渭河关中段典型支流非点源污染监测与负荷估算

Monitoring and load estimation of non-point source pollution on typical tributaries in the Guanzhong reach of the Weihe River

2009年,对渭河关中段3条典型支流泾河、沣河和灞河进行了洪水期和非洪水期水质水量同步监测,水质监测指标包括COD、DP、TP、NH4+-N和TN.根据监测结果及水文站实测流量资料,分别采用水文分割法和平均浓度法对各条支流的非点源污染负荷进行了计算,分析了非点源污染的特点.结果表明:①3条河流洪水期间各指标的平均浓度基本都大于平时的平均浓度;②各指标浓度峰基本超前于流量峰或与流量峰同时到达;负荷输移速率峰基本上与流量峰同时到达,符合地表径流的初期效应规律;各指标非洪水期浓度变化总体上小于洪水期浓度变化幅度,量级较大的洪水水质变化幅度相对较小;③水文分割法和已被检验并被广泛采用的平均浓度法计算结果吻合良好,说明该法可用于有限资料条件下非点源污染负荷的估算;两种方法计算结果的平均值显示,非点源污染在3条河流水污染中均占较大比重,其对水质的影响不容忽视;④3条河流年污染负荷以汛期负荷为主,汛期污染负荷以非点源污染负荷为主;⑤从3条河流综合情况看,污染物年总负荷中,43%COD、75%DP、83%TP、64%NH4+-N、47%TN来源于非点源污染.

The water quality of the Weihe River is heavily affected by non-point source pollution（NSP） from its tributaries.To quantify NSP loading from its major tributaries we monitored both water flow and water quality of three tributaries,Jinghe River,Fenghe River and Bahe River,in the Guanzhong reach of the Weihe River during the flooding and non-flooding periods in 2009.Measured water quality factors included COD,dissolved orthophosphate,TP,NH＋4-N and TN.NSP loadings were computed using two methods：hydrological division and mean concentration.The results indicate that：①the mean concentrations were higher during the flooding period than during non-flooding periods.②The peak pollutant concentrations occurred either before or at the same time as the flow peaks;the peak load transport rates appeared at the same time as the flooding peaks,which was in accordance with the natural process of initial ground surface flushing;the variations of pollutant concentrations were smaller during the non-flooding periods than during the flooding periods,and bigger floods had smaller variations in pollutants concentrations than smaller floods;③ The results using the hydrological division method were in good agreement with the well tested and widely used mean concentration method,and this indicated that the hydrological division method can be used to estimate NSP loading when limited data is available.The mean values from both methods showed that NSP accounts for a significant proportion of pollution for the three rivers,which cannot be ignored.④In terms of annual pollutant loading,most of it occurred during the flooding periods.⑤NSP accounts for a majority of the total annual pollutant loading,i.e.,43% of the COD,75% of the dissolved orthophosphate,83% of the TP,64% of the NH＋4-N and 47% of the TN.