Radionuclide resuspension across ecosystems and environmental disturbances.

Exposure assessment from radionuclides and other soil-bound contaminants often requires quantifying the amount of contaminant resuspended in the air. Rates and controlling factors of radionuclide resuspension and wind erosion of soil are clearly related but have largely been studied separately. Here, we review both and then integrate wind erosion measurements with the radiological resuspension paradigm to provide better estimates of resuspension factors across a broad range of ecosystems and environmental conditions. Radionuclide resuspension by wind was initially investigated during the era of aboveground nuclear weapons testing. Predictive dose models were developed from empirically-derived ratios of air and soil concentrations, otherwise called the resuspension factor. Resuspension factors were shown to generally predict radionuclide concentrations in air, but they were site-specific and largely derived from the arid and semi-arid environments surrounding nuclear weapons testing locations. In contrast, wind erosion studies from the agricultural and environmental sciences have produced more mechanistic models and a relatively robust data set of wind erosion rates and model parameters across a range of ecosystems. We sequentially show the mathematics linking measured sediment flux from wind erosion rate measurements to resuspension factors using the concept of transport capacity and its relationship to the deposition velocity. We also describe the conceptual framework describing how resuspension factors change through time and the mathematical models describing this decrease. We then show how vertical mass flux measurements across ecosystems were categorized and used to calculate ecosystem-based resuspension factors. These calculations allow generalized estimation of radionuclide resuspension factors across ecosystem types as a function of disturbance and as input for dose calculations.

Potential sources of bacteriological pollution for two bays with marinas in Trinidad.

Welcome Bay and Chaguaramas Bay in the northwest peninsula of Trinidad contain large marinas and smaller sections of bathing beaches. Bacteriological surveys were conducted at both bays to assess water quality and to determine potential sources of pollution. These surveys were conducted during the wet season of 1996 and the dry season of 1997. Eleven sample stations were established at Welcome Bay and 12 at Chaguaramas Bay. Freshwater samples were collected from rivers and drains within the survey area. Marine water samples were collected from marinas, bathing beaches and inshore and outer areas at both bays. Five water samples were collected from each sampling station during the wet season of 1996 and six during the dry season of 1997. The membrane filter technique was used to determine faecal coliform and Escherichia coli levels in all samples. There was a seasonal effect on water quality, with significantly higher faecal coliform levels in the wet season, when water quality was not in compliance with international standards. This represents a potential health risk in bathing areas. Water quality was better at the outer area of both bays. Water quality at the inner bay areas was most likely adversely affected by land-based sources of pollution identified in this study. These sources include three drains and two rivers, which discharged into the bays. Yachts were apparently not a source of sewage pollution: there was no significant relationship between yacht number and faecal coliform levels.