Chemical Composition of Snow-Water and Scavenging Ratios over Costal Antarctica

Krishnakant Babanrao Budhavant,Pramod Digambar Safai,Pasumarthi Surya Prakasa Rao

doi:10.4209/aaqr.2013.03.0104

Krishnakant Babanrao Budhavant, Pramod Digambar Safai + Show 1 more

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https://doi.org/10.4209/aaqr.2013.03.0104

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Abstract

Snow samples and aerosol samples were collected at coastal Antarctica near Larsemann Hills and Maitri, during the 29th Indian Antarctic Expedition carried out during Dec., 2009 to March 2010. The main objective of this study was to characterize the chemical composition of fresh and surface snow at coastal Antarctica and to determine the scavenging ratios using composition of snow and aerosol samples. The pH of surface and fresh snow were 6.03 and 5.64 respectively. The surface snow samples were collected along a 127-km transect from the seaward edge of the ice shelf to the Antarctic plateau and analyzed for the presence of the major inorganic components SO4 2-, NO3 -, Cl-, NH4 +, Na+, K+, Ca2+ and Mg2+. It was observed that Na+ and Cl- were the most abundantly occurring ions at Antarctica. Considerable amount of SO4 2- was also found in the both fresh and surface snow which may be attributed to the long range transport from Northern Hemisphere as well as to the oxidation of DMS produced by marine phytoplankton. A higher percentage of the ions in fresh snow may be because of trapping of the particulate matter in it. The sea-salt components i.e., Na+, Cl- and Mg2+ decreased with increasing distance from the coast. The acidic components were neutralized mainly by NH4 + and Ca2 +. The scavenging ratio was maximum for Na+ and minimum for NO3 -, indicating that the scavenging efficiency was higher for coarse size particles and lower for fine size particles. In addition, we have attempted to find out the possible sources of the observed chemical species in snow-water.

Highlights

As one of Earth’s most dynamically changing surface material, the structure of the snow changes in response to diurnal and seasonal changes in temperature
Considerable amount of SO42– was found in the both fresh and surface snow which may be attributed to the long range transport from Northern Hemisphere as well as to the oxidation of dimethyl sulphide (DMS) produced by marine phytoplankton
The scavenging ratio was maximum for Na+ and minimum for NO3, indicating that the scavenging efficiency was higher for coarse size particles and lower for fine size particles

Summary

Introduction

As one of Earth’s most dynamically changing surface material, the structure of the snow changes in response to diurnal and seasonal changes in temperature. The snow pack can contain records that include climate change proxies, aerosol contaminant deposition rates and physical or photochemical alterations. Antarctica has a unique climate, which is the result of high altitude, perpetual snow cover, and great height of the ice plateau above the mean sea level and the vast extent of its surrounding ocean. The Antarctica provides the cleanest atmospheric environment available for study of the chemicals stored in snow and accumulated on the polar ice sheet, the atmosphere of the Polar Regions is already affected by human activities (Legrand and Mayewski, 1997). Snow studies over sites such as Antarctica will help in estimating the backgroundlevel snow and aerosol, which could be compared with

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