Distribution Characteristics and Ecological Risk Assessment of Heavy Metals under Reclaimed Water Irrigation and Water Level Regulations in Paddy Field

摘要

This article carried out research on changes of heavy metals in soil and rice plant with different reclaimed water irrigation and water level regulations. The results showed that, the heavy metals content in soil was increased after irrigated by reclaimed water, but short-term reclaimed water irrigation will not cause heavy metal pollution to the soil. The coefficient of variation had a stronger level of variation for Cd, Cr and Cu (>30%). With R2 irrigation, the Zn, Pb, Cd, Cr content in rice root could be reduced, and the Cd, Cr content in rice stem could be reduced, and also the Zn, Cd, Cr content in rice leaf could be reduced. The ecological risk coefficient of Cd in the soil was the highest, followed by Cu and Pb, and the risk coefficient of Cr and Zn was lower. The soil risk index at 60-80cm soil layer was the highest under RI irrigation, while it was the highest at 20-40cm soil layer under R2. Among them, the ecological risk of Cd under irrigation of various water sources was the highest. RI was at a strong risk on average, and R2 and R3 were moderate risks. Under reclaimed water irrigation, Cd, Pb, Cr had significant correlation to soil Ec, while Cu had significant correlation to NO3--N, and Zn had a significant correlation to sanity and NH4+-N. Therefore, R2 source might be the safest and efficient irrigation source.