Cadmium pollution characteristics and ecological risk assessment of undeveloped island soil of the Pearl River water system in Guangzhou
A large number of undeveloped islands in the Pearl River water system in Guangzhou are very important urban wetland systems and natural landscape resources in Guangzhou.The heavy metal cadmium pollution in the soil not only affects the development and stability of the island's own ecosystem,but also is an important factor affecting the safety and health of the Pearl River aquatic ecosystem.This study investigated and analyzed the soil cadmium content and pollution status of twenty-two undeveloped islands in five watersheds of the Pearl River water system in Guangzhou,and assessed the aquatic ecological risk of soil cadmium to the waters near the two islands,Dazhou Island and Longmensha Island,by using the species sensitivity distribution model(SSD).The results showed that the total cadmium content of sixty-seven soil samples from twenty-two river islands ranged from 0.01～5.95 mg/kg,with an average of 0.62 mg/kg,the highest cadmium content was found in Dazhouwei Island of Dongjiang River basin,and the average cadmium content in islands reached 2.35 mg/kg,followed by Longmensha Island in the front and back channels,Dazhou Island in Liuxi River basin,and Shichuansha Island in the south channel;According to the Standard for Risk Management and Control of Agricultural Land and Soil Pollution of Soil Environmental Quality(Trial)(GB 15618-2018),the cadmium content of thirty-four soil samples exceeded the risk screening value.According to the evaluation results of the local cumulative index,forty-nine of the sixty-seven soil samples were polluted by cadmium to varying degrees,accounting for 73.1%of the total samples;Based on the evaluation results of the cadmium accumulation index of island soil sampling points,among the twenty-two undeveloped islands,only three islands have cadmium in their soil in a pollution-free state,while the other nineteen have varying degrees of cadmium pollution.The analysis results of potential ecological risks of soil cadmium show that there are nine low risk islands,seven islands are medium risk,six islands are high risk,and all the five basins of the Pearl River water system in Guangzhou have undeveloped islands where soil cadmium is moderately and severely polluted and there are medium and high ecological risks.The results of SSD curve ecological risk assessment found that only sample sixteen of the four samples from the two islands of Dazhou Island and Longmensha Island was of medium ecological risk,and the other three samples were of high risk.The soil of the two islands may become a source of cadmium pollution in the nearby aquatic ecosystem during the wet season.Therefore,there is a certain ecological risk of cadmium pollution in the soil of undeveloped island of the Pearl River water system in Guangzhou,which should be monitored and remedied.
Undeveloped island wetlandthe Pearl River water system in Guangzhousoil cadmium pollutionecological risk assessment
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