Department of Plant and Soil Sciences, University of Delaware, Newark, DE 19716, United States.
Department of Plant and Soil Sciences, University of Delaware, Newark, DE 19716, United States; School of Environmental Science and Engineering, Nanjing University of Information Science & Technology, Nanjing, Jiangsu 210044, PR China.
Sci Total Environ. 2021 Oct 20;792:148353. doi: 10.1016/j.scitotenv.2021.148353. Epub 2021 Jun 8.
Eutrophication in coastal water has compromised ecosystem services. Identification of phosphorus (P) sources and their load contributions are required for the development of effective nutrient management plans. In this research, multi-isotope proxies were applied to track P sources and evaluate their relative contributions in Love Creek, a coastal estuary in Delaware. The isotope values of carbon (ca. -22‰), nitrogen (ca.+6‰), and phosphate oxygen (ca.+18‰) of agricultural soils under different agricultural practices are generally similar even though their concentrations are distinctly different from forest soils (δC: ca. -27‰; δN: ca.+2‰; δO: ca.+22‰). Comparison of these parameters among potential land sources (agricultural soils, forest soils, septic wastes, and plant debris) and sink (colloids in water) revealed that the plant debris and soils from forest sources are likely dominant sources of P in freshwater sites. The contribution of terrestrial P sources gradually decreased along the salinity gradient and agricultural soil sources gradually dominanted in the saline water portion of the creek. The variations of P loads due to weather-related discharge, changing land use and activities, and seasons were high and reflected the limitation of accurate estimation of sources. Overall, these results provide improved insights into potential sources and biogeochemical processes in the estuary, which are expected to be useful for water quality monitoring programs.
沿海水域富营养化已经损害了生态系统服务。为了制定有效的营养物管理计划，需要确定磷 (P) 的来源及其负荷贡献。在这项研究中，应用多同位素示踪剂来追踪 P 来源，并评估它们在特拉华州沿海河口洛夫克里克的相对贡献。尽管不同农业实践下的农业土壤的浓度与森林土壤明显不同（δC：约-27‰；δN：约+2‰；δO：约+22‰），但其碳（约-22‰）、氮（约+6‰）和磷酸盐氧（约+18‰）的同位素值大致相似。在潜在的陆地来源（农业土壤、森林土壤、化粪池废物和植物残渣）和汇（水中胶体）之间比较这些参数后发现，植物残渣和森林来源的土壤可能是淡水地点磷的主要来源。由于与天气有关的排放、土地利用和活动的变化以及季节等因素，陆地磷源的贡献逐渐沿着盐度梯度减少，而农业土壤源在小溪的咸水部分逐渐占主导地位。由于天气相关排放、土地利用和活动变化以及季节等因素引起的磷负荷变化较大，反映了对来源的准确估计的局限性。总的来说，这些结果提供了对河口潜在来源和生物地球化学过程的深入了解，这有望对水质监测计划有用。
