Decomposition of Litterfall and Evaluation of Uranium Release and Secondary Contamination from Uranium Tailings Ponds

Pollution from uranium tailings ponds poses a severe threat to aquatic ecosystems. However, its effects on litterfall decomposition in aquatic environments are uncertain. This study was conducted to investigate the effects of different species (Macleaya cordata and Typha orientalis Presl), sources (inside and outside the tailings pond), sites (above and below ground), initial biomass (1, 2, and 4 g) and initial ambient uranium concentrations (0, 1, and 3 mg/L) on the decomposition of uranium-containing litterfall. The study found that the above-mentioned indicators (litterfall self-characteristics and environmental factors) affect the decomposition of uranium-containing litterfall. The decomposition rate of litterfall in the water environment is related to the plant species, sites, and initial biomass, mainly due to the differences in the content of plant structural materials (cellulose, hemicellulose, and lignin). Uranium concentration is also an important factor affecting the decomposition of litterfall. A high concentration of uranium may affect the activities of microorganisms and thus inhibit the decomposition of litterfall, while a low concentration of uranium has the effect of accelerating the decomposition. In addition, the uranium content in M. cordata increased significantly after decomposition, but T. orientalis was the opposite, and both metal pools decreased significantly. At the same time, the underground parts of the two plants released more uranium than the aboveground parts. In conclusion, this study provides new insights and a scientific basis for the risks posed by the uranium mining industry.