Chemical Fate & Transport

An understanding of the behavior and fate of chemicals in the environment is central to most investigations of contamination and potential impacts. State-of-the-art chemical fate-and-transport assessments require a comprehensive understanding both of the movement of chemicals in air, water, and subsurface and of the physical, chemical, and biological processes that influence the ultimate disposition of those chemicals in the environment. Exponent’s scientists and engineers have mastered these facets and have advised clients on these matters for over 30 years. We have advised numerous government entities and industrial clients and have published hundreds of peer-reviewed scientific articles on questions related to chemical fate and transport, including the sources of chemicals, changes that occur in the environment, the transport of these chemicals, reconstruction of historical chemical releases, and exposure assessments. Exponent’s work combines empirical data, basic principles of chemistry and microbiology, and fate and transport models, and we have been recognized for our investigatory work, expert opinions, and publications on the fate and transport of chemicals in toxic tort, property damage, cost allocation, and Natural Resource Damage Assessment (NRDA) cases nationwide.

Exponent’s chemical fate-and-transport consulting and expert services cover a broad spectrum of chemical contaminants across environmental media (e.g., air, water, groundwater, soil, soil vapor, surface sediment, and house dust). The first step is typically a site-specific conceptual site model (CSM) to identify the key pathways from sources to receptors that require evaluation in a particular scenario. Next, we evaluate the reactions (abiotic and/or biological) that alter chemical forms and distributions in various media. Finally, we estimate the exposure to human and ecological receptors. Geographical information systems (GIS) and advanced data analytics are used to evaluate spatial and temporal trends in contaminant concentrations, and numerical modeling is employed to simulate chemical movement and concurrent transformation in air, unsaturated soil, groundwater, sediments, and water bodies (rivers, lakes, estuaries, oceans).

Depending on project objectives, the numerical models developed by Exponent can range from simple to complex, including state-of-the-art geochemical and hydrological models developed for specific sites to understand chemical mobility in complicated environmental systems.

Exponent provides unique synergies between our core expertise in environmental chemistry and other disciplines where needed, including hydrology, meteorology, microbiology, and investigative and failure analysis, engineering expertise in materials and structures, and fires and explosions. Exponent employs this expertise when evaluating the source, mechanism, and timing of environmental releases. In addition, Exponent’s environmental scientists and engineers work closely with ecological and health scientists to understand exposure and effects. This cooperation among the diverse Exponent practices provides our clients with unmatched value and resources in successfully managing their regulatory and litigation needs.