Chemical characteristics of PM<SUB>10</SUB> aerosols and airmass trajectories over Bay of Bengal and Arabian sea during ICARB

For the first time, chemical characterization of PM10 aerosols was attempted over the Bay of Bengal (BoB) and Arabian Sea (AS) during the ICARB campaign. Dominance of SO42-, NH4+ and NO3- was noticed over both the regions which indicated the presence of ammonium sulphate and ammonium nitrate as major water soluble particles playing a very important role in the radiation budget. It was observed that all the chemical constituents had higher concentrations over Bay of Bengal as compared to Arabian Sea. Higher concentrations were observed near the Indian coast showing influence of landmass indicating that gaseous pollutants like SO2, NH3 and NO x are transported over to the sea regions which consequently contribute to higher SO42-, NH4+ and NO3- aerosols respectively. The most polluted region over BoB was 13&#176;-19&#176;N and 70&#176;-90&#176;E while it was near 11&#176;N and 75&#176;E over AS. Although the concentrations were higher over Bay of Bengal for all the chemical constituents of PM10 aerosols, per cent non-sea salt (nss) fraction (with respect to Na) was higher over Arabian Sea. Very low Ca2+ concentration was observed at Arabian Sea which led to higher atmospheric acidity as compared to BoB. Nss SO42-alone contributed 48% of total water soluble fraction over BoB as well as AS. Ratios SO42- /NO3- over both the regions (7.8 and 9 over BoB and AS respectively) were very high as compared to reported values at land sites like Allahabad (0.63) and Kanpur (0.66) which may be due to very low NO.3 over sea regions as compared to land sites. Air trajectory analysis showed four classes: (i) airmass passing through Indian land, (ii) from oceanic region, (iii) northern Arabian Sea and Middle East and (iv) African continent. The highest nss SO42- was observed during airmasses coming from the Indian land side while lowest concentrations were observed when the air was coming from oceanic regions. Moderate concentrations of nss SO2- 4 were observed when air was seen moving from the Middle East and African continent. The pH of rainwater was observed to be in the range of 5.9-6.5 which is lower than the values reported over land sites. Similar feature was reported over the Indian Ocean during INDOEX indicating that marine atmosphere had more free acidity than land atmosphere

Estimation of SO<SUB>4</SUB> contribution by dry deposition of SO<SUB>2</SUB> onto the dust particles in India

Dustfall deposition fluxes of major water-soluble components Cl, NO<SUB>3</SUB>, SO<SUB>4</SUB>, NH<SUB>4</SUB>, 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 SO<SUB>4</SUB> contributed by dry deposition of SO<SUB>2</SUB> on the dust particles was estimated. Using these estimates, further the ambient concentrations of SO<SUB>2</SUB> were calculated which were in a very good positive agreement with experimental concentration of SO<SUB>2</SUB>

Real-time wet scavenging of major chemical constituents of aerosols and role of rain intensity in Indian region

Real-time simultaneous studies on chemical characteristics of rainwater and PM10 aerosols were carried out to understand the scavenging of major chemical components in Indian region. The concentrations of Ca2+, NH4+, SO42− and NO3− were observed to be lower in the aerosol samples collected during rain as compared to before and after rain events. The most significant reduction was noticed for Ca2+ (74%) during rain which showed highest scavenging ratio (SR) and indicated that below-cloud scavenging is an effective removal process for Ca2+ in Indian region. Among non-sea salt components, Ca2+ had highest SR at Hyderabad indicating typical characteristics of crustal influence as abundance of calcium carbonate in soil dust has been reported in India. However, the levels of these major chemical components gradually got build-up in due course of time. After rain events, the levels of SO42− aerosols were noticed to be substantially higher (more than double) within 24 h. In general, scavenging ratios for all components (except Ca2+, NH4+ and K+) were higher over BOB as compared to Hyderabad. The maximum fall in aerosol levels (BR minus AR) was observed during continuous and low intensity rain events that did not allow building up of aerosol concentrations

Temporal Variation and Concentration Weighted Trajectory Analysis of Lead in PM10 Aerosols at a Site in Central Delhi, India

Ambient levels of lead (Pb) in PM10 were studied at a site in Central Delhi for the period of one year during day and night. The annual mean concentration of lead has been observed as 625 and 1051 ng/m3 during day and night time, respectively. The seasonal averaged concentrations of Pb have followed the order winter > postmonsoon > summer > monsoon. Highest levels of lead have been observed in winter with 31% samples exceeding the CPCB-NAAQS value as 1000 ng/m3. Lead levels during winter have been found to be 5.7 times higher than in monsoon, which might be attributed to prevailing meteorological conditions and more biomass burning. The low levels of Pb during summer might be attributed to its higher dispersion in the atmosphere. A sharp rise of Pb during postmonsoon might be linked to the local nonpoint sources, more biomass burning, and shifting of boundary layer. However, the higher concentrations of lead were observed during night time in all the seasons of the year as compared to those of the day time. To identify the potential source regions of Pb, Concentration Weighted Trajectories (CWT) have been plotted which showed higher influence of local sources during winter and postmonsoon while showing distant sources during summer

Water soluble components of dry deposition at Delhi

151-154Dry deposition rates of major water soluble components, namely CI, NO3, SO4, NH4, Na, K, Ca and Mg, are estimated at National Physical Laboratory, New Delhi. The pH of water soluble fraction of dry deposition samples has been observed to lie between 5.8 and 8.0 at this site which is in agreement with soil pH of this region. It suggested that dry deposition is mainly dominated by soil-derived particles which add higher alkalinity due to presence of components like Na, K, Ca, etc. Dry deposition rates are found to be maximum for Ca. In general, the dry deposition rates are highest in summer, moderate in winter and lowest in monsoon

Chemical characteristics of trace metals in PM10 and their concentrated weighted trajectory analysis at Central Delhi, India

Trace metals associated with PM10 aerosols and their variation during day and nighttime as well as during different seasons have been studied for the year 2012. PCA analysis suggested 5 PCs, which accounted for 86.8% cumulative variance. PC1 accounted for 30% with a significant loading of metals of anthropogenic origin, while PC2 showed 28% variance with the loading of metals of crustal origin. These trace metals showed seasonal distinct day and night time characteristics. The concentrations of Cu, Pb, and Cd were found to be higher during nighttime in all the seasons. Only Fe was observed with significantly higher mean concentrations during daytime of all seasons except monsoon. The highest mean values of Cu, Cd, Zn, and Pb during post-monsoon might be attributed to winds advection over the regions of waste/biomass burning and industrial activities in Punjab and Haryana regions. Furthermore, concentration weighted trajectory analysis suggested that metals of crustal origin were contributed by long-range transport while metals of anthropogenic and industrial activities were contributed by regional/local source regions. (C) 2016 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences

Impact of anthropogenic emissions and open biomass burning on carbonaceous aerosols in urban and rural environments of Indo-Gangetic Plain

Carbonaceous aerosols were studied at two locations, urban and rural, on day and night time basis for 1 year in the Indo-Gangetic Plain. Average OC and EC concentrations at the urban site were observed as 25.6 and 13.7 mu g/m(3), while at the rural site as 29.6 and 12.8 mu g/m(3). Exceptionally high OC and EC values were observed during November indicating the impact of large-scale open biomass burning, in the post-harvesting season, on carbonaceous aerosols in the region. The high OC and EC levels were observed during the winter season and low during the monsoon season. Estimated secondary organic carbon accounted for 44.4 and 39.5 % of OC at the urban site and 58.3 and 35.6 % of OC at the rural site during day and night time, respectively. A good correlation was observed between OC and EC indicating a common origin of these species at both the sites. OC/EC ratios mainly in the range 1-4 at the urban site suggested the influence of motor vehicle exhaust as the main emission source whereas at the rural site, an occurrence of OC/EC > 4 indicated the impact of residential wood smoke and biomass burning. PM2.5 samples were analyzed for eight individual carbon fractions (OC1, OC2, OC3, OC4, EC1, EC2, EC3, and OP). Principal component analysis of eight carbon fractions indicated the influence of anthropogenic emissions at both the sites

Investigation of alkaline nature of rain water in India

Increased industrialization and urbanization lead to the atmospheric acidity which causes acid rain. However, in India, the nature of rain water has been observed to be alkaline. The reason for alkaline nature of rain water is found to be the buffering of acidity by soil-derived aerosols which are rich in Ca. Over the Indian Ocean where concentrations of soil dust are negligible, the acid rain has been observed to be a common phenomenon during INDOEX campaigns. In the Indian subcontinent, observations have indicated that rain becomes acidic when the buffering potential of rain water is weak. The weak buffering potential may be due to less interference of soil dust, acidic nature of soil or very high influence of industrial source

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

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<SUB>2</SUB> equilibrium. Out of 28 rain events, only two events were observed in acidic range (&lt;5.6) which occurred after continuous rains. The equivalent concentration of components followed the order: Ca<SUP>2+</SUP>&gt;Cl<SUP>-</SUP>&gt;SO<SUB>4</SUB><SUP>2+</SUP>&gt;NH<SUB>4</SUB>+&gt;Na<SUP>+</SUP>&gt;HCO<SUB>3</SUB><SUP>-</SUP>&gt;NO<SUB>3</SUB><SUP>-</SUP>&gt;K<SUP>+</SUP>&gt;Mg<SUP>2+</SUP>. 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