Pentachlorophenol, in estuarine

DeLaune, R.D., R.P. Gambrell, and K.S. Reddy. 1983. Fate of pentachlorophenol in estuarine sediment. Environ. Pollut. 6B 297-308. 

The following half-lives were reported for pentachlorophenol in estuarine water exposed to sunlight and microbes 10 and 7 h during summer (24 °C) and winter (10 °C), respectively in poisoned estuarine water 6 and 10 h during summer and winter, respectively (Hwang et al., 1986). 

An important aspect of our studies were the effect of cloud cover, pH, chloride ion, and season on the photolysis of phenol and various chlorophenols. The effect of pH on the photolysis of chlorophenols is due to the higher rate of photolysis of the phenoxlde ion relative to the nonionized compound, due to stronger absorbance by the phenoxide ion ( ). The pK of dichlorophenol, trichlorophenol, and pentachlorophenol are 7.6, 7.0 and 4.8, respectively (.22, 24). Low photolysis rates of chlorophenols in both estuarine and distilled water were obtained at pH below the pK (Table III). At pH 7.6 found in estuarine water 50Z, 80Z, and 99.82 of the dichlorophenol, trichlorophenol, and pentachlorophenol, respectively, is in the form of the phenoxide ion. The photolysis rate of pentachlorophenol in estuarine water was lower than in distilled water (Table I). Addition of chloride ion to distilled water containing pentachlorophenol resulted in a decrease in the photolysis rate. Miille and Crosby ( 5) found that pentachlorophenol had a lower photolysis rate in seawater compared to distilled water due to the photonucleophilic... 

In soils, PCP persisted for 15 to more than 60 days, depending on soil conditions and application rate. At initial concentrations of 100 mg PCP/kg soil, the Tb 1/2 was 10 to 40 days at 30°C under flooded conditions. However, in aerobic soils there was virtually no degradation after 2 months (Kaufman 1978). In rice paddy soils, initial concentrations of 4 mg PCP/kg fell to 2 mg/kg in 7 days (Bevenue and Beckman 1967). Pentachlorophenol was still measurable after 12 months in warm, moist soils (Cote 1972 USEPA 1980). In estuarine sediments, degradation was most rapid under conditions of increased oxygen and a pH of 8.0 (DeLaune et al. 1983). 

Roszell, L.E. and R.S. Anderson. 1993. In vitro immunomodulation by pentachlorophenol in phagocytes from an estuarine teleost, Fundulus heteroclitus, as measured by chemiluminescence activity. Arch. Environ. Contam. Toxicol. 25 492-496. 

Seidler, J.J., M. Landau, F.E. Dierberg, and R.H. Pierce. 1986. Persistence of pentachlorophenol in a wastewater-estuarine agriculture system. Bull. Environ. Contam. Toxicol. 36 101-108. 

Photolysis of various chlorophenols as a function of time are shown in Fig. 1. The photo-transformation and photo-mineralization of the compounds followed a first-order equation In (Cg /C) kpt, where Cg and C are the concentrations of the compound at time zero and time t, while kp is the first-order photolysis rate constant. The photolysis half-lives of the compounds were calculated using the equation ti/2 = 0.693/kp. The relative rates of photolysis in estuarine water decreased in tne order 2,4,5-trichlorophenol, 2,4-dichlorophenol, pentachlorophenol, p-chlorophenol, phenol (Table 1). 

As noted above photolysis rates in estuarine water decreased in the order trichlorophenol, dichlorophenol, pentachlorophenol, chlor-ophenol, and phenol. With the exception of the transformation rates for p-chlorophenol and the photolysis rates for pentachlorophenol, for all compounds the photolysis rates including both photo-transformation and photo-mineralization were higher in the sumner than in the winter (t-test, p 0.05 Table I, Fig. 2). For example, the photo-transformation rate constant of dichlorophenol increased from 0,38 to 1.00 hr going from winter to summer, and the photo-mineralization rate constant of phenol increased from 0.006 to 0.04 day going from winter to sumner. 

Our studies indicated rapid photolysis of trichlorophenol, di-chlorophenol, and pentachlorophenol in both distilled and estuarine water. We can compare our results of pentachlorophenol with those of other investigators who have studied the photolysis of this compound in both fresh and marine waters O, 17-20). The photolysis rate constant kp for pentachlorophenol in a freshwater stream was 0.29 hr ( 1/2 2.4 hr) at 3.8 cm in the summer ( W), while we found a kp of 0.37 hr ( 1/2 " 2 hr, light hours) at a depth of 3.0 cm in the summer (Table I). The half-life of pentachlorophenol in a 1 m deep freshwater pond was 1.5 to 3 days (17) while in 5.5 m deep marine mesocosm the half-life was 22 days (18). Using lamps to simulate sunlight the pentachlorophenol in surface seawater was found to have a half-life of 2.4 hr. ( 5), Thus our rate constant and half-life for pentachlorophenol photolysis was similar to one determined by others in surface waters. Due to attenuation of light by substances in the water longer half-lives, i.e., days rather than hours, are found for pentachlorophenol when distributed throughout the water column. 

In summary, photolysis appears to be the major degradation process in the removal of dichlorophenols, trichlorophenols, and pentachlorophenol from estuarine waters but is less important in the degradation of phenol and chlorophenol. 

The degradation of pentachlorophenol (PCP) in natural waters was studied by LC-DAD and confirmed by APCI-LC-MS both after Lichrolut EN SPE. A half-life of PCP in ground water, in estuarine and river waters of < 2 h was reported... 

Bothwick, P.W. and S.C. Schimmel. 1978. Toxicity of pentachlorophenol and related compounds to early life stages of selected estuarine animals. Pages 141-146 in K.R. Rao (ed.). Pentachlorophenol Chemistry, Pharmacology, and Environmental Toxicology. Plenum Press, New York. 

Selective extraction was used to operationally determine the quantitative and qualitative distributions of PCB 8 and saturated hydrocarbons among free lipid (FL), humic acid (HA), and humin (HU) fractions of four contaminated estuarine sediments. In all samples, over 90% of the total sedimentary PCB s and hydrocarbons were extracted with FL fractions. Bound (HA and HD) and free assemblages of these compounds may have derived from different sources. Two polar, chlorinated pollutants also detected In this study, hexachlorophene (HCP) and pentachlorophenol (PCP), were proportionately more concentrated In bound fractions than the non-polar compounds HCP was detected only In HA fractions and was probably chemically hound to refractory organic matter. Selective extraction Is a promising technique for Investigating strongly bound polar pollutants, such as HCP, which apparently are not recovered by conventional solvent extraction. 

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