ENVIRONMENTAL RISK ASSESSMENT OF APPLICATION AND POLLUTANT RELEASE OF PHOSPHOGYPSUM-BASED STABILIZED MATERIALS AFTER DEGRADATION
The possible environmental risks were evaluated by studying the pollutants leaching of phosphogypsum-based stabilized materials after degradation in extreme conditions,including acid rain leaching,immersion in freshwater,carbonization,and freeze-thawing,and the distribution of pollutants in the main environmentally sensitive points of the site road sections.The results of degradation simulation experiments in the laboratory showed that the total phosphorus in the leachate of all the performance degradation tests could reach the quality standard of Class Ⅳ of Environmental Quality Standards for Surface Water(GB 3838-2002).In the whole test period,the pH value of leaching from phosphogypsum-based stabilized materials was always better than that from cement-stabilized material and the heavy metal content was always better than that of Class Ⅰ in GB 3838-2002.The fluoride ion concentration of leaching was up to the quality standards of Class Ⅳ of Standard for Groundwater Quality(GB/T 14848-2017)or Standard for Irrigation Water Quality(GB 5084-2021)except for that of the leaching after degradation of carbonization.The analysis of the testing road section showed that the concentration of fluoride in the surrounding environment was significantly reduced,but the total phosphorus and heavy metal concentrations in the soil and surrounding surface water showed no statistical rules,all of which indicated the uncertain relationship between total phosphorus and heavy metal concentrations in the environment and phosphogypsum-based stabilized materials.Therefore,for phosphogypsum based stabilized materials,optimizing the formula design,scientifically managing the construction process,and appropriate maintenance can control the environmental pollution risk when being applied on roads.
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