山丘河谷平原潜水氮素浓度变化及其与土地利用的相关性

Variations of nitrogen concentration in phreatic water and its correlation with land use patterns in a hilly valley plain

为分析山丘河谷平原地带农业集约化发展条件下地下潜水氮素情况,对浙江长乐江流域河谷平原地带地下潜水以月为单位连续采样分析,研究该地区地下潜水中氮素浓度的季节性动态变化和空间分布情况,并以各个采样点为圆心,分别提取每个样点周围8种半径(50、100、250、500、750、1 0000、1 250、1 500 m)的圆形区域中各类土地利用类型面积,分析不同土地利用类型面积占比与地下潜水中氮素浓度的关系。结果表明,地下潜水中硝态氮(NO_3^--N)浓度总体平均值为(1. 326±0. 618) mg·L^(-1),总氮(TN)浓度总体平均值为(2. 717±1. 614) mg·L^(-1),地下潜水中TN与NO_3^--N浓度的时空变化呈现出高度的一致性,时间分布上两者浓度均在丰水期大于枯水期,空间分布上则从以园地(蔬菜、苗木)和耕地(水稻、油菜)为主要土地利用类型的区域向周边递减。各土地利用类型中,以园地对NO_3^--N和TN浓度值贡献最大。地下潜水中的氨氮(NH_3-N)浓度总体平均值为(0. 434±0. 158) mg·L^(-1),占TN的16%。各监测点丰水期的NH_3-N浓度普遍低于枯水期,并呈现靠近水域的监测点氨氮浓度偏高的趋势。

Based on the monthly groundwater sampling and measurements,the seasonal variations and spatial distributions of nitrogen in ground phreatic water were analyzed in the hilly valley plain of Changle River Watershed,Zhejiang Province,China.The area occupation ratios of different land use patterns were extracted in the areas of different radius(50,100,250,500,1 000,1 250,1 500 m)around each sampling site to investigate the correlation within land use patterns and the corresponding groundwater nitrogen concentration.It was shown that the average concentrations of nitrate nitrogen(NO3^--N)and total N(TN)were(1.326±0.618)and(2.717±1.614)mg·L^-1,respectively.The temporal and spatial distributions of TN concentration in the plain groundwater showed strong consistency with NO3^--N.Both TN and NO-3-N concentrations were higher in wet season than those in dry season,and they were always higher under the land use pattern of gardens(vegetables and seedlings)and cultivated lands(rice and rape)than those in others.The average concentration of NH 3-N in the plain groundwater was(0.434±0.158)mg·L^-1,which was only about 16%of the TN concentration.NH3-N concentrations in groundwater were lower in the wet season than those in the dry season,and it showed an increasing trend nearby the water body(river and pond).