河流沉积物重金属潜在生态风险及其空间分异——以黄河包头段为例

Potential Ecological Risk and Its Spatial Variance of Heavy Metals in River Sediments:A Case Study on the Baotou Section of the Yellow River

以黄河包头段干、支流的6个站位0～20cm柱状沉积物为例,计算了分层位的重金属潜在生态风险指数,并对其进行地统计学分析和K riging插值重建,以此揭示研究尺度上潜在生态风险的空间分异。结果表明,几乎所有的层位都发生了轻微和轻微以上生态风险,排污支流站位F的风险达到中等乃至强;各站位间重金属垂向潜在生态风险在空间上有较大的变异;其中空间自相关引起的空间变异占主导地位,表明各站位重金属潜在生态危害整体的垂向空间分布结构性相对较强;空间变异比与相关尺度的对应揭示出随机部分引起的空间异质性越高,则空间自相关尺度越小;阐明了潜在风险空间分异现实存在性和进行分层计算潜在生态风险指数的必要性。

Spatial variability of heavy metals co-pollution is one of the foci in the field of water quality researches in recent years. Geostatistics is a branch of applied statistics, and used for randomness and structure of regionalized variable in ecology, soil, agriculture and environment research broadly. Spatial variability and spatial correlation of heavy metals potentially ecological risk in river column sediments were assessed in this paper.Four main river ways (A1, B1, C1, D) and two branches stations (E, F) were selected in the Baotou Section of the Yellow River, and 6 column sediments about 20 cm were taken from these stations, each column sediment was divided into 10 layers by 2 cm in the sampling spots. The concentrations of copper, lead, zinc and cadmium in sediments (<63 μm) were measured by AAS according to Tessier method, and the potential ecological risk indexes (RI) of the heavy metal were calculated at different depths. The spatial variability of the RI was calculated by semivariogram analysis and kriging interpolation by the software of GS+5.1.The results showed that light or lighter ecological risk in the stations occurred in almost all layers, and the ecological risk of the F station was medium or even serious. The spatial variability of potential ecological risk in vertical section was biggest in the research scale, with the order A1 < E < D < B1 < C1 < F, suggesting the disturbanceof the exotic heavy metals. The variability caused by spatial autocorrelation was dominant, which illustrated that the structure of potential ecological risk in vertical section was relatively strong in the stations. The mutuality of spatial variance proportion and correlation scale showed that the higher of the spatial heterogeneous caused by random section, the lower of the scale of the spatialautocorrelation. There existed spatial variability of the potential ecological risk and it was necessity to calculate the RI for different depths.