Identifying the Criteria of Cadmium Pollution in Paddy Soils Based on a Field Survey

In this paper, a field survey was conducted to evaluate the criteria of cadmium pollution in paddy soil. A set of 32 samples of paired grain, straw, and topsoil (0-20) were collected, and Cd concentrations in soils and rice plants were determined by an ICP-MS. The results indicated that Cd concentrations of fifteen soil samples were excessive to the value of maximum allowable limit (MAL) for cadmium in soil (1.0 mg kg-1), and Cd concentrations of five brown rice samples were excessive to maximum level for cadmium in rice (0.2 mg kg-1 dry matter). It was found that Cd concentrations in straw and brown rice are significantly (P<0.01) correlative to the Cd concentrations in topsoil with the correlative coefficients 0.800** and 0.907**, respectively. Using the regression equation and maximum level for cadmium in rice, the criteria of Cd pollution in paddy soil modified as 1.5 mg kg-1 was recommended. Cadmium concentration in straw could be used for early distinguishing the status of cadmium contamination of rice grain.