Irrigation with polluted water from the upper Yellow River (YR) channel of Northwest China has resulted in agricultural soil being contaminated by heavy metals (HMs). This causes major concerns due to the potential health risk to the residents in this area. The present study aims to assess the efficiency of constructed wetland (CW) in reducing the heavy metal contamination in irrigation water and food crops, thus in reduction of potential health risk to the residents. The associated risk was assessed using hazard quotient (HQ) and hazard index (HI). The results showed a potential health risk to inhabitants via consumption of wheat grain irrigated with untreated water from YR. However CW could greatly reduce the human health risk of HMs contamination to local residents through significantly decreasing the concentrations of HMs in wheat grain. In theory, the reduction rate of this risk reached 35.19% for different exposure populations. Therefore, CW can be used as a system to pre-treat irrigation water and protect the residents from the potential HMs toxicity.

Heavy metal (HM) pollution in aquatic environments is of worldwide concern because of the toxicities of HMs in animals and humans. Constructed wetlands (CWs) have successfully been used as cost-effective natural systems to remove various contaminants. However, the effects of CW on the survival of animals have not been studied in any depth. We established a CW to remove HMs from water in Baiyin City, in the upper Yellow River (YR) region, which has a highly developed mining industry. The HM removal efficiency of CW as well as its effect on the development of the toad Bufo raddei were studied. The HM removal efficiencies by the CW were in the order Cd>Pb>Zn>Cu, and the decrease of the HM concentrations in the water also caused the decrease of the HM concentrations in B. raddei toads living in the CW. The toads in the CW had larger body sizes and less oxidative stress than toads living in the YR, and no malformations were found in the toads living in the CW. These results indicate that CW systems such as that used in this study could protect amphibians from developmental problems caused by HM pollution. We recommend that CW systems are used to treat polluted water and protect amphibians.