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Water-Soluble Organic Nitrogen in High Mountain Snow Samples from Central Japan

Category: Interaction between Air and Precipitation Chemistry

Volume: 16 | Issue: 3 | Pages: 632-639
DOI: 10.4209/aaqr.2015.04.0256
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Tomoki Mochizuki1, Kimitaka Kawamura 1, Kazuma Aoki2

  • 1 Institute of Low Temperature Science, Hokkaido University, N19 W8, Kita-ku Sapporo 060-0819, Japan
  • 2 Department of Earth Science, Faculty of Science, University of Toyama, 3190, Gofuku, Toyama 930-8555, Japan

Highlights

Water-soluble organic nitrogen contributes to 15% of water-soluble total nitrogen.

Concentrations of WSON in high mountain snowpack samples are relatively low.

WSON is significantly less abundant than WSOC with the ratio of 24.

WSON in snow samples positively correlates with a dust tracer (nss-Ca).

WSON may be seriously decomposed during long-range transport.


Abstract

We measured water-soluble organic nitrogen (WSON) in snow pit samples, which were collected at the Murodo-Daira snowfield near the summit of Mt. Tateyama, central Japan in 2008, 2009, and 2011. The concentrations of WSON ranged from 12.8 to 96.7 ng g–1, which were significantly lower than those reported in continental wet deposition samples from the Asian continent. WSON may be largely diluted in the snow samples during snowing processes over the high mountains. We found that WSON significantly correlated with nss-Ca2+ and water-soluble organic carbon (WSOC). Concentrations of WSON are likely controlled by the intensity of Asian dust events. Contributions of WSON to water soluble total nitrogen (WSTN) in snow pit sequence was found to be 15 ± 10%, which is lower than those (63–91%) of reference dust materials collected in China. Mass concentration ratio of WSOC/WSON was on average 23.7, which is significantly higher than the C/N weight ratio (5.6) calculated from the Redfield ratio. This result suggests that WSOC is largely produced by secondary photochemical oxidation of anthropogenic volatile organic compounds during the transport from East Asia to the high mountain areas in Japan. On the other hand, WSON may be contributed from Asian dusts from arid areas in China whereas water-soluble inorganic nitrogen may be derived from pollution sources.

Keywords

Water-soluble organic nitrogen High mountain snow Central Japan Long-range atmospheric transport East Asia


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