汉江上游现代洪水滞流沉积物重金属元素特征

Heavy Metal Characteristics in the Modern Flood Slackwater Deposits in the Upper Hanjiang River Valley

  • 摘要: 年对汉江上游现代洪水SWD(滞流沉积物)系统采样,并分析样品的粒度、烧失量和重金属元素质量分数,以揭示该流域内大洪水期间重金属的面源污染状况. 结果表明:汉江上游现代洪水SWD的粒度成分中,黏粒(粒径<2μm,下同)占1.3%~6.9%,细粉沙(2~<16μm)占9.0%~40.9%,粗粉沙(16~63μm)占22.7%~50.3%,并且三者沿程自上而下逐渐增加;而沙粒(>63μm)占7.1%~65.6%,沿程自上而下呈逐渐减少的趋势. 与全国泛滥平原沉积物重金属背景值比较发现,Co、Cr、Ba和V累积明显,而w(Cu)、w(Ni)、w(Pb)和w(Zn)不同程度地高出背景值. 运用地质累积指数(Igeo)和污染指数(PI)评价表明,主要污染元素的地质累积指数为Co>Cr>Ba>V,而Cu、Ni、Pb和Zn都属于清洁. 汉江上游现代洪水SWD的重金属整体处于中等污染水平. 利用相关性和主成分分析发现,Co和Cr多富集在沙粒中,而Cu、Ni、Pb、Zn、Ba和V多累积在黏粒、细粉沙和粗粉沙中. 现代洪水SWD的粒径分布和重金属元素质量分数空间变化明显,聚类分析发现其空间分布可分为安康盆地、汉江上游北岸和汉江上游南岸3类,这种分布特征与汉江上游地貌特征、羽毛状水系和人类活动的影响等密切相关.

     

    Abstract: Human activities and environment change within river basins can be indicated by the dynamic change of concentrations of heavy metals in the river sediments. Flood slackwater deposits (SWD) are deposited from the suspended sediment load in flood flow and preserved after the flood recession. The fine-grained sediments were produced by soil erosion during the season of storm rain and great flood over the river basin. Modern flood SWD were collected along the main stream after two large floodings which occurred during 2010-2011along the upper Hanjiang River valley. The analytical results showed that the contents of clay(<2μm) ranged from 1.3% to 6.9%. Fine silt (2-<16μm) values varied between 9.0% and 40.9%. Coarse silt (16-63μm) varied between 22.7% and 50.3%. Sand (>63μm) was between 7.1% and 65.6%. Clay, fine silt and coarse silt in modern flood SWD gradually increased, while sand decreased along the upper Hanjiang River valley. Average concentrations of heavy metals Co, Cr, Cu, Ni, Pb, Zn, Ba and V were 49.7,1.7,1.1,7.2,6.1,7.6,7.2,2.4mg/kg, respectively. Concentrations of heavy metals, Co, Cr, Ba and V, were significantly higher than floodplain background values in China. Index of geoaccumulation(Igeo)and pollution index(PI) were applied to assess heavy metals in modern flood SWD. The order of pollution elements were Igeo(Co)>Igeo(Cr)>Igeo(Ba)>Igeo(V), whereas Cu,Ni, Pb and Zn belonged to unpolluted. Concentration of heavy metals accumulated in modern flood SWD were defined as the moderately polluted by pollution index in the upper Hanjiang River. Results obtained from the principal component analysis (PCA) were confirmed by the correlation analysis. Heavy metals Co and Cr were mainly enriched in sand, whereas Cu, Ni, Pb, Zn, Ba and V were rich in clay, fine silt and coarse silt. Cluster analysis (CA) showed that the cluster depend on geographical location of sampling sites locating at Ankang plain, north and south side of Hanjiang River. The upstream of Hanjiang River is the water source area for China''s Middle Route of the South-to-North Water Division Project. These results provide basic physicochemical data for environmental protection and conservation for soil and water in the upper Hanjiang River valley.

     

/

返回文章
返回