Wetlands ecology, conservation

Observations of the wastewater depuration capacity of natural wetlands have led to a greater understanding of the potential of these ecosystems for pollutant assimilation and have stimul

W ETLANDS : E COLOGY ,

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L IBRARY OF C ONGRESS C ATALOGING - IN -P UBLICATION D ATA

Wetlands : ecology, conservation, and restoration / Raymundo E Russo (editor)

C ONTENTS

Expert Commentary

Two Alternative Modes for Diffuse Pollution Control by Wetlands 1

Chen Qingfeng, Shan Baoqing and Ma Junjian

Short Communication

Multiangular Imaging of Wetlands in New England 7

Lesley-Ann L Dupigny-Giroux and Eden Furtak-Cole

Research and Review Articles

Ana Dordio, A J Palace Carvalho and Ana Paula Pinto

Chapter 2 Remote Sensing Data for Regional Wetland Mapping in the

United States: Trends and Future Prospects 73

Megan W Lang and Greg W McCarty

Chapter 3 Transforming Useless Swamps into Valuable Wetlands:

Evaluating America’s Policy, 1970-2008 113

Andrea K.Gerlak and Jeanne N Clarke

Chapter 4 Dynamics of Coastal Wetlands and Land Use Changes in the

Watershed: Implications for the Biodiversity 133

Miguel Ángel Esteve, M Francisca Carreño, Francisco Robledano, Julia Martínez-Fernández and Jesús Miñano

Kela P Weber and Raymond L Legge

Chapter 6 The Role of Harvest and Plant Decomposition in

Constructed Wetlands 213

Juan A Álvarez and Eloy Bécares

Chapter 7 Nutrition and Toxicity of Inorganic Substances from Wastewater in

Constructed Wetlands 247

Zhenhua Zhang, Zed Rengel and Kathy Meney

Chapter 8 A Conceptual and Methodological Framework for the Study of

Vegetated Fluvial Landscape Evolutionary Trajectories 271

Dov Corenblit, Johannes Steiger, Eric Tabacchi and Angela M Gurnell

Chapter 9 Macrophyte Morphological Response to the Industrial Effluent

Toxicity in a Constructed Wetland 295

H R Hadad, M M Mufarrege, M Pinciroli, G Di Luca,

V del Sastre and M A Maine

Chapter 10 Phytoremediation Processes for Water and Air Pollution Control

in the Aspects of Nutrient and Carbon Dioxide Removals 325

Jae Seong Rhee, Yonghui Song, Fasheng Li and Janjit Iamchaturapatr

Chapter 11 Phytoplankton Biomass Regulation in Contrasting Environmental

States of Temporary Pools 359

Silvia Martín, Marta Rodríguez and David G Angeler

Chapter 12 Can Tern Migrants Coexist with Urban Development and

Estuarine Recreational Activities? 373

Ken Chan, Jill Dening and Marja-Leena Malinen

P REFACE

Wetlands are lands where saturation with water is the dominant factor determining the nature of soil development and the types of plant and animal communities living in the soil and on its surface Wetlands vary widely because of regional and local differences in soils, topography, climate, hydrology, water chemistry, vegetation, and other factors, including human disturbance Indeed, wetlands are found from the tundra to the tropics and on every continent except Antarctica This new book brings together the latest research in the field Short Communication - Multiple view angles (MVA) or multiangular imaging represents

a yet to be explored use of the remote sensing of wetlands The ability to view the landscape off-nadir (traditionally the surface is viewed at right angles) allows for the quantification of moisture stress, species separation and the proportion of vegetation to standing water in these ecosystems This commentary will focus on the ratio of two broadband wavelengths (near-infrared to blue) derived from multiangular images acquired by the Airborne Multi-angle Imaging SpectroRadiometer (AirMISR) of wetlands across New England The resulting insights into the photointerpretation, monitoring and mapping of wetlands will be highlighted Chapter 1 - Human societies have indirectly used natural wetlands as wastewater discharge sites for many centuries Observations of the wastewater depuration capacity of natural wetlands have led to a greater understanding of the potential of these ecosystems for pollutant assimilation and have stimulated the development of artificial wetlands systems for treatment of wastewaters from a variety of sources Constructed wetlands, in contrast to natural wetlands, are human-made systems that are designed, built and operated to emulate wetlands or functions of natural wetlands for human desires or needs Constructed wetlands have recently received considerable attention as low cost, efficient means to clean-up not only municipal wastewaters but also point and non-point wastewaters, such as acid mine drainage, agricultural effluents, landfill leachates, petrochemicals, as well as industrial effluents Currently, untreated wastewater discharge in the natural wetlands sites is becoming an increasingly abandoned practice whereas the use of constructed wetlands for treatment of wastewater is an emerging technology worldwide However, natural wetlands still play an important role in the improvement of water quality as they act as buffer zones surrounding water bodies and as a polishing stage for the effluents from conventional municipal wastewater treatment plants, before they reach the receiving water streams In fact, one of the emerging issues in environmental science has been the inefficiency of wastewater treatment plants to remove several xenobiotic organic compounds such as pesticides and pharmaceutical residues and consequent contamination of the receiving water bodies Recent

studies have shown that wetlands systems were able to efficiently remove many of these compounds, thus reaffirming the importance of the role which can be played by wetlands in water quality preservation

The aim of this work is to present a review on the application of wetlands as “living filters” for water purification Emphasis was focused on the removal of micropollutants, especially xenobiotic organic compounds such as pharmaceuticals residues, which are not efficiently removed by conventional municipal wastewater treatment plants Furthermore, the role of wetlands as protection zones which contribute to the improvement of the aquatic ecosystems’ quality will be discussed

Chapter 2 - Historically, the biologic, aesthetic, and economic values of wetlands were largely unappreciated Wetlands within the United States have been and are continuing to disappear rapidly Efforts are being made to conserve remaining wetlands and many regulatory policies have been adopted in support of this goal To regulate the loss, preservation, and/or restoration of wetlands and to judge the effectiveness of these regulatory efforts in preserving associated ecosystem services, wetlands must be routinely monitored Wetland mapping is an essential part of this monitoring program and much effort has been made by the US state and federal governments, as well as other organizations, to provide quality wetland map products Wetland maps can serve a variety of purposes including regulation and natural resource management They can also be used to parameterize models that quantify water quality and quantity, as well as the provision of wetland ecosystem services, at the watershed scale Wetland hydrology is the most important abiotic factor controlling ecosystem function and extent, and it should therefore be a vital part of any wetland mapping or monitoring program New approaches are needed to not only map wetlands, but also to monitor wetland hydrology as it varies in response to weather, vegetation phenology, surrounding landuse change, and other anthropogenic forces including climate change Recently developed remote sensing technologies and techniques have the potential to improve the detail and reliability of wetland maps and the ability to monitor important parameters such as hydrology Various types of remotely sensed data (e.g., aerial photographs, multispectral, hyperspectral, passive microwave, radar, and lidar) have different capabilities with specific advantages and disadvantages for wetland mapping at the regional scale Although aerial photographs were traditionally used to map wetlands and infer hydrology, fine-resolution optical images are now available more frequently as commercial agencies increase satellite coverage (e.g., Quickbird and IKONOS) However, optical data, such as aerial photographs and multispectral satellite images have limitations, including their inability to detect hydrology below dense vegetative canopies and their limited ability to detect variations in hydrology (i.e., inundation and soil moisture) The restrictions of optical data are increasingly being compensated for with the use of new technologies, including synthetic aperture radar, lidar, and geospatial modeling The availability of these new data sources is increasing rapidly For example, many states in the US are now collecting synoptic state-wide coverages of lidar data The sources, strengths, and limitations of different types of remotely sensed data are reviewed in this chapter, as well as the importance of temporal and spatial resolution necessary for regional scale wetland mapping efforts The potential of multi-temporal, multi-sensor approaches that capitalize on geospatial modeling are emphasized for meeting current wetland mapping challenges

Chapter 3 - This paper traces the evolution of America’s wetland policy beginning with passage of the Clean Water Act (CWA) of 1972 This law, for the first time, established a

federal program to protect wetlands, dramatically elevating the value of these ecosystems However, despite attitudinal changes and new governmental programs, the nation continues

to lose its potentially valuable wetlands albeit at a slower rate than was the case in the 1970s and prior to the passage of the CWA This chapter offers an objective evaluation of the federal wetlands protection policy The authors place this evaluation within a broad societal context, showing that since 1970 there have occurred sweeping demographic, economic, and political changes that clearly have impacted the extent of wetlands in the United States They argue that Section 404 has failed to reverse the net loss of wetlands in the U.S Moreover, it has evolved into a policy lightening rod within the water resources arena and been a major factor in Congress’ failure to revise and reauthorize the Clean Water Act Finally, the authors offer some recommendations designed to improve the policy, arguing for heightened wetlands protection through partnerships and acquisitions

Chapter 4 - The Mediterranean coastal landscapes have suffered significant changes along the last decades due to the agricultural intensification and tourist development Such changes have modified the water flows and specifically the hydrological regime of wetlands,

as has occurred in the Mar Menor (Southeast Spain) The Mar Menor coastal lagoon and associated wetlands present noticeable ecological and biodiversity values However, the land-use changes in the watershed and the consequent changes in the water and nutrient flows along the period 1980-2005 are threatening the conservation of these wetlands A dynamic model has been developed to simulate the key environmental and socio-economic factors driving the export of nutrients to the Mar Menor lagoon and associated wetlands, where some eutrophication processes have appeared

In this chapter the changes in the vegetal and faunistic assemblages are analysed Vegetal communities are studied by means of remote sensing techniques, which have provided information about the changes in area and habitat composition of the wetlands along the considered period This has shown that the habitats more negatively affected by the hydrological changes are those most threatened in the international context and with a highest interest from the point of view of biodiversity conservation It has also been possible to verify the direct relationships between all these changes at wetlands scale and the agricultural changes at the watershed scale

Two faunistic communities especially sensitive to these ecosystemic changes have also been studied: i) Wandering beetles and ii) Birds (waterbirds and steppe passerines) Wandering beetles (Coleoptera) were studied with pitfall traps in 1984, 1992 and 2003 and steppe passeriforms with line transects in several years along the period In both communities evident changes have been observed Regarding beetles, the most halophilous species have been favoured, some of them especially relevant due to its rarity in the European context The ratio Carabidae/Tenebrionidae has shown to be a good indicator of the hydrological changes

of the wetlands Waterbirds have shown dramatic changes in their relative abundances within the lagoon, with a long-term decline in the most characteristic original species, increases in generalist piscivores and a recent appearance and rapid growth of the herbivores guild In the case of steppe passeriforms, this community has been negatively affected, especially some

species like Melanocorypha calandra The family Alaudidae has lost importance to the benefit of the families Turdidae and Fringillidae These changes can be considered a loss of

value in relation with the original passeriform community, since the wetland qualifies as a Specially Protected Area under the EU’s Bird Directive, precisely on the basis of its genuine steppe bird assemblage

In conclusion, the changes at wetlands scale clearly reflect the hydrological modifications

at the watershed scale and have significant effects on the most characteristic biodiversity of the wetlands of coastal arid systems

Chapter 5 - Conventional secondary and tertiary wastewater treatment methods include activated sludge, trickling filters, slow sand filtration, chlorination, ozonation and UV radiation Chlorination being the most widely used pathogen disinfection method is presently under scrutiny as chlorination can produce carcinogenic trihalomethanes when natural organic matter is present in the wastewater Constructed wetlands (CWs) have proven to be an effective treatment alternative for the removal and inactivation of pathogens in wastewaters Constructed wetlands have low principle and operating costs and are fairly simple to design and implement, making them an attractive wastewater treatment alternative when compared

to conventional secondary or tertiary treatment processes Constructed wetlands designed for pathogen treatment are most often preceded by filtration or sedimentation Pathogen removal efficiencies upwards of 99.99% have been reported by multiple authors employing many different constructed wetland designs Constructed wetland design tends to be based largely

on rule of thumb sizing, as the specific mechanisms and fundamental variables involved in pathogen removal are only vaguely understood Suggested mechanisms of pathogen treatment

in CWs include but are not restricted to sedimentation, natural die-off, temperature, oxidation, predation, unfavourable water chemistry, biofilm interaction, mechanical filtration, exposure

to biocides and UV radiation Pathogen removal has been shown to correlate well with hydraulic retention time Use of first order decay kinetics is the preferred method to describe and predict pathogen removal in CWs A severe lack of attention has been given to the comparative quantification of the specific mechanisms contributing to pathogen treatment in constructed wetlands Small-scale controllable constructed wetland systems are identified as systems which can be used in conducting well-designed controlled experiments where fundamental mechanisms and variables involved in pathogen removal can be comparatively quantified It is proposed that if the fundamental mechanisms and variables affecting pathogen removal in constructed wetlands are better understood and quantified the large performance variations reported for similarly designed treatment wetland systems can be better explained, engineered and controlled

Chapter 6 - Upon decomposition, at the end of the summer and during the autumn, wetland vegetation releases organic carbon into the wetland system A part of this organic matter remains in the wetland, and is degraded at different rates during the rest of the year Therefore, litter decomposition has important consequences on constructed wetlands because

it is related to the autochthonous production of organic matter, clogging rates in surface-flow wetlands, and terrestrialization in free-water surface wetlands

The effect of harvest was studied in two free-water surface-flow wetlands Both wetlands

were planted with Typha latifolia with one of the wetlands harvested On the other hand, decomposition rates of Typha latifolia were quantified during both winter and summer in the

non-harvested surface constructed wetland using the litter bag technique Nutrient concentrations were always lower in the effluent of the harvested wetland, indicating nitrogen and phosphorus release by decomposition of vegetation, in the non-harvested system In addition, harvesting reduced the effluent TSS and BOD concentrations by 37.3% and 49.2%,

respectively, when compared to the non-harvested wetland in spring Seasonal background

concentrations (C*) in the wetlands, increased from winter to spring and decreased again in

summer Organic load and nutrients produced per gram of Typha were evaluated by using

in-situ Typha degradation experiments Taking into account the experiments of litter bag

technique, no significant differences were found in both variables among the different mesh sizes, with the exception of the control bags in winter Meso or macrofauna did not play any role in plant decomposition Decomposition rates were significantly different between winter and summer when considering each mesh size separately Decomposition rates from adjusted exponential models ranged from 0.0014 to 0.0026 d-1 in winter (5ºC), and from 0.0043 to 0.0052 d-1 in summer (20ºC) Typha decomposition rates were compared with others

macrophytes From these decomposition rates, it is estimated that 31% of the initial mass of plant detritus would remain in the system after one year Based on the research conducted during several experiments, harvesting can be recommended as an operational and management strategy in warm climates and diluted wastewater conditions

Chapter 7 - The use of constructed wetlands for purification of wastewater has received increasing attention around the world A variety of wetland plant species (including ornamental ones) as either a monoculture or species mixes are used in constructed wetlands Plants play an extremely important role in removing pollutants from wastewater Although there is considerable information on plant productivity, biomass and nutrient dynamics in natural and fertilized wetlands, most studies on constructed wetlands for treatment of wastewaters have only addressed general aspects of plant growth and nutrient accumulation Nutrition and toxicity of inorganic substances such as nitrogen, sulphur, salts and metals in wastewater on wetland plants has not been fully investigated and their interactive effects and environmental cycling in constructed wetlands remain poorly understood

Nitrogen nutrition is the most important factor influencing plant performance in constructed wetlands, but higher NH4-N may become toxic to wetland plants Sulphur is an essential nutrient for plant growth, but under waterlogged conditions sulphate is reduced to hydrogen sulphide that is highly toxic to wetland plants Many metals in wastewater are essential micronutrients for wetland plants, but become toxic if their concentration exceeds a specific critical point A proper amount of salts is essential for plant growth, but high concentrations of salts, particularly sodium chloride in wastewater have harmful effects on plant growth

Wetland plant species have differential capacity to take up nutrients, different preference for nitrogen forms and have evolved various adaptive mechanisms protecting them against toxicity of inorganic substances Given that plants are an integral part of constructed wetlands, the selection of suitable species, improvement of cultivations and determination of factors affecting growth are needed to produce healthy and effective wetland ecosystems Understanding biogeochemical cycling in wetlands as well as nutrition and toxicity of inorganic substances from wastewater on plant development and function may help reduce performance variability and enhance pollutant removal in constructed wetlands

Chapter 8 - This chapter presents a conceptual and methodological framework to study temporal and spatial changes of fluvial landforms and associated plant communities and to identify the underlying causes of either progressive or sudden changes Mutual interactions and feedbacks between hydrogeomorphic processes, fluvial landforms and vegetation dynamics are considered within this framework, leading to the analysis of biogeomorphic (i.e., landforms and associated vegetation communities) evolution trajectories within the fluvial corridor and to the evaluation of their consequences for ecological and geomorphic forms and processes

First, fundamental aspects linked to the conceptual model of Fluvial Biogeomorphic Succession (FBS model) proposed by the authors (cf Corenblit et al 2007) are presented This model describes the most dominant biogeomorphic succession trajectory of temperate rivers under current bioclimatic and anthropogenic conditions, starting from the rejuvenated state (bare sediment within the channel after a destructive flood) This dynamic model involves a characteristic sequence of four biogeomorphic phases where interactions of hydrogeomorphic processes and vegetation dynamics are either strong or weak according to different spatiotemporal configurations The characteristic evolutionary trajectory corresponds to a progressive shift from the dominance of allogenic (hydrogeomorphic) processes to the dominance of autogenic (ecological) processes It is marked by a development of specific stabilised vegetated landforms such as banks, islands and floodplains In particular, the cyclic dynamics of the biogeomorphic succession (i.e., frequency and magnitude of rejuvenation and maturation processes), incorporating critical thresholds are discussed

Second, a conceptual tool for the description and analysis of potential fluvial landscape evolutionary trajectories is proposed This conceptual tool is a discrete three dimensional biogeomorphic phase-space composed of five key-stages of vegetation development (bare sediment; seedlings and saplings; adult herbs; adult shrubs; adult trees) within four distinct zones of the river corridor, exposed to four distinct levels of hydrogeomorphic disturbance (permanent submerged area; high flood-frequency area; low flood-frequency floodplain; non-submersible area) The four main processes controlling shifts between biogeomorphic configurations within the phase-space are related to the critical role of pioneer vegetation within fluvial landscape dynamics

Finally, a methodological basis to test and to refine the model using a probabilistic transition analysis combining the biogeomorphic phase-space, empirical field data, GIS and remote sensing at local and regional scales is proposed and its applications for river management are discussed

Chapter 9 – This chapter describes the morphological variations of floating and rooted macrophytes growing in a wetland constructed for the treatment of industrial wastewater and

in natural wetlands of the Middle Paraná River floodplain, Argentina Cross-sectional areas (CSA) of the root, stele and of metaxylem vessels and the total metaxylem CSA were measured In addition, parameters such as dry biomass, chlorophyll concentration, and metal (Cr, Ni and Zn) and nutrient (P) concentrations were compared During the first months of operation of the constructed wetland, only sewage was poured and floating macrophytes were

dominant After five years of operation, Typha domingensis was the dominant species in the

constructed wetland In this species, biomass and height of the plants at the inlet and outlet were significantly higher than in the natural wetlands The plants growing at the inlet showed root and stele CSA values significantly higher than those for the plants growing at the outlet and in natural wetlands The total metaxylem vessels CSA of the inlet plants were significantly higher than those obtained in the outlet and natural wetlands owing to the plants

of this site showed the highest number of metaxylem vessels In order to determine the morphological changes as an adaptive response to the contaminants present in the effluent,

greenhouse experiments were carried out with P stratiotes and E crassipes In P stratiotes,

Ni and Cr+Ni+Zn treatments were the most toxic ones, in which biomass, chlorophyll and the

internal morphological parameters of roots decreased significantly, while in E crassipes Ni

caused toxic effects in the internal as well as the external morphology The modifications

recorded account for the adaptability of T domingensis to the conditions prevailing in the

constructed wetland, which allowed it to become the dominant species This chapter may contribute to the design and mainteinance of constructed wetlands that include the macrophytes studied

Chapter 10 - The growth of industries and major agricultural enterprises (especially food industries) supplying the human demands for their increasing population causes an annihilation of water ecosystems and an augmentation of water pollutions These are the main sources of nutrient supplements in water resources Excess nutrients led to the eutrophication phenomena and in many cases the deterioration of public health While the role of carbon dioxide (CO2) gas in global climate change has become well-known, which is one of the most important environmental issues of our day, therefore it is necessary to develop technologies for the minimization of CO2 discharging into the atmosphere Although CO2 occurs naturally

in the atmosphere, its current atmospheric concentrations have been greatly affected by human activities

One ecological method used for treating polluted water containing high nutrients and encouraging CO2 sequestration is treatment wetlands, where various aquatic plants are used for purifying the water and wastewater from excess nutrients and also withdrawing the anthropogenic CO2 from polluted atmosphere into plant’s biomass by photosynthesis process Although wetland area around the world has diminished and continues to lose due to economic development, agriculture, and other landscape alterations, recently many of these losses are compensated by construction of new wetlands due to an our increasing understanding of wetland functions and values on global environment

Chapter 11 - Although abiotic forces play a fundamental role in community and process regulation of disturbed wetland ecosystems, biotic interaction is increasingly recognised for having important regulatory feedback effects This chapter reports on the context-specific role

of biotic and abiotic regulation of phytoplankton biomass in temporary ponds Contamination

of artificial ponds with different application concentrations of a fire retardant resulted in alterations of the trophic status, primary producer and zooplankton communities in treatment ponds Principal component analyses suggested that facilitation of phytoplankton biomass through cladocerans was the most important controlling factor in nutrient-limited control ponds These biotic interaction effects disappeared in retardant treatment ponds where phytoplankton biomass was almost exclusively controlled by water depth fluctuation This context-specific, eutrophication-mediated physical control of algal biomass in treatment ponds adds a new dimension to the traditional perspective of resource and consumer control

of phytoplankton in alternative ecosystem states in lakes The context-dependent interplay of physical and biotic processes in wetlands will likely influence applied issues and challenge wetland management and restoration

Chapter 12 - Urbanisation and recreational activities are two of the major causes of population declines of species, and throughout the world they continue to spread and intensify

at a rapid rate The two are often linked—an increase in recreational activities is often associated with nearby growth in residential development and vice versa Developmental growth is greatest in places of high tourism value, such as in coastal areas with sandy shores Sandy coasts are popular with beach walking and jogging, swimming, off-road vehicles, boating, ecotourism, and other outdoor activities The most concentrated activities are in estuaries with sandbanks and intertidal flats that are protected from the open ocean Yet the same estuaries are often sensitive ecosystems, commonly frequented by a variety of resident

and migrant birds that use the areas to breed, forage, or roost Increasing incidents of human disturbance can affect breeding behavior, feeding patterns, opportunities for rest, and decline

in estuarine bird abundance The direct impact on reproduction in breeding birds is obvious, but survival of migratory species is also affected through ineffective build-up of requisite fat reserves to successfully undertake their migratory journey For both resident and migrant birds, disturbance could result in reduced feeding time, lowering the necessary fat reserves for survival

Chapter 13 - Increased agricultural production, land drainage and resultant land use changes have increased loads of non-point source pollutants being discharged into aquatic ecosystems Estimates suggest that non-point source pollution (NPS) contributes over 65% of the total pollution load to inland surface waters, including 332,000 km of rivers, 215,000 ha

of lakes and 1.5 x 106 ha of estuaries There are two types of agricultural wetlands that could mitigate NPS pollution: constructed wetlands and surface drainage ditches Constructed wetlands are commonly used to mitigate increased nutrient, biological oxygen demand, and pesticide loads prior to entering receiving waters However, some farmers will forgo the practice of constructing a wetland for routing water because of associated costs of construction, maintenance and loss of land in agricultural production Agricultural drainage ditches are management tools put in place by farmers to rapidly remove standing water from their farmland Drainage ditch function is simply one of drainage; however, research has shown that surface vegetated drainage ditches are primary intercept wetlands characterized by

an ephemerally inundated hydroperiod, developed hydro-soils and a suite of facultative hydrophytes Studies in the mid-South US have shown vegetated surface drainage ditches to reduce both pesticide and nutrients loads within the ditch prior to effluent reaching receiving waters This is increasingly important in today’s landscape where fertilizer and pesticide applications are still high Pollutant reduction capacity within ditches may be improved with temporal and spatial manipulation of water residence at critical junctions of non-point pollutant loss throughout the year Primary interception, transformation and mitigation of agricultural pollutants has far reaching consequences for aquatic ecosystem health, downstream eutrophication, and coastal dynamics such as hypoxia, commercial fisheries and economic development

Chapter 14 - Over 3 million wetlands populate the U.S portion of the Prairie Pothole Region (PPR), where conservation goals include restoration and preservation of the cover cycle The cover cycle is characterized by seasonal and annual changes in vegetation and open water and is closely coupled to climate and natural ecosystem functions A complete cover cycle include periods of time when high waters drown hydric vegetation during deluge and periods where hydric vegetation expands as waters dry-down during drought Changes in wetland cover may occur on weekly, monthly, or annual time-scales These dynamics contribute to a rich diversity of habitats that support more waterfowl than any other region in North America In addition temporal dynamics, PPR wetlands rarely function as single entities because of shared surface and/or groundwater hydrology This spatial interdependence requires PPR wetland functional assessments represent populations of wetlands, commonly referred to as “profiles.” Synoptic data profiling cover cycle stage and return time for populations of wetlands would scaffold large-scale investigations of ecosystems services, habitat status, and sensitivity to climate change

This chapter describes application of previously developed tools for synoptic delineation

of wetland water and hydric vegetation cover to classify cover cycle for thousands of wetland

basins within a single satellite image (10,000-30,000 km2 of land area) Using satellite data layers in geographic information systems (GIS), wetland profiles developed using current (2007) wetland cover data are compared with profiles developed using National Wetland Inventory (NWI) data from 1980 Results underscore the dynamic nature of these ecosystems and the need for current observations when setting conservation goals, monitoring restoration effectiveness, and evaluating anthropogenic impacts

Expert Commentary

T WO A LTERNATIVE M ODES FOR D IFFUSE

Chen Qingfeng∗1, Shan Baoqing2 and Ma Junjian1

1Shandong Analysis and Test Center, Jinan, 250014, China

2Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences,

There are many ecological engineering techniques, such as buffer zones, ponds, wetlands and riparian zones currently in use, and wetlands have been shown to be effective in removing pollutants from runoff water (Mitsch et al., 2002) In order to improve treatment efficiency, wetlands can be used as treatment trains According to the flow route, the control chains can be designed in on-line and off-line treatment trains (Bardin et al., 2001; Michael and John, 2003; Shan et al., 2006; Paolo et al., 2006; Chen et al., 2007) For the on-line treatment train, all of the runoff from a storm routes through all the system structures, which are distributed on the runoff route The treatment train may have lower pollutant removal efficiency than off-line treatment train if the system storage is not large enough to hold all the runoff from a significant storm event For the off-line treatment train, the system structures are distributed away from the runoff route The treatment train is designed to intercept the

“first flush”, which has much higher concentration of pollutants in the initial runoff The later runoff, with lower concentration of pollutants, overflows the catchment directly The off-line treatment train requires less land area and it is an economical and effective measure for the control of runoff pollution in urban areas Every mode plays an important role in stabilizing the adjacent ecosystems and reducing the load of runoff pollution

∗ Email:chensdcn@163.com

In the process of diffuse pollution control, the selection of the mode is the key step The selection of the two alternative modes for diffuse pollution control is based on concern with native topography, climate, storm water volume and available land area of the catchment (Figure 1)

Figure 1 The flow chart of the two alternative modes selection for diffuse pollution control

If there is enough available land area in the catchment, then both modes can be selected Otherwise, the offline mode may be the only choice for diffuse pollution control Furthermore, the online mode may be the better choice if reuse of rainwater, additional biologic habitat, and aesthetics value are taken into consideration In other conditions, the offline mode may be an effective choice for diffuse pollution control In every mode, many ecological engineering techniques can be included However, the application of the two modes in urban zoos has received little research attention

A detailed study was carried out from April 2003 to August 2005 in Wuhan City Zoo, which is surrounded by Moshui Lake In this study, two catchments were selected to study the characteristics and performances of the online and offline modes in Wuhan City Zoo For this purpose, an online pond-wetlands system in the Orangutan House Catchment, and an offline filtering ditch-pond system in the Canine House Catchment, were designed to control the small point and diffuse sources of pollution in the urban zoo

In the Orangutan House Catchment, an online pond wetlands system was used to control pollution from small point and diffuse sources All the engineering constructions were built to adjust the flow rate of storm water and the kinetic energy of runoff on the runoff route From upland to downstream, the landscape structures included upland grassland, orangutan house, sediment tank (ST), pond (P), the first wetland (W1) and the second wetland (W2) For the huge storage capacity of the pond-wetlands system (1071m3), most of runoff was able to be stored temporarily and purified by physical, chemical and biologic processes in the wetlands

The online mode flow of the catchment is shown in Figure 2 Through grids, S2 was initially stored in ST on dry days During rainfall events, all runoff, coming from S1 and S3, as well

as S2, flowed through ST, P, W1 and W2 sequentially and then drained into Moshui Lake In order to save water, the rainwater, stored in the pond-wetlands system, can be reused for flushing the animal house and irrigating the grassland

Figure 2 Online mode for diffuse pollution control in the Orangutan House Catchment

Without enough available land area for water treatment constructions, an offline filtering ditch-pond system was designed to control diffuse pollution in the Canine House Catchment The off-line treatment train was composed of some pretreatment equipments and a filtering ditch–pond system The pretreatment equipments include a transport ditch, grids and a sediment tank The filtering ditch–pond system consists of a filtering ditch and two ponds This system has a storage capacity of 115m3 and can store the initial 13.7mm runoff depths in

a storm Four species of hydrophytes, including Phragmites communis Trirn., Acorus calamus Linn., Alternanthera philoxeroides and Canna generalis, were planted in the ponds

The landscape structures in the catchment include upland grassland, storm transport ditch (T), Canine House, filtering ditch (FD) and ponds (P) from upland to downstream FD was underground and rebuilt by an old flue, is 83 m in length, 0.5 m in width, and 1.2 min depth

It has three sections: sediment zone, filtration zone and storage zone There are 9 subsections

in the filtration zone and each subsection is filled with one of the following media: gravel, aluminite stone, bulky sand, cobblestone, ceramic granule, silver sand, turf, steel slag and vermiculite

All the ecological engineering constructions were finished in April 2004 According to the pollution characteristics, topography, available land area and climate in the catchment, the off-line treatment train was designed to separate the ‘first flush’ from the runoff The sketch map of the off-line treatment train is shown in Figure 3 Because the main type of land use is upland (61.4%) in the catchment, the off-line treatment train works in a natural process and requires no power Through the grids, wastewater from flushing the animal houses (S2) was initially stored in the sediment tank (ST) and overflowed to filtering ditch–pond system for decontamination on dry days

During rainy days, the initial runoff, coming from upland runoff (S1) and roof runoff (S3), as well as wastewater (S2), was diverted to the filtering ditch (FD) for filtration and adsorption After that, the runoff water overflowed into ponds for further decontamination

and then, in the final stage, drained into Lake Moshui The later runoff, with lower concentration of pollutants, was discharged into the lake directly

Figure 3 Offline mode for diffuse pollution control in Canine House Catchment

The results showed that the two modes both improved runoff water quality and had high retention rates for water and pollutants In the outflows, the event mean concentrations (EMCs) of total suspended solids (TSS), chemical oxygen demand (COD), total nitrogen (TN) and total phosphorus (TP) were reduced by 88%, 59%, 46% and 71% for the online mode, and those were 75%, 50%, 50% and 74% for the offline mode The annual retention rates of pollutant loads for the online mode were 94.9%–98.5% in the three study years; those for the offline mode were 70.5%–86.4% Based on calculation, the online mode was able to store the runoff of 66.7 mm rainfall completely, and the offline mode could store that of 31.3

mm rainfall In addition, the online mode can provide an effective way for rainwater utilization and good habitats for aquatic wildlives, and has an excellent aesthetics value for recreationsal pastimes The offline mode can save land resources and may be an effective and economical measure for diffuse pollution control in urban areas

Bardin, JP, Barraud, S, Chocat, B, 2001 Uncertainty in measuring the event pollutant

removal performance of on-line detention tanks with permanent outflow Urban Water 3,

91–106

Chen QF, Shan BQ, Yin CQ, Hu CX An off-line Filtering Ditch-pond system for Diffuse

Pollution Control at Wuhan City Zoo Ecological Engineering, 2007, 30(4):373-380

Chen QF, Shan BQ, Yin CQ, Hu CX Two Alternative Modes of Diffuse Pollution Control in

an Urban Tourist Area Journal of Environment Science, 2007, 19(10):1067-1073

Deletic, A, 1998 The first flush load of urban surface runoff Water Res 32 (8), 2462–2470 Lazzarotto, P, Prasuhn, V, Butscher, E., Crespi, C., Flu¨ hler, H., Stamm, C., 2005

Phosphorus export dynamics from two Swiss grassland catchments J Hydrol 304, 139–

150

Michael Jr., John, H., 2003 Nutrients in salmon hatchery wastewater and its removal through

the use of a wetland constructed to treat off-line setting pond effluent Aquaculture 226,

213–225

Mitsch, WJ, Lefeuvre, JC, Bouchard, VB, 2002 Ecological engineering—applied to river and

wetland restoration Ecol Eng 10, 119–130

Novotny, V, 1999 Integrating diffuse pollution control and water body restoration into

watershed management J Am Water Resour Assoc 35 (4), 717–727

Paolo, SC, Gaspare, V, 2006 Simulation of the operation of detention tanks Water Res 40

Short Communication

N EW E NGLAND

Lesley-Ann L Dupigny-Giroux∗ and Eden Furtak-Cole

University of Vermont, Department of Geography

200 Old Mill Building, Burlington, VT 05405-0114, 802-656-2156

Multiple view angles (MVA) or multiangular imaging represents a yet to be explored use of the remote sensing of wetlands The ability to view the landscape off-nadir (traditionally the surface is viewed at right angles) allows for the quantification of moisture stress, species separation and the proportion of vegetation to standing water in these ecosystems This commentary will focus on the ratio of two broadband wavelengths (near-infrared to blue) derived from multiangular images acquired by the Airborne Multi-angle Imaging SpectroRadiometer (AirMISR) of wetlands across New England The resulting insights into the photointerpretation, monitoring and mapping of wetlands will

be highlighted

Multiple view angles (MVA) or multiangular imaging of terrestrial ecosystems has been shown to provide multispectral data not observed from the nadir or other single view angles only, due to the highly anisotropic reflectance of vegetation (Asner et al., 1998) Vegetation parameters may not be the most sensitive to the nadir view angle (Privette, 1995) Other studies have explored the relationship between a sensor’s field of view and vegetation structure (Widlowski et al., 2004; see Diner et al., 2005 for a full description of these studies), land cover classifications (Hyman and Barnsley, 1997) and the role of sub-pixel heterogeneity (Zhang et al (2002a, b), as well as view angle and reflectance anisostropy at the red wavelengths (Pinty et al., 2002)

∗ E-mail: ldupigny@uvm.edu

In a recent study (Dupigny-Giroux, 2007), multiangular images from the Airborne angle Imaging SpectroRadiometer (AirMISR) of the Howland Forest in Maine, were used for land use/land cover (LULC) separability under varying moisture conditions in the humid, continental environment of central Maine The study extended original work by Dupigny-Giroux and Lewis (1999) that used the ratio of near-infrared/blue wavelengths plotted against surface temperatures to describe vegetation and moisture stress for the semiarid Brazilian nordeste (northeast) This study complements work by Silva Xavier and Soares Galvão (2005) who used Principal Components Analysis of Multi-angle Imaging SpectroRadiometer (MISR) data from the Amazon to discriminate land cover types

Multi-Results of the Dupigny-Giroux (2007) indicated that the NIR/blue ratio at multiple view angles was able to discriminate variations among wetland, aquatic vegetation and the extent

of moisture stress Contributions of the study included an expansion of the recommended combination of the 15-30˚ solar illumination angle and nadir viewing angle for optimally recording benthic features (Dobson et al., 1995); a sensitivity of the NIR/blue ratio to species type and vigour, water/vegetation proportions and moisture gradients across emergent wetlands; and the distinction between aquatic macrophytes and terrestrial vegetation that are often similar individual wavelengths (Valta-Hulkkonen et al., 2003) The study suggested potential uses of the multi-angular ratio including improved mapping of wetlands in humid temperate regions (Bicheron et al., 1997; Barnsley et al., 1997); the avoidance of false change detection due to drought or water draw down (U.S Fish and Wildlife Service, 2004) and; the improved photointerpretation of evergreen forested wetlands and more xeric ecosystems (Tiner, 2003)

In this commentary, the methodology of the Dupigny-Giroux (2007) study was applied to wetlands at two other experimental forests in New England to explore the applicability of the technique across disparate wetland types and microclimates

The data used in this commentary were collected over three experimental forests in New England in August 2003 (Figure 1) The Bartlett Experimental Forest in north-central New Hampshire and the Harvard Forest in western Maine were both flown on 24 August, with data acquisition over Howland Forest in central Maine on 28 August All three sites are well instrumented with standard meteorological equipment, biomass and carbon sequestration

measurements to support long term experiments including NASA’s Forest Ecosystem Dynamics Project

Howland Forest Bartlett Forest Harvard Forest

Figure 1 Locations of the three experimental forests in New England

Only the data from the north-south runs and A-C cameras over each site were used due to data inhomogeneities Georectified radiance product (L1B2) data were resampled to a 27.5m grid in the UTM (Universal Transverse Mercator) projection and available online from the Langely Distributed Active Archive Center (DAAC) Actual radiances were computed using the AirMISR tool An IR minimum check was performed for each viewing angle Ancillary digital data were acquired from the National Wetlands Inventory, Maine GIS, New Hampshire GIS and Massachusetts GIS

2.2 Wetlands of the Study Sites

The wetlands observed at the three study sites varied by extent, species composition, tidal regimes and permanence of water The Howland Forest site decreases in elevation from over 120m in the north to about 19m in the south, with palustrine, estuarine, evergreen as well as broad-leaf deciduous and persistent emergent wetlands To the west, the Bartlett Experimental Forest site located in the White Mountains National Forest ranges in elevation from 59m to 1868 m, an upland area characterized by broadleaf deciduous forests with predominantly palustrine forested broad-leaf deciduous and needle-leaf evergreen wetlands The Harvard Forest site was lower in elevation (9-548m) and characterized by both palustrine evergreen and freshwater forested shrub wetlands

3 RESULTS AND APPLICABILITY OF MVA TO

The relationship between wetlands and view angles can be analyzed by scatterplots (not shown) of camera pairs on which the 45˚ and best fit lines have been plotted For the three experimental forests, there was a high degree of correlation between the high camera view angles (An, Af, Aa and Bf) The straight line relationship denotes a moisture gradient from mesic regions (low ratios) to xeric ones (high ones) The relationship is most extensive (with points at both ends of the 1:1 line) for the palustrine, estuarine wetlands of the Howland forest and less so for the other two regions Differences in species composition and tidal flow regimes were marked across the three forests, influencing the view angles that were most useful for wetland discrimination For example, at the Howland Forest wetlands, the scatterplot of the Af and Bf forward viewing angles (R2=0.904) was particularly well suited to highlighting moisture stress across forested wetlands, stress that was not observable at nadir (Dupigny-Giroux, 2007) This may be due to the fact that these seasonally flooded wetlands tend to be wetter for shorter durations during the growing season (Tiner, 2003) At the Harvard Forest, both the scatterplots of the high forward view angles (Af and Bf) as well as the nadir (An) and Af pair had the most significant best fit lines (R2 values of 0.946 and 0.957 respectively) The An-Af pairing was marginally better in that it deviated less from the 1:1 line than the Af-Bf pairing For the Bartlett Forest wetlands, the regression statistics for camera pairs were quite low (R2 <0.3) due to the presence of several outliers which will be discussed shortly

Figure 2 summarizes various wetland characteristics across view zenith angles at the three study sites Bowl-shaped and bell-shaped reflectance anisotropy have been observed in other studies of forested areas (e.g Pinty et al., 2002; Nolin, 2004; Asner, 2000; Goodin et al., 2004) Largest NIR/blue ratios and the most pronounced bowl-shaped anisotropy was observed for stressed estuarine aquatic and emergent vegetation (MF) at Howland Forest related to severe moisture stress in this saltwater habitat, and marked vertical variations in emergent and surface vegetation across the wetland Almost all of the wetlands sampled at the Harvard Forest site displayed bowl-shaped anisotropy (FR1), peaking at the An view zenith angle and decreasing at the aft view angles This may be a function of the solar illumination-view angle geometry at these latitudes, as well as the fact that most of wetlands in this region were freshwater in nature

In contrast, the wetlands at the Bartlett and Howland Forests displayed darkspots or decreases in the NIR/blue ratio at one of the A cameras or the Bf one At Howland Forest, the

Bf darkspot was observed for an upland needle-leaf forested wetland (U), while at Bartlett Forest, it corresponded to a lotic (riverside) upper perennial wetland with an unconsolidated bottom (HW) The dramatic Af darkspot at the Howland site was found in a region of aquatic/emergent vegetation (SA) where the herbaceous species resembled evergreen forests

at the other view angles, but residual wetland characteristics showed up as strong NIR absorption at the Af view angle At the Bartlett Forest, the Af darkspot corresponded to a forested broad-leaf deciduous wetland that was temporally flooded (BD) Larger overall NIR/blue ratios for the latter wetland at all view zenith angles allowed its distinction from the aquatic/emergent species observed at Howland Forest

Figure 2 Variations in NIR/blue ratio as a function of viewing angle for selected wetlands At Howland Forest - water and persistent emergent wetlands (W); water-dominated intertidal emergent and subtidal aquatic vegetation (WA); drying estuarine subtidal aquatic bed (DA); acid, saturated needle-leaf

forested wetland (AW); moisture stressed subtidal aquatic bed/intertidal emergent vegetation (MF); dead forested wetland (D1); transitional subtidal aquatic and intertidal emergent vegetation (SA); and upland needle-leaved evergreen forested wetland (U) At Bartlett Forest - high elevation wetlands with

a westerly aspect (HW); upper perennial wetland with an unconsolidated bottom (HA); dead needle-leaf forested wetland (D2); and broad-leaf deciduous wetland (BD) At Harvard Forest - freshwater

scrub/shrub wetland (PF01/SS1E) FR1 and freshwater scrub/shrub wetland (PF01/4E) FR2 [Wetland codes according to Cowardin et al., 1979]

Similarly, An darkspots observed at Bartlett and Howland Forests were attributable to different wetland types, with distinct NIR/blue ratios At Howland Forest, the An darkspot corresponded to upland, lotic, water-dominated subtidal and intertidal wetlands (WA), where the former displayed more vegetation on or below the water surface than the latter The An darkspot at Bartlett Forest was observed for both a forested, needle-leaf evergreen wetland that was dead (D2), as well as for a scrub-shrub, broad-leaf evergreen wetland that was acidic NIR/blue ratios were larger for the dead, forested wetland than for the acidic one, and were on the order of those observed for the subtidal wetlands at Howland Forest Finally, the Aa darkspot observed for the freshwater forested/shrub wetland at Harvard Forest (FR2) was twice the magnitude of that observed for an anomalous acidic, saturated needle-leaved evergreen emergent wetland at Howland Forest (AW)

Two other important across-view angle observations deal with water bodies and the role

of topography Deep “pure” water bodies (W) displayed low, almost constant ratios at all angles, with largest values at the Bf and Cf view angles High elevation wetlands with a westerly aspect (HW) were characterized by low NIR/blue ratios at the forward view angles,

a peak at the Aa view angle and decreasing at the other aft angles

Two important underlying factors that explain the differences in wetlands across New England were the antecedent moisture conditions and species composition Precipitation deficits across lowland regions in northern New England (Howland Forest), were neither observed at high elevations of similar latitudes (Bartlett Forest) nor in southern New England (Harvard Forest) Tables 1 and 2 highlight the above normal precipitation received near Bartlett and Harvard Forests that was in stark contrast to the long term dryness that

characterized the Howland Forest (Dupigny-Giroux, 2007) The acceleration of phenology under drought conditions (Dupigny-Giroux, 2001) may have accounted for anomalously high near-infrared radiances observed in the most stressed estuarine wetlands in the Howland Forest These dry intertidal emergent vegetation regions were characterized by a concentration of organic material near the surface of the water, and displayed the highest NIR/blue ratio of all wetlands sampled

Table 1 Statewide precipitation received in 2003 Rankings are given in parentheses with 1 being the driest year and 113 being the wettest in the 1895-2007 time frame

(Data courtesy National Climatic Data Center)

(Data courtesy National Climatic Data Center)

Bangor, Maine 22.6 mm (82.3 mm) 50 mm (75.56 mm)

North Conway, NH 79.5 mm (102.1 mm) 187.9 mm (105.4 mm) Amherst, MA 68.3 mm (100.3 mm) 202.9 mm (104.1 mm)

Multiple view angles (MVA) or multiangular imaging represents a yet to be explored use

of the remote sensing of wetlands The application of the NIR/blue ratio to wetlands at three experimental forests in New England revealed that the technique is independent of the vegetation physiology and more a function of the moisture conditions and species composition across the wetland types Wetlands at the Howland Forest site were the most stressed, reflecting both the long-term and short term moisture deficits across the region At the Harvard Forest, most of the wetland sampled were of similar vegetation density and health, displaying overlapping bowl-shaped anisotropy Darkspots were observed at the A and

B view angles at the Bartlett and Howland Forest sites, with differences in the magnitude of the NIR/blue allowing for distinction across wetlands of varying species composition, acidity, health and tidal regimes Finally, the interplay among topographic aspect, solar illumination

and view zenith angle produced low NIR/blue ratios at forward view angles and higher values

at aft ones for some high elevation, westerly sites

These data were obtained from the NASA Langley Research Center Atmospheric Sciences Data Center

Asner, G.P., Braswell, B.H., Schmil, D.S and Wessman, C.A (1998) Ecological Research

Needs from Multiangle Remote Sensing Data, Remote Sensing of Environment,

63(2):155-165

Asner, G.P (2000) Contributions of Multi-view Angle Remote Sensing to Land-surface and

Biogeochemical Research, Remote Sensing Reviews, 00, 1-26

Barnsley, M.J., Allison, D and Lewis, P (1997) On the information content of multiple view

angle (MVA) images, International Journal of Remote Sensing, 18, 1937-1960

Bicheron, P., Leroy, M., Hautecouer, O., and Breon, F.M (1997) Enhanced discrimination of boreal forest covers with directional reflectances from the airborne polarization and

directionality of Earth reflectances (POLDER) instrument, Journal of Geophysical Research, 102(29), 517-528

Cowardin, L.M., Carter, V., Golet, F.C and LaRoe, E.T (1979) Classification of Wetlands and Deepwater Habitats of the United States, U.S Fish and Wildlife Service, Washington, DC, FWS/OBS-79-31

Diner, D.J., Barge, L.M., Bruegge, C.J., Chrien, T.G., Conel, J.E., Eastwood, M.L., Garcia, J.D., Hernandez, M.A., Kurzweil, C.G., Ledeboer, W.C., Pignatano, N.D., Sarture, C.M and Smith, B.G (1998) The Airborne Multi-angle Imaging SpectroRadiometer

(AirMISR): Instrument Description and First Results, IEEE Transactions on Geoscience and Remote Sensing, 36(4), 1339-1349

Diner, D.J., Braswell., B.H., Davies, R., Gobron, N., Hu, J., Jin, Y., Kahn, R.A., Knyazikhin, Y., Loeb, N., Muller, J.-P., Nolin, A.W., Pinty, B., Schaaf, C.B., Seiz, G and Stroeve, J (2005) The value of multiangle measurements for retrieving structurally and radiatively

consistent properties of clouds, aerosols and surfaces, Remote Sensing of Environment,

97, 495-518

Dobson, J.E., Bright, E.A., Ferguson, R.L., Field, D.W., Wood, L.L., Haddad, K.D., Iredale III, H., Jensen, J.R., Klemas, V.V., Orth, R.J and Thomas, J.P (1995) NOAA Coastal Change Analysis Program (C-CAP): Guidance for Regional Implementation, NOAA Technical Report NMFS 123, Department of Commerce

Dupigny-Giroux, L-A and Lewis, J.E (1999) A Moisture Index for Surface Characterization

over a Semiarid Area, Photogrammetric Engineering and Remote Sensing, 65(8),

937-945

Dupigny-Giroux, L-A (2001) Towards characterizing and planning for drought in Vermont

Part I A Climatological Perspective, Journal of the American Water Resources Association, 37( 3), 505-525

Dupigny-Giroux, L.-A (2007) Using AirMISR to explore moisture-driven land use-land cover variations at the Howland Forest, Maine - A case study, Remote Sensing of Environment, 107, 376-384

Goodin, D.G., Gao, J and Henebry, G.M (2004) The Effect of Solar Illumination Angle and

Sensor View Angle on Observed Patterns of Spatial Structure of Tallgrass Prairie, IEEE Transactions on Geoscience and Remote Sensing, 42(1) 154-165

Hyman, A.H and Barnsley, M.J (1997) On the potential land cover mapping from

multiple-view-angle (MVA) remotely-sensed images, International Journal of Remote Sensing,

MISR, IEEE Transactions on Geoscience and Remote Sensing, 40(7),1561-1573

Privette, J.L (1995) Uses of a Bidirectional Reflectance Model with Satellite Remote

Sensing Data, Elements of Change 1995, Session I, AGCI

Tiner, R.W (2003) Correlating Enhanced National Wetlands Inventory Data with Wetland Functions for Watershed Assessments: A Rationale for Northeastern U.S Wetlands, U.S Fish and Wildlife Service, National Wetlands Inventory Program, Region 5, Hadley, MA 26pp

U.S Fish and Wildlife Service (2004) Technical Procedures for Wetlands Status and Trends, Operational Version, Arlington, VA

Valta-Hulkkonen, K., Pellikka, P., Tanskanen, H., Ustinov, A and Sandman, O (2003)

Digital false colour aerial photographs for discrimination of aquatic macrophyte species, Aquatic Botany, 75, 71-88

Widlowski, J.-L., Pinty, B., Gobron, N., Verstraete, M.M., Diner, D.J and Davis, A.B (2004) Canopy structure parameters derived from multi-angular remote sensing data for

terrestrial carbon studies, Climate Change, 67, 403-415

Zhang, Y., Tian, Y., Myneni, R.B., Knyazikhin, Y and Woodcock, C.E (2002a) Assessing the information content of multiangle satellite data for mapping biomes I Statistical

analysis, Remote Sensing of Environment, 80, 418-434

Zhang, Y., Shabanov, N., Knyazikhin, Y and Myneni, R.B., (2002b) Assessing the

information content of multiangle satellite data for mapping biomes II Theory, Remote Sensing of Environment, 80, 435-446

Chapter 1

W ETLANDS : W ATER “L IVING F ILTERS ”?

Ana Dordio1∗, A J Palace Carvalho1,2 and Ana Paula Pinto1,3

1Department of Chemistry, University of Évora, Évora, Portugal

2Centro de Química de Évora, University of Évora, Évora, Portugal

3ICAM – Instituto de Ciências Agrárias e Mediterrâneas,

University of Évora, Évora, Portugal

Human societies have indirectly used natural wetlands as wastewater discharge sites for many centuries Observations of the wastewater depuration capacity of natural wetlands have led to a greater understanding of the potential of these ecosystems for pollutant assimilation and have stimulated the development of artificial wetlands systems for treatment of wastewaters from a variety of sources Constructed wetlands, in contrast

to natural wetlands, are human-made systems that are designed, built and operated to emulate wetlands or functions of natural wetlands for human desires or needs Constructed wetlands have recently received considerable attention as low cost, efficient means to clean-up not only municipal wastewaters but also point and non-point wastewaters, such as acid mine drainage, agricultural effluents, landfill leachates, petrochemicals, as well as industrial effluents Currently, untreated wastewater discharge

in the natural wetlands sites is becoming an increasingly abandoned practice whereas the use of constructed wetlands for treatment of wastewater is an emerging technology worldwide However, natural wetlands still play an important role in the improvement of water quality as they act as buffer zones surrounding water bodies and as a polishing stage for the effluents from conventional municipal wastewater treatment plants, before they reach the receiving water streams In fact, one of the emerging issues in environmental science has been the inefficiency of wastewater treatment plants to remove several xenobiotic organic compounds such as pesticides and pharmaceutical residues and consequent contamination of the receiving water bodies Recent studies have shown that wetlands systems were able to efficiently remove many of these compounds, thus reaffirming the importance of the role which can be played by wetlands in water quality preservation

∗ Corresponding author: Tel: +351 - 266 745343; E-mail address: avbd@uevora.pt

The aim of this work is to present a review on the application of wetlands as “living filters” for water purification Emphasis was focused on the removal of micropollutants, especially xenobiotic organic compounds such as pharmaceuticals residues, which are not efficiently removed by conventional municipal wastewater treatment plants Furthermore, the role of wetlands as protection zones which contribute to the improvement of the aquatic ecosystems’ quality will be discussed

Wetlands have been recognized throughout human history to be a valuable natural resource Their importance has been appreciated in managed forms, for example rice paddies, particularly in South East Asia, but also in their natural state by such people as the Marsh Arabs around the confluence of the rivers Tigris and Euphrates in southern Iraq (Mitsch and Gosselink J.G., 2000) Benefits provided by wetlands include water supply and control, mining, use of plants, wild-life, integrated systems and aquaculture, erosion control, education and training, recreation and reclamation (USEPA and USDA-NRCS, 1995; Cooper

et al., 1996; Vymazal et al., 1998a; USEPA, 2000; Sundaravadivel and Vigneswaran, 2001) The water purification capability of wetlands, in particular, has for long been recognized Natural wetlands usually improve the quality of water passing through them, acting as “living filters” and serving as transitional zones or “ecotones” between terrestrial and aquatic systems (Mitsch and Gosselink J.G., 2000; Sundaravadivel and Vigneswaran, 2001) They provide several physical, chemical, and biological processes which allow for the depuration of pollutants resulting from point and non-points source, thereby contributing for an improvement of water quality In many regions, natural wetlands have been used, for centuries, as convenient wastewater discharge sites and sinks for a wide variety of anthropogenic pollutants including toxic organic compounds (Kadlec and Knight, 1996; Vymazal, 1998)

Despite the many benefits offered by wetlands, some of these areas have also been for long regarded as wasted, useless land, unsuitable for agriculture, and subjected to drainage in order to make them available for cultivation Since the early 20th century, wetland losses attributed to agriculture have been dramatic Extensive wetland draining in the 1960s and 1970s led to increased available agricultural production acreage However, in many places, in parallel with this practice, a decline has been observed in the water quality of the neighboring water bodies An aggravated potential for damage to the aquatic systems, such as increased sedimentation or fish kills, is expected when rivers, streams, and lakes adjacent to the former wetland areas receive runoff following rainfall events The functional role of wetlands in improving water quality has been, in recent years, a compelling argument for their preservation and study The realization of the importance of wetlands, adjacent to other water bodies, has resulted in the fact that drainage of wetlands has ceased in many countries and that even previously drained wetlands are restored

The water treatment capabilities of wetlands are thus generally recognized but the extent

of their treatment capacity is largely unassessed However, studies have led to both a greater understanding of the potential of natural wetland ecosystems for pollutant assimilation and the design of new natural water treatment systems inspired in these natural systems There remain, however, concerns over the possibility of harmful effects resulting from toxic

compounds and pathogens that may be present in many wastewater sources Also, there are concerns that there may be a potential for long-term degradation of natural wetlands due to the addition of nutrients and changes in the natural hydrologic conditions influencing these systems At least in part due to such concerns, there has been a growing interest in the use of constructed wetlands systems (CWS) for wastewater treatment

Significant advances have been made in the last years in the engineering knowledge of creating artificial wetlands that can closely imitate the treatment functions that occur in the natural wetland ecosystems These CWS can be defined as man-made systems that have been designed and constructed to utilize the natural processes involving wetland vegetation, soils, and their associated microbial populations to assist in treating wastewater (Hammer and Bastian, 1989; Vymazal, 1998) They are designed to take advantage of many of the same processes that occur in natural wetlands, but do so within a more controlled environment While some CWS have been designed and operated with the sole purpose of treating wastewater, others have been implemented with multiple-use objectives in mind, such as using treated wastewater effluent as a water source for the creation and restoration of wetland habitat for wildlife use and environmental enhancement

The construction of artificial wetlands for the treatment of wastewater has been developing fast over the last decades and it represents now a widely accepted and an increasingly common treatment alternative The many advantages offered by CWS such as simplicity of design and lower costs of installation, operation, and maintenance make them an appropriate alternative for both developed and developing countries (USEPA and USDA-NRCS, 1995; Vymazal et al., 1998a; USEPA, 2000)

In the following sections of this text the water purification functions of natural wetlands are presented in greater detail and, afterwards, the constructed wetland systems are described Studies on the removal of several types of pollutants by these systems, as well as the more recent new trends on the use of CWS for pollutants removal are discussed

2.1 Definition and Characterization

Wetlands encompass a broad range of wet environments, ranging from submerged coastal grass beds to salt marshes, swamp forests and boggy meadows (USEPA and USDA-NRCS, 1995; Kadlec and Knight, 1996; Vymazal et al., 1998a; Sundaravadivel and Vigneswaran, 2001)

A single precise definition and classification for wetlands that can correctly describe them in a comprehensive way for most purposes still has not been developed In fact, a definition for wetlands has long been the subject of debate, due to the great variety of environments which are, either permanently or seasonally, influenced by water as well as to the specific requirements of the diverse groups of people involved in the study and management of these systems Terms used in wetlands classification are many and are often confusing Still, they are important for both the scientific understanding of these systems and for their proper management

The Ramsar Convention, which in 1971 brought a worldwide attention to wetlands, took

a broad approach in its definition in the text of the Convention (Article 1.1) (UNESCO, 1994):

“Wetlands are areas of marsh, fen, peatland or water, whether natural or artificial, permanent or temporary, with water that is static or flowing, fresh, brackish or salt, including areas of marine water the depth of which at low tide does not exceed six metres”

In addition, for the purpose of protecting coherent sites, the Article 2.1 stipulates in order

to be included in the Ramsar List of internationally important wetlands, they may incorporate:

“riparian and coastal zones adjacent to the wetlands, and islands or bodies of marine water deeper than six metres at low tide lying within the wetlands”

Another definition of wetlands was proposed by the U.S Fish and Wildfire Services, which also developed a classification system capable of encompassing and systematically organizing for scientific purposes all types of wetland habitats According to such view, wetlands are described as the transition areas between terrestrial and aquatic systems, where water is the dominant factor determining soil characteristics and development of associated biological communities The definition specifies that wetlands need, at least periodically, to fulfill one or more of the following four requirements (Hammer and Bastian, 1989; Cowardin and Golet, 1995; Brady and Weil, 2002):

· areas where the water table is at or near the surface or where the land is covered by shallow water;

· areas supporting predominantly hydrophytes (water-tolerant plant species);

· areas with predominantly undrained hydric soils Hydric soils are those that are sufficiently wet for long enough to produce anaerobic conditions, thereby limiting the types of plants that can grow on them;

· areas with non-soil substrate (such as rock or gravel) that are saturated or covered by shallow water at some time during the growing season of plants

The U.S Fish and Wildlife Service classification system (Cowardin and Golet, 1995) is much like the hierarchical system used by scientists to classify plants and animals, starting out with five large systems and progressively subdividing into a series of subsystems, classes and subclasses, which are then characterized by examples of dominant types of plants and animals This system thus provides a consistent standard of terminology to be used among scientists and specialists

Various legislation and agency regulations define wetlands in more general terms The U.S Environmental Protection Agency (EPA) and the U.S Army Corps of Engineers jointly define wetlands as (Environmental Laboratory, 1987):

“Those areas that are inundated or saturated by surface or ground water at a frequency and duration sufficient to support, and that under normal circumstances do support, a prevalence of vegetation typically adapted for life in saturated soil conditions Wetlands generally include swamps, marshes, bogs, and similar areas”

One of the most recent definitions has been used by the U.S National Research Council, which defines wetlands as (National Research Council, 1995; Vymazal et al., 1998a):

“an ecosystem that depends on constant or recurrent, shallow inundation or saturation at

or near the surface of the substrate”

Notwithstanding which of the definitions one may use, three major factors are salient in the characterization of a wetland: water (hydrology), substrate (physico-chemical features) and biota (type of vegetation and microbial activity)(National Research Council, 1995) The characteristics of all these three components are interdependent and conditioned by each other It is from the complex interactions among them that results the values and functions of wetlands

2.2 Natural Wetlands as Natural Water “Living Filters”?

Long regarded as wastelands, wetlands are now recognized as important features in the landscape that provide numerous beneficial functions for people and for fish and wildlife These services, considered valuable to societies worldwide, are the result of the wetlands’ inherent and unique natural characteristics

Wetlands support a rich diversity of wildlife and fisheries by being stopping-off points and nesting areas for migratory birds and spawning grounds for fish and shellfish Those wetlands along the coasts, riverbanks and lakeshores have a valuable role in stabilizing shorelands and protecting them from erosion One of the greatest benefits of inland wetlands

is the natural flood control or buffering provided for downstream areas by slowing the flow of floodwater, desynchronizing the peak contributions of tributary streams and reducing peak flows on main rivers (Hammer and Bastian, 1989; USEPA and USDA-NRCS, 1995) Some wetlands may function as discharge areas for groundwaters, allowing stored groundwater to sustain surface base flow in streams during dry periods (Hammer and Bastian, 1989) Additional benefits provided by these natural systems include mining (peat, sand, gravel), use

of plants (staple food plants, grazing land, timber, paper production, roofing, agriculture,

horticulture, fodder), integrated systems and aquaculture (e.g fish cultivation combined with

rice production), energy (hydroelectric, solar energy, heat pumps, gas, solid and liquid fuel) education and training, recreation and reclamation (USEPA and USDA-NRCS, 1995; Vymazal et al., 1998a)

Perhaps one of the most important but least understood functions of wetlands is water quality improvement These systems may well be considered “natural purifiers of water” as they provide an effective treatment for many kinds of water pollution (Hammer and Bastian, 1989; Kadlec and Knight, 1996) In fact, a capacity has already been recognized in wetlands

to efficiently reduce or remove large amounts of pollutants from point sources (e.g municipal and certain industrial effluents) as well as nonpoint sources (e.g mining, agricultural and urban runoff) including organic matter, suspended solids, excess of nutrients, pathogens, metals and other micropollutants (Hammer and Bastian, 1989)

This pollutants removal is accomplished by the interdependent action of several physical, chemical and biological processes which include sedimentation, filtration, chemical precipitation, sorption, biodegradation, plants uptake among others The mechanisms and the

interdependences among the wetlands components (water, substrate and biota) are complex and not yet entirely understood, although some progresses have been achieved in the latest years as the awareness to the water depurative functions of wetlands becomes more widespread

The hydrology of the sites, the soil and the biota (vegetation and microorganisms) are reportedly the main factors influencing water quality in wetlands

2.3 Factors Influencing Water Quality

The hydrological cycle emerges with an underlying major role as it influences the type of vegetation, microbial activity and biogeochemical cycling of nutrients in soil Indeed, the biotic status of a wetland is intrinsically linked to the hydrological factors, which affect the nutrient availability as well as physicochemical parameters such as soil and water pH and anaerobiosis within soils In turn, biotic processes will have an impact upon the hydrological conditions of a wetland (Mitsch and Gosselink J.G., 2000; Kivaisi, 2001)

Soil is one of the most important physical components of natural wetlands Physical and chemical characteristics of the soil can greatly influence the type of wetland plants that will

be prevalent over its surface and the microbial populations that will live on the soil phase In addition, soil characteristics such as acid-base properties, redox potential and sorption capacity will also determine the type of physical-chemical processes occurring within the aqueous medium that can be responsible for the removal of certain types of pollutants, with a major impact in water quality

Macrophytes are the dominant vegetation in wetlands These plant species are typically adapted to water saturated conditions and are able to persist in anaerobic soil conditions as a result of high water content Compared with the vegetation of well-drained soils, wetland plants have a worldwide similarity which overrides climate and is imposed by the common characteristics of a free water supply and the abnormally hostile chemical environment which plant roots must endure It is not surprising that plants regularly found in wetlands have evolved functional mechanisms to deal with the environmental stresses

Virtually all wetland plants have elaborate structural mechanisms to avoid root anoxia Rhizosphere oxygenation is considered essential for active root function, and also enables the plants to counteract the effects of soluble phytotoxins, including sulfides and metals, which may be present at high concentrations in anoxic substrates

Microorganisms play a central role in the biogeochemical transformations of nutrients (Cooper et al., 1996; Vymazal et al., 1998b; Stottmeister et al., 2003; Vymazal, 2007), and the metabolism of organic compounds including even some xenobiotic compounds (Machate

et al., 1997; Stottmeister et al., 2003) There is a close interdependence between microorganisms and vegetation Much of the plants nutrients are the result of the mineralization of more complex compounds by the microorganisms, whereas the activity of the latter is stimulated by enzymes released in root exudates The aerobic conditions provided

by the plants in their rhizosphere will also be determinant for the type of microbial populations and bioprocesses available in this region

The conjugation of all these factors and interactions between different wetlands components and their associated processes lead to essentially different abilities to interact with water pollutants by different types of wetlands An overview of the abilities by different

types of natural wetlands to cope with various non-point pollution problems along with a summary of each wetland type characteristics is presented in table 1

Table 1 Characteristics of different types of natural wetlands and their ability to retain

non-point source pollutants (IETC-UNEP, 1999)

Type of

Wetland Characteristics

Ability to retain non-point source pollutants

Wet meadows Grassland with waterlogged

soil; standing water for part of the year

Denitrification only in standing water; removal of nitrogen and phosphorus by harvest

Fresh water

marshes

Reed-grass dominated, often with peat accumulation

High potential for denitrification, which

is limited by the hydraulic conductivity Forested

wetlands

Dominated by trees, shrubs;

standing water, but not always for the entire year

High potential for denitrification and accumulation of pollutants, provided that standing water is present

with minor flows

High potential for denitrification but limited by small hydraulic conductivity Shoreline

wetlands

Littoral vegetation of significant importance for lakes and reservoirs

High potential for denitrification and accumulation of pollutants, but limited coverage

In spite of the general abilities for water depuration that can be observed for typical wetland configurations, it is very difficult to predict responses to water pollution by natural wetlands and to translate their behavior from one geographical area to another due to the extreme variability of the functional components that characterizes them Therefore, natural wetlands can not be viewed as a systematic approach to wastewater treatment Only in a controlled environment provided by constructed wetlands, can such treatment work in a reliable and reproducible manner

2.4 Natural Wetlands Preservation through the Construction of

Artificial Wetlands

Currently, in many countries, natural wetlands are protected areas, thus meaning that wastewater application is not permitted Although studies have shown that natural wetlands are able to provide high levels of wastewater treatment (Hammer and Bastian, 1989), there is concern over possible harmful effects of toxic compounds and pathogens in wastewaters and

a long term degradation of wetlands due to additional nutrient and hydraulic loadings from wastewater These potential benefits and concerns have promoted a growing interest in the use of artificial wetlands for wastewater treatment (USEPA and USDA-NRCS, 1995)

While the application of wastewater to natural wetlands is becoming a deprecated practice worldwide, studies conducted on these systems have led to both a greater understanding of the processes involved in pollutant assimilation and removal as well as

suggesting the design of new natural water treatment systems where these water depuration capabilities would be imitated and improved (Vymazal et al., 1998a) Using the knowledge and the experience with the assimilative capacity of natural wetlands, the construction of man-made wetland systems (constructed wetlands) for wastewater treatment has therefore been proposed The functional role of wetlands in improving water quality, thus, becomes a compelling argument for the preservation of natural wetlands and in recent years the construction of wetlands systems for wastewater treatment

Constructed wetlands can be built with a much greater degree of control, using a defined composition of substrate, type of vegetation, and flow pattern In addition, constructed wetlands offer several additional advantages compared to natural wetlands including site selection, flexibility in sizing and, most importantly, control over the hydraulic pathways and retention time (Brix, 1993)

Recent concerns over wetlands losses have generated a need for creation of wetlands, which are intended to emulate the functions and values of natural wetlands that have been destroyed Such CWS can be defined as a designed and man-made complex of saturated substrates, emergent and/or submergent vegetation, animal life, and water that simulates natural wetlands for human use and benefits (Hammer and Bastian, 1989) Artificial wetlands are engineered or constructed for one or more of the following purposes as indicated by specific descriptive terminology (Kadlec and Knight, 1996; Sundaravadivel and Vigneswaran, 2001):

creation of wetland habitats to compensate for natural wetlands which have been converted for agriculture and urban development (or help offset their rate of conversion) and hence to conserve native flora and fauna including aquatic plants, fish, water birds, reptiles, amphibians and invertebrates (Constructed habitat wetlands)

• flood control facility (Constructed flood control wetland)

• production of food and fiber (Constructed aquaculture wetlands) and

• water quality improvement and wastewater treatment system (Constructed treatment wetlands)

Although CWS are being developed in many parts of the world for various functions, their wastewater treatment capabilities have attracted research efforts for a wide range of treatment applications including domestic wastewaters (Hammer and Bastian, 1989; Cooper

et al., 1996; Vymazal et al., 1998a; Kivaisi, 2001; Cooper, 2001; Cameron et al., 2003; Hench

et al., 2003; Solano et al., 2004), urban storm-water (Livingston, 1989; USEPA, 1993; Scholes et al., 1998; Carleton et al., 2001; Kohler et al., 2004), agricultural wastewaters (Carty et al., ; Hammer et al., 1989; Cronk, 1996; Knight et al., 2000), landfill leachates (Barr and Robinson, 1999; Nivala et al., 2007), acid mine drainage (Brodie et al., 1989; Ledin and Pedersen, 1996; Sobolewski, 1999) and for polishing advanced treated municipal wastewater for return to freshwater resources CWS are also used for treating eutrophic lake waters (D'Angelo and Reddy, 1994; Coveney et al., 2002) and for conservation of nature (Hammer