浑河流域地表水和地下水氮污染特征研究

通过分析浑河流域地表水、地下水中主要离子和不同形态氮含量,探讨了水体中水化学组成特点、各形态氮污染水平与分布特征,并采用综合指数法对流域浅层地下水水质进行了评价.结果表明,地表水水型从上游到下游由Ca-HCO3型转变为Ca-SO4型.NO3--N浓度由1.06mg/L增至6.13mg/L,NO2--N和NH4+-N仅在中游和下游地表水中检出,表明地表水在流域中下游地区受到的人为影响强烈;地下水沿流动方向水型由Ca-HCO3型依次演进为Ca-SO4和Ca-Cl型.NO3--N的含量(0.62~23.47mg/L)明显高于其在地表水中的含量.局地土地利用类型(林地、旱地、城镇用地、水田)对附近地表水体NO3--N浓度影响不显著,而旱地与水田地下水中NO3--N浓度存在显著差异,旱地地下水NO3--N浓度最高.浅层地下水质量评价结果显示流域浅层地下水总体质量一般,NO3--N超出背景值1.4倍,中游地区NO2--N和NH4+-N污染严重,达到Ⅳ类水标准.地下水中ORP、DO、Cl-浓度和各形态氮组成特征表明由于反硝化作用,中下游地区地下水中NO3--N浓度逐渐降低,而NO2--N浓度上升到0.041mg/L.

Characteristics of nitrate in surface water and groundwater in the Hun River Basin

Hydrogeochemistry and nitrate pollution characteristics in surface water and groundwater of the Hun River basin were investigated by analyzing concentrations of the main ions and nitrogen. The results showed that the water types of the surface water changed from Ca-HCO3 to Ca-SO4 along the river while it varied from Ca-HCO3、Ca-SO4 to Ca-Cl in shallow groundwater. Concentrations of NO3--N in the surface water were increased to 6.13mg/L from the initial 1.06mg/L. However, the NO2--N and NH4+-N were only detected in the middle and lower Hun River. These results indicated that the surface water was significantly affected by anthropogenic activities. Concentration of NO3--N in groundwater was evidently higher than that in surface water. There were no significant differences of NO3--N content in surface water samples of the four land-use types (forest land, dry land, urban land and paddy field). However, significant difference for NO3--N levels in shallow groundwater were found between dry land and paddy field. Serious pollution of NO3--N, NO2--N and NH4+-N were found in shallow groundwater. In general, most of shallow groundwater samples showed medium water quality. The denitrification might exist in the shallow groundwater of the middle and lower areas based on variations of ORP, DO, Cl- and nitrate concentrations showing the content of NO3--N was decreased gradually and increase of NO2--N concents.