Pollution Monitoring And Risk Assessment Of Heavy Metals And Organic Pollutants In Soil And Water From Typical Agricultural Watersheds In Southeast China

In agricultural watersheds, the pollution of heavy metals, pesticides, and estrogens has special characteristics. However, related research is lacking. In this study, we moni-tored pollution and assessed the risk of heavy metals and organic pollutants in soil and wa-ter from typical agricultural watersheds in southeast China, Tiaoxi River and Siling reser-voir. The results and conclusion can be summarized as follow:In this study, the water quality index (WQI) of Siling reservoir was verified to calcu-late scores based on water characteristics data using an online water quality monitoring system from September2011to September2012. WQI (including ten parameters:pH, WT, EC, DO, TDS, CODm,,, TP, TN, NH4+-N, and turbidity) and a minimal water quality index (WQImin)(including five parameters:water temperature, pH, DO, EC and turbidity) were investigated. Multivariate statistical analysis techniques viz:correlation analysis and re-dundancy analysis (RDA) were employed to analyze the obtained data. The results showed that water quality was good in the Siling reservoir during autumn and winter sea-sons. However, a decreasing trend in water quality was observed during spring and sum-mer seasons. WQImin illustrates similar trend to WQI with a better R2value of0.99, with a minimum cost and could be useful for the intervallic routine monitoring program. Higher positive correlation between WQI and DO was observed during winter season. Moreover, the results further indicated the risk of algal blooms in the reservoir water, which reflected the effects of climatic condition on reservoir water quality. This study suggested that the resulting WQI provides valuable information on developing, monitoring and understand-ing surface source water quality for the decision makers and reservoir management.The concentrations of seven metals (Zn, Cu, Mn, Fe, Cr, Cd and Pb) were deter-mined in agricultural soils from Siling reservoir watershed. Multivariate statistical ap-proaches were used to study the variation of metals in soils during summer and winter sea-sons. Heavy metal concentrations were observed higher in winter season as compared to summer season. Cr and Cd revealed random distribution with diverse correlations in both seasons. Principal component analysis and cluster analysis showed significant anthropo-genic intrusions of Zn, Cd, Pb, Cr and Cu in the soils. Enrichment factor, revealed signifi- cant enrichment of Zn, Cd and Pb, whereas, geoaccumulation index and contamination factor exhibited moderate to high contamination for Zn, Cr, Cd and Pb.Spatio-temporal variations and risk assessment of the selected heavy metals (Zn, Cu, Mn, Fe, Cr, Cd and Pb) were investigated in water samples from Siling reservoir wa-tershed. During summer season Mn, Fe and Cd concentrations were higher in the water samples, while the concentrations of Zn, Fe and Pb were dominant in winter season. How-ever, Cr exhibited elevated concentrations in both seasons. The health risk assessment re-vealed that hazard quotient (HQing) and hazard index (HIing) values were near to the ac-ceptable limit indicating non-carcinogenic risk to the recipient via oral intake of water. The calculated values for chronically daily intake were found in the order of Cr> Fe> Mn> Zn> Cd in summer season and Zn> Fe> Cr> Pb> Mn> Cu during winter season. The carcinogenic risk (CRing) via ingestion route for Cr, Cd and Pb were noted higher than the acceptable limit (10-6). Multivariate statistical analysis such as; cluster analysis (CA) and principal component analysis (PCA) results revealed that both natural processes and an-thropogenic activities were the main sources of water contamination.Seasonal concentrations of legacy organochlorine pesticides (OCPs), polycyclic aro-matic hydrocarbons (PAHs), and polychlorinated biphenyls (PCBs) were determined in soil samples from agricultural fields of the Siling reservoir watershed. Persistence organic pollutants (POPs) were found in almost all of the soil samples. The total concentrations of OCPs, PAHs, and PCBs during summer and winter seasons ranged from21.85to21.64ng g-1,40.33to38.83ng g-1, and86.98to74.29ng g-1, respectively. The total concentrations of individual POPs were further used to evaluate the cancer risk probabilities in human via ingestion, dermal contact, and inhalation of soil particles. Near to very low cancer risk of every POPs was found in the soils of the Siling reservoir watershed. Furthermore, cancer risk, based on total OCPs, PAHS and PCBs concentrations were also investigated. Results revealed cancer risk with a value of1.07×10-6, which was a little higher than the ac-ceptable limit (10-6).Estrogens levels in wastewater collected from a large-scale swine farm in Tiaoxi River watershed near by Siling reservoir were analyzed. And the efficiency of estrogen removal by anaerobic/aerobic active sludge (A/O) treatment or by upflow anaerobic sludge blanket and step-fed sequencing batch reactor (UASB-SFSBR) treatment was also investigated. The results showed that the A/O treatment had no significant estrogenic re-moval ability, whereas the removal rates of estrogen after UASB-SFSBR treatment reached approximately78%, as measured by LC-MS/MS. The17?-estradiol equivalents (EEQ) decreased from31.5ng L-1to an undetectable level according to the Yeast Estro-gen Screen (YES) analysis. We found differences between the estrogen removal rates measured by the chemical assay and those measured using the bioassay. More attention must be paid to the removal of estrogen pollutants in livestock wastewater to reduce the environmental risk.The estrogen pollution in surface water of Tiaoxi River watershed was investigated by chemical and bioassay analysis. Most estrogens species, except estrone, were not de-tected by the chemical analysis using LC-MS/MS. The concentration of estrone in the samples ranged from below the detection limit to17.25ng L"1. The estrogen activity in most water samples was also determined by YES. The17?-estradiol activity could be de-tected in all water samples. EEQ in sample from the estuary of Taihu Lake was17.60ng L-1. This study demonstrates that combining chemical and bioassay analysis is an effective way to detect environmental contamination by estrogen species. Furthermore, the results indicate that the risk of estrogen contamination in the Tiaoxi River watershed should be controlled.