EVALUATION OF CHEMICAL SPILL CONSEQUENCES USING MODELING1

Abstract

ABSTRACT A wide variety of chemicals are shipped in bulk world-wide, raising concerns regarding the ecological and human health risks of hazardous chemical spills. A screening analysis was performed using the chemical spill model, CHEMMAP, to estimate the fate and concentrations of selected chemicals in water and the atmosphere above the water, as well as the potential for ecological and human health impacts that would result from a spill into a large channel. A representative sample of chemicals, including floating, sinking, soluble and insoluble chemicals, were evaluated using typical shipping volumes to assess worst-case scenarios. The model uses physical and chemical properties to simulate three dimensional fate processes, including: (1) spreading (floating liquids), (2) transport (3) dispersion, (4) evaporation-volatilization, (5) entrainment (liquids), (6) dissolution, (7) partitioning, (8) sedimentation, (9) resuspension and (10) degradation. Estimates of the distribution of chemical (mass and concentrations) on the water surface, on shorelines, in the water column, in the sediments, and in the lower atmosphere (in the zone where there would be exposure to humans and wildlife) are calculated over time. Based on model outputs, it is possible to select chemicals that would have the highest ecological and human health consequences after a spill. Chemicals that would have the greatest ecological consequence are those that are not highly volatile, disperse readily, are soluble, and have the lowest threshold of concern. Similarly, it is possible to select chemicals that would have the greatest human health concern, which would be chemicals that are more volatile and present hazards via the inhalation pathway. The model results can be used to indicate safe distances for responders, as well as the area of water that may be contaminated above thresholds of concern. This paper describes the model's application to hypothetical spills of selected chemicals and the rank order of these chemicals based on how hazardous they are to human health and the ecosystem.