Chemical composition of snow-water and scavenging ratios over costal Antarctica

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

Influence of local sources on rainwater chemistry over Pune region, India

Rainwater samples were collected at five locations in the Pune region, an urban area in the south-west part of India, during 2006-2009. These locations; viz., Swargate (Traffic), Bhosari (Industrial), Pashan, Sangvi (Urban) and Sinhagad (Rural and High Altitude), represent different environments in this region. The study based on chemical analyses of these samples reveals that, on average, rainwater was alkaline at all the locations with pH values of 6.7, 6.16, 5.94, 6.04 and 5.92, respectively. Higher pH value of rainwater at the traffic location than those at the other locations is due mainly to the abundance of Ca 2- caused by vehicle-driven road-side dust. The maximum SO 4 2- and NO 3 - concentrations were found at Bhosari and Swargate respectively caused by local industrial and vehicular emissions. The average Fractional acidity over Pune area is 0.024, indicating about 98 acidity is neutralized by alkaline constituents. Factor analysis of the results indicated the influence of various sources, such as anthropogenic, soil dust, sea salt and biomass burning

Seasonal factors influencing in chemical composition of total suspended particles at pune, India

A study on the chemical characterization of boundary layer aerosols is made based on the collection of TSP and size separated aerosol mass samples at Pune during March 2007-February 2008. This study will be helpful in simulating atmospheric processes responsible for aerosol development over Pune region and understanding its environmental implications related to radiation budget and climate. It is found that major fraction of Ca2+ is locally generated by suspension of soil dust during all the seasons. During pre-monsoon season, coarse Mg2+ is originated from the soil and the sea salt, whereas fine Mg2+ is generated from the local biomass burning. Sizeable amount of SO4 2- is emitted from local industrial and brick kiln's activities. Neutralization of NO3 - , generated both from biogenic and anthropogenic sources, is made by NH3 gas generated mainly from anthropogenic sources.The data are further examined in terms of the factors specific to the individual seasons influencing physical and chemical characteristics of the boundary layer aerosols. The specific factors are: (a) Intense local convection during pre-monsoon season; (b) southwesterly wind flow and rainfall activity during monsoon season; and (c) Day time convection and occurrence of low level inversion during post-monsoon and winter seasons

Black carbon in cloud-water and rain water during monsoon season at a high altitude station in India

We present results of measurements of black carbon (BC) from ground-based wet-only rainwater (RW) and cloud-water (CW) sampling at a mountain field station, Sinhagad, situated in south western India during the period from June 2008 to October 2010. The amount of BC in the sample was determined by photometry at a wavelength of 528 nm after a procedure including the filtration through a 0.4 μm polycarbonate membrane filter. Water soluble concentrations of major anions in RW and CW were also determined. The average concentration of BC in RW (16 μmol dm−3) is higher by at least a factor 2 than that found in similar studies reported from other parts of the world. On the other hand, the average concentration of BC in CW (47 μmol dm−3) is lower by about a factor of 2 than that found at other sites. The ratio between the average concentrations in CW and RW varies from 2 (K+) to 7 (SO42−). The ratio for BC was about 3. No significant difference was observed for pH. Analysis of air mass back trajectories and of correlations between the various components indicates that long range transport of pollutants and dust from East Africa and Southern part of the Arabian peninsula might contribute to the high concentrations of BC and some of the ionic constituents at Sinhagad during the monsoon season

Chemistry of rainwater and aerosols over Bay of Bengal during CTCZ program

For the first time, simultaneous study on physical and chemical characteristics of PM 10, PM 2.5, and rainwater chemistry was attempted over the Bay of Bengal in monsoon season of 2009. The aerosols and rainwater samples were collected onboard ship 'SK-261, ORV Sagar Kanya' during Oceanographic Observations in the Northern Bay of Bengal under the Continental Tropical Convergence Zone (CTCZ) program conducted during 16 July to 19 Aug 2009. Aerosol samples collected by PM 10 and PM 2.5 were analyzed for various water soluble (Na +, K +, Ca 2+, Mg 2+, NH 4 + , Cl -, SO 4 2- and NO 3 - and acid soluble (Fe 2+, Al 3+, Zn 2+, Mn 3+ and Ni 2+) ionic constituents. The pH of rainwater varied from 5.10 to 7.04. Chloride ions contributed most to the total ion concentration in aerosol and rainwater, followed by Na +. Significant contributions of SO 4 2- , NO 3 - and NH 4 + found in PM 2.5, PM 10 and high concentrations of TSP and non sea-salt SO 4 2- over the mid-ocean is attributed to the long range transport of anthropogenic pollution from the Indian continent. The scavenging ratio was maximum for coarse particles such as Ca 2+ and minimum for fine particles like NH 4 +

Long term studies on characteristics of black carbon aerosols over a tropical urban station Pune, India

Continuous monitoring of surface black carbon (BC) was carried out using an Aethalometer in Pune, an inland urban tropical location in SW India. BC data for the period of 6years (2005-2010) was studied and compared with that reported from different Indian locations. The mean BC concentration for the 6year period was 3.58±1.55μg/m3 with maximum concentration occurring during winter and minimum during monsoon season in each year. Various characteristics of temporal variation of BC aerosols are discussed. Mean annual mass fraction of BC to TSP was 2.9. The similarity of diurnal variation as well as significantly good correlation of BC with PM1.0 showed that BC lies mainly in the fine size. Also, a good correlation with other anthropogenically originated chemical components of aerosol like NO3 -, NH4 + and nonsea salt fractions of SO4 2- and K+ indicated the presence of common source like fossil-fuel/biomass burning. Effects of meteorological parameters such as temperature, wind speed, rainfall and mixing ratio on BC are discussed. In addition, some of the optical properties of aerosols e.g. aerosol optical depths (AOD), single scattering albedo (SSA), and Angstrom Coefficient are correlated with surface BC concentrations

Source characterization for aerosol constituents and changing roles of calcium and ammonium aerosols in the neutralization of aerosol acidity at a semi-urban site in SW India

Atmospheric aerosols were collected at a semi-urban site in Pune city, located in the southwestern part of India, during the year 2007-08 covering different seasons. Anthropogenically derived particles (Non seasalt and non crustal fractions of SO4, Cl, K, Ca and Mg together with NO3, NH4, Cu, Zn and black carbon) contributed about 73 of the total measured TSP. Natural sources like sea (16) and soil (11) contributed about 27 to the total measured composition of TSP on annual basis. Surprisingly, Ca which is generally observed from crustal source, showed equal contribution from crustal and anthropogenic sources and was the major neutralizer of aerosol acidity in summer and monsoon seasons. NH4 was the most abundant component on annual average basis among the measured chemical components and also it was the leading neutralizer of aerosol acidity during post-monsoon and winter seasons. Aerosols showed alkaline nature (mean annual pH 6.51 and Neutralization Potential/Acidic Potential ratio 1.45) due to the neutralizing effect of Ca and NH4

Seasonal characteristics of black carbon aerosols over a high altitude station in Southwest India

Black carbon (BC) aerosol mass concentrations were measured using an Aethalometer at high altitude station Sinhagad, a rural location in south-west India, in the pre-monsoon and post-monsoon seasons during 2009-10. Mean BC concentration was about 67 less during pre-monsoon than that during post-monsoon. During post-monsoon, the surface boundary layer is generally shallow resulting in the trapping of pollutants in a lesser volume near the surface which lead to higher BC concentrations than of pre-monsoon which experiences high convective activity and thereby dispersion of aerosols near the surface. Diurnal variation of BC during pre-monsoon was attributed to the changes in the local boundary layer as well as to the certain anthropogenic activities near the sampling site. BC aerosol mass concentration showed good correlation with temperature gradient and relative humidity in pre-monsoon. However in post-monsoon, a weak correlation was observed with temperature gradient whereas with relative humidity, a good correlation was observed during night hours only. The wind speed and direction using NCEP/NCAR reanalysis data showed a possible transport from Pune city as well as from N/NE Indian regions during post-monsoon. BC also showed good correlation with other anthropogenic components of aerosols like NssSO 4, NssK, NO 3, and NH 4; indicating a possible common source for them