Spatio-temporal distributions and indications of multi-nuclides on suspended particulate matters in the middle and lower reaches of the Yellow River

Natural radionuclides (²³⁸U, ⁴⁰K, ²²⁶Ra, ²²⁸Ra, ⁷Be, ²¹⁰Pb_xs, etc.) are important tracers for understanding the sources and transport process of particulate matters. However, studies about the nuclides on suspended particulate matters (SPM) in rivers are still rare thus far. In this study, we analyzed the activity levels and spatial-temporal distribution characteristics of multiple natural radionuclides on SPM in the middle and lower reaches of the Yellow River. It was found that the activity ranges of ²³⁸U, ⁴⁰K, ²²⁶Ra, ²²⁸Ra, ⁷Be and ²¹⁰Pb_xs on SPM in spring were 26.86～119.57 Bq/kg, 619.50～835.62 Bq/kg, 12.88～55.51 Bq/kg, 24.55～82.61 Bq/kg, 0.24～39.47 Bq/kg, and 0.92～18.78 Bq/kg; and were 40.54～73.96 Bq/kg, 804.95～1023.12 Bq/kg, 31.24～47.68 Bq/kg, 57.92～77.95 Bq/kg, 0.98～30.50 Bq/kg, and 12.60～31.33 Bq/kg in autumn, respectively. Both the ranges and trends of ⁷Be were similar in the two surveys. The specific activities of all other nuclides in spring were higher than which in autumn. In terms of the spatial distribution of various nuclides contents and ratios, there were significant anomalies in the three regions of Xiaolangdi, Kaifeng and Jiangjundu. It was speculated that this may be due to the changes of material source, particle size and compositions.