Inorganic Gases Research Articles

Characterization and variability of inorganic aerosols and their gaseous precursors at a suburban site in northern France over one year (2015–2016)

Measurements of inorganic precursor gases (NO, NO2, HONO, NH3, SO2 and HCl) and PM2.5 inorganic water-soluble ions (NO3−, SO42−, NH4+, Cl−, Na+, Mg2+, Ca2+, K+) were performed at a suburban site in northern France for the first time using a MARGA 1S with an hourly time-resolution from August 2015 to July 2016. The observations were compared with other independent methods: HR-ToF-AMS, BAM-1020, SO2 and NH3 gas monitors over shorter time periods. The dominant particulate species were NO3−, SO42− and NH4+, with average annual mass contributions to PM2.5 of 28.0%, 13.1% and 9.9%, respectively. The highest concentrations of SIA were found in spring likely due to increased agricultural emissions of precursor gases. A strong formation of ammonium nitrate (NH4NO3) over nighttime was observed for every season and attributed to the condensation of its gaseous precursors NH3 and HNO3. The partitioning of NH4NO3 between the gas and particulate phases was compared with that obtained with the thermodynamic module ISORROPIA II and generally found to agree well except for HNO3. The local or distant origin of each species was determined by means of Non parametric Wind Regression (NWR) polar plots and Potential Source Contribution Function (PSCF) maps. SIA main origins were regional with significant contributions from Belgium, the Netherlands and western Germany. Additionally, several high PM2.5 episodes that lasted more than 2 days were analyzed, showing some common features.

In situ synthesis of carbon doped porous silicon nanocomposites as high-performance anodes for lithium-ion batteries

We demonstrate the in situ synthesis of carbon doped porous silicon (Si/C) nanocomposites by a simple thermal displacement process between Mg2Si and inorganic gas CO2 in one-step. Via the decomposition of Mg2Si, the reduction process occurred between Mg and CO2, leading the uniform doping of many distributed tiny carbon nanoparticles into Si. Meanwhile, the porous structure was formed after an acid treatment. When worked as anodes for lithium-ion batteries, the as-prepared s-porous Si/C nanocomposites exhibited good cycling stability and high-rate capability, which were superior to the porous Si and porous Si/C nanocomposites. It was revealed that the enhanced electrochemical properties could be ascribed to the novel porous structure and doped carbon nanoparticles that can buffer the volume expansion, as well as enhance the electronic conductivity of Si. The reaction mechanism was well investigated by studying the influence of reaction temperature and raw Mg2Si particle size on the morphology and component of the porous Si/C nanocomposites.

Quantitative Analysis by Thermogravimetry-Mass Spectrum Analysis for Reactions with Evolved Gases.

During energy conversion, material production, and metallurgy processes, reactions often have the features of unsteadiness, multistep, and multi-intermediates. Thermogravimetry-mass spectrum (TG-MS) is seen as a powerful tool to study reaction features. However, reaction details and reaction mechanics have not been effectively obtained directly from the ion current of TG-MS. Here, we provide a method of an equivalent characteristic spectrum analysis (ECSA) for analyzing the mass spectrum and giving the mass flow rate of reaction gases as precise as possible. The ECSA can effectively separate overlapping ion peaks and then eliminate the mass discrimination and temperature-dependent effect. Two example experiments are presented: (1) the decomposition of CaCO3 with evolved gas of CO2 and the decomposition of hydromagnesite with evolved gas of CO2 and H2O, to evaluate the ECSA on single-component system measurement and (2) the thermal pyrolysis of Zhundong coal with evolved gases of inorganic gases CO, H2, and CO2, and organic gases C2H4, C2H6, C3H8, C6H14, etc., to evaluate the ECSA on multi-component system measurement. Based on the successful calibration of the characteristic spectrum and relative sensitivity of specific gas and the ECSA on mass spectrum, we demonstrate that the ECSA accurately gives the mass flow rates of each evolved gas, including organic or inorganic gases, for not only single but multi-component reactions, which cannot be implemented by the traditional measurements.

Evolution profile of gases during coal carbonization and relationship between their amounts and the fluidity or coke strength

The evolution of inorganic-gases (H2, CO, CO2 or H2O) and hydrocarbon gases CH4, C2(C2H4, C2H6), or C3(C3H6 + C3H8) during the carbonization of caking coals is examined to clear the influence of the evolution amount of these gases on the Gieseler maximum fluidity (MF) and coke strength (DI15015). The samples are carbonized at 3 °C/min up to 1000 °C in high-purity He. The MF and the evolution profile of gases depend on the coal type. A negative relation exists between evolution amounts of gases, except for H2, until initial softening temperature (IST) and MF values. Additionally, the evolution amounts of inorganic gases, except for H2, until the IST increase with the increase of the carboxyl (COOH) group contents in raw coal. Moreover, the MF values trends to decrease with the increase in the COOH in raw samples. Thereby, it is found that the inherently-present coal-O adverse affect coal fluidity. Drum index (DI15015) of coke increases with the increase of C%-dry ash free (daf), fixed carbon (FC) %-dry, and reflectance (R0) vol% in raw coal, while the values decrease with the increase O%-daf and volatile matter (VM) %-dry. The DI15015 values exhibit an increasing trend with regard to the amount of the evolved H2 or CH4 during the carbonization. However, the values decrease as the amount of O-containing gases increased. A similar trend is observed in semi-coke and coke, where the values decrease as the remaining O% increased. Although the proportion of turbostatic-C (T-carbon) in coke depends on the coal type, DI15015 increases as the proportion of T-carbon increased. Therefore, it is found that the coal-O also has an adverse influence on coke strength.

Effects of HZSM-5 on volatile products obtained from the fast pyrolysis of lignin and model compounds

This study aimed to experimentally investigate the effect of HZSM-5 on the distribution of volatile products, especially carbon monoxide (CO), C1–C5 hydrocarbons and aromatic hydrocarbons (AHs) during catalytic pyrolysis of lignin and lignin model compounds. Catechol was pyrolyzed using a two-stage tubular reactor (TS-TR) connected to a gas chromatography system over HZSM-5 at 550–950 °C. Forty-three products, including four inorganic gases, twenty C1–C5 hydrocarbons, and nine AHs were quantified using three GC-columns. Results indicated that HZSM-5 accelerated the catechol conversion with a large amount of CO and AHs produced. C1–C5 hydrocarbons were formed during non-catalytic pyrolysis of model compounds, and consumed quickly during HZSM-5 catalytic pyrolysis of catechol. Catalytic pyrolysis of phenol, guaiacol and syringol was carried out at 650 °C in the TS-TR over HZSM-5. HZSM-5 obviously promoted the conversion of lignin model compounds, and largely increased the yield of volatile products especially CO and AHs. Three lignin samples were also catalytically pyrolyzed over HZSM-5 in the TS-TR at 650 °C. HZSM-5 increased the yield of C2-C3 hydrocarbons and AHs, and reduced the yield of oxygenated compounds. HZSM-5 could promote the formation of AHs (lower than 10 wt%) during lignin pyrolysis, but not as obviously as during model compounds pyrolysis (higher than 19 wt%). High yields of char and tar would account for the low catalytic efficiency of HZSM-5 during lignin pyrolysis.

Methodologies for analysis of air environment. Certification and arrangement of intra laboratory control of the quality of analysis results

A computational and experimental method of certification and arrangement of intra laboratory control of the methods for analysis of air environment, i.e., air of the working zone, atmosphere air and industrial emissions into the atmosphere, is developed. Note that nowadays a rather small number of standard samples (SS) of air environment (calibration gas mixtures (CGM)) is available for less than thirty substances with determined maximum permissible concentrations (MPC) (inorganic gases and light organic compounds). About 100 sources of microcflows (MF) are also developed for light organic compounds. Such a narrow set of developed SS hinders determination of the accuracy indicators on the basis of the certification experiment for the vast majority of the methods used for analysis of air samples and, in turn, keeps out of stating standards for intra-laboratory control and implementation of the procedures of operational control and control of the stability. For those techniques (in the lack of calibration gas mixtures and sources of microflows), the error characteristics are estimated usually by calculations with exception of the stability of the calibration curves and error characteristics of the individual sampling stages which are determined experimentally. The proposed method implies a conditional division of the technique into two stages: sampling and analytical stages. For the stage of sampling, the error characteristics are determined by the calculation-experimental method, for the analytical stage, by the experimental method, similar to other methods for analysis of condensed media. The possibility of arrangement of the intra-laboratory control of the analytical stage and implementation of all the algorithms of both operational and stability control, including construction of Shewhart’s control charts is shown. The proposed method makes it possible to arrange certification of the majority of similar techniques used in the sphere of state regulation of ensuring the uniformity of measurements that have not been previously certified and provided with standard samples in the form of calibration gas mixtures and sources of microflows.

Characterization of emissions from diesel backup generators in Cambodia

This study provided a comprehensive emission characterization of the diesel backup generators commonly used in the commercial sector in Cambodia using the hood experiment method. Two backup generators were selected and referred to as E1 (small size, 18.4 kW) and E2 (larger size, 92 kW). The monitoring parameters included particulate matter (PM), 16 USEPA priority polycyclic aromatic hydrocarbons (PAHs, separately in PM and gas phase), and inorganic gases (CO, CO2, SOx and NOx). The PM compositions of element carbon (EC) and organic carbon (OC), PAHs, water-soluble inorganic ions, and elements were characterized to develop the source emission profile. The emission factors (EFs) were higher for E1 (smaller engine) as compared to E2 for all monitored parameters except for NOx. PM EFs were 2.03 ± 0.18 g kg−1 for E1 and 1.05 ± 0.01 g kg−1 for E2. Total 16 PAHs EFs, about 86% were in gas phase, were 2.0 ± 0.03 mg kg−1 for E1 and 1.03 ± 0.03 for E2. The obtained PM profile showed significant components in the descending order of OC, EC, soluble ions, elements and PAHs. The smaller engine also had higher PAHs toxicity in term of BaPeq, mainly because of more heavy PAHs found in the PM phase. The PAH concentration profiles and the diagnostic ratios obtained in this study were in the range of the literature reported values for diesel engines and could be useful for PAH source identification. The annual emissions of diesel backup generators used in the commercial sector in Cambodia were estimated for 2015 which showed the largest emission share from Phnom Penh followed by Siem Reap.

From Gas Sensors to Biomimetic Artificial Noses

Since the first attempts to mimic the human nose with artificial devices, a variety of sensors have been developed, ranging from simple inorganic and organic gas detectors to biosensing elements incorporating proteins of the biological olfactory system. In order to design a device able to mimic the human nose, two major issues still need to be addressed regarding the complexity of olfactory coding and the extreme sensitivity of the biological system. So far, only 50 of the approximately 300–400 functioning olfactory receptors have been de-orphanized, still a long way from breaking the human olfactory code. On the other hand, the exceptional sensitivity of the human nose is based on amplification mechanisms difficult to reproduce with electronic circuits, and perhaps novel approaches are required to address this issue. Here, we review the recent literature on chemical sensing both in biological systems and artificial devices, and try to establish the state-of-the-art towards the design of an electronic nose.

Gas Chromatography Columns Based on Functionalized Polymer for the Analysis of Catalytic Reaction Products

For the first time in this work, two methods of modification of poly(1-trimethylsilyl-1-propyne) (PTMSP) and the possibilities of its application for the determination of catalytic reaction products are described. Aging of PTMSP is determined by three mechanisms: physical, chemical and mechanical effects. Free volume decreases, texture characteristics change, and partial oxidation of the polymer takes place in the structure of PTMSP. The chromatographic behavior of PTMSP, which was used for 18 months, differs significantly from the properties of the freshly prepared polymer. Thermal stability and chemical inertness are the main requirements for chromatographic materials. Therefore, two methods were used to stabilize the aging process. The first method consisted of preparing a mixed phase by adding disubstituted polyacetylene poly(1-phenyl-1-propyne) (PPP) to PTMSP. The resulting sorbent Chromosorb Р NAW + 10 wt% (97% PTMSP + 3% PPP) is efficient for solving a wide range of chromatographic tasks such as simultaneous analysis of hydrocarbons and sulfur-containing inorganic gases, analysis of chlorine-substituted methanes in CCl4 and thiophene in benzene, separation of hydrocarbons and aromatic compounds. It should be noted, the low selectivity of separation of oxygen-containing components on this sorbent. A second method of PTMSP modification, namely the oxidation treatment with nitrous oxide, is proposed. It was shown that the polymer is oxidized by means of its C=C double bond with the formation of ketone, carbonyl and hydroxyl groups. The increase in number of those groups in the polymer changed the polarity of PTMSP. The change in polarity of polymer led to the selectivity of separations, including oxygen-containing substances. Examples of separations of aliphatic and aromatic hydrocarbons, oxygen- and halogen-containing substances are presented. Chromatographic characteristics of the sorbent Chromosorb P NAW + 10 wt% (97% PTMSP + 3% PPP) and PTMSP oxidized by nitrous oxide are stable in the temperature range from 30 to 220 °C for at least 1.5 years of continuous operation.

Stratospheric Injection of Brominated Very Short‐Lived Substances: Aircraft Observations in the Western Pacific and Representation in Global Models

AbstractWe quantify the stratospheric injection of brominated very short‐lived substances (VSLS) based on aircraft observations acquired in winter 2014 above the Tropical Western Pacific during the CONvective TRansport of Active Species in the Tropics (CONTRAST) and the Airborne Tropical TRopopause EXperiment (ATTREX) campaigns. The overall contribution of VSLS to stratospheric bromine was determined to be 5.0 ± 2.1 ppt, in agreement with the 5 ± 3 ppt estimate provided in the 2014 World Meteorological Organization (WMO) Ozone Assessment report (WMO 2014), but with lower uncertainty. Measurements of organic bromine compounds, including VSLS, were analyzed using CFC‐11 as a reference stratospheric tracer. From this analysis, 2.9 ± 0.6 ppt of bromine enters the stratosphere via organic source gas injection of VSLS. This value is two times the mean bromine content of VSLS measured at the tropical tropopause, for regions outside of the Tropical Western Pacific, summarized in WMO 2014. A photochemical box model, constrained to CONTRAST observations, was used to estimate inorganic bromine from measurements of BrO collected by two instruments. The analysis indicates that 2.1 ± 2.1 ppt of bromine enters the stratosphere via inorganic product gas injection. We also examine the representation of brominated VSLS within 14 global models that participated in the Chemistry‐Climate Model Initiative. The representation of stratospheric bromine in these models generally lies within the range of our empirical estimate. Models that include explicit representations of VSLS compare better with bromine observations in the lower stratosphere than models that utilize longer‐lived chemicals as a surrogate for VSLS.

Carrier Mobility-Dominated Gas Sensing: A Room-Temperature Gas-Sensing Mode for SnO2 Nanorod Array Sensors.

Adsorption-induced change of carrier density is presently dominating inorganic semiconductor gas sensing, which is usually operated at a high temperature. Besides carrier density, other carrier characteristics might also play a critical role in gas sensing. Here, we show that carrier mobility can be an efficient parameter to dominate gas sensing, by which room-temperature gas sensing of inorganic semiconductors is realized via a carrier mobility-dominated gas-sensing (CMDGS) mode. To demonstrate CMDGS, we design and prepare a gas sensor based on a regular array of SnO2 nanorods on a bottom film. It is found that the key for determining the gas-sensing mode is adjusting the length of the arrayed nanorods. With the change in the nanorod length from 340 to 40 nm, the gas-sensing behavior changes from the conventional carrier-density mode to a complete carrier-mobility mode. Moreover, compared to the carrier density-dominating gas sensing, the proposed CMDGS mode enhances the sensor sensitivity. CMDGS proves to be an emerging gas-sensing mode for designing inorganic semiconductor gas sensors with high performances at room temperature.

Kinetics and Product Formation during the Photooxidation of Butanol on Atmospheric Mineral Dust.

Mineral dust particles have photochemical properties that can promote heterogeneous reactions on their surfaces and therefore alter atmospheric composition. Even though dust photocatalytic nature has received significant attention recently, most studies have focused on inorganic trace gases. Here, we investigated how light changes the chemical interactions between butanol and Arizona test dust, a proxy for mineral dust, under atmospheric conditions. Butanol uptake kinetics were measured, exploring the effects of UV light irradiation intensity (0-1.4 mW/cm2), relative humidity (0-10%), temperature (283-298 K), and butanol initial concentration (20-55 ppb). The composition of the gas phase was monitored by a high-resolution proton-transfer-reaction mass spectrometer (PTR-ToF-MS) operating in H3O+ mode. Water was observed to play a significant role, initially reducing heterogeneous processing of butanol but enhancing reaction rates once it evaporated. Gas phase products were identified, showing that surface reactions of adsorbed butanol led to the emission of a variety of carbonyl containing compounds. Under actinic light these compounds will photolyze and produce hydroxyl radicals, changing dust processing from a sink of VOC into a source of reactive compounds.

Modeling reactive ammonia uptake by secondary organic aerosol in CMAQ: application to the continental US

Abstract. Ammonium salts such as ammonium nitrate and ammonium sulfate constitute an important fraction of the total fine particulate matter (PM2.5) mass. While the conversion of inorganic gases into particulate-phase sulfate, nitrate, and ammonium is now well understood, there is considerable uncertainty over interactions between gas-phase ammonia and secondary organic aerosols (SOAs). Observations have confirmed that ammonia can react with carbonyl compounds in SOA, forming nitrogen-containing organic compounds (NOCs). This chemistry consumes gas-phase NH3 and may therefore affect the amount of ammonium nitrate and ammonium sulfate in particulate matter (PM) as well as particle acidity. In order to investigate the importance of such reactions, a first-order loss rate for ammonia onto SOA was implemented into the Community Multiscale Air Quality (CMAQ) model based on the ammonia uptake coefficients reported in the literature. Simulations over the continental US were performed for the winter and summer of 2011 with a range of uptake coefficients (10−3–10−5). Simulation results indicate that a significant reduction in gas-phase ammonia may be possible due to its uptake onto SOA; domain-averaged ammonia concentrations decrease by 31.3 % in the winter and 67.0 % in the summer with the highest uptake coefficient (10−3). As a result, the concentration of particulate matter is also significantly affected, with a distinct spatial pattern over different seasons. PM concentrations decreased during the winter, largely due to the reduction in ammonium nitrate concentrations. On the other hand, PM concentrations increased during the summer due to increased biogenic SOA (BIOSOA) production resulting from enhanced acid-catalyzed uptake of isoprene-derived epoxides. Since ammonia emissions are expected to increase in the future, it is important to include NH3 + SOA chemistry in air quality models.

Selective guest inclusion by crystals of calixarenes: potential for application as separation materials

Recently, much attention has been devoted towards the development of methods for the capture and separation of inorganic gases and organic compounds with high selectivity and efficiency using nanoporous materials. Unlike metal–organic frameworks and covalent organic network polymer, nanoporous molecular crystals (NMCs) do not have extended network structures through coordination or covalent bonding. Instead, they are composed of discrete organic molecules with only weak noncovalent interactions between them. Calixarenes, used as artificial hosts for molecular recognition, constitute a representative class of NMCs that exhibit “porosity without pores.” Despite the absence of empty-channels, calixarene crystals can absorb various inorganic gases and organic compounds, thereby undergoing a guest-induced structural change. Thus, because of their ability to precisely discriminate between molecules of similar sizes and structures, such NMCs show great potential for application as separation materials. This review summarizes reports on the absorption and inclusion of inorganic gases and organic molecules with crystals of calixarenes and their derivatives and discusses their potential as separation materials.

Methods and Devices for the Preparation of Standard Gas Mixtures

A review of methods for the preparation of standard gas mixtures (SGMs) with the known concentrations of organic and inorganic gases and vapors is presented. The classification of methods is proposed and their advantages and disadvantages are compared. Along with the widely known thermal diffusion and gasextraction methods and devices for the preparation of SGMs functioning on their basis, i.e., sources of gas and vapor microflows and vapor-phase sources of gas mixtures, the review considers and discusses metrological possibilities proposed by Russian researchers of chromatomembrane and chromato-desorption methods of SGM preparation and corresponding instrumentation.

Co-gasification of waste wood with coal: Release of condensable and non-condensable inorganic gas species

This letter deals with the in-situ determination of important inorganic gas phase species in high temperature gasification product gas. The fuels are waste wood and German hard coal which were co-gasified at 1500 °C in lab-scale experiments. The release of the vapour species 34H2S+, 36HCl+, 56KOH+, 58NaCl+, 60COS+, 64SO2+, and 74KCl+ was determined online by a Molecular Beam Mass Spectrometer. The experimentally determined data sets were compared to calculated data sets in order to distinguish the underlying release mechanisms. The release behaviour of the inorganics 34H2S+, 36HCl+, 60COS+, 64SO2+ and 58NaCl+ cannot be attributed to simple mixing and dilution effect only. Further, it is shown that the release of these inorganics is significantly influenced by secondary reactions, e.g. competitive reaction with S and Cl.

Study on pyrolysis characteristics of pretreated high‑sodium (Na) Zhundong coal by skimmer-type interfaced TG-DTA-EI/PI-MS system

Various pretreatment methods has been used to upgrade the high-Na Zhundong coal to solve the inherent problem with its thermal conversion. To provide a better understanding of pyrolysis characteristics of the pretreated high-Na Zhundong coal, a system of thermogravimetry-differential thermal analysis coupled with mass spectrometry equipped with skimmer-type interface and with electron ionization and photoionization capability (TG-DTA-EI/PI-MS system), was employed to analyze qualitatively the pyrolysis characteristics of the pretreated high-Na Zhundong coals. Three types of coal samples including the raw coal, H2O-washed coal, and HCl-washed coal were pyrolyzed in this study. The total pyrolysis yield, evolved volatile gases composition and individual gas evolving behavior were evaluated. It was shown that the pretreatments affected insignificantly the total yield but did significantly the volatile gases composition, the individual gas yield and production rate. The larger aromatic compounds of C7H8O (anisole), C9H12 (propylbenzene), and C10H14 (butylbenzene) disappeared gradually after the coals were pretreated. Especially, the HCl-washing pretreatment reduced greatly the yield and production rate of inorganic gases of H2, CO, CO2, and aromatic compounds of C6H6O (phenol), C8H10 (ethylbenzene), whereas improved greatly those of the smaller aliphatic compound of C3H6 (propene). It was believed that the absence of the NH4Ac-soluble Na species and HCl-soluble Na species was a main factor to affect the volatile gases composition, the individual gas yield and production rate, through altering the reaction routine of bond breaking and cross-linking during pyrolysis.

Cerium-substituted magnetite: Fabrication, characterization and sonocatalytic activity assessment

The present paper reports the sonocatalytic activity of cerium-substituted-magnetite for removal of oxytetracycline (OTC). The catalyst was prepared through a chemical route (co-precipitation, Fe3-xCexO4) and a mechanical procedure (CeO2/Fe3O4). Subsequently, the physico-chemical characteristics of both samples were determined using XRD, BET, SEM, EDX, TEM, Dot-mapping, FT-IR, DRS, and VSM analysis and compared to pristine magnetite and ceria. Afterwards, the effects of various operational conditions were assessed on sonocatalytic performance of Fe2.8Ce0.2O4 for OTC removal and the obtained optimal conditions were applied to compare the resulted DE with so-synthesized Fe3O4, CeO2, and CeO2/Fe3O4 samples. Fe2.8Ce0.2O4 (0.75 g/L) exhibited great catalytic performance for sono-degradation of OTC under its unchanged pH and US power of 300 W, wherein about 88% and 64% of OTC was removed at its initial concentrations of 20 and 50 mg/L. Moreover, the effects of the addition of a number of oxidants, organic and inorganic compounds and gases on the sonocatalytic degradation of OTC were evaluated under the identical condition. The obtained results presented an effective sonocatalytic system based on the synergistic action of Fe2.8Ce0.2O4 under ultrasonic irradiation.

Amperometric Gas Sensors as a Low Cost Emerging Technology Platform for Air Quality Monitoring Applications: A Review.

This review examines the use of amperometric electrochemical gas sensors for monitoring inorganic gases that affect urban air quality. First, we consider amperometric gas sensor technology including its development toward specifically designed air quality sensors. We then review recent academic and research organizations' studies where this technology has been trialed for air quality monitoring applications: early studies showed the potential of electrochemical gas sensors when colocated with reference Air Quality Monitoring (AQM) stations. Spatially dense networks with fast temporal resolution provide information not available from sparse AQMs with longer recording intervals. We review how this technology is being offered as commercial urban air quality networks and consider the remaining challenges. Sensors must be sensitive, selective, and stable; air quality monitors/nodes must be electronically and mechanically well designed. Data correction is required and models with differing levels of sophistication are being designed. Data analysis and validation is possibly the biggest remaining hurdle needed to deliver reliable concentration readings. Finally, this review also considers the roles of companies, urban infrastructure requirements, and public research in the development of this technology.

Human exposure to carcinogens in ambient air in Denmark, Finland and Sweden

The concentrations of seventeen pollutants (particulate mass fractions PM2.5 and PM10, a range of metals, inorganic gases and organic compounds) are for the first time analyzed in a screening of the carcinogenic risk at a resolution of 1 × 1 km2 in ambient air in three Nordic countries. Modelled annual mean air concentrations in 2010 show no exceedances of the EU air quality limit, guideline or target values. The only modelled exceedance of US-EPA 1:100,000 cancer risk concentrations (0.12 ng/m3, US-EPA IRIS, 2015) occurs for B(a)P in Denmark, for approximately 80% of the Danish population. However, the EU target value threshold of 1 ng/m3 for B(a)P is not exceeded in the modelled values in any parts of Denmark. No emission data for B(a)P were available for the whole domain of the other two considered Nordic countries and important uncertainties are still related to the emissions. Long-range transport is significant for the concentrations of all of the considered pollutants, except for B(a)P that commonly originates mostly from local residential wood combustion. The ambient air concentrations of NOx, SO2, Cd, Cr and Pb also have significant contributions from national sources; 45–65% for NOx and SO2, and for the metals from 15 to 60% in urban areas and from 1 to 20% in rural areas, within the considered Nordic area. High national contributions occur especially in urban air, due to primarily road traffic, residential wood combustion, energy production and industrial point sources. It is recommended to monitor the influence from residential wood combustion more extensively, and to analyze longer time trends for long-term human exposure.