Abstract:

Perchlorate ( {\mathrm{ClO}}_4^{-}), a low molecular weight toxic inorganic complex anion is a widespread contaminant in the environment. Perchlorate contamination is a serious environmental problem as perchlorate is known to impact thyroid function by replacing iodine intake due to its similar molecular size with iodine. Column experiments, using river sand from the polluted site as the experimental material, were conducted to stimulate natural attenuation of the target pollutant, perchlorate ( {\mathrm{ClO}}_4^{-}). The effects of iron oxides and nitrate ( {\mathrm{NO}}_3^{-}) were also evaluated. The results show that {\mathrm{ClO}}_4^{-} natural attenuation is mainly dependent on microbial degradation in the aquifer, and the groundwater environment is more conducive to microbial activity. Natural river sand can remove 2 mg/L {\mathrm{ClO}}_4^{-}; however, the process is slow and the reduction amount is limited. A lack of electron donors was found to result in a long-term removal efficiency of less than 10%. Iron oxides can stimulate natural attenuation of {\mathrm{ClO}}_4^{-}. In fact, the attenuation process began to be affected when the concentration of dissolved iron was lower than 5.5 mg/L. Nitrate ( {\mathrm{NO}}_3^{-}) in groundwater has an inhibitory effect on {\mathrm{ClO}}_4^{-} reduction. When {\mathrm{NO}}_3^{-} concentration was less than 10 mg/L, an apparent reduction in {\mathrm{ClO}}_4^{-} could be initiated.

Key words: perchlorate, natural attenuation, microbial degradation, electron donors, iron oxides, nitrate