Pentachlorophenol In Soil Research Articles

Biodegradation of pentachlorophenol in soil: the response to physical, chemical, and biological treatments

The effects of physical, chemical, and biological treatments on biodegradation of pentachlorophenol (PCP) were studied in a silt-loam soil contaminated with 175 mg PCP/kg and uniformly 14C-labelled PCP. Biodegradation of 14C-labelled PCP and technical-grade PCP were monitored over 210 days incubation. Mineralization of labelled PCP was significantly (p=0.05) influenced by soil treatments. Negligible biodegradation occurred in either the sterile control soil or the uninoculated control soil, with less than 1% of added 14C recovered as 14 CO2. Inoculation of unamended soil with a strain of Flavobacterium (ATCC 39723) known to degrade PCP increased biodegradation of PCP; approximately 60% of the [14C]PCP was recovered as 14CO2. Increased soil water content (60% versus 30% w/w) enhanced biodegradation (67% recovery of 14C as CO2), while increased chloride ion concentration and anoxic conditions were inhibitory (20 and 1% recoveries, respectively). Residual soil PCP concentrations were also influenced by various treatments. In the sterile control soil and noninoculated control, after 210 days incubation, concentrations of PCP were 143 and 1223 mg/kg, respectively, while the PCP concentration in the inoculated soil was 21 mg/kg. When soil organic matter was increased by adding finely ground red clover leaf and stem material, the residual PCP concentration was reduced to 6 mg/kg after 210 days. Increased soil water content resulted in a residual PCP concentration of 5 mg/kg. High-pressure liquid chromatography of soil extracts revealed no accumulation of partial PCP degradation products. The results indicated that biodegradation of PCP in soil was significantly influenced by various soil amendments.

The survival of the pentachlorophenol-degrading Rhodococcus chlorophenolicus PCP-1 and Flavobacterium sp. in natural soil

The survival of two different pentachlorophenol (PCP)-degrading bacteria were studied in natural soil. The PCP-degraders Rhodococcus chlorophenolicus and Flavobacterium sp., both able to mineralize PCP into CO2 and chloride in axenic culture, were tested for the capacity to survive and degrade PCP in natural soil. These bacteria were immobilized on polyurethane (PUR) foam and introduced into natural peaty soil to give about 109 cells g-1 of soil (dry weight). R. chlorophenolicus induced PCP-degrading activity in soil remained detectable for 200 days whether or not a carbon source was added (distillery waste or wood chips). Electron microscopic investigation performed almost a year after inoculation, revealed the presence of R. chlorophenolicus-like cells in the PUR foam particles. PCP-degrading activity of Flavobacterium sp. declined within 60 days of burial in the soil without enhancing the PCP removal. R. chlorophenolicus degraded PCP in soil at a mean rate of 3.7 mg of PCP day-1 kg-1 of soil, which corresponds to ca. 5×10-3 pg of PCP degraded per inoculated R. chlorophenolicus cell day-1. The solvent extractable organic chlorine contents of the soil decreased stoichiometrically (>95%) with that of PCP indicating that PCP was essentially mineralized.

Metabolism of Pentachlorophenol (PCP) by Soil Microorganisms

Pentachlorophenol (PCP) and its sodium salt have been widely used as agricultural and industrial pesticides, especially as herbicides in paddy fields during the decade from 1960 in Japan. Degradation of PCP in soils and metabolism of PCP by isolated soil microorganisms have been intensively studied. The rate of PCP dissipation from soils under moist conditions varied among soils, and half-life of PCP was 7-14 days. The dissipation of PCP was influenced by the presence of certain fungicides as well as autoclaving. Another studies clarified the dissipation of PCP was also reduced in submarged condition. Repeated application of PCP to soils resulted in acceleration of the PCP dissipation. The evolution of 14CO2 from soil treated with 14C-PCP was observed. From these results it appeared that the dissipation of PCP depended on microbial decomposition. Pseudomonas sp. isolated from a soil degraded 14CPCP rapidly with release of approximately 50% of the 14C as 14CO2 and incorporated the 14C into the bacterial cell constituents such as amino acids. Tetrachlorocatechol (TCC) and tetrachlorohydroquinone (TCHQ) were identified as degradation products. Metabolic pathways of ortho or para hydroxylation of PCP as initial degradation step followed by rapid ring cleavage were proposed. PCP was methylated to pentachloroanisole (PCA) by isolated Mycobacterium sp. The isolate simultaneously metabolized PCP to TCHQ followed by successive methylation to form their dimethyl ethers, tetrachloro-1, 2-dimethoxybenzene or tetrachloro-1, 4-dimethoxybenzene, via monomethyl ethers, tetrachloro-2-methoxyphenol or tetrachloro-4-methoxyphenol. Chlorothiophenols as well as chlorophenols were also methylated by this bacterium. When either methionine, ATP, and Mg++ or S-adenosylmethionine was incubated with the cell-free extracts of Mycobacterium sp. in phosphate buffer containing PCP, PCA was produced. Incubation of methyl-14C labeled S-adenosylmethionine with PCP by cell-free extracts resulted in transfer of the radioactivity to PCA. These results revealed that the methylation of PCP by isolated Mycobacterium sp. was attributable to the enzyme(s) concerned with the transferance of methyl group to PCP.

PCP連用圃場のPCP分解菌とPCP耐性菌の菌数変化 : 土壌中でのペンタクロロフェノールの分解(第2報)

PCP連用圃場のPCP分解菌とPCP耐性菌の菌数変化 : 土壌中でのペンタクロロフェノールの分解(第2報)

Degradation of PCP (Pentachlorophenol) in Soil (Part 1) Microbial Depletion of PCP under the Dark and Submerged Condition

Degradation of PCP (Pentachlorophenol) in Soil (Part 1) Microbial Depletion of PCP under the Dark and Submerged Condition