| Title | Wet deposition at the base of Mt Everest: Seasonal evolution of the chemistry and isotopic composition |
| Abstract | The chemistry of wet deposition was investigated during 2012 e 2014 at the Pyramid International
Laboratory in the Upper Khumbu Valley, Nepal, at 5050 m a.s.l., within the Global Atmosphere Watch
(GAW) programme. The main hydro-chemical species and stable isotopes of the water molecule were
determined for monsoon rain (JulyeSeptember) and snow samples (OctobereJune). To evaluate the
synoptic-scale variability of air masses reaching the measurement site, 5 day back-trajectories were
computed for the sampling period. Ion concentrations in precipitation during the monsoon were low
suggesting that they represent global regional background concentrations. The associations between ions
suggested that the principal sources of chemical species were marine aerosols, rock and soil dust, and
fossil fuel combustion. Most chemical species exhibited a pattern during the monsoon, with maxima at
the beginning and at the end of the season, partially correlated with the precipitation amount. Snow
samples exhibited significantly higher concentrations of chemical species, compared to the monsoon
rainfall observations. Particularly during 2013, elevated concentrations of NO3, SO42 and NH4 were
measured in the first winter snow event, and in May at the end of the pre-monsoon season. The analysis
of large-scale circulation and wind regimes as well as atmospheric composition observations in the
region indicates the transport of polluted air masses from the Himalayan foothills and Indian subcontinent
up to the Himalaya region. During the summer monsoon onset period, the greater values of
pollutants can be attributed to air-mass transport from the planetary boundary layer (PBL) of the Indo-
Gangetic plains. Isotopic data confirm that during the monsoon period, precipitation occurred fromwater
vapor that originated from the Indian Ocean and the Bay of Bengal; by contrast during the non-monsoon
period, an isotopic signature of more continental origin appeared, indicating that the higher recorded
NO3 and SO4 2 concentrations could be ascribed to a change in air circulation patterns. A comparison of
recent monsoon deposition chemistry with data from the 1990's shows similar levels of contaminants in
the rainfall. However, non-monsoon deposition can be significant, as it largely contributed to the ion wet
deposition fluxes for all analyzed species in 2013. |
| Source | Atmospheric environment (1994) 146, pp. 100–112 |
| Keywords | snowsulfatenitrateBack-trajectoriesd-excessmonsoon |
| Journal | Atmospheric environment (1994) |
| Editor | Pergamon., Oxford, Regno Unito |
| Year | 2016 |
| Type | Articolo in rivista |
| DOI | 10.1016/j.atmosenv.2016.08.056 |
| Authors | Balestrini R., Delconte C.A., Sacchi E., Wilson A.M., Williams M.W., Cristofanelli P., Putero D. |
| Text | 360221 2016 10.1016/j.atmosenv.2016.08.056 Scopus 2 s2.0 84993929180 ISI Web of Science WOS 000388051700010 snow sulfate nitrate Back trajectories d excess monsoon Wet deposition at the base of Mt Everest Seasonal evolution of the chemistry and isotopic composition Balestrini R., Delconte C.A., Sacchi E., Wilson A.M., Williams M.W., Cristofanelli P., Putero D. a CNR IRSA e Water Research Institute, Brugherio, MB, Italy b Department of Earth and Environmental Sciences, University of Pavia, Pavia, Italy c Institute of Arctic and Alpine Research, University of Colorado at Boulder, USA d CNR ISACeInstitute for Atmospheric Sciences and Climate, Bologna, Italy The chemistry of wet deposition was investigated during 2012 e 2014 at the Pyramid International Laboratory in the Upper Khumbu Valley, Nepal, at 5050 m a.s.l., within the Global Atmosphere Watch GAW programme. The main hydro chemical species and stable isotopes of the water molecule were determined for monsoon rain JulyeSeptember and snow samples OctobereJune . To evaluate the synoptic scale variability of air masses reaching the measurement site, 5 day back trajectories were computed for the sampling period. Ion concentrations in precipitation during the monsoon were low suggesting that they represent global regional background concentrations. The associations between ions suggested that the principal sources of chemical species were marine aerosols, rock and soil dust, and fossil fuel combustion. Most chemical species exhibited a pattern during the monsoon, with maxima at the beginning and at the end of the season, partially correlated with the precipitation amount. Snow samples exhibited significantly higher concentrations of chemical species, compared to the monsoon rainfall observations. Particularly during 2013, elevated concentrations of NO3, SO42 and NH4 were measured in the first winter snow event, and in May at the end of the pre monsoon season. The analysis of large scale circulation and wind regimes as well as atmospheric composition observations in the region indicates the transport of polluted air masses from the Himalayan foothills and Indian subcontinent up to the Himalaya region. During the summer monsoon onset period, the greater values of pollutants can be attributed to air mass transport from the planetary boundary layer PBL of the Indo Gangetic plains. Isotopic data confirm that during the monsoon period, precipitation occurred fromwater vapor that originated from the Indian Ocean and the Bay of Bengal; by contrast during the non monsoon period, an isotopic signature of more continental origin appeared, indicating that the higher recorded NO3 and SO4 2 concentrations could be ascribed to a change in air circulation patterns. A comparison of recent monsoon deposition chemistry with data from the 1990 s shows similar levels of contaminants in the rainfall. However, non monsoon deposition can be significant, as it largely contributed to the ion wet deposition fluxes for all analyzed species in 2013. 146 Published version http //www.sciencedirect.com/science/article/pii/S1352231016306495 18/08/2016 Wet deposition at the base of Mt Everest Seasonal evolution of the chemistry and isotopic composition Wet deposition at the base of Mt Everest Seasonal evolution of the chemistry and isotopic composition atmenv_acidrain2016.pdf Articolo in rivista Pergamon. 1352 2310 Atmospheric environment 1994 Atmospheric environment 1994 Atmos. environ. 1994 carloandrea.delconte DELCONTE CARLO ANDREA davide.putero PUTERO DAVIDE raffaella.balestrini BALESTRINI RAFFAELLA |
