Surface-to-Air Particle Suspension Formulations: Computed Source Term Release Model, Multimedia Environmental Pollutant Assessment System (MEPAS)
Legal Notice
Preface
Summary
Table of Contents
1.0 Introduction
2.0 Surface-to-Air Particle Suspension Models
3.0 Revised Formulations for Surface-to-Air Mass Flux Models
1.0 Introduction
The Multimedia Environmental Pollutant Assessment System (MEPAS) Computed Source Term Release Model, referred to in this report as the source term model, includes formulations for the simultaneous release of contamination into air and water from a contaminated soil site. The source term model includes formulations for surface-to-air suspension of particulate material from an area with contaminated surface material.
The original air-to-suspension formulations for MEPAS (Whelan et.al. 1987. PNL-6200) were used with only minor changes in a subsequent model release (Droppo and Buck 1996, PNNL-11080; Streile et.al 1996. PNNL-11248). Both those original and the revised particle suspension formulations documented in this report are based mainly on regulatory modeling guidance by the U.S. Environmental Protection Agency. Since those original formulations were released, a number of the particle suspension models on which the MEPAS formulations are based have been revised. The revisions have included scientific improvements in the computation algorithms as well as changes to meet new application needs. These revised models have incorporated particle size information - reflecting the recognition of the importance of such information in conducting environmental and health analyses.
The surface-to-air suspension of particulate material from an area with contaminated surface material represents a loss of contaminated material from the surface and a source of suspended contamination in the atmosphere. The resulting airborne contamination represents inhalation health hazards as well as a downwind secondary source of surface contamination.
Models are required to calculate suspension of particulate matter from surfaces into the air in both source and health impact components of a multimedia modeling system. Particle suspension results from wind and mechanical disturbances. Potential emissions can occur from areas with a wide variation in surface stabilization as well as from areas with paved and unpaved roadways. The revised formulations incorporate recent particle suspension models and provide emissions as a function of particle size. Equations are given for computing the particle emission rates as a function of particle size as well the total mass loss from an area with a contaminated soil cover.
The next section of this report provides an overview of the various surface-to-air suspension models used in the source and suspension components of MEPAS. The section following it contains the revised formulations for surface-to-air suspension of particulate material from an area with contaminated surface material. These revised formulations for the surface-to-air particle suspension computations are now implemented in Version 1.3 of the Framework for Risk Analysis in Multiple Environmental Media (FRAMES) and replace all previously released formulations for the wind suspension rate calculations in the source term model.
