Modeling of Contaminant Partitioning in the Multimedia
Environment
Research Team: Professor Yoram Cohen (PI), Robert van de Water (Graduate Student),
Rajeev Vohra (Graduate Student).
In response to the needs of the State of California and California Industry for conducting a
credible multimedia risk assessment for air toxics, the multimedia transport and exposure assessment
(MTEA) project has focused on the assessment and development of practical multipathway transport
and exposure assessment tools. The first component of the MTEA project focuses on the continuing
development of the integrated spatial-multimedia-compartmental model (ISMCM) to assess the
multimedia environmental partitioning of volatile and particle-bound pollutants in the environment.
The description of the modeling approach and rationale are described in two recent papers by Cohen
and Clay (1994) and Cohen (1993). The ISMCM is based on a detailed mechanistic description of
intermedia transfer processes. Thus, relative to other existing multimedia models, the ISMCM can
be used to study various scenarios with minimum parameter input requirements . The ISMCM
describes the environmental media as composed of eight main compartments (air, aerosol, soil, water,
sediment, suspended solids, biota, vegetation). The model incorporates theoretical and empirical
descriptions of transport processes associated with the gaseous, dissolved and particle phases to
reduce the required user-input. Furthermore, the ISMCM includes the modeling of rainfall events
and the associated intermedia transport processes such as precipitation scavenging of contaminants
from the atmosphere and contaminant transport in soils due to rain infiltration and runoff. The
ISMCM model was recently expanded by including a dynamic vegetation and biota compartments.
The vegetation compartment includes contaminant uptake from both the soil and the atmosphere and
the biota compartment accounts for contaminant uptake from both water and via the food chain. The
ISMCM model is currently used in the classroom environment in a course on Multimedia
Environmental Assessment.