Potential risks of organic contaminated soil after persulfate remediation: Harmful gaseous sulfur release

Persulfate is considered a convenient and efficient remediation agent for organic contaminated soil. However, the potential risk of sulfur into the soil remediation by persulfate remains ignored. In this study, glass bottles with different persulfate dosages and groundwater tables were set up to simulate persulfate remediation of organic pollutants (aniline). The results found sulfate to be the main end-product (83.0%‒99.5%) of persulfate remediation after 10 days. Moreover, H₂S accounted for 93.4%‒99.4% of sulfur reduction end-products, suggesting that H₂S was the final fate of sulfur. H₂S was released rapidly after one to three days at a maximum concentration of 33.0 ppm, which is sufficient to make a person uncomfortable. According to the fitted curve results, H₂S concentration decreased to a safe concentration (0.15 ppm) after 20‒85 days. Meanwhile, the maximum concentration of methanethiol reached 0.6 ppm. These results indicated that secondary pollution from persulfate remediation could release harmful gases over a long time. Therefore, persulfate should be used more carefully as a remediation agent for soil contamination.