Simpson Zachary P, Mott Joshua, Elkin Kyle, Buda Anthony, Faulkner Joshua, Hapeman Cathleen, McCarty Greg, Foroughi Maryam, Hively W Dean, King Kevin, Osterholz Will, Penn Chad, Williams Mark, Witthaus Lindsey, Locke Martin, Pawlowski Ethan, Dalzell Brent, Feyereisen Gary, Dolph Christine, Bjorneberg David, Nouwakpo Kossi, Rogers Christopher W, Scott Isis, Bolster Carl H, Duriancik Lisa, Kleinman Peter J A
USDA-ARS, Sustainable Water Management Research Unit, Stoneville, Mississippi, USA.
USDA-ARS, Soil Management and Sugar Beet Research Unit, Fort Collins, Colorado, USA.
J Environ Qual. 2025 Jul-Aug;54(4):851-869. doi: 10.1002/jeq2.20632. Epub 2024 Sep 29.
The buffering of phosphorus (P) in the landscape delays management outcomes for water quality. If stored in labile form (readily exchangeable and bioavailable), P may readily pollute waters. We studied labile P and its intensity for >600 soils and sediments across seven study locations in the United States. Stocks of labile P were large enough to sustain high P losses for decades, indicating the transport-limited regime typical of legacy P. Sediments were commonly more P-sorptive than nearby soils. Soils in the top 5 cm had 1.3-3.0 times more labile P than soils at 5-15 cm. Stratification in soil test P and total P was, however, less consistent. As P exchange via sorption processes follows the difference in intensities between soil/sediment surface and solution, we built a model for the equilibrium phosphate concentration at net zero sorption (EPC) as a function of labile P (quantity) and buffer capacity. Despite widely varying properties across sites, the model generalized well for all soils and sediments: EPC increased sharply with more labile P and to greater degree when buffer capacity was low or sorption sites were likely more saturated. This quantity-intensity-capacity relationship is central to the P transport models we rely on today. Our data inform the improvement of such P models, which will be necessary to predict the impacts of legacy P. Further, this work reaffirms the position of labile P as a key focus for environmental P management-a view Dr. Sharpley developed in the 1980s with fewer data and resources.
景观中磷（P）的缓冲作用会延迟水质管理的成效。如果磷以不稳定形式（易于交换且具有生物可利用性）储存，它可能很容易污染水体。我们在美国七个研究地点对600多种土壤和沉积物中的不稳定磷及其强度进行了研究。不稳定磷的储量足以维持数十年的高磷流失，这表明了典型的遗留磷的传输受限状态。沉积物通常比附近的土壤对磷的吸附性更强。表层5厘米的土壤中不稳定磷的含量比5至15厘米处的土壤高1.3至3.0倍。然而，土壤有效磷和总磷的分层情况不太一致。由于通过吸附过程进行的磷交换遵循土壤/沉积物表面与溶液之间强度的差异，我们建立了一个模型，用于计算净零吸附时的平衡磷酸盐浓度（EPC），该浓度是不稳定磷（数量）和缓冲容量的函数。尽管不同地点的性质差异很大，但该模型对所有土壤和沉积物都具有良好的通用性：随着不稳定磷含量的增加，EPC急剧上升，当缓冲容量较低或吸附位点可能更饱和时，上升幅度更大。这种数量-强度-容量关系是我们目前所依赖的磷传输模型的核心。我们的数据为改进此类磷模型提供了依据。预测遗留磷的影响，改进这些模型是必要的。此外，这项工作再次强调了不稳定磷作为环境磷管理关键重点的地位——这一观点是夏普ley博士在20世纪80年代利用较少的数据和资源提出的。
