Department of Agricultural Sciences, Faculty of Agriculture and Forestry, University of Helsinki, P.O. Box 27 (Latokartanonkaari 5), 00014, Finland; Chair of Hydrobiology and Fishery, Estonian University of Life Sciences, Kreutzwaldi 5, 51006 Tartu, Estonia.
Freshwater Research, 3421 Hwy 117, Baysville, Ontario P0B 1A0, Canada.
Water Res. 2024 Oct 1;263:122157. doi: 10.1016/j.watres.2024.122157. Epub 2024 Jul 26.
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.
沉积物地球化学领域的研究表明，集水区过程（土地利用）、内部磷（P）负荷和湖水水质之间存在潜在联系，但由于数据有限，证据仍未得到充分量化。在这里，我们基于芬兰南部 27 个湖泊的综合数据集来解决这些问题。具体而言，我们旨在：1）阐明沉积物地球化学空间变化背后的因素；2）根据沉积物成分垂直分布的变化，评估成岩转化对湖泊内部 P 再生的影响；3）探索沉积物 P 形态在内部 P 负荷（IL）中的作用，4）确定 IL 对湖泊水质的影响。在集水区包含超过 10%农田的（主要是富营养化的）湖泊中，沉积物 P 浓度与野外面积百分比（FA%）之间的关系具有统计学意义。我们发现，随着 FA%的增加，沉积物中铁结合磷（Fe-P）增加，这与从耕作区预期的高损失一致。此外，人口稠密地区增加了沉积物 Fe-P 的储量。内部 P 负荷与沉积物 Fe-P 和沉积物有机磷（Org-P）均呈显著正相关。然而，在以营养状态变量为第一个预测因子，Fe-P 为第二个预测因子的模型中，Org-P 不是显著（作为第三个预测因子）。此外，沉积物成分的垂直分布表明成岩转化在长期沉积物 P 释放中起作用，尤其是在最大水深较深和水停留时间较长的湖泊中。最后，IL 与水质变量呈显著正相关，包括浮游植物生物量、蓝藻比例、叶绿素 a 浓度和营养状态指数。我们的研究结果表明，减少农田和人口密集区的 P 损失将减少内部 P 负荷，并通过减少 Fe-P 储量来提高水质。
