Title : Assessment of the supply of uranium from the atmosphere of a northern city
Abstract:
A geochemical study of particulate matter in the urban atmosphere was performed both for summer and winter (soluble and solid phases of snowpack) seasons. The study indicates the formation of anthropogenic anomalies of heavy metals, rare elements and radioactive elements in the near-surface atmosphere. The actinides of interest form extensive weak anomalies in the downtown U. Summertime PM consist of solid particles of different sizes. U are mostly contained in the dust fraction (PM10-100) together with siderophile elements. Wintertime PM consists of finer particles, mostly PM10. Specific mineral phases correlating with actinides deposited on the soil surface in the zone of anthropogenic impact are carbonates and amphiboles for U. The U concentrations uniformly decrease in the system: soils – summertime PM – wintertime PM (snow) – aerosols and gases (snow). The majority of U (about 90%) is deposited during the summer season. Wintertime solid deposition accounts for about 10% of the total atmospheric deposition of U. Wintertime deposition of U with aerosols and gases is minimal. The total deposition of U in Yakutsk is estimated to be about 16 mg/m2·year. At sites of strong anomalies, this value can exceed 40-50 mg/m2·year. The sources of U into the near-surface atmosphere are mainly fugitive dust, vehicle emissions, and to a lesser extent, emissions from power generating facilities. The deposition of U in mobile forms (in the soluble phase of snowpack) allows them to penetrate deep into the active layer with meltwater and concentrate in soil water. Based on the snow contamination index, wintertime air pollution is estimated to be low over most of the city and moderate in areas of high traffic and near the power facilities.
