Abstract. In this study we attempt to optimize the method for measuring black carbon (BC) in snow and ice using a Single Particle Soot Photometer (SP2). Beside the previously applied ultrasonic (CETAC) and Collison-type nebulizers we introduce a jet (Apex Q) nebulizer to aerosolize the aqueous sample for SP2 analysis. Both CETAC and Apex Q require small sample volumes (a few milliliters) which makes them suitable for ice core analysis. The Apex Q shows the least size-dependent nebulizing efficiency in the BC particle diameter range of 100–1000 nm. The CETAC has the advantage that air and liquid flows can be monitored continuously. All nebulizer-types require a calibration with BC standards for the determination of the BC mass concentration in unknown aqueous samples. We found Aquadag to be a suitable material for preparing calibration standards. Further, we studied the influence of different treatments for fresh discrete snow and ice samples as well as the effect of storage. The results show that samples are best kept frozen until analysis. Once melted, they should be sonicated for 25 min, immediately analyzed while being stirred and not be refrozen.
The atmospheric chemistry responsible for the conversion of SO2(g) to particulate sulfate in areas impacted by anthropogenic emission of SO2 is reviewed. The major reaction mechanism for the homogeneous conversion process in the absence of clouds or fog is the oxidation of SO2(g) by the hydroxyl radical. The rate of this conversion process increases with both increasing temperature and relative humidity. Correlations are described for the effects of these two variables on the conversion process, and equations given which correlate all of the available literature data for the homogeneous conversion process in ambient atmospheres. The conversion of S(IV) to sulfate via aqueous solution chemistry in clouds and fog is more complex and dependent on several variables, including concentrations of the principal oxidants (hydrogen peroxide and ozone), ammonia, droplet size and composition, and meteorology. The gas‐phase homogeneous conversion process can vary from less than 1% SO2(g) converted per hour to a maximum of about 10% converted per hour at high temperature and relative humidity. In contrast, the rate of conversion of S(IV) to sulfate in the aqueous‐phase homogeneous process is controlled by mixing and reactant limitations, rather than kinetic considerations. The process can involve 100% SO2 converted per hour under optimum conditions. Consequences of the various conversion processes on environmental quality are briefly illustrated with a discussion of the impact of sulfate‐containing aerosols on PM10 concentrations and visibility degradation.
Abstract. In this study we attempt to optimize the method for measuring black carbon (BC) in snow and ice using a single particle soot photometer (SP2). Beside the previously applied ultrasonic (CETAC) and Collison-type nebulizers we introduce a jet (APEX-Q) nebulizer to aerosolize the aqueous sample for SP2 analysis. Both CETAC and APEX-Q require small sample volumes (few milliliters) which makes them suitable for ice core analysis. The APEX-Q shows the least size-dependent nebulizing efficiency in the BC particle diameter range of 100–1000 nm. The CETAC has the advantage that air and liquid flows can be monitored continuously. All nebulizer-types require a calibration with BC standards for the determination of the BC mass concentration in unknown aqueous samples. We found Aquadag to be a suitable material for preparing calibration standards. Further, we studied the influence of different treatments for fresh discrete snow and ice samples as well as the effect of storage. The results show that samples are best kept frozen until analysis. Once melted, they should be sonicated for 25 min, immediately analyzed while being stirred and not be refrozen.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.