Strawn Daniel G
Department of Soil and Water Systems, University of Idaho, Moscow, ID, 83844-2340, USA.
Geochem Trans. 2018 Apr 2;19(1):10. doi: 10.1186/s12932-018-0055-6.
Arsenic is a non-essential element that poses risks in many environments, including soil, groundwater, and surface water. Insights into the environmental biogeochemistry of As can be gained by comparing As and P reaction processes. Arsenic and P are chemical analogues, and it is proposed that they have similar chemical behaviors in environmental systems. However some chemical properties of As and P are distinct, such as redox reactions, causing the biogeochemical behavior of the two elements to differ. In the environment, As occurs as either As(V) or As(III) oxyanions (e.g., AsO or AsO). In contrast, P occurs predominantly as oxidation state five plus; most commonly as the orthophosphate ion (PO). In this paper, data from four published case studies are presented with a focus on P and As distribution and speciation in soil. The goal is show how analyzing P chemistry in soils can provide greater insights into As reaction processes in soils. The case studies discussed include: (1) soil developed from shale parent material, (2) mine-waste impacted wetland soils, (3) phosphate-amended contaminated soil, and (4) plants grown in biochar-amended, mine-contaminated soil. Data show that while P and As have competitive reactions in soils, in most natural systems they have distinct biogeochemical processes that create differing mobility and bioavailability. These processes include redox reactions and rhizosphere processes that affect As bioavailability. Results from these case studies are used as examples to illustrate how studying P and As together allows for enhanced interpretation of As biogeochemical processes in soils.
砷是一种非必需元素，在包括土壤、地下水和地表水在内的许多环境中都存在风险。通过比较砷和磷的反应过程，可以深入了解砷的环境生物地球化学。砷和磷是化学类似物，有人提出它们在环境系统中具有相似的化学行为。然而，砷和磷的一些化学性质是不同的，例如氧化还原反应，这导致这两种元素的生物地球化学行为有所差异。在环境中，砷以五价砷（As(V)）或三价砷（As(III)）含氧阴离子（如亚砷酸根离子或砷酸根离子）的形式存在。相比之下，磷主要以正五价氧化态存在；最常见的是正磷酸根离子（PO）。本文介绍了四个已发表的案例研究数据，重点关注土壤中磷和砷的分布及形态。目的是展示分析土壤中的磷化学如何能更深入地了解土壤中砷的反应过程。所讨论的案例研究包括：（1）由页岩母质发育而来的土壤，（2）受矿山废弃物影响的湿地土壤，（3）添加磷酸盐的污染土壤，以及（4）生长在添加生物炭的矿山污染土壤中的植物。数据表明，虽然磷和砷在土壤中有竞争反应，但在大多数自然系统中，它们具有不同的生物地球化学过程，从而导致不同的迁移性和生物有效性。这些过程包括影响砷生物有效性的氧化还原反应和根际过程。这些案例研究的结果被用作示例，以说明同时研究磷和砷如何能够增强对土壤中砷生物地球化学过程的解释。
