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Science | 2009

Brown Clouds over South Asia: Biomass or Fossil Fuel Combustion?

Örjan Gustafsson; Martin Kruså; Zdenek Zencak; Rebecca J. Sheesley; Lennart Granat; Erik Engström; P. S. Praveen; P.S.P. Rao; Henning Rodhe

Carbonaceous aerosols cause strong atmospheric heating and large surface cooling that is as important to South Asian climate forcing as greenhouse gases, yet the aerosol sources are poorly understood. Emission inventory models suggest that biofuel burning accounts for 50 to 90% of emissions, whereas the elemental composition of ambient aerosols points to fossil fuel combustion. We used radiocarbon measurements of winter monsoon aerosols from western India and the Indian Ocean to determine that biomass combustion produced two-thirds of the bulk carbonaceous aerosols, as well as one-half and two-thirds of two black carbon subfractions, respectively. These constraints show that both biomass combustion (such as residential cooking and agricultural burning) and fossil fuel combustion should be targeted to mitigate climate effects and improve air quality.


Atmospheric Environment | 1989

Spread of acid rain over India

L. T. Khemani; G.A. Momin; P.S.P. Rao; P.D. Safai; G. Singh; R.K. Kapoor

Abstract Rain water and aerosol samples were collected at a few locations representative of urban and non-urban regions in India. Also, rain water samples were collected in and around a coal-fired power plant. All the rain water and aerosol samples were analyzed for major chemical components along with pH. The rain water at all the places of measurement, except near the industrial sources, has been found to be alkaline and was characterized by the presence of excess cations, particularly by Ca2+. The acid rain near the industrial sources was associated with excess anions, especially SO42−. The atmospheric aerosols at all the places of measurement were found rich with basic components, suggesting that the alkaline soil dust and fly ash are responsible at present for preventing the spread of acid rain in India.


Atmospheric Environment | 1987

Influence of alkaline particulates on pH of cloud and rain water in India

L. T. Khemani; G.A. Momin; Medha S. Naik; P.S.P. Rao; P.D. Safai; A.S.R Murty

Abstract Cloud and rain water samples were collected on board aircraft by specially designed equipment, during three monsoon seasons, 1983, 1984 and 1985 in the Pune region in India. The samples were analyzed for major ionic components and pH, and the concentrations of all the ionic components were found to be significantly higher (35–161%) in cloud water than in rain water. In cloud water Cl contributed most (35%) to the total ionic concentration followed by Ca(21%) and Na(17%). Sulphate and nitrate concentrations, on the average, were low and were found to account for only 6% of the total ionic concentration. pH of cloud water and rain water was substantially higher than that of the CO2-equilibrated value (5.6). The findings suggest that influence of anthropogenic sources is negligible and that of soil dust which is alkaline is substantial on the pH and chemistry of cloud/rain water in India.


Water Air and Soil Pollution | 1985

Impact of alkaline particulates on pH of rain water in India

L. T. Khemani; G.A. Momin; Medha S. Naik; P.S.P. Rao; R. Kumar; Bh. V. Ramana Murty

Rain water samples were collected over a period of a decade from 1974 in Pune, a city which is relatively free from industrial pollution. They were also collected at 4 places during 1974 in the region of Bombay which is highly industrialized. The samples were analyzed for major chemical components and pH. The ionic balance was computed. Samples were collected at Delhi during 1965 and 1966 and were analyzed for pH. The values were compared with those reported for 1978. The total suspended particulates (TSP) were measured at Delhi during 1980 and analyzed for water soluble components. The rain water at all the places except near the industrial source was not acidic and was characterized by the presence of excess cations, particularly Ca. The acid rain near the industrial source was associated with excess anions, especially sulphate. The difference between the cations and anions was inversely proportional to the H+ ion concentration. The pH of rain water at Delhi which was in the alkaline range during 1965 and 1966 remained alkaline even after a period of 12 yr when the city developed industrially. The TSP in the region was rich with the basic components, mainly Ca, suggesting that the alkaline property of the soil dust is mainly responsible for neutralizing the acidic effects resulting from the anthropogenic gaseous pollutants.


Atmospheric Environment | 1995

Study of surface ozone behaviour at urban and forested sites in India

L. T. Khemani; G.A. Momin; P.S.P. Rao; R. Vijayakumar; P.D. Safai

Abstract Surface ozone concentrations were measured continuously at Pune for a period of one year during 1991–1992 and for a period of 10 days in January 1992 at Upper Kargudi and in April 1992 at Bandipur, core zones of the Nilgiri Biosphere Reserve forests located in Tamil Nadu and Karnataka States, respectively, in south India. There is a marked diurnal variation in the concentration of surface ozone which clearly follows the diurnal variation of surface temperature. The monthly maximum concentration was observed during the summer season (March–May) and minimum during the monsoon season (June–September). The annual average concentration of ozone was 27 ppb and hourly values varied between 2 and 69 ppb at Pune. However, in the forest environment the 10-day average concentration was 15 ppb and hourly values varied between 5 and 31 ppb. The values of surface ozone at Pune and forest environment are below the U.S. EPA standard (113 ppb, maximum 1 h permissible concentration).


Atmospheric Environment | 1995

Rain water and throughfall chemistry in the silent valley forest in South India

P.S.P. Rao; G.A. Momin; P. D. Safai; A.G. Pillai; L. T. Khemani

Rain water and throughfall samples were collected at the Silent Valley forest during the two consecutive southwest summer monsoon seasons (June-September) of 1989 and 1990. All the samples were analysed for Cl - , SO 4 2- , NO 3 - , NH 4 + , Na + , K + , Ca 2+ , Mg 2+ and pH. The average pH of rain water was 5.31 and that of throughfall was 6.38 indicating that the throughfall is 10 times more alkaline than the rain water. The buffering of H + in throughfall was due to interaction with canopy. It was found that the ionic concentrations in throughfall were higher than those in rain water, except for NH 4 + . Enrichment of ionic components in throughfall is attributed to the interaction of precipitation with the forest canopy.


Atmospheric Environment. Part B. Urban Atmosphere | 1992

Measurements of wet and dry deposition at an urban location in India

P.S.P. Rao; L.T. Khemani; G.A. Momin; P.D. Safai; A.G. Pillai

Abstract Wet and dry depositions were collected in Pune city using 24-h and weekly sampling periods, respectively, from January 1984 to December 1988. All the wet and dry deposition samples were analysed for major cations and anions along with pH. Dry depositions were minimum in the monsoon season and maximum in the winter season though there was no significant difference in pH values. The wet deposition of all ionic components was found to be higher than the dry deposition. The depositions of the ionic components from natural sources (soil and sea) were higher than those from anthropogenic sources. The dry deposition velocities of the aerosols were found to be increasing with increase of their mass median diameters. The chemical composition of the dry deposition at Pune indicated maximum depositions of the alkaline substances, which are the main cause for the alkaline pH of rain water. Results of the present study have suggested that the atmospheric composition in the city is strongly influenced by natural sources rather than anthropogenic.


Atmospheric Environment | 1989

Long-term effects of pollutants on pH of rain water in North India

L. T. Khemani; G.A. Momin; P.S.P. Rao; P. D. Safai; G. Singh; R. N. Chatterjee; Prem Prakash

Abstract The ionic composition and pH of rainwater samples collected during the summer monsoon seasons of 1963 and 1965 at Agra and Delhi, respectively have been compared with those collected during the summer monsoon seasons of 1984 at both these cities. The pH values at Agra and Delhi have been found to have decreased by 2.8 (9.1-6.3) and 0.9 (7.0-6.1) units, respectively after the period of two decades during which the cities developed industrially to a great extent. The main cause for the decrease in the pH values is a significant increase of acidic components and decrease of soil-oriented components in the rain water. For the first time in India, long-term effects of pollutants on the pH of rain water have been observed but the effects are comparatively slow compared with those in western countries.


Water Air and Soil Pollution | 2001

Studies of Wet Deposition and Dustfall at Pune, India

A.G. Pillai; Medha S. Naik; G.A. Momin; P.S.P. Rao; P.D. Safai; Kaushar Ali; Henning Rodhe; Lennart Granat

Rain water and dustfall deposition samples were collected at Pune, an urban site (1992–98) and at Sinhagad, a rural site (1992–94). The samples were collected with wet-only and bulk collectors at Pune and with bulk collector at Sinhagad. The samples were analyzed for major ions, pH and conductivity. The study showed that the rain water at both places is alkaline (pH > 5.6). The average pH at Pune was 6.1. Neutralising components, indicated by Ca and non sea salt (nss) Mg have higher concentrations than the acidifying components SO4 and NO3. The wet deposition fluxes of all the ionic components were higher than the dustfall fluxes. Relative contribution from dustfall was largest for K, Ca, Mg and NO3. Dustfall was greater at Pune, compared to Sinhagad for all components and up to double for Ca.


Atmospheric Environment | 1985

Trace elements and sea salt aerosols over the sea areas around the Indian sub-continent

L. T. Khemani; G.A. Momin; Medha S. Naik; P.S.P. Rao; R. Kumar; Bh. V. Ramana Murty

Abstract The nature and the characteristics of trace elements and sea salt aerosols in the ocean atmosphere around the Indian sub-continent was studied. For this purpose, concentrations of the total suspended particulates (TSP) as well as of its various chemical components together with their mass size distributions were measured on 11 days in May 1983. Over the sea regions around the sub-continent, sampling was done on board the research Vessel Gaveshani using a high volume air sampler and a multistage Andersen sampler. The concentrations of soil-origin elements (Al, Fe, Mn and Ca) were found to be at a maximum over the Arabian sea region suggesting the presence of dust particulates, transported from the Arabian peninsula. The near sea water ratio of CI/ Na was observed in giant size (> 2.5 μm dia) sea salt aerosols suggested that there was very little fractionation in these aerosols. The ratio value considerably decreased in the case of sub-μm sea salt particles. The chemical components originating from soil and from sea salt showed a unimodal distribution whereas those from anthropogenic sources showed a bimodal distribution.

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G.A. Momin

Indian Institute of Tropical Meteorology

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P. D. Safai

Indian Institute of Tropical Meteorology

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Kaushar Ali

Indian Institute of Tropical Meteorology

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P.D. Safai

Indian Institute of Tropical Meteorology

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L. T. Khemani

Indian Institute of Tropical Meteorology

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D. M. Chate

Indian Institute of Tropical Meteorology

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Krishnakant Budhavant

Indian Institute of Tropical Meteorology

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Medha S. Naik

Indian Institute of Tropical Meteorology

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S. Tiwari

Indian Institute of Tropical Meteorology

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A.G. Pillai

Indian Institute of Tropical Meteorology

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