Abstract:
objective Heavy metal pollution of paddy soil is an important issue for the quality and safety of agricultural products. The differences in the forms of heavy metals and their absorption and transport by rice in industrial and agricultural contaminated sources were investigated in order to provide a reference for heavy metal contamination control in paddy soils.
Method In the middle and lower reaches of the Yangtze River, 27 rice fields contaminated by heavy metals from industrial sources and agricultural sources were selected. The root shaking method was used to collect rhizosphere soil, rice roots and rice seeds during the rice maturity period.
Result The contents of Cd, Pb, Cu and Zn in the soil contaminated by industrial source were more than 30% higher than by the agricultural source rice field. Meanwhile, the total content of soil Cd was more than 280% of soil pollution risk control value of agricultural land. The residual form was the main form of heavy metal, accounting for 46.84% to 64.99%. The exchangeable form of Zn, Cd and Cu from industrial source were higher than those from agricultural source. The proportion of humic acid binding heavy metals in the agricultural soil was higher than that in the industrial soil. Cd and Zn in the industrial source soils showed a high soil-crop mobility. The contents of Cd, Cu, Pb in rice seeds from industrial source was 76%, 172% and 298% higher than those from agricultural source. RDA showed that the main factor for the accumulation of heavy metals in rice roots was its bioavailable form in soil. The accumulation of heavy metals in rice roots from industrial source responded more strongly to pH, while that from agricultural source responded more strongly to soil organic matter.
Conclusion Therefore, the forms of heavy metals in soil and the absorption of heavy metals by rice were different due to different pollution routes. In rice fields contaminated by industry, the availability of heavy metals and the risks of plant migration and food contamination were higher.