Nitrate stable isotopes and major ions in snow and ice samples from four Svalbard sites

Increasing reactive nitrogen (N-r) deposition in the Arctic may adversely impact N-limited ecosystems. To investigate atmospheric transport of N-r to Svalbard, Norwegian Arctic, snow and firn samples were collected from glaciers and analysed to define spatial and temporal variations (1 10 years) in major ion concentrations and the stable isotope composition (delta N-15 and delta O-18) of nitrate (NO3-) across the archipelago. The delta N-15(NO3-) and delta O-18(NO3-) averaged -4 parts per thousand and 67 parts per thousand in seasonal snow (2010-11) and -9 parts per thousand and 74 parts per thousand in firn accumulated over the decade 2001-2011. East-west zonal gradients were observed across the archipelago for some major ions (non-sea salt sulphate and magnesium) and also for delta N-15(NO3-) and delta O-18(NO3-) in snow, which suggests a different origin for air masses arriving in different sectors of Svalbard. We propose that snowfall associated with long-distance air mass transport over the Arctic Ocean inherits relatively low delta N-15(NO3-) due to in-transport N isotope fractionation. In contrast, faster air mass transport from the north-west Atlantic or northern Europe results in snowfall with higher delta N-15(NO3-) because in-transport fractionation of N is then time-limited

Preface:Nitrogen and global change

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Global Nutrient Flows and Cycling in Food Systems

Plants require 14 nutrient elements in specific amounts for growth and development, in addition to carbon dioxide, water, and photosynthetic active radiation. The most limiting nutrient elements are nitrogen, phosphorus, and potassium. This chapter briefly summarizes the driving forces of nutrient cycling and the changes in global nutrient flows and balances in agricultural systems and food systems, with a focus on nitrogen and phosphorus in food production‐consumption systems. The nitrogen cycle is a most complex nutrient cycle. Nitrogen exists in different forms, most of which are biologically, photochemically, or radiatively active. The phosphorus cycle serves as an example for the cycling of “immobile” elements, such as metals, cadmium, and magnesium. The availability of phosphorus in most soils limits crop production around the world. The specialization and agglomeration of food production systems was facilitated by transnational corporations