[Effect of long-term fertilization on dissipation of pentachlorophenol in red paddy field]

Dissipation of pentachlorophenol (PCP) with initial concentration of 85 mg/kg in red paddy field with rice cultivation and non-rice cultivation were investigated under the conditions of four long-term fertilization treatments, including the ones without fertilizer (CK), application of urea (N), application of organic fertilizer (OM), and N + OM. The results showed that the extractable PCP residues in surface soil in the treatments CK, N, OM and N + OM under non-rice cultivation condition were 28.3, 34.2, 19.3, 18.7 mg/kg after harvesting rice plant, and the extractable PCP residues in subsurface soil were 6.3, 9.1, 5.1, 4.1 mg/kg,respectively. Under rice cultivation condition, the extractable PCP residues in surface soil were 19.4, 30.9, 16.7, 8.7 mg/kg, and the extractable PCP residues in subsurface soil were 3.7, 6.1, 2.6, 2.8 mg/kg, respectively. The results indicated that the long-term application of organic fertilizer or inorganic plus organic fertilizer significantly accelerated the dissipation of PCP in surface soil, and decreased the transportation of PCP down the soil profile. However, long-term application of urea inhibited the dissipation of PCP in surface soil, and increased the transportation of PCP down the soil profile. When compared with non-rice cultivation, rice cultivation significantly accelerated the dissipation of PCP in surface soil other than the treatment N. In addition,the rice cultivation significantly decreased the transportation of PCP down the soil profile. No matter rice was cultivated or not, the dechlorinated metabolites of PCP detected in paddy soil were 2,3,4,5-TeCP and 3,4,5-TCP. 2,3,4,5-TeCP was the major dechlorinated metabolite of PCP under non-rice cultivation condition,whereas 3,4,5-TCP was the major dechlorinated metabolite of PCP under rice cultivation condition.