Is chlorophyll-athe best surrogate for organic matter enrichment in submicron primary marine aerosol?

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Rapid growth and high cloud-forming potential of anthropogenic sulfate aerosol in a thermal power plant plume during COVID lockdown in India

The COVID lockdown presented an interesting opportunity to study the anthropogenic emissions from different sectors under relatively cleaner conditions in India. The complex interplays of power production, industry, and transport could be dissected due to the significantly reduced influence of the latter two emission sources. Here, based on measurements of cloud condensation nuclei (CCN) activity and chemical composition of atmospheric aerosols during the lockdown, we report an episodic event resulting from distinct meteorological conditions. This event was marked by rapid growth and high hygroscopicity of new aerosol particles formed in the SO2 plume from a large coal-fired power plant in Southern India. These sulfate-rich particles had high CCN activity and number concentration, indicating high cloud-forming potential. Examining the sensitivity of CCN properties under relatively clean conditions provides important new clues to delineate the contributions of different anthropogenic emission sectors and further to understand their perturbations of past and future climate forcing

Scattering Properties of Aerosols in Clean Marine and Polluted Air

The light scattering properties of aerosols are affected by their chemical composition, size distribution and ambient relative humidity (RH) thus making them highly variable in both the spatial and temporal domains, which induces large uncertainty in their radiative effects on climate. Long-term aerosol measurements are key for developing a better understanding of their radiative properties. In the pristine marine environment, sea-spray aerosols are the precursors for cloud formation, which then act as a reflecting layer for incoming solar radiation. This increases the overall albedo of the marine environment, thus inducing a cooling effect on the climate which otherwise is towards warming because of the darker ocean surface. The main factors which influence the production mechanisms and radiative properties of sea-spray aerosols are windspeed, relative humidity and ocean near-surface layer chemical composition which in turn show seasonal behaviour. Hence it is vital to study the radiative properties of sea-spray aerosols with reference to these influencing parameters in order to reduce uncertainties in the estimation of the Earth¿s radiation budget and to obtain more reliable climate predictions. In the present work, the scattering properties of sea-spray aerosols with reference to above mentioned variables were investigated for clean marine air masses arriving at the Mace Head Atmospheric Research Station on the western periphery of Europe. Ten years (2001-2010) of aerosol light scattering data showed a clear seasonal trend in the aerosol light scattering coefficient (¿scat) and the Ångström exponent (Å). ¿scat values were maximum (35.3 Mm-1) in the month of January and minimum (13.7 Mm-1) in the month of July. A high positive correlation coefficient of 0.82 was also found for the summer season between percentage occurrence of lower ¿scat values (5-15 Mm-1) and the percentage occurrence of relatively large Å values (>1.2). A high positive correlation coefficient of 0.88 was found between wind-speed and ¿scat. These Abstract vi findings clearly indicate that high ¿scat values in the winter season are due to the contribution of wind driven sea-spray aerosols in the marine boundary layer. Subsequent studies found that ¿scat and the aerosol light backscattering coefficient (¿bscat) are dependent on the square of wind-speed ~ U2. It was also found that ¿scat for the low biological activity (LBA) period was approximately twice that found for the high biological activity (HBA) period. This difference was attributed to the combined effect of size distribution and refractive index whereas refractive index on its own accounted for 70% of the observed differeces A relative humidity (RH) scanning Nephelometer (Humidograph) instrument was built to study the effect of RH on aerosol light scattering properties. It was found that the aerosol light scattering enhancement (f(RH)) values for the clean marine air masses was 2.22 at 85% RH which is higher than the f(RH) value 1.77 for polluted air masses. Also, the effect of RH on backscatter fraction and single scattering albedo was to reduce the former by 20% and to increase the latter by 1-5% at 85% RH as compared to dry conditions. By combining the information about aerosol chemical composition and hygroscopic growth factor (HGF), a new HGF parameterization for seaspray aerosols was established. Using the HGF parameterization along with aerosol density and refractive index as inputs to a Mie radiative code, a dual hygroscopicity state, flipping from high-hygroscopicity and high f(RH) to lowhygroscopicity and low f(RH), of aerosol was found as the organic matter mixing volume percentage exceeded ~ 50%. The effect of organic enrichment on the top of atmosphere (TOA) direct radiative forcing (¿F) was to reduce the cooling contribution of sea-spray aerosol by ~4.5 times as compared to pure sea-salt spray

Seasonal Variation of the Aerosol Light Scattering Coefficient in Marine Air of the Northeast Atlantic

Aerosol light scattering measurements were carried out using a TSI 3563 Nephelometer at the Mace Head Atmospheric Research Station, on the west coast of Ireland from year 2001–2010. A strong seasonal trend in the aerosol light scattering coefficient at 550 nm (scat), for clean marine air masses, is observed with a high scat value, [average (geometric mean)] of 35.3 Mm−1 (29.5 Mm−1), in January and a low scat value of 13.7 Mm−1 (10.2 Mm−1), in July. This near threefold increase in the scat value during the winter season is because of the large contribution of wind-speed generated sea-salt particles in the marine boundary layer. A high positive correlation coefficient of 0.82 was found between the percentage occurrence of relatively large Ångström exponent (Å) values (>1.2) and the percentage occurrence of lower scat values (5–15 Mm−1) in the summer season. scat and wind-speed have a high positive correlation coefficient of 0.88 whereas Å and wind-speed have a negative correlation coefficient of −0.89. Å values during the summer months indicate the dominance of sub-m particles thus indicating the contribution of non-sea-salt sulphate and organics towards the scat as these species show an enhanced concentration during the summer months

Wind-driven influences on aerosol light scattering in north-east atlantic air

Ten years (2001-2010) of aerosol light-scattering measurements in N.E. Atlantic marine air are analysed to determine wind-speed related influences on scattering properties. The scattering coefficient and the backscattering coefficient dependency on wind speed (U) was determined for the winter (Low Biological Activity-LBA) and the summer seasons (High Biological Activity-HBA), and was found to be dependent on similar to U-2. In spite of having a U-2 dependency, scattering properties for the LBA-period are approximately twice those of the HBA-period. 96% of the LBA-HBA scattering difference can be explained by the combined effects of size distribution and refractive index differences while 70% of the scattering difference can be attributed to a difference in refractive index alone resulting from organic-matter enrichment during the HBA period. The 550 nm scattering coefficient was similar to 70 Mm(-1) for similar to 25 ms(-1) wind speeds, which is considerably higher than that encountered under polluted air masses in the same region. Citation: Vaishya, A., S. G. Jennings, and C. O\u27Dowd (2012), Wind-driven influences on aerosol light scattering in north-east Atlantic air, Geophys. Res. Lett., 39, L05805, doi:10.1029/2011GL050556

Seasonal variation of the aerosol light scattering coefficient in marine air of the northeast atlantic

Aerosol light scattering measurements were carried out using a TSI 3563 Nephelometer at the Mace Head Atmospheric Research Station, on the west coast of Ireland from year 2001-2010. A strong seasonal trend in the aerosol light scattering coefficient at 550nm (sigma(cat)), for clean marine air masses, is observed with a high sigma(cat) value, [average (geometric mean)] of 35.3Mm(-1) (29.5Mm(-1)), in January and a low sigma(cat) value of 13.7Mm(-1) (10.2Mm(-1)), in July. This near threefold increase in the sigma(cat) value during the winter season is because of the large contribution of wind-speed generated sea-salt particles in the marine boundary layer. A high positive correlation coefficient of 0.82 was found between the percentage occurrence of relatively large angstrom ngstrom exponent (angstrom) values (> 1.2) and the percentage occurrence of lower sigma(cat) values (5-15Mm(-1)) in the summer season. sigma(cat) and wind-speed have a high positive correlation coefficient of 0.88 whereas angstrom and wind-speed have a negative correlation coefficient of -0.89. angstrom values during the summer months indicate the dominance of sub-mu m particles thus indicating the contribution of non-sea-salt sulphate and organics towards the sigma(cat) as these species show an enhanced concentration during the summer months

Delivery of amphotericin B for effective treatment of Candida albicans induced dermal mycosis in rats via emulgel system: Formulation and evaluation

Background: Amphotericin B (AmB) is among the gold standard antifungal agents used for the treatment of the wide range of fungal infections. However, the drug has various side- effects. Transdermal approach for the delivery of drug is one of the accepted and convenient modes of drug delivery. Aim: The current work was designed to formulate and to evaluate the AmB emulgel system. Materials and Methods: In the preparation of AmB emulgel, Carbopol 930 was used as a gel in this study. The formulation was evaluated for viscosity, spreadability, drug content, drug release and in vitro and in vivo antifungal testing. Results: AmB emulgel was found to penetrate skin effectively and without any irritation. Further, in vivo studies revealed effective therapeutic potential against Candida albicans induced dermal mycosis. Conclusions: The current work, for the first time, revealed effective delivery of AmB across the skin

Bistable effect of organic enrichment on sea spray radiative properties

Primary-produced sea spray aerosol, typically comprising sea-salt, but also enriched with organic matter (OM) in biologically active oceanic regions, impacts the global radiative budget through contributions to aerosol optical depth. We show that sea spray light-scattering enhancement, f(RH), as a function of relative humidity (RH) is suppressed when enriched with OM. A new hygroscopic growth factor parameterization reveals a dual hygroscopicity state, flipping from high hygroscopicity and high f(RH) to low hygroscopicity and low f(RH) as the OM mixing volume percentage exceeds similar to 55% in sea spray. Under elevated wind speeds, this affects the Top-of-atmosphere direct radiative forcing (F) by reducing the cooling contribution of sea spray by similar to 5.5 times compared to pure sea-salt spray. These results suggest a positive feedback coupling between the marine biosphere, sea spray aerosol, and the direct radiative budget