Changes in Sedimentary Phosphorus Burial Following Artificial Eutrophication of Lake 227, Experimental Lakes Area, Ontario, Canada
Changes in Sedimentary Phosphorus Burial Following Artificial Eutrophication of Lake 227, Experimental Lakes Area, Ontario, Canada
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DOI：
10.1029/2020jg005713
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发表时间：
2020-08
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通讯作者：
D. O'Connell;N. Ansems;R. Kukkadapu;D. Jaisi;D. Orihel;B. Cade‐Menun;Yongfeng Hu;J. Wiklund;R. Hall;H. Chessell;T. Behrends;P. Cappellen
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作者：
D. O'Connell;N. Ansems;R. Kukkadapu;D. Jaisi;D. Orihel;B. Cade‐Menun;Yongfeng Hu;J. Wiklund;R. Hall;H. Chessell;T. Behrends;P. Cappellen
加拿大安大略实验湖区的227号湖自1969年开始施磷，导致其从贫营养状态迅速转变为富营养状态。从含氧的上层水层收集的沉积物岩心，和这个独特的湖泊的缺氧的下层水层包含一个历史记录的沉积物磷的形态和掩埋率的变化在整个营养过渡。为了阐明这些变化，化学提取的结果与210 Pb沉积物测年，31 P NMR，穆斯堡尔和XANES光谱相结合。在1969年之前，有机磷（P_2O_3）是227湖主要的沉积磷汇。湖泊的富营养化与总P（TP）的埋藏率以及NaHCO 3可提取P库（腐殖结合P，PHum）的相对贡献显著增加相一致。自人工施肥开始以来，PHum和Pd 3共同占沉积物中总P埋藏量的70%以上。PHum级分可能包含具有腐殖物质的磷酸盐复合物。磷和铁（Fe）提取的NaHCO 3之间的强线性相关性意味着这两个元素的腐殖酸部分的密切关联。穆斯堡尔和XANES光谱进一步表明，1969年后沉积物中的大多数Fe仍处于Fe（III）氧化态，这归因于有机质对可还原Fe的稳定性，部分原因是通过形成磷酸盐-Fe（III）-腐殖酸复合物。重要的是，我们的研究结果表明，227湖的富营养化实验造成了一个大型水库的活性沉积物P，这可能会继续燃料内部P负荷的水柱一旦人工施肥终止的积累。
Lake 227 of the Experimental Lakes Area (ELA) in Ontario, Canada, has been fertilized with phosphorus (P) since 1969, which resulted in a rapid transition from oligotrophic to eutrophic conditions. Sediment cores collected from the oxygenated epilimnion, and the mostly anoxic hypolimnion of this unique lake contain a historical record of the changes in sediment P speciation and burial rates across the trophic transition. To elucidate these changes, results of chemical extractions were combined with 210Pb sediment dating, and with 31P NMR, Mössbauer, and XANES spectroscopies. Prior to 1969, organic P (POrg) was the major sedimentary P sink in Lake 227. Eutrophication of the lake coincided with marked increases in the burial rate of total P (TP), as well as in the relative contribution of the NaHCO3‐extractable P pool (humic‐bound P, PHum). Together, PHum and POrg account for ≥70% of total P burial in the sediments deposited since artificial fertilization started. The PHum fraction likely comprises phosphate complexes with humic substances. The strong linear correlation between P and iron (Fe) extracted by NaHCO3 implies a close association of the two elements in the humic fraction. Mössbauer and XANES spectra further indicate that most Fe in the post‐1969 sediments remained in the Fe (III) oxidation state, which is attributed to the stabilization of reducible Fe by organic matter, in part via the formation of phosphate‐Fe (III)‐humic complexes. Importantly, our results show that the eutrophication experimentation of Lake 227 caused the accumulation of a large reservoir of reactive sediment P, which may continue to fuel internal P loading to the water column once artificial fertilization is terminated.