SELENIUM CYCLING THROUGH AGRICULTURAL GRASSLANDS IN THE UK - BUDGETING THE ROLE OF THE ATMOSPHERE

Two idealised Se budget scenarios have been generated to assess the role of atmospheric cycling on the Se status of UK agriculture grasslands. Based on a thorough literature review, the budgets demonstrate that varying the factors for losses by volatilisation from plants and soils or inputs by deposition may significantly affect the net balance of a grassland. The contribution of wet, dry vapour and particulate deposition inputs to the soil-herbage system are assessed and are thought to be dominated by a soluble form in wet deposition. The total input is calculated to be typically in the range 0.2-0.7 mg m-2 year-1. Volatile losses from the soil are difficult to derive accurately, but are estimated to range between 0.1 and 10 mg m-2 years-1. The budget suggests there is a net input of Se to herbage from the atmosphere, even in remote/rural locations, where inputs are generally low. The implications for the availability of Se to plants and grazing livestock are briefly considered.