PM2.5-bound oxygenated PAHs, nitro-PAHs and parent-PAHs from the atmosphere of a Chinese megacity: Seasonal variation, sources and cancer risk assessment
Polycyclic aromatic compounds (PACs) in air particulate matter contribute considerably to the health risk of air pollution. The objectives of this study were to assess the occurrence and variation in concentrations and sources of PM2.5 bound PACs [Oxygenated PAHs (OPAHs) nitro PAHs and parent PAHs] sampled from the atmosphere of a typical Chinese megacity (Xi'an) to study the influence of meteorological conditions on PACs and to estimate the lifetime excess cancer risk to the residents of Xi'an (from inhalation of PM2.5 bound PACs). To achieve these objectives we sampled 24 h PM2.5 aerosols (once in every 6days from 5 July 2008 to 8 August 2009) from the atmosphere of Xi'an and measured the…
Uptake of gaseous formaldehyde by soil surfaces: a combination of adsorption/desorption equilibrium and chemical reactions
Abstract. Gaseous formaldehyde (HCHO) is an important precursor of OH radicals and a key intermediate molecule in the oxidation of atmospheric volatile organic compounds (VOCs). Budget analyses reveal large discrepancies between modeled and observed HCHO concentrations in the atmosphere. Here, we investigate the interactions of gaseous HCHO with soil surfaces through coated-wall flow tube experiments applying atmospherically relevant HCHO concentrations of ~ 10 to 40 ppbv. For the determination of uptake coefficients (γ), we provide a Matlab code to account for the diffusion correction under laminar flow conditions. Under dry conditions (relative humidity = 0 %), an initial γ of (1.1 ± 0.05…
Plant diversity enhances the natural attenuation of polycyclic aromatic compounds (PAHs and oxygenated PAHs) in grassland soils
Increasing plant species richness stimulates microbial activity in soil, which might favor biodegradation of polycyclic aromatic compounds (PACs). To explore the relationship between plant community composition and PACs in grassland soils (Fluvisols exposed to an urban atmosphere), we determined the concentrations of 29 polycyclic aromatic hydrocarbons (PAHs) and 15 oxygenated PAHs (OPAHs) in topsoils of 80 plots of a grassland biodiversity experiment. The plots included different levels of plant species richness (1, 2, 4, 8, 16, 60 species) and 1–4 plant functional groups (grasses, small herbs, tall herbs, and legumes) in a randomized block design. The concentrations (ng g−1) of ∑29PAHs an…
Atmospheric protein chemistry influenced by anthropogenic air pollutants: nitration and oligomerization upon exposure to ozone and nitrogen dioxide
The allergenic potential of airborne proteins may be enhanced via post-translational modification induced by air pollutants like ozone (O3) and nitrogen dioxide (NO2). The molecular mechanisms and kinetics of the chemical modifications that enhance the allergenicity of proteins, however, are still not fully understood. Here, protein tyrosine nitration and oligomerization upon simultaneous exposure of O3 and NO2 were studied in coated-wall flow-tube and bulk solution experiments under varying atmospherically relevant conditions (5–200 ppb O3, 5–200 ppb NO2, 45–96% RH), using bovine serum albumin as a model protein. Generally, more tyrosine residues were found to react via the nitration pathw…
Physicochemical uptake and release of volatile organic compounds by soil in coated-wall flow tube experiments with ambient air
Volatile organic compounds (VOCs) play a key role in atmospheric chemistry. Emission and deposition on soil have been suggested as important sources and sinks of atmospheric trace gases. The exchange characteristics and heterogeneous chemistry of VOCs on soil, however, are not well understood. We used a newly designed differential coated-wall flow tube system to investigate the long-term variability of bidirectional air–soil exchange of 13 VOCs under ambient air conditions of an urban background site in Beijing. Sterilized soil was investigated to address physicochemical processes and heterogeneous/multiphase reactions independently from biological activity. Most VOCs revealed net depositio…
Daytime formation of nitrous acid at a coastal remote site in Cyprus indicating a common ground source of atmospheric HONO and NO
Abstract. Characterization of daytime sources of nitrous acid (HONO) is crucial to understand atmospheric oxidation and radical cycling in the planetary boundary layer. HONO and numerous other atmospheric trace constituents were measured on the Mediterranean island of Cyprus during the CYPHEX campaign (CYPHEX = CYprus PHotochemical EXperiment) in summer 2014. Average volume mixing ratios of HONO were 35 pptv (±25 pptv) with a HONO/NOx ratio of 0.33, which was considerably higher than reported for most other rural and urban regions. Diel profiles of HONO showed peak values in the late morning (60±28 pptv around 09:00 local time), and persistently high mixing ratios during daytime (45±18 pptv…