Hexachlorobenzene dechlorination as affected by nitrogen application in acidic paddy soil

Abstract

Batch incubation experiments were conducted to study the effects of different nitrogen (N) fertilizers (NH 4HCO 3, CO(NH 2) 2, and NaNO 3) on hexachlorobenzene (HCB) dechlorination in an acidic paddy soil. Results showed that NH 4HCO 3 and CO(NH 2) 2 had similar effects on HCB dechlorination, and their application amount was a crucial factor on reductive dechlorination. The addition of a proper amount of 0.14 g NH 4HCO 3- or CO(NH 2) 2-N to 500 g soil promoted HCB dechlorination, however, the application of a high amount (0.84 g) of NH 4HCO 3- or CO(NH 2) 2-N inhibited HCB dechlorination. Additional NaNO 3 served as an electron acceptor and led to lower soil pH, thus inhibited HCB dechlorination. Detected dechlorinated products showed that the dominant pathway of HCB dechlorination was HCB → pentachlorobenzene (PeCB) → 1,2,3,5-tetrachlorobenzene (TeCB) → 1,3,5-trichlorobenzene (TCB), and PeCB was the main metabolite. The role of methanogenic bacteria in HCB dechlorination was uncertain and conditions-dependent.