莱州湾东岸地下水硝酸盐空间变异特征研究

应用经典统计学和地统计学对莱州湾东岸地下水NO3-质量浓度进行分析,采用Kriging方法对未观测点进行估值,分析研究区不同区域NO-3质量浓度的空间变异特征。同时,利用地理信息系统与Surfer软件分析研究区土地利用类型和NO-3质量浓度之间的关系。结果表明:1)莱州湾东岸地区地下水NO3-质量浓度平均值为118.51mg/L,变异系数为0.80,表现为中等强度变异;2)研究区地下水NO-3质量浓度的变异函数理论模型符合高斯模型,块金值/基台值为41.5%,表现为中等程度的空间相关性;3)不同土地利用类型中,耕地地下水中硝酸盐质量浓度平均值(136.09 mg/L)最高,其次是城镇用地(89.15 mg/L),水产养殖区(30.32 mg/L)最低,其中耕地超标率为81.25%,城镇用地超标率为76.92%,水产养殖区均未超标。农业生产过量使用化肥和城镇生活中的生活生产废水大量排放是造成地下水硝酸盐质量浓度过高的主要原因。而水产养殖区由于受人类生活、生产与耕作影响较少,地下水硝酸盐质量浓度相对较低。

On the spatial nitrate concentration variations in the groundwater of the eastern coast of Laizhou Bay

This study is intended to present the research results of our analysis of the NO-3 concentration variation in the east coast of Laizhou Bay by means of classical statistics and geostatistics.The paper has also investigated the spatial variations of the NO-3 concentration in different spots of the above said area in hoping to evaluate the situation concerned of the non-observational areas with Kriging method.At the same time,we have also jointly applied the geographic information system with the surfing software to an analysis of the relationship between the concentrations of nitrate and the land use types in the area under study.The results of our research reveal that:(1) the average concentration of NO-3 in the eastern coast of Laizhou Bay is 118.51 mg/L with the coefficient of variation being 0.8,which can be regarded as a result of moderate-intensity variation.(2) The theoretical variogram model of the groundwater nitrate concentration in the area is a Gaussian model with its nugget/sill of 41.5%,which indicates a medium spatial correlation.(3) In different types of land use,the average content concentration of nitrate proves to be different.The content of nitrate in the farmlands has been found maximal with a value of 136.09 mg/L;the variation order was followed by the urban land,whose average content is 89.15 mg/L;and the content with the aquaculture areas proves to be weakest,only 30.32 mg/L.Of different land use types,the farmland(81.25%) is found with excessive content rate of nitrate concentration,whereas the rate in urban land is 76.92%,except for the aquaculture areas.Comparing the above findings with the specific circumstances of the study area,we have found that the excessive uses of agricultural fertilizers in the farmlands and large amounts of wastewater emission in the urban areas are the main causes leading to the high nitrate content in the groundwater.For example,the nitrate content in the groundwater is found relatively low in aquaculture areas,because of the less impact of human activities on the daily life,production and farming.Thus,it can be concluded that there exists a very closely relation between the groundwater nitrate concentration and land use type.