Abstract：
Anthropogenic activities could significantly increase nutrients loading, especially phosphorus (P), into aquatic systems, leading to eutrophication and disturbance of ecosystems. Detailed investigation of P cycling and its controlling factors in modern lakes could help understand mechanisms behind eutrophication, thus provide suggestions for future environmental management. Here, we investigate evolution history of P and iron (Fe) cycling over the last ∼300 years in west Chaohu Lake, a typical eutrophic lake in East China. The combination of 210Pb-137Cs dating and elemental analysis demonstrates drastic escalation of P input and organic carbon burial since 1960s, coincided with the rapid growth of human population near this region. P phase partitioning data indicate that Fe-bound P (PFe) is the predominant P pool of sediments in Chaohu Lake, which also regulates the evolving trend of reactive P (Preac). Moreover, the highest fraction of PFe is consistent with observations via P K-edge X-ray absorption near edge structure (P XANES). In addition, Fe speciation results show a principal contribution of Fe (hydr)oxides (Feox) and negligible presence of pyrite, suggesting a generally oxygenated depositional environment, where P could be preferentially sequestrated in sediments in association with Fe oxide minerals. Relatively high molar organic carbon/organic P (Corg/Porg) but low Corg/Preac ratios also support limited recycling of Preac in west Chaohu Lake. This study reveals that human activities play an important role in leading to the eutrophication of Chaohu Lake. Future environmental management could utilize the coupling of P and Fe oxides to remove P from water column.
摘要：
人为活动可以显着增加养分负荷，特别是磷（P），进入水生系统，导致富营养化和生态系统的干扰。对现代湖泊中磷循环及其控制因素的详细调查可以帮助理解富营养化背后的机制，从而为今后的环境管理提供建议。这里,我们调查了巢湖西部近300年磷和铁（Fe）循环的演化史，中国东部典型的富营养化湖泊。210Pb-137Cs测年和元素分析的结合表明，自1960年代以来，磷输入和有机碳埋藏急剧增加，恰逢该地区附近人口的快速增长。P相分配数据表明，Fe结合的P（PFe）是巢湖沉积物的主要P库，这也调节了反应性P(Preac)的发展趋势。此外，PFe的最高分数与通过PK边缘X射线吸收近边缘结构（PXANES）的观察结果一致。此外,铁形态结果表明，铁（氢）氧化物（Feox）的主要贡献和黄铁矿的存在可忽略不计，表明通常是含氧的沉积环境，其中P可以优先与氧化铁矿物结合在沉积物中。相对较高的摩尔有机碳/有机P（Corg/Porg）但较低的Corg/Preac比也支持了巢湖西部Preac的有限回收利用。本研究揭示了人类活动在导致巢湖富营养化过程中起着重要作用。未来的环境管理可以利用P和Fe氧化物的耦合从水柱中去除P。
