Abstract:
In order to understand the accumulation characteristics and pollution risk of heavy metals in farmland soils in the limestone area of western Zhejiang province, 153 heavy metal contaminated farmlands were randomly selected, and both soil and rice samples were collected in the way of point-to-point. The cadmium contents of the soil and brown rice samples, and soil properties were analyzed. Moverover, the relationships between cadmium accumulation in the soils and brown rice, and soil properties were discussed. The results showed that total soil cadmium was increased with the increase of clay content, while decreased with the decrease of soil pH. The proportion of available Cd to total Cd was negatively correlated with soil pH. There was no significant negative correlation between cadmium content in brown rice and cadmium accumulation in soil, but it was significantly positively correlated with soil available cadmium and water-soluble cadmium. The cadmium content in the brown rice was significantly negatively correlated with soil pH, organic matter content and clay content. Meanwhile, soil pH value was the most important factor affecting Cd accumulation of brown rice in the limestone areas. The soil pollution risk screening value in
Soil Environmental Quality – Risk Control Standard for Soil Contamination of Agricultural Land (Trial Version) (GB 15618—2018) was not applicable to the soils with high pH value in the limestone areas. When 6.5 < pH ≤ 7.5, the results of heavy metal content in soil over standard was not consistent with those in agricultural products. The risk screening value of 0.60 mg kg
−1 could be lower, but the actual might be more than 0.80 mg kg
−1. The water soluble cadmium in soil could be better to assess the risk of heavy metal pollution of crops in the limestone areas than soil total cadmium and available cadmium.