Abstract:

To investigate soil accumulation of heavy metals in farmlands that have long been irrigated with sewage and its environmental risks,samples of the soil and wheat plants were collected from typical sewage irrigated farmlands alongside the Wangyanggou,a typical sewage irrigation river,for analysis of Cd,Pb,Cu and Zn contents,and status quo of the heavy metal pollution,potential ecological risks and potential health risks were evaluated. Results show that although the contents of Cd,Pb,Cu,and Zn did not exceed the limits set in the national standard,they were higher than the soil background values and those in the soil irrigated with clean water,indicating that heavy metal accumulation had already started. In about 23. 1% and 15. 4% of the wheat plant samples,the contents of Pb and Zn were higher than the standards.However,the contaminations of Cd,Pb,Cu and Zn were still in the safe range,indicating that the heavy metal contents had not yet reached their respective alarming levels. Potential ecological risk assessment shows that Cd was the highest in ecological risk coefficient,posing a moderate ecological hazard; and Pb,Cu and Zn posed slight potential ecological risks.Health risk assessment shows that none of the four heavy metals reached a significant level in single-factor health risk coefficient,but their integrated pollution risk index was higher than 1,indicating that there are certain potential health risks in this region,which are more hazardous to children than to adults. Therefore,the situation calls for adequate attention.

Key words:  sewage irrigation, soil, risk, heavy metal