A Study On Spatial Variation Of Heavy Metals In Plants In A Typical Area Of The Yangtze River Delta

With rapid global economic development and industrialization, as well as changing agriculture practices, heavy metal pollutants are introduced to the environment, especially the soil, in various ways. Plant biology and human health are negatively impacted by highly concentrations of heavy metals in their surroundings.In this study, the spatial variation of copper (Cu), lead (Pb), and cadmium (Cd), in rice and wheat grains, were studied by collecting soil and crop samples in Zhangjiagang County of the Yangtze River Delta in China, and primary statistical models of heavy metal accumulation in rice and wheat grain were developed. These results can provide important basic information and reference for assessing security of agricultural product quality and performing effective agricultural management in the region. Results are described as follows:1. Pb and Cd contents in some rice and wheat samples significantly exceeded the National Food Health Standards (NFHS) (GB2762-2005). Most of samples which exceeded the standards appeared in the areas near industries. The Cu in rice and wheat, and Cd in rice have no threat to human health at present, but accumulation of Cu and Cd in the areas near industries should be closely monitored.2. Spatially, Cu and Pb content in rice was higher in Anthrosols than Cambosols and the converse was true with respect to Cd (p<0.05); Cu and Cd content in wheat was higher in Cambosols than Anthrosols, and for Pb was higher in Anthrosols than Cambosols.3. The accumulation of Cu and Cd in rice and wheat were significantly affected by their background level in the soil, as was Pb in wheat. Accumulation of Cd was affected by soil pH.4. The heavy metal content in rice and wheat was also dependant on the types of industries presented. Cu and Cd were higher in areas close to chemical industries, while Pb was higher in areas close to metallurgy industries.5. Content and distribution of heavy metal in crops is influenced by their concentration in the soil, soil properties, types of crops, and heavy metal properties. Crop uptake of heavy metals from soils was influenced by crop types and transfer ability of heavy metals. For Cu and Cd, crop uptake was higher for wheat than rice, and higher for rice than wheat for Pb. For different heavy metals, metal uptakes by wheat was in the following order: Cd > Cu > Pb; uptake by rice was in the following order: Cu > Cd > Pb. Therefore, crops with weak uptake towards certain heavy metals should be paired with soil affected by that particular heavy metal to reduce the impact on human health.6. The heavy metal models in rice and wheat grains by stepwise regression can fit the heavy metal contents in rice and wheat grain estimations on Anthrosols and Cambosols in Zhangjiagang.