Department of Public Health Sciences

Chemical dynamics of persistent organic pollutants:  a sensitivity analysis relating soil concentration levels to atmospheric emissions

Eisenberg JNS, Bennett DH, McKone TE

Environmental Science and Technology. 1998. 32(1):115-123.

A dynamic modeling framework is presented that provides a method to estimate deposition of air emissions in soil, based on either single or multiple time-point soil measurements. These dynamic estimates, made in the context of the uncertainty and variability associated with environmental systems, differ significantly from those based on steady-state single-valued assumptions. A case study on the global mass balance for polychlorinated dibenzo-p-dioxins (PCDD) and dibenzofurans (PCDF) illustrates that, by explicitly representing the uncertainty of the parameters used to assess mass balance, there exists a discrepancy between deposition and source emissions of between 6- and 20-fold. The uncertainty in these soil deposition estimates was most strongly dependent on two landscape properties (the deposition velocity of air particles and the thickness of the atmosphere) and three chemical properties (the organic-carbon partition coef ficient, chemical degradation within the atmosphere, and vapor pressure). Using lower-bound values of the deposition velocity of air particles, lower-bound values of the organic-carbon coefficient, and upper-bound values of atmospheric thickness, this discrepancy was estimated to be over 1 order of magnitude; whereas using upper-bound values of the deposition velocity combined with lower-bound values of vapor pressure, this discrepancy was estimated to be around 6-fold. Constraints on these five properties decreased the uncertainty measure, as expressed by the coefficient of variation, from 0.8 to as low as 0.17.



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