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Samples of rainwater (RW) were collected to characterize the chemistry and sources in two representative megacities at Pune (Southwest) and Delhi (Northern) India from 2011 to 2014 across two seasons: monsoon (MN) and non-monsoon (NMN). Collected RW samples were analyzed for major chemical constituents (F − , Cl − , SO 4 2− , NO 3 − , NH 4 + , Na + , K + , Ca 2+ , and Mg 2+ ), pH and conductivity. In addition, bicarbonate (HCO 3 − ) was also estimated. The mean pH values of the RW were >6 at Pune and <6 at Delhi and 4% and 26% were acidic, respectively. The mean sum of all measured ionic species in Pune and Delhi was 304.7 and 536.4 μeq/l, respectively, indicating that significant atmospheric pollution effects in these Indian mega cities. Both the Ca 2+ and SO 4 2− were the dominant ions, accounting for 43% (Pune) and 54% (Delhi) of the total ions. The sum of measured ions during the NMN period was greater than the NM period by a factor of 1.5 for Pune (278.4: NM and 412.1: NMN μeq/l) and a factor of about 2.5 for Delhi (406 and 1037.7 μeq/l). The contributions of SO 4 2− and NO 3 − to the RW acidity were ∼40% and 60%, respectively, at Pune and correspondingly, 36% and 64% at Delhi. The concentrations of secondary aerosols (SO 4 2− and NO 3 − ) were higher by a factor of two and three when the air masses were transported to Pune from the continental side. At Delhi, the concentrations of SO 4 2− , NO 3 − , Ca 2+ , and Mg 2+ were significantly higher when the air masses arrive from Punjab, Haryana, and Pakistan indicating the greater atmospheric pollution over the Indo-Gangetic Plain. Positive matrix factorization was applied to the source apportionment of the deposition fluxes of these ions. Three factors were obtained for Pune and four for Delhi. The sources at Pune were secondary aerosols from fossil fuel combustion, soil dust, and marine, whereas, at Delhi, the sources were soil, fossil fuel combustion, biomass burning, and industrial chlorine. [ABSTRACT FROM AUTHOR]

One year of aerosol size distribution and chemical composition measurements conducted at the Zeppelin station on Svalbard (78° 58′ N and 11° 53′E) is presented. The data, which cover the period March 2000–April 2001, show a very strong seasonal dependence of the number mode particle size. The transition from one seasonal characteristic regime to the other occurs rapidly and takes place over only a few days. As expected, the largest integrated aerosol surface and particle volumes are observed during the Arctic haze period in spring. On a seasonal scale the total number density covariate with the incoming solar radiation, which points to photochemistry as an important component during new particle formation in the Arctic summer. However, maximum number densities are observed during the second part of the summer concurrent with a relative reduction in the incoming radiation. The onset of this period of enhanced particle number densities coincides in time with the surface temperature remaining steadily above the freezing point and the melting of the snow cover. A similar transition occurring over the Siberian tundra is proposed as a potential source of aerosol precursor gases, which could explain the enhanced particle number densities during the second half of the summer. A second maximum of ammonium in particles during late summer and fall, concurrent with a reduction in sea salt and nss-sulfate present in particles would be consistent with continental source without a significant anthropogenic component. The data presented in the study also illustrate the usefulness of measurements that extend over several seasons where phenomenon that occur with in one season, the summer in this case, can be put into context. [Copyright &y& Elsevier]

To determine the direct and indirect effects of aerosols on climate, it is important to know the spatial and temporal variations in cloud condensation nuclei (CCN) concentrations. Although many types of CCN measurements are available, extensive CCN measurements are challenging because of the complexity and high operating cost, especially in remote areas. As aerosol optical depth (AOD) can be readily observed by remote sensing, many attempts have been made to estimate CCN concentrations from AOD. In this study, the CCN–AOD relationship is parameterized based on CCN ground measurements from the Zeppelin Observatory (78.91° N, 11.89° E, 474 m asl) in the Arctic region. The AOD measurements were obtained from the Ny-Ålesund site (78.923° N, 11.928° E) and Modern-Era Retrospective Analysis for Research and Applications, Version 2 reanalysis. Our results show a CCN–AOD correlation with a coefficient of determination R2 of 0.59. Three additional estimation models for CCN were presented based on the following data: (i) in situ aerosol chemical composition, (ii) in situ aerosol optical properties, and (iii) chemical composition of AOD obtained from reanalysis data. The results from the model using in situ aerosol optical properties reproduced the observed CCN concentration most efficiently, suggesting that the contribution of BC to CCN concentration should be considered along with that of sulfate. ● Relationship between CCN concentration and AOD was parameterized with statistically significant. ● AOD from MERRA-2 and MODIS were comparable with ground-based measurements of AOD. ● In-situ aerosol optical properties reproduce the CCN most efficiently. [ABSTRACT FROM AUTHOR]