DSpace at VNU: Anthropogenic influence on surface water quality of the Nhue and Day sub-river systems in Vietnam

DSpace at VNU: Anthropogenic influence on surface water quality of the Nhue and Day sub-river systems in Vietnam tài liệ...

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O R I G I N A L P A P E R

Anthropogenic influence on surface water quality

of the Nhue and Day sub-river systems in Vietnam

Pham Thi Minh Hanh •Suthipong Sthiannopkao•

Kyoung-Woong Kim•Dang The Ba•

Nguyen Quang Hung

Received: 22 February 2009 / Accepted: 17 September 2009 / Published online: 6 October 2009

Ó Springer Science+Business Media B.V 2009

Abstract In order to investigate the temporal and

spatial variations of 14 physical and chemical surface

water parameters in the Nhue and Day sub-river

systems of Vietnam, surface water samples were

taken from 43 sampling sites during the dry and rainy

seasons in 2007 The results were statistically

exam-ined by Mann–Whitney U-test and hierarchical

cluster analysis The results show that water quality

of the Day River was significantly improved during

the rainy season while this was not the case of the

Nhue River However, the river water did not meet

the Vietnamese surface water quality standards for

dissolved oxygen (DO), biological oxygen demand

(BOD5), chemical oxygen demand (COD), nutrients,

total coliform, and fecal coliform This implies that the health of local communities using untreated river water for drinking purposes as well as irrigation of vegetables may be at risk Forty-three sampling sites were grouped into four main clusters on the basis of water quality characteristics with particular reference

to geographic location and land use and revealed the contamination levels from anthropogenic sources Keywords Mann–Whitney U-test

Cluster analysis Nhue and Day sub-river systems Water quality Spatial and seasonal variations

Introduction The Nhue and Day sub-river systems, located on the right bank of the Red River, have been considered an important water source for people in the area (agri-culture, aqua(agri-culture, small industry, water supply, etc.) The rivers also function as waterways, irrigation, drainage, and flood protection systems Urbanization

in this region is rapidly progressing, with annual population increase of about 5% (MONRE 2006), while the infrastructure is still incompatible with rapid development At present, the Nhue River is under great pressure due to socioeconomic development activities The establishment and operation of indus-trial zones, craft villages, factories, and agricultural areas have caused significant changes to the natural environment, especially to water quality In recent

Department of Environmental Science and Engineering,

Gwangju Institute of Science and Technology (GIST),

Gwangju 500-712, Korea

e-mail: kwkim@gist.ac.kr

International Environmental Research Center (IERC),

Gwangju Institute of Science and Technology (GIST),

Gwangju 500-712, Korea

e-mail: suthi@gist.ac.kr

D T Ba

College of Technology (COLTECH), Vietnam National

University, Hanoi, Vietnam

N Q Hung

Vietnam Academy of Science and Technology (VAST),

Hanoi, Vietnam

DOI 10.1007/s10653-009-9279-9

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as it is considered to be one of the most severely

polluted river systems in Vietnam (MONRE2006)

Few studies on water quality of the Nhue River

have been done, and they were mainly focused on the

impact of wastewater from the capital Hanoi’s

drain-age system, the To Lich River Treatment of water

from the To Lich River is strongly recommended;

otherwise, a reduction of current wastewater discharge

down to one-third is needed to bring water quality

back to the environmental standard (Duc et al.2006,

2007) Only one sampling point from the Nhue, at the

meeting point with the Red River, has been monitored

by the national surface water monitoring network

Systematic study of the water quality of the whole

sub-river system, however, has not yet been done

As an initial step toward water resource

manage-ment in the Nhue and Day sub-river systems, this

study focused on evaluation and examination of the

temporal and spatial variability of water quality in the

whole river basin Sampling sites covered a wide

range of land-use purposes in the catchment area

(suburban, urban, and rural), main rivers, and

tribu-taries The obtained results are the first systematic

data showing the comprehensive water quality profile

of this river system in Vietnam The contaminant

concentrations were statistically compared with the

Vietnamese surface water quality standard TCVN

5942-1995 (MOSTE1995) to get the overall pattern

of water quality, and seasonal and spatial variations

of water quality were examined by Mann–Whitney

U-test and hierarchical cluster analysis

Methods

Study area and sampling sites

The catchment area of the sub-river system covers

7,665 km2of Ha Tay, Nam Dinh, Ha Nam, and Ninh

Binh Provinces and a part of the capital Hanoi and

Hoa Binh Province (MONRE 2006), with total

population of approximately 10 million people (based

on 2005 statistical data) (SPH2006) The Day River

is 237 km long, flowing through Ha Tay, Ha Nam,

Nam Dinh, and Ninh Binh Provinces and outflowing

to the sea at the Day River mouth After the

reconstruction of the Day Dam in 1937, the Day

River no longer receives water from the Red River

long, running through Ha Noi, Ha Tay, and Ha Nam Provinces As a tributary of the Red River, the Nhue River’s boundaries are the Lien Mac Dam (Tu Liem, Hanoi) to the north and a meeting point with the Day Diver at Phu Ly (Ha Nam) to the south The two rivers are connected by the La Khe and Van Dinh Rivers Untreated wastewater from the To Lich River, the main drainage system of Hanoi, discharges into the Nhue River at To Bridge (Fig 1) Agriculture is the dominant land use in the Day River basin The upstream part of the Nhue River with length of about

20 km mainly lies in the urban areas of Hanoi and Ha Dong (Ha Tay Province) cities The rest of the river is located in areas where agriculture is the predominant land use (Table 1) There are two main seasons of the year in this region: the rainy season (from June to October) and the dry season (from November to May) The rainy season contributes 70–80% of the total annual flow (MONRE 2006)

Samples were collected during the dry (February/ March 2007) and rainy seasons (July 2007) from a total of 43 sites in the Nhue and Day Rivers and their main tributaries In addition, samples from the Red River (3 km upstream of the confluence point of the Red River with the Nhue River) were also taken as a water quality reference (Fig.1)

Measurement of water quality parameters Water temperature (Tw), pH, dissolved oxygen (DO), and salinity (sal) were measured in situ by using a TOA model WQC-22A water quality checker Suspended solid (SS) was determined according to standard method number 2540 (APHA1998)

The water samples were collected in midstream at approximately 20–30 cm below the water surface Sample containers were rinsed three times with the water sample before sampling Samples were pre-served according to standard methods for the exami-nation of water and wastewater (APHA 1998) Analyses were carried out the same day as sample collection Blank samples were analyzed before and after analyzing the actual samples each day Duplicates were taken every five samples Ammonia–nitrogen (NH3-N), nitrate-nitrogen (NO3-N), nitrite-nitrogen (NO2-N), and orthophosphate-phosphorus (PO4-P) concentrations were measured by the reference method using a portable HACH spectrophotometer model

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DR/2000 Total phosphorus (TP-P) was defined after

converting to PO4 by oxidizing and decomposing

organic matter Orthophosphate concentration was

then quantified An ELE International portable incu-bator (Paqualab 50) was used for microbiological analysis [total coliform (T coli) and fecal coliform

Sampling sites

Red river site: R

N1 Lien Mac dam D1 Mai Linh bridge

N2 Co nhue D2 North of Ba Tha

N3 Dien bridge D3 Ba Tha

N4 Dong Bong 1 D4 Te Tieu bridge

N5 Doi bridge D5 Duc Khe bridge

N6 Ha Dong dam D6 Que Bridge

N7 Ta Thanh Oai D7 Thanh Son

N8 Dan Nhiem D8 Phu Van village

N9 Dong Quan dam D9 Hong Phu bridge

N10 Noi bridge D10 Doan Vi bridge

N11 Cong Than bridge D11 Ninh Khang

N12 Nhat Tuu dam D12 Ninh Binh city

N13 Do Kieu D13 Doc Bo

N14 Luong Co dam D14 Khanh Tien

N15 Phu Van bridge D15 Nghia Lac

D16 Tung Thien D17 Day river mouth

Tributaries

NT1 La Khe river DT1 Bui river

NT2 To Lich river (1) DT2 Van Dinh river

NT3 To Lich river (2) DT3 Thanh Ha river

NT4 Van Dinh river DT4 Hoang Long river

NT5 Chau Giang river DT5 Dao river

DT6 Vac river

N/A not available

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determined after 5 days of incubation in the dark at

20°C, and chemical oxygen demand (COD) analysis

followed standard method number 5220C (APHA

1998)

Statistical analysis

First, the normality of the distribution of the data sets

was tested by the Shapiro–Wilk test Data for few of

the parameters could be fitted to a normal distribution

with 95% confidence Therefore, nonparametric tests

were deemed more suitable than parametric tests,

as normality of the data could not be assumed (Ott

1988; Morgan et al 2007) The Mann–Whitney

U-test (MW-U) was performed in order to determine

whether there was a significant seasonal difference in

river water quality

Hierarchical cluster analysis (CA), which can be

employed for grouping either monitoring sites or

monitoring parameters, has been widely used in a

number of previous studies (Zou and Whittemore

1993; Chang 2005; Singh et al 2005; Panda et al

2006; Astel et al 2007; Mendiguchı´a et al 2007;

Kambe et al.2007; Kannel et al.2007; Shrestha and

Kazama2007) In order to obtain the groups of sites

that had similar water quality characteristics, cluster

analysis was applied in this study to classify all 43

sampling sites All statistical processes were

per-formed using SPSS (Statistical Package for Social

Sciences) 15.0 software for Windows

Overall patterns of water quality Table3summarizes the values of measured parameters

in the samples from the Nhue and Day Rivers The percentage of samples that did not meet the Vietnamese surface water quality standard for individual parame-ters is presented in Table2and Fig.2 The results show that the river system was contaminated with BOD5, COD, NO2-N, NH3-N, T coli, and F coli all year round The values of F coli from all the sampling sites (600–1,500,000 number/100 ml and 2,500–1,200,000 number/100 ml for the Nhue River and Day River, respectively) were much higher than the WHO standard (WHO1984) (absent/100 ml for drinking water) and Vietnamese standard TCVN6773-2000—water quality guidelines for irrigation (B200 number/100 ml for vegetable growing areas) Unfortunately, an important vegetable source for the capital Hanoi is watered directly with Nhue River water Along the Day River, local communities have been widely using contami-nated river water for washing and drinking purposes as well as irrigation of vegetables This suggests that long-term use of untreated river water for these purposes may pose health problems in the local population

Seasonal variations in surface water quality

of the Nhue River The MW-U test results revealed that, in general, there was no statistically significant difference in the

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concentrations of DO, BOD5, COD, NH3-N, PO4-P,

TP-P, T coli, and F coli in river water between the

two seasons (p \ 0.05) (Table3) These results may

provide evidence of critical anthropogenic impacts on

the Nhue River According to the agreement among

six provinces (Hanoi, Ha Tay, Hoa Binh, Ha Nam,

Nam Dinh, and Ninh Binh) since 2005, wastewater

from To Lich River could be discharged into the Nhue River only in the rainy season This explained why, even though the rainy season accounts for 70– 80% of total annual water flow, Nhue River water quality was not improved by this dilution effect This suggested that untreated wastewater (as displayed in Table 4) of approximately 500,000 m3/day (MONRE

Nhue river Day river Dry season Rainy season Dry season Rainy season

0.0 0.1 0.2 0.3 0.4 0.5

0 10 20 30 40 50 60 70

20 22 24 26 28 30 32 34 36

0 50 100 150 200 250 300 350

5 6 7 8 9

0 2 4 6 8 10 12 14

0.00 0.05 0.10 0.15 0.20 0.25 0.30

0 2 4 6 8 10 12

plots comparing seasonal

changes in water quality of

the Nhue and Day Rivers.

The boundaries of the box

indicate the 25th and 75th

percentiles, whiskers

indicate the 90th and 10th

percentiles The median and

mean are shown by a solid

and dotted line,

respectively Dash-dotted

line: TCVN5942-1995

level A

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2006) from To Lich River was the main reason for

the degradation in the Nhue River water quality This

agrees with the previous study by Duc et al (2006)

about the significant impact of To Lich River input

wastewater on the water quality of the Nhue River

The medians of SS, Tw, pH, and NO3-N of the

Nhue River water were significantly higher in the

rainy season than in the dry season (p \ 0.05) It was

obvious that the SS concentration of the Nhue River

was strongly affected by the Red River water, which

was much higher in the rainy/flood season The

concentration of SS of the Red River sample in this

study was 4.8 mg/l in the dry season and 160.5 mg/l

in the rainy season High temperatures in the rainy

season may be the main reason for the increase of the

NO3-N concentration This is due to the fact that

nitrification is favored under high temperatures On

the contrary, the median salinity and NO2-N were

higher in the dry season Lower concentration of

NO2-N during the rainy season may result from a higher rate of nitrification, as mentioned above Seasonal variations in surface water quality

of the Day River The comparison of water quality data between the dry and rainy seasons of the Day River is shown in Table 3 The results implied that values of pH, DO, sal, BOD5, PO4-P, TP-P, and T coli during the dry season were significantly higher than those for the rainy season (Fig.2) Because of the relatively smaller loads of untreated wastewater into the Day River, dilution effects during the rainy season resulted in a significant benefit in terms of improved water quality in this river The PO4-P and TP-P emissions from fertilizer and livestock feed into the

Nhue river Day river

Dry season Rainy season Dry season Rainy season

0 1 2 3 4 5 6

0 1 2 3 4 5 6 7

0 20 40 60

0 20 40 60 80 100

0.0 5.0e+5 1.0e+6 1.5e+6 2.0e+6 2.5e+6

0.0 2.0e+5 4.0e+5 6.0e+5 8.0e+5 1.0e+6 1.2e+6 1.4e+6 1.6e+6

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Table

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watershed during the rainy season were insignificant

because residual phosphate was able to form

rela-tively insoluble forms with many cations

(Environ-ment Canada2004)

Similar to in the Nhue River, median

concentra-tions of SS, Tw, and NO3-N in the Day River were

significantly higher in the rainy season (p \ 0.05)

However, no significant differences between the

median COD, NO2-N, NH3-N, and F coli levels for

the two seasons were found (Table3) This may be

explained by surface runoff that can carry

contam-inants directly into the river during the rainy season

The Day River basin is dominated by agricultural

activities, especially along the river banks (Table1)

It is documented that runoff from agricultural land is

an important source of nitrogen pollution in many

catchments (Carpenter et al 1998; Li et al 2009)

Outdoor livestock grazing and cattle and human

excreta application in agricultural were likely the

source of F coli for the Day River In addition, high

temperatures during the rainy season may have provided favorable conditions for F coli

Anthropogenic input and spatial variations

in surface water quality of the Nhue and Day sub-river systems

The relationship among the sampling sites is shown

in Fig.3; four main clusters were identified from the cluster analysis

Cluster 1, the so-called relatively clean group, includes five upstream sites of the Nhue River (N1 to N5), three downstream sites (N12, N14, and N15), Chau Giang River (a Nhue tributary), almost all sites

of the Day River (D1 to D15), and all Day River tributaries (DT1 to DT6) Cluster 1 can be further divided into two subclusters (see the sampling sites in Fig.1) Cluster 1a is formed by N1 to N5—upstream sites of the Nhue River, about 6 km after receiving the Red River water; D12 to D15—downstream sites

season

TCVN 5942-1995 level A

TCVN 5945-1995 industrial wastewater discharge standards

TCVN 5942-1995

Level A Surface water quality standard for water supply

TCVN 5945-1995

Level A Industrial wastewater can be discharged into water bodies used for sources of domestic water supply

Level B Industrial wastewater can be discharged only into water bodies used for navigation, irrigation purposes or for bathing, aquatic breeding, cultivation, etc.

Level C Industrial wastewater can be discharged only into specific water bodies permitted by authority agencies

Industrial wastewater with concentrations of substances that are greater than those specified in level C should not be discharged into surroundings

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of the Day River; DT5—the Dao River, the main

tributary of the Red River; and DT6—the Vac River

These sites lie in rural areas or far from municipal,

industrial pollution sources Cluster 1b is not as clean

as cluster 1a, formed by four sampling sites from the

Nhue River and its tributary (N12, N14, N15, NT5)

and another 15 sites from the Day River (D1 to D11)

and its four tributaries (DT1 to DT4) Water quality

of the downstream sites (N12, N14, and N15) of the

Nhue River was better than that of the middle part

(cluster 3) of the river because of self-purification

processes The Day River and its tributaries sites in

this subcluster pass through areas of low or medium

industrial development and residential housing

Cluster 2, the so-called river mouth group, consists

of two sites (D16 and D17) This group is closely related with cluster 1, as shown by a short cluster separation However, it has typical river mouth water characteristics with high salinity concentration, and this may explain why these sites form a distinct unit cluster

There are ten sampling sites grouped into the cluster 3, the contamination source group of Nhue River These are all from the Nhue River system, N6 to N11, N13 and the Van Dinh River—a Nhue tributary—and these sites likely correspond to point pollution sources This part of the Nhue River lies in the urban/suburban areas of Hanoi and Ha Dong Cities with a significantly high population and rapid development of industry It is to be noted that there

is self-purification of the Nhue River as it flows downstream Station N13 is located in a part of the river where it receives wastewater from the indus-trial zone of Dong Van and Ha Nam Therefore, these localized conditions at site N13 may impart different water quality characteristics that those observed in cluster 1b (containing sites N12, N14, and N15)

Cluster 4, the so-called extreme contamination sites, has only one site, located in the To Lich River (NT2), the Nhue’s tributary, and which also serves as the main drainage of the capital Hanoi This cluster corresponds to a critical contamination site within the system and should be considered as an outlier (as further demonstrated by the long cluster separation)

Conclusion Obtained data show that the Nhue and Day River systems were contaminated by BOD5, COD, NO2-N,

NH3-N, T coli, and F coli all year round Using untreated river water for domestic purposes as well as irrigation of vegetables may pose a serious health problem to the local community For the Day River, water quality was improved during the rainy season compared with in the dry season for a number of water quality parameters such as BOD5, PO4-P, TP-P, and T coli Water runoff, especially from agriculture areas, during the rainy season had a significant impact

on the river water quality The dilution factor was not effective in improving the water quality of the Nhue River Untreated wastewater from the To Lich River

the Nhue and Day sub-river systems

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water quality.

Cluster analysis classified four different groups of

sampling sites based on anthropogenic inputs and

water characteristics This classification can be

considered as a suggestion for implementing optimal

river monitoring nets and making a priority of water

resource management for the Nhue and Day sub-river

systems In addition, the impact of land-use type on

water quality in both rivers was indicated

International Environmental Research Center (IERC), Gwangju

Institute of Science and Technology (GIST), Korea, for financial

support The authors would also like to thank Dr Kenneth

Widmer (IERC) for comments and editorial suggestions in the

preparation of this manuscript.

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