湖北四湖流域农田排水沟渠水质评价

WATERQUALITY EVALUATION OF AGRICULTURE DRAINAGE DITCHES IN FOUR LAKES REGION OF HUBEI PROVINCE

选取湖北省四湖流域14个农田排水沟渠和总干渠上3个关键节制闸及干渠出口作为样本点,利用GPS进行定点采样测试,分析EC、pH、DO、COD、TN和TP6项水质指标。采用单因子污染指数法判别沟渠水体的主要污染负荷类型,同时利用内梅罗指数法与模糊综合评判法进行评价分级,以期了解该流域水质现状与水环境空间变化特征。结果表明,DO和TN是水体中的主要污染因子,流域内78.57%的排水单元沟渠水体处于轻度污染状态,其中42.86%的沟渠水体已达到《地表水环境质量标准》(GB3838-2002)中Ⅳ类水质级别,污染比较严重。排水单元污染程度由强至弱的排列顺序为:监利段(D03～D07)>洪湖以北(D08～D09)>洪湖西(D10～D12)>江陵、潜江段(D01～D02)>大同湖地区(D13～D14)。总体来说,总干渠水质好于农田排水单元沟渠水质,中区排水单元沟渠水质要劣于下区。

In this study,water samples from fourteen agriculture drainage ditches as well as from three critical check gates,two outlets of main channel of four lakes region in Hubei Province were collected and examined with six physicochemical parameters:electrical conductivity(EC),pH,dissolved oxygen(DO),chemical oxygen demand(COD),total nitrogen(TN),and total phosphorus(TP).Global positioning system(GPS)was used to determine the coordinates of sampling points.In order to identify the main pollution loading types of ditch water,the single factor pollution index was applied.Moreover,Nemero Index and the fuzzy comprehensive evaluation were used to judge the water quality grades,and then to characterize the water quality situation and the spatial variation features of water environment in this basin.The results indicated that DO and TN were the main polluting factors.And the proportion of agriculture drainage ditches in slight pollution was about 78.57%,among which 42.86% points reached up to the standard requirement of classⅣin《Surface Water Environment Quality Standard》(GB3838-2002).This showed that the ditches were heavily polluted.The changing intensity of water pollution in agriculture drainage ditches was Jianli section(D03～D07)>the northern area of Honghu(D08～D09)>the west of Honghu county(D10～D12)>Jiangling and Qianjiang section(D01～D02)>the area of Datong Lake(D13～D14).In summary,the water quality in main channel was much better than that in agriculture drainage ditches,the middle area was worse than the inferior segment in the aspect of water quality of agriculture drainage ditches.