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India aims to reduce pollution from solid residential fuel use and promote clean energy through the Pradhan Mantri Ujjwala Yojana (PMUY) scheme launched in 2016. The scheme targeted below-poverty-line (BPL) families using traditional stoves by providing free LPG connections. BPL families in urban slums and village dwellers of Delhi are major users of solid residential fuel. This study investigates the overlying reasons by surveying ∼6500 households from ∼700 urban slums and villages and identifying high consumption areas and fuel use patterns. The urban slums and villages of Delhi reported a total usage of 0.415 Mt. residential fuels annually for the year 2019 (72 % fuelwood, 27 % dung cake, 0.002 % crop residue, and 0.001 % coal). An interrelation of household energy consumption patterns, socio-economic demographics, and kitchen characteristics is also presented in the study. The energy-ladder hypothesis was found to be validated in slums while the linearity of the hypothesis was contradicted in rural areas as the use of traditional stoves was driven by food preferences rather than economic constraints. Predictive models were developed to estimate residential fuel usage for space heating and water heating during winters, which are not reported by NSSO annual reports. The study also calculated the gross calorific values of biomass fuels to assess their energy content. This information aids in further understanding biomass combustion efficiency and the importance of transitioning to cleaner energy sources like LPG for sustainable practices. This study estimated an additional annual $10.04 million in Government aid is sufficient to minimize pollutant load emanating from residential fuel combustion by providing free LPG refills to economically weaker households. This action has the potential to reduce residential fuel usage for cooking significantly leading to a decrease in pollution levels across the megacity. • Slums and rural areas of Delhi used 0.415 Mt. solid residential fuels in 2019. • Annual usage of 0.3 Mt. FW, 0.112 Mt. DC, minimal consumption of CR and coal • The energy ladder hypothesis holds in slums but is contradicted in villages. • Two predictive models used for estimating SBFs for space and water heating. • 10 hotspot grids over Delhi accounted 51 % of total solid residential fuel usage. • A simple policy proposed for mitigating solid residential fuels in Delhi. [ABSTRACT FROM AUTHOR]

The critical ecological process of animal-mediated pollination is commonly facilitated by odour cues. These odours consist of volatile organic compounds (VOCs), often with short chemical lifetimes, which form the strong concentration gradients necessary for pollinating insects to locate a flower. Atmospheric oxidants, including ozone pollution, may react with and chemically alter these VOCs, impairing the ability of pollinators to locate a flower, and therefore the pollen and nectar on which they feed. However, there is limited mechanistic empirical evidence to explain these processes within an odour plume at temporal and spatial scales relevant to insect navigation and olfaction. We investigated the impact of ozone pollution and turbulent mixing on the fate of four model floral VOCs within odour plumes using a series of controlled experiments in a large wind tunnel. Average rates of chemical degradation of α-terpinene, β-caryophyllene and 6-methyl-5-hepten-2-one were slightly faster than predicted by literature rate constants, but mostly within uncertainty bounds. Mixing reduced reaction rates by 8–10% in the first 2 m following release. Reaction rates also varied across the plumes, being fastest at plume edges where VOCs and ozone mixed most efficiently and slowest at plume centres. Honeybees were trained to learn a four VOC blend equivalent to the plume released at the wind tunnel source. When subsequently presented with an odour blend representative of that observed 6 m from the source at the centre of the plume, 52% of honeybees recognised the odour, decreasing to 38% at 12 m. When presented with the more degraded blend from the plume edge, recognition decreased to 32% and 10% at 6 and 12 m respectively. Our findings highlight a mechanism by which anthropogenic pollutants can disrupt the VOC cues used in plant-pollinator interactions, which likely impacts on other critical odour-mediated behaviours such as mate attraction. [Display omitted] • Ozone pollution degrades the components of floral odour plumes • Reaction rates were fastest at the plume edges and slowest at the plume centre • Higher O 3 levels increased plume intermittency and reduced odour filament width • Bees recognition of floral odours declined significantly following reaction with O 3 [ABSTRACT FROM AUTHOR]

Common air pollutants, such as nitrogen oxides (NO x), emitted in diesel exhaust, and ozone (O 3), have been implicated in the decline of pollinating insects. Reductionist laboratory assays, focused upon interactions between a narrow range of flowering plant and pollinator species, in combination with atmospheric chemistry models, indicate that such pollutants can chemically alter floral odors, disrupting the cues that foraging insects use to find and pollinate flowers. However, odor environments in nature are highly complex and pollination services are commonly provided by suites of insect species, each exhibiting different sensitivities to different floral odors. Therefore, the potential impacts of pollution-induced foraging disruption on both insect ecology, and the pollination services that insects provide, are currently unknown. We conducted in-situ field studies to investigate whether such pollutants could reduce pollinator foraging and as a result the pollination ecosystem service that those insects provide. Using free-air fumigation, we show that elevating diesel exhaust and O 3 , individually and in combination, to levels lower than is considered safe under current air quality standards, significantly reduced counts of locally-occurring wild and managed insect pollinators by 62–70% and their flower visits by 83–90%. These reductions were driven by changes in specific pollinator groups, including bees, flies, moths and butterflies, and coincided with significant reductions (14–31%) in three different metrics of pollination and yield of a self-fertile test plant. Quantifying such effects provides new insights into the impacts of human-induced air pollution on the natural ecosystem services upon which we depend. [Display omitted] • Common air pollutants (e.g. nitrogen oxides and ozone) can react with floral odors. • Both pollutants resulted in severely reduced insect pollinator foraging efficiency. • Specific insect pollinator groups demonstrated differential responses to pollutants. • Metrics of insect-mediated plant pollination decreased under both pollutants. • Air pollution has the potential to disrupt other odor-mediated ecosystem services. [ABSTRACT FROM AUTHOR]

Mixing ratios and fluxes of volatile organic compounds (VOCs) were measured by PTR-MS (and GC-MS) and virtual disjunct eddy covariance during a three-week field campaign in summer 2009 within and above a Douglas fir (Pseudotsuga menziesii) forest in Speulderbos, the Netherlands. Measurements included the first non-terpenoid species fluxes and mixing ratios for Douglas fir canopy. Above-canopy emissions of monoterpenes were comparable to previous studies of P. menziesii, with estimated standard emission factors for the first and second halves of the campaign of 0.8 ± 0.4 and 0.8 ± 0.3 µg gdw-1 h-1, and temperature coefficients of 0.19 ± 0.06 and 0.08 ± 0.05 °C-1, respectively. Estimated isoprene standard emission factors for the two halves of the campaign were 0.09 ± 0.12 and 0.16 ± 0.18 µg gdw-1 h-1. Fluxes of several non-terpenoid VOCs were significant, with maximum fluxes greater than has been measured for other coniferous species. a-Pinene was the dominant monoterpene within and above the canopy. Within-canopy mixing ratios of individual species were generally greatest in early evening consistent with reduced vertical mixing and continued temperature-dependent emissions. Acetaldehyde, acetone and monoterpenes had elevated mixing ratios toward the bottom of the canopy (5-10 m) with assumed contribution from the large quantities of forest-floor leaf litter. MBO (2-methyl-3-buten-2-ol) and estragole had peak mixing ratios at the top of the canopy and are known to have coniferous sources. MVK + MACR (methyl vinyl ketone and methacrolein) also had highest mixing ratios at the top of the canopy consistent with formation from in-canopy oxidation of isoprene. The work highlights the importance of quantifying a wider variety of VOCs from biogenic sources than isoprene and monoterpenes. [ABSTRACT FROM AUTHOR]

Methanesulfonic acid (MSA) is an important product from the oxidation of dimethyl sulfide (DMS), and thus is often used as a tracer for marine biogenic sources and secondary organic aerosol. MSA also contributes to aerosol mass and potentially to the formation of cloud condensation nuclei and new particles. However, measurements of MSA at high temporal resolution in the remote Arctic are scarce, which limits our understanding of its formation, climate change impact and regional transport. Here, we applied a validated quantification method to determine the mass concentration of MSA and non-sea salt sulfate (nss-SO 4) in PM 2.5 in the marine boundary layer, using a high resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) during a research cruise to the Arctic and North Atlantic Ocean, between 55 °N and 68 °N (26th May to June 23, 2022). With this method, the concentrations of MSA in the remote Arctic marine boundary layer were determined for the first time. Results show that the average MSA concentration was 0.025 ± 0.03 μg m−3, ranging from <0.01 to 0.32 μg m−3. The lowest MSA level was found towards the northern leg of the cruise (near Sisimut (67 °N)) with air masses from sea ice over the northern polar region, and the highest MSA concentrations were observed over the Atlantic open ocean. The diurnal cycles of gas MSA, particulate MSA and nss-SO 4 peaked in the afternoon, about one hour later than that of peak of solar radiation, which suggests that photochemical process is an important mechanism for the conversion of DMS into MSA above the remote ocean. The mass ratio of MSA to nss-SO 4 (MSA/nss-SO 4) presents a temperature dependence, which indicates that the addition branching pathway favors MSA formation, while thermal decay of intermediate radicals could be a possible pathway for sulfate formation. Finally, we found that the MSA/nss-SO 4 ratio is around 0.22-0.25 in the remote northern marine atmosphere. [Display omitted] • A validated quantification method was employed to determine the particulate MSA mass concentration by HR-TOF-AMS. • The OH-initiated pathway is an important mechanism for the conversion of DMS into MSA above the remote ocean. • Mass ratio of MSA to nss-SO 4 presents temperature dependence during the whole cruise. [ABSTRACT FROM AUTHOR]

Under the EU Air Quality Directive (AQD) 2008/50/EC member states are required to undertake routine monitoring of PM 2.5 composition at background stations. The AQD states for PM 2.5 speciation this should include at least: nitrate (NO 3 −), sulfate (SO 4 2−), chloride (Cl−), ammonium (NH4+), sodium (Na+), potassium (K+), magnesium (Mg2+), calcium (Ca2+), elemental carbon (EC) and organic carbon (OC). Until 2017, it was the responsibility of each country to determine the methodology used to report the composition for the inorganic components of PM 2.5. In August 2017 a European standard method of measurement of PM 2.5 inorganic chemical components (NO 3 −, SO 4 2−, Cl−, NH 4 +, Na+, K+, Mg2+, Ca2+) as deposited on filters (EN16913:2017) was published. From August 2019 this then became the European standard method. This filter method is labour-intensive and provides limited time resolution and is prone to losses of volatile compounds. There is therefore increasing interest in the use of alternative automated methods. For example, the UK reports hourly PM 2.5 chemical composition using the Monitor for AeRosols and Gases in Ambient air (MARGA, Metrohm, NL). This study is a pre-assessment review of available data to demonstrate if or to what extent equivalence is possible using either the MARGA or other available automatic methods, including the Aerosol Chemical Speciation Monitor (ACSM, Aerodyne Research Inc. US) and the Ambient Ion Monitor (AIM, URG, US). To demonstrate equivalence three objectives were to be met. The first two objectives focused on data capture and were met by all three instruments. The third objective was to have less than a 50% expanded uncertainty compared to the reference method for each species. Analysis of this objective was carried out using existing paired datasets available from different regions around the world. It was found that the MARGA (2006–2019 model) had the potential to demonstrate equivalence for all species in the standard, though it was only through a combination of case studies that it passed uncertainty criteria. The ACSM has the potential to demonstrate equivalence for NH 4 +, SO 4 2−, and in some conditions NO 3 −, but did not for Cl− due to its inability to quantify refractory aerosol such as sea salt. The AIM has the potential for NH 4 +, NO 3 −, SO 4 2−, Cl− and Mg2+. Future investigations are required to determine if the AIM could be optimised to meet the expanded uncertainty criterion for Na+, K+ and Ca2+. The recommendation is that a second stage to demonstrate equivalence is required which would include both laboratory and field studies of the three candidate methods and any other technologies identified with the potential to report the required species. • Comparison of EN16913:2017 filter method for speciated inorganic PM 2.5 against automatic methods. • Automatic methods have the potential to demonstrate equivalence for some or all species. • Further field and laboratory studies are required to demonstrate equivalence for speciated PM 2.5 [ABSTRACT FROM AUTHOR]

Some of the world's highest air pollution episodes occur in Delhi, India and studies have shown particulate matter (PM) is the leading air pollutant to cause adverse health effects on Delhi's population. It is therefore vital to chart sources of PM over long time periods to effectively identify trends, particularly as multiple air quality mitigation measures have been implemented in Delhi over the past 10 years but remain unevaluated. An automated offline aerosol mass spectrometry (AMS) method has been developed which has enabled high-throughput analysis of PM filters. This novel offline-AMS method uses an organic solvent mix of acetone and water to deliver high extraction recoveries of organic aerosol (OA) (95.4 ± 8.3%). Positive matrix factorisation (PMF) source apportionment was performed on the OA fraction extracted from PM 10 filter samples collected in Delhi in 2011, 2015 and 2018 to provide snapshots of the responses of OA to changes in sources in Delhi. The nine factors of OA resolved by PMF group into four primary source categories: traffic, cooking, coal-combustion and burning-related (solid fuel or open burning). Burning-related OA made the largest contribution during the winter and post-monsoon, when total OA concentrations were at their highest. Annual mean burning-related OA concentrations declined by 47% between 2015 and 2018, likely associated with the 2015 ban on open waste burning and controls and incentives to reduce crop-residue burning. Compositional analysis of OA factors shows municipal waste burning tracers still present in 2018, indicating further scope to reduce burning-related OA. The closure of the two coal power stations, along with initiatives to decrease coal use in industry, businesses, and residential homes, resulted in a significant decrease (87%) in coal-combustion OA. This corresponds to a 17% reduction in total OA, which shows the effectiveness of these measures in reducing PM 10. Increases in traffic OA appear to have been offset by the introduction of the Bharat stage emissions standards for vehicles as the increases do not reflect the rapid increase in registered vehicles. However, daytime restrictions on heavy goods vehicles (HGVs) entering the city is linked to large increases in PM 10 during the winter and post-monsoon, likely because the large influx of diesel-engine HGVs during the early mornings and evenings is timed with a particularly low planetary boundary layer height that enhances surface concentrations. Average concentrations of PM 10 OA factors during each of the four seasons of the years 2011, 2015 and 2018. [Display omitted] • A novel offline aerosol mass spectrometry method has been developed. • Burning-related OA was the largest contributor during peak PM concentrations. • Despite a ban, open waste and crop-residue burning were active in 2018. • Coal power station closures and coal-use reductions likely decreased OA. • Heavy goods vehicles restrictions may inadvertently cause increases in OA. [ABSTRACT FROM AUTHOR]

Replies to comments made on the article 'The European Air Quality Framework Directive and atmospheric mercury: the wrong tool for the job,' by David S. Lee, David Fowler and Eiko Nemitz, which appeared in a 2002 issue of the journal 'Atmospheric Environment.' Assessment of the potential for adverse exposures to mercury; Expected benefits of introducing an air quality limit.

• We show how reduced form and complex models can be applied in combination to inform air pollution policy development. • We compare PM 2.5 concentrations calculated by both a reduced-form and a complex ACTM, showing good agreement. • Both models agree well with observations of PM 2.5 and SIA concentrations from national monitoring networks. • We present this comparison for the current (2018) and selected future (2040) emissions scenarios in the United Kingdom. • We confirm the robustness of a reduced-form model to evaluate alternative futures, through comparison with an Eulerian ACTM. Simulation models can be valuable tools in supporting development of air pollution policy. However, exploration of future scenarios depends on reliable and robust modelling to provide confidence in outcomes which cannot be tested against measurements. Here we focus on the UK Integrated Assessment Model, a fast reduced-form model with a purpose to support policy development with modelling of multiple alternative future scenarios, and the EMEP4UK model which is a complex Eulerian Atmospheric Chemistry Transport Model requiring significant computing resources. The EMEP4UK model has been used to model selected core scenarios to compare with UKIAM, and to investigate sensitivity studies such as the interannual variability in response to meteorological differences between years. This model intercomparison addresses total PM 2.5 , primary PM 2.5 and Secondary Inorganic Aerosol concentrations for a baseline of 2018 and selected scenarios for projections to 2040. This work has confirmed the robustness of the UK Integrated Assessment Model for assessing alternative futures through a direct comparison with EMEP4UK. Both models have shown good agreement with measurements, and EMEP4UK shows an ability to replicate past trends. These comparisons highlight how a combination of reduced-form modelling (UKIAM) and complex chemical transport modelling (EMEP4UK) can be effectively used in support of air pollution policy development, informing understanding of projected futures in the context of emerging evidence and uncertainties. [ABSTRACT FROM AUTHOR]

Abstract: The Aerosol Time-of-Flight Mass Spectrometer (ATOFMS) is one of few instruments able to measure the size and mass spectra of individual airborne particles with high temporal resolution. Data analysis is challenging and in the present study, we apply three different techniques (PMF, ART-2a and K-means) to a regional ATOFMS dataset collected at Harwell, UK. For the first time, Positive Matrix Factorization (PMF) was directly applied to single particle mass spectra as opposed to clusters already generated by the other methods. The analysis was performed on a total of 56,898 single particle mass spectra allowing the extraction of 10 factors, their temporal trends and size distributions, named CNO–COOH (cyanide, oxidized organic nitrogen and carboxylic acids), SUL (sulphate), NH4-OOA (ammonium and oxidized organic aerosol), NaCl, EC+ (elemental carbon positive fragments), OC-Arom (aromatic organic carbon), EC− (elemental carbon negative fragments), K (potassium), NIT (nitrate) and OC–CHNO (organic nitrogen). The 10 factor solution from single particle PMF analysis explained 45% of variance of the total dataset, but the factors are well defined from a chemical point of view. Different EC and OC components were separated: fresh EC (factor EC−) from aged EC (factor EC+) and different organic families (factors NH4-OOA, OC-Arom, OC–CHNO and CNO–COOH). A comparison was conducted between PMF, K-means cluster analysis and the ART-2a artificial neural network. K-means and ART-2a give broadly overlapping results (with 9 clusters, each describing the full composition of a particle type), while PMF, by effecting spectral deconvolution, was able to extract and separate the different chemical species contributing to particles, but loses some information on internal mixing. Relationships were also examined between the estimated volumes of ATOFMS PMF factors and species concentrations measured independently by GRAEGOR and AMS instruments, showing generally moderate to strong correlations. [Copyright &y& Elsevier]

Abstract: We present here a novel instrument for measuring surface–atmosphere exchange fluxes of ammonia. The instrument is the upgraded version of a recently developed near-infrared diode laser based photoacoustic ammonia concentration monitoring instrument, i.e. the original instrument is supplemented with two additional sampling lines, an appropriate gas handling system and an advanced software controlling gradient measurements. As a result of these developments, ammonia concentration can be measured simultaneously at three different heights above the ground and ammonia fluxes can be calculated from these data using the aerodynamic gradient method. The instrument operates fully automatically, requires minimal maintenance and has a temperature controlled, waterproof housing which makes it suitable for measurements even under harsh field conditions. Preliminary tests on stability and accuracy were carried out during two two-week field measurement campaigns, with the three sampling inlets being placed at the same height together with the inlet of a reference instrument. The readings of the three channels agreed well (with correlation coefficients above 0.96). Comparison to reference instruments showed good stability of the photoacoustic instrument, there was no measurable zero-drift or change in sensitivity during the tests. Flux measurements were carried out during a three-week field campaign in southern Scotland over fertilized grassland with reference to a wet-chemical AMANDA instrument in gradient configuration. Ammonia fluxes calculated from the data of the two instruments agreed well. Fluxes up to 2500 ng m−2 s−1 were observed after fertilization. The minimum detectable ammonia flux was calculated on the basis of “virtual ammonia fluxes”, from measurements carried out with all inlets at the same height and was found to be ±60 ng m−2 s−1 which ensures reliable measurements above intensively managed grasslands or agricultural fields. [Copyright &y& Elsevier]

Abstract: Little information is known about the behaviour of ultrafine particles (UFP) on a citywide scale. Total particle number flux, dominated by UFP, and other meteorological parameters were collected from tower sites in Manchester, London, Edinburgh and Gothenburg between 1999 and 2006 using the eddy covariance technique. Averaged diurnal cycles were produced for particle number flux, concentration, sensible heat flux, emission velocity, friction velocity, wind speed and temperature. UFP flux cycles showed clear diurnal trends which were linked to traffic activity and local sources. Wind sector analysis showed contributions to flux from local heavily urbanised areas. A simple parameterised model linking UFP flux to traffic activity, sensible heat and friction velocity above the city was produced. [Copyright &y& Elsevier]