K.M. Kumari

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.

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).

Measurements of major ion concentration in settled coarse particles and aerosols at a semiarid rural site in India

Deposition rates and deposition velocities of water-soluble ions (F, Cl, NO3, SO4, NH4, Ca, Mg, Na and K) were measured at a rural site (Gopalpura, Agra). Dry deposition samples were collected throughout the year from December 1995 to August 1997, while the aerosol samples were collected only during the winter season of 1996. Surrogate technique was used to collect the dry deposition samples, while aerosol samples were collected on PTFE membrane filter. Deposition velocities (Vd) of SO4 and NO3 are < or = 0.01 m s(-1) while Ca, Mg, Na, K, NH4, F and Cl exhibit greater than 0.01 m s(-1) Equivalent concentration ratios of K/Na, Ca/Na and Mg/Na conform with the corresponding ratios of local soil, indicating the dominant contribution of local sources. Deposition rates are maximum in winter, followed by summer and monsoon. No significant differences are found in dry deposition rates of all ions or in atmospheric concentrations of soil-derived elements with respect to wind direction. However, in aerosols, concentrations of F, Cl, NO3 and SO4 are higher with winds from southwesterly and westerly directions corresponding to pollution sources located in these directions. Deposition data have been used to calculate the critical load of S and N for soil with respect to Triticum vulgaris. The critical load of actual acidity was found to be 622.4 eq ha(-1) year(-1) within the range of 500-1,000 eq ha(-1) year(-1) as assessed by the RAINS-Asia model for this region. The present load of S and N (77.4 and 86.4 eq ha(-1) year(-1)) was much lower than the critical load of S and N (622.4 and 2,000 eq ha(-1) year(-1)), indicating that at present there is no harmful effect on ecosystem structure and function.

Measurements of formic and acetic acid levels in the vapour phase at Dayalbagh, Agra, India

Abstract Acetic and formic acid concentrations were determined in the vapour phase at ground level at Dayalbagh, Agra, during the winter and summer of 1992–1993. Ion chromatography was used to measure the species. Yearly means were 1.7±1.6 ppbv for acetic acid and 1.3±1.4 ppbv for formic acid ( N = 137). Average winter mixing ratios ( N = 60) for acetic acid and formic acid were 1.8±1.6 and 1.4±1.4 ppbv, respectively, and the corresponding summer levels ( N = 77) were 1.3±1.2 and 1.1±1.2 ppbv but seasonal variation was not statistically significant. These concentrations are within the range reported at other sites worldwide. The F A (formate-to-acetate) ratio showed a diurnal variation with higher averages in the day (1.2) than at night (0.45). With respect to wind direction, the W sector appears to be the cleanest and is associated with the lowest mean concentrations of acetic and formic acids; local sources as well as the ones on a larger scale appear to contribute to the levels recorded in this study.

Dry deposition of sulphate and nitrate to polypropylene surfaces in a semi-arid area of India

Abstract Dry deposition rates of the major ionic species Cl − , NO 3 − , SO 4 2− , Na + , K + , Ca 2+ and Mg 2+ were estimated by the surrogate collection technique using polypropylene surfaces. The dry deposition rates of the soil derived cations Ca 2+ , Na + , K + and Mg 2+ were of the order of 0.4–6.1 mg m −2 d −1 . The dry deposition rates of the acidic ions NO 3 − and SO 4 2− were of similar magnitude, suggesting that they are also soil derived or associated with the soil elements. On a seasonal basis, deposition rates were maximum during the winter followed by summer and minimum during the monsoon.

Identification of the nature and source of atmospheric aerosols near the Taj Mahal (India).

The chemical composition of aerosol samples collected at Agra near the Taj Mahal during April 1991-June 1992 was identified by wet chemical analysis. The average concentration of suspended particulate matter (SPM) was 368.5 µg m−3, ranging between 83 and 1305 µg m−3, depending upon the season. Elevated levels of Na, SO4, Mg, NO3 and Cl compared to levels reported worldwide were attributed to the suspension of soil particles, as well as industrial emissions. Geometric mean enrichment factors of elements indicated two groups; one having enrichment factors less than 7 which were comprised of Na, K, Ca, Mg, Fe, Al, Mn and Si (crustal) and the other having enrichment factors greater than 13 and which were comprised of Ni, Cu, Zn, Pb, and Cd (non-crustal). Principal component analysis revealed the association of the first principal component with soil-derived elements while the second, third and fourth principal components were associated with industrial processes, wood combustion and brick kilns respectively. The study indicates that near the Taj Mahal the dominance of natural sources may enhance the degree of deterioration of the marble surface if micro-climatological conditions favour its wetting.

Formate and acetate in monsoon rainwater of Agra, India

Formate and acetate concentrations were estimated using ion chromatography in 19 precipitation samples collected on an eventwise basis during the monsoon season (July through September), 1991, at Dayalbagh, Agra. Volume-weighted average (VWA) concentrations for formate and acetate were 5.8 and 6.55 μmol L−1, respectively. The VWA hydrogen ion concentration was 0.084 μeq L−1 (pH 7.07) and the correlation coefficient between the two ions was 0.85. The average formate to acetate ratio was low (0.88), possibly due to an increase in acetate contribution from direct emissions associated with heavy vehicular traffic load and/or indirect acetate formation by alkaline hydrolysis of PAN. Widespread local use of biomass as a domestic fuel may also contribute acetate. In 4 of the 19 precipitation events studied, higher values of both species were recorded. Contributions from soil in addition to vegetation, were suspected in these samples. Inputs from soil and combustion activities were supported by correlations among formate, acetate and Ca2+ (terrigenous species), K+, SO42− and NO31−.

Dry deposition of nitrate and sulphate on surrogate surfaces

Airborne velocities and deposition fluxes (DF) of NO3−1 and SO4−2 on various surrogate surfaces, specifically petridishes of polypropylene and glass, marble slabs, ceramic tiles, and stainless steel plates, were measured between January and June, 1991. DFs were higher in the summer months, but varied with the surface, decreasing in the order above. In the summer, NO3−1 DFs were higher than corresponding SO4−2 values. In the winter, this trend was reversed. Deposition velocities of both species were of the order of 10−3cm s−1.

Effect of anthropogenic activity on formate and acetate levels in precipitation at four sites in Agra, India

Abstract Twenty-four-hour precipitation samples from four sites: Dayalbagh (DB), Hari Parvat (HP), Taj Mahal (TM) and Udyog Kendra (UK) in Agra city, during the monsoon season (July–September) of 1991, were analysed for formate and acetate. Each site was representative of a different level of anthropogenic activity. The formate/acetate ratio observed appeared to be characteristic of the dominant activity at the site; the geometric means of the formate/acetate ratios calculated for individual samples were 0.99, 0.17, 0.83 and 0.21 for DB, HP, TM and UK, respectively. These corresponded to the level of pollution at the site. Direct acetate inputs from extensive combustion and automobile exhaust could contribute to elevated levels of the species at two of the four sites. Another possible indirect input could be from the alkaline hydrolysis of PAN, aided by relatively high pH values of rain water (volume-weighted averages = 6.79, 6.69, 7.22, 7.15) at the four sites.

Formate and acetate levels compared in monsoon and winter rainwater at Dayalbagh, Agra (India)

A total of 59 rainwater samples were collected during the winter and monsoon (1991–92) at Dayalbagh, Agra. This site is relatively free from the influence of anthropogenic emissions and the volume-weighted average concentrations (VWA) of formate in the winter and monsoon were 22.5±6, 16.1±3 while acetate VWAs were 17.1±5 and 13.8±3 μmol l-1, respectively. Although the VWAs varied between seasons, it was not statistically different. Total deposition (in mmol m-2) varied between season (winter formate, 1.4; acetate, 1.1; monsoon formate, 7.4; acetate, 6.4). A difference in VWA values may have occurred as a result of the dilution factor; the total rain depth from collected samples in the monsoon was 46 cm while that in winter was 6.3 cm. Sources at this site may be anthropogenic and natural; scavenging from the vapour phase, washout of soil particles and emissions from vegetative sources are probably important sources for formate and acetate.