Study On The Pollution Of Microcystins And Environmental Factors

Microcystins (Microcystins, MCs) is the most popular algae toxin generated by the explosive propagation of cyanobacteria in the fresh water in the state of eutrophication. It is a kind of single-ring seven peptide toxin, the toxin has a strong liver toxicity and tumor promoting role. Shanzai reservoir as a the second drinking water resource for Fuzhou citizens showed somewhat eutrophication in recent years, Therefore it is urgently necessary to monitor the MC levels and understand its environmental behaviors in Shanzai reservoir, for controlling the harmful effects of MC to local citizens and keeping the health of citizens.In this study, some key techniques for monitoring the three microcystin MC-LR, MC-RR, MC-YR by use of high-performance liquid chromatography (HPLC) analysis and solid-phase extraction for sample preparation were optimized, and with the monitoring technique, the microcystin pollution levels and environmental factors in Shanzai reservoir were monitored in the whole year of 2007. Some meaningful research conclusions were listed as following:(1) The key techniques of monitoring MCsIt is a better separation for the MC-YR, MC-LR and MC-RR in HPLC sample analysis: the methanol: 0.06% TFA solution = 60:40 (V/V) as the mobile phase. It will have a higher recovery rate during the Solid Phase Extraction in pre-treatment process: using 0.1% TFA-methanol as the eluate for the three toxins MC-YR, MC-LR and MC-RR, and the recovery rate would reach 91%, 89.8%, 81% respectively. For environmental samples to use 20% methanol as eluent can reduce the impurity peaks impact on the HPLC analysis, and can ensure the recovery.(2) The characteristics of MCs in Shanzai Reservoir in 2007MC-YR is the main form of microcystins in Shanzai reservoir in 2007. In the season of June to September with high algae growth, MC-YR were detected out with the highest concentration 0.374μg/L in the water, lower than the national drinking water standard 1.0μg/L. Adding glacial acetic acid in the water to breaking algal cells, the content of microcystins increased up to 41.1 times of the original level. (3) The relationship among MCs and water environmental indicatorsThe critical water environmental indicators which directly influence the MC levels were proved as Water temperature,TN/TP and TP. There is not significant correlation between the Water Primary Productivity - chlorophyll-a and microcystins. Under the conditions of higher water temperature and adequate supply of phosphorus, higher level of MC will exist in water. Therefore, it is regarded that the key problem of keeping the safety of drinking water is to reduce the TP level in June to Sept. with the higher temperature in whole year. For water quality parameters, TP-TN-chlorophyll-a showed a significant correlations. Chlorophyll-a level was strongly impacted by the level of TN and TP, as well as the interaction between them.(4) Assessment of the water quality and relations between MCs and water qualityIn 2007, the nutrition status of Shanzai reservoir is from mesotrophic to eutroph in Spring and is from light eutrophic to middle eutropher in Summer and mesotrophic in Autumn and Winter. There is significant correlation between the nutritional status index and the concentration levels of Microcystins.