长江中下游平原升金湖流域硝酸盐来源解析及其不确定性

The contribution rates of nitrate sources and their uncertainties in Shengjin Lake Basin,middle and lower reaches of the Yangtze River Plain

考虑流域地理特征的空间分异,以升金湖流域人口/农业集约区大渡口(DDK)与森林子流域唐田河(TTH)为研究区,利用贝叶斯同位素混合模型分别解析这2个子流域硝酸盐来源的贡献率,并分析其不确定性.研究表明:(1)地下水中,DDK、TTH硝酸盐均主要来源于粪便/污水,贡献率可达65%以上,粪便/污水通过土壤下渗导致地下水硝酸盐富集.(2)地表水中,DDK硝酸盐主要来源于化学肥料,贡献率约为56%;而TTH主要来源于土壤,贡献率为44%;化肥和粪便/污水在DDK的贡献率要高于TTH.(3)无论是地表水还是地下水,贡献率大的硝酸盐来源,其不确定性较大,这与流域土地利用方式、生活污染源以及土壤理化特性等因素的空间差异有关.

Considering the spatial differentiation of geographical characteristics in the basin,the population/agricultural intensive watershed(DDK)and a forest sub-watershed(TTH)in Shengjin Lake Basin selected as study areas,Bayesian isotope mixed models is used to analyse the contribution rates and uncertainties of potential nitrate sources in surface water and groundwater.For the groundwater type in the basin,nitrate in DDK and TTH are mainly comes from manure and sewage,with the contribution rate more than 65%,which is caused by the infiltration of manure and sewage through soil.For the surface water type,nitrate in DDK mainly comes from chemical fertilizer,with a contribution rate of 56%,while that in TTH mainly comes from soil with a contribution rate of 44%.The contribution of chemical fertilizer and manure and sewage in DDK is significantly higher than that that in TTH.Whether for surface water or groundwater,the nitrate sources with the larger contribution rate have greater uncertainties,which are related to spatial differentiation in factors such as land use patterns,domestic pollution sources,and soil physicochemical characteristics.