Study On The Relationship Between Radionuclides And Soil Fertility Under Different Land Use

The red soil region of South China which located in the subtropics has occurred soil quality degradation in consequence of high intensity rainfall and biological cycle. The increasingly serious soil erosion led to the decreasing of soil fertility and the soil structure change. There are obvious changes in soil organic matter, soil partical and other features during the decreasing of soil fertility which were caused by soil erosion. Therefore, studying soil fertility status is important to rational land planning, effective management and sustainable development. As soil particals and organic soil colloids have a strong adsorption of radionuclides, exploring the relationship between the radionuclide and soil fertility factors and evaluating the soil quality qualitatively has important theoretical significance.This study was conducted in a small watershed nearby Chayuan Mount in Yujiang County, Jiangxi Province. A field servey was carried out at first. Then we analyzed the physical and chemical properties of soil samples and measured the radionuclides. The correlation betweent soil radionuclide (137Cs and 210Pbex) and chemical indicators (TOC, TN, TP, soil aggregates and soil particle size) were analyzed. The results showed that:(1) Land use types have significant effects on the distribution and changes of 137Cs and 210Pbex in soil profiles. The migration laws of these two radionuclides in the soil profiles are similar. The content of 137Cs and 210Pbex in non-cultivated land soil decaying exponential with depth increases in 0-20 cm while it showed a relatively uniform distribution trend in culticated land soil. This result suggests that 137Cs and 210Pbex have similar distribution characteristics and migration laws in soil profiles.(2) The correlation between nutrient elements and radionuclides are significant different under different land use types. It mainly for:â‘  Under different land use type, the content of TOC,TN and radionuclides have similar distribution trends with decreased depth. The distributions of TP and radionuclides concentration are significant different.â‘¡Overall, the correlation between TOC, TN and radionuclides concentration was significantly, it was much more significant in non-cultivated land than cultivated land. The correlation between TP and radionuclides content is more complex, it dose not appear certain regularity under different land use types, while TP content showed a significant correlation with pH value.(3) The correlation between soil mechanical composition and radionuclides under different land use types are obvious defferent. â‘ The content of water stable aggregates (5-2mm) have significant correlation with radionuclides content, the mean weight of water stable aggregate and radionuclides also have a strong correlatioa.â‘¡ The correlation between soil partical size percentage and radionuclide content is also studied. This study found that the percentage of sand has a strong positive correlation with radionuclide content, the percentage of silt and clay have a negative correlation with radionuclide content. â‘¢The fractal dimension of soil particle size weight has a negative correlation with radionuclide content under different land use types.