| Eutrophication and microcystins (MCs) pollution have become the mainenvironmental problems of plain reservoirs currently, which are related to people’shealth and sustainable development of social economy. In this paper, Jihongtanreservoir was chozen as representative of plain reservoirs. Eutrophication and MCspollution of Jihongtan reservoir were systematically studied. The study has importantmeaning for Qingdao city supply water security. The comprehensive eutrophicationinvestigations and experiments were conducted from three aspects, including physicaland chemical index of water quality, phytoplankton index and sediment nutrients. Atthe same time, a solid phase extraction-high performance liquid chromatography(SPE-HPLC) method for MCs detection was optimized and applied to the detection ofMCs in Jihongtan reservoir. The main research contents and results were as follows.(1) Historical data of Jihongtan reservoir were collected. Based on the physicaland chemical index data(2000-2009) and phytoplankton index data(2006-2010), thereservoir water characteristics were studied. The results showed that: watertemperature (T), pH value, transparency (SD) and total phosphorus (TP) concentrationmet the class Ⅱstandard of the surface water and had less interannual changes, whiletotal nitrogen (TN) concentration changed obviously. In the past two years, TN andchlorophyll a (Chla) concentration showed an upward trend. There were86species ofphytoplankton in Jihongtan reservoir, which belonged to60genera. The dominantspecies were diatoms, cyanophytes and cryptomonas. The phytoplankton cell densityvaried from0.12×106-9.01×106cells/L and the trend of its change was fall>summer> winter> spring. Shannon-Weaver diversity index ranged from1to3.(2) From June2010to September2011, the spatial variation and seasonalvariation of water quality were monitored. The results show that: T, pH, potassiumpermanganate index (CODMn), TP and Chla concentration were higher in summer andautumn than in winter and spring. The dissolved oxygen (DO) and TN concentrationwere higher in winter and spring than in summer and autumn. T, CODMn, TN, and Chla concentration were the highest in the outlet of Jihongtan reservoir and the lowestin the inlet, which was opposite to DO concentration. T, pH, DO and CODMndecreased with increase of the water depth. The survey of sediment showed thatnitrogen and phosphorus concentrations in sediment were low, and phosphorusmainly existed in the form of Ca-P. The content of sediment nutrients release was low.Algae growth potential experiment showed that phosphorus was the limit nutrientfactor of the reservoir.(3) The solid phase extraction-high performance liquid chromatography(SPE-HPLC) method for MCs detection was optimized and used for the detection ofMCs in Jihongtan reservoir. The results showed that: the average MCs concentrationin the reservoir was0.078μg/L, which was below the limit of MCs concentration indrinking water standard. The level of MCs pollution in Jihongtan reservoir was low.(4) Using the physical and chemical index, biological index and comprehensiveindex analysis method, eutrophication assessment showed that the nutrition level ofthe reservoir was middle. The correlations between Chla concentration,Shannon-Weaver index, MCs concentration and physical and chemical index of waterquality were respectively studied by SPSS software. The results indicated that: thecorrelations between Chla and TN, DO and SD were significantly negative, and thatbetween Chla and T, TP and CODMnwere significantly positive; Shannon-Weaverdiversity index was significantly positive correlated with T and negative correlatedwith TN; the correlations between MCs and T, DO, CODMn, TP and Chla werepositive, and that between MCs and TN was significantly negative. T, TN and TPwere important factors of eutrophication and MCs pollution in Jihongtan reservoir.Finally, eutrophication and MCs pollution prevention measures for Jihongtanreservoir were put forward. |
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