Measurements of carbonaceous aerosols at urban and remote marine sites

Concentrations of total carbon (TC) and black carbon (BC) in ambient air at Delhi (urban site) and over Indian Ocean (remote marine) were determined as a part of INDOEX programme. Over Indian Ocean, the TC and BC concentrations varied from 1.81 to 10.05 μg/m3 and 0.13 to 1.36 μg/m3 respectively during FFP-98. During the same season at Delhi, the TC and BC ranged from 7.50 to 40.27 μg/m3 and 0.49 to 2.84 μg/m3 respectively. In addition, at Delhi, the TC and BC concentrations were noticed very low during the monsoon season. However, the percentage BC during monsoon season was very high compared to winter season. High concentrations of TC were observed due to high organic carbon (OC) which might be due to biomass burning of various kinds. Similar to Delhi, near Indian coast, the concentration of OC was very high while towards ITCZ and across ITCZ, OC content was relatively lower

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>

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

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

Dry deposited fluxes of inorganic constituents after a fire in Delhi – A case study

144-147Dry deposition samples, after a fire in a plastic scrap market in Delhi, were collected and analysed for pH, electrical conductance, Cl, NO3,SO4, Na, K, Mg and Ca. The fluxes of Na, Ca, Cl and NO3 were observed to be 16, 7, 4 and 4 times higher than those under normal conditions. The higher fluxes of Cl may be attributed to the pyrolysis of PVC, while the higher fluxes of other components may be due to their presence in PVC or other materials burnt in the fire. Assuming that the fire influenced 1/4 part of Delhi, the total deposition of Ca, Cl, Na, NO3, SO4, K and Mg was estimated to be 61, 21, 16,16, 11, 11 and 5 tones, respectively, due to this fire incident

Measurements of formic and acetic acid levels in vapour phase at urban and semi-urban sites of Delhi

240-243The vapour phase acetic and formic acid levels were measured at two different sites of Delhi. Mean formic and acetic acid levels were found to be 1.66±0.81 and 5.83±2.24 ppbv, respectively, at the urban site of Rohini, while they were 2.51 ±1.22 and 2.92±1.78 ppbv, respectively, &nbsp;at National Physical Laboratory (NPL), a semi-urban site. Strong correlation between formic and acetic acids was observed at Rohini (correlation coefficient r=0.73) indicating similar source type for both the acids at this site, while at NPL, the correlation was very weak (r=0.19) indicating different sources of two acids

Progress in nitrogen deposition monitoring and modelling

The chapter reviews progress in monitoring and modelling of atmospheric nitrogen (N) deposition at regional and global scales. The Working Group expressed confidence in the inorganic N wet deposition estimates in U.S., eastern Canada, Europe and parts of East Asia. But, long-term wet or dry N deposition information in large parts of Asia, South America, parts of Africa, Australia/Oceania, and oceans and coastal areas is lacking. Presently, robust estimates are only available for inorganic N as existing monitoring generally does not measure the complete suite of N species, impeding the closing of the atmospheric N budget. The most important species not routinely measured are nitrogen dioxide (NO2), ammonia (NH3), organic N and nitric acid (HNO3). Uncertainty is much higher in dry deposition than in wet deposition estimates. Inferential modelling (combining air concentrations with exchange rates) and direct flux measurements are good tools to estimate dry deposition; however, they are not widely applied. There is a lack of appropriate parameterizations for different land uses and compounds for input into inferential models. There is also a lack of direct dry deposition flux measurements to test inferential models and atmospheric model estimates