INTRODUCTION
Background
Water is an integral part of human being, as well as all the species on the Earth
Water is essential for all living beings, constituting up to 90% of some organisms and around 60% of the human adult body The Earth is composed of approximately 80% water, with 97.2% being salt water from the oceans, 2.15% frozen in glaciers, and only 0.67% available as fresh water in reservoirs like groundwater, lakes, and streams, as well as water vapor in the atmosphere Unfortunately, only a small fraction of this fresh water is accessible for human use.
Many communities today face severe water shortages, struggling to access clean and safe water necessary for their survival As living standards rise, environmental pollution, particularly water pollution, becomes a significant concern, adversely affecting both daily activities and public health due to waterborne diseases A World Bank study from 1995 revealed that approximately 80% of diseases in developing countries stemmed from contaminated water, resulting in around 10 million deaths each year—an alarming average of 27,000 premature deaths daily, with over half being children under the age of five (Miller, 1997).
Water pollution is a significant issue, primarily caused by toxic chemicals and heavy metals like lead (Pb), mercury (Hg), and arsenic (As) These pollutants originate from both industrial activities and everyday household practices Even at low concentrations, they can accumulate in biological systems, leading to various diseases and disorders (Pehlivan et al., 2009).
Lead (Pb) is a highly hazardous pollutant, as noted by Sharma and Dubey (2005), with its presence in soil and water linked to industrial effluents, fuel usage, and agricultural pesticides and fertilizers This contamination poses significant risks to living organisms, making lead pollution a pressing global issue today.
Numerous approaches have been explored by researchers for the remediation and treatment of heavy metal-contaminated areas, but these methods often prove to be costly, inefficient, and technically challenging to implement (Raymond and Felix, 2011).
Recent studies have investigated alternative methods for assessing metal toxicity levels in water, including phytoremediation This technique effectively extracts and removes inactive metals and contaminants from polluted water, demonstrating itself as an efficient and cost-effective solution to current environmental challenges (Bieby et al., 2011).
Research Objective
This research aims to explore the phytoremediation method for the extraction and elimination of inactive heavy metal lead (Pb) and its contaminant, lead nitrate (Pb(NO3)2), from polluted water The study specifically investigates the absorption capabilities of the Najas indica plant in contaminated water, with the goal of enhancing water quality and promoting sustainable water sources.
Research questions
- What is phytoremediation? How does it work?
- How do the Pb and Pb(NO 3 ) 2 effect water quality and human life?
- How Pb and Pb(NO 3 ) 2 can absorbed by Najas indica?
Limitations
- Limited plants can be used and take a long time (time-consuming process)
- The success of phytoremediation may be limited by some factors such as: Growing time, growth rate, climate, root depth, level of contaminant
High levels of pollutants can hinder plant growth, potentially restricting their use in certain areas Additionally, plants can accumulate significant amounts of toxic metals, which poses further risks to their health and the environment.
- Metal-accumulating plants need to be harvested and either recycled or disposed with applicable regulations
- Contaminants may enter the food chain through animals/insects that eat plant material containing contaminant.
LITERATURE REVIEW
Overview of phytoremediation
Phytoremediation, a term derived from the Greek word "phyto" meaning plant and the Latin "remedium" meaning to correct, was first introduced in 1991 This innovative process involves studying the selective uptake capabilities of aquatic plant root systems, alongside their abilities for translocation, bioaccumulation, and degradation of contaminants Understanding these mechanisms highlights the advantages and disadvantages of using phytoremediation as an effective environmental cleanup strategy.
Phytoremediation is a method of cleaning contaminated soil and water by utilizing specific plants and trees that absorb or degrade pollutants, thereby enhancing environmental quality.
There are some different definitions of phytoremediation by scientists:
Phytoremediation is an innovative technology that utilizes various plants to effectively degrade, extract, contain, or immobilize contaminants from soil and water This method serves as a sustainable solution for environmental cleanup, harnessing the natural abilities of plants to address pollution issues (USEPA, 2000).
- The use of vascular plants to remove pollutants from the environment or to render them harmless (Bhattacharya, et al, 2006)
Engineered green plants are utilized to effectively remove, contain, or neutralize environmental contaminants such as heavy metals, trace elements, organic compounds, and radioactive materials in soil and water.
The phytoremediation of metals is a cost-effective and ‘green’ technology based on the use of metal-accumulating plants to remove toxic metals, including radionuclides, from soil and water (Raskin, 1997)
Phytoremediation employs various complex mechanisms for contaminant attenuation, tailored to specific contaminants Key processes include phytoextraction, phytovolatilization, rhizodegradation, phytostabilization, photodegradation, and rhizofiltration, each contributing uniquely to environmental cleanup efforts (Burken et al., 2000; Meagher, 2000).
Phytoextraction, also known as phytomining, involves the absorption of contaminants by plant roots, which are then translocated to the above-ground parts of the plants, or shoots These shoots can be harvested and burned to generate energy while recycling metals from the resulting ash (Erakhrumen and Agbontalor, 2007).
Phytoextraction is a bioremediation process that utilizes specific plants to absorb and store harmful pollutants, including toxic metals, from the environment When certain heavy metals, organic compounds, and radionuclides resist plant metabolism, these substances can still be taken up and transported within plant tissues in a recoverable form (U.S EPA, 2000).
This process primarily used in the treatment of soil, sediments, and sludges Sometime, phytoextraction can be used for treatment of contaminated water in low level (Emanuel, 2014)
Ethylenediaminetetraacetic acid (EDTA) is effectively utilized in the phytoextraction process to remove toxic heavy metals such as cadmium (Cd), copper (Cu), nickel (Ni), lead (Pb), and zinc (Zn) from contaminated soil and water, particularly when applied to plants days before harvest EDTA enhances the solubility of these metals by forming complex substances, which reduces free-metal activity and facilitates the release of bound metal ions As plants absorb significant amounts of EDTA, they also take up and translocate heavy metals like lead as an EDTA complex, continuing this process until all EDTA-extractable metals are depleted (Raskin et al., 1997; Blaylock et al., 1997).
Phytovolatilization is the process by which plants absorb contaminants during their growth and subsequently release them into the atmosphere through transpiration As water circulates through the plant's vascular system from the roots to the leaves, pollutants are transformed and altered This phenomenon occurs in growing trees and plants that take up both water and organic contaminants, which are then evaporated or transpired into the air (Sukha R.V and Srivastava P.N, 2008).
This technique facilitates the movement of pollutants from soil and water into the atmosphere, posing significant risks to human health and ecosystems due to elevated levels of toxic compounds (U.S EPA, 2000).
Rhizodegradation, on the other hand, uses rhizospheric components of plants and soil microbes in order to degrade and break the contaminants U S Environmental
Rhizodegradation, as defined by the Protection Agency (2000), refers to the microbial breakdown of organic contaminants occurring in the soil's root zone This process is also recognized by several terms, including plant-assisted degradation, plant-assisted bioremediation, plant-aided in situ biodegradation, and enhanced rhizosphere biodegradation.
Phytostabilization is an effective method for reducing soil and water pollution by immobilizing contaminants through the absorption and accumulation of plant roots This technique also involves the precipitation of pollutants within the root zone and utilizes plant medium to prevent the movement of toxic substances caused by erosion, leaching, and dispersion.
Phytostabilization primarily takes place in the root zone's microbiological environment, influenced by changes in soil conditions and the presence of toxic substances This process is facilitated by mechanisms such as sorption, precipitation, complexation, and the reduction of metal valence, enhancing the likelihood of effective phytostabilization (EPA, 1997a).
Plants play a crucial role in stabilizing soil and minimizing wind and water erosion, which helps prevent the spread of contaminants in the environment Additionally, the organic compounds associated with lignin in plants contribute to a process known as phytolignification, a form of phytostabilization that enhances soil health and integrity (Cunningham et al., 1995b).
Phytodegradation is another method existing that helps the metabolism of harmful chemicals within the plant tissues Also known as phytotransformation, the plants
Sukha and Srivastava (2008) describe a mechanism that enables plants to uptake pollutants, metabolize them, and subsequently break them down before releasing them into the atmosphere This process is effective in treating pollutants found in soil, sediments, as well as ground and surface waters (U.S EPA, 2000).
Overview of heavy metals
Metals are classified into two categories: light metals, which have densities ranging from 0.860 to 5.0 gm/cm³, and heavy metals, with densities between 5.308 and 22.000 gm/cm³ Heavy metals can be further divided into three types: toxic metals, including mercury (Hg), chromium (Cr), lead (Pb), zinc (Zn), copper (Cu), nickel (Ni), cadmium (Cd), arsenic (As), cobalt (Co), and tin (Sn); precious metals, such as palladium (Pd), platinum (Pt), and gold (Au).
Over 20 metals are identified as toxic, with around half of them released into the environment, significantly increasing risks to human health (Akpor and Muchie, 2010) These include precious metals like silver (Ag) and ruthenium (Ru), as well as radioactive elements such as uranium (U), thorium (Th), radium (Ra), and americium (Am).
Heavy metals are generally characterized by their high atomic number, atomic weight, and a specific gravity exceeding 5.0, although there is no precise definition for them Common heavy metal contaminants include cadmium (Cd), chromium (Cr), copper (Cu), mercury (Hg), lead (Pb), and zinc (Zn).
Heavy metal contaminants can be founded in common sources such as: mining, industrial activities, fertilizer and pesticide in agricultural activities, etc
Heavy metals are non-toxic in their elemental form, but when combined with other anions, they can become highly toxic to living organisms Essential heavy metals like iron, zinc, magnesium, cobalt, manganese, molybdenum, and copper are crucial for human health, albeit in trace amounts necessary for metabolism However, excessive levels of these essential elements can pose serious health risks to organisms (Foulkes, 2000).
Heavy metal contaminants, such as lead (Pb), cobalt (Co), and cadmium (Cd), are stable and persist in the environment for thousands of years, posing significant risks to living organisms, soil microflora, and plant growth (Pehlivan et al., 2009) These toxic metals cannot be biodegraded and can accumulate in living organisms, leading to various diseases and disorders, even at low concentrations Among these, lead is the most prevalent heavy metal contaminant (Dj Maio, 2001).
2.2.2 Lead (II) Nitrate in environment
Lead (II) nitrate, an inorganic compound with the formula Pb(NO3)2, is water-soluble and recognized for its toxicity Classified as an oxidizing agent, it is also deemed probably carcinogenic to humans by the International Agency for Research on Cancer (Revolvy Group, 2002).
Lead(II) nitrate can infiltrate the food chain, leading to bioaccumulation that poses significant health risks to humans Exposure to lead is linked to various diseases affecting hemoglobin synthesis, renal function, nervous system health, and reproductive capabilities (ATSDR, 2005).
Lead (II) (Pb 2+) is highly toxic to humans when present in significant quantities, and due to its non-biodegradable nature, it poses a persistent risk of exposure once environmental contamination occurs The presence of metal pollutants like lead adversely affects biological systems and remains in the environment indefinitely (Pehlivan et al., 2009).
High environment lead levels will never return to normal if there is no remedial treatment
In the environment, lead (II) nitrate is known to be toxic to plants, animals, and microorganisms Lead (II) nitrate Pb(NO3)2 contamination in the environment exists
Lead (Pb) accumulates in various aquatic plants, despite being a non-essential metal for plant metabolism Its presence can stimulate the formation of free radicals and reactive oxygen species (ROS), leading to potential damage to plant cells (Andra et al., 2010; Kazina et al., 2005).
Lead (Pb) is known to generate reactive oxygen species (ROS) and increase the activity of antioxidant enzymes The oxidative stress caused by ROS leads to several detrimental effects in plant cells, including reduced photosynthetic activity, decreased ATP production, lipid peroxidation, and DNA damage (Ruley et al., 2004).
Overview of Najas Indica
Najas indica, a species prevalent in various Asian countries and notably widespread in China, thrives in paddy fields, ponds, and lakes Currently, it is classified as Least Concern, with no reported threats to its global population While it is locally common, there is a lack of information regarding global population trends (Encyclopedia of Life, 2012).
Najas indica is a species of aquatic plant found in freshwater habitats, especially still or slow-moving waters, like ponds and rice fields The flowers are monoecious (Chamisso et al, 1829)
- Global Distribution: Tropical Asia and Africa
- Distribution: Found in China and tropical Asia It has been recorded from India, Japan, Thailand, Myanmar, Viet Nam, Indonesia, and New Guinea (Figure 1)
- Habitat and Ecology: It grows in paddy fields, ponds and lakes
-General habitat: Streams, ditches and ponds
-Flowering class: Monocot Habit: Herb
Figure 1 Distribution map of Najas Indica (Encyclopedia of Life, 2012)
Najas indica is a fully submerged, floating plant with long narrow leaves (Figure 2) These features are provided a large surface area for metal adsorption and absorption potential (Sight et al, 2010)
Lysis process
Lysis refers to the disintegration or dissolution of cells, resulting in the destruction of plant cell membranes by chemical substances (Merriam-Webster Dictionary; Houghton, 2002) Research by Pinchasov et al (2006) indicates that lead (Pb) negatively impacts photosynthesis by reducing chlorophyll content As lead accumulation increases, the chlorophyll levels in Najas indica plants decrease, causing a noticeable color change from green to light brown, resembling withered plants.
MATERIALS AND METHODS
Place and date
- This study was conducted from March, 2015 to April 2015 in the laboratory of Integrated Postgraduate, Sriwijaya University, Palembang, Indonesia
- Analysis of Pb concentration in Najas indica plants and water samples are conducted at the Laboratory of the Science Faculty of Chemistry, University of Sriwijaya, Indralaya, Indonesia
This experiment was conducted from March to April 2015 The experiment conduction process concludes:
- Taking whole sample plants that all have green leaves, in Jakabaring lake (3 basins) on 11/03/2015 and moved to laboratory of Integrated Postgraduate, Sriwijaya University, Palembang, Indonesia in the same day
- Acclimation time for Najas indica in new environment that is in tap water, under laboratory condition on 12/03/2015
- The experiment started on 15/03/2015 by taking samples for day 0, then continue to applying Lead (II) nitrate (Pb(NO 3 ) 2 ) for all the treatments except control treatment
- 20 th March 2015 started to observation and sampling for day 5, after that, each
5 days need observed and sampled for day 10, 15, 20
- Destruction samples after one day of each time observed and sampled, and
Materials
The materials used in this study were the following:
- Test species: Najas indica plant (Figure 3)
Figure 3 Najas Indica plant samples taken in Jakarbaring Lake,
- Test chemical: Standard stock solution of Pb (NO 3 ) 2 1000 ppm and Nitric Acid (HNO 3 ) 65%.
Equipment
The equipment used in the research:
• Atomic Absorption spectrophotometer (AAS) (Analytical technique that measures the concentration of elements)
• Fume hood machine, hot place, incubator oven
• Vacuum pump and compressor filtered machine
• Glass plates, glass flasks, glass funnels, measuring cup.
Methods
The research employs a completely randomized design (CRD) featuring two factors: the type of plant, Najas indica, and varying concentrations, with three replications for each condition.
2 Factor 2: Treatment variations with 4 levels of Pb(NO 3 ) 2 , namely:
Pb concentration Replication 1 Replication 2 Replication 3
A is plant (Najas indica) and B is the treatment
Plants were randomly selected from uniformity of conditions, namely: coming from the same place to grow, with the criteria of the plant length 10 cm to 15 cm, the
After sample selection, clean plants by fresh water to wash away sediment
Twelve samples of Najas indica plants, each weighing 300 grams, were prepared for the experiment These samples were divided into four treatments with three replications each and placed in 12 plastic containers Each container has a diameter of 90 cm and a height of 30 cm, filled with 20 liters of water.
- Taking 12 samples which without Pb(NO 3 ) 2 for day 0, each sample is 55 gram of Najas indica plant without water in each container
- Next step is applying 4 treatments of Lead (Pb): 0 ppm (control), 5 ppm, 10 ppm, 15 ppm Lead solution obtained from the stock standard solution of Pb(NO 3 ) 2
1000 ppm Apply the formula below to dilute Pb(NO 3 ) 2 stock solution to 5 ppm, 10ppm, 15 ppm:
- With: V 1 is Pb volume that we need to dilute from stock solution in 20 litter of tap water
- V 2 is volume of tap water (20litter)
- M 1 is original concentration of stock solution (1000ppm)
- To get 5 ppm of Pb(NO 3 ) 2 solution in 20 litter of tap water for one B 2 replication, use formula (*) :
- Three replications for B 2 treatment we need: 100ml x 3= 300ml of Pb(NO 3 ) 2 /3treatments
Similar for B 3 and B 4 , apply formula (*) we have:
- For B 3 treatment (10ppm) we need: 200ml of Pb(NO 3 ) 2 x3 = 600ml/3treatments
- For B 4 treatment (15ppm) we need: 300ml of Pb(NO 3 ) 2 x3 900ml/3treatments
- Using rubber pipette 10ml to take Pb(NO 3 ) 2 standard stock solution and put into
12 plastic basins of samples follow the concentration above
The experiment involved a total of 12 plastic containers utilized for phytoremediation, which was conducted in a static environment over a duration of 20 days Observations were made at intervals of 5, 10, 15, and 20 days to assess the effectiveness of the process.
Observation for 5 day; 10 day; 15 day; 20 day
Procedures required in observation plant samples before destruction and analyzing include following steps:
- In each plastic container, take 55 gram of Najas indica plant samples and put in glass plates Total: 12 samples
- Put all of plant samples in incubator to dry them and wait for 24 hours
To prepare water samples for pH measurement, take 50ml of water in each treatment plastic basin using a volumetric pipette and transfer it to a glass bottle Measure the pH of the samples with a pH meter To preserve the pH until analysis, add two drops of 65% HNO3 to three control treatment bottles (B1 concentration) and one drop of HNO3 to the remaining bottles.
After observation process and preparing for destruction, destruction sample progress requires all steps below:
- Take all Najas indica samples out of incubator oven and cut it into small pieces and measure 2 grams of Najas indica dry-small pieces in each treatment sample and
- Add 25ml of distilled water in each flask and shake it
To safely dry the solutions, add 5ml of 65% Nitric acid (HNO3) to each flask and place all sample flasks on hot plates Ensure this process is conducted in a fume hood to prevent exposure to toxic gases released during the drying of the HNO3 solution.
- Waiting for one hour Watch and shake the sample flasks during waiting time to make it be puree compound
Once the samples in the flask have transformed into a puree compound and the solution volume is approximately 10ml, carefully remove the flask from the hot plates and fume hood, then allow it to cool down.
To filter the compound consisting of dry small pieces of Najas indica plant, distilled water, and 65% nitric acid, utilize Whatman filter paper along with a vacuum filtration system Essential tools for this process include Erlenmeyer bottles and a glass funnel (refer to Figure 4).
Figure 4 Vacuum filtered machine and set of tools
To prepare a 50ml solution, use a volumetric pipette to add distilled water to the liquid sample obtained from the previous step, and transfer the mixture into a pre-prepared 100ml bottle.
- Last step is writing and labeling on each bottle, write the number of observation day to distinguish among different observations
- For control treatment (0 ppm), we add 25ml of distilled water For other treatments that contain Pb, we add 50ml of distilled water
Process analysis of heavy metal content in plants
Analysis Pb content using SNI reference 06-6992.3-2004 - Sediment Part 3: Test methods of lead (Pb) with acid destruction by Atomic Absorption Spectrophotometer (AAS) (Figure 5)
Process of data analysis of heavy metal content of Pb dissolved in water
Analysis of Pb concentration in accordance with the procedure SNI 6989.8.2009 - Water and waste-water Part 8: Test methods of lead (Pb) by flame- Atomic Absorption Spectrophotometer (AAS) (Figure 5)
Data was gotten after analyzing had processed by using:
Statistic: One-way ANOVA to identify the significantly different effect of Pb(NO 3 ) 2 concentration in each of 4 treatments to Pb concentration in water and in Najas Indica
Time series analysis: Predict the changing trend of Pb concentration in water and also in Najas Indica plant in upcoming time if the experiment still continues.
RESULTS
Pb concentration in plant
- The results of Pb concentration in Najas indica plant after analyzing by Atomic Absorption Spectrophotometer (AAS) for 5 sampling times ( day 0, day 5, day
10, day 15 and day 20) were presented in table 3:
Table 3 Pb concentration in Najas indica plant
Table 3 shows the Pb concentration in Najas indica plant, in the first sampling time - day 0, sample plants already have Pb content inside their body with the average
Pb concentration of 3 replications are: 13.38 ppm for treatment B1, 23.41 ppm for treatment B2, treatment B3 is 37.13 ppm and last one, treatment B4 is 17.09 pmm
The data in day 5 indicated the significant increasing of Pb concentration in Najas indica plant went up to 84.56 ppm of B1, while treatment B2 is 2765.86 ppm, B3 is 1438.07 ppm and B4 is 2690.99 ppm.
On day 20, the data for treatment B3 and B4 is marked as not available (N.A) due to the absence of plant samples for destruction and analysis, as all samples were utilized in the previous treatment.
Figure 7: Mean of Pb concentration in plant
The data presented in Figure 7 indicates a consistent increase in lead (Pb) concentration within the Najas indica plant over the observation period Notably, the highest Pb concentration recorded was in treatment B4 on day 15, reaching an impressive 25,267.18 ppm In comparison, the Pb concentration in the surrounding water for the same treatment was significantly lower, peaking at only 9.47 ppm Overall, both Table 3 and Figure 7 illustrate that the Pb concentration in the plant is substantially greater than that in the surrounding water.
Results of Data analysis
• Changing trend of Pb concentration in water
The mean Pb concentration in water across four treatments was analyzed using time series analysis, revealing the changing trend predictions for treatments B2, B3, and B4, while treatment B1 showed an approximate Pb content of zero, as illustrated in Figures 8, 9, and 10.
Figure 8: Pb concentration in B2 treatment (mean) for water
The Pb concentration prediction data shows fluctuations until the 45th day, after which the levels stabilize, remaining consistently between 1 ppm and 1.2 ppm.
Figure 9: Pb concentration in B3 treatment (mean) for water
Figure 9 illustrates the variations in Pb concentration throughout the experiment, concluding with prediction data beyond day 20 The forecast indicates that Pb levels will remain stable, fluctuating between 3.1 ppm and 3.2 ppm in the subsequent days.
Figure 10: Pb concentration in B4 treatment (mean) for water
Treatment B4 exhibited the highest concentration of Pb in water compared to other treatments, as shown in figure 10 While it followed a similar fluctuation trend as the other treatments, the most notable aspect of treatment B4 is its distinct range over the observed days.
5 to day 15, Pb concentration increased to the highest level of Pb concentration in day
The experiment observed a concentration of 9.47 ppm on day 5, which decreased to 3.14 ppm by day 15 By day 20, the final observation day, the concentration rose again to 5.71 ppm Following this, the predicted concentration remained stable, fluctuating only slightly between 5.6 ppm and 5.7 ppm in the subsequent days.
• Changing trend of Pb concentration in Najas indica
The analysis of mean lead (Pb) concentration in plants across four treatments indicates significant trends, particularly in treatments B1 and B2, as illustrated in Figures 11 and 12 Unfortunately, data for treatments B3 and B4 are unavailable.
Figure 11: Pb concentration in treatment B1for plant (mean)
Figure 11 illustrates that the Pb concentration in treatment B1 increases from day 0 to day 5 and again from day 10 to day 15, with a notable twofold decrease observed in the graph The predictive data indicates a stable Pb concentration after day 30, suggesting consistency in the following days.
Figure 12: Pb concentration in B2 treatment for plant (mean)
Figure 12 shows the increasing trend of Pb concentration in the experiment and after the experiment It only went down one time from day 15 to day 20
The study observed a general decline in lead (Pb) concentration in water from day 5 to day 15, attributed to the absorption of water and Pb by Najas indica plants for metabolic processes Following this initial decrease, Pb concentration experienced a slight increase towards the end of the experiment, ultimately stabilizing at a certain level This finding aligns with Pourrut et al (2011), who noted that excessive Pb concentrations in plant cells can lead to cell lysis and destruction.
This study focuses on the chemical substance lead (Pb) and its effects on plant cells When the cells of the Najas indica plant burst, a small amount of Pb is released back into the water, resulting in a slight increase in Pb concentration However, as the plant's cells are destroyed, their ability to absorb Pb diminishes, leading to a stabilization of Pb concentrations in the water.
Whereas, the fluctuation trend of Pb concentration in water decreased as the Pb concentration in plant increased
Najas indica demonstrates the ability to adapt to higher concentrations of lead (Pb) in its environment, as observed in the regrowth of its top after a certain period Newly formed plant cells initially absorb small amounts of Pb from the water until the lysis process occurs However, the limited number of new cells that develop are unable to absorb Pb as effectively as during the initial stages of the experiment.
A study by Ragini Singh et al (2009) on the lead bioaccumulation potential of the aquatic macrophyte Najas indica revealed significant findings regarding its antioxidant system The research showed that at a concentration of 100 µM, the percentage of lead (Pb) accumulation increased from 34% on day 1 to 68% on day 2, reaching 92% by day 4 The total lead accumulated in Najas indica was notably high, measuring 3554 µg g⁻¹ dry weight when exposed to varying concentrations of Pb(NO₃)₂ Additionally, visible toxicity symptoms, such as chlorosis and fragmentation of leaves accompanied by mucilaginous discharge, were observed at a concentration of 50 µM after four days.
If the lysis process does not take place, the plant cells will persist over the following days, leading to sustained Pb concentration in both water and plant tissues Once the plant cells reach their saturation limit, a saturation process will occur.
According to the results of Pb concentration in water and Pb concentration in plants has a large distance in scale unit For instance, in water, the highest number of
In treatment B 4-3, the Pb concentration measured 10.9 ppm on the 5th day, while in treatment B 4-2, it reached 26,693.5 ppm by the 15th day, highlighting the varying bioaccumulation coefficients of different metals According to Ilya Raskin et al (1997), these coefficients can range from several hundred for cationic species like arsenic to nearly 10,000 for lead and copper Furthermore, plants exhibit distinct bioaccumulation capabilities; for instance, Indian mustard (Brassica juncea) can accumulate lead from water concentrations of 20 to 2,000 g/L, with coefficients between 500 and 2,000, as noted by Salt et al (1997) Studies by Albers P.H et al (1993) and Vlatko K et al (2012) indicate that heavy metal concentrations in macrophyte tissue can be significantly higher—up to thousands of times—than in surrounding water Additionally, water pH plays a crucial role in heavy metal solubility, as explained by Bruce Averill and Patricia Eldredge in General Chemistry: Principles, Patterns, and Applications, v 1.0, where they state that a strong acid can greatly enhance the solubility of salts containing the conjugate base of weak acids.
Phytoremediation is an effective process that utilizes plants to remediate, degrade, or immobilize contaminants in soil and water, ultimately improving environmental quality This study focuses on Najas indica, a submerged aquatic plant, which has been shown to accumulate and remove lead (Pb) from polluted water The method is applicable for managing various toxic metals and radionuclides while minimizing environmental disturbance and eliminating secondary waste By investigating the absorption of lead nitrate (Pb(NO3)2) by Najas indica, this research aims to enhance water quality and contribute to sustainable water sources The findings demonstrate that Najas indica effectively bioaccumulates lead, showcasing its potential in phytoremediation efforts.
Phytoremediation is an eco-friendly and economical technology, yet it has limitations, particularly regarding the toxicity and accumulation of heavy metals Research on the Najas indica plant remains scarce and superficial, highlighting the need for further studies Continued investigation into the adsorption of heavy metals, especially lead (Pb), through Najas indica is essential for advancing our understanding of its potential in environmental remediation.
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