Nutrient losses from Mississippi watersheds degrade downstream water bodies. As forested floodplains intercept agricultural drainage waters, a limiting nutrient like phosphorus (P) could potentially be sequestered in forest soils, reducing P loss to the Gulf of Mexico. Thus far, the role of temperate deciduous floodplain soils for P has not been extensively investigated in the Midwestern United States. The objective of this study was to investigate the buffering capacity of P in floodplain soils using soil biochemical chemical assays, 31P nuclear magnetic resonance spectroscopy (NMR) and P K-edge X-ray absorption near edge structure spectroscopy (XANES). Phosphorus reaction dynamics were compared between floodplains and surrounding upland soils in east-central Illinois, USA. Total organic P was significantly greater in the floodplain (277.27 ± 159.51 mg kg−1) than that in the upland (113.04 ± 74.88 mg kg−1), illustrating its buffering capacity. Notably, microbial biomass P (averaged 13.08 mg kg−1) was greater in the floodplain than that in the upland. The results of 31P NMR analysis showed the presence of organic P (e.g., orthophosphate monoesters) and orthophosphate. The P K-edge XANES analysis shows that these inorganic and organic P species are predominantly adsorbed in calcite and precipitated as calcium phosphate in floodplain soils. These findings suggest that temperate deciduous floodplain soils have a great potential to immobilize agricultural P in the Upper Mississippi watershed.

中文翻译：

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美国伊利诺伊州温带漫滩土壤中农业磷的固定化

密西西比流域的养分损失使下游水体退化。由于森林漫滩拦截农业排水，磷（P）等限制性营养物质可能会被隔离在森林土壤中，从而减少向墨西哥湾的磷流失。到目前为止，温带落叶漫滩土壤对磷的作用尚未在美国中西部进行广泛调查。本研究的目的是使用土壤生化化学分析、31P 核磁共振光谱 (NMR) 和 P K 边缘 X 射线吸收近边缘结构光谱 (XANES) 来研究泛滥平原土壤中 P 的缓冲能力。比较了美国伊利诺伊州中东部的漫滩和周围高地土壤之间的磷反应动力学。漫滩中的总有机磷显着更高 (277.27 ± 159. 51 mg kg-1) 比高地 (113.04 ± 74.88 mg kg-1) 高，说明其缓冲能力。值得注意的是，洪泛区的微生物生物量 P（平均 13.08 mg kg-1）大于高地。31P NMR分析的结果表明存在有机P（例如，正磷酸单酯）和正磷酸。P K-edge XANES 分析表明，这些无机和有机 P 物质主要吸附在方解石中，并在漫滩土壤中以磷酸钙的形式沉淀。这些发现表明，温带落叶漫滩土壤具有很大的潜力来固定密西西比河上游流域的农业磷。31P NMR分析的结果表明存在有机P（例如，正磷酸单酯）和正磷酸。P K-edge XANES 分析表明，这些无机和有机 P 物质主要吸附在方解石中，并在漫滩土壤中以磷酸钙的形式沉淀。这些发现表明，温带落叶漫滩土壤具有很大的潜力来固定密西西比河上游流域的农业磷。31P NMR分析的结果表明存在有机P（例如，正磷酸单酯）和正磷酸。P K-edge XANES 分析表明，这些无机和有机 P 物质主要吸附在方解石中，并在漫滩土壤中以磷酸钙的形式沉淀。这些发现表明，温带落叶漫滩土壤具有很大的潜力来固定密西西比河上游流域的农业磷。