13 research outputs found
Snow scavenging and phase partitioning of nitrated and oxygenated aromatic hydrocarbons in polluted and remote environments in central Europe and the European Arctic
Nitrated and oxygenated polycyclic aromatic hydrocarbons (N/OPAHs) are
emitted in combustion processes and formed in polluted air. Their
environmental cycling through wet deposition 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 17Â NPAHs, 8Â OPAHs, and
11Â nitrated mono-aromatic hydrocarbons (NMAHs), of which most N/OPAHs as well
as nitrocatechols, 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 (Ξ) at 273 K were
predicted using a multi-phase gas-particle partitioning model based on
polyparameter linear free energy relationships. ââNPAH concentrations
were 1.2–17.6 and 8.8â19.1 ng L−1 at urban and rural sites, whereas
ââOPAHs were 79.8–955.2 and 343.3–1757.4 ng Lâ1 at these sites,
respectively. 9,10-anthraquinone was predominant in snow aqueous and
particulate phases. 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 âââN/OPAHs and âââNMAHs
were found at the remote site (3.5 and 390.5 ng L−1, respectively).
N/OPAHs preferentially partitioned in snow particulate phase in accordance
with predicted Ξ, whereas NMAHs were predominant in the aqueous phase,
regardless of Ξ. 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 and dissolution during in- or below-cloud
scavenging.</p
Revolatilisation of soil-accumulated pollutants triggered by the summer monsoon in India
Persistent organic pollutants that have accumulated in soils can be
remobilised by volatilisation in response to chemical equilibrium with the
atmosphere. Clean air masses from the Indian Ocean, advected with the onset
of the summer monsoon, are found to reduce concentrations of
hexachlorocyclohexane (HCH), dichlorodiphenyltrichloroethane (DDT) and its
derivatives, endosulfan and polychlorinated biphenyls (PCBs) in air at a
mountain site (all in the range 5â20 pg mâ3) by 77 %, 70 %, 82 % and 45 %,
respectively. The analysis of fugacities in soil and air suggest that the
arrival of summer monsoon triggers net volatilisation or enhances ongoing
revolatilisation of the now-banned chemicals HCH and PCBs from
background soils in southern India. The response of the airâsoil exchange was
modelled using a regional air pollution model, WRF-Chem PAH/POP. The results
suggest that the air is increasingly polluted during transport by the
south-westerly monsoon winds across the subcontinent. Using a multidecadal
multimedia mass balance model, it is found that airâsurface exchange of HCH
and DDT have declined since the ban of these substances from agriculture, but
remobilisation of higher chlorinated PCBs may have reached a historical
high, 40 years after peak emission.</p
Polycyclic aromatic hydrocarbons, polychlorinated biphenyls, and chlorinated pesticides in background air in central Europe - investigating parameters affecting wet scavenging of polycyclic aromatic hydrocarbons
Concentrations of polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and chlorinated pesticides (CPs) were measured in air and precipitation at a background site in central Europe. Sigma PAH concentrations in air and rainwater ranged from 0.7 to 327.9 ng m(-3) and below limit of quantification (< LOQ) to 2.1 x 10(3) ng L-1. The concentrations of PCBs and CPs in rainwater were < LOQ. Sigma PCB and Sigma CP concentrations in air ranged from < LOQ to 44.6 and < LOQ to 351.7 pg m(-3), respectively. The potential relationships between PAH wet scavenging and particulate matter and rainwater properties were investigated. The concentrations of ionic species in particulate matter and rainwater were significantly correlated, highlighting the importance of particle scavenging process. Overall, higher scavenging efficiencies were found for relatively less volatile PAHs, underlining the effect of analyte gas-particle partitioning on scavenging process. The particulate matter removal by rain, and consequently PAH wet scavenging, was more effective when the concentrations of ionic species were high. In addition, the elemental and organic carbon contents of the particulate matter were found to influence the PAH scavenging
Composition and mass size distribution of nitrated and oxygenated aromatic compounds in ambient particulate matter from southern and central Europe - implications for the origin
Nitro-monoaromatic hydrocarbons (NMAHs), such as nitrocatechols, nitrophenols and nitrosalicylic acids, are important constituents of atmospheric particulate matter (PM) water-soluble organic carbon (WSOC) and humic-like substances (HULIS). Nitrated and oxygenated derivatives of polycyclic aromatic hydrocarbons (NPAHs and OPAHs) are toxic and ubiquitous in the ambient air; due to their light absorption properties, together with NMAHs, they are part of aerosol brown carbon (BrC). We investigated the winter concentrations of these substance classes in size-resolved PM from two urban sites in central and southern Europe, i.e. Mainz (MZ), Germany, and Thessaloniki (TK), Greece. The total concentration of 11 NMAHs (â11NMAH concentrations) measured in PM10 and total PM were 0.51-8.38 and 12.1-72.1 ng m-3 at the MZ and TK sites, respectively, whereas â7OPAHs were 47-1636 and 858-4306 pg m-3, and â8NPAHs were -3, respectively. NMAHs contributed 0.4% and 1.8% to the HULIS mass at MZ and TK, respectively. The mass size distributions of the individual substances generally peaked in the smallest or second smallest size fraction i.e. < 0.49 or 0.49-0.95 ”m. The mass median diameter (MMD) of NMAHs was 0.10 and 0.27 ”m at MZ and TK, respectively, while the MMDs of NPAHs and OPAHs were both 0.06 mu m at MZ and 0.12 and 0.10 ”m at TK. Correlation analysis between NMAHs, NPAHs, and OPAHs from one side and WSOC, HULIS, sulfate, and potassium from the other suggested that fresh biomass burning (BB) and fossil fuel combustion emissions dominated at the TK site, while aged air masses were predominant at the MZ site
Nitro-polycyclic aromatic hydrocarbons - gas-particle partitioning, mass size distribution, and formation along transport in marine and continental background air
Nitro-polycyclic aromatic hydrocarbons (NPAH) are ubiquitous in polluted air but little is known about their abundance in background air. NPAHs were studied at one marine and one continental background site, i.e. a coastal site in the southern Aegean Sea (summer 2012) and a site in the central Great Hungarian Plain (summer 2013), together with the parent compounds, PAHs. A Lagrangian particle dispersion model was used to track air mass history. Based on Lagrangian particle statistics, the urban influence on samples was quantified for the first time as a fractional dose to which the collected volume of air had been exposed. At the remote marine site, the 3â4-ring NPAH (sum of 11 targeted species) concentration was 23.7âŻpgâŻmâ3 while the concentration of 4-ring PAHs (6 species) was 426âŻpgâŻmâ3. The most abundant NPAHs were 2-nitrofluoranthene (2NFLT) and 3-nitrophenanthrene. Urban fractional doses in the range of <âŻ0.002â5.4âŻ% were calculated. At the continental site, the ÎŁ11âŻ3â4-ring NPAH and ÎŁ6âŻ4-ring PAH were 58 and 663âŻpgâŻmâ3, respectively, with 9-nitroanthracene and 2NFLT being the most concentrated amongst the targeted NPAHs. The NPAH levels observed in the marine background air are the lowest ever reported and remarkably lower, by more than 1 order of magnitude, than 1 decade before. Dayânight variation of NPAHs at the continental site reflected shorter lifetime during the day, possibly because of photolysis of some NPAHs. The yields of formation of 2NFLT and 2-nitropyrene (2NPYR) in marine air seem to be close to the yields for OH-initiated photochemistry observed in laboratory experiments under high NOx conditions. Good agreement is found for the prediction of NPAH gasâparticle partitioning using a multi-phase poly-parameter linear free-energy relationship. Sorption to soot is found to be less significant for gasâparticle partitioning of NPAHs than for PAHs. The NPAH levels determined in the south-eastern outflow of Europe confirm intercontinental transport potential
Air-soil exchange of toxic semivolatile substances (organochlorine pesticides, PCBs, PAHs) under the influence of the southwest monsoon in India
Evaluation of models for gas-particle partitioning of nitro- and oxy-aromatic hydrocarbons
Gas-particle partitioning is an important mechanism affecting the transport and fate of semi-volatile organic compounds (SOCs). The preferential partitioning of SOCs in the atmosphere depends on parameters such as the compoundâs molecular structure as well as particulate matter physical and chemical properties. This can be explained by various empirical and theoretical models based on single- or poly-parameter linear free energy relationship (ppLFER). To explain the SOC partitioning, each model considers one or more of the compoundâs physico-chemical properties or particulate matter characteristics. Despite the past efforts in determining the most appropriate model, discrepancies remain between the model prediction and observation because some models neglect certain intermolecular interactions. The aim of the present research was to apply a dual-phase as well as a multi-phase ppLFER model to predict gas-particle partitioning of nitro- and oxy- aromatic hydrocarbons. To this end, air samples (gas and particulate phase) were collected from urban and non-urban sites in Germany, France, and India. The poster will present the model predictions versus observations, and discuss their structural differences in details
One-year measurements of secondary organic aerosol (SOA) markers in the Paris region (France): Concentrations, gas/particle partitioning and SOA source apportionment
International audienc
Accelerated solvent extraction (ASE) for purification and extraction of silicone passive samplers used for the monitoring of organic pollutants
Evaluation of a conceptual model for gas-particle partitioning of polycyclic aromatic hydrocarbons using polyparameter linear free energy relationships
A model for gas-particle partitioning of polycyclic aromatic hydrocarbons (PAHs) was evaluated using polyparameter linear free energy relationships (ppLFERs) following a multiphase aerosol scenario. The model differentiates between various organic (i.e., liquid water-soluble (WS)/organic soluble (OS) organic matter (OM), and solid/semisolid organic polymers) and inorganic phases of the particulate matter (PM). Dimethyl sulfoxide and polyurethane were assigned as surrogates to simulate absorption into the above-mentioned organic phases, respectively, whereas soot, ammonium sulfate, and ammonium chloride simulated adsorption processes onto PM. The model was tested for gas and PM samples collected from urban and nonurban sites in Europe and the Mediterranean, and the output was compared with those calculated using single-parameter linear free energy relationship (spLFER) models, namely Junge-Pankow, Finizio, and Dachs-Eisenreich. The ppLFER model on average predicted 96 ± 3% of the observed partitioning constants for semivolatile PAHs, fluoranthene, and pyrene, within 1 order of magnitude accuracy with root-mean-square errors (RMSE) of 0.35â0.59 across the sites. This was a substantial improvement compared to Finizio and Dachs-Eisenreich models (37 ± 17 and 46 ± 18% and RMSE of 1.03â1.40 and 0.94â1.36, respectively). The Junge-Pankow model performed better among spLFERs but at the same time showed an overall tendency for overestimating the partitioning constants. The ppLFER model demonstrated the best overall performance without indicating a substantial intersite variability. The ppLFER analysis with the parametrization applied in this study suggests that the absorption into WSOSOM could dominate the overall partitioning process, while adsorption onto salts could be neglected