As and Sb are more labile and toxic to water spinach (Ipomoea aquatica) in recently contaminated soils than historically co-contaminated soils

Abstract

Elevated concentrations of As and Sb impact environmental quality and human health. In this study total and bioavailable As and Sb were measured from recently and historically contaminated soils and the phytotoxicity of these soils was evaluated with Ipomoea aquatica (35-d exposure from germination) using biomass, length of plant tissues and photosynthetic efficiency. As and Sb were both present within the soil (co-contaminated). The bioavailable As and Sb in soils were determined by a Sequential Extraction Procedure (SEP) and compared to total soil concentrations and bioaccumulation in the edible parts of I. aquatica. For both As and Sb, bioavailable concentrations increased proportionally with the total soil concentrations and greater bioavailability in recently contaminated soil was observed. Tissue dry mass and length drastically reduced with increasing total and SEP-bioavailable As and Sb soil concentrations. The total soil concentration was a less sensitive measure of the phytotoxicity of As and Sb than the bioavailable fraction. Shoot length was inhibited by 50% (EC50) at bioavailable As concentrations of 80-96 mg kg-1 in both recently and historically contaminated soils; however, bioavailable Sb EC50 for shoot length was achieved at lower bioavailable concentrations, 96 (42-219) and 12 (7-19) mg kg-1 in recently contaminated soils and historically contaminated soils, respectively. Shoot biomass was inhibited by 50% (EC50) at bioavailable As concentrations of 11 (4-30) and 49 (37-65) mg kg-1 in recently and historically contaminated soils, respectively whereas this occurred at much lower bioavailable Sb concentrations, 2-5 mg kg-1 in both recently and historically contaminated soils. Aging is important in contaminated soils, it decreases the lability of As and Sb and hence their bioavailability to agricultural plants, thus posing a lower risk of exposure of these metalloids to humans through agricultural plants grown in contaminated soils.

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

“…The physical and chemical properties—soil pH, particle size, soil moisture (percentage), total organic matter (TOM; percentage), total Kjeldhal nitrogen (TKN; milligrams per kilogram), and sodium bicarbonate (Olsen) extractable phosphorus (milligrams per kilogram) were measured before starting the bioasays using the methods outlined in Egodawatta et al (2018; Supplemental Data, Table S1).…”

“…Arsenic (As) and antimony (Sb) often co‐occur and are commonly found in plants grown in contaminated agricultural soil near Sb‐mining sites (Casado et al 2007; Mestrot et al 2016; Egodawatta et al 2018). Furthermore, some agricultural fields have become contaminated by the improper disposal of industrial wastes, the application of pesticides and fertilizers, wastewater irrigation, spillage of petrochemicals, and atmospheric deposition (Dahal et al 2008; Wuana and Okieimen 2011).…”

Mitigation of Arsenic Accumulation in Crop Plants Using Biofertilizer

“…The difference observed between length of plants in cultivated group was not signi cant. The study of Egodawatta et al (2018) has shown a poor relationship between both length and biomass (in root and shoot) of water spinach and exposure to As concentration under 100 mg/kg in natural contaminated soils. Codling (2014) has also reported an insigni cant reduction in lettuce yield when lettuce is cultivated in naturally As-contaminated soil (133-153 mg As/kg).…”

An investigation into the use of Australian native plants and designer metal-binding particles for remediation of metal-contaminated landscapes

“…Also, after the addition of metal to a soil, its availability decreases with time, usually because of micropore diffusion, cavity entrapment, occlusion in solid phases by co-presipitation and co-flocculation, surface precipitation or crystal growth (Ma et al, 2006a). Egodawatta et al (2018) claimed that bioavailability of As and Sb depends on soil properties, total soil metalloid concentrations and incubation time, and that percentage of As and Sb bioavailability in historically contaminated soils (~34 years) was <10%…”

“…Zn was mostly present in an exchangeable fraction but it decreased over time, with 45% of Zn being remobilized into stronger binding sites after 63 days of aging. As a result, in experiments in which metals have been recently added to soils, the availability of metal is greater than in those in which the metals have aged for some period (Sauve, 2002, McBride and Cai, 2016, Egodawatta et al, 2018.…”