| The lake eutrophication pollution is very heavy all around China. It will lead cyanophytato reproducing greatly, which will further release Microcystins (MCs) to water. People’shealth will be severely threatened by MCs since they drink the polluted water. However, thereis not a controllable reference standard to prevent and restrain the damage of MCs. Therefore,for the sake of the safe drinking water in Lake Taihu basin, it is significantly important toinvestigate the distributions of MCs and eutrophication factors and their relationship in orderto obtain the standard threshold of Chl-a.Water samples were collected and analyzed from Lake Taihu, Lake Gehu, Lake Sanjiu,Lake Changdanghu, Lake Yuandanghu, Lake Yangchenghu, Lake Chenghu and LakeKunchenghu in2013.06to2013.10and2013.12in this work. The distributions of threeintracellular and extracellular microcystins isomers (MC-LR, MC-RR, MC-YR) and differentphysical and chemical factors, including TN, TP, Chl-a, SD, CODMn, water temperature andso on, were conducted in this study. The relationship between microcystins and physical andchemical factors were also analyzed. Then the standard threshold of Chl-a is investigatedbased on the limit values of MC-LR, MCs in drinking water and the relationship betweenMC-LR, MCs and Chl-a.The results are obtained as follows：（1） MCs can be detected in all eight lakes in Taihu Basin by means of Solid phaseextraction and high performance liquid chromatography-tandem mass spectrometry.MCs ishighest in Lake Taihu and Lake Gehu, the next is Lake Sanjiuhu, the lowest is LakeKunchenghu and Lake Chenghu. The highest MCs locates Meiliang Bay and Zhushan Bay inLake Taihu, and the concentration is as high as264.55ug/L, while the lowest MCs locatesLake Xuhu and Southern Lake area. The distributions of eutrophication factors are similar tothat of MCs. The eutrophication factors, especially TP and Chl-a affect the concentration ofMCs significantly in Lake Taihu basin. The spatial distributions of Chl-a, TP and CODMnagree well with MCs in Lake Taihu. The intracellular MCs all around the Lake Taihu area ismainly in the form of MC-LR, while extracellular MCs in Lake Taihu and Lake Gehu ismainly in the form of MC-RR.（2）The temporal variation tendency of MCs is similar to that of eutrophication factorsbetween Lake Taihu and Taihu basin.Total intracellular MCs increases from June to August, and reaches the highest values in October in a very high speed,13.97ug/L and7.46ug/L.Specifically, the intracellular MCs of September in Taihu basin is a little lower than that ofAugust while it is opposite in Lake Taihu, but the difference is very small. And then decreasesthe lowest in December. As for the intracellular MCs，the concentration of MC-LR is highestwhile MC-YR is lowest in every month. Extracellular MCs is highest in July and October, thenext are August and September, the lowest month is June. And extracellular MCs is mainly inthe form of MC-RR in every month. It is found that the eutrophication factors especially TPand Chl-a affect the temporal variation tendency of MCs in some degrees.（3）Correlation analysis shows that the eutrophication factors in Lake Taihu and Taihubasin have good correlation relation with MCs. Various MCs shows very positiverelationships with TN, TP, CODMnand Chl-a (P<0.01), and the correlation coefficientsbetween various MCs and TP,Chl-a are very high. In addition，various extracellular MCsshows very positive relationships with pH、PO43--P (P<0.01), while they shows negativecorrelation with NH4+-N(P＜0.05) in Lake Taihu Basin.（4）The range of Chl-a standard threshold in Taihu basin is17.96-26.6mg/m3, and it is10.15-14.68mg/m3in Lake Taihu. In order to keep the water safe in Taihu basin, theconcentrations of TP, TN, CODMnshould be mainly restrained, and the concentrations ofChl-a should be no more than14.68mg/m3. And MCs pollution is very heavy in summer andautumn, so the monitoring effects and frequency should be reinforced in Lake Taihu and LakeGehu in order to have a certain forewarning function to prevent the MCs pollution so thatsome corresponding protection measures can be taken. |
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