Extension of a biotic ligand model for predicting the toxicity of metalloid selenate to wheat: The effects of pH, phosphate and sulphate. (February 2021)

• Record Type: Journal Article
• Authors: Wang, Fangli; Wang, Xuexia; Chen, Qinghua; Song, Ningning
• Is Part Of: Chemosphere. Volume 264(2021)Part 1
• Publication Date: 2021-02
• Subjects: Biotic ligand model (BLM) -- Hexavalent selenium (Se(VI)) -- Toxicity prediction -- Wheat; Pollution -- Periodicals; Pollution -- Physiological effect -- Periodicals; Environmental sciences -- Periodicals; Atmospheric chemistry -- Periodicals; 551.511
• DOI: 10.1016/j.chemosphere.2020.128424
• Languages: English
• ISSNs: 0045-6535

Abstract

Abstract: It has not been well understood that the influences of pH and accompanying anions on the toxicity of selenate (Se(VI)). The influences of pH and major anions on Se(VI) toxicity to wheat root elongation were determined and modeled based on the biotic ligand model (BLM) and free ion activity model (FIAM) concepts. Results showed that EC50[Se(VI)]T values increased from 162 to 251 μM as the pH values increased from 4.5 to 8.0, indicating that the pH increases alleviated the Se(VI) toxicity. The EC50{SeO4 2− } values increased from 133 to 203 μM while the EC50{HSeO4 − } values sharply decreased from 210 to 0.102 nM with the pH increasing from 4.5 to 8.0. The effect of pH on Se(VI) toxicity could be explained by the changes of Se(VI) species in different pH solutions as SeO4 2− and HSeO4 − were differently toxic to wheat root elongation. The toxicity of Se(VI) decreased with the increasing activities of H2 PO4 − and SO4 2− but not for NO3 − and Cl − activities, indicating that only H2 PO4 − and SO4 2− had competitive effects with Se(VI) on the binding sites. An extended BLM was developed to consider effects of pH, phosphate and sulphate, and stability constants of SeO4 2−, HSeO4 −, H2 PO4 − and SO4 2− to the binding sites were obtained: log K S e O 4 B L = 3.45, log K H S e O 4 B L = 5.98, log K H 2 P O 4 B L = 2.05, log K S O 4 B L = 1.85. Results implied that BLM performed much better than FIAM in the wheat root elongation prediction when coupling with toxic species SeO4 2− and HSeO4 −, and the competitions of H2 PO4 − and SO4 2− for the binding sites while developing the Se(VI)-BLM. Highlights: SeO4 2− and HSeO4 − were the two main toxic species contributed to Se(VI) toxicity. HSeO4 − had a greater binding affinity than SeO4 2− . Se(VI) toxicity was described by H2 PO4 − and SO4 2− protection and speciation effect. An extended BLM can predict the Se(VI) toxicity to wheat root elongation.