Abstract
Excessive accumulation of cadmium (Cd) and arsenic (As) in rice (Oryza sativa L.) poses a potential health risk to populations. Cd and As exhibit opposite geochemical behavior in paddy soil, using appropriate remediation materials to reduce their migration and inhibit their uptake by rice is a great challenge. A pot culture experiment was conducted to investigate the effects of application of silkworm excrement biochar (BC) and ferrous sulfate (Fe(II)) on available Cd and As in paddy soils and their uptake by rice. Results showed that the application of BC + Fe significantly accelerated the tillering of rice plants, and the addition of BC alone to soil did not have a significant effect on the pH of soil, while applied 1% (w/w) BC and 1% (w/w) Fe(II) (1BC-1 Fe(II)) treatment could markedly reduce the soil pH. BC+Fe(II) could reduce the content of available Cd (reduced by 10%–23%) and As (reduced by 6%–33%) in soil. BC+Fe(II) has a distinct decreasing effect on the available As, thus inhibiting As uptake in rice tissues, and the effect was more obvious with an increasing mass ratio of Fe in BC+Fe(II) treatment. BC+Fe(II) decreased bioaccumulation factors (BF) of As compared to control and BC alone treatments. Compared with As, Cd was more readily transferred from the root to the shoot and accumulated in rice eventually. These findings provide a safe and reliable remediation strategy though application of BC+Fe(II) in Cd and As co-contaminated soil. However, the improvement effect of amendments should be paid a special attention on soil pH.
Highlights
Anthropogenic activities and mining are major sources of metals accumulation in soils, especially in agricultural soils [1,2]
translocation factor (TF), we found is easier rootCd to stem to grain migration
More rice plant tillers mean a higher yield of rice [32]
Summary
Anthropogenic activities and mining are major sources of metals accumulation in soils, especially in agricultural soils [1,2]. The pollution of Cd in paddy soils is a widespread problem due to its potential harm to plants and human health [3]. Rice (Oryza sativa L.) is a widely cultivated crop in China [1], and a common dietary source for Cd and As exposure. Cultivated in flooded soil, with the enhanced bioavailability of As in soil due to the anaerobic conditions, the rice take in more [5]. Owing to high redox potential, aerobic conditions in paddy soil can obviously inhibit the uptake of As in grains, whereas rice growing tends to increase uptake of Cd in rice under the aerobic conditions [7,8]. For ensuring the grain safety, how to simultaneously reduce the uptake of Cd and As in rice has become a vital issue and drawn much public attention
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