P. S. P. Rao

Atmospheric pollutants and their influence on acidification of rain water at an industrial location on the West Coast OF India

The chemical analysis of rain water samples at 11 locations along with measurements of atmospheric aerosols and their size distributions were made to study the influence of pollutants on acidification of rain water during the monsoon season of 1990 at Chembur-Trombay area, a highly industrialized belt in Bombay region located on the west coast of India. The concentrations of acid precursor gases, namely, SO2 and NO, emanating from industries were low and their influence on acidification was limited to a few kilometer radius of their sources. Whereas, the deposition of ionic components (Na+, K+, Ca2+, Mg2+ and CI−) whose sources are natural (sea and soil) were uniformly distributed throughout the region as compared to those released from man-made sources. The high concentration of alkaline components, especially Ca2+ from natural sources and NH3 released from a fertilizer plant, were responsible for neutralising H+ ion concentration generated from the acidic components (SO42− and N03−). The variation from acidic (1970s) to alkaline (1990s) nature of rainwater in the area maybe due to the change in the use of fuel from coal to natural gas, which contains less sulphur and also, the pollution control measures taken by the industries.

Study of chemical composition of rainwater at an urban (Pune) and a rural (Sinhagad) location in India

[1]xa0Data are presented on the chemical composition of rainwater collected at a rural site (Sinhagad) near Pune, India, between August 2002 and August 2003 and at an urban site in Pune between April 2002 and August 2003. Both bulk water samples and wet-only samples were alkaline at both sites, with an average pH of 6.6 (both bulk and wet-only) at Pune and 6.4 (bulk) and 6.2 (wet-only) at Sinhagad. Only one case of acidic rain was recorded: at Sinhagad with pH of 5.2 (bulk) and 4.9 (wet-only). The major cations were Ca2+ and Na+, and the major anions were Cl− and SO42−. Higher concentrations of both SO42− and Cl− at Pune compared to Sinhagad were balanced by higher concentration of Ca2+ such that the pH remained approximately similar and, on average, well on the alkaline side. The difference in ionic composition between the two sites, available so far only for the monsoon period, is quite small (especially in case of wet only samples) and interpreted as an influence of local sources at the Pune site. At both sites the concentrations in the bulk samples were only slightly larger than those in the wet-only samples. Our analysis demonstrates that the Sinhagad site provides useful data representative of the regional situation. The data are also analyzed in terms of seasonal (monsoon versus postmonsoon) variations and air mass trajectories. Surprisingly high concentrations of SO42− at the rural site (Sinhagad) during the SW monsoon period may indicate transport from the African continent.

Seasonal variation of chemical composition and source apportionment of PM2.5 in Pune, India

Particulate matter with size less than or equal to 2.5xa0μm (PM2.5) samples were collected from an urban site Pune, India, during April 2015 to April 2016. The samples were analyzed for various chemical constituents, including water soluble inorganic ions, organic carbon (OC), and elemental carbon (EC). The yearly mean total mass concentration of PM2.5 at Pune was 37.3xa0μg/m3, which is almost four times higher than the annual WHO standard (10xa0μg/m3), and almost equal to that recommended by the Central Pollution Control Board, India (40xa0μg/m3). Measured (OC, EC) and estimated organic matter (OM) were the dominant component (56xa0±xa011%) in the total particulate matter which play major role in the regional atmospheric chemistry. Total measured inorganic components formed about 35% of PM2.5. Major chemical contributors to PM2.5 mass were OC (30%), SO42− (13%), and Cl− and EC (9% each). The high ratios of OC/EC demonstrated the existence of secondary organic carbon. The air mass origin and correlations between the various components indicate that long range transport of pollutants from Indo-Gangetic Plain (IGP) and Southern part of the Arabian Peninsula might have contributed to the high aerosol mass during the dry and winter seasons. To our knowledge, this is the first systematic study that comprehensively explores the chemical characterization and source apportionment of PM2.5 aerosol speciation in Pune by applying multiple approaches based on a seasonal perspective. This study is broadly applicable to understanding the differences in anthropogenic and natural sources in the urban environment of particle air pollution over this region.

Impact of anthropogenic activity and cyclonic storm on black carbon during winter at a tropical urban city, Pune

AbstractnBlack carbon (BC) aerosols are emitted into the atmosphere as a byproduct of different combustion processes and are reported to be a very strong absorber of solar radiation. In this paper, we present results on BC aerosols over Pune, a tropical urban city in south west India during Diwali festival in the month of November 2010. Daily mean BC showed about 5xa0% increase on Diwali day compared with preceding and succeeding period with concentrations reaching as high as about 21xa0μg/m3 in the morning on Diwali day, mainly due to the influence of extensive fireworks. However, the strong winds accompanied by occasional rainfall due to severe cyclonic storm “Jal” formed in the Bay of Bengal on the same day dampened this effect and reduced BC to about 2xa0μg/m3 within 6xa0h. There was only 5xa0% increase in mean BC concentration on Diwali day during 2010 as compared to the average increase of about 17xa0% during preceding 4xa0years on Diwali day, mainly due to the impact of weather conditions induced by Jal.

Size distribution and chemical composition of summer aerosols over Southern Ocean and the Antarctic region

The size distribution of atmospheric aerosols together with their composition, sources and sinks, is a key element in understanding aerosol effects on the Earth’s climate. Aerosol particle size distribution and chemical composition were measured over the Southern Ocean and at Antarctic region during December 2009–March 2010. Aerosol samples were collected using multi-stage low volume Air Sampler, and an aerosol size spectrometer was employed to monitor PM mass concentration continuously. The mean mass concentrations for PM10, PM2.5 and PM1 were 1.5, 1.0 and 0.6xa0μg/m3, respectively at the Bharati station and were almost 2.5 times higher at the Maitri station. The mass size distribution of the aerosols measured by using a low volume air sampler exhibited a bimodal feature with a peak each in the size range of 0.4 to 0.7xa0μm and 3 to 5xa0μm. The difference in concentrations between the two locations for fine particles was comparatively lower than that for simultaneously measured coarse particles. Aerosol samples were analyzed for various water-soluble ionic constituents e.g. Na+, K+, Ca2+, Mg2+, NH4+, Cl−, SO42− and NO3−. Sea-salt aerosols contributed to 86% of the measured mass over the Southern Ocean, 80% over Bharati and 76% at Maitri. The Southern Ocean being the most significant source of the particles during summer time, controls the aerosols at Bharati and Maitri sites. The present study will be helpful in simulating atmospheric processes responsible for aerosol characterization over coastal Antarctica and understanding its environmental implications related to radiation budget and climate over this region.