第九届青年地学论坛

The phosphate oxygen isotope (δ¹⁸Oₚ) method is one of the valuable tools to trace phosphorus pollution in water. As phosphogypsum leachate (PGL) is strongly acidic and contains complex components, it is challenge to trace the phosphorus pollution of PGL in underground water using δ¹⁸Oₚ. Herein, the influence of the primary environmental conditions (microbial condition and temperature) and the PGL properties (low pH and high concentrations of fluoride, sulfate, and calcium ions) on the fractionation of δ¹⁸Oₚ in soil and water media were investigated. It was found that the δ¹⁸Oₚ increased from 10.13‰ to 10.92‰ in the presence of microorganisms, while there was no significant change in the sterilized environment. The δ¹⁸Oₚ change value at relatively low-temperature condition (0.39‰) were lower than that at high-temperature condition (0.79‰) as the microorganisms were less active in the low-temperature environment. High concentrations of fluoride and calcium ions hampered both the fractionation rate and genetic fractionation effects of δ¹⁸Oₚ in the reaction system through suppressing the activities of microorganism and phosphatase. Likewise, low pH inhibited the activity of pyrophosphatase, thereby impeding the equilibrium fractionation effect of δ¹⁸Oₚ.That is, microorganisms were the main reason for the fractionation of δ¹⁸Oₚ in soil and water media. Under anaerobic condition, sulfate ions would lead to the fractionation of δ¹⁸Oₚ because of the reduce of sulfate ions by sulfate-reducing bacteria and the release of phosphate , while sulfate ions exhibited negligible influence on the fractionation of δ¹⁸Oₚ under aerobic condition. Furthermore, δ¹⁸Oₚ fractionation of actual PGL was observed in the soil and water media, which obeyed the Rayleigh fractionation model with a fractionation coefficient of -2.97‰ and the R² value of 0.977. This study explores the δ¹⁸Oₚ fractionation effects of PGL in soil and water media, offering a theoretical reference for its application in the source analysis of phosphorus.
 

Phosphate oxygen isotope,fractionation factor,isotope fractionation,phosphogypsum leachate,water and soil media