Nicholas School of the Environment, Duke University, Durham, NC 27708, USA.
Department of Crop and Soil Sciences, North Carolina State University, Raleigh, NC 27695, USA.
Sci Total Environ. 2024 Jan 10;907:167863. doi: 10.1016/j.scitotenv.2023.167863. Epub 2023 Oct 28.
Phosphate fertilizers may contain elevated concentrations of toxic metals and metalloids and therefore, their excessive application can result in the accumulation of both phosphorus (P) and metal(loid)s in agricultural soils. This study aims to investigate the occurrence, distribution, and potential plant-availability of metal(loid)s originating from phosphate fertilizer in a long-term experimental field at the Tidewater Research Station in North Carolina, where topsoil (10-20 cm deep) and subsoil (up to 150 cm deep) samples were collected from five plots with consistent and individually different application rates of P-fertilizer since 1966. We conducted systematic analyses of P and metal(loid)s in bulk soils, in the plant available fraction, and in four sequentially extracted soil fractions (exchangeable, reducible, oxidizable, and residual). The results show that P content in topsoils were directly associated with the rate of P-fertilizer application (ρ = 1, p < 0.05). Furthermore, P concentrations were highly correlated with concentrations of Cd, U, Cr, V, and As in the bulk topsoil (ρ > 0.58, p < 0.05), as well as the potential plant-available fraction (ρ > 0.67, p < 0.01), indicating the accumulation of the fertilizer-derived toxic metal(loid)s in the topsoil. Significant correlations (p < 0.001) of metal(loid)s concentrations between the bulk soil and the potential plant-available fraction raises the possibility that P-fertilizer application could increase the accumulation of toxic metal(loid)s in plants, which could increase human exposure. Results from sequential leaching experiments revealed that large portions of the trace elements, in particular Cd, occur in the soluble (exchangeable and reducing) fractions of topsoil with higher P-fertilizer input, whereas the levels of redox-sensitive elements (As, V, U, Cr) were higher in the reducible and oxidizable fractions of the soils. Overall, the data presented in this study demonstrate the effect of long-term P-fertilizer application on the occurrence and accumulation of a wide range of toxic metal(loid)s in agricultural topsoil.
磷肥可能含有较高浓度的有毒金属和类金属，因此，过量施用磷肥会导致农业土壤中磷和金属（类）的积累。本研究旨在调查北卡罗来纳州潮汐研究站长期实验场中来自磷肥的金属（类）的发生、分布和潜在的植物可利用性，该实验场从 1966 年以来，在五个具有一致且单独不同磷肥施用量的地块中，从 10-20 厘米深的表土层和 150 厘米深的底土层中采集了土壤样本。我们对土壤中大量元素和金属（类）的全量、有效态以及四个顺序提取的土壤组分（可交换态、可还原态、可氧化态和残渣态）进行了系统分析。结果表明，表土层的磷含量与磷肥施用量呈直接相关（ρ=1，p<0.05）。此外，磷浓度与全量表土中 Cd、U、Cr、V 和 As 浓度高度相关（ρ>0.58，p<0.05），以及潜在的植物有效态（ρ>0.67，p<0.01），表明肥料衍生的有毒金属（类）在表土层中的积累。大量元素和金属（类）浓度在全量土壤和潜在植物有效态之间的显著相关性（p<0.001）表明，磷肥的施用可能会增加植物中有毒金属（类）的积累，从而增加人体接触的风险。连续浸出实验的结果表明，在高磷肥输入的表土层中，痕量元素，特别是 Cd，大部分存在于可溶（可交换和还原）组分中，而氧化还原敏感元素（As、V、U、Cr）的水平则较高的可还原和可氧化组分中。总的来说，本研究的数据表明，长期磷肥施用对农业表土中多种有毒金属（类）的发生和积累有影响。
