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Spatial moment analysis of transport of nonlinearly adsorbing pesticides using analytical approximations
Author(s) -
Beltman Wim H. J.,
Boesten Jos J. T. I.,
van der Zee Sjoerd E. A. T. M.
Publication year - 2008
Publication title -
water resources research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.863
H-Index - 217
eISSN - 1944-7973
pISSN - 0043-1397
DOI - 10.1029/2007wr006436
Subject(s) - sorption , moment (physics) , mechanics , mass transfer , dispersion (optics) , thermodynamics , materials science , soil science , physics , chemistry , environmental science , classical mechanics , adsorption , organic chemistry , optics
Analytical approximations were derived for solute transport of pesticides subject to Freundlich sorption, and first‐order degradation restricted to the liquid phase. Solute transport was based on the convection‐dispersion equation (CDE) assuming steady flow. The center of mass (first spatial moment) was approximated both for a non‐degraded solute pulse and for a pulse degraded in the liquid phase. The remaining mass (zeroth spatial moment) of a linearly sorbing solute degraded in the liquid phase was found to be a function of only the center of mass (first spatial moment) and the Damköhler number (i.e., the product of degradation rate coefficient and dispersivity divided by flow velocity). This relationship between the zeroth and first spatial moments was shown to apply to nonlinearly sorbing pulses as well. The mass fraction leached of a pesticide subject to Freundlich sorption and first‐order degradation in the solution phase only was found to be a function of the Damköhler number and of the dispersivity, so independent of sorption. Hence perceptions of the effects of sorption on pesticide leaching should be reconsidered. These conclusions equally hold for other micropollutants that degrade in the solution phase only.