Abstract：
Research in the field of sediment geochemistry suggests potential linkages between catchment processes (land use), internal phosphorus (P) loading and lake water quality, but evidence is still poorly quantified due to a limited amount of data. Here we address the issues based on a comprehensive data set from 27 lakes in southern Finland. Specifically, we aimed at: 1) elucidating factors behind spatial variations in sediment geochemistry; 2) assessing the impact of diagenetic transformation on sediment P regeneration across lakes based on the changes in the vertical distribution of sediment components; 3) exploring the role of the sediment P forms in internal P loading (IL), and 4) determining the impact of IL on lake water quality. The relationship between sediment P concentration and field area percentage (FA%) was statistically significant in (mainly eutrophic) lakes with catchments that included more than 10 % of fields. We found that sediment iron-bound P (Fe-P) increased with increasing FA%, which agrees with the high expected losses from the cultivated areas. Additionally, populated areas increased the pool of sediment Fe-P. Internal P loading was significantly positively related to both sediment Fe-P and sediment organic P (Org-P). However, Org-P was not significant (as the third predictor) in models that had a trophic state variable as the first predictor and Fe-P as the second predictor. Further, the vertical profiles of sediment components indicated a role of diagenetic transformations in the long-term sediment P release, especially in lakes with deeper maximum depth and longer water residence time. Finally, IL was significantly positively correlated to water quality variables including phytoplankton biomass, its proportion of cyanobacteria, chlorophyll a concentration and trophic state index. Our findings suggest that reduction of P losses from the field and populated areas will decrease internal P loads and increase water quality through a reduced pool of Fe-P.
摘要：
沉积物地球化学领域的研究表明，流域过程(土地利用)之间存在潜在的联系，内部磷（P）负荷和湖泊水质，但由于数据量有限，证据量化仍然很差。在这里，我们根据芬兰南部27个湖泊的综合数据集解决了这些问题。具体来说,我们的目标是：1）阐明沉积物地球化学空间变化背后的因素；2）根据沉积物组分垂直分布的变化评估成岩转化对湖泊沉积物磷再生的影响；3）探索沉积物磷形式在内部磷负荷（IL）中的作用，4)确定IL对湖泊水质的影响。在流域超过10％的湖泊（主要是富营养化）中，沉积物P浓度与田间面积百分比（FA％）之间的关系具有统计学意义。我们发现沉积物铁结合P(Fe-P)随着FA%的增加而增加，这与耕地的高预期损失一致。此外,人口稠密的地区增加了沉积物Fe-P。内部P负荷与沉积物Fe-P和沉积物有机P（Org-P）均呈显着正相关。然而,在以营养状态变量为第一预测因子和Fe-P为第二预测因子的模型中，Org-P不显著（作为第三预测因子）。Further,沉积物成分的垂直剖面表明成岩转化在长期沉积物P释放中的作用，特别是在最大深度更深和水停留时间更长的湖泊中。最后,IL与包括浮游植物生物量在内的水质变量显着正相关，它的蓝藻比例，叶绿素a浓度和营养状态指数。我们的发现表明，减少田间和人口稠密地区的磷损失将减少内部磷负荷，并通过减少的Fe-P池提高水质。
