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Chemosphere

Title:		Influence of dissolved humic substances on the mass transfer of organic compounds across the air-water interface
Author(s):		Ramus K; Kopinke FD; Georgi A;
Address:		"Helmholtz Centre for Environmental Research - UFZ, Department of Environmental Engineering, Permoserstr. 15, D-04318 Leipzig, Germany"
Journal Title:		Chemosphere
Year:		2012
Volume:		20111101
Issue:		2
Page Number:		138 - 143
DOI:		10.1016/j.chemosphere.2011.09.055
ISSN/ISBN:		1879-1298 (Electronic) 0045-6535 (Linking)
Abstract:		"The effect of dissolved humic substances (DHS) on the rate of water-gas exchange of two volatile organic compounds was studied under various conditions of agitation intensity, solution pH and ionic strength. Mass-transfer coefficients were determined from the rate of depletion of model compounds from an apparatus containing a stirred aqueous solution with continuous purging of the headspace above the solution (dynamic system). Under these conditions, the overall transfer rate is controlled by the mass-transfer resistance on the water side of the water-gas interface. The experimental results show that the presence of DHS hinders the transport of the organic molecules from the water into the gas phase under all investigated conditions. Mass-transfer coefficients were significantly reduced even by low, environmentally relevant concentrations of DHS. The retardation effect increased with increasing DHS concentration. The magnitude of the retardation effect on water-gas exchange was compared for Suwannee River fulvic and humic acids, a commercially available leonardite humic acid and two synthetic surfactants. The observed results are in accordance with the concept of hydrodynamic effects. Surface pressure forces due to surface film formation change the hydrodynamic characteristics of water motion at the water-air interface and thus impede surface renewal"
Keywords:		*Air Algorithms Diffusion Gases/chemistry Humic Substances/*analysis Hydrogen-Ion Concentration Kinetics Phase Transition Salts/chemistry Volatile Organic Compounds/*chemistry Water/*chemistry;
Notes:		"MedlineRamus, Ksenia Kopinke, Frank-Dieter Georgi, Anett eng Research Support, Non-U.S. Gov't England 2011/11/05 Chemosphere. 2012 Jan; 86(2):138-43. doi: 10.1016/j.chemosphere.2011.09.055. Epub 2011 Nov 1"