Residual level of chlorine disinfectant, the formation of disinfection by-products, and its impact on soil enzyme activity

Disinfectants can kill pathogenic microorganisms, effectively block the spread of infectious diseases, and are widely used during epidemics. However, a little has been studied about the environmental hazards caused by the heavy use of disinfectants. In this paper, the residual situation of chlorine ions in the soil, possible disinfection by-products (DBPs), and effects on soil enzyme activities after using 84 disinfectants (main component: sodium hypochlorite) and hypochlorite disinfectant (main component: hypochlorous acid) were investigated. It was found that the residual rates were generally higher than 92% for the 84 disinfectant treatment and between 80% similar to 90% for the hypochlorite disinfectant treatments. The overall change in chlorine ion concentration in the soil-leaching solution of the hypochlorite disinfectant treatments was relatively small and stable compared to the 84 disinfectant treatments. Several types of trihalomethanes (THMs) were detected after 24 h of disinfection. The generation concentration of THMs was higher for the 84 disinfectant than for the hypochlorite disinfectant. The generation of trichloromethane was the highest, ranging from 1000 to 3000 mu g/L. Soil enzyme activities changed much when the soil was treated with the disinfectant for 28 days. The above results indicated that hypochlorite disinfectant was safer and more stable than 84 disinfectants, and trichloromethane should be strictly controlled as a key indicator among the disinfection by-products. In addition, the long-term application of disinfectants affects soil enzyme activities obviously.