长江口海域表层沉积物中磷的形态分布及环境意义

Distributions and Environmental Implications of the Phosphorus Forms in the Surface Sediments from the Changjiang Estuary

用分级浸取的方法对2009年2月采自长江口海域27个表层沉积物样品中P的形态和相关环境特征进行了研究。结果表明,物质来源和沉积物粒度是各形态P的含量与分布的主要控制因素。Ex-P（可交换态磷）,Fe-P（铁结合态磷）,Al-P（铝结合态磷）,Lea-OP（可浸取有机磷）和CFA-P（自生钙磷）5种形态的沉积磷在适当条件下均可被释放参与P的再循环（可再循环磷）,占总磷的15%-43%。其中贡献最大的是Fe-P,占可再循环磷45.5%,其他形态-的贡献由大到小依次是Al-P〉CFA-P〉Ex-P〉Lea-OP。单因子污染评价显示长江口沉积物中可再循环磷向水体释放的生态风险较小。沉积物总铁与总磷比（TFe∶TP）和BD（碳酸氢钠—连二亚硫酸钠）浸取相铁磷比（BD-Fe∶BD-P）分别高于27和20,表明沉积物吸附磷的铁氧化物位点过量,沉积物仍有较强的保留P的能力和潜力。这揭示了水体磷存在向沉积物转移的趋势,且沉积磷释放造成水体富营养化的风险很低。

Twenty-seven surface sediment samples collected from the Changjiang Estuary in February 2009 were sequentially extracted to study the forms of phosphorus （P） and their ecological risks as internal P sources. It is shown that the content and distributions of P in surface sediments are majorly controlled by the sourses of P and the grain size of sediments. Ex-P （Exchangeable P）, Fe-P （Fe-bound P）, Al-P （Al-bound P）, Lea-OP （Leachable Organic P）, and CFA-P （Authigenic Carbonate Fluoapatie） are transferable phosphorus forms, which could be released from sediments to seawater and return to the biogeochemical cycling. Transferable P accounts for 15- 43% of TP in sediments. Among the transferable P forms, Fe-P is the largest form in content, accounting for 45.5% of total transferable P; and the other forms are in the order of Al-P〉CFA-P〉Ex-P〉Lea-OP. The single factor contaminant index of transferable P indicates low ecological risks of sedimentary P release. The ratios of iron to phosphorus in the sediments （TFe ：TP） and in BD extractant （BD-Fe ： BD-P） are above 27 and 20, respectively. This suggests that the surface sediments have sufficient sorption sites for dissolved P to adsorb onto them, and also have high capacity to retain particulate P in sediments. Consequently, P has the potential to migrate from water to sediment in the Changjiang Estuary, and sedimentary P release has low risks to eutrophication.