Pentachlorophenol measurement

In summary thermal decomposition of chlorinated phenols does not generally lead to dioxins. There are, however, several conditions which by themselves or combined would favor dioxin formation. First, of all chlorinated phenols either in bulk or in solution, only pentachlorophenol produced measurable amounts of dioxin. Secondly (Table II), only sodium salts in salid state reactions produced dioxins in reasonable yields. In contrast, the silver salt of pentachlorophenol (Figure 8) undergoes an exothermic decomposition at considerably lower temperatures and produced only higher condensed materials. No dioxin was detected. 

Chlorinated dibenzo ip-dioxins are contaminants of phenol-based pesticides and may enter the environment where they are subject to the action of sunlight. Rate measurements showed that 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is more rapidly photolyzed in methanol than octachlorodi-benzo-p-dioxin. Initially TCDD yields 2,3,7-trichlorodiben-zo-p-dioxin, and subsequent reductive dechlorination is accompanied by ring fission. Pure dibenzo-p-dioxin gave polymeric material and some 2,2 -dihydroxybiphenyl on irradiation. Riboflavin-sensitized photolysis of the potential precursors of dioxins, 2,4-dichlorophenol and 2,4,5-trichloro-phenol, in water gave no detectable dioxins. The products identified were chlorinated phenoxyphenols and dihydroxy-biphenyls. In contrast, aqueous alkaline solutions of purified pentachlorophenol gave traces of octachlorodibenzo-p-dioxin on irradiation. 

FIG 12 Potential difference between Ag/AgCl electrode in the stem and Ag/AgCl electrode in a root of a soybean plant measured 70 h after adding 50 mL of 5 x 10 M pentachlorophenol to soil. Distance between Ag/AgCl electrodes was 9 an. The plants were given water every other day and kept at 24°C. Volume of soil was 0.5 L. (b), (c) and (d) show short time intervals of (a). (From Ref. 19.)... 

Dobbs, A. J., Grant, C. (1980) Pesticide volatilization rate a new measurement of the vapor pressure of pentachlorophenol at room temperature. Pestic. Sci. 11, 29-32. 

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). 

Pentachlorophenol was found at high concentrations in all samples of sediments, waters, and biota collected near industrial facilities that used PCP as a wood preservative (Niimi and Cho 1983 Oikari and Kukkonen 1988) (Table 23.3). Fish can bioconcentrate PCP from water up to 10,000 times (Fox and Joshi 1984). However, similar concentrations were measured in blue mussel, Mytilus edulis (Folke and Birklund 1986), and softshell clam, Mya arenaria (Butte et al. 1985), from the vicinity of PCP-contaminated wastewater discharges as well as from more distant collection sites. Thus, PCP bioaccumulation in marine bivalve molluscs does not appear to be dose related. 

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. 

There are a few data that suggest that pesticides can undergo reactions indoors. For example, Wallace et al. (1996) observed that the aldrin levels inside a home decreased with time, whereas those of dieldrin did not. Dieldrin had been applied with aldrin but is also an oxidation product of aldrin. One of the reasons for the lack of change in dieldrin may be that it was being formed as the aldrin decayed however, this could not be differentiated from the effects of a lower vapor pressure of dieldrin, which could lead to lower overall removal rates. In the same study, pentachloroanisole was also measured inside the home and attributed to formation by degradation of pentachlorophenol, which is used as a wood preservative and termiticide. 

The deficiency of tlie LH equation was demonstrated also for pentachlorophenol [25] and by Cunningham [26-28]. The quantum yields for photodegradation of salicylate and other strongly sorbing substituted benzenes were less than those measured for nonsorbing chlorophenols. For salicylic acid, which chemisorbs, the photo-oxidation rates in air-saturated solutions are independent of the salicylic acid concentration, although the surface excess increases with the concentration [29]. 

Unexpectedly high immunotoxicity of higher chlorinated PCDEs compared to lower chlorinated PCDEs has been reported in mice [89]. Immunotoxicity of PCDEs 206,207,208, and 209 were measured in C57BL/6 mice and in less Ah-re-sponsive DBA/2 mice. Harper et al. [89] suggested that some immunotoxic effects could be independent from Ah-receptor. Another study also refers that immunotoxicity of PCDEs may not be mediated by Ah-receptor. Kverkliet et al. [90] studied humoral immunotoxicity of a PCDE fraction isolated from technical grade pentachlorophenol in C57BL/6 mice and observed that this fraction was not immunosuppressive at any dose level tested. The PCDE fraction contained hexa-, hepta-, octa-, and nonaCDEs. 

Their adsorptive capacity for phenol, pentachlorophenol, dodecylbenzenesulphonate, and p-toluenesulphonate were measured [9 ] From these results the carbons J23 and J32 and the reference carbon F 400 (Calgon corporation) were selected to study the adsorption of humic substances. 

Verein Deutscher Ingenieure (1997) Indoor air-poUution measurement. Measurement strategy for pentachlorophenol (PCP) and y-hexachlorocyclohexane (lindane) in indoor air. VDI 4300, part 4... 

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