D. C. Parashar

Influence of crustal aerosols on wet deposition at urban and rural sites in India

Abstract The present study reports the pH and chemical composition of rain water at four urban sites of Delhi and one rural site away from Delhi. The collected samples were analysed for major cations (Ca, K, Mg , Na and NH4) and anions (SO4, NO3 and Cl). Data showed very high pH and Ca concentration at rural site which indicated the direct influence of crustal sources on rain water. It was estimated that a significant fraction of SO4 in rain water is contributed by crustal sources in this region. The association of high pH and high crustal SO4 suggested that crustal SO4 is not responsible for acidity or lowering the pH of rain water in India. Ion balance and conductivity balance for data quality assessment was observed to be within USEPA recommended limits.

Wet-only and bulk deposition studies at New Delhi (India)

Rain water samples were collected at New Delhi during the monsoon of 1994 at a height of 30 m above the ground level using a wet-only collector. Simultaneously, bulk samples from two different heights at 30 m and 13 m were collected. Frequency distribution of pH in wet-only samples revealed that rain was mostly alkaline Four out of 23 events were observed to be acidic where the ratio of (Ca+Mg+NH4)/(SO4+NO3) was very low. pH and ionic constituents were higher in bulk samples than in wet-only samples. On an average, the concentration in bulk samples at 30m height exceeded the wet-only samples by 13% while bulk samples collected at 13m height had 19% higher concentration than the bulk samples at 30m height and 32% higher than wet-only. The acidity of ram water was mainly contributed by sulphuric acid rather than nitric acid. At the height of 30 m, the acidity was primarily neutralized by NH4 while at 13 m height, it was buffered by Ca and Mg indicating the influence of dust particles.

Estimation of SO4 contribution by dry deposition of SO2 onto the dust particles in India

Dustfall deposition fluxes of major water-soluble components Cl, NO3, SO4, NH4, Na, K, Ca and Mg were estimated at five different sites of Delhi. The pH of water extracts of samples has been observed minimum at NPL ranging from 5.8 to 7.1 and maximum at Iqbalpur ranging from 7.9 to 8.7. The high values of pH of dustfall deposition suggest the dominance of crustal components that add higher alkalinity due to presence of components like Ca, Mg, etc. Dustfall fluxes were observed highest for Ca. considering the importance of alkaline nature of dust particles; the fraction of SO4 contributed by dry deposition of SO2 on the dust particles was estimated. Using these estimates, further the ambient concentrations of SO2 were calculated which were in a very good positive agreement with experimental concentration of SO2.

Precipitation and aerosol studies in India.

In India, rain water and atmospheric aerosols are observed to bealkaline in nature due to the influence of soil-derivedparticles which are rich in components like Ca and Mg. Thesecomponents increase the neutralization potential of rain waterand have a greater influence at rural site compared to urbansite. However, if there are continuous rains, the concentrationof crustal components becomes lower resulting in lower pH ofrain water. Unlike the characteristics of rain water oncontinent, the pH of rain water has been observed to be acidicin all the events over the Indian Ocean during Pre-campaigns ofIndian Ocean Experiment (INDOEX). The possible reason for acidicrains over Indian Ocean could be the anthropogenic contributionfrom continent transported by NE winds coming towards the oceanduring this period.

Anthropogenic emissions of NOX, NH3 and N2O in India

Emissions of NOx, NH3 and N2O from anthropogenic activities in India have been estimated based on actual field measurements as well as available default methodologies. The NOx emissions are mainly from the transport sector and contribute about 5% of the global NOx emission from fossil fuel. NH3 emissions from urea seems to be highly uncertain. However, emissions of NH3 from fertilizers and livestock are estimated to be 1175 Gg and 1433 Gg, respectively. N2O emissions seem to be derived predominantly from fertilizer applications, resulting in the release of 199–279 Gg N2O. Other sources of N2O, viz. agricultural residue burning, biomass burning for energy and nitric acid production are estimated to be 3, 35–187 and 2–7 Gg, respectively.

Emissions of SO 2 and NO x from biofuels in India

Concentrations of oxides of S and N in the atmosphere are strongly influenced by the emissions taking place from the burning of biofuels. This is particularly important in the developing countries where most of the energy requirement in the rural sector is met from biofuels. An experimental setup has been built to carry out controlled biomass burning and to derive emission factors for SO2 and NOx(NO and NO2) from various biofuels commonly used in India. Using these emission factors and the consumption data obtained from Tata Energy Research Institute’s (TERI) Energy Data Directory and Yearbook 1998–99, the budget of SO2 and NOx from biofuels used in India has been estimated as 0.4 ± 0.3 and 1.0 ± 0.4 Tg, respectively, for the year 1990.

A study on short-time sampling of individual rain events at New Delhi during monsoon, 1994

Rain water samples of equal volume (50 mL) were collected from two couvective showers at New Delhi on 28 July and 23 August during the monsoon, 1994. The variation of constituents of both the showers showed different trends which might have been due to different antecedent periods. The first shower occurred after an antecedent period of 2–3 hours while the second shower occurred after a 14 day interval. The first shower had acidic pH (<5.6) and relatively higher concentration of NH4, SO4, NO3, Cl, F and K indicating insignificant below cloud scavenging. The second shower had alkaline pH (>5.6) and relatively higher concentrations of Ca and Mg. The higher concentration of Ca and Mg in the second shower were due to the loading with particulate matter during the preceding 14 days which made below cloud scavenging significant.

Characterization of dry deposition associated with fire in plastic scrap market of west Delhi

Abstract Samples of dry deposition were collected at National Physical Laboratory during a fire incident occurred at Jwalapuri, a plastic scrap market located in west Delhi. About 2500 shops were gutted in this fire and almost 1 4 th of the city was affected by the plume. The collected samples were analyzed for Cl, NO3, SO4 and NH4. pH and Electrical Conductance of the samples were also measured. Data showed that deposition of Cl, SO4, NO3 was significantly higher than the normal conditions as reported earlier. It was estimated that respectively 21, 11, 16 and 0.2 tones of Cl, SO4, NO3 and NH4 were deposited by dry removal process during this fire incident.