典型岩溶小流域水体中硝酸盐分布特征及成因:以普定后寨河流域为例

岩溶流域水环境极易受到人为活动的影响，而硝酸盐污染是岩溶流域面临的最突出最普遍的问题之一，把握岩溶流域中硝酸盐的来源及其在不同水体中的分布特征与成因，可为岩溶流域硝酸盐污染的防治提供依据.以贵州普定后寨河流域为研究对象，于2017年5月采集地下水和地表水样品共53件，测定主要水化学参数，分析NO₃-来源，并结合区域土地利用类型，沿流动路径阐明其影响.结果表明，研究区主要阴、阳离子浓度从大到小依次为HCO₃- > SO₄2- > NO₃- > Cl-、Ca2+ > Mg2+ > Na+ > K+，水化学类型以HCO₃-Ca型为主.水体NO₃-的主要来源为化肥，有6个采样点水体明显受到硝酸盐污染，NO₃-浓度变化主要受混合过程控制，硝化作用和反硝化作用影响不明显.流域水体NO₃-浓度受土地利用方式影响明显，流经以农田或村寨为主的区域时NO₃-浓度升高，流经以林地灌木等自然植被繁茂的区域时NO₃-浓度降低. 

Distribution Characteristics and Causes of Nitrate in Waters of Typical Small Karst Catchment: A Case of the Houzhai River Catchment

The water environment of karst catchment is very susceptible to human activities. Nitrate pollution is a prominent and common problem in karst catchment. It is important to clarify the source, distribution characteristics and formation mechanism of nitrate in waters of karst catchment, which can facilitate the nitrate pollution prevention in karst catchment. The Houzhai River catchment of Puding of Guizhou was selected as the study area. 53 samples of groundwater and surface water were collected for measuring water chemical parameters in May 2017. Water chemical parameters were determined for analyzing the NO₃- source. Combined with the land use type, the influence of the nitrate spatial distribution was discussed along the flow path. The results show that the order of ion concentration in waters was Ca2+ > Mg2+ > Na+ > K+, HCO₃- > SO₄2- > NO₃- > Cl- in the study area, respectively. The type of water chemistry was HCO₃-Ca. The main source of NO₃- was the chemical fertilizer. Variations of NO₃- concentration along the flow path were mainly controlled by the mixing process, and the impact of nitrification and denitrification was not obvious. Waters of 6 sampling sites were obviously polluted by nitrate. The concentration of NO₃- in waters of the catchment was obviously affected by the land use pattern. NO₃- concentration increased when waters flowed through farmland or villages, and decreased when they flowed through forest land.