Environmental correlates of the distribution characteristics of artificial radionuclides (137Cs, 239+240Pu, 237Np) in the northeast China

This work focuses on the correlation between the distribution of artificial radionuclides cesium(137Cs), plutonium(239+240Pu), and neptunium(237Np) and regional environmental factors in northeast China (NEC). For soil/ sediment in this work, HPGe was used for 137Cs measurements and ICP-MS for Pu isotope and 237Np measurements. The 137Cs, 239+240Pu, and 237Np activities of the surface samples were 0.9-55 Bq/kg, 0.021-2.8 Bq/kg, and 0.02-3.9 mBq/kg, respectively. The 137Cs, 239+240Pu, and 237Np inventories were 823-3335 Bq/m2, 57-336 Bq/m2, and 0.016-0.31 Bq/m2, respectively. The surface activity and inventory datasets based on nuclides were analyzed for correlation with the environmental factors dataset to correlate their correlations. The correlation results showed that 137Cs and 237Np surface soil activity and 137Cs and 239+240Pu inventories were positively correlated with soil total organic matter (SOM), soil cation exchange capacity (CEC), normalized difference vegetation index (NDVI), and mean annual precipitation (MAP), while negatively correlated with pH and altitude (ALT). Surface soil 239+240Pu activity was positively correlated with SOM, CEC, NDVI, and ALT but barely correlated with pH and MAP. Exploring and quantifying the extent to which 137Cs, 239+240Pu, and 237Np concentrations correlate with environmental factors provides important support for predicting the safety of nuclides in the environment.