A Mass Balance for Mercury in the San Francisco Bay Area

TitleA Mass Balance for Mercury in the San Francisco Bay Area
Publication TypeJournal Article
Year of Publication2006
AuthorsMatthew Macleod, Thomas E McKone, Donald Mackay
JournalEnvironmental Science and Technology
Volume39
Chapter
Pagination6721-6729
Keywordscontaminated sediments, Environmental Chemistry, Exposure and Risk Group, historical contamination, indoor environment department, multimedia, pollutant cycling, pollutant fate and transport modeling, san francisco estuary
Abstract

We develop and illustrate a general regional multi-species model that describes the fate and transport of mercury in three forms, elemental, divalent, and methylated, in a generic regional environment including air, soil, vegetation, water and sediment. The objectives of the model are to describes the fate of the three forms of mercury in the environment and determine the dominant physical sinks that remove mercury from the system. Chemical transformations between the three groups of mercury species are modeled by assuming constant ratios of species concentrations in individual environmental media. We illustrate and evaluate the model with an application to describe the fate and transport of mercury in the San Francisco Bay Area of California. The model successfully rationalizes the identified sources with observed concentrations of total mercury and methyl mercury in the San Francisco Bay Estuary. The mass balance provided by the model indicates that continental and global background sources control mercury concentrations in the atmosphere but loadings to water in the San Francisco Bay estuary are dominated by runoff from the Central Valley catchment and re-mobilization of contaminated sediments deposited during past mining activities. The model suggests that the response time of mercury concentrations in the San Francisco Bay estuary to changes in loadings is long, of the order of 50 years.