Medha S. Naik

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

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.

Impact of alkaline particulates on pH of rain water in India

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.

Studies of Wet Deposition and Dustfall at Pune, India

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.

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

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.

Trace elements in the atmospheric aerosols at Delhi, North India

The total suspended particulate (TSP) levels at Delhi (north India) were measured on 116 days between February and October 1980. The observations were stratified according to season and the values of cross-correlation of the TSP and its components were evaluated. High TSP (209 μg m-3) levels were found during the summer period associated with hot and dry weather in the region and low TSP (109 μg m-3) were found during the monsoon period. Most of the TSP mass was associated with natural soil elements, such as Fe, Al, Mn, Ca, and K. Only a fraction of the mass of the TSP was comprised of elements from anthropogenic sources, e.g., Pb, Ni, Cd, Sb, Cu, and Zn. The aerosols at Delhi were potentially basic in nature, unlike those in European countries which are acidic in nature and cause acid rainfall.

Observations of Aitken nuclei and trace gases in different environments in India

Surface measurements of Aitken nuclei have been made at a few representative environments in India. The periods of measurements have ranged from a few days to a few years depending upon the place of measurement. Aircraft measurements of Aitken nuclei were made at one of the locations during three successive monsoon periods. During part of the time simultaneous measurements were made of the trace gases SO2, NH3, NO2, and O3. The study presents the seasonal and diurnal variation of Aitken nuclei in the different environments and their association with the trace gas concentrations.

Precipitation chemistry at Sinhagad : a hill station in India

The chemistry of precipitation in remote sites such as mountain tops is of interest in the study of atmospheric pollution and acid rain. The chemical composition measured at mountain site which is away from industrial and urban areas is useful as a reference level and it allows to determine the extent of anthropogenic contamination. Hence, rain water samples were collected at Sinhagad (18°21′N, 73°45′E, 1450 m asl during the monsoon season (June-September) of 1992 and were analysed for major ions. The precipitation samples collected at Sinhagad were alkaline in nature and pH values ranged between 5.9 to 6.76. The ionic composition was dominated by soil dust The concentration of Ca2+ was highest among all the ions. The concentrations of excess SO32− and NO4− were small (23.8 and 15.2 μeq l−1 respectively) compared to the values of polluted regions in India. The correlation coefficient between the ions and pH values was calculated and it was found to be maximum in case of Ca2+. Precipitation samples collected at Sinhagad were alkaline owing to higher concentration of Ca2+ and lower levels of acidic pollutants (SO42− and NO3−).

Origin of calcium in marine aerosol over the arabian sea near the west Coast of India

Abstract We report the influence of soil dust on marine aerosols inferred from the analysis of aerosol samples collected on board research vessel ‘Gaveshani’ for a period of 11 days during May 1983 over the sea areas around the Indian subcontinent. The number distribution curve over the Arabian Sea was disturbed due to the presence of soil particles in the large size aerosols ( r ⩾ 1 μm) as compared to that over the Bay of Bengal. The atmospheric concentration of non sea-salt calcium was positively correlated with the concentration of Fe. The Ca/Na ratios varied widely from the Arabian Sea to the Bay of Bengal with respect to ratio in sea-water. All the excess calcium in the marine aerosols is found to originate from the soil particles of the Arabian Desert and is transported towards the west coast of India.

A study of the gaseous and particulate pollutants in the environment of a thermal power plant project area

Observations on gaseous and particulate pollutants were undertaken at four locations in the region of a thermal power plant (TPP), which is under construction at Tuticorin, south India. The predicted concentrations Of SO2 due to the emissions from the TPP and its possible impact on the inhabitants and climate in the downwind region were evaluated. Also, the predicted concentrations downwind of a Petrochemical Industrial Complex (PIC) located in the vicinity of the TPP were computed and compared with the measured concentrations.The predicted maximum concentration of SO2 at 6 km downwind of TPP is about 530 μg m−3 under most favourable wind conditions. The anticipated increase in SO2 due to the thermal power plant under construction may therefore be substantial.The predicted concentrations Of SO2, at a distance of 1.8 km downwind of the PIC, varied between 34 and 216 μg m−3 for wind directions ranging from 70 to 90° and for Pasquill stability category C. The plume would be over the observational site when the wind direction is 80°. The maximum measured concentration was 23 ug m−3. The discrepancy was due to the rapid fluctuations in the wind direction during the observational period over a wide range from 20 to 90°.

Dispersion of sulphur dioxide around the thermal power plant at Ahmedabad, India

Abstract Air quality due to the release of sulphur dioxide from the thermal power plant within the city limits of Ahmedabad has been computed employing a point, area and line dispersion model. To estimate probable air quality, the meteorological data for 3 consecutive days in the middle of each month of 1983 is used. The concentration of sulphur dioxide is computed at a distance of every 500 m in 16 directions up to the city limit. The air quality in the worst case is estimated in downwind distances under unfavourable meteorological conditions. The probable zones of high concentrations of sulphur dioxide over residential, commercial and industrial areas of the city are below the ambient air quality standards set by the U.S. EPA in 1971 almost throughout the year. However, in the months of April and October the zone of high concentration (500 μg m −3 ) exceeds the EPA standard. Also, under the most unfavourable meteorological conditions, the estimated high ground-level concentration of sulphur dioxide can reach up to 1000 μg m −3 at a distance of 1.25 km from the thermal power plant. This may be attributed to the effect of fumigation.