Aerosol and Precipitation Chemistry at a Remote Himalayan Site in Nepal

Shrestha, Arun B.; Wake, Cameron P.; Dibb, Jack E.; Whitlow, Sallie I.

doi:10.1080/027868202753571269

Cited by 76 publications

(39 citation statements)

References 28 publications

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“…The dominance of crustal sources at Gulmarg is mainly due to transported dust. The dominance of crustal fraction has been reported in snow samples worldwide (Mayewski et al, 1983;Shrestha et al, 2002). Anthropogenic contribution (29.9%) at this site is mainly due to various airmasses such as African, Middle East and European origin.…”

Section: Source Contribution At Gulmargmentioning

confidence: 97%

Long Range Transport and Wet Deposition Fluxes of Major Chemical Species in Snow at Gulmarg in North Western Himalayas (India)

Kumar

Singh

Gupta

et al. 2016

Aerosol Air Qual. Res.

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The study reports snow chemistry and long range transport of pollutants at Gulmarg in north-western Himalayan region of India during winters of 2012-2013. The pH of snowmelt varied between 5.16 and 7.68 with an average of 5.90. The frequency distribution of pH of snowmelt showed that the maximum number of samples (31%) had pH between 6.81 and 7.20. However, 12% samples were observed to be acidic (below 5.6 respectively. Both local emissions as well as long range transport (LRT) of pollutants were found to be the sources of these ionic species. Backward airmass trajectory calculations showed that this site received airmasses from six major sectors i.e., i) North Atlantic Ocean origin (NAO), ii) African origin (Af), iii) Middle East origin (ME), iv) European origin (Eu), v) Western India origin (InW), vi) Pakistan origin (Pk). The highest average pH (7.58) of the snowfall was noticed during InW airmasses which had the lowest ratios of nssSO 4 2-/nssCa 2+ and NO 3 -/nssCa 2+ . Very high pH has been observed in precipitation samples at Indian sites due to buffering of acidic components by atmospheric dust rich in CaCO 3 . The lowest pH (4.94) was noticed for ME airmasses which had the highest nssSO 4 2-/nssCa 2+ and NO 3 -/nssCa 2+ ratios. Data of present study was compared with a study reported almost three decades ago. We noticed a drastic increase in the concentrations of anthropogenic components such as nssSO 4 2-(114%), NO 3 -(109%) and NH 4 + (90%). This is probably due to increase in LRT of pollutants as well as local activities during past three decades.

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Section: Source Contribution At Gulmargmentioning

confidence: 97%

Long Range Transport and Wet Deposition Fluxes of Major Chemical Species in Snow at Gulmarg in North Western Himalayas (India)

Kumar

Singh

Gupta

et al. 2016

Aerosol Air Qual. Res.

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“…During the post-monsoon period and winter, which correspond to drier conditions, a rise in NH + 4 concentration is observed in the atmosphere and a clear strong peak is usually recorded during the pre-monsoon season. Dry and wet deposition processes of both particulate NH + 4 and gaseous NH 3 result in high concentration peaks on the surface snow, which may subsequently be amplified by post-depositional processes such as snow sublimation (Ginot et al, 2001) or reaction with HNO 3 absorbed on the snow layers Shrestha et al, 2002). In winter, westerly circulation associated with distant or reduced sources may generate low NH + 4 concentration in the snow layers; but these layers are usually scarce (very dry conditions in winter) and often not preserved in the snow column (snow remobilized into the atmosphere due to strong winds at high elevations in winter, Wagnon et al, 2013).…”

Section: Datingmentioning

confidence: 99%

A 10 year record of black carbon and dust from a Mera Peak ice core (Nepal): variability and potential impact on melting of Himalayan glaciers

et al. 2014

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Abstract.A shallow ice core was extracted at the summit of Mera Peak at 6376 m a.s.l. in the southern flank of the Nepalese Himalaya range. From this core, we reconstructed the seasonal deposition fluxes of dust and refractory black carbon (rBC) since 1999. This archive presents well preserved seasonal cycles based on a monsoonal precipitation pattern. According to the seasonal precipitation regime in which 80 % of annual precipitation falls between June and September, we estimated changes in the concentrations of these aerosols in surface snow. The analyses revealed that mass fluxes are a few orders of magnitude higher for dust (10.4 ± 2.8 g m −2 yr −1 ) than for rBC (7.9 ± 2.8 mg m −2 yr −1 ). The relative lack of seasonality in the dust record may reflect a high background level of dust inputs, whether from local or regional sources. Over the 10-year record, no deposition flux trends were detected for any of the species of interest. The data were then used to simulate changes in the surface snow albedo over time and the potential melting caused by these impurities. Mean potential melting caused by dust and rBC combined was 713 kg m −2 yr −1 , and for rBC alone, 342 kg m −2 yr −1 for rBC under certain assumptions. Compared to the melting rate measured using the mass and energy balance at 5360 m a.s.l. on Mera Glacier between November 2009 and October 2010, i.e. 3000 kg m −2 yr −1 and 3690 kg m −2 yr −1 respectively, the impact of rBC represents less than 16 % of annual potential melting while the contribution of dust and rBC combined to surface melting represents a maximum of 26 %. Over the 10-year period, rBC variability in the ice core signal primarily reflected variability of the monsoon signal rather than variations in the intensity of emissions.

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“…The chemical composition of aerosol in the Himalayas has been studied in detail by Shrestha et al (2000Shrestha et al ( , 2002, Carrico et al (2003) and Stone et al (2009). In particular, Shrestha et al (2000) conducted a 15 month long study of inorganic aerosol species at Phortse (4100 m a.m.s.l.…”

Section: P Shrestha Et Al: Pre-monsoon Aerosol Properties In Centramentioning

confidence: 99%

Chemical composition and aerosol size distribution of the middle mountain range in the Nepal Himalayas during the 2009 pre-monsoon season

2010

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Abstract. Aerosol particle number size distribution and chemical composition were measured at two low altitude sites, one urban and one relatively pristine valley, in Central Nepal during the 2009 pre-monsoon season (May-June). This is the first time that aerosol size distribution and chemical composition were measured simultaneously at lower elevations in the middle Himalayan region in Nepal. The aerosol size distribution was measured using a Scanning Mobility Particle Sizer (SMPS, 14-340 nm), and the chemical composition of the filter samples collected during the field campaign was analyzed in the laboratory. Teflon membrane filters were used for ion chromatography (IC) and watersoluble organic carbon and nitrogen analysis. Quartz fiber filters were used for organic carbon and elemental carbon analysis. Multi-lognormal fits to the measured aerosol size distribution indicated a consistent larger mode around 100 nm which is usually the oldest, most processed background aerosol. The smaller mode was located around 20 nm, which is indicative of fresh but not necessarily local aerosol. The diurnal cycle of the aerosol number concentration showed the presence of two peaks (early morning and evening), during the transitional periods of boundary layer growth and collapse. The increase in number concentration during the peak periods was observed for the entire size distribution. Although the possible contribution of local emissions in size ranges similar to the larger mode cannot be completely ruled out, another plausible explanation is the mixing of aged elevated aerosol in the residual layer during the morning period as suggested by previous studies. Similarly, the evening time concentration peaks when the boundary layer becomes shalCorrespondence to: A. P. Barros (barros@duke.edu) low concurrent with increase in local activity. A decrease in aerosol number concentration was observed during the nighttime with the development of cold (downslope) mountain winds that force the low level warmer air in the valley to rise. The mountain valley wind mechanisms induced by the topography along with the valley geometry appear to have a strong control in the diurnal cycle of the aerosol size distribution. During the sampling period, the chemical composition of PM 2.5 was dominated by organic matter at both sites. Organic carbon (OC) comprised the major fraction (64-68%) of the aerosol concentration followed by ionic species (24-26%, mainly SO 2− 4 and NH + 4 ). Elemental Carbon (EC) compromised 7-10% of the total composition and 27% of OC was found to be water soluble at both sites. The day-to-day variability observed in the time series of aerosol composition could be explained by the synoptic scale haze that extended to the sampling region from the Indian Gangetic Plain (IGP), and rainfall occurrence. In the presence of regional scale haze during dry periods, the mean volume aerosol concentration was found to increase and so did the aerosol mass concentrations.

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Aerosol and Precipitation Chemistry at a Remote Himalayan Site in Nepal

Cited by 76 publications

References 28 publications

Long Range Transport and Wet Deposition Fluxes of Major Chemical Species in Snow at Gulmarg in North Western Himalayas (India)

Long Range Transport and Wet Deposition Fluxes of Major Chemical Species in Snow at Gulmarg in North Western Himalayas (India)

A 10 year record of black carbon and dust from a Mera Peak ice core (Nepal): variability and potential impact on melting of Himalayan glaciers

Chemical composition and aerosol size distribution of the middle mountain range in the Nepal Himalayas during the 2009 pre-monsoon season

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