Vertical distribution of Pu in forest soil in Qinghai-Tibet Plateau.

The 239+240Pu and 137Cs activities and 240Pu/239Pu atom ratios in surface soil and soil core collected from Qinghai-Tibet Plateau were investigated. The maximum of 239+240Pu and 137Cs activity concentrations in five soil cores were found in upper layers and have a same trend: the maximum followed by exponential decline. The 240Pu/239Pu atom ratio ranged from 0.160 ± 0.009 to 0.212 ± 0.012, clarified that the plutonium mainly came from the global fallout and the contribution of Lop Nor test sites was negligible. In addition, the vertical profiles of radionuclides (210Pb, 238U, 232Th, 226Ra, 40K) have been studied and a high correlation has been found between them. The correlations of Pu between organic matter (OM) and heavy metals were also studied. Person Correlation Coefficients revealed Pu had significant positive correlations with organic matter and Cd, Cu, Co, Zn, but negative correlation with Tl. The results have important implication for further understanding of the sources, records and environmental impacts of global and regional nuclear activities, which expanded the database of Pu activity level and atom ratio in Chinese soil and established a foundation for future environmental risk assessment.

Radionuclides in the environment around the uranium mines in Guangxi, China.

Uranium and plutonium are both poisonous radioactive elements, which are very harmful to human health and environment. Therefore, it is of great significance to study the distribution of 238U concentration and 239+240Pu activity in the uranium mine surrounding soils. We have collected some surface soil sediments within 2 km of two uranium mines and a solid waste management center in Guangxi Province. The 238U concentration in these study areas is in the range of 1.44-83.91 mg/g, and the 238U concentration in the A uranium mine surrounding surface soils is higher than that in the B uranium mine and the solid waste management center. While the B uranium mine and the solid waster management center don't pollute the surrounding soils because the 238U concentrations in their surrounding soils are similar to the average 238U concentration in the soil. The 239+240Pu activities in soil samples collected around the two uranium mines and the solid waste management center are close ranged from 0.06 mBq/g to 0.51 mBq/g. Moreover, the 240Pu/239Pu atom ratios in our study samples are ranged from 0.15 to 0.23, which indicate the Pu may come from the global fallout. In addition, we study heavy metals in our collected samples, only heavy metal Tl has weak positive correlations with 238U concentrations and 239+240Pu activities. And there is a weak positive correlation between 238U concentrations and 239+240Pu activities.

Characteristic of Pu from urban wetland and lacustrine sediments in Suzhou Industrial Park, China.

In this study, plutonium activity concentrations in the urban wetlands and lacustrine sediment of Suzhou Industrial Park (SIP) are studied for the first time. Results show 239+240Pu activity concentrations in the wetland surface soils of SIP range from 0.035 to 0.426 mBq/g and the 240Pu/239Pu atom ratio ranges from 0.171±0.024 to 0.226±0.049. Judging from the atom ratio of 240Pu/239Pu, the main source of Pu in the wetland is global fallout. The correlations of Pu between organic matter and heavy metals are also studied. The correlation coefficients show Pu has significant positive correlations with Cu, Sn and Pb but negative correlation with As. Unlike distributions of Pu in other places, Pu in SIP has weak correlation with organic matter content. A sediment core from Lake Yangcheng is also analyzed to investigate the historical record of Pu deposition. The atom ratios of each layer in the sediment core indicate the area is mainly influenced by global fallout. Using Pu as a discrete-time maker, the deposition rate in Lake Yangcheng is 0.396±0.019 cm/yr. The calculated inventory of 239+240Pu is 58.5 Bq/m2, which is in the range of inventories of the corresponding latitudes according to UNSCEAR.