Study On Benthic Diatoms Ecological Characteristics And Control Effect Of Filter Dam To Polluted Water In Wujiang River Upstream(Cengtai Town In Bijie City)

Wujiang River is the longest river in Guizhou Province, it is an importanttributary of Yangtze River. The water quality of Wujiang river have a greatsignificance to people’s life and health along the two rivers. This study choosea river(a tributary of the Wujiang river upstream)originated from CengtaiTown as research object, and use engineering filter dam method to purify thepolluted river.The study try to explore the purifying effect of filtering dam tothe polluted river through dynamic monitoring of physical and chemicalindexes of water and diatoms taxa.The sand filter dam is builded in this river, the study set three samplepoints before and after dam respectively, collect water samples and benthicdiatom samples regularly.The diatom are identified334species, belonging to2classes,6orders,10families,26genera. Correlation analysis betweendiatom abundance and physical and chemical factors show total nitrogen(TN)is the main factor affecting diatom abundance. Shannon-Weaver Index isslightly higher after filtering during monitoring period, which show thecomplexity of the diatom community before filtering is slightly higher thanfiltered; Simpson Index is higher after filtering. The changes of MotilityIndex of Diatoms (M) show the organic pollution is decreased after filtering.Diatom index (GI) is greater after filtering in the first four months, but thesituation is reversed in November and December, so the filter material need toelutriate. The filtering efficiency of turbidity, CODMn, TN in turn is turbidity(42.3%), CODMn(15.8%), TN (13.3%). The change trend of TP and PO43-isnot obvious. NO2-N content is accumulated from month to month, and thecumulative trend is increase after September. ORP rise before October butdecrease in November and December post-filtering.Hg concentration exceed the Environmental Quality Standards forSurface Water(GB3838-2002), belongs to Ⅳ-Ⅴc lass. Hg concentration anddiatom abundance has certain correlation.The changes of Diatom index (GI), NO2-N and ORP show that filteringeffect of the dam become worse in later period. So it is suitable to elutriationfilter material per run7months.