Study On The Relationship Between Soil Cd Pollution And Cd Contents In Four Kinds Of Vegetables And Pollution Threshold Of Soil In Guangdong Province

Guangdong Province has been at the forefront of China’s economic development. A series of environmental problems has been brought out accompanied with the economic development, leading to more and more serious soil cadmium (Cd) pollution. The Cd pollution of the consumption of vegetables caused by soil Cd pollution affect the food safety of the residents of southern China. In order to protect the quality and safety of South China vegetables, the correlation study was carried out to establish the relationship between the Cd contamination in the different species of vegetables and in soils in Guangdong Province, which would provide a theoretical basis for the guidance of safe production of vegetables.In this study, four common vegetables in Guangdong province of leafy vegetables (Chinese cabbage), the root-stocks (carrot), solanceous vegetables (pepper), and beans (cowpea) were selected. The in-situ soils with different concentrations of Cd pollution in the typical areas of Guangdong Province were sampled for pot experiment. The characteristics of Cd absorption of different kinds vegetables, and the correlation between soil Cd content (included total soil Cd and available Cd) and Cd in vegetables were studied under the potted conditions. Soil Cd pollution threshold for safe production of different vegetables was calculated by establishing regression models between Cd concentrations in vegetables and soils. The study is aimed at providing valuable reference for establishment of more complete classification index of soil Cd pollution in the future. The results of this experiment study were as follows:1. Total Cd content and available Cd in soil in the pot experiment for the four vegetables showed same variation pattern, and manifested as a significant positive correlation The correlations between soil physical and chemical properties such as soil pH, organic matter, CEC and the total and available Cd content in soil and the Cd content in vegetables were not significant, there were no consistent variation patterns.2. Cadium content in the4vegetables increased with the increasing concentration of soil Cd.Different types of vegetables had different Cd accumulations. In this experiment, four kinds of vegetables in the same experimental condition, showed different capacities of Cd enrichment, ranking as:carrot>cabbage>pepper>cowpea, meaning that root-stocks>leafy vegetables>solanceous vegetables>beans.3. The absorption of Cd in different parts of vegetables were different. Samely, the distribution characteristics of Cd in same organs of different species vegetables were not the same. The Cd concentration in different parts of Pepper ranked from highest to lowest is:roots>stems>leaves>edible parts. The Cd concentration in different parts of cowpea varied not consistently with regularity, ranking as roots>stems> leaves at low and high Cd levels, but ranking as stems>roots>leaves or root> leaves>stems under the conditions of moderate concentrations, but the Cd concentration in edible part is lower than all the roots、stems and leaves. Carrots under the conditions of high concentration showed that:Cd concentration in underground sections> Cd concentration in aerial parts.4. For these four vegetables, the Cd concentration in roots had a significant correlation with the total Cd content、available Cd in the corresponding concentration soil and Cd content in the edible parts of vegetables, but the content in the stems and leaves did not.5. Both total and available Cd contents in soil had significantly positive correlation with Cd content in the4vegetables, with correlation coefficients above0.900. The correlation between soil total Cd and Cd content in vegetables was much better for Chinese cabbage and pepper, but the correlation between available Cd in soil and Cd content in vegetables was much better for cowpea and carrot.6. Simulated total Cd threshold in soil for Chinese cabbage, pepper, cowpea and carrot production under the pot experiment conditions were1.742,1.894,119.7and1.078mg/kg respectively, ranking from highest to lowest as cowpea>>pepper>Chinese cabbage>carrot, all higher than current soil standard limit values.Simulated available Cd threshold in soil for Chinese cabbage, pepper, cowpea, carrot production under the pot experiment conditions were0.8276,0.7069,58.88and0.065mg/kg respectively, ranking from highest to lowest as cowpea>>cabbage>pepper>carrot. Except the soil available Cd threshold for carrot, that for other vegetables were higher than current soil standard limit values.