基于集成分析的环渤海地区河流硝酸盐污染解析

近几十年全球人口剧增,粮食生产及燃料消耗都增加了地表水中的氮负荷,而地表水是连接大陆氮库和海洋氮库的重要通道,地表水中的硝酸盐的增加将直接导致河口及沿海硝酸盐浓度的增加,因此研究近海河流的氮污染情况、确定影响因素将会为近海营养物质的控制及水环境管理提供重要信息.以环渤海地区的入海河流为主要研究对象,通过收集公开数据建立环渤海地表水硝酸盐数据库集成分析,研究入海河流的水体硝酸盐的时空污染特征及其与各影响因素之间的关系.结果表明,环渤海区域地表水中硝酸盐浓度的变化范围在0.0~76.4 mg·L~(-1),与溶解氧、总氮、总磷和电导率有显著的相关关系(p=0.01).在空间变化方面,黄河下游及浑太河上游流域硝酸盐污染较为严重.在除去来自城市污废水排放的人工河道带来的硝酸盐浓度异常值后,丰水期(平均浓度4.55 mg·L~(-1))与平水期(平均浓度5.39 mg·L~(-1))的硝酸盐浓度的平均水平较枯水期(平均浓度4.03 mg·L~(-1))更高,且浓度的变化范围(丰水期:0.00~34.90 mg·L~(-1);平水期:0.00~31.00 mg·L~(-1))亦大于枯水期(0.00~25.64 mg·L~(-1)).影响因素方面,硝酸盐浓度与降水量有显著相关性(r=0.122,p=0.01).土地利用相关性研究表明耕地与建设用地是硝酸盐的主要来源,林地和草地对硝酸盐污染有改善作用.硝酸盐的入海通量约为33.4×10~4t·a-1.

River nitrate pollution in the Bohai Rim region based on the integrated analysis

With the world''s population escalating in recent years, food production and fuel consumption have greatly impacted the nitrogen load in rivers. River system plays a vital role in linking terrestrial nitrogen pool with oceanic nitrogen pool, since the continuous increasing nitrogen will directly lead to excessive nitrate increment in estuaries and coastal waters. Therefore, to find out the current condition of the nitrogen pollution and to identify the impact factors in the Bohai Rim region which is affected deeply by human activities can provide crucial information for us to controlling the input of nutrient and monitoring aquatic environment. The rivers in the Bohai Rim region were selected in this study to establish a database for integral analysis. The results showed that nitrate concentration in surface water varied from 0 to 76.4 mg·L^-1, and has significant correlation with dissolved oxygen, total nitrogen, total phosphorus, and electrical conductivity (p=0.01). For spatial variation, the lower reaches of the Yellow River and the upper reaches of the Huntai River Basin had more serious nitrate pollution. The nitrate concentration during normal and high flow period were higher and varied in a larger range (normal period:0~31.00 mg·L^-1; high flow period:0~34.9 mg·L^-1) than its during low flow period (0~25.64 mg·L^-1). In regard to impact factors, there is significant correlation between nitrate concentration and precipitation (r=0.122,p=0.01). Agricultural (r=0.332,p=0.01) and construction land (r=0.194,p=0.01)showed significantly positive effect on nitrate pollution, indicating that these land use types were main nitrate sources. While the forest(r=-0.279,p=0.01) and grass (r=-0.15,p=0.05) have significantly negative correlation with nitrate concentration, suggesting that these types contributed to water quality improvement. Nitrate flux flowing into the Bohai Sea is estimated at 33.4×10⁴ tons/yr.