Abstract
To investigate the heavy metal and metalloid contamination of soil around a Huanan uranium tailings pond, abandoned in 1998, we defined a study area of 41.25 km2 by a natural boundary and targeted 5 elements’ (U, Mn, As, Pb, Cr) single contamination and comprehensive pollution as the assessment contents. First, we collected 205 samples and evaluated them with the contamination factor (CF) method aiming at judging whether the single target element concentration exceeded the local background value and environmental quality standard. We obtained CF1 (the background value of a certain target element as the baseline value) and CF2 (the environmental quality standard for soils as the baseline value). Second, we evaluated the ecological risk of the key pollutant U with the risk assessment code (RAC) method, taking the 27 samples whose CF2 > 1 as examples and concluded that the environmental risk of U was relatively high and should arouse concern. Third, we selected comprehensive pollution index (CPI) to assess the compound pollution degree of five target elements. Fourth, we constructed the U contamination and CPI’s continuous distribution maps with spatial interpolation, from which we worked out the sizes and positions of slightly, moderately and strongly polluted zones. Finally, we analyzed the spatial variability of U and CPI with the aid of a geostatistical variogram. We deduced that the spatial variation of uranium was in close relationship with local topography, and probably precipitation was the driving force of U contamination diffusion, whereas CPI exhibited weak spatial dependence with random characteristics. The above work showed that 3.14 km2 soil near the pond was fairly seriously polluted, and the other 4 elements’ single contaminations were less serious, but the 5 target elements’ cumulative pollution could not be ignored; there were other potential pollution sources besides the uranium tailings pond. Some emergency measures should be taken to treat U pollution, and bioremediation is recommended, taking account into U’s high bioavailability. Further, special alerts should be implemented to identify the other pollution sources.
Highlights
Uranium tailings ponds may contain a large amount of radionuclide and non-radioactive potentially hazardous elements and cause contamination of the surrounding soil and water environment [1]
To fully determine the pollution degrees of potentially hazardous elements, we explored the spatial characteristics of the regional pollution using spatial interpolation and constructed pollution distribution maps after assessing the discrete sampling points
The descriptive statistics, contamination factor analyses of 5 target elements concentrations according to the soil samples indicated that U pollution near the tailings pond was fairly serious, even after it was decommissioned for 20 years, and being the key pollutant, U’s ecological risk was relatively high, inferring from
Summary
Uranium tailings ponds may contain a large amount of radionuclide and non-radioactive potentially hazardous elements and cause contamination of the surrounding soil and water environment [1]. The pollution of uranium in the surrounding soil of uranium mining and metallurgy regions has been reported many times and has attracted much attention [1,2,3,4,5,6,7,8]. Contamination assessment is related to the pattern of land use, the selection of crop planting types, and the safety of agricultural products [9]. The Huanan uranium tailings pond, situated in south-central China, is the largest source of radioactive pollution in the uranium mining and metallurgical system of China. Since the served uranium smelting plant was not active, the tailings pond was covered by clay with an average thickness
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have