Review of interactions between phosphorus and arsenic in soils from four case studies

Abstract

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., AsO43− or AsO33−). In contrast, P occurs predominantly as oxidation state five plus; most commonly as the orthophosphate ion (PO43−). 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.

Desorption of Arsenic from Calcareous Mine Affected Soils by Phosphate Fertilizers Application in Relation to Soil Properties and As Partitioning

“…In fact, from lowest to highest P rate, equilibrium pH values were ranged between 7.4 and 6.5 and 7.0 and 6.3 for soils 1 and 2 respectively, while the corresponding pH values for the initial solutions were ranged between 5.3 and 4.1. The alkaline pH of the soils and the oxidizing conditions indicate that As predominantly occurred as arsenates and this would not substantially change under the experimental conditions of this study [9]. Comparable to our results are the findings reported by Singes-Pastor et al [32], even though the initial solutions pH values were neutral or alkaline due to the different P treatments used by these authors.…”

“…Stock solutions of varying phosphates concentrations were prepared by dilution of appropriate amounts of commercial triple superphosphate fertilizer (0-46-0) (TSP) in deionized water ( (9) examined the effects of P amendments on As mobilization using P sorption isotherm experiments with a wide range of P concentrations from 0.098 to 198 mg L −1 . Prior to dilution, TSP particles pulverized, and multiple tests were run to determine TSP solubility in deionized water alone and in the presence of 0.01 M NaNO 3 .…”

“…In the soil environment, As is found in two distinct chemical species: (i) Arsenite as a hydroxyl species (H 3 AsO 3, H 2 AsO 3 − ) and (ii) arsenate as an oxyanion (H 2 AsO 4 −1 or HAsO 4 −2 ) [9]. Arsenates and phosphates chemical behavior is considered as similar regarding either biological processes, such as uptake by plants and incorporation in micro-organisms cells, or their interaction with soil constituents as they compete for available sorption sites [10,11].…”

Influence of Soil Phosphate on the Accumulation and Toxicity of Arsenic and Antimony in Choy Sum Cultivated in Individually and Co-contaminated Soils

“…The main factors controlling As and Sb mobility and speciation are soil redox potential, pH, and the presence of competitive ions such as phosphate (PO 4 3− ). The oxyanions of P(V) and As(V) have tetrahedral structures and display very similar physical and chemical behaviors under aerobic environments (Strawn 2018). As a result, PO 4 3− and arsenate (AsO 4 3− ) compete for the same soil sorption sites, which can result in an increased As bioavailability (Anawar et al 2018).…”

Frontiers and advances in environmental soil chemistry: a special issue in honor of Prof. Donald L. Sparks

“…In addition, Cade-Menun et al [9] and Hamilton et al [10] investigate the fate and transport of phosphate as a nutrient in soil systems by using inductively coupled plasma spectroscopy, P-nuclear magnetic resonance, and X-ray absorption spectroscopy. Strawn et al provide a nice review that discusses phosphorus and arsenic in soil using four case studies [11]. Nickel, zinc, and copper in soils are trace transition metals and critical nutrients as well.…”