Biomass Burning Markers Research Articles

Evidence for Cytotoxicity and Mitochondrial Dysfunction in Human Lung Cells Exposed to Biomass Burning Aerosol Constituents: Levoglucosan and 4-Nitrocatechol

Biomass burning (BB) emissions are one of the largest sources of carbonaceous aerosol, posing a significant risk as an airway irritant. Important BB markers include wood pyrolysis emissions, such as levoglucosan (LG) that is an anhydrous sugar bearing a six-carbon ring structure (i.e., 1,6-anhydro-β-D-glucopyranose). Atmospheric chemical aging of BB-derived aerosol (BBA) in the presence of nitrogen oxides (NOx) can yield nitro-aromatic compounds, including 4-nitrocatechol (4NC). There is building evidence that NOx-mediated chemical aging of BBA poses a more serious exposure effect than primary pyrolysis emissions. This study provides a comparative toxicological assessment following the exposure to important BBA marker compounds in human lung cells (i.e., A549 and BEAS-2B) to determine whether aromatic 4NC is more toxic than BBA-bound anhydrous carbohydrate (i.e., LG). We determined inhibitory concentration-50 (IC50) and examined reactive oxygen species (ROS) changes, mitochondrial dysfunction, and apoptosis induction in the two cell lines following exposure to LG and 4NC in a dose-response manner. In the BEAS-2B cells, estimated IC50 values for 4NC were 33 and 8.8 μg mL-1, and for LG were 2546 and ∼ 3 × 107 μg mL-1 at 24 h and 48 h of exposure, respectively. A549 cells exhibited a much higher IC50 value than BEAS-2B cells. LG exposures resulted in mitochondrial stress with viability inhibition, but cells recovered with increasing exposure time. 4NC exposures at 200 μg mL-1 resulted in the induction of apoptosis at 6 h. Mitochondrial dysfunction and ROS imbalance induced the intrinsic apoptotic pathway induction following 4NC exposures. While increased ROS is caused by LG exposure in lung cells, 4NC is a marker of concern during BB emissions, as we observed apoptosis and high mitochondrial ROS in both lung cells at atmospherically-relevant aerosol concentrations. It may be associated with higher airway or inhalation pathologies in higher BBA emissions, such as wildfires or during wood combustion.

Physicochemical Characterization of the Particulate Matter in New Jersey/New York City Area, Resulting from the Canadian Quebec Wildfires in June 2023.

The global increase in wildfires, primarily driven by climate change, significantly affects air quality and health. Wildfire-emitted particulate matter (WFPM) is linked to adverse health effects, yet the toxicological mechanisms are not fully understood given its physicochemical complexity and the lack of spatiotemporal exposure data. This study focuses on the physicochemical characterization of WFPM from a Canadian wildfire in June 2023, which affected over 100 million people in the US Northeast, particularly around New Jersey/New York. Aerosol systems were deployed to characterize WFPM during the 3 day event, revealing unprecedented mass concentrations mainly in the WFPM0.1 and WFPM0.1-2.5 size fractions. Peak WFPM2.5 concentrations reached 317 μg/m3, nearly 10 times the National Ambient Air Quality Standard (NAAQS) 24 h average limit. Chemical analysis showed a high organic-to-total carbon ratio (96%), consistent with brown carbon wildfires nanoparticles. Large concentrations of high-molecular-weight PAHs were found predominantly bound to WFPM0.1, with retene, a molecular marker of biomass burning and a known teratogen, being the most abundant (>70%). Computational modeling estimated a total lung deposition of 9.15 mg over 72 h, highlighting the health risks of WFPM, particularly due to its long-distance travel capability and impact on densely populated areas.

Specific biomass burning tracers in air pollution in Zagreb, Croatia

Biomass burning is considered a renewable energy source whose household usage is rapidly increasing throughout Europe, largely encouraged by the rising cost of other energy sources. With all the advantages that characterize such an energy source, there are several disadvantages mostly from the air quality standpoint, and consequently with regard to the influence it may have on human health and climate change. Considering the side effects of air pollution, it is important to identify the composition and sources of air pollutants precisely. This study investigated the presence of biomass combustion-specific tracers in the air of Zagreb, Croatia, a city affected by increased air pollution mostly during wintertime. Biomass burning markers in terms of anhydrosugars, namely levoglucosan, mannosan, and galactosan were monitored in particulate matter PM10. A sampling of PM10 particulate matter was conducted in parallel at measuring stations in the northern and southern part of the city during 30 days in each season in 2020. The results showed a significant seasonal difference in PM10 and anhydrosugar levels at both measuring stations with the same seasonal trend decreasing as follows: winter, autumn, spring, summer. Both PM10 and anhydrosugar concentrations were higher in the southern compared to the northern station. Average winter PM10 levels were 58 μg m−3 at the southern and 51 μg m−3 at the northern station, while average levoglucosan levels were 3.68 and 1.64 μg m−3 at the southern and northern stations, respectively. An average levoglucosan/PM10 contribution of 6.3 % was determined at the southern, and 3.2 % at the northern measuring station. The differences in contribution can be explained by areas more populated by households using biomass for residential heating, the dominant wind direction in the area, and influences from other districts, including long- or close-range transport. Linear regression indicated a weak correlation (R2 = 0.32) of anhydrosugars between the stations.

Molecular Characterization of Gaseous Organic Acids and Nitrogen‐Containing Compounds From Crop Straw and Wood Burning

AbstractBiomass burning serves as important sources of volatile organic compounds (VOCs), yet our understanding of the molecular characteristics of oxygenated volatile organic compounds (OVOCs) from fresh emissions remains limited. In this study, gaseous organic compounds in fresh smokes from burning typical Chinese crop straws and woods are measured using an iodide time‐of‐flight chemical ionization mass spectrometer. Approximately 750 molecular formulas are identified, with CHO compounds containing carbon, hydrogen and oxygen atoms accounting for 77%–95% of the total. C1–C3 organic acids and dicarboxylic acids dominate the total CHO signal intensities by 27%–48%, while well‐known molecular markers of biomass burning, such as monosaccharide, guaiacol and syringol derivatives, contribute 7%–17%. Notably, crop straw and wood burning emit a higher abundance of guaiacol than syringol derivatives by a factor of 5. Additionally, a variety of nitrogen‐containing compounds (mainly in the CHON group) is identified, including isocyanate, amide, amino acids, and pyridine. The mass spectral profiles of organic compounds are largely similar between crop straw and wood burning fuels, although wood burning produces higher contributions of compounds with carbon atoms numbers >10. The saturation concentrations of organic compounds are estimated using molecular formula‐based volatility parameterization, revealing that semi‐volatile and intermediate VOCs (S/intermediate volatility organic compounds (IVOCs)) predominate smoke releases by 35%–60% and 20%–43%, respectively, with only a small fraction of low‐volatility compounds. Given the widespread nature of biomass burning in winter China, our results may have significant implications for interpreting secondary organic aerosol formation through gas‐particle partitioning or aqueous‐phase reactions.

Australian Black summer smoke signal on Antarctic aerosol collected between New Zealand and the Ross sea

Open biomass burning (BB) events are a well-known primary aerosol source, resulting in the emission of significant amount of gaseous and particulate matter and affecting Earth's radiation budget. The 2019–2020 summer, known as “Australian Black Summer”, showed exceptional duration and intensity of seasonal wildfires, triggered by high temperatures and severe droughts. Since increasing megafires are predicted due to expected climate changes, it is critical to study the impact of BB aerosol on a large scale and evaluate related transport processes. In this study, five aerosol samples (total suspended particles with a diameter >1 μm) were collected during the XXXV Italian Expedition in Antarctica on board of the R/V Laura Bassi from 6th of January to February 16, 2020, along the sailing route from Lyttelton harbor (New Zealand) to Terra Nova Bay (Antarctica). Levoglucosan and its isomers have been analyzed as markers of BB, together with polycyclic aromatic hydrocarbons (PAHs), sucrose and alcohol sugars. Ionic species and carboxylic acids have been analyzed to support the identification of aerosol sources and its aging. Results showed high levoglucosan concentrations (325–1266 pg m−3) during the campaign, suggesting the widespread presence of smoke in the region, because of huge wildfire releases. Backward trajectories indicated the presence of long-range atmospheric transport from South America, probably carrying wildfires plume, in agreement with literature. Regional sources have been suggested for PAHs, particularly for 3–4 rings' compounds; monosaccharides, sucrose, arabitol, and mannitol were related to marine and biogenic contributions. In a warming climate scenario, more frequent and extensive wildfire episodes are expected in Australia, potentially altering albedo, aerosol radiative properties, and cloud interactions. Therefore, it is crucial to strengthens the investigations on the regional climatic effects of these events in Antarctica.

Characteristics of Atmospheric Pollutants in Paddy and Dry Field Regions: Analyzing the Oxidative Potential of Biomass Burning

This study aimed to identify the characteristics of atmospheric pollutants emitted by agricultural activities and to evaluate factors that may cause harm to human health. For the research, atmospheric pollutants were measured over the course of a year in representative rice farming and field crop farming areas in South Korea. The results confirmed that the characteristics of atmospheric pollutants in agricultural areas are influenced by the nature of agricultural activities. Specifically, when comparing rice paddies and field crop areas, during summer, the correlation between oxidative potential and levoglucosan—a marker for biomass burning—weakens due to less burning activity in the rice-growing season, leading to lower oxidative potential despite different PM2.5 across areas. The study also finds that methyl sulfonic acid, indicating marine influence, plays a big role in keeping oxidative potential low in summer. This suggests that the main causes of PM2.5-related health risks in the area are from biomass burning and external sources, with burning being a significant factor in increasing oxidative potential. Based on these results, it is hoped that measures can be taken in the future to reduce atmospheric pollutants in agricultural areas.

Biomass Combustion in Boiler: Environmental Monitoring of Sugar Markers and Pollutants

The need to use renewable sources and matrices with energy potential is widely recognized. The development of innovative technologies aimed at the improvement of energy conversion processes and reducing environmental impacts is currently receiving increasing attention from the scientific community and policymakers. The presence of sugars in airborne particle materials is attributed to biomass combustion. For this reason, these compounds are considered markers of biomass burning. The purpose of this work was to evaluate the emissions produced by agroforestry biomass burning (citrus pruning) by simultaneously sampling both stack emissions and atmospheric particulates in the area around a biomass boiler to understand the real contribution of biomass burning to atmospheric pollution. The combustion tests were carried out by comparing the processes with and without particulate abatement system to see how biomass combustion’s contribution to particulate emission can be controlled and reduced. During the tests, the focus was on particulate matter (PM) speciation in terms of sugar marker identification and determination. This study aims to increase knowledge to better understand the contribution of biomass plants to air pollution and differentiate it from the contributions of other sources, such as vehicular traffic or domestic heating.

Mass spectrometric analysis of unprecedented high levels of carbonaceous aerosol particles long-range transported from wildfires in the Siberian Arctic

Abstract. Wildfires in Siberia generate large amounts of aerosols, which may be transported over long distances and pose a threat to the sensitive ecosystem of the Arctic. Particulate matter (PM) of aged wildfire plumes originating from Yakutia in August 2021 was collected in Nadym and on Bely Island (both in northwestern Siberia). An advanced analysis of the chemical composition of aerosol particles was conducted through a multi-wavelength thermal–optical carbon analyzer (TOCA) coupled to resonance-enhanced multiphoton ionization time-of-flight mass spectrometry (REMPI-TOFMS) as well as through ultra-high-resolution Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS). In Nadym, concentrations of organic carbon (OC) and elemental carbon (EC) peaked at 100 and 40 µg m−3, respectively, associated with Angström absorption exponents for 405 and 808 nm (AAE405/808) between 1.5 and 3.3. The weekly average on Bely Island peaked at 8.9 µg m−3 of OC and 0.3 µg m−3 of EC and AAE405/808 close to unity. In particular, ambient aerosol in Nadym had a distinct biomass burning profile with pyrolysis products from carbohydrates, such as cellulose and hemicellulose, as well as lignin and resinoic acids. However, temporarily higher concentrations of five- and six-ring polycyclic aromatic hydrocarbons (PAHs), different from the PAH signature of biomass burning, suggest a contribution of regional gas flaring. FT-ICR MS with electrospray ionization (ESI) revealed a complex mixture of highly functionalized compounds, containing up to 20 oxygen atoms, as well as nitrogen- and sulfur-containing moieties. Concentrations of biomass burning markers on Bely Island were substantially lower than in Nadym, flanked by the appearance of unique compounds with higher oxygen content, higher molecular weight, and lower aromaticity. Back-trajectory analysis and satellite-derived aerosol optical depth suggested long-range transport of aerosol from the center of a Yakutian wildfire plume to Nadym and from the plume periphery to Bely Island. Owing to lower aerosol concentrations in the plume periphery than in its center, it is demonstrated how dilution affects the chemical plume composition during atmospheric aging.

Particulate matter from a tropical city in southeast Brazil: Impact of biomass burning on polycyclic aromatic compounds levels, health risks, and in vitro toxicity

In the context of a rising global temperature, biomass burning represents an increasing risk to human health, due to emissions of highly toxic substances such as polycyclic aromatic hydrocarbon (PAHs). Size-segregated particulate matter (PM) was collected in a region within the sugarcane belt of São Paulo state (Brazil), where biomass burning is still frequent, despite the phasing out of manual harvesting preceded by fire. The median of the total concentration of the 15 PAHs determined was 2.3 ± 1.8 ng m−3 (n = 19), where 63% of this content was in PM1.0. Concentrations of OPAHs and NPAHs were about an order of magnitude lower. PM2.5 collected in the dry season, when most of the fires occur, presented PAHs and OPAHs total concentrations three times higher than in the wet season, showing positive correlations with fire foci number and levoglucosan (a biomass burning marker). These results, added to the fact that biomass burning explained 65% of the data variance (PCA analysis), evidenced the importance of this practice as a source of PAHs and OPAHs to the regional atmosphere. Conversely, NPAHs appeared to be mainly derived from diesel-powered vehicles. The B[a]P equivalent concentration was estimated to be 4 times higher in the dry season than in the wet season, and was greatly increased during a local fire event. Cytotoxicity and genotoxicity of PM1.0 organic extracts were assessed using in vitro tests with human liver HepG2 cells. For both types of tests, significant toxicity was only observed for samples collected during the dry season. Persistent DNA damage that may have impaired the DNA repair system was also observed. The results indicated that there was a health risk associated with the air particulate mixture, mainly related to biomass burning, demonstrating the urgent need for better remediation actions to prevent the occurrence of burning events.

Chemically speciated air pollutant emissions from open burning of household solid waste from South Africa

Abstract. Open burning of household solid waste is a large source of air pollutants worldwide, especially in the Global South. However, waste burning emissions are either missing or have large uncertainties in local, regional, or global emission inventories due to limited emission factor (EF) and activity data. Detailed particulate matter (PM) chemical speciation data are even less available. This paper reports source profiles and EFs for PM2.5 species as well as acidic and alkali gases measured from laboratory combustion of 10 waste categories that represent open burning in South Africa. Carbonaceous materials contributed more than 70 % of PM2.5 mass. Elemental carbon (EC) was most abundant from flaming materials (e.g., plastic bags, textiles, and combined materials), and its climate forcing exceeded the corresponding CO2 emissions by a factor of 2–5. Chlorine had the highest EFs among elements measured by X-ray fluorescence (XRF) for all materials. Vegetation emissions showed high abundances of potassium, consistent with its use as a marker for biomass burning. Fresh PM2.5 emitted from waste burning appeared to be acidic. Moist vegetation and food discards had the highest hydrogen fluoride (HF) and PM fluoride EFs due to fluorine accumulation in plants, while burning rubber had the highest hydrogen chloride (HCl) and PM chloride EFs due to high chlorine content in the rubber. Plastic bottles, plastic bags, rubber, and food discards had the highest EFs for polycyclic aromatic hydrocarbons (PAHs) and nitro-PAHs as well as their associated toxicities. Distinct differences between odd and even carbon preferences were found for alkanes from biological and petroleum-based materials: dry vegetation, paper, textiles, and food discards show preference for the odd-numbered alkanes, while the opposite is true for plastic bottles, plastic bags, and rubber. As phthalates are used as plasticizers, their highest EFs were found for plastic bottles and bags, rubber, and combined materials. Data from this study will be useful for health and climate impact assessments, speciated emission inventories, source-oriented dispersion models, and receptor-based source apportionment.

Gas–particle partitioning of semivolatile organic compounds when wildfire smoke comes to town

Abstract. Wildfires have become an increasingly important source of organic gases and particulate matter in the western USA. A large fraction of organic particulate matter emitted in wildfires is semivolatile, and the oxidation of organic gases in smoke can form lower-volatility products that then condense on smoke particulates. In this research, we measured the gas- and particle-phase concentrations of semivolatile organic compounds (SVOCs) during the 2017 northern California wildfires in a downwind urban area, using semivolatile thermal desorption aerosol gas chromatography (SV-TAG), and measured SVOCs in a rural site affected by biomass burning using cTAG (comprehensive thermal desorption aerosol gas chromatography mass spectrometry) in Idaho in 2018. Commonly used biomass burning markers such as levoglucosan, mannosan, and nitrocatechols were found to stay predominantly in the particle phase, even when the ambient organic aerosol (OA) was relatively low. The phase partitioning of SVOCs is observed to be dependent on their saturation vapor pressure, while the equilibrium absorption model underpredicts the particle-phase fraction of most of the compounds measured. Wildfire organic aerosol enhanced the condensation of polar compounds into the particle phase but not some nonpolar compounds, such as polycyclic aromatic hydrocarbons.

Measurement report: A 1-year study to estimate maritime contributions to PM10 in a coastal area in northern France

Abstract. This work focuses on filling the knowledge gap associated with the contribution of natural and anthropogenic marine emissions to PM10 concentrations in northern France. For this purpose, a 1-year measurement and sampling campaign for PM10 has been conducted at a French coastal site situated at the Strait of Dover. The characterization of PM10 samples was performed considering major and trace elements, water-soluble ions, organic carbon (OC), elemental carbon (EC), and organic markers of biomass burning and primary biogenic emissions. Furthermore, the source apportionment of PM10 was achieved using the constrained weighted non-negative matrix factorization (CW-NMF) model. The annual average PM10 was 24.3 µg m−3, with six species contributing 69 % of its mass (NO3-, OC, SO42-, Cl−, Na+, and NH4+). The source apportionment of PM10 led to the identification of 9 sources. On average yearly, fresh and aged sea salts contributed 37 % of PM10, while secondary nitrate and sulfate contributed 42 %, biomass burning contributed 8 %, and heavy-fuel-oil (HFO) combustion from shipping emissions contributed almost 5 %. Additionally, monthly evolution of the sources' contribution evidenced different behaviors with high contributions of secondary nitrate and biomass burning during winter. In the summer season, 15-times-higher concentrations for HFO combustion (July compared to January) and the predominance of aged sea salts versus fresh sea salts were observed.The concentration-weighted trajectory model showed that the sources contributing more than 80 % of PM10 at Cap Gris-Nez are of regional and/or long-range origins, with the North Sea and the English Channel as hotspots for natural and anthropogenic marine emissions and Belgium, the Netherlands, and the west of Germany as hotspots for secondary inorganic aerosols.

Chemical evolution of primary and secondary biomass burning aerosols during daytime and nighttime

Abstract. Primary emissions from wood and pellet stoves were aged in an atmospheric simulation chamber under daytime and nighttime conditions. The aerosol was analyzed with online aerosol mass spectrometry and offline Fourier transform infrared spectroscopy (FTIR). Measurements using the two techniques agreed reasonably well in terms of the organic aerosol (OA) mass concentration, OA:OC trends, and concentrations of biomass burning markers – lignin-like compounds and anhydrosugars. Based on aerosol mass spectrometry, around 15 % of the primary organic aerosol (POA) mass underwent some form of transformation during daytime oxidation conditions after 6–10 h of atmospheric exposure. A lesser extent of transformation was observed during the nighttime oxidation. The decay of certain semi-volatile (e.g., levoglucosan) and less volatile (e.g., lignin-like) POA components was substantial during aging, highlighting the role of heterogeneous reactions and gas–particle partitioning. Lignin-like compounds were observed to degrade under both daytime and nighttime conditions, whereas anhydrosugars degraded only under daytime conditions. Among the marker mass fragments of primary biomass burning OA (bbPOA), heavy ones (higher m/z) were relatively more stable during aging. The biomass burning secondary OA (bbSOA) became more oxidized with continued aging and resembled that of aged atmospheric organic aerosols. The bbSOA formed during daytime oxidation was dominated by acids. Organonitrates were an important product of nighttime reactions in both humid and dry conditions. Our results underline the importance of changes to both the primary and secondary biomass burning aerosols during their atmospheric aging. Heavier fragments from aerosol mass spectrometry seldom used in atmospheric chemistry can be used as more stable tracers of bbPOA and, in combination with the established levoglucosan marker, can provide an indication of the extent of bbPOA aging.

Residual impacts of a wildland urban interface fire on urban particulate matter and dust: a study from the Marshall Fire

The impacts of wildfires along the wildland urban interface (WUI) on atmospheric particulate concentrations and composition are an understudied source of air pollution exposure. To assess the residual impacts of the 2021 Marshall Fire (Colorado), a wildfire that predominantly burned homes and other human-made materials, on homes within the fire perimeter that escaped the fire, we performed a combination of fine particulate matter (PM2.5) filter sampling and chemical analysis, indoor dust collection and chemical analysis, community scale PurpleAir PM2.5 analysis, and indoor particle number concentration measurements. Following the fire, the chemical speciation of dust collected in smoke-affected homes in the burned zone showed elevated concentrations of the biomass burning marker levoglucosan (medianlevo = 4147 ng g−1), EPA priority toxic polycyclic aromatic hydrocarbons (median Σ16PAH = 1859.3 ng g−1), and metals (median Σ20Metals = 34.6 mg g−1) when compared to samples collected in homes outside of the burn zone 6 months after the fire. As indoor dust particles are often resuspended and can become airborne, the enhanced concentration of hazardous metals and organics within dust samples may pose a threat to human health. Indoor airborne particulate organic carbon (median = 1.91 μg m−3), particulate elemental carbon (median = .02 μg m−3), and quantified semi-volatile organic species in PM2.5 were found in concentrations comparable to ambient air in urban areas across the USA. Particle number and size distribution analysis at a heavily instrumented supersite home located immediately next to the burned area showed indoor particulates in low concentrations (below 10 μg m−3) across various sizes of PM (12 nm–20 μm), but were elevated by resuspension from human activity, including cleaning.Graphical

Brown Coal and Logwood Combustion in a Modern Heating Appliance: The Impact of Combustion Quality and Fuel on Organic Aerosol Composition.

Residential heating with solid fuels is one of the major drivers for poor air quality in Central and Eastern Europe, and coal is still one of the major fuels in countries, such as Poland, the Czech Republic, and Hungary. In this work, emissions from a single-room heater fueled with brown coal briquettes (BCBs) and spruce logs (SLs) were analyzed for signatures of inorganic as well as semivolatile aromatic and low-volatile organic constituents. High variations in organic carbon (OC) emissions of BCB emissions, ranging from 5 to 22 mg MJ-1, were associated to variations in carbon monoxide (CO) emissions, ranging from 900 to 1900 mg MJ-1. Residential BCB combustion turned out to be an equally important source of levoglucosan, an established biomass burning marker, as spruce logwood combustion, but showed distinct higher ratios to manosan and galactosan. Signatures of polycyclic aromatic hydrocarbons emitted by BCB combustion exhibited defunctionalization and desubstitution with increasing combustion quality. Lastly, the concept of island and archipelago structural motifs adapted from petroleomics is used to describe the fraction low-volatile organic compounds in particulate emissions, where a transition from archipelago to island motifs in relation with decreasing CO emissions was observed in BCB emissions, while emissions from SL combustion exhibited the island motif.

Characterization of organic aerosols at the Natura 2000 remote environment of Sanabria Lake (Spain): Evaluating the influence of African dust and regional biomass burning smoke

This work presents a thorough analysis of PM10 speciated organic composition at Sanabria Lake Natural Park, a rural remote area in NW-Spain, including diacids, hydroxy and poliacids, fatty acids, alkenoic acids, sugars, sugar alcohols, n-alkanes, PAHs, quinones, hopanes, tracers of biomass burning, and biogenic secondary organic aerosol (BSOA) from isoprene and α-pinene.PM10 ambient concentrations at Sanabria (mean value of 12.2 μg m−3) were within the typical range registered in regional-background air quality monitoring stations in Spain. However, the occurrence of African dust outbreaks and biomass burning events produced significant increases in the PM10 levels at this monitoring site (daily mean levels of 29.2 μg m−3 and 13.7 μg m−3, respectively).Major organic compounds were levoglucosan, sacharides and 2-methyltetrols, markers for biomass burning, soil dust and BSOA respectively.SOA contributed more than 53% of the total measured organics in summer Samples with high levels of SOA include most of the African dust events, suggesting that African dust might promote the formation of oxygenated species such as SOA derivatives in this area. This contribution decreased to a 14% in winter. Biomass burning tracers represented 37% of the analysed organic pollutants in winter, indicating that this is the main source of organic compounds in the colder seasons, mainly due to the influence of regional biomass burning events and the use of biomass as fuel in domestic heating. Hence, the fact that African dust outbreaks and biomass burning events are likely to become increasingly frequent in the context of climate change makes this type of analysis particularly relevant for assessing their impact on natural protected areas.

Spatial distribution and temporal variation of biomass burning and surface black carbon concentrations during summer (2015‒2021) in India.

Historical biomass burning in summer season (April‒June, during 2015‒2021) was assessed by studying active fire spot data recorded by the Visible Infrared Imaging Radiometer Suite (VIIRS) aboard NASA/NOAASuomi NPP satellite and mapping the same over Indian landmass. The fire spots often formed regional clusters and most profusely covered the states of Odisha, Chhattisgarh, Andhra Pradesh, Telengana, Madhya Pradesh, Maharashtra, Jharkhand, Karnataka, Punjab, Uttar Pradesh, Haryana, Gujarat, Tamil Nadu, Manipur, Nagaland, and Mizoram during April but their number decreased conspicuously in May and further in June. Forward movements of air masses potentially carrying fire-induced air pollutants from five principal fire cluster regions (northern, south eastern, western, north-eastern, and central) of India during April and May in2021 were traced by 6-day forward airtrajectory modelling. It was observed that many parts of India were the recipients of air coming from the above principal fire clusters. In each year, the surface mass concentration of black carbon (BC), one of the most prominent markers of biomass burning, was higher in April over May and June in the affected regions, commensurate with the most active period of fire. The BC surface mass concentrations progressively declined thereafter in May and June with decreasing number of active fire spots along with declining average monthly height of the planetary boundary layer (PBL), indicating integral connection of surface BC levels with biomass burning. The study suggests that in spite of more favourable meteorological conditions in summer, extensivebiomass burning may have hada crucial role to play in perturbing local and regional air quality over India by generatingBC and other air pollutants.

Source apportionment of VOCs, IVOCs and SVOCs by positive matrix factorization in suburban Livermore, California

Abstract. Gas- and particle-phase molecular markers provide highly specific information about the sources and atmospheric processes that contribute to air pollution. In urban areas, major sources of pollution are changing as regulation selectively mitigates some pollution sources and climate change impacts the surrounding environment. In this study, a comprehensive thermal desorption aerosol gas chromatograph (cTAG) was used to measure volatile, intermediate-volatility and semivolatile molecular markers every other hour over a 10 d period from 11 to 21 April 2018 in suburban Livermore, California. Source apportionment via positive matrix factorization (PMF) was performed to identify major sources of pollution. The PMF analysis identified 13 components, including emissions from gasoline, consumer products, biomass burning, secondary oxidation, aged regional transport and several factors associated with single compounds or specific events with unique compositions. The gasoline factor had a distinct morning peak in concentration but lacked a corresponding evening peak, suggesting commute-related traffic emissions are dominated by cold starts in residential areas. More monoterpene and monoterpenoid mass was assigned to consumer product emissions than biogenic sources, underscoring the increasing importance of volatile chemical products to urban emissions. Daytime isoprene concentrations were controlled by biogenic sunlight- and temperature-dependent processes, mediated by strong midday mixing, but gasoline was found to be the dominant and likely only source of isoprene at night. Biomass burning markers indicated residential wood burning activity remained an important pollution source even in the springtime. This study demonstrates that specific high-time-resolution molecular marker measurements across a wide range of volatility enable more comprehensive pollution source profiles than a narrower volatility range would allow.

Different roles of primary and secondary sources in reducing PM2.5: Insights from molecular markers in Pearl River Delta, South China

It is essential to understand the variations of PM2.5 sources under different pollution levels for improving air quality. The Pearl River Delta (PRD) was one of the most polluted areas by PM2.5 in China and is now the advanced region with the most significant improvement in PM2.5 pollution. In the year that regional PM2.5 over the PRD met the National Air Quality Standard (35 μg m−3) for the first time, we conducted a year-round PM2.5 sampling campaign at 9 sites and measured organic tracers for primary and secondary sources as well as water-soluble ions and heavy metals. Based on the daily PM2.5 concentrations in these samples, we divided the data into four pollution levels: Polluted (PM2.5 > 75 μg m−3), Moderate (75 μg m−3 > PM2.5 > 35 μg m−3), Clean (35 μg m−3 > PM2.5 > 25 μg m−3), and Good (PM2.5 < 25 μg m−3). The average concentrations of PM2.5 under the Polluted, Moderate, Clean, and Good levels were 91.8 ± 18.8 μg m−3, 47.6 ± 10.7 μg m−3, 30.1 ± 3.22 μg m−3, and 17.3 ± 4.67 μg m−3, respectively. Under different pollution levels, the reduction rates of molecular markers for biomass burning, vehicle exhaust, anthropogenic secondary organic aerosol (ASOA), nitrate aerosol, and industrial emission were rapider than or close to those of PM2.5, implying that the control measures on these sources were effective in the PRD. Based on the chemical characterization of specific molecular markers and source apportionment by the Positive Matrix Factorization model, we found that PM2.5 over the PRD predominantly originated from anthropogenic sources (82% on average), and the contributions of primary sources (53% on average) were slightly higher than those of secondary sources (41% on average). Compared with the Polluted days, the Good days had large decreases in anthropogenic sources of PM2.5 with significant reductions in both primary (industrial emission, vehicle exhaust, and biomass burning) and secondary (secondary nitrate, secondary sulfate and ASOA) contributions. The declines of PM2.5 from Polluted to Moderate and Clean to Good were mainly due to the reductions of primary (69% on average) and secondary (58% on average) sources, respectively. Our findings highlight the different roles of reducing primary and secondary aerosols in improving PM2.5 air quality under different pollution levels.

Spatially calibrating polycyclic aromatic hydrocarbons (PAHs) as proxies of area burned by vegetation fires: Insights from comparisons of historical data and sedimentary PAH fluxes

Many regions worldwide have experienced increasing wildfire activity in recent years and climate changes are predicted to result in more frequent and severe fires. Reconstruction of past fire activity offers paleoenvironmental context for modern and future burning. Pyrogenic polycyclic aromatic hydrocarbons (PAHs) have been increasingly used as a molecular biomarker for fire occurrence in the paleorecord and offer opportunity for nuanced reconstructions of fire characteristics. A suite of PAHs is produced during combustion, and the emission amount and assemblage is influenced by many variables including fuel type, fire temperature, and oxygen availability. Despite recent advances in understanding the controls and taphonomy of these biomass burning markers, the spatial scale of this proxy is unknown. In this paper, measurements of PAH fluxes preserved in a lake sediment archive from the Sierra Nevada, California were compared with a historical geographic information system (GIS) dataset of area burned up to 150 km distance from the lake to determine the spatial scales for which these biomarkers are reliable proxies of biomass burning. The PAH fluxes in the Swamp Lake sediments record a change in the relative anthropogenic and pyrogenic sourcing of PAHs. Anthropogenic pollution sources could explain why some PAHs (fluoranthene (Fl), pyrene (Py), benz[a]anthracene (BaA), retene (Ret), benzo[a]pyrene (BaP), dibenzo[a,h]anthracene (DA) and ideno[1,2,3-cd]pyrene (IP)) did not correlate with area burned within 150 km. This indicates that individual PAHs may have different efficacies in recording area burned and be more susceptible to masking of fire signals by pollution sources. Despite these complications, we find that the PAHs naphthalene (Na), acenaphthene (Ace), fluorene (F), and anthracene (An) are reliable local proxies of area burned (within 40 km), whereas the PAHs phenanthrene (Phe), chrysene (Ch), benzo[b]fluoranthene (BbF), benzo[k]fluoranthene (BkF), and benzo[g,h,i]perylene (Bghi) are both reliable local (within 36 km) as well as more regional (as much as 75 km for phenanthrene (Phe), chrysene (Ch), and benzo[g,h,i]perylene (Bghi) or 150 km for benzo[b]fluoranthene (BbF) and benzo[k]fluoranthene (BkF)) area burned proxies. Comparisons of PAH fluxes with charcoal accumulation rates in the same sediments suggest that pyrogenic particulate transport modulates low to mid-molecular weight PAHs via adsorption. Overall, the results show that PAH records integrate a combination of spatial signals of area burned and measurement of individual PAHs may enable cross-scale paleofire reconstructions.