| Title | Wet Deposition Chemistry at a High Elevation Site in the Khumbu Valley (Nepal Himalaya). Implication for the N Biogeochemical Cycle |
| Abstract | Among the alpine environments of the world, the region of Mount
Everest is a unique ecosystem with a degree of biodiversity among the
highest existing, but characterized by a recognized fragility and low
resilience. There is a growing concern about the potential effects of global
warming and other large scale phenomena (e.g. atmospheric brown cloud)
on aquatic undisturbed systems in the Himalayan region.
The chemistry of wet deposition was investigated at the Pyramid
International Laboratory in the northernmost portion of the Khumbu
Valley, at 5050 m asl, during 2007-2008, and since June 2012 until now,
within the GAW programme. The main hydro-chemical species and the
stable isotopes of oxygen ( 18O) and deuterium ( 2H) were determined
on precipitation samples.
The obtained results revealed a very low ionic content, also compared
to precipitation sampled in remote sites from the Tibetan Plateau. The
temporal variations of NO3 and SO4 exhibited maximum concentrations
at the beginning and ending phases of monsoon. A similar trend is observed
for the carbonaceous and ionic aerosols, at the same site. Also the isotopic
composition is strongly related to the amount of precipitation, withdepleted values characterizing the central monsoon period. Results suggest
that during monsoon the air masses reaching the Pyramid site were almost
completely depleted of potential contaminants originated from the lower
urbanized Asian areas.
The low nitrogen concentrations associated with very modest amounts
of precipitation have produced nitrogen loads considerably lower than
those measured in high-altitude environments in Europe and North
America. Higher N loads were reported for other different ecosystems in
the most remote regions of the world, as the Northern Africa dry savannah
and for the Central Amazonia tropical rain forest. These results will be
discussed further considering the nitrogen level in surface waters collected
in the high Khumbu valley catchment. |
| Source | International Conference on Mountains and Climate Change "High Summit", Lecco, 23-25 Ottobre 2013 |
| Keywords | nitratesulfateprecipitationwater isotopes |
| Year | 2014 |
| Type | Contributo in atti di convegno |
| Authors | RAFFAELLA BALESTRINI1, ELISA SACCHI2, CARLO DELCONTE1, ALANA WILSON3, MARK WILLIAMS3 |
| Text | 309675 2014 nitrate sulfate precipitation water isotopes Wet Deposition Chemistry at a High Elevation Site in the Khumbu Valley Nepal Himalaya . Implication for the N Biogeochemical Cycle RAFFAELLA BALESTRINI1, ELISA SACCHI2, CARLO DELCONTE1, ALANA WILSON3, MARK WILLIAMS3 1 Italian National Research Council, Water Research Institute, CNR IRSA, Italy 2 Department of Earth and Environmental Sciences, University of Pavia, and Italian National Research Council, Geosciences and Earth Resources Institute, CNR IGG, Italy 3 Institute of Arctic and Alpine Research, University of Colorado, Boulder, USA Among the alpine environments of the world, the region of Mount Everest is a unique ecosystem with a degree of biodiversity among the highest existing, but characterized by a recognized fragility and low resilience. There is a growing concern about the potential effects of global warming and other large scale phenomena e.g. atmospheric brown cloud on aquatic undisturbed systems in the Himalayan region. The chemistry of wet deposition was investigated at the Pyramid International Laboratory in the northernmost portion of the Khumbu Valley, at 5050 m asl, during 2007 2008, and since June 2012 until now, within the GAW programme. The main hydro chemical species and the stable isotopes of oxygen 18O and deuterium 2H were determined on precipitation samples. The obtained results revealed a very low ionic content, also compared to precipitation sampled in remote sites from the Tibetan Plateau. The temporal variations of NO3 and SO4 exhibited maximum concentrations at the beginning and ending phases of monsoon. A similar trend is observed for the carbonaceous and ionic aerosols, at the same site. Also the isotopic composition is strongly related to the amount of precipitation, withdepleted values characterizing the central monsoon period. Results suggest that during monsoon the air masses reaching the Pyramid site were almost completely depleted of potential contaminants originated from the lower urbanized Asian areas. The low nitrogen concentrations associated with very modest amounts of precipitation have produced nitrogen loads considerably lower than those measured in high altitude environments in Europe and North America. Higher N loads were reported for other different ecosystems in the most remote regions of the world, as the Northern Africa dry savannah and for the Central Amazonia tropical rain forest. These results will be discussed further considering the nitrogen level in surface waters collected in the high Khumbu valley catchment. Proceedings International Conference on Mountains and Climate Change High Summit Elisa Wuillermoz, Roberta Toffolon, Alberto Cortinovis 978 88 8080 148 1 1 International Conference on Mountains and Climate Change High Summit Lecco 23 25 Ottobre 2013 Internazionale Su invito Contributo in atti di convegno carloandrea.delconte DELCONTE CARLO ANDREA raffaella.balestrini BALESTRINI RAFFAELLA |
