Municipal Waste Incineration Risk Assessment Deposition, Food Chain
The disposal of large quantities of municipal solid waste (MSW) being generated by industrialized countries has become a serious problem. Since it is estimated that within 10 years, half of all municipalities will lack sufficient landfill space, many citi
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Laboratory between two flat terrain models, ISCST and ISCLT, and two current, state-of-the-art complex terrain models recommended by u.s. EPA (1986a), COMPLEX I and the Rough Terrain Diffusion Model (RTDM), that were modified to estimate pollutant deposition. The two primary questions for the study were: (1) is it acceptable to use flat terrain models such as ISCST and ISCLT to model sources located in complex terrain; and (2) are more sophisticated, particle size-dependent deposition models better than algorithms currently used in ISCST and ISCLT? This report contains brief descriptions of the modifications made to COMPLEX I and RTDM, and the findings and conclusions from the study.
DESCRIPTION OF MODELS USED IN THE STUDY ISC Models The short and long term versions of the Industrial Source Complex Model, ISCST, and ISCLT are preferred for use in flat or moderately rolling terrain when modeling sources such as stacks from MWCs or other industrial source complexes (U.S. EPA, 1986a). Both are steady state Gaussian plume models which contain limited provisions for estimating the effects of terrain on pollutant transport. ISCST and ISCLT are sometimes used to estimate pollutant transport in complex terrain. However, concentrations estimated for points above stack top elevation are sUbject to extreme uncertainty as the models sUbstitute stack top elevation for the point's actual elevation. Pollutant deposition is calculated through the use of surface reflection coefficients and gravitational settling velocities. COMPLEX I COMPLEX I is a recommended second level screening model for use in complex terrain (U.S. EPA, 1986a). Like ISCST, it is also a Gaussian plume model. For terrain below the height of the stack being modeled, the algorithms used by COMPLEX I are essentially the same as those found in ISCST. However, for terrain above stack height COMPLEX I contains five traditional options for modeling complex terrain effects (Turner, 1986). The recommended option makes use of a terrain correction factor which reduces pollutant concentrations for elevations up to 400 meters above stack height (Turner, 1986). At elevations above this height, concentrations are set equal to zero. Algorithms used in COMPLEX I to estimate atmospheric pollutant concentrations are not capable of calculating pollutant deposition. Since one of the chief goals of this study was to determine whether deposition rates estimated by a more sophisticated deposition model were a significant improvement over those estimated by ISCST, it was necessary to modify the concentration algorithms of COMPLEX I to calculate pollutant deposition. Since concentration and deposition are interdependent (i.e., plume depletion), accurate representations for bo~h of these quantities can only be obtained from concentration algorithms which consider depositional effects. An evaluation of several existing 2
models capable of estimating pollutant deposition revealed that the algorithms found in the MUltiple Point Source Algorithm with Terrain Adjustments Including Deposit
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