Cloud processing of nitrate

Abstract

[1] The role of clouds in the transport and transformation of tropospheric pollutants was investigated through airborne measurements made out of Cleveland, Ohio, from 21 ] ratio was highest in the bulk cloud water and higher in the cloud droplet residuals compared with the below-cloud aerosols. Most of the nitrate entered the cloud water as HNO 3 , and in 30% of 43 size distributions examined, the nitrate in the cloud droplets was found in residual particle sizes smaller than those of sulfate. Simulations from a trace gas-aerosol-cloud parcel model show that this size difference results from differences in the processes by which nitrate and sulfate enter cloud water. The transfer of HNO 3 to cloud droplets is governed primarily by gas-phase mass transfer to the droplets, leading to greater accumulation in the smaller, more numerous droplets with higher total surface area. In contrast, much of the sulfate in the cloud water is the result of nucleation scavenging, which distributes the sulfate mass toward slightly larger sizes. The extent of separation between nitrate and sulfate is dependent on the cloud base sulfate size distribution and the factors that govern both HNO 3 and SO 2 uptake, with subsequent S(IV) oxidation.

Sources of nitrate in stratocumulus cloud water: Airborne measurements during the 2011 E-PEACE and 2013 NiCE studies

“…For instance, one airborne-based study in the vicinity of Ohio indicated that NO 3 À enters cloud water predominantly through partitioning of gaseous HNO 3 , whereas SO 4 2À enters mostly through nucleation scavenging (Hayden et al, 2008 ; furthermore, they concluded that scavenging of vapors (e.g., HNO 3 ) by drops was not responsible for their results. Different conclusions in these two studies motivate an analysis of how this chemical mass concentration ratio varies inside and outside of clouds in our study region.…”

“…It is noted that C-ToF-AMS NO 3 À generally was below detection limits on cloud-free days in the marine boundary layer. The peak ratio in cloud water could be a result of (i) (Hayden et al, 2008); the heated air stream in the CVI inlet ranged between approximately 30e35 C.…”

Sampling Artifacts from Conductive Silicone Tubing

“…Hayden et al (2008) reported a siloxane contaminant resulting from a silicone sealant used in a counter-flow virtual impactor. Since we did not use silicone sealant in any particle accessible regions of the sampling line, we dismissed sealant as a potential contamination source.…”

In situ chemical composition measurement of individual cloud residue particles at a mountain site, southern China

“…These studies were mainly conducted at sites in North America including Wyoming (Pratt et al, 2010a), Ohio (Hayden et al, 2008), Oklahoma (Berg et al, 2009), Florida Twohy et al, 2005) and California (Coggon et al, 2014); in Europe including Schmücke (Roth et al, 2016;Schneider et al, 2017), Jungfraujoch (Kamphus et al, 2010), Åresku-tan (Drewnick et al, 2007) and Scandinavia (Targino et al, 2006); in the Arctic (Zelenyuk et al, 2010); in Central America (Cziczo et al, 2013); in western Africa (Matsuki et al, 2010); and in marine areas (Twohy and Anderson, 2008;Twohy et al, 2009;Shingler et al, 2012).…”