Hexachlorobenzene concentrations

D. Wodarg, P. Komp, and M.S. McLachlan, A baseline study of polychlorinated biphenyl and hexachlorobenzene concentrations in the western Baltic Sea and Baltic Proper, Mar. Chem. 87 (2004) 23-36. 

Hexachlorobenzene concentration profiles and total gas production for the glucose-fed culture exposed to three initial surfactant (Tween series) loadings are shown in Figure 4. At surfactant concentrations of 10 and 200 mg/L, total gas production was identical to that of the reference (without surfactant amendment). As the initial surfactant concentration was increased to 1,000 mg/L (Figure 4C), total gas production was equal to or exceeded the reference case. These data suggest that many of the Tween surfactants were subject to biodegradation. Both the rate and extent of HCB disappearance decreased, however, as the initial surfactant concentration was increased from 10 to 1,000 mg/L. The HCB concentration in azide-amended controls did not vary significantly over die... 

Commercial PCB mixtures frequently contain impurities that may contribute to the 2,3,7,8-TCDD toxic equivalency factor. These impurities may include other PCBs, dioxins, dibenzofurans, naphthalenes, diphenyl ethers and toluenes, phenoxy and biphenyl anisoles, xanthenes, xanthones, anthracenes, and fluorenes (Jones etal. 1993). PCB concentrations in avian tissues sometimes correlate positively with DDE concentrations (Mora et al. 1993). Eggs of peregrine falcons (Falco peregrinus) from California, for example, contained measurable quantities of various organochlorine compounds, including dioxins, dibenzofurans, mirex, hexachlorobenzene, and / ,//-DDE at 7.1 to 26.0 mg/kg FW PCB 126 accounted for 83% of the 2,3,7,8-TCDD equivalents, but its interaction with other detectable organochlorine compounds is largely unknown (Jarman et al. 1993). 

When the individual insecticides are present in the solution in such a concentration range, the electron capture responds nearly uniformly to all insecticides. A column filled with 1.5% silicone OV-17 plus silicone oil (fluoralchylsiloxane) on Chromasorb W (80-100 mesh) is used for separation of the BHC alpha, beta, gamma and delta isomers (hexachlorocyclohexane), o,p -DDT, p,p -DDE, p,p -DDD, and p,p -DDT. a-BHC and hexachlorobenzene (HCB) have a common peak. They can be separated on a column filled with 2.5% Silicone Oil XE-60 (Is-cyanoethyl-methylsilicone) on Chromosorb W (80-100 mesh). 

When hexachlorobenzene was statically incubated in the dark at 25 °C with yeast extract and settled domestic wastewater inoculum, no significant biodegradation was observed. At a concentration of 5 mg/L, percent losses after 7, 14,21, and 28-d incubation periods were 56, 30, 8, and 5, respectively. At a concentration of 10 mg/L, only 21 and 3% losses were observed after the 7 and 14-d incubation periods, respectively. The decrease in concentration with time suggests biodegradation followed a deadaptive process (Tabak et al., 1981). 

When an aqueous solution containing hexachlorobenzene (150 nM) and a nonionic surfactant micelle (0.50 M Brij 58, a polyoxyethylene cetyl ether) was illuminated by a photo-reactor equipped with 253.7-nm monochromatic UV lamps, significant concentrations of pentachlorobenzene, all tetra-, tri-, and dichlorobenzenes, chlorobenzene, benzene, phenol, hydrogen, and chloride ions were formed. Two compounds, namely 1,2-dichlorobenzene and 1,2,3,4-tetrachlorobenzene, formed in minor amounts (<40 ppb). The half-life for this reaction, based on... 

Molten salt is a technique that has been considered for the destruction of pesticides and other hazardous wastes for several years. In a recent study by Rockwell International for EPA (1 ), the destruction of solid hexachlorobenzene (HCB) and liquid chlordane exceeded 99.99% in a molten sodium carbonate bath at 900 to 1000°C with a residence time of 0.75 s. For the pilot-scale tests, the concentration of HCB and chlordane in the spent melt was < 1 ppm. The HCl concentration in the off-gas was < 100 ppm. 

G. Liljegren et al., Case-control Study on Breast Cancer and Adipose Tissue Concentrations of Congener Specific Polychlorinated Biphenyls, DDE and Hexachlorobenzene, Eur. J. Cancer Prev. 7 (1998) 155-40 R. J. Helzlsouer et al., Serum Concentrations of Organochlorine Compounds and the Subsequent Development of Breast Cancer, Cancer Epidemiol. Biomarkers. Prev. 8 (1999) 525-52 J. F. Dorgan, Serum Organochlorine Pesticides and PCBs and Breast Cancer Risk Results from a Prospective Analysis, Cancer Causes and Control 10 (1999) 1-11 G. A. S. Mendonca et al., Organochlorines and Breast Cancer a Case-control Study in Brazil, Int. 

It remains unnoticed for several years that the pesticide hexachlorobenzene (HCB) has continuously entered the small well-mixed pond described in Illustrative Example 23.1. One day, your colleague determines the HCB concentration in the surface sediments of the pond and finds a Cf value of 1.3 nmol kg 1. You are alarmed by this value, because you fear that the HCB concentration in the water column could be dangerously high. Since you cannot get a water sample at once, you first try to calculate the concentration in the water column, C°p, by assuming a steady-state situation. From earlier investigations the following data on the sediments are available. 

Watts et al. (1994) studied sorption and degradation of hexachlorobenzene on geothite as the iron catalyst and concluded that mineral-catalyzed, Fen-ton-like reactions are controlled by desorption, FI202 concentration, and contaminant structure. 

Through the use of atmospheric half-lives of OC pesticides calculated from the year-to-year trend in atmospheric concentrations measured at IADN sites, virtual elimination dates of these compounds have been estimated these range from 2010 for p,p -DDT to about 2060 for hexachlorobenzene [54]. There was little, if any, spatial variability in the observed half-lives, suggesting similar loss processes among individual lakes, and also suggesting that the decrease in precipitation concentrations reflects a regional decrease in environmental levels. 

Table 8.2. Hexachlorobenzene (HCB) concentrations in bird samples from different countries... 

DDTs), hexachlorocyclohexane isomers (HCHs), chlordane compounds (CHLs) and hexachlorobenzene. Residues levels of industry-derived contaminants such as polychlorinated biphenyls (PCBs) and polychlorinated dibenzo-/>-dioxins and dibenzofurans (PCDD/Fs) were also reviewed. Concentrations of these contaminants in different environmental compartments were expressed as unit equivalent to part-per-billion (ppb) level, unless otherwise specified. The cited values of concentrations from various literature sources were rounded to two significant digits for comparison. A number of factors can influence the concentrations in biological samples. Therefore, whenever possible, for biological samples the lipid normalized concentrations were cited for comparison. 

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