[Simulation Cadmium (Cd) Accumulation in Typical Paddy Soils in South China].

The simulation analysis of the migration path and soil accumulation trend of Cd in paddy soil systems could contribute to improved scientific and reasonable risk decision-making. In this study, based on a regional survey of environmental media in Youxian County, Hunan Province, a pollutant accumulation model (PAM) was built to predict the cumulative trend of Cd in paddy soils. Combined with Monte Carlo simulation, the PAM model was used to evaluate the effectiveness and sustainability of various remediation measures. Results showed that the probability of Cd accumulation in paddy soils in Youxian County exceeded that of the national soil environmental quality standard by 2-fold and was up to 82.1%, and the average accumulation rate reached 4.28 µg·(kg·a)-1 after 50 years of cultivation under current input pattern. Sensitivity analysis results showed that atmospheric deposition and rice uptake were the key processes affecting Cd accumulation in paddy soils. Results of a multi-scenario simulation showed that the comprehensive measures, such as reducing the straw returning, optimizing the layout of industrial and mining enterprises that reduce the atmospheric deposition of Cd, and cleaning irrigation water, could reduce the Cd accumulation in paddy soils by 43.7% and reduce the probability of light Cd pollution by 80.6% after 50 years, which would be an effective long-term measure to prevent and control Cd pollution risk in paddy soils.

Health risk assessment of heavy metals in Cyprinus carpio (Cyprinidae) from the upper Mekong River.

The purposes of this research are to quantify the concentration of heavy metals (Zn, Cu, As, Pb, Cd, and Hg) in the water and fish tissues of common carp (Cyprinus carpio) in the upper Mekong River and to thereby elucidate the potential dietary health risks from fish consumption of local residents. Surface water and fish tissues (gill, muscle, liver, and intestine) from four representative sample areas (influence by a cascade of four dams) along the river were analyzed for heavy metal concentrations. Results revealed that the levels of heavy metals in fish were tissue-dependent. The highest Cu and As levels were found in the liver; the highest Zn and Pb levels occurred in the intestine, and the highest Hg level was found in the muscle. The total target hazard quotient (THQ) value for residents is > 1 for long-term fish consumption, and local residents are, therefore, exposed to a significant health risk. Results from the current study provide an overall understanding of the spatial and tissue distribution of heavy metals in water and fish body along the upper Mekong River under the influence of cascade dams and highlight the potential health risk of As for the local residents of long-term fish consumption.