黄河三角洲土壤盐渍化原因分析与生态风险评价

Analysis for Driving Forces and Ecological Risk Assessment of Soil Salinization in the Yellow River Delta

以黄河三角洲为研究区域,选择土壤全盐为标志,以海拔高程、地下水位、地下水矿化度、、灌溉排水状况、土壤有机质和人口密度6个土壤盐渍化主要控制性因子,采用聚类分析方法进行了土壤盐渍化原因分析;基于ArcGIS 9.3和Matlab,选择上述7个要素为评价因子,以归一化植被指数(NDVI)为生态终点,利用灰色关联度方法建立了区域土壤盐渍化的生态风险评价模型,并进行了生态风险评价。结果表明:黄河三角洲土壤盐渍化主要受自然和人为因素驱动,其中地下水位和海拔高程等自然因素是造成研究区土壤盐渍化的自然因素,土壤有机质和人口密度等是人为因素;土壤盐渍化极大和重度风险区域集中分布于黄河三角洲东南沿海区域、西北沿海、东北部的部分地区,该区域受海洋影响强烈,土壤盐渍化面积最大,占到总面积的58%以上;无风险、轻度风险和中度风险区域主要与黄河径流的距离有关,且随着距离增大而风险增加。

Saline soil is a kind of soil which has been influenced by salinity--alkali components with varying degrees of salinity and alkalinity, e. g. , aline soil, alkaline soil and other soils including coastal saline soil and inland saline soil. The formation of soil salinization is closely related to the topography, climate, parental material of soil, groundwater, and human activities, while the secondary soil salinization may occur when regional water and salt migrates under unsuitable conditions. Soil salinization destroys environments of plant growth, makes ecological environment further deteriorate, and increases the difficulty of land use and development. Therefore, it is of great significance to study the distribution, migration and risk assessment of salt and water. Seven indicators, i.e. the elevation, groundwater level, groundwater salinity, total salt content of the soil, thecondition of irrigation and drainage, soil organic matter and population den- sity, were selected as the main driving factors, which were analyzed by means of principal component analysis and cluster analysis methods. By introducing the soil salinization ecological evaluation models, choosing the above seven factors as the evaluation factors, regarding Normalized Difference Vegetation Index index as the ecological endpoint, and taking advantage of ArcGIS and Matlab programming, we established the ecological risk assessment model for soil salinization of the Yellow River Delta and then made the evaluation for the delta by using the model. The results showed that the elevation and the groundwater level were the main controlling factors, and both of them were internal factors in controlling soil salinization. However, human activity factors such as population density and drainage irrigation district were the external factors for the development of soil salinization. The most severe risk areas were mainly located in the southeast and northwest coastal areas and the small parts of the northeast district. Such risk areas were influenced seriously by marine environment and accounted for more than 58% of the total area. And, the norisk, slight-risk and medium-risk areas were co-related to the distance between the areas and the Yellow River run-off, and the risk increased with increasing distance.