Phosphorus cycle and its influencing factors in different areas of Lake Taihu

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为进一步了解人类活动及环境因子对太湖磷污染的贡献，揭示磷在太湖不同介质中的迁移转化规律，本文以太湖主要入湖湖区竺山湖、西部沿岸区、南部沿岸区和主要出湖湖区东太湖为对象，调查了表层水、上覆水、间隙水和沉积物中总磷(TP)分布的概况，分析了不同介质中磷的交换特征及其影响因素. 结果表明，表层水和上覆水TP浓度基本相当，平均值均为0.10 mg/L，上覆水和间隙水TP差异较大，间隙水平均浓度约为上覆水的7倍，表层沉积物TP含量为474~2160 mg/kg. 在本研究水域中，TP具有较强的沉积物吸附特性，沉积物作为“汇”的特征明显强于其“源”的特征，且磷的留存能力高度依赖于铁浓度. 空间分布上，入湖湖区磷污染程度明显高于出湖湖区，竺山湖和西部沿岸区存在较大的底泥污染释放风险，但竺山湖外源污染影响较内源污染更加突出，应列为当前太湖磷治理重点关注的区域，建议以控源截污作为竺山湖周边区域的治理重点. 西部沿岸区需注重外源和内源污染同步控制. 南部沿岸区周边区域需妥善处理好未来经济发展与废水排放负荷的关系.;This paper explores the influences of human activities and environmental factors to phosphorus (P) loadings in Lake Taihu, and further reveals the migration and transformation patterns of P across different mediums. To this end, the total phosphorus (TP) distribution characteristics were firstly investigated in surface water, overlying water, pore water and sediments, and further, the TP exchange characteristics and its influencing factors were analyzed, taking the main inlet-lake-areas such as the Zhushan Bay, the western coastal area, the southern coastal area, and the main outlet-lake-area of East Lake Taihu as study objects. The TP concentrations in surface water and overlying water was basically equivalent in those study areas, with an average concentration of 0.10 mg/L. Whereas, TP concentrations between the overlying water and the pore water showed large differences: the average TP concentration in pore water reached seven times of that in the overlying water. The TP content of surface sediment was about 474-2160 mg/kg. In those study areas, TP tended to be adsorbed into sediments rather than to be released from sediments, and the characteristics of sediments as sink were obviously stronger than those as source. Also, the P retention capacity was found highly dependent on iron concentrations. Spatially, the degree of P pollution in the inlet-lake-areas was significantly higher than that in the outlet-lake-areas. Main inlet-lake-areas, e.g., Lake Zhushan and the western coastal area showed greater potential risks of TP release from the sediments. However, external P input was still more prominent than that of internal P loading for Lake Zhushan; thus, measures such as source control and pollution interception should be highlighted for those areas. Whilst, for the western coastal area, apart from the external P loading reduction, the potential risks of internal P loadings should also be concentrated. Additionally, for the surrounding region of the southern area, the relationship between future economic development and wastewater discharge loading should be comprehensively considered and properly handled.