Umesh Chandra Kulshrestha

Chemical characteristics of rainwater at an urban site of south-central India

Abstract The pH variation and the chemical characteristics of rainwater have been studied during monsoons from 1999 to 2001 at Hyderabad, a city in south-central India. The pH varied from 5.5 to 7.2 with an average of 6.4 which is in alkaline range considering 5.6 as the neutral pH of cloud water with atmospheric CO 2 equilibrium. Out of 28 rain events, only two events were observed in acidic range ( 2+ >Cl − >SO 4 2+ >NH 4 + >Na + >HCO 3 − >NO 3 − >K + >Mg 2+ . The ratios of different components with respect to seawater ratios were observed to be higher, indicating the significant influence of non-marine sources at this site.

Characterization of precipitation at Agra

In the present study, the precipitation at Agra city was studied during July–September, 1991. Thirty two samples were collected at Dayalbagh which is a suburban area in the NW of the city with no major industrial activities and minimum traffic density. The study comprised the determination of F, Cl, NO3, SO4, Na, K, Ca, Mg, NH4, Fe, Cu, Zn, and SiO2 in the wet-only samples. On the basis of the neutralizing factors and correlations, it has been determined that in our region, acid neutralization is brought about by calcium rather than the ammonium ion. The Ca/K and Ca/Mg ratios indicated that only 10 percentile of the values in the rainwater samples correspond to local soil and the rest could be attributed to transported soil. The data were also subjected to factor analysis based on principal component analysis, using the SPSS software. The rotated factor matrix grouped the variables into four factors. The first factor includes Cu, Zn, Fe and Na which may be attributed to industrial activities and scavenging processes. Factor 2 clusters Ca, HCO3, NO3, SO4, Cl and Mg together, all of which are soil-derived species. Factor 3 groups K and NH4 which may be attributed to biogenic combustion emissions. Factor 4 includes F and SiO2 which are probably because of their emission in the process of lime pulverization.

Investigation into atmospheric deposition through precipitation studies at New Delhi (India)

Abstract Rain water samples were collected during the monsoon of 1994, using automatic wet-only and manual bulk collectors at a height of 30 m above the ground at the National Physical Laboratory, New Delhi. The average pH of the rain water was 5.7 and its chemical composition was dominated by NH 4 and SO 4 . The free acidity of the rain water was found to be due to S04 rather than N03 and it was mainly neutralized by NH 4 and Ca. Calculation of sea salt fraction and enrichment factor revealed that this site is free for marine influence. On an average the bulk samples had 13% higher concentration than that of wet-only samples which may be due to the deposition of soil-derived particles during the 24 h period of exposure. The higher neutralization factors of Ca and Mg in bulk samples and highest dry deposition rates for Ca in comparison to other components, indicated the positive interference of dust particles in neutralization.

Chemical Composition and Association of Size-Differentiated Aerosols at a Suburban Site in a Semi-Arid Tract of India

Size-differentiated concentrations of SPM, F, Cl, NO3, SO4, Na, K, Ca, Mg and NH4 in atmospheric aerosols were measured in a suburban area of Agra city during December 1992 to March 1993. Except for NH4, Cl and Na, all components were found to have a bimodal distribution. The fine fraction was dominated by NH4, K, NO3 and SO4, while Na, Ca, Mg, F and Cl contributed to the coarse fraction. Fifty-eight percent of SO4 and 67% of NO3 were found in the fine mode and the coarse mode comprised 42 and 33% of SO4 and NO3, respectively. SO4 was found to have a peak above the submicron range at 1.1 µm which has been attributed to secondary sulphate formation by heterogeneous oxidation of SO2 on alkaline particles of Ca and Mg. The total aerosol was basic in nature and dominated by the soil-derived acid neutralising components (Ca, Mg and Na).

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.

Greenhouse Gas Inventory

The “greenhouse effect” is the warming of the Earth due to the presence of GHGs. The name “green house” is borrowed from phenomenon used in greenhouses to raise temperature capturing long wave radiation within the green house. Solar radiation from the sun absorbed by the surface of the Earth and then radiated back to the atmosphere in the form of long wave infrared radiation.

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.

Factors affecting alkaline nature of rain water in Agra (India).

Rain water was collected and analysed from a reference site, Dayalbagh and Taj Ganj, near the Taj Mahal in Agra. The ionic components Ca, Mg, Na, K, NH(4), Pb, Fe, Zn, SO(4), HCO(3), Cl and F were analysed along with pH, alkalinity and conductance. The average pH of rain water at both sites is 7.05. There is a dominance of alkaline components, particularly Ca. The rain water chemistry shows the importance of calcareous soil-derived materials in controlling the pH of rain water.