The Study On Algae Growth And The Formation Of Toxins In Qingcaosha Researvoir

Due to the rapid development of industry and agriculture, the surge in volume of sewage discharge has increased water pollution. Many major river systems are in eutrophication in China. Eutrophication caused water deterioration and then bloom outbreak. In recent yesrs, outbreak of algae and their toxins affected safety of water supply, population health and social stability.Usually, human exposure to algal toxins by several ways, such as daily drinking water, food and wading entertainment. There were a variety of algal toxins, and Microcystins (MCs) and anatoxin-a are the most risk for animal and human. Spectrum of adiverse effects are from discomfort to death according to exposure dose and exposure time. Acute high dose exposure induced gastroenteritis, vomiting, abdominal pain and even death. Plenty of studies testified MCs were cancer promotor, and risk factors of liver cancer and colorectal cancer. Population epidemiological studies indicated long-term exposure from drinking water of MCs can cause liver and colorectal cancer in China and United States. Pro visional limit of1μg/L was drawed up accrodding subchronic mice exposured experiment by World Health Organization (WHO).Anatoxin-a, a neurotoxin, has been concerned intensely by its rapid lethal effect. So far, there is no standard limit of anatoxin-a in drinking water in WHO, and only in Newzealand and Austrilia there are provisional limits. There is no standard detection method and limit in drinking water in China, while blooms are common and heavy.Several genus of cyanobacteria can produce both MCs and anatoxin-a, so they coexist in water and have synergic effect.Problems of public health induced by decreasing water quality and water overload intake were alleviated and improved by establishment of Qingcaosha reservoir (QCSR), a new main water source in Shanghai replacement of Huangpu River. QCSR locates in eatury of Yangtze River, storing high quality fresh water from Yangtze River avoiding salt water intrusion. QCSR can provide high quality water source for population by improvement water quality mainly through self-purification and provide high quality drinking water for Shanghai municipal. QCSR is the largest estuarine reservoir in China, study of the algea growth and their toxins formation is of great significance for safety of city water supply, and also can provide basic knowneledge for future study of other estuarine researvoirs.Our study was carried out to assess water quality and eutrophic state firstly. On the basis of algal numerate and genus identification to learn of algal contamination and algal structure, and by utilization of principal components analyse, to analyze their impact factors and fit their pridective models. Based on HPLC detection method for MC-LF/LW/LR/RR/YR, we detect MCs qualitatively and quantitatively in QCSR. To analyze the impact factors of dissolved MCs by generalized least squares (GLS), and to test correlation of MCs and cyanobacteria density. To establish a HPLC detection method for anatoxin-a, and investigation its contamination levels in QCSR and finished water.Part1Algae growth and microcystions formation in Qingcaosha ResearvoirOur study monitored water quality indicators of total nitrogen (TN), total phosphorous (TP), potassium permanganate index (CODMn), chlorophyll-a (Chl-a), pH, transparency (SD), water temperature (WT), and dissolved oxygen (DO) succesively, and assessed by National Environmental quality standards for surface water (GB3838-2002). Trophic states of QCSR were assessed by calculation of single and comprehensive trophic state index (TSIM) for SD, TN, TP, Chl-a and CODMn, The results showed that, water quality cannot satisfy IIIstandard limits of National Environmental quality standards for surface water. DO and CODMn satisfied Ⅲ standard limits of National Environmental quality standards for surface water, pH ranged between8.0and9.2, a little alkaline, most of it satisfied IIIstandard limits of National Environmental quality standards for surface water, TN and Chl-a cannot satisfy IIIstandard limits of National Environmental quality standards for surface water after February, most of TP levels were above0.05mg/L that cannot satisfy Ⅲ standard limits of National Environmental quality standards for surface water. Comprehensive TSIM (CTSIM) was in light eutrophication, and TSIM(TP) and TSIM(SD) were the most eutrophication. Algal numeration, identification and diversity were ivestigated in QCSR. Sample sites located at the heading, stagnant water area, itermediate area and the ending of QCSR. Temporal and spacial trends of algal density and stucture, and pricipal component analysis (PCA) was employed to analyze impact factors of total algae density and cyanobacteria density. Results showed, algal density was above million per liter, and the peak occurred in Febuary2011. There were8phylum51genus commonly appeared, chlorophyte was the main dominant phylum, and cyanobacteria dominated only in July. Algal displayed obvious spacial trends, increasing from the heading to stagnant water area, and then decreasing to the ending for total algal density and algal diversity, decreasing of proportion of cyanobacteria and increasing of proportion of chlorophyte, cryptophyte and euglenophyte. Algal density and diversity decreased along with increasing of water depth. Algal diversity was between17and37genus, and lowest at the ending of QCSR. The results from PC A were that, TP and WT were significantly negative correlated with total algal density, DO, TN/TP, Chl-a and light were significantly positive correlated with tatol algal density, and the role of TN was weak. TP had no correlation with cyanobacteria density in current QCSR, NH3-N, TN, turbidity and NO3-N had significantly positive correlations with cyanobacteria density, SD, DO, TN/TP and Chl-a had significantly negative correlations with cyanobacteria density, and the remains had weak play on cyanobacteria density.Investigation of5isomers of MCs in QCSR showed, they had different temporal trends and contamination levels. Dissolved MCs were about0.1μg/L acrossing study period, and the heaviest contamination levels occurred in May and June2011, above0.4μg/L. From the heading to the ending, MCs levels increased and then decreased, and the heaviest contamination was at staganant area. Itermediate area was heavieat polluted in spring and the heading in summer showed by GIS. DO had significantly negative correlations with dissolved MCs, and SD, TN and Chl-a had significantly positive correlations with dissolved MCs analyzed by generalized least square (GLS). Total MCs were significantly positive correlated with cyanobacteria density, while not with total algal density according to Pearson correlation results.Part2Investigation of anatoxin-a contamination levels in Qingcaosha Reservoir and finished waterAnatoxin-a is a neurotoxin. There is no standard limit and detection method of anatoxin-a in our current National Drinking Water Standards (GB5749-2006). Establishing a detection method for anatoxin-a in drinking water can provide a standard and effective method for investigation of anatoxin-a contamination later on. This study established a detection method for drinking water based on HPLC. Elution effects of several elutions containing different volume of TFA, recovery efficiency, sensitivity and precision were detected to testify accuracy and reliability of this method. Results showed, methanol containing0.2%TFA had an optimal elution effect. The linear range of standard curve was0.01μg/ml～5μig/ml and R2was0.9999. Detection limit of anatoxin-a was2.9ng/L in water sample. Spiked recovery rates and relative standard deviation (RSD) were75.2%～100.6%and6.38%～8.76%, respectively. When detected continuously for six days, average values were consistent with the true values, and intra-and inter-day RSD was among1.60%～8.90%. So, this method had low detection limit, high recovery rate and accuracy, good stability and reliability, which can be used to detect trace anatoxin-a in water and even for continuous batch detection.Water samples were collected from Qingcaosha Reservoir and its two provided plants, filtered by GF/C membrane, enriched by weak cation-exchange packing (WCX) for intracellular and dissolved anatoxin-a, and detected by HPLC. Meanwhile, algal density and structure were also investigated.There were low levels contamination of anatoxin-a in QCSR for intracellular anatoxin-a was detected from outlet of QCSR, raw water of PD and YSP water plants (80.7ng/L,.5.8ng/L and29.4ng/L, respectively). Current water treatment can eliminate low levels of anatoxin-a since anatoxin-a was non-detection in both finished water. Microcystis occurred in QCSR with0.10-0.55X106cells/L. More attention should be paid to surveillances of QCSR and finished water because of neurotoxicology of anatoxin-a and its potential health adverse effects.