A successive correction modeling technique to identify sources and evaluate impact of compounds detected by the TAGA 6000E

The US Environmental Protection Agency Environmental Response Team (US EPA/ERT) was requested by Region 4 to verify or refute periodic exceedances of the short-term thresholds of several volatile organic compounds (VOCs) near a petroleum recovery Superfund site. During ambient air mobile monitoring for VOCs within a residential neighborhood, a plume was detected adjacent to a Superfund site containing contaminated subsurface impoundments. The site, for which the mobile monitoring was performed, was expected to emit several of the same compounds as those detected in the plume. The objective then became to identify the source(s) responsible for the elevated concentrations. Therefore, a successive correction technique (SCT) was developed to setup several Fugitive Dust Model (FDM) runs to determine the emission rates necessary, at the sources of concern, to produce the ambient concentrations detected during mobile monitoring. Locations of other suspected sources were included in the modeling study, including: a creek, a groundwater treatment plant, and a nearby enclosed excavation site. Two stationary samplers aided in identifying the latter two sources as suspected sources. After several investigative modeling runs using the SCT, it was found that the excavation site was the most likely candidate responsible for the impact. The source term was obtained and its impact on a nearby neighborhood was evaluated