G. R. Barrie Webster

The effect of dissolved organic matter on the bioavailability of polychlorinated dibenzo-p-dioxins

Abstract The extent to which dissolved organic matter (DOM) influences the bioavailability of polychlorinated dioxins (PCDDs) was determined using Aldrich humic acid or filtered natural lake water as sources of DOM. The bioconcentration factors (BCFs) for rainbow trout (Salmo gairdneri) of four PCDD congeners were determined using both centrifuged and reverse-phase cartridge extractable water concentrations. Aldrich humic acid (DOM) reduced the apparent uptake rate constants of PCDDs by reducing the free water concentrations available to the fish. However, DOM from natural lake water had little effect on the apparent uptake rate constants relative to Aldrich humic acid. Although Aldrich humic acid overestimated the influence of DOM on BCFs relative to natural lake waters it did provide a useful tool to examine these interactions. Measured apparent BCFs of PCDDs were below those predicted by their octanol to water partition coefficients (Kow) alone but only part of this reduction was explained by calculating the true BCFs using the estimated free water concentrations. Although this may be due to experimental errors leading to an overestimation of the free water concentrations, steric hindrances, solubility factors, or metabolic transformation may also be important factors controlling the BCFs of PCDDs.

Environmental Photochemistry of Herbicides

Herbicides are commonly used as preplant or preemergence and post-emergence for controlling several weeds in most major agricultural crops throughout the World (Worthing and Walker 1983). When utilized in agriculture they are likely to enter into various compartments of the environment. They may undergo leaching by water, volatilization into the atmosphere, sorption to various surfaces, and partitioning into organic films. Their environmental behavior in each of these compartments is of prime importance in the successful prediction of their fate. The environmental picture becomes even more complex by taking into account the varying conditions existing within each compartment. Moilanen et al. (1979) listed several of the most important variables encountered within each environmental compartment (Table 1).

Aqueous solubility of polychlorinated dibenzo-p-dioxins determined by high pressure liquid chromatography

Abstract Water solubilities (SW) determined by the HPLC generator column method are reported for a series of chlorinated dibenzo- p -dioxins (PCDDs) with SW ranging from 0.4 ng/L (ppt) for octa-chlorodibenzo- p -dioxin to 430 ng/L for 1,2,3,7-tetrachlorodibenzo- p -dioxin at 20°C. A correlation is demonstrated between SW and HPLC capacity factors (k′) for these extremely hydrophobic compounds, allowing calculation of SW of PCDDs from k′ and melting point data.

Protocol guidelines for the investigations of photochemical fate of pesticides in water, air, and soils

Pesticides represent an increasingly important sort of synthetic chemical introduced into the environment through human activity. A compound is important in environmental chemistry provided it has (or shows evidence of having) the following characteristics (Choudhry et al. 1979a): produced or distributed in large quantity high likelihood of entry into the environment — dispersion tendency (transport) persistence (lack of degradation under biotic and abiotic conditions) bio-accumulation (concentration effects, e.g., in the food chain or by other mechanisms) significant toxicity and related biological effects

Analysis of Diesel Fuel Contamination in Soils by Near-Infrared Reflectance Spectrometry and Solid Phase Microextraction-Gas Chromatography

A feasibility study was undertaken to determine whether the rapid, nondestructive analytical technology, near-infrared reflectance spectrometry (NIRS) could be used to predict total petroleum hydrocarbon (TPH) in contaminated soil. Hydrocarbon concentrations were determined on samples of diesel-contaminated soils by the solid phase microextraction-gas chromatography (SPME-GC) method. The same samples were then scanned for near-infrared reflectance spectrometry over the wavelength range 1100 to 2498 nm. Calibrations were developed between the NIR spectral data and the reference SPME-GC chemical data using stepwise multiple linear regression. Linear regression relationships between NIR-predicted TPH concentrations and reference data had r2 of 0.68 and 0.72. These results indicate that the combination of NIRS and SPME-GC shows promise as a method for rapid estimation of TPH in soil. A major hurdle in the evaluation of methodology for hydrocarbons residues in soil is the challenge posed by the weathering of s...

Biotransformation and tissue distribution of 1,2,3,7-tetrachlorodibenzo-p-dioxin, 1,2,3,4,7-pentachlorodibenzo-p-dioxin and 2,3,4,7,8-pentachlorodibenzofuran in rainbow trout

Abstract Two polychlorinated dibenzo-p-dioxins were eliminated more slowly in rainbow trout which were treated with an inhibitor of biotransformation. Fish were given a single oral dose of either 14 C-labeled 1,2,3,7-tetrachlorodibenzo-p-dioxin (T 4 CDD), 1,2,3,4,7-pentachlorodibenzo-p-dioxin (P 5 CDD) or 2,3,4,7,8-pentachlorodibenzofuran (P 5 CDF). Half of the fish were daily treated with piperonylbutoxide (PBO) which is a well known inhibitor of monooxygenase activity. The amounts of radioactivity were determined in liver, gall bladder, skin, muscle, spleen, heart, kidney, gills and intestine 2, 7, 14 and 21 days after administration. T 4 CDD and P 5 CDD were both eliminated more slowly in the PBO treated fish than in the fish which did not receive PBO. P 5 CDF showed no statistically different elimination rates in PBO treated and untreated fish. For all compounds the highest concentrations were found in liver and intestine. The highest absolute amounts of each compound was found in muscle. The slower elimination rates and the higher body burden of T 4 CDD and P 5 CDD in PBO treated trout indicate that biotransformation is very important for their elimination kinetics. Biotransformation may thus be responsible for the more rapid elimination and lower body burden of these compounds under normal conditions.

Environmental photochemistry of PCDDs. Part I. Kinetics and quantum yields of the photodegration of 1,2,3,4,7-penta- and 1,2,3,4,7,8-hexachlorodibenzo-p-dixin in aqueous acetontrile

For the determination of the quantum yields of 1,2,3,4,7-pentachlorodibenzo-p-dioxin (1) and 1,2,3,4,7,8-hexachlorodibenzo-p-dioxin (2), ten Pyrex glass photochemical cells were constructed and their correction factors determined. Quantum yields at 313 nm for 1 and 2 in aqueous acetonitrile (4:6 v/v) were (9.781 ± 2.376) 10−5 and (1.096 ± 0.020) × 10−4, respectively. These quantum yields and the measured absorption spectra were used to estimate the environmental phototransformation first-order rate constants and photochemical half-lives of 1 and 2 in water under conditions of variable sunlight intensity during various seasons from solar intensity data available in the literature. In summer, typical half-lives for the phototransformation of 1 and 2, respectively, near the surface of water bodies at 40° north latitude would be 364 ± 88 and 151 ± 3 h; whilst such values in winter would be 1257 ± 309 and 518 ± 10 h.

Environmentally significant photochemistry of chlorinated benzenes and their derivatives in aquatic systems

The pollution of soil and aquatic environments by chlorinated aromatic pollutants (CAPs) such as polychlorobenzenes (PCBzs), polychlorophenols (PCPs), polychloro‐diphenyl ethers (PCDPEs), phenoxyacetic acids, etc., creates growing public anxiety. Phototransformation is an important process for pollutants in aquatic systems. This article extensively reviews the environmentally significant solution phase photochemistry of PCBzs as well as other CAPs derived therefrom. The paper includes photochemical fate of these CAPs at wavelengths >285 nm on the one hand and their photolysis in solution in aquatic systems on the other. In this article, photolytic reductive dechlorination and isomerization of PCBzs are reviewed together with the photoformation of several products including polychlorobiphenyls (PCBs) from PCBzs. Recently developed phenomena of photoincorporation of PCBzs into humic model monomers is also described. This review also describes the environmental photochemistry of chlorobenzene derivatives, na...

Environmental photochemistry of polychlorinated dibenzofurans (PCDFs) and dibenzo‐p‐dioxins (PCDDs): A review

Contamination of our water, air and soil environments by polychlorinated dibenzofurans (PCDFs) and dibenzo‐p‐dioxins (PCDDs) is of growing public concern. Among various environmental transforming processes of pollutants, photochemical transformation caused by sunlight is an important process. This paper reviews the potential photolytic source as well as the photochemical fate of hazardous PCDFs and PCDDs in our environment.

Analysis of the petroleum components benzene, toluene, ethyl benzene and the xylenes in water by commercially available solid-phase microextraction and carbon-layer open tubular capillary column gas chromatography

Extraction of the petroleum components benzene, toluene, ethyl benzene and the xylenes (BTEX) from water is described using a commercially available poly(dimethylsiloxane) solid-phase microextraction fibre assembly with separation and quantification by carbon-layer open tubular capillary column gas chromatography and flame ionization detection. All components of BTEX are resolved. No cryofocussing is required.