Snow scavenging and phase partitioning of nitrated and oxygenated aromatic hydrocarbons in polluted and remote environments in central Europe and the European Arctic

Abstract

Nitrated and oxygenated polycyclic aromatic hydrocarbons (N/OPAHs) are emitted in combustion processes and formed in polluted air. Their precipitation cycling has hardly been studied. Fresh snow samples at urban and rural sites in central Europe, as well as surface snow from a remote site in Svalbard were analysed for 17 NPAHs, 9 OPAHs, and 11 nitrated mono-aromatic hydrocarbons (NMAHs), of which most N/OPAHs as well as nitrocatechols, 5 nitrosalicylic acids, and 4-nitroguaiacol are studied for the first time in precipitation. In order to better understand the scavenging mechanisms, the particulate mass fractions (Ө) at 273K were predicted using a multiphase gas-particle partitioning model based on polyparameter linear free energy relationships. ∑NPAH concentrations were 1.2-17.6 and 8.8-19.1 ng L -1 at urban and rural sites, whereas ∑OPAHs were 0.3-1.1 and 0.5-2.4 µg L -1 at these sites, respectively.Acenaphthoquinone and 9,10-anthraquinone were predominant in snow dissolved and particulate phase, respectively. 10 NPAHs were only found in the particulate phase with 9-nitroanthracene being predominant followed by 2-nitrofluoranthene. Among NMAHs, 4-nitrophenol showed the highest abundance in both phases. The levels found for nitrophenols were in the same range or lower than those reported in the 1980s and 1990s. The lowest levels of ∑OPAHs and ∑NMAHs were found at the remote site (9.2 and 390.5 ng L -1 , respectively). N/OPAHs preferentially partitioned in snow particulate phase in accordance with predicted Ө, whereas NMAHs were predominant in the 15 dissolved phase, regardless of Ө. It is concluded that the phase distribution of non-polar N/OPAHs in snow is determined by their gas-particle partitioning prior to snow scavenging, whereas that for polar particulate phase substances, i.e. NMAHs, is determined by an interplay between gas-particle partitioning in the aerosol, particle mass size distribution, and dissolution during in-or below-cloud scavenging.Atmos. Chem. Phys. Discuss., https://doi

A New Structural Classification Scheme for Dissolved Organic Sulfur in Urban Snow from North China

“…By compiling thousands of CHOS, this study provides a new structural classification of CHOS for atmospheric samples. Our results indicate that low-medium mass CHOS species (< 500 Da) in snow, with medium O/S ratio (5)(6)(7)(8)(9)(10)(11), are related with typical known secondary organosulfates and anthropogenic-derived anionic surfactants. The feasibility of the new classification on CHONS molecules will be performed in another study by taking consideration of variety oxidation states of sulfur and nitrogen.…”

“…S4). High O/S molecules (10)(11)(12)(13)(14)(15)(16) with high mass (≥ 500 Da) made a significant contribution to this difference. To be specific, the high mass organic sulfur containing molecules, as discussed above, were largely distributed in subgroups C and D. Highly unsaturated molecules (subgroup C) might be related to SOA compounds from biomass burning.…”

“…Detailed molecular classification of common CHOS in the snow samples could be found in Text S3. It should be noted that these common CHOS molecules are largely in medium O/S ratios (5)(6)(7)(8)(9)(10)(11) with low-medium mass (< 500 Da) (Figure 2b and 2c). More than one hundred (138-150) organosulfate and sulfonate formulas were detected in each snow sample (Figure S8), contributing about 10% of the common CHOS molecules.…”

“…9 Carboxylic acids, amino acids, sugars and phenolic compounds were used as chemical markers to investigate the aerosol-snow transfer processes. 10 Shahpoury et al 11 suggested that the interplay between gas-particle partitioning in the aerosol and dissolution during in-or below-cloud scavenging determines the phase distribution of polar particulate substances.…”

Is the oxidative potential of components of fine particulate matter surface-mediated?

“…The analysis was performed in negative chemical ionization mode with methane used as the ionization gas. The analytes were separated on a 30 m DB-5 ms capillary column (0.25 mm ID, 0.25 μm film thickness; J&W, Santa Clara, USA) with helium (99.99%; Westfalen, Münster, Germany) as a carrier gas (Shahpoury et al 2018 ). Analyte recoveries (Table S2 ) from ELF and QFs ranged 85–116% ( n = 4 replicates).…”