EPA-Expo-Box (A Toolbox for Exposure Assessors)
Water and Sediment
Estimates of contaminant concentrations in water and/or sediment are needed for assessing exposure via potential exposure pathways involving these media—ingestion, dermal contact, and/or inhalation. These media concentrations may also be needed as data inputs for modeling the fate and transport of contaminants in water and the transfer of contaminants to other media (e.g., vegetation used as a food source, volatilization to air).
Characterizing contaminant concentrations for an exposure scenario is typically accomplished using some combination of the following approaches:
- Sampling water and sediment and measuring contaminant concentrations
- Modeling the concentration distribution based on source strength, media transport, and chemical transformation processes
- Using existing, available measured concentration data collected for related analysis or compiled in databases
A number of sampling techniques or protocols have been established for monitoring and characterizing water and sediment contamination. Sampling protocols are necessary to ensure that samples are collected in a proper manner using suitable equipment to account for environmental conditions. Analytical methods for measuring concentrations of contaminants in water and sediment may include methods required for specific contaminants or groups of contaminants that are regulated by EPA or methods for unregulated contaminants or groups of contaminants of interest.
In the absence of monitoring data, models may be used to estimate the concentrations of contaminants in water and sediment, such as the following. By modeling contaminant movement and concentrations in freshwater, marine, and estuarine environments, researchers can better understand how these contaminants affect the quality of water, sediment, and aquatic biota. Groundwater models simulate groundwater flow through the subsurface (and possible migration to surface water) and inform subsurface contaminant transport models.
There are a number of information sources that provide monitoring data on contaminant concentrations in surface water and sediment (also see the Aquatic Biota Module of the Media Tool Set). Some of these data come from national surveys—such as the National Lakes Assessment—that help to characterize the chemical, biological, and physical water quality of the Nation’s waters; identify actions to prevent pollution; and evaluate the effectiveness of protection and restoration efforts.