南四湖支流东鱼河水质时空分布特征与水质评价

Spatial and temporal distribution characteristics and water quality evaluation of Dongyu River, a tributary of Nansihu Lake

为了解南四湖支流东鱼河水质的时空分布特征,本文在2017年7月自上游至入湖河口设定6个采样点采集上覆水,测定营养盐和重金属的浓度,并对东鱼河2008—2017年入湖河口上覆水进行水质评价。结果表明,2017年东鱼河上覆水中重金属及NO;浓度符合目标水质标准,COD_(Mn)、TP、F;和TN均存在不同程度地污染,其中TN污染状况最为严重。从空间分布特征来看,COD_(Mn)和TP的变化趋势相似。TN除D3—D4变化较大,其余均在4~7 mg/L之间。F;呈上升趋势,D1和D6相差3.87倍。COD_(Mn)和TP主要污染来源为农业生产;TN的主要污染来源为水生动植物及其残体;F;的主要污染来源为农业生产及高氟区的影响。从时间分布特征来看,COD_(Mn)单因子指数2009年最大,2015年最小;TP指数基本在0.4~1.35之间,仅2016年为4.15,受降雨量影响较大。TN指数2010年最小,2013年最大,受温度影响较大。内梅罗指数在2016年达到峰值后又在2017年显著降低,主要原因是政府在汛期前做好防洪除涝的准备,有效减缓了河道水土流失现象。由上述可知,重视农业排污问题,及时对水生生物进行打捞,并在汛期前做好防洪除涝的工作是改善东鱼河水质的关键。

In order to understand the temporal and spatial distribution characteristics of water quality of Dongyu River, a tributary of Nansihu Lake, six sampling sites were set from the upstream to the estuary in July 2017 to collect the overlying water, determine the concentrations of nutrients and heavy metals, and evaluate the water quality of the overlying water of Dongyu River from 2008 to 2017. The results showed that the concentrations of heavy metals and NO;in the overlying water of Dongyu River in 2017 met the target water quality standards. COD_(Mn), TP, F;and TN polluted the river to varying degrees, and TN pollution was the most serious. From the spatial distribution characteristics, the changing trends of COD_(Mn)and TP were similar each other. Except d3-d4 and TN which varied greatly, the remains varied between 4 and 7 mg/L. The F;concentration showed an upward trend, and the difference between D1 and D6 was 3.87 times. The main pollution sources of COD_(Mn)and TP were agricultural production. The main pollution sources of TN were aquatic animals and plants and their residues. The main pollution sources of F;were agricultural production and the impact of high fluorine areas. In terms of time distribution characteristics, COD_(Mn)single factor index was the largest in 2009 and the smallest in 2015. TP index varied basically between 0.4 and 1.35, which was only 4.15 in 2016. This index was greatly affected by rainfall. TN index was the smallest in 2010 and the largest in 2013, which is greatly affected by temperature. After reaching the peak in 2016, the Nemero index decreased significantly in 2017, mainly because the government made good preparations for flood control and waterlogging before the flood season, which effectively slowed down the phenomenon of water and soil loss in the river. It can be seen from the above findings that the key to improving the water quality of Dongyu River is to pay attentions to the problem of agricultural sewage discharge, salvage aquatic organisms in time, and do a good job in flood controlling and waterlogging removal before flood season.