Recent reports have drawn attention to the uranium contamination arising from coal mining activities in the Yili region of Xinjiang, China due to the mixed distribution of uranium and coal mines, and some of the coal mines being associated with a high uranium content. In this study, we have collected water samples, solid samples such as soil, mud, coal, and coal ash, and hair and urine samples from local populations in order to evaluate the uranium level in this environment and its implications for humans in this high uranium coal mining area. Our results showed that uranium concentrations were 8.71-10.91 μg L-1 in underground water, whereas lower levels of uranium occurred in river water. Among the solid samples, coal ash contained fairly high concentrations of uranium (33.1 μg g-1) due to enrichment from coal burning. In addition, uranium levels in the other solid samples were around 2.8 μg g-1 (the Earth's average background value). Uranium concentrations in hair and urine samples were 22.2-634.5 ng g-1 (mean: 156.2 ng g-1) and 8.44-761.6 ng L-1 (mean: 202.6 ng L-1), respectively, which are significantly higher than reference values reported for unexposed subjects in other areas. Therefore, these results indicate that people living in this coal mining area have been subjected to uranium exposure for long periods of time.

Groundwater in many parts of the world is contaminated with arsenic and nitrate. To date no technology is available that can in situ remediate arsenic and nitrate pollution of groundwater using one single bacterial species. In this study, a novel anaerobic nitrate-dependent Fe(II)-oxidizing bacterium, Clostridium sp. strain PXL2, was isolated from anoxic activated sludge. The strain PXL2 could efficiently oxidize Fe(II) associated with the reduction of nitrate. Scanning Electron Microscope (SEM), X-ray diffraction (XRD) and Fourier Transform Infrared Spectrometry (FTIR) analysis showed that strain PXL2 formed nanosize and poorly crystalline Fe(III) oxides which encrusted the cells, with the viability and function of the cells might being inhibited by the encrustation of Fe(III) oxides. It was found that strain PXL2 was an excellent candidate microbe for bioremediation of nitrate and arsenic pollution. It could effectively and simultaneously remove As(III) and nitrate from water due to its Fe(II) oxidation and denitrtification activity. 40.6–100% of NO₃⁻ was removed from an initial concentration of 12.3 mM. High concentrations of As(III) decreased nitrate removal. With initial concentrations of 10 μM, 65 μM and 125 μM As(III), 100% of As(III) was removed in a 20 d treatment. Arsenic was removed by adsorption to the biogenic Fe(III) oxides but not by adsorption to the cells. Strain PXL2 was also able to oxidize As(III) to less mobile and less toxic As(V) and this may significantly enhance the performance of bioremediation of arsenic pollution. Anaerobic nitrate-dependent Fe(II)-oxidizing species, such as strain PXL2, has great application potential for in situ remediation of nitrate and metal(loid)s polluted groundwater with advantages of high efficiency and low cost.