长江北支口门圆陀角附近潮滩沉积物重金属来源及污染评价

Sources and Pollution Assessment of Heavy Metals in the Sediments of the Tidal Flat at the Yuantuojiao Point, the North Branch, Changjiang River

基于圆陀角附近潮滩YY孔岩芯重金属(Co、Cr、Cu、Mn、Ni、V、Zn)富集系数和人为贡献率、地累积指数和潜在生态风险系数,讨论了圆陀角附近潮滩重金属来源及污染。结果表明,重金属Co、V平均含量显著高于背景值。除Cr是自然来源外,其它6种重金属受自然和人为来源的影响,且以自然来源为主。7种重金属总体无污染,仅Co、Cu、V和Zn在岩芯132 cm处出现无污染至中度污染。7种重金属潜在生态危害属轻微水平。值得关注的是,1997年之后,重金属Co、Cr、Mn、V、Zn地累积指数和潜在生态风险系数均有增加的趋势。

The North Branch, separated by the Chongming Island, was once the main channel in the estuary of the Changjiang River. The human reclamation and the south migration of the main channel led to the narrowing and shallowing of the North Branch. Yuantuojiao Point is the intersecting point of the North Branch of the Changjiang River with the South Yellow Sea coastal line. The specific geographic location and the complexity of regional morphological dynamics developed a typical silt-mud tidal fiat. Heavy metals contents of the tid- al-fiat sediments recorded rich information of the coastal environmental changes near the Yuantuojiao Point. In this study, the heavy metals sources and pollution evolution were discussed according to the heavy metals con- tents within the tidal-flat sediments at the Yuantuojiao Point. A drilling core of 218 cm was collected on the salt marsh at the Yuantuojiao Point. The grain size and 7 heavy metals （Co, Cr, Cu, Mn, Ni, V, Zn） of the YY core were measured. The chronology of this core was built by using the 137Cs dating. The correlation analysis, enrich- ment coefficient, human contribution rate, geo-accumulation index, and potential ecological risk coefficient of the heavy metals from the YY core were calculated. The results show the contents of heavy metals were lower after 1960, but were higher before 1960. The average content of V was significantly higher than the background and the content of Co is higher than the background for more than 100%. The average content of 7 heavy metals was most obviously higher than the background value at the depths of 132 cm of the YY core. The content of 7 heavy metals had a good relationship with grain size, indicating of the obvious ＂grain size control effect＂, and the heavy metals might have more coherent sources. The human contribution rates of 7 heavy metals from the sediments further proved that Cr was completely influenced by natural sources, the other 6 heavy metals con- tents were co-affected by the natural and artificial sources, but the natural source was still the main one. Accord- ing to the environmental quality standard, the sediments are of no pollution for most heavy metals, but the sedi- ments of the depths of 132 cm in the YY core were of free to moderate pollution for Co, Cu, V and Zn. The po- tential ecological risk level of 7 heavy metals was mild. However, the potential ecological risk coefficient and geo-accnmulation index was higher before 1960 than that of after 1960. It is worthy to note that geo-accumula- tion index and potential ecological risk coefficient of 5 heavy metals （Co, Cr, Mn, V, and Zn） of the YY core show an increasing tendency after 1997. The accelerated accumulation of heavy metals at the Yuantuojiao Point should be paid attention. And the emission of heavy metals with larger toxicity coefficient should be reduced.