Abstract
ABSTRACTWe 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.
Highlights
The annual global emissions of water-soluble inorganic nitrogen (WSIN) and water-soluble organic nitrogen (WSON) in particulate phase were estimated to be 34 and 3.9 Tg-N, respectively (Neff et al, 2002)
WSON levels reported in the Murodo-Daira site are similar to those of the ice floe samples from the Fram Strait near the Arctic Ocean (Thomas et al, 1995), suggesting that WSON concentrations in the Japanese high mountain snow samples are near the background level on the Earth
We found that WSON does not comprise of major fraction of water-soluble total nitrogen (WSTN) in the Japanese high mountain snow samples
Summary
The annual global emissions of water-soluble inorganic nitrogen (WSIN) and water-soluble organic nitrogen (WSON) in particulate phase were estimated to be 34 and 3.9 Tg-N, respectively (Neff et al, 2002). WSON accounts for 10– 40% of the water-soluble total nitrogen (WSTN) on a global scale (Cornell, 2011). Cape et al (2011) reported that WSON concentrations in wet deposition are increasing recently; relatively high concentrations of WSON in wet deposition are observed in China due to the enhanced anthropogenic sources (Zhang et al, 2008). Increased emissions of nitrogen species to the air control the nitrogen saturation in terrestrial and aquatic ecosystems (e.g., Aber et al, 1989; Cornell et al, 1995), and affect human health by decreasing the quality of air and water (e.g., Harrison and Yin, 2000; Zhang and Anastasio, 2001). Global nitrogen cycle should be influenced by enhanced human activity.
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