Lakes typically are hydrologically downstream from watersheds, and outputs from watersheds, including toxic materials such as arsenic (As), can accumulate in lake sediments at concentrations that pose substantive health or environmental risks. Our previous studies documented a total inventory of ~537 kg of As in >19,000 metric tons of sediment and porewaters in Little Lake Jackson, Highlands County, Florida. This resulted from monosodium methylarsonate (MSMA) pesticide applications to golf courses and lawns in topographically higher areas of the watershed. Although MSMA percolates downward in soils of many areas, this lake was susceptible to As accumulation because surface waters as well as impervious clay and sand lenses in local soils directed pesticide leachates towards the lake. Total As content in lake sediments exceeded the consensus-based sedimentary concentration for probable toxicity effects in freshwater benthic fauna. Subsurface waters in shallow test wells reached 11 times the federal standard for As in drinking waters, potentially exposing local residential wells. Our subsequent studies document total As, As(III), As(V), DMA, AsB, and MMA content in fish, crustacean, and reptile tissues at various levels in food chains of two MSMA-contaminated lakes. Total As concentrations in blue tilapia were as high as 11.6 ppm in organs and 1.5 ppm in muscle tissue, which is comparable to total As values measured in tilapia from the Human Blackfoot Disease area of Taiwan, where As in well waters leads to necrosis and need for amputation in humans. Bluegills showed total As content as high as 10.8 ppm in organs and 1.3 ppm in muscle tissue. Local subsurface geology in the watersheds of these lakes apparently led to unexpectedly high accumulations of As that might pose risks for aquatic fauna, as well as for humans who consume the aquatic fauna.
Discipline Categories: Geology and Health, Environmental Geoscience, LimnogeologyPreferred Presentation Type: Poster