Identification of anthropogenic influences on water quality of rivers in Taihu watershed

Evaluating long-term impacts of land use/land cover changes on pollution loads at a catchment scale

Evaluating how pollutant loads react to changes in land use/land cover (LULC) is a challenging task due to the intricate relationships among the many elements within a watershed. However, the difficulty in connecting LULC change and nonpoint source (NPS) pollution loads to streams may be lessened by combining hydrological modeling with geospatial tools and multivariate statistics. The objective of this study was to investigate the long-term effects of LULC change on NPS pollution loads in a highly human-dominated catchment, in central Ethiopia. In the study, hydrologic modeling was used to estimate the NPS parameters from multispectral Landsat images, and multivariate statistical techniques were then used to extract major LULC types that explain the variances of NPS loads between 1981 and 2020. The results demonstrated that there were human-induced LULC changes in the area, as the built-up and agricultural landscapes are rising (186.4% and 5.8%, respectively), and shrub and forest lands are decreasing (67.1% and 41%, respectively). As a result of these changes, the concentrations of nitrate (NO3), total P, total N, organic N, and organic P loads were increased by 69.41, 19.83, 18.45, 18.88, and 24.05%, respectively. Reductions in natural vegetation, as well as agriculture intensification, are the major contributors to the NPS pollutant losses to surface water sources. The result also revealed that pollution nutrients are strongly related to deforestation and agricultural land expansion. Proper adaptation strategies should be implemented to minimize the negative impact of LULC changes in the area.

Response of coastal phytoplankton to pollution from various sources in the coastal Bay of Bengal

The coastal ocean receives nutrient pollutants from various sources, such as aerosols, municipal sewage, industrial effluents and groundwater discharge, with variable concentrations and stoichiometric ratios. The objective of this study is to examine the response of phytoplankton to these pollutants in the coastal water under silicate-rich and silicate-poor coastal waters. In order to achieve this, a microcosm experiment was conducted by adding the pollutants from various sources to the coastal waters during November and January, when the water column physicochemical characteristics are different. Low salinity and high silicate concentration were observed during November due to the influence of river discharge contrasting to that observed during January. Among the various sources of pollutants used, aerosols and industrial effluents did not contribute silicate whereas groundwater and municipal sewage contained high concentrations of silicate along with nitrate and phosphate during both the study periods. During November, an increase in phytoplankton biomass was noticed in all pollutant-added samples, except municipal sewage, due to the limitation of growth by nitrate. On the other hand, an increase in biomass and abundance of phytoplankton was observed in all pollutant-added samples, except for aerosol, during January. Increase in phytoplankton abundance associated with decrease in biomass was observed in aerosol-added sample due to co-limitation of silicate and phosphate during January. A significant response of Thalassiothrix sp. was observed for industrial effluent-added sample during November, whereas Chaetoceros sp. and Skeletonema sp. increased significantly during January. Higher increase in phytoplankton biomass was observed during November associated with higher availability of silicate in the coastal waters in January. Interestingly, an increase in the contribution of dinoflagellates was observed during January associated with low silicate in the coastal waters, suggesting that the concentration of silicate in the coastal waters determines the response of the phytoplankton group to pollutant inputs. This study suggested that silicate concentration in the coastal waters must be considered, in addition to the coastal currents, while computing dilution factors for the release of pollutants to the coastal ocean to avoid occurrence of unwanted phytoplankton blooms.

The multiscale nexus among land use-land cover changes and water quality in the Suquía River Basin, a semi-arid region of Argentina

Agricultural intensification and urban sprawl have led to significant alterations in riverscapes, and one of the critical consequences is the deterioration of water quality with significant implications for public health. Therefore, the objectives of this study were the assessment of the water quality of the Suquía River, the assessment of LULC change at different spatial scales, and the analysis of the potential seasonal correlation among LULC change and Water Quality Index (WQI). The Sample Sites (SS) 1 and 2 before Cordoba city had the highest WQI values while from SS3 the WQI decreased, with the lowest WQI close to the wastewater treatment plant (SS7) after Cordoba city. From SS8 in a agricultural context, the WQI increases but does not reach the original values. In light of analysis carried out, the correlation between water quality variables and the different LULC classes at the local and regional scales demonstrated that WQI is negatively affected by agricultural and urban activities, while natural classes impacted positively. The spatialization of the results can help strongly in assessing and managing the diffusion of point and non-point pollution along the riverscape. The knowledge gained from this research can play a crucial role in water resources management, which supports the provision of river ecosystem services essential for the well-being of local populations.

Spatio-temporal variation in water quality and phytoplankton community structure in Changwang, Meishe, and Wuyuan Rivers in Hainan Island, China

For the first time, this study explored spatio-temporal variation in water quality and phytoplankton community structure in Changwang, Meishe, and Wuyuan Rivers in tropical Hainan Island, China. Phytoplankton samples and water were collected between March and December 2019 and analyzed using standard methods. Two-way ANOVA revealed significant spatial and seasonal variation in physico-chemical parameters (p < 0.05). Wuyuan had high TP (0.06 ± 0.04 mg L^-1), TN (1.14 ± 0.71 mg L^-1), NH₄⁺-N (0.07 ± 0.09 mg L^-1), Secchi depth (2.28 ± 3.79 m), salinity (3.60±5.50 ppt), and EC (332.50 ± 219.10 µS cm^-1). At the same time, Meishe had high TP (0.07 ± 0.03 mg L^-1), TN (1.04 ± 0.74 mg L^-1), NH₄⁺-N (0.07 ± 0.10 mg L^-1), EC (327.61 ± 63.22 µS cm^-1), and turbidity (40.25 ± 21.16 NTU). In terms of seasons, spring recorded high average TP, TN, NH₄⁺-N, COD, and DO, while summer had a high temperature, Chl-a, salinity, and EC. Generally, the physico-chemical parameters met the China water quality standard limits (GB 3838-2002). Overall, 197 phytoplankton species belonging to Cyanophyta, Chlorophyta, Cryptophyta, Bacillariophyta, Pyrrophyta, Euglenophyta, Xanthophyta, and Chrysophyta were identified, with Cyanophyta being dominant. Phytoplankton density showed spatial changes varying from 18 × 10⁶ cell L^-1 to 84 × 10⁶ cell L^-1. The phytoplankton diversity ranged from 1.86 to 2.41, indicating a mesotrophic state. One-way ANOSIM showed no significant spatial dissimilarity in phytoplankton composition (R = 0.042, p = 0.771) but indicated a significant seasonal difference (R = 0.265, p = 0.001). Therefore, SIMPER analysis revealed that Lyngbya attenuata, Merismopedia tenuissima, Cyclotella sp., Merismopedia glauca, Merismopedia elegans, and Phormidium tenue contributed to the seasonal differences. Furthermore, CCA demonstrated that TP, TN, NH₄⁺-N, COD, Chl-a, and Secchi depth greatly influenced the phytoplankton community. This study shows the spatio-temporal variation in water quality and phytoplankton communities, useful for managing riverine quality.

Major ion compositions, sources and risk assessment of karst stream under the influence of anthropogenic activities, Guizhou Province, Southwest China

To explore the influence of different types of anthropogenic activity on the rivers, we investigate the major ion composition, sources and risk assessment of the karst stream (Youyu stream and Jinzhong stream), which are heavily influenced by mining activities and urban sewage, respectively. The chemical compositions of the Youyu stream water, which is heavily influenced by mining activities, are dominated by Ca²⁺ and SO₄^2-. However, the chemical compositions of the Jinzhong stream water, which is heavily influenced by urban sewage, are dominated by Ca²⁺ and HCO₃^-. The Ca²⁺, Mg²⁺ and HCO₃^- in Jinzhong stream are mainly derived from rock weathering, while the Youyu stream is affected by acid mine drainage, and sulfuric acid is involved in the weathering process. Ion sources analysis indicates that the Na⁺, K⁺, NO₃^-, and Cl^- in the Jinzhong stream mainly derive from urban sewage discharge; but NO₃^- and Cl^- of the Youyu stream mainly derive from agricultural activities, and Na⁺, K⁺ are mainly from natural sources. The element ratios analysis indicates the ratio of SO₄^2-/Mg²⁺ in Youyu stream (4.61) polluted by coal mine is much higher than that in Jinzhong stream (1.29), and the ratio of (Na⁺+K⁺+Cl^-)/Mg²⁺ in Jinzhong stream (1.81) polluted by urban sewage is higher than Youyu stream (0.64). Moreover, the ratios of NO₃^-/Na⁺, NO₃^-/K⁺, and NO₃^-/Cl^- in the agriculturally polluted Youyu stream were higher than those in the Jinzhong stream. We can identify the impact of human activities on streams by ion ratios (SO₄^2-/Mg²⁺, (Na⁺+K⁺+Cl^-)/Mg²⁺, NO₃^-/Na⁺, NO₃^-/K⁺, and NO₃^-/Cl^-). The health risk assessment shows the HQ_T and HQ_N for children and adults are higher in Jinzhong stream than in Youyu stream and the total HQ value (HQ_T) of children was higher than one at J1 in the Jinzhong stream, which shows that children in Jinzhong stream basin are threatened by non-carcinogenic pollutants. Each HQ value of F^- and NO₃^- for children was higher than 0.1 in the tributaries into Aha Lake, indicating that the children may also be potentially endangered.

Unraveling the response of water quality and microbial community to lake water backflowing in one typical estuary of Lake Taihu, China

To investigate the effect of lake water backflowing on the aquatic ecosystem in the estuary, surface water samples in the backflowing and unbackflowing areas were collected from one typical estuary of Lake Taihu, Xitiaoxi River. 16S rRNA sequencing and redundancy analysis were conducted to quantitatively elucidate the correlation between microbial community and water quality parameters. Results indicated lake water backflowing would affect the relative distribution of nitrogen species and increase the concentration of total nitrogen (TN) and nitrate, especially in the outlets of municipal sewage and agricultural drainage. For backflowing areas, more frequent water exchange could lower the seasonal fluctuation of the abundance and diversity of microbial community. RDA results showed crucial water quality parameters that greatly influence bacterial community were total organic carbon (TOC), total dissolved solids (TDS), salinity (SAL), ammonia, nitrate, TN for backflowing areas, and TOC, TDS, SAL, ammonia, TN without nitrate for unbackflowing areas. Verrucomicrobia, Proteobacteria, Microcystis, and Arcobacter were dominant with 27.7%, 15.7%, 30.5%, and 25.7% contribution to the overall water quality in backflowing areas. Chloroflexi, Verrucomicrobia, Flavobacterium, and Nostocaceae were dominant with 25.0%, 18.4%, 22.3%, and 11.4% contribution to the overall water quality in unbackflowing areas. And lake water backflowing might mainly affect the amino acid and carbohydrate metabolism based on the metabolism function prediction. A better understanding of the spatiotemporal changes in water quality parameters and microbial community was obtained from this research to comprehensively assess the effect of lake water backflowing on the estuarine ecosystem.

Identification of pollutant sources and evaluation of water quality improvement alternatives of a large river

While pollutants are the most important factors for the deterioration of surface water quality, the identification of major pollutant sources for rivers is challenging, especially in areas with diverse land covers and multiple pollutant inputs. This study aims to identify the significant pollutant sources from the tributaries that are affecting the water quality and identify the limiting nutrient for algal growth in the Geum river to provide a management alternative for an improvement of the water quality. The positive matrix factorization (PMF) was applied for pollutant source identification and apportionment of the two major tributaries, Gab-cheon and Miho-cheon. Positive matrix factorization identifies three and two major pollutant sources for Gab-cheon and Miho-cheon, respectively. For Gab-cheon, wastewater treatment plants, urban, and agricultural pollution are identified as major pollutant sources. Furthermore, for Miho-cheon, agricultural and urban pollution were identified as major pollutant sources. Total phosphorus (TP) is also identified as a limiting nutrient for algal growth in the Geum river. Water quality control scenarios were formulated and improvement of water quality in the river locations was simulated and analyzed with the Environmental Fluid Dynamic Code (EFDC). Scenario results were evaluated using a water quality index. The reduction of total phosphorus (TP) from the tributaries has greatly improved the water quality, especially algal bloom in the downstream stations.

Hydrogeochemical characterization based water resources vulnerability assessment in India's first Ramsar site of Chilka lake

A limnological site is significantly characterized by rich biological, chemical, and physical properties of the environment and is also described as the epitome of a large aquatic ecosystem. During the last few decades, the Chilka lake Ramsar site has experienced substantial degradation of water quality with associated deterioration of aquatic biodiversity. Our study aims to quantify the VWRM of the Chilka lake Ramsar region using the most reliable MLAs, namely ANN and RF, with the help of seventeen hydro-chemical properties of lake water. The produced map is validated through six validating measures (ROC-AUC- 0.89, Sensitivity-0.90, Specificity-0.78, PPV-0.78, NPV-0.88, Taylor diagram (r)-0.94), which depict that ANN is the most reliable ML algorithm in assessing the VWRM of the concerned region followed by RF. The prepared map of our study revealed that the eastern part was remarkably high to very high vulnerable zone covered area with 22.41 % and 7.19 %, respectively.

Diversity and abundance of antibiotic resistance genes and their relationship with nutrients and land use of the inflow rivers of Taihu Lake

Taihu Lake is the third largest freshwater lake in China and an important source for drinking water, flood protection, aquaculture, agriculture, and other activities. This lake is connected to many principal and small rivers with inflow from west and outflow on the eastern side of the lake and these inflow rivers are believed to significantly contribute to the water pollution of the lake. This study was aimed at assessing the diversity and abundance of antibiotic resistance genes (ARGs) and mobile genetic elements (MGEs), and their relationship with water quality parameters and land use patterns. Water samples were collected from 10 major inflow rivers and the source water protection area of the Taihu Lake in spring and summer 2019. High-throughput profiling was used to detect and quantify 384 ARGs and MGEs and in addition, 11 water quality parameters were analyzed. The results showed that the number of ARGs/MGEs detected in each inflow river ranged from 105 to 185 in spring and 107 to 180 in summer. The aminoglycoside resistance genes were the most dominant types ARGs detected followed by beta-lactam resistance, multidrug resistance, macrolide-lincosamide-streptogramin B (MLSB) resistance genes, which contributed to 65% of the ARGs. The water quality parameters showed significant correlation with absolute abundance of ARGs. Furthermore, significant correlation between ARGs and MGEs were also observed which demonstrates potential gene transfer among organisms through horizontal gene transfer via MGEs. ARGs showed strong positive correlation with cultivated and industrial lands whereas, negative correlation was observed with river, lake, forest, land for green buffer, and land for port and harbor. The overall results indicate that the inflow rivers of Taihu Lake are polluted by various sources including multiple nutrients and high abundance of ARGs, which needs attention for better management of the inflow rivers of this lake.

Spatiotemporal correlations between water quality and microbial community of typical inflow river into Taihu Lake, China

Changxing River, which is a typical inflow river into Taihu Lake and occurs severe algae invasion, is selected to study the effect of different pollution sources on the water quality and ecological system. Four types of pollution sources, including the estuary of Taihu Lake, discharge outlets of urban wastewater treatment plants, stormwater outlets, and nonpoint source agricultural drainage areas, were chosen, and next-generation sequencing and multivariate statistical analyses were used to characterize the microbial communities and reveal their relationship with water physicochemical properties. The results showed that ammonia nitrogen (NH₄⁺-N), total nitrogen (TN), and total phosphorus (TP) were the main pollutants in Changxing River, especially at stormwater outlets. At the same time, the diversity of microbial communities was the highest in the summer, and dominant microbes included Proteobacteria (40.9%), Bacteroidetes (21.0%), and Euryarchaeota (6.1%). The results of BIOENV analysis showed that the major seasonal differences in the diversity of microbial community of Changxing river were explained by the combination of water temperature (T), air pressure (P), TP, and COD_Mn. From the perspective of different pollution types, relative abundances of Microcystis and Nostocaceae at the estuary of Taihu Lake were correlated positively with dissolved oxygen (DO) and pH, and relative abundances of Pseudomonas and Arcobacter were correlated positively with concentrations of TN and nitrate nitrogen (NO₃^--N) at stormwater outlets. This study provided a reference for the impact of pollution types on river microbial ecosystem under complex hydrological conditions and guidance for the selection of restoration techniques for polluted rivers entering the important lake.

Biochemical and histopathological effects in muscular tissue of carp fish (Labeo rohita, Hamilton 1822) following exposure to untreated and treated sewage water

Present work describes a laboratory study aiming at assessing the impact of sewage treatment plant (STP) effluents on fish health by means of biochemical and histopathological biomarkers in muscular tissue of fish. Labeo rohita (7.62 ±0.25 cm, 8.25±0.32 g) was exposed to sub-lethal concentrations of untreated (UT) and treated (T) sewage water obtained from STP, Ludhiana, India. Following the determination of the 96h lethal concentration (LC₅₀), the fish were exposed to control (de-chlorinated tap water), treated sewage water, 1/10^th of LC₅₀ UT and 1/20^th of LC₅₀ UT sewage water. The experiment was conducted for the period of 60 days. Experimental results depicted significant reduction (p<0.05) in muscle-somatic index of 1/10^th LC₅₀ UT and 1/20^th LC₅₀ UT groups compared to control and treated groups. Fish toxicity induced by untreated sewage water was evident from the significant decrease (p<0.05) in the levels of proteins and significant increase (p<0.05) in content of total lipids in muscular tissue of exposed group fingerlings. Drastic changes in the fatty acids profile and severe histological abnormalities viz. shortening of muscle bundles, edema, hyper-vacuolization, elongation of muscle bundles, gap formation in myofibrils, degenerated myotomes, hemorrhage, inter-myofibrillar space, necrosis, were also recorded in muscular tissue of exposed fingerlings. The intensity of muscular damage in L.rohita was found to increase with increase in duration of exposure. Results demonstrated that untreated sewage water could potentially induce physiological stress and somatic cell toxicity in fish L.rohita. Genotoxicity studies on germ cells of L.rohita fingerlings are further suggested to examine the genotoxic potential of untreated sewage water at high concentrations; this is especially of interest given that many effluents are genotoxic to fish.

Spatial Distribution Characteristics and Risk Assessment of Nutrient Elements and Heavy Metals in the Ganjiang River Basin

The pollution of water bodies by nutrients and heavy metals can lead to a loss of biodiversity, environmental degradation, and harm to human health. During the two-month monitoring period (e.g., December 2019 to January 2020), variables such as trace metals (e.g., Cu, Zn, As, and Cr), nutrients (e.g., NH4+-N, TN, and TP), water temperature, pH value, dissolved oxygen (DO), chemical oxygen demand (COD) and five-day biochemical oxygen demand (BOD5) were measured at 102 monitoring points in the main stream and tributaries of the Ganjiang River in the Poyang Lake Basin. A variety of multivariate statistical techniques, including cluster analysis (CA), principal component analysis (PCA), and correlation analysis, were used to conduct risk assessments and source analyses of the nutrient elements and heavy metals in the Ganjiang River system. The results show that although the Ganjiang River Basin is polluted by human activities, its water chemistry characteristics and trace metal and nutrient elements concentrations were better than the national standards. Through principal component analysis, the water pollution sources could be divided into urban sewage, agricultural activities, industrial activities, and the sources of industrial activities and transportation activities. The comprehensive risks of noncarcinogens (Hc) and comprehensive risks of carcinogens (Rc) for adults and children due to drinking water indicated that the risk from drinking water for the children in the basin was greater than that for adults, and that the Hc for adults and children was acceptable. However, the Rc for adults and children was slightly higher than the acceptable values. This study provides a reference for the fine control of the environmental water pollution sources in the Ganjiang river basin and health risk assessments in the basin, which are of great significance for improving the environmental water quality standards in the river basin and for reducing the risk of carcinogenesis.

Characteristics of the Phytoplankton Community Structure and Water Quality Evaluation in Autumn in the Huaihe River (China)

As an important indicator of phytoplankton in water quality evaluation, the phytoplankton community structure is very sensitive to changes in water quality, and analyzing their community composition and function is of great significance for the ecological management and maintenance of watershed environments. To understand the environment and ecological status as well as reconstruct or restore a healthy aquatic ecosystem in the Huaihe River Basin in China, a comprehensive phytoplankton survey was conducted in the main stream and main tributaries of the Huaihe River in 2019. A total of 266 species or genera of phytoplankton were identified, mainly belonging to Bacillariophyta and Chlorophyta. The number of phytoplankton species upstream and downstream was higher than that in the middle. The results of phytoplankton biomass showed significant spatial differences in different river reaches (p < 0.05). The identified phytoplankton functional groups (FGs) were divided into 27 groups, including 16 representative functional groups (RFGs), followed by A, B, F, G, H1, J, K, L_M, L_O, M, MP, P, T, T_B, W_O and X2. The mean values of the Shannon-Wiener index and Margalef index were 2.47 and 2.50, respectively, showing that most of the water in the Huaihe River Basin was in a state of moderate nutritional status. The results of this study provided a reference for studying the composition and distribution of phytoplankton communities, nutrient status, and pollution levels in the Huaihe River Basin, as well as in other similar watersheds.

Evaluation of Seasonal and Spatial Variations in Water Quality and Identification of Potential Sources of Pollution Using Multivariate Statistical Techniques for Lake Hawassa Watershed, Ethiopia

The magnitude of pollution in Lake Hawassa has been exacerbated by population growth and economic development in the city of Hawassa, which is hydrologically closed and retains pollutants entering it. This study was therefore aimed at examining seasonal and spatial variations in the water quality of Lake Hawassa Watershed (LHW) and identifying possible sources of pollution using multivariate statistical techniques. Water and effluent samples from LHW were collected monthly for analysis of 19 physicochemical parameters during dry and wet seasons at 19 monitoring stations. Multivariate statistical techniques (MVST) were used to investigate the influences of an anthropogenic intervention on the physicochemical characteristics of water quality at monitoring stations. Through cluster analysis (CA), all 19 monitoring stations were spatially grouped into two statistically significant clusters for the dry and wet seasons based on pollution index, which were designated as moderately polluted (MP) and highly polluted (HP). According to the study results, rivers and Lake Hawassa were moderately polluted (MP), while point sources (industry, hospitals and hotels) were found to be highly polluted (HP). Discriminant analysis (DA) was used to identify the most critical parameters to study the spatial variations, and seven significant parameters were extracted (electrical conductivity (EC), dissolved oxygen (DO), chemical oxygen demand (COD), total nitrogen (TN), total phosphorous (TP), sodium ion (Na+), and potassium ion (K+) with the spatial variance to distinguish the pollution condition of the groups obtained using CA. Principal component analysis (PCA) was used to qualitatively determine the potential sources contributing to LHW pollution. In addition, three factors determining pollution levels during the dry and wet season were identified to explain 70.5% and 72.5% of the total variance, respectively. Various sources of pollution are prevalent in the LHW, including urban runoff, industrial discharges, diffused sources from agricultural land use, and livestock. A correlation matrix with seasonal variations was prepared for both seasons using physicochemical parameters. In conclusion, effective management of point and non-point source pollution is imperative to improve domestic, industrial, livestock, and agricultural runoff to reduce pollutants entering the Lake. In this regard, proper municipal and industrial wastewater treatment should be complemented, especially, by stringent management that requires a comprehensive application of technologies such as fertilizer management, ecological ditches, constructed wetlands, and buffer strips. Furthermore, application of indigenous aeration practices such as the use of drop structures at critical locations would help improve water quality in the lake watershed.

Synergy between Satellite Altimetry and Optical Water Quality Data towards Improved Estimation of Lakes Ecological Status

European countries are obligated to monitor and estimate ecological status of lakes under European Union Water Framework Directive (2000/60/EC) for sustainable lakes’ ecosystems in the future. In large and shallow lakes, physical, chemical, and biological water quality parameters are influenced by the high natural variability of water level, exceeding anthropogenic variability, and causing large uncertainty to the assessment of ecological status. Correction of metric values used for the assessment of ecological status for the effect of natural water level fluctuation reduces the signal-to-noise ratio in data and decreases the uncertainty of the status estimate. Here we have explored the potential to create synergy between optical and altimetry data for more accurate estimation of ecological status class of lakes. We have combined data from Sentinel-3 Synthetic Aperture Radar Altimeter and Cryosat-2 SAR Interferometric Radar Altimeter to derive water level estimations in order to apply corrections for chlorophyll a, phytoplankton biomass, and Secchi disc depth estimations from Sentinel-3 Ocean and Land Color Instrument data. Long-term in situ data was used to develop the methodology for the correction of water quality data for the effects of water level applicable on the satellite data. The study shows suitability and potential to combine optical and altimetry data to support in situ measurements and thereby support lake monitoring and management. Combination of two different types of satellite data from the continuous Copernicus program will advance the monitoring of lakes and improves the estimation of ecological status under European Union Water Framework Directive.

Decrease of both river flow and quality aggravates water crisis in North China: a typical example of the upper Yongding River watershed

Due to unevenly distributed water resources, semi-arid regions are particularly prone to severe water shortage and quality degradation. In this study, based on long-term hydrological database (1935-2015), and the latest available water quality data sets (2011-2016), we analyzed the water crisis and its driving forces in the upper Yongding River watershed, a typical water shortage area in North China. The results showed that human induced excessive water consumption is responsible for the significantly decreased river flow over the past eight decades. Although the capacity of the watershed wastewater treatment has improved, current water quality does not meet the requirements of the national water management goals, because of the excessive nitrogen and COD_Cr (chemical oxygen demand), which mainly come from the wastewater and feedlots discharge. Due to the decreased river flow, current Yongding River is unable to dilute and assimilate pollutions. The analysis of river pollutant load illustrated that more than 60 % of the nitrogen in the river water system is diverted for reservoir storage, and more than 50 % of the COD_Cr and TP are diverted for irrigation, thereby, increasing the risk of reservoirs eutrophication and threatening food safety. Besides, the high Cl^- (388.2 ± 322.5 mg/L) and SO₄^2- (470.6 ± 357.7 mg/L) imply that the upper river water are not suitable for drinking and irrigation purposes, and a potential risk of salinization if the river flow continues to decrease. We conclude that water resources over extraction and quality degradation are the main driving factors of the Yongding River water crisis.

Waste into rivers: a residual issue? The case of the UNESCO's site of the Quebrada De Humahuaca, NW Argentina

The Quebrada de Humahuaca in North West Argentina is a world heritage site listed by the UNESCO since 2003. As pollution is increasing dramatically, a pluridisciplinary, annual-long survey was conducted along the valley to determine dominant patterns in waste management and water quality. Along with the habit of discarding waste into the river, urbanizations have been identified as having a deep influence on the river water quality: iron together with maximum peaks of nitrite and nitrate are related with the anthropogenic activity at Humahuaca, whereas the concentrations of arsenic increase from north to south, with maximum peaks of up to 13.50 and 14.50 μg L^-1 measured during the rainy season at Maimará and Volcán, respectively. In this underdeveloped region, economic struggles and waste management customs revealed as major factors causing the environmental degradation. The inclusion in the UNESCO's sites list was insufficient in preserving this world heritage site. The approach discussed in this article suggests a straightforward analytical measurement of the river hydrochemical properties during the rainy season in arid/semi-arid regions with monsoonal regime, to assess the effects of waste dumping along watercourses. In addition to scientific evaluations, both public acceptance and the establishment of proper waste management infrastructure are fundamental to ensuring the preservation of human and environmental health.

Contrasting Water Quality Treatments Result in Structural and Functional Changes to Wetland Plant-Associated Microbial Communities in Lab-Scale Mesocosms

The impact of contrasting water quality treatments on wetland plant-associated microbial communities was investigated in this study using 12 lab-scale wetland mesocosms (subsurface flow design) planted with reed canary grass (Phalaris arundinacea) or water speedwell (Veronica anagallis-aquatica) over a 13-week period. Mesocosms received water collected from two sites along the Grand River (Ontario, Canada) designated as having either high or poor water quality according to Grand River Conservation Authority classifications. All mesocosms were established using sediment collected from the high water quality site and received water from this source pre-treatment. Resulting changes to microbial community structure were assessed using PCR-denaturing gel gradient electrophoresis (DGGE) on microbial 16S rDNA sequences extracted from rhizoplane, rhizosphere, and water samples before and after exposure to water quality treatments. Functional community changes were determined using Biolog™ EcoPlates which assess community-level carbon source utilization profiles. Wetland mesocosm removal of inorganic nutrients (N, P) and fecal coliforms was also determined, and compared among treatments. Treatment-specific effects were assessed using a repeated measures restricted maximum likelihood (REML) analysis. Structural and functional characteristics of rhizoplane microbial communities were significantly influenced by the interaction between plant species and water treatment (P = 0.04, P = 0.01). Plant species-specific effects were observed for rhizosphere structural diversity (P = 0.01) and wetland water community metabolic diversity (P = 0.03). The effect of water treatment alone was significant for structural diversity measurements in wetland water communities (P = 0.03). The effect of plant species, water quality treatment, and the interaction between the two is dependent on the microhabitat type (rhizoplane, rhizosphere, or water). Rhizoplane communities appear to be more sensitive to water quality-specific environmental changes and may be a good candidate for microbial community-based monitoring of wetland ecosystems.

Spatio-temporal Characterization Analysis and Water Quality Assessment of the South-to-North Water Diversion Project of China

In this article, a data matrix of 20 indicators (6960 observations) was obtained from 29 water quality monitoring stations of the Middle Route (MR) of the South-to-North Water Diversion Project of China (SNWDPC). Multivariate statistical techniques including analysis of variance (ANOVA), correlation analysis (CA), and principal component analysis (PCA) were applied to understand and identify the interrelationships between the different indicators and the most contributive sources of anthropogenic and natural impacts on water quality. The water quality index (WQI) was used to assess the classification and variation of water quality. The distributions of the indicators revealed that six heavy-metal indicators including arsenic (As), mercury (Hg), cadmium (Cd), chromium (Cr), selenium (Se), and lead (Pb) were within the Class I standard, while the As, Pb, and Cd displayed spatial variation. Moreover, some physicochemical indicators such as dissolved oxygen, 5-day biochemical oxygen demand (as BOD₅), and total phosphorus (TP) had spatio-temporal variability. The correlation analysis result demonstrated that As, Hg, Cd, Cr, Se, Pb, copper (Cu), and zinc (Zn) had high correlation coefficients. The PCA result extracted three principal components (PC) accounting for 82.67% of the total variance, while the first PC was indicative of the mixed sources of anthropogenic and natural contributions, the second and the third PCs were mainly controlled by human activities and natural sources, respectively. The calculation results of the WQI showed an excellent water quality of the MR of the SNWDPC where the values of the stations ranged from 10.49 to 17.93, while Hg was the key indicator to determine the WQI > 20 of six stations, which indicated that the Hg can be the main potential threat to water quality and human health in this project. The result suggests that special attention should be paid to the monitoring of Hg, and the investigation and supervision within the areas of high-density human activities in this project should be taken to control the impacts of urban and industrial production and risk sources on water quality.

Assessment of eutrophication and water quality in the estuarine area of Lake Wuli, Lake Taihu, China

Our study assessed the actual water situation in the estuarine area of Lake Wuli, Meiliang Bay, Lake Taihu, China, based on eutrophication levels and status of water quality using the trophic level index (TLI) and water quality index (WQI) methods. In the wet (August 2017) and dry (March 2018) seasons, 22 estuarine areas were tested at 69 sampling sites, which included lake and rivers. Five parameters-chlorophyll a (Chl-a), total phosphorus (TP), total nitrogen (TN), Secchi disk (SD) and permanganate index (COD_Mn)-were measured to calculate the TLI, and 15 parameters-temperature (T), pH, electrical conductivity (EC), dissolved oxygen (DO), total dissolved solids (TDS), TN, TP, ammonium (NH₄-N), nitrate (NO₃-N), nitrite (NO₂-N), COD_Mn, calcium (Ca²⁺), magnesium (Mg²⁺), chloride (Cl^-) and phosphate (PO₄-P)-were measured to calculate the WQI. The average TLI and WQI values in the wet season were 61.69 and 60.70, respectively, and the eutrophication level and water quality status were worse than that in the dry season (TLI: 57.40, WQI: 65.74). Significant differences were observed between three parts of Lake Wuli (West, Middle and East). Regardless of wet or dry season, East Wuli had worse eutrophication levels and water quality status than the other parts, whereas West Wuli showed less severe levels. DO, TN and COD_Mn used in the minimum WQI (WQI_min) were the most effective parameters in our study. WQI_min had stricter standards than WQI when analyzing water quality in the estuarine area of Wulihu. Factor analysis from principal component analysis (PCA) indicated that N might be the main factor affecting water quality of the most eastern sites in the wet season, and P may be the main factor in the dry season. Our results provide a valuable contribution to inform decision-making for the management of water environments by providing the actual water situation of the estuarine area of Lake Wuli.

Microbial Indicators and Environmental Relationships in the Umhlangane River, Durban, South Africa

The use of rivers for recreational and domestic practices makes it imperative to scrutinize the water quality circulating within surrounding communities. The complexity of biological, physical and chemical constituents in water is constantly evolving. This study evaluated various microbial and physico-chemical parameters in a polluted river system over a 12-month period. Apart from an increase in chemical pollutants, elevated levels of E. coli, total (TC) and faecal (FC) coliforms, and Shigella species could be attributed to faecal contamination entering the catchment. Canonical correspondence analysis revealed a strong relationship between FC, TC and temperature whereas moderate interactions was seen between total dissolved solids, electrical conductivity, TC and FC populations. Furthermore, close relationships between the bacterial and phage communities were also observed. The complex interactions of these physico-chemical and microbial indicators could be due to anthropogenic activities, changing climatic conditions and the excreta of infected and non-infected individuals entering the river. Assessing the complexity of aquatic ecosystems can aid in the development of novel, customizable, inexpensive water purification tools.

Abundant and Rare Bacterioplankton in Freshwater Lakes Subjected to Different Levels of Tourism Disturbances

Anthropogenic disturbances have a negative impact on lake ecosystems, such as water environmental degradation. Bacterioplankton communities are essential components in lakes and consist of a few abundant species and several rare taxa. However, little is known about the community diversity and composition of abundant and rare bacterioplankton subjected to different levels of anthropogenic disturbances. In this study, water samples were collected from twelve freshwater lakes located around the city of Nanjing, China. Both Illumina MiSeq sequencing and multivariate statistical analysis were employed to determine the bacterioplankton community composition and its relation to environmental variables. The results indicated that tourism disturbances (mostly sewage discharge and tourist activities) altered the community structure of both abundant and rare bacterioplankton by changing water physicochemical characteristics. Alpha diversity of both abundant and rare taxa did not differ among different anthropogenic disturbance lakes (p > 0.05). Rare bacterial taxa possessed higher alpha diversity than abundant taxa, though rare taxa occupied a tiny portion of abundance (4.5%). Redundancy analysis demonstrated that dissolved organic carbon (DOC) was the most significant correlation variable for constraining the variation of abundant taxa, whereas total phosphorus (TP), ammonium nitrogen (NH4+-N), and chlorophyll-a (Chl-a) were the most dominant environmental factors constraining the rare taxa, indicating abundant and rare taxa may have different ecological niches.

Decomposition of Wolffia arrhiza residues rapidly increases mineral nitrogen and decreases extractable phosphorus in acidic soils

While nutrient loads from anthropogenic sources upset aquatic ecosystem balance, Wolffia arrhiza (duckweed) has capacity to purge nutrient-rich water if continuously harvested. The nutrients accumulated in biomass have potential as soil fertility amendments. The objective of this study was to determine changes in release of nitrogen (N) and phosphorus (P), and the fate of P in soils after duckweed biomass amendment. An incubation experiment was conducted at 25 °C using three soils amended with proportions equivalent to 501, 1002 and 1503 mg N kg^-1 and 62, 124 and 186 mg P kg^-1. Soil samples were collected on 0, 3, 7, 14, 21, 28, 42 and 56 days, for ammonium-N, nitrate-N and extractable-P measurements. At the end of incubation, P pools were determined. At least 25 mg kg^-1 of ammonium-N was released on day 0, reaching a peak within the first 2 weeks. Nitrate- and mineral-N increased from 14 to 42 days, with a corresponding decrease in ammonium-N. Relatively fertile soil released more mineral-N at higher applied ratios of duckweed than the less fertile. About 10-80 mg kg^-1 of duckweed P was extractable on day 0 and amounts progressively declined over the incubation period. The combined percentage (0.5%) of tissue aluminium (Al) and iron (Fe) facilitated Al and Fe phosphate accumulation as the proportion of duckweed amendment increased. The results suggested that soil type and elemental composition of duckweed are important determinants for N and P release, and liming could improve P availability in soil.

Assessing river water quality using water quality index in Lake Taihu Basin, China

Lake Taihu Basin, one of the most developed regions in China, has received considerable attention due to its severe pollution. Our study provides a clear understanding of the water quality in the rivers of Lake Taihu Basin based on basin-scale monitoring and a water quality index (WQI) method. From September 2014 to January 2016, four samplings across four seasons were conducted at 96 sites along main rivers. Fifteen parameters, including water temperature, pH, dissolved oxygen (DO), conductivity, turbidity (tur), permanganate index (COD_Mn), total nitrogen, total phosphorus, ammonium (NH₄-N), nitrite, nitrate (NO₃-N), calcium, magnesium, chloride, and sulfate, were measured to calculate the WQI. The average WQI value during our study period was 59.33; consequently, the water quality was considered as generally "moderate". Significant differences in WQI values were detected among the 6 river systems, with better water quality in the Tiaoxi and Nanhe systems. The water quality presented distinct seasonal variation, with the highest WQI values in autumn, followed by spring and summer, and the lowest values in winter. The minimum WQI (WQI_min), which was developed based on a stepwise linear regression analysis, consisted of five parameters: NH₄-N, COD_Mn, NO₃-N, DO, and tur. The model exhibited excellent performance in representing the water quality in Lake Taihu Basin, especially when weights were fully considered. Our results are beneficial for water quality management and could be used for rapid and low-cost water quality evaluation in Lake Taihu Basin. Additionally, we suggest that weights of environmental parameters should be fully considered in water quality assessments when using the WQI_min method.

Long-term evaluation of water quality parameters of the Karoun River using a regression approach and the adaptive neuro-fuzzy inference system

This paper investigates chemical water quality parameters of the Karoun, the greatest and the most important river of Iran, during a 48-year period, from 1968 to 2015. Water discharge (Q) fluctuates between 191.1m³s^-1 and 1758.7m³s^-1, with a decreasing trend over the 48-year period. Except pH, other water quality parameters increased, significantly, so that the rate of increase for EC and TDS was 25.71μScm^-1y^-1 and 16.66mgl^-1y^-1, respectively. Moreover, SO₄^-2, HCO₃^-, Cl^-, Ca⁺², Mg⁺² and Na⁺ have increased by 0.116, 0.012, 0.151, 0.066, 0.052 and 0.168meql^-1y^-1, respectively. Result indicated that water discharge can be a satisfactory predictor of chemical water quality parameters in this river. It was finally concluded when water discharge of the river decreases to less than ~500m³s^-1, the vales of water salinity (EC and TDS) and soluble salts will increase, severely.

Isotopic fractionation of particulate organic matter and its biogeochemical implication in the littoral zone of Lake Taihu, China

Signatures of stable isotope ratios have previously been used to trace the source and transport of particulate organic matter (POM) in freshwater and marine ecosystems. In this study, water columns were collected at 22 sites in the littoral zone of Lake Taihu in 2014 to investigate the distribution and concentration of nutrients and the stable isotope signatures of POM, and their potential interrelation. Generally, mean concentration of nitrogen forms (NH₄⁺-N) showed substantial variation, probably because they had received large amounts of wastewater from various local industrial enterprises. Source analysis by stable carbon and nitrogen isotopic ratios showed that the main POM sources were phytoplankton. Contrasting correlations were obtained between δ¹⁵N and N concentrations in effluent river mouths when compared with influent river mouths. In effluent river mouths, there was a significant positive correlation between δ¹⁵N and nitrogen concentration (total nitrogen and ammonia-nitrogen), in contrast with the negative correlation in influent river mouths. According to these results, more factors should be taken into consideration when stable carbon and nitrogen isotopes of POM are used to assess the feeding relationship between consumers and prey, as well as the energy flow pathways that support the lake pelagic food webs.

Spatial Distribution of Pemphigus Occurrence over Five Decades in Southeastern Brazil

Well-defined locations of pemphigus cases support the hypothesis of environmental factors' involvement in its etiopathogenesis; however, these foci have never been described using specialized geographical tools. This is the first report to geo-reference pemphigus cases in a high-prevalence Brazilian region using geographic information systems. We aimed to report the spatio-temporal behavior of pemphigus foliaceus (PF) and vulgaris (PV) in southeastern Brazil, over the last five decades to describe geographical clusters, as well as to characterize the land use in the city with the highest number of cases. Patients were identified from 1965 to 2014. Maps were developed using ArcGIS software and organized into decades from 1965 to 2014. Ribeirão Preto was identified as the city with the greatest number of cases. Land use was analyzed within a 2 km-buffer surrounding the residence of each patient. A total of 426 cases of pemphigus were identified. PF was the predominant form (285 cases); notwithstanding, the number of new cases of PV rose, overtaking the number of new cases of PF in the last decade studied. Agricultural area (42%) and exposed soil (33.2%) are the most predominant land uses in Ribeirão Preto surrounding patients' residences. This study shows high-confidence geographical foci of PF and PV, as well as provides evidence of an increase of both clinical forms over the last five decades. All cases of PV and PF are in proximity to rivers and agricultural areas which reinforce the hypothesis that environmental factors play a role in pemphigus etiopathogenesis.

Evaluation of heavy metal risk potential in Bogacayi River water (Antalya, Turkey)

This study analyzed 25 river water samples collected from the Bogacayi River in Antalya, Turkey, to evaluate the potential risk of pollution by heavy metals. Concentrations of As, Ba, Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb, Se, Sr, and V were determined by inductively coupled plasma mass spectrometry (ICP-MS). The method was validated prior to analysis in terms of linearity, limit of detection (LOD), limit of quantification (LOQ), and recovery. In addition, a certified standard (SPS-SW2 surface water) was used to verify method trueness. Method validation data and results obtained from the certified material suggested that the method could be applied to determine elemental compositions of the samples. Although various concentrations of As, Ba, Cd, Cr, Cu, Mn, Ni, Pb, and Sr were found in the samples, no Hg, V, Co, and Se concentrations were found. The highest concentration of Pb, Cd, and As was found in the samples from the 22nd, 16th, and 5th sampling stations, respectively. Concentrations of the studied elements were aligned from high to low as Sr > Ba > Ni > Cr > Cu > Mn > Pb > As > Cd. To evaluate the risk potential of metallic pollution, the data were used to calculate the heavy metal pollution index (HPI). The HPI values were found to be in the range from 7.81 to 43.97 (mean 25.48). Samples from upstream seemed to show lower risk potentials (<15) than those from downstream (>30); however, all HPI values were lower than 100, which is the critical HPI value for drinking safety.

Assessment of soil quality parameters using multivariate analysis in the Rawal Lake watershed

Soil providing a wide array of ecosystem services is subjected to quality deterioration due to natural and anthropogenic factors. Most of the soils in Pakistan have poor status of available plant nutrients and cannot support optimum levels of crop productivity. The present study statistically analyzed ten soil quality parameters in five subwatersheds (Bari Imam, Chattar, Rumli, Shahdra, and Shahpur) of the Rawal Lake. Analysis of variance (ANOVA), cluster analysis (CA), and principal component analysis (PCA) were performed to evaluate correlation in soil quality parameters on spatiotemporal and vertical scales. Soil organic matter, electrical conductivity, nitrates, and sulfates were found to be lower than that required for good quality soil. Soil pH showed significant difference (p < 0.05) in mean values at different sampling sites and sampling months indicating that it is affected and determined by land uses and seasons. Pearson correlation revealed a strong positive correlation (r = 0.437) between nitrates and organic matter. Application of principal component analysis resulted in three major factors contributing 76 % of the total variance. For factor 1, temperature, sand, silt, clay, and nitrates had the highest factor loading values (>0.75) and indicated that these were the most influential parameters of first factor or component. Cluster analysis separated five sampling sites into three statistically significant clusters: I (Shahdra-Bari Imam), II (Chattar), and III (Shahpur-Rumli). Among the five sites, Shahdra was found to have good quality soil followed by Bari Imam. The present study illustrated the usefulness of multivariate statistical approaches for the analysis and interpretation of complex datasets to understand variations in soil quality for effective watershed management.

Water Quality Assessment of River Soan (Pakistan) and Source Apportionment of Pollution Sources Through Receptor Modeling

The present study was designed to determine the spatiotemporal patterns in water quality of River Soan using multivariate statistics. A total of 26 sites were surveyed along River Soan and its associated tributaries during pre- and post-monsoon seasons in 2008. Hierarchical agglomerative cluster analysis (HACA) classified sampling sites into three groups according to their degree of pollution, which ranged from least to high degradation of water quality. Discriminant function analysis (DFA) revealed that alkalinity, orthophosphates, nitrates, ammonia, salinity, and Cd were variables that significantly discriminate among three groups identified by HACA. Temporal trends as identified through DFA revealed that COD, DO, pH, Cu, Cd, and Cr could be attributed for major seasonal variations in water quality. PCA/FA identified six factors as potential sources of pollution of River Soan. Absolute principal component scores using multiple regression method (APCS-MLR) further explained the percent contribution from each source. Heavy metals were largely added through industrial activities (28 %) and sewage waste (28 %), nutrients through agriculture runoff (35 %) and sewage waste (28 %), organic pollution through sewage waste (27 %) and urban runoff (17 %) and macroelements through urban runoff (39 %), and mineralization and sewage waste (30 %). The present study showed that anthropogenic activities are the major source of variations in River Soan. In order to address the water quality issues, implementation of effective waste management measures are needed.

Geochemistry and magnetic measurements of suspended sediment in urban sewage water vis-à-vis quantification of heavy metal pollution in Ganga and Yamuna Rivers, India

Sewage water is becoming a key source of heavy metal toxicity in large river systems worldwide and the two major Himalayan Rivers in India (Ganga and Yamuna) are severely affected. The high population density in the river banks combined with increased anthropogenic and industrial activities is contributing to the heavy metal pollution in these rivers. Geochemical data shows a significant increase in the concentration of all heavy metals (Pb, 48-86 ppm; Zn, 360-834 ppm; V, 45-101 ppm; Ni, 20-143 ppm; Cr, 79-266 ppm; Co, 8.62-22.12 ppm and Mn, 313-603 ppm) in sewage and mixed water (sewage and river water confluence site) samples due to increased effluent discharge from the catchment area. The ΣREE content of sewage water (129 ppm) is lower than the average mixed water samples (142 ppm). However, all the samples show similar REE pattern. The mass magnetic susceptibility (Xlf) values of suspended sediments (28 to 1000 × 10(-8) m(3) kg(-1)) indicate variable concentration of heavy metals. The Xlf values show faint positive correlation with their respective bulk heavy metal contents in a limited sample population. The present study comprising geochemical analysis and first magnetic measurement data of suspended sediments in water samples shows a strongly polluted nature of Ganga and Yamuna Rivers at Allahabad contrary to the previous report mainly caused by overtly polluted city sewage water.

Strategies to optimize monitoring schemes of recreational waters from Salta, Argentina: a multivariate approach

Several recreational surface waters in Salta, Argentina, were selected to assess their quality. Seventy percent of the measurements exceeded at least one of the limits established by international legislation becoming unsuitable for their use. To interpret results of complex data, multivariate techniques were applied. Arenales River, due to the variability observed in the data, was divided in two: upstream and downstream representing low and high pollution sites, respectively, and cluster analysis supported that differentiation. Arenales River downstream and Campo Alegre Reservoir were the most different environments, and Vaqueros and La Caldera rivers were the most similar. Canonical correlation analysis allowed exploration of correlations between physicochemical and microbiological variables except in both parts of Arenales River, and principal component analysis allowed finding relationships among the nine measured variables in all aquatic environments. Variable's loadings showed that Arenales River downstream was impacted by industrial and domestic activities, Arenales River upstream was affected by agricultural activities, Campo Alegre Reservoir was disturbed by anthropogenic and ecological effects, and La Caldera and Vaqueros rivers were influenced by recreational activities. Discriminant analysis allowed identification of subgroup of variables responsible for seasonal and spatial variations. Enterococcus, dissolved oxygen, conductivity, E. coli, pH, and fecal coliforms are sufficient to spatially describe the quality of the aquatic environments. Regarding seasonal variations, dissolved oxygen, conductivity, fecal coliforms, and pH can be used to describe water quality during dry season, while dissolved oxygen, conductivity, total coliforms, E. coli, and Enterococcus during wet season. Thus, the use of multivariate techniques allowed optimizing monitoring tasks and minimizing costs involved.

Spatial and temporal variability of surface water pollution in the Mekong Delta, Vietnam

Surface water pollution in the Vietnamese Mekong Delta (MD) could threaten human, animal and ecosystem health given the fact that this water source is intensively used for drinking, irrigation and domestic services. We therefore determined the levels of pollution by organic pollutants, salts, metals and microbial indicators by (bi)monthly monitoring of canals between November 2011 and July 2012 at 32 sampling locations, representing fresh and saline/brackish environments. The results were compared with national water quality guidelines, between the studied regions and with water quality data from main waterways. Key factors explaining the observed levels of pollution in surface water were identified through principal component analysis (PCA). Temporal variations due to tidal regime and seasonality were also assessed. Based on regression models, the spatial variability of five water quality parameters was visualized using GIS based maps. Results indicate that pH (max. 8.6), turbidity (max. 461 FTU), maximum concentrations of ammonium (14.7 mg L(-1)), arsenic (44.1 μg L(-1)), barium (157.5 μg L(-1)), chromium (84.7 μg L(-1)), mercury (45.5 μg L(-1)), manganese (1659.7 μg L(-1)), aluminum (14.5 mg L(-1)), iron (17.0 mg L(-1)) and the number of Escherichia coli (87,000 CFU 100 mL(-1)) and total coliforms (2,500,000 CFU 100 mL(-1)) in canals exceed the thresholds set by Vietnamese quality guidelines for drinking and domestic purposes. The PCA showed that i) urbanization; ii) metal leaching from soils; iii) aquaculture; and iv) tidal regime explain 85% of the variance of surface water quality attributes. Significant differences in water quality were found due to daily tidal regime and as a result of seasonality. Surface water quality maps for dissolved oxygen, ammonium, ortho-phosphate, manganese and total coliforms were developed to highlight hot-spot areas of pollution. The results of this study can assist policy makers in developing water management strategies and drinking water companies in selecting optimum water extraction locations.

Identifying diffused nitrate sources in a stream in an agricultural field using a dual isotopic approach

Nitrate (NO3(-)) pollution is a severe problem in aquatic systems in Taihu Lake Basin in China. A dual isotope approach (δ(15)NNO3(-) and δ(18)ONO3(-)) was applied to identify diffused NO3(-) inputs in a stream in an agricultural field at the basin in 2013. The site-specific isotopic characteristics of five NO3(-) sources (atmospheric deposition, AD; NO3(-) derived from soil organic matter nitrification, NS; NO3(-) derived from chemical fertilizer nitrification, NF; groundwater, GW; and manure and sewage, M&S) were identified. NO3(-) concentrations in the stream during the rainy season [mean±standard deviation (SD)=2.5±0.4mg/L] were lower than those during the dry season (mean±SD=4.0±0.5mg/L), whereas the δ(18)ONO3(-) values during the rainy season (mean±SD=+12.3±3.6‰) were higher than those during the dry season (mean±SD=+0.9±1.9‰). Both chemical and isotopic characteristics indicated that mixing with atmospheric NO3(-) resulted in the high δ(18)O values during the rainy season, whereas NS and M&S were the dominant NO3(-) sources during the dry season. A Bayesian model was used to determine the contribution of each NO3(-) source to total stream NO3(-). Results showed that reduced N nitrification in soil zones (including soil organic matter and fertilizer) was the main NO3(-) source throughout the year. M&S contributed more NO3(-) during the dry season (22.4%) than during the rainy season (17.8%). AD generated substantial amounts of NO3(-) in May (18.4%), June (29.8%), and July (24.5%). With the assessment of temporal variation of diffused NO3(-) sources in agricultural field, improved agricultural management practices can be implemented to protect the water resource and avoid further water quality deterioration in Taihu Lake Basin.

Assessment of physico-chemical qualities and heavy metal concentrations of Umgeni and Umdloti Rivers in Durban, South Africa

We assessed the effects of seasonal dynamics on the physico-chemical qualities and heavy metals concentrations of the Umgeni and Umdloti Rivers in Durban, South Africa. Water samples were taken from nine different sampling points and analysed for the following parameters; temperature, pH, turbidity, electrical conductivity (EC), biological oxygen demand (BOD5), chemical oxygen demand (COD), phosphate (PO4(2-)), nitrate (NO3(2-)), ammonium (NH4(+)), sulphate (SO4(2-)), lead (Pb(2+)), mercury (Hg(2+)), cadmium (Cd(2+)), aluminium (Al(3+)), and copper (Cu(2+)) using standard methods. The data showed variations it terms of the seasonal fluctuations and sampling regime as follows: temperature 12-26.5 °C; pH 5.96-8.45; turbidity 0.53-18.8 NTU; EC 15.8-5180 mS m(-1); BOD5 0.60-7.32 mg L(-1); COD 10.5-72.9 mg L(-1); PO4 (2-) < 500-2,460 μg L(-1); NO3 (2-) <0.05-4.21 mg L(-1); NH4 (+) < 0.5-1.22 mg L(-1); SO4 (2-) 3.90-2,762 mg L(-1); Pb(2+) 0.023-0.135 mg L(-1); Hg(2+) 0.0122-0.1231 mg L(-1) Cd(2+) 0.068-0.416 mg L(-1); Al(3+) 0.037-1.875 mg L(-1), and Cu(2+)0.006-0.144 mg L(-1). The concentrations of most of the investigated parameters exceeded the recommended limit of the South African Guidelines and World Health Organization tolerance limits for freshwater quality. We conclude that these water bodies are potentially hazardous to public health and this highlights the need for implementation of improved management strategies of these river catchments for continued sustainability.

Microbiological, coliphages and physico-chemical assessments of the Umgeni River, South Africa

The water quality of Umgeni River in KwaZulu-Natal (South Africa) was investigated from April 2011 to January 2012. Indicator bacterial populations, physico-chemical properties, heavy metal contaminants and the presence of coliphages were determined according to standard protocols. The results showed that all sampling points failed to comply with the set guidelines for turbidity, total coliform, faecal coliform and total heterotrophic counts. Salmonella spp., Shigella spp. and Vibrio cholerae were also detected in all the water samples. The somatic coliphages and F-RNA coliphages were detected more frequently in the lower reaches of the river during summer. Temperature, electrical conductivity and pH were found to have positive relationships with the microbial communities especially in the lower catchment area during spring and summer indicating the impacts of various anthropogenic activities in the surrounding areas.

Spatial pattern assessment of river water quality: implications of reducing the number of monitoring stations and chemical parameters

The Tamsui River basin is located in Northern Taiwan and encompasses the most metropolitan city in Taiwan, Taipei City. The Taiwan Environmental Protection Administration (EPA) has established 38 water quality monitoring stations in the Tamsui River basin and performed regular river water quality monitoring for the past two decades. Because of the limited budget of the Taiwan EPA, adjusting the monitoring program while maintaining water quality data is critical. Multivariate analysis methods, such as cluster analysis (CA), factor analysis (FA), and discriminate analysis (DA), are useful tools for the statistically spatial assessment of surface water quality. This study integrated CA, FA, and DA to evaluate the spatial variance of water quality in the metropolitan city of Taipei. Performing CA involved categorizing monitoring stations into three groups: high-, moderate-, and low-pollution areas. In addition, this categorization of monitoring stations was in agreement with that of the assessment that involved using the simple river pollution index. Four latent factors that predominantly influence the river water quality of the Tamsui River basin are assessed using FA: anthropogenic pollution, the nitrification process, seawater intrusion, and geological and weathering processes. We plotted a spatial pattern using the four latent factor scores and identified ten redundant monitoring stations near each upstream station with the same score pattern. We extracted five significant parameters by using DA: total organic carbon, total phosphorus, As, Cu, and nitrate, with spatial variance to differentiate them from the polluted condition of the group obtained by using CA. Finally, this study suggests that the Taiwan EPA can adjust the surface water-monitoring program of the Tamsui River by reducing the monitoring stations to 28 and the measured chemical parameters to five to lower monitoring costs.

Water Quality of River Kosi and Rajera System at Rampur (India): Impact Assessment

River Kosi, an important tributary of river Ramganga, is one of the important rivers of Uttaranchal and Uttar Pradesh After traveling for about 100 kms in lower Himalayas with higher velocity, it emerges at Ramnagar in Indo-Gangetic plains. Here, the major portion of city sewage is discharged into it. Then, it flows through the famous rice belt area of Kashipur, where a number of polluting industries discharge their highly polluted effluents into it. To determine the extent of pollution in downstream district Rampur, a study was conducted. The aim of this study was to evaluate the effect of dilution caused by the merger of river Rajera with Kosi River. For this samples, were collected from three stations and analyzed for various parameters for the period of one year. The study revealed higher levels of industrial pollution as compared to domestic pollution. It also shows the alleviating effects of dilution caused by the merger of river Rajera.

Study of physico-chemical characteristics of wastewater in an urban agglomeration in Romania

This study investigates the level of wastewater pollution by analyzing its chemical characteristics at five wastewater collectors. Samples are collected before they discharge into the Danube during a monitoring campaign of two weeks. Organic and inorganic compounds, heavy metals, and biogenic compounds have been analyzed using potentiometric and spectrophotometric methods. Experimental results show that the quality of wastewater varies from site to site and it greatly depends on the origin of the wastewater. Correlation analysis was used in order to identify possible relationships between concentrations of various analyzed parameters, which could be used in selecting the appropriate method for wastewater treatment to be implemented at wastewater plants.

Water quality evaluation based on improved fuzzy matter-element method

For natural water, method of water quality evaluation based on improved fuzzy matter-element evaluation method is presented. Two important parts are improved, the weights determining and fuzzy membership functions. The coefficient of variation of each indicator is used to determine the weight instead of traditional calculating superscales method. On the other hand, fuzzy matter-elements are constructed, and normal membership degrees are used instead of traditional trapezoidal ones. The composite fuzzy matter-elements with associated coefficient are constructed through associated transformation. The levels of natural water quality are determined according to the principle of maximum correlation. The improved fuzzy matter-element evaluation method is applied to evaluate water quality of the Luokou mainstream estuary at the first ten weeks in 2011 with the coefficient of variation method determining the weights. Water quality of Luokou mainstream estuary is dropping from level I to level II. The results of the improved evaluation method are basically the same as the official water quality. The variation coefficient method can reduce the workload, and overcome the adverse effects from abnormal values, compared with the traditional calculating superscales method. The results of improved fuzzy matter-element evaluation method are more credible than the ones of the traditional evaluation method. The improved evaluation method can use information of monitoring data more scientifically and comprehensively, and broaden a new evaluation method for water quality assessment.

Heavy metals in northern Chilean rivers: spatial variation and temporal trends

Rivers of central-northern Chile are exposed to pollution from different sources, including mining activities, natural orogenic process, volcanic activity, and geology. In order to determine the contribution of mining to river pollution, the spatio-temporal dynamics of chemical species dissolved in 12 rivers of central-northern Chile was assessed. Of all the rivers studied, the Elqui showed the highest historical mean concentrations of As, Cu and Pb. The Aconcagua had the highest concentration of Hg and a large Cr concentration, while the Rapel showed elevated concentrations of Cu and Mo. The Elqui and the Aconcagua were clustered as distinct groups by a cluster analysis based on two independent principal components. Hierarchical Bayesian models showed annual trends but no seasonal effects in heavy metal concentrations. As and Cu in the Elqui had positive annual slopes. Sulphate concentration exceeded 100 mg L(-1) in nine rivers, and in seven of them it had positive annual slopes. Our findings suggest that mining pollution is the main process contributing to this increasing annual trend in As, Cu and SO(4)(2-). Therefore, in order to improve the water quality of these rivers it is necessary to identify the main sources of heavy metals associated with mining activities.

Assessment of surface water quality of the Ceyhan River basin, Turkey

In this study, surface water quality of the Ceyhan River basin were assessed and examined with 13 physico-chemical parameters in 31 stations in 3 months during the period of 2005. Multivariate statistical techniques were applied to identify characteristics of the water quality in the studied stations. Nutrients, Cl- and Na+ affected mostly to the stations of Erkenez 2, Sir 2, and Sir 3 in the ordination diagram of correspondence analysis. Three factors were extracted by principal component analysis, which explains 79.14% of the total variation. The first factor (PC1) captures variables of EC, DO, NO2-, PO4triple bond, Cl-, SO4=, Na+, and Ca++. The second factor (PC2) is significantly related to pH, NH3-, and Mg++, while water temperature (T) and NO3- accounted for the greatest loading for factor 3 (PC3). The stations were divided into three groups for PC1, two groups for PC2, and three groups for PC3 by hierarchical cluster analysis. The stations in the vicinity of cities presented low dissolved oxygen and high concentration of physico-chemical parameter levels. The stations of Erkenez 2, Sir 2, Sir 3, and Aksu 4 located near the city of Kahramanmaraş were characterized by an extremely high pollution due to discharge of wastewater from industry and domestic. Pinarbaşi and Elbistan stations were also influenced by household wastewater of the city of Elbistan. According to criteria of Turkish Water Pollution Control Regulation, Erkenez 2, Sir 2, and Sir 3 stations have high polluted water. This study suggests that it is urgent to control point pollutions, and all wastewater should be purified before discharge to the Ceyhan River basin.

Spatial and seasonal variations of the contamination within water body of the Grand Canal, China

To delineate the character of contaminations in the Grand Canal, China, a three-year study (2004-2006) was conducted to investigate variations the water quality in the canal. Results showed that the variation of water quality within the Grand Canal was of there is remarkable spatial and seasonal heterogeneity regarding water quality within the Canal. Values of contaminants in dry-season were obviously higher than those in wet-season. Sites influenced strongly by industry and urbanization showed higher contents of nutrients and lower levels of dissolved oxygen in water body; moreover these sites were severely polluted by dissolved metals with the contents of cadmium, chromium and copper exceeding the Criteria Maximum Concentration (CMC), US EPA. Multivariate statistical analysis suggested nutrient and dissolved metals pollution was the dominant environmental problems within the Canal. Anthropogenic influences played a dominant role in the character of contaminations in the Grand Canal.