Comparison of two experimental techniques for determining air/water Henry's law constants

Water samples from 30 lakes in Canada and the northeastern United States were analyzed for the occurrence of 27 current-use pesticides (CUPs). Eleven CUPs were frequently detected in lakes receiving agricultural inputs as well as in remote lakes hundreds of kilometers from known application areas. These included the triazine herbicide atrazine and its desethylated degradation product; the herbicides alachlor, metolachlor, and dacthal; the organophosphate insecticides chlorpyrifos, diazinon, and disulfoton; the organochlorine insecticides alpha-endosulfan and lindane; and the fungicides chlorothalonil and flutriafol. For six of the pesticides, empirical half-distances on the order of 560 to 1,820 km were estimated from the water-concentration gradient with latitude. For most of the pesticides, a suite of assessment models failed to predict such atmospheric long-range transport behavior, unless the effect of periods of lower hydroxyl radical concentrations and dry weather were taken into account. Observations and model results suggest that under the conditions prevailing in south-central Canada (relatively high latitude, low precipitation rates), many CUPs will be able to undergo regional-scale atmospheric transport and reach lakes outside areas of agricultural application. When assessing the potential of fairly reactive and water-soluble substances to undergo long-range transport, it is imperative to account for periods of no precipitation, to assure that degradation rate constants are correct, and to apply oxidant concentrations that are valid for the region and time period of interest.

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“…Muir et al [39]. b Log mean of values given in Fendinger and Glotfelty [40] and in Fendinger et al [41]. c Dubelman and Bremer [42].…”

Section: Organochlorine Cups In Lake Watermentioning

confidence: 99%

Empirical and modeling evidence of regional atmospheric transport of current‐use pesticides

Muir

Teixeira

Wania

2004

Enviro Toxic and Chemistry

130

127

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“…Relatively few experimentally measured HLCs have been reported for pesticides [6]. However, a limited number of HLCs for structurally complex pesticides have been measured recently [21,22]. Table 5 compares experimentally measured LWAPCs to bond-estimated LWAPCs for 17 pesticides.…”

Section: Vulidution Setmentioning

confidence: 99%

Bond contribution method for estimating henry's law constants

Meylan

Howard

1991

Enviro Toxic and Chemistry

249

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Bond contribution values, used to estimate Henry's law constant (HLC) (air‐to‐water partition coefficient) from chemical structure, have been determined for 59 chemical bonds by a least‐square analysis of known HLCs for 345 organic compounds. A correlation coefficient (r2) of 0.94 was determined for the relationship between known LWAPCs (log water‐to‐air partition coefficients) and bond estimated LWAPCs for the 345 compound data set. The correlation coefficient increases to 0.97 when quantified correction factors are applied to selected chemical classes. The ability of the bond method to estimate LWAPCs is demonstrated by a validation test set of 74 diverse and structurally complex compounds that were not included in the least‐squares analysis. The correlation coefficient for the validation set is 0.96.

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“…Henry's law is used to describe mass transfer between water and air. Several methods have been described and evaluated [6,7]. Because there is variable quality of published data for H [4,5], reliable methods for measuring H a r e of great value.…”

Section: Introductionmentioning

confidence: 99%

“…Fendinger et al [7] used a technique based on the same principle: the wetted-wall column where compounds are equilibrated between a thin film of water flowing down the inside of a column, and a concurrent flow of air. The method described in this paper uses a purge technique in which an inert gas purges the solute from the water phase.…”

Section: Introductionmentioning

confidence: 99%

Temperature Dependence of Henry's Law Constants for Selected Chlorobenzenes, Polychlorinated Biphenyls and Polycyclic Aromatic Hydrocarbons

Hulscher¹,

Velde²,

Bruggeman³

1992

Environ Toxicol Chem

149

109

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Modeling the fate of organic micropollutants in aquatic systems requires information about gas/water partitioning at environmental temperatures. In this paper experimental data are presented on Henry's law constant (H) for seven chlorobenzenes, three polychlorinated biphenyl (PCB) congeners, and six polycyclic aromatic hydrocarbons (PAHs). The studied compounds were 1,2,3–; 1,2,4– and 1,3,5–tri–; 1,2,3,4– and 1,2,3,5–tetra–; penta–; and hexachlorobenzene; 2–5–di–; 2,4,4′–tri‐; and 2,2′5,5′–tetrachlorobiphenyl; and the PAH compounds fluoranthene, benzo[b]flu‐oranthene, benzo[kfluoranthene, benzo[a]pyrene, benzo[ghi]perylene, and indeno[1,2,3–cd]pyrene. H was measured in a buffer solution using a modified gas‐purge technique. Values for this set of PAH compounds have not been determined experimentally before. The temperature dependence of H was measured for the tetra‐, penta‐, and hexachlorobenzenes and for all PCBs and PAHs over a temperature range of 10 to 55°C. The experimental data and temperature dependence are in good agreement with partitioning theory and available literature data. The observed temperature dependence results in a doubling of H for every 10°C temperature increase.

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Comparison of two experimental techniques for determining air/water Henry's law constants

Cited by 53 publications

References 9 publications

Empirical and modeling evidence of regional atmospheric transport of current‐use pesticides

Empirical and modeling evidence of regional atmospheric transport of current‐use pesticides

Bond contribution method for estimating henry's law constants

Temperature Dependence of Henry's Law Constants for Selected Chlorobenzenes, Polychlorinated Biphenyls and Polycyclic Aromatic Hydrocarbons

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