城市重污染河流水质特征分析——以皂河为例

皂河是西安市的重点排污和泄洪河流,除了点源污染外,还在一定程度上受到非点源污染的影响。因此,有必要对其水质特征进行研究。2010年4月至2011年11月,对西安市皂河进行了多次水质水量监测,分析了城市重污染河流的污染特征,计算了皂河下游控制断面草滩监测站的非点源污染负荷及构成。结果表明：①皂河污染物SS、COD、TP、NH3-N、NO3-N和TN浓度均超出地表水Ⅴ类标准;②草滩断面洪水期间各指标的平均浓度基本都小于平时的平均浓度;③上游至下游：COD浓度呈逐渐增加的趋势,TP、NH3-N和TN浓度呈现先增加后减小的趋势,NO3-N浓度变化不大,重金属污染物中Cr含量最高,平均浓度从上游到下游呈逐渐增加的趋势;④洪水过程中,非点源污染负荷均小于点源,SS、COD、TP、NH3-N、NO3-N和TN的非点源污染负荷比重依次为：14%,2.0%,5.1%,6.0%,7.4%和4.2%;⑤目前西安市皂河污染治理的重点仍然是点源污染,但非点源污染对水质的影响不容忽视。

Analysis on water quality of severely polluted urban river,Zaohe River as an example

The Zaohe River is a river in Xian city for waste water discharge and flood discharge.Its water is contaminated by point source pollution(PSP) and to some extent,also by non-point source pollution(NSP).To quantify water quality in this river,we monitored water flow and water quality at a control section of Caotan station from Apr.,2010 to Oct.,2011,including contents of COD,TP,NH3-N,NO3-N and TN.The results are summarized as follow.1) At Caotan,the concentrations of SS,COD,NH3-N,NO3-N and TN exceeded those in the surface water quality standard V,and the mean concentrations in flood periods were lower than those in non-flood periods.2) The pollutant concentrations at Caotan were lower in flood periods than non-flood periods.3) From upstream to downstream along the river,the COD concentration was increasing,the total phosphorus,ammonia nitrogen and total nitrogen were increasing first and then decreasing,while the change in nitrate nitrogen was little.The content of Cr among heavy metals was the highest and its mean concentration took an increasing trend along the river.4) In flood periods,NSP load was lower than PSP load,and the NSP load ratios of SS,COD,TP,NH3-N,NO3-N and TN were 14%,2.0%,5.1%,6.0%,7.4% and 4.2%,respectively.5) At present,PSP issue of the Zaohe River remains a focus of pollution control,but NSP should not be ignored.