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| Titel |
Nutrient and mercury deposition and storage in an alpine snowpack of the Sierra Nevada, USA |
| VerfasserIn |
C. Pearson, R. Schumer, B. D. Trustman, K. Rittger, D. W. Johnson, D. Obrist |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 12, no. 12 ; Nr. 12, no. 12 (2015-06-16), S.3665-3680 |
| Datensatznummer |
250117986
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| Publikation (Nr.) |
 copernicus.org/bg-12-3665-2015.pdf |
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| Zusammenfassung |
| Biweekly snowpack core samples were collected at seven sites along two
elevation gradients in the Tahoe Basin during two consecutive snow years to
evaluate total wintertime snowpack accumulation of nutrients and pollutants
in a high-elevation watershed of the Sierra Nevada. Additional sampling of
wet deposition and detailed snow pit profiles were conducted the following
year to compare wet deposition to snowpack storage and assess the vertical
dynamics of snowpack nitrogen, phosphorus, and mercury. Results show that, on
average, organic N comprised 48% of all snowpack N, while nitrate
(NO3--N) and TAN (total ammonia nitrogen) made up 25 and 27%,
respectively. Snowpack NO3--N concentrations were relatively uniform
across sampling sites over the sampling seasons and showed little difference
between seasonal wet deposition and integrated snow pit concentrations. These
patterns are in agreement with previous studies that identify wet deposition
as the dominant source of wintertime NO3--N deposition. However, vertical
snow pit profiles showed highly variable concentrations of NO3--N within
the snowpack indicative of additional deposition and in-snowpack dynamics.
Unlike NO3--N, snowpack TAN doubled towards the end of winter, which we
attribute to a strong dry deposition component which was particularly
pronounced in late winter and spring. Organic N concentrations in the
snowpack were highly variable (from 35 to 70%) and showed no clear
temporal, spatial, or vertical trends throughout the season. Integrated
snowpack organic N concentrations were up to 2.5 times higher than seasonal
wet deposition, likely due to microbial immobilization of inorganic N as
evident by coinciding increases in organic N and decreases in inorganic N in
deeper, aged snow. Spatial and temporal deposition patterns of snowpack P
were consistent with particulate-bound dry deposition inputs and strong
impacts from in-basin sources causing up to 6 times
greater enrichment at
urban locations compared to remote sites. Snowpack Hg showed little temporal
variability and was dominated by particulate-bound forms (78% on
average). Dissolved Hg concentrations were consistently lower in snowpack
than in wet deposition, which we attribute to photochemically driven gaseous
re-emission. In agreement with
this pattern is a significant positive relationship between snowpack Hg and
elevation, attributed to a combination of increased snow accumulation at
higher elevations causing limited light penetration and lower photochemical
re-emission losses in deeper, higher-elevation snowpack. Finally, estimates
of basin-wide loading based on spatially extrapolated concentrations and a
satellite-based snow water equivalent reconstruction model identify snowpack chemical loading from
atmospheric deposition as a substantial source of nutrients and pollutants to
the Lake Tahoe Basin, accounting for 113 t of N, 9.3 t of P, and 1.2 kg of
Hg each year. |
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