Derivation of empirical model to predict the accumulation of Pb in rice grain

Lead contamination in soil has become a worldwide threat on food security and human health. To assess the Pb bioavailability and evaluate the safe use of low Pb polluted soil for food production, the speciation of Pb in 19 types of paddy soil were investigated by chemical extraction and X-ray absorption near-edge structure (XANES), and the uptake and accumulation characteristics of Pb in different soil-rice systems were investigated. Moreover, an empirical model was established to predict the content of Pb in rice grain, and field validation was conduct to evaluate model performance. Results showed that the proportion of available Pb in different soil satisfied normal distribution N (0.47, 0.23). Pb(CH3COO)(2), GSH-Pb, PbO, PbHPO4 and Pb-3(PO4)(2) performed well in characterizing the speciation of Pb in different rhizosphere soils, and PbHPO4 accounted for more than 70%. The exceedance of Pb in grain in CK, 0.5X and 1X treatment were 10.5%, 36.1% and 42.1%, respectively, and the accumulation of Pb in grain was significantly related with Pb content in root. Carbonate and organic bound Pb in rhizosphere soil were two major Pb species that influenced the accumulation of Pb in rice. Moreover, content of total Pb, clay and SOM performed well in predicting the Pb content in grain, both for pot and field samples. Above all, our predicting model worked well in evaluating Pb accumulation in rice grain among low polluted paddy farmland (Total Pb < 300 mg/kg). (C) 2021 Elsevier Ltd. All rights reserved.

Automated summary

The study evaluated the bioavailability of Pb in paddy soil and its impact on rice production. Different Pb speciation in soil was characterized, with PbHPO4 being the predominant form. The accumulation of Pb in rice grain was significantly related to Pb content in root, and carbonate and organic bound Pb in soil influenced the accumulation of Pb in rice. Total Pb content, clay, and SOM were effective predictors of Pb content in grain. The predictive model worked well in evaluating Pb accumulation in rice grain in low polluted paddy farmland.