丰台区地下水硝酸盐氮分布特征及生态风险评价

Distribution Characteristics and Ecological Risk Assessment of Nitrate Nitrogen in Groundwater of Fengtai Plain Area

以硝酸盐氮为典型指标,利用多年地下水监测数据及mapGIS和Excel的分析功能,分析地下水硝酸盐氮时空分布特征及变异规律,并尝试采用商值法对其可能给丰台区城市生态系统带来的生态风险进行评价。结果表明,枯、丰水期硝酸盐氮检出浓度普遍较高,浓度分布在空间上呈现出边缘低、中间高的特征,且以南苑西部为中心大致呈同心半椭圆形向西北延展,浓度逐渐降低。6年来硝酸盐氮浓度均值一直较高,从年内变化来看,大多年份丰水期高于枯水期;从年际变化来看,浓度总体呈缓慢下降趋势。6年来,硝酸盐氮枯(丰)水期变异系数均呈上升趋势,大多年份丰水期大于枯水期。硝酸盐氮生态风险水平的空间分布与枯(丰)水期浓度分布大体一致,即从边缘向中间逐步增大。研究区生态系统可能处于较高生态风险水平。

Taking nitrate nitrogen as typical index, based on the groundwater monitoring data for many years and with the help of the mapGIS and Excel, spatial and temporal distribution character and variation pattern in Fengtai are analyzed, possible ecological risk for urban ecological system is evaluated by using quotient method. The results show that detectable concentration of nitrate nitrogen is generally higher and characters of the lower edge and the higher middle are presented, with focus on the west of Nanyuan, it extends in the shape of a concentric semi-oval towards northwest where the concentration gradually decreases. The average nitrate nitrogen concentration has been relatively high in the past 6 years. From the point of view of the change of the year, most of the high water season is higher than the dry season, and from the inter-annual change, the concentration of nitrate nitrogen has a slow downward trend in the past six years. The coefficient of variation of nitrate nitrogen in dry water period showed an upward trend, and in most years, it was larger in high water season than in dry water period. The spatial distribution of the ecological risk level of nitrate nitrogen is roughly consistent with the concentration distribution in the dry water period, that is, increasing gradually from the edge to the middle. The local ecosystem may be in the higher ecological risk level.