Phosphate-enhanced movement of arsenic out of lead arsenate-contaminated topsoil and through uncontaminated subsoil

Abstract

Abstract. Past use of lead arsenate insecticides has resulted in elevated concentrations of lead (Pb) and arsenic (As) in topsoils of many existing and former deciduous tree fruit orchard sites throughout the world. Application of phosphate (PO4)-containing fertilizers to these soils can increase soil As solubility, phytoavailability and downward mobility. A laboratory soil column experiment was conducted to determine if As released by phosphate additions to a topsoil artificially contaminated with lead arsenate (1.65 mmol total Pb/kg; 1.10 mmol total As/kg) would be appreciably resorbed by the underlying uncontaminated subsoil. Treatments were a factorial combination of topsoil amendment with monoammonium phosphate (MAP, 0 or 16.67 mmol POjkg), and amount of leaching ( 1, 5 and I0 pore volume displacements (PVD) with distilled water under saturated flow conditions). Soil As decreased in the topsoil with increasing amount of leaching and increased in the subsoil. Addition of MAP substantially increased loss of topsoil As, promoted As transport into and through the subsoil, and increased dissolved As concentrations in the column leachates. After 10 PVDs, 95% of the initial soil As remained in the -MAP columns, while 56% of the initial soil As remained the +MAP columns. Dissolved Pb concentrations were <0.05 itmol/L in all column leachates. The data are consistent with a mechanism of PO4-enhanced release of As in the topsoil and subsequent promotion of As movement through the subsoil by continuing competition of dissolved As and PO4 for ion adsorption sites. The experimental results indicate that use of PO4-containing fertilizers on lead arsenate-contaminated soils has the potential to greatly enhance downward movement of soil As.

Mitigation of cadmium and arsenic in rice grain by applying different silicon fertilizers in contaminated fields

“…The As concentration in basal fertilizers (NPK) is low (0.03-5.2 mg/kg), suggesting the increase of As in grain is not due to the application of basal fertilizers. The most plausible explanations are (a) the competition between phosphate (PO 4 2− ) originating from the NPK fertilizers and arsenate in the soil may release As into pore water (Peryea and Kammereck 1997;Peryea 1998;Wang et al 2002), leading to increased As bioavailability and higher uptake of As by the plants, or (b) the NPK fertilizers may stimulate microbial activity, which reduces Fe or As in soil, releasing the As adsorbed on the Fe minerals and causing increased availability of As. The addition of rice straw into the soil (NPK+RS) significantly increased the As concentration in rice grain by 12.2 and 26.4 % compared with the NPK and control treatments, respectively.…”

Environmental Impact and Remediation of Residual Lead and Arsenic Pesticides in Soil

“…Arsenic is slightly more soluble and will move through the soil profile (Focus, 2006). Arsenic mobility is enhanced by addition of phosphorus (Peryea & Kammereck, 1997). Arsenic is more mobile compared to lead regardless of the soil type and texture (Eflving et al, 1994).…”

“…Remediation of lead arsenate contaminated soils, however, is more challenging because of (1) the vast amount of lead arsenate contaminated soil throughout the world (Peryea & Kammereck 1997), and (2) some of the common in situ remediation methods that have been proven effective for the remediation of lead contaminated soils result in the release of arsenic from lead arsenate contaminated soil, thereby creating a new environmental problem (Codling, 2007;Peryea 1991b). Phosphate, for example, has been shown to be very effective in sequestering lead in contaminated soils (Chaney & Ryan 1994;Ruby et al, 1994), but this remediation method is not suited for lead arsenate contaminated soil; because arsenate and phosphate exhibit similar physicochemical behavior in soil and compete directly for sorption sites on soil particles, the use of phosphate on a lead arsenate contaminated soil will promote arsenic release from the soil into the soil solution phase, threatening the ground water (Dupanport & Peryea 1991b;Eflving et al, 1994;Peryea & Kammereck 1997;Peryea, 1991). Increasing the number of adsorption sites via the addition of high oxide minerals such as iron and manganese might allow for the resorption of arsenate after its release caused by phosphate competition during lead sequestration.…”

“…Some o f t h e s e p r o d u c t s h a v e b e e n u s e d i n agriculture as defoliants, insecticides, and fungicides to control pests in apple, plum, and peach orchards, turf, vegetable crops, and on cattle. From the late 1800s to about 1947, lead arsenate was the most commonly used insecticide for control of codling moth in deciduous tree fruit orchards in countries throughout the world, including the USA, Australia, Canada, New Zealand, England, and France, because of its low cost, high efficiency, and low phytotoxicity (Focus, 2006;Kammereck, 1997 andShepard, 1951). The wide use of lead arsenate significantly increased its annual production during the early 1900s.…”

Arsenic Addition to Soils from Airborne Coal Dust Originating at a Major Coal Shipping Terminal

“…The significance of this additional As to human and/or environmental health in southeastern Virginia is currently unknown. However, application of phosphorous-rich fertilizers to these soils, many of which are overlain by lawns, could potentially lead to the mobilization of the added As in Norfolk soils (e.g., Peryea and Kammereck 1997). Furthermore, a recent study demonstrated that children playing in playgrounds with chromated copper arsenate treated wooden playground structures or with sand that has come in contact with such structures, acquire more soluble As on their hands compared to children not exposed to such structures or the associated sand (Kwon et al 2004).…”