珠三角滩涂围垦农田土壤和农作物重金属污染

为了研究珠三角滩涂围垦农田土壤和农作物重金属污染状况，采集了广州南沙、中山一带围垦农田农作物及其根际土壤样品，测定重金属的质量分数。结果表明，围垦农田土壤样品中Cu、Ph、Cd、Ni、Cr和Zn含量均大于广东省相应土壤环境背景值，其中Cu（56．06mg·kg^-1）、Pb（48．30mg·kg^-1）、Cd（0．72mg·kg^-1）、Ni（41．15mg·kg^-1）、Cr（115．1mg·kg^-1）和Zn（200．1mg·kg^-1）分别为背景值的3．30、1．34、12．82、2．26、2．28和4．23倍。与《土壤环境质量标准》（GB15618-1995）中Ⅱ级标准（pH〈6．5）比较，土壤样品中Cu、Cd、Ni和Zn的超标率分别为73．7％、88．6％、59．6％和28．9％。以GB15618-1995中Ⅱ级标准为评价标准，采用Nemerow指数法进行评价，土壤重金属平均综合污染指数为1．86，属3级轻污染。与《食品中污染物限量》（GB2762-2005）等相关标准比较，农作物中Cu、Pb、Cd、Ni、Cr和Zn含量的样品超标率分别为0、28．9％、2．6％、48．3％、12．3％和6．1％。由此可见，珠三角滩涂围垦农田土壤和农作物重金属污染问题已经比较突出，土壤污染以Cd为主，而农作物污染则以Ni、Ph、Cr为主。

Heavy Metals Pollution in the Reclaimed Tidal Flat Soils and Crops in the Pearl River Delta

In order to study the heavy metals pollution in the reclaimed tidal fiat soils and crops in the Pearl River Delta, the crops and their root soils were collected from the reclaimed cropland in Nansha and Zhongshan, Guangdong Province, China. The total contents of six metals Cu, Pb, Cd, Ni, Cr and Zn in soils and crops were measured. The results showed that all the concentrations of Cu, Pb, Cd, Ni, Cr and Zn in soil samples were higher than the background values in Guangdong Province soils. The content of Cu （56.06 mg·kg^-1）, Pb （48.30 m·kg^-1）, Cd （0.72 mg·kg^-1）, Ni（41.15 mg·kg^-1）, Cr（ 115.1 mg·kg^-1） and Zn（200.1 mg·kg^-1） was 3.30, 1.34, 12.82, 2.26, 2.28 and 4.23 times of the background values respectively. Compared to the Grade Ⅱ （pH〈6.5） of soil environmental quality standards （GB 15618-1995 ）, the concentration of Cu in 73.7% soil samples, Cd in 88.6% samples, Ni in 59.6% samples and Zn in 28.9% samples exceeded the criteria. Based on the Nemerow index method and the China National Soil Environmental Quality Standards （Grade Ⅱ （pH〈6.5））, the average comprehensive pollutant index for heavy metals in soil was 1.86, which belonged to slight pollution. For the edible parts of crops, the concentration of Pb in 28.9 % samples, Cd in 2.6 % samples, Ni in 48.3 % samples, Cr in 12.3 % samples and Zn in 6.1% samples exceeded the maximum levels of contaminants in foods（ GB 2762-2005 ）.The concentration of Cu in all crop samples did not exceed the standard. It was obvious that the reclaimed tidal fiat soils and crops in the Pearl River Delta were polluted with heavy metals significantly, especially Cd in soil and Ni ,Pb and Cr in crop.