Risk assessment of using phosphate and calcium fertilisers for continuously flooded rice cultivation in a soil co-contaminated with cadmium and antimony

Abstract

Antimony (Sb) pollution is causing serious concerns in some regions globally, such as around the XiKuangShan mine in China, which is the largest Sb mine in the world. However, remediation measures are scarce. In this study, we assessed the effects of two fertilisers, sodium dihydrogen phosphate (NaH2PO4 at 200, 500 and 2000 mg kg−1) and calcium chloride (CaCl2 at 20, 80 and 200 mg kg−1), on uptake by rice (Oryza sativa L.) of Sb, cadmium (Cd) and arsenic (As) from contaminated soil under flooded conditions. Despite a very low soil As concentration (10.89 mg kg−1), the results showed that flooded conditions will result in excess accumulation of As in rice grains. NaH2PO4 generally enhanced the release of As and Sb by increasing pH and competitive adsorption in the soil, which resulted in their accumulation in many tissues of the rice plants. NaH2PO4 (200 mg kg−1) significantly reduced soil available Cd concentration by increasing soil pH, which resulted in a decrease in Cd concentration in the roots and husks. CaCl2 at 200 mg kg−1 decreased soil pH, and CaCl2 treatments increased the available Sb concentration, although not as much as NaH2PO4. Both NaH2PO4 and CaCl2 enhanced the formation of root iron plaques, and in many cases increased the concentrations of As, Cd and Sb in the root plaques, suggesting a storage role rather than a barrier of root iron plaques for plant uptake of As, Cd and Sb. CaCl2 at 200 mg kg−1 was the most effective treatment for reducing As, Sb and Cd concentrations in rice grains. We conclude that utilisation of fertilisers containing P on a soil co-contaminated by Sb and Cd poses a risk of Sb and As accumulation under continuous flooded conditions, whereas addition of CaCl2 at 200 mg kg−1 may control As, Sb and Cd accumulation in grains of rice plants under these conditions.

<i>In-situ</i> Stability and Remediation of Typical Antimony (Sb) Tailings by Combined Solid Waste in Southwest China

“…The fixation of As and Sb is mainly controlled by the formation of Ca-As and Ca-Sb precipitates [31,32]. As and Ca can precipitate CaHAsO 4 and Ca 3 (AsO 4 ) 2 at stable and moderate pH [33]. This is consistent with the best stabilization effect of As and Sb in treatment group 5 when pH is neutral.…”

Soil ridging combined with biochar or calcium-magnesium-phosphorus fertilizer application: Enhanced interaction with Ca, Fe and Mn in new soil habitat reduces uptake of As and Cd in rice

“…Soil in-situ amendments such as biochar (Rehman et al, 2017), and calcium-magnesium-phosphate (CMP) fertilizers (Jiang et al, 2022;Shi et al, 2022) are effective for Cd immobilization. Both materials are environmentally friendly soil inputs and are compatible with food crops.…”

In-situ stability assessment and remediation mechanism of typical antimony (Sb) tailings by combined organic-inorganic solid waste in Southwest China

“…Fe and oxides such as Ca, which further enhance the adsorption of Sb. Some researchers have shown that the immobilization of As and Sb is mainly controlled by the formation of calcium-arsenic and calcium-antimony precipitates(Dutré and Vandecasteele, 1995;Dutre and Vandecasteele, 1998;Shi et al, 2022), and in strong oxidation, arsenate and calcium can form precipitates of CaHAsO4 and Ca 3 (AsO 4 ) 2…”