Publication Date:
2014-12-12
Description:
Samples from two ice cores drilled at Lomonosovfonna, Svalbard, covering the period 1957–2009, and 1650–1995, respectively, were analyzed for NO 3 − concentrations, and NO 3 − stable isotopes ( δ 15 N and δ 18 O). Post-1950 δ 15 N has an average of (−6.9 ± 1.9) ‰, which is lower than the isotopic signal known for Summit, Greenland, but agrees with values observed in recent Svalbard snow and aerosol. Pre-1900 δ 15 N has an average of (4.2 ± 1.6) ‰ suggesting that natural sources, enriched in the 15 N-isotope, dominated before industrialization. The post-1950 δ 18 O average of (75.1 ± 4.1) ‰ agrees with data from low and polar latitudes, suggesting similar atmospheric NO y (NO y = NO + NO 2 + HNO 3 ) processing pathways. The combination of anthropogenic source δ 15 N and transport isotope effect was estimated as −29.1 ‰ for the last 60 years. This value is below the usual range of NO x (NO x = NO + NO 2 ) anthropogenic sources which is likely the result of a transport isotope effect of –32 ‰. We suggest that the δ 15 N recorded at Lomonosovfonna is influenced mainly by fossil fuel combustion, soil emissions and forest fires; the first and second being responsible for the marked decrease in δ 15 N observed in the post-1950s record with soil emissions being associated to the decreasing trend in δ 15 N observed up to present time, and the third being responsible for the sharp increase of δ 15 N around 2000.
Print ISSN:
0148-0227
Topics:
Geosciences
,
Physics
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