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Widespread contamination of agricultural soil with Cd and As has resulted in substantial transfer and accumulation of these toxicants in rice grains. In the present study, we investigated the effects of chicken manure application on Cd and As concentrations and As speciation in the rice grains grown under different water conditions by pot experiment. Under aerobic condition, the application of chicken manure increased soil pH and soil Eh during most of the growth period of rice. Consequently, the application of chicken manure has little effect on total Cd, slightly decreased total As and inorganic As of rice grains when applied at rate of 2.0%. Under intermittent irrigation condition, the application of chicken manure increased soil pH and decreased soil Eh during most of the growth period of rice. Thus, chicken manure decreased total Cd, As, and inorganic As of rice grains. Besides, there was increased reduction of Cd and As with increase in the amount of chicken manure applied. Under flooded condition, the application of chicken manure increased soil pH before heading but decreased soil pH after heading. The application of chicken manure dramatically decreased total and inorganic As in rice grains, and slightly decreased Cd of rice grains. There was increased reduction of total As concentration with the increase in the amount of chicken manure applied. Meanwhile, the inorganic As concentration was the lowest when the concentration of chicken manure was 1.0%.

The in-situ immobilization effect of sepiolite and biochar on the compound pollution of cadmium (Cd) and atrazine in acid red soil of south China was studied. Results showed that in a certain concentration range, sepiolite and biochar can improve the germination rate, ensure normal growth and increase biomass of pakchoi, reduce the content of Cd in edible parts of pakchoi in different degrees and meet international standards, and restrain absorption of atrazine in pakchoi completely. Sepiolite was more effective than biochar for the immobilization of Cd, while biochar was more effective than sepiolite for the immobilization of atrazine. Combined application of sepiolite and biochar in soil contaminated by Cd and atrazine was better than individual applications of sepiolite or biochar. The remediation method applied in this research can effectively repair the acid red soil with combined pollution of Cd and atrazine in south China, while also providing ideas for in-situ remediation of farmland soil with combined pollution of pesticides and metals.

Selenium (Se) alleviates cadmium (Cd) accumulation in several plants. Nevertheless, it is still unclear why it has such effect. Thus, this study aimed to investigate the effects of Se on soil Cd bioavailability, and Cd accumulation in flooded rice plants, and to determine the mechanisms underlying these effects. Concentration of Cd and Se in different rice tissues was determined along Cd and Se concentrations in the soil solution and soil Cd fractions. Results showed that exogenous selenite and selenate treatments significantly increased rice grain Se by 4.25- and 2.39-fold and decreased Cd by 36.5% and 25.3% relative to control treatment, respectively. The addition of Se to Cd-contaminated soil significantly decreased total Cd concentration in the soil solution by 11.2-13.0%, increased soil pH by 0.06-0.32 units, and enhanced soil Cd immobilization in relation to control. Exogenous Se also reduced diethylenetriaminepentaacetic acid-Cd, exchangeable, and residual Cd but increased the levels of Cd bound to carbonate and iron and manganese oxides. Thus, amending Cd-contaminated soil with Se may help decrease Cd content as well as increase Se levels in rice grain, as Se may mitigate Cd accumulation in rice plants by increasing soil pH, reducing Cd bioavailability, and inhibiting Cd translocation from roots to shoots.