Deposition of atmospheric reactive nitrogen species to an inland surface water body

Abstract

The transport, dispersion and deposition of chemical species present in the atmosphere are integral to biogeochemical cycling. Increased emissions to the atmosphere resulting from intensified anthropogenic activities can significantly increase the dispersion of material throughout the environment, and therefore affect these cycles, although impacts can be seen to be beneficial or detrimental, depending on the perspective adopted. In agriculture, inputs of additional material can be an important source of nutrients, while in excess, depending on chemical composition and properties, such inputs can lead to acidification, resulting in poor soil conditions. Deposition of chemical species to natural vegetation, that exceeds the natural background, always causes negative effects that can affect biological diversity.The present project aims to assess the contribution of atmospheric nitrogenous species, in the forms of dry and wet deposition, to alteration of the soluble nitrogen species composition of inland surface waters. To this end, we shall use as a model a reservoir that does not receive any form of effluent input, and that has no agricultural activity in its immediate vicinity. Quantification of atmospheric deposition will be performed considering reactive nitrogen present in the gas phase, in aerosols and in precipitation water. Analysis of soil samples along gradients at the margins of the reservoir will be used to identify any significant terrestrial inflows of nitrogen. Quantification of chemical species at the receptor (the reservoir) will be undertaken at different points, using appropriate experimental design, in order to understand the relative contributions of material arriving in the reservoir either already dissolved in water, or deposited from the atmosphere and subsequently contributing to the total dissolved nitrogen content. Models of dry deposition, together with the physical measurements, will be used to determine the annual fluxes of nitrogenous compounds. The work will ultimately enable estimation of the role of atmospheric deposition in transporting reactive nitrogen to the surface, and improve understanding of chemical exchange at the water/atmosphere interface. This will permit conclusions to be drawn concerning natural processes, such as eutrophication, that are governed largely by concentrations of dissolved nitrogen species, as well as any implications concerning the quality of potable water for human consumption. (AU)