To elucidate the molecular composition and sources of organic aerosols in Central Asia, carbonaceous compounds, major ions, and 15 organic molecular tracers of total suspended particulates (TSP) were analyzed from September 2018 to August 2019 in Dushanbe, Tajikistan. Extremely high TSP concentrations (annual mean ± std: 211 ± 131 μg m⁻³) were observed, particularly during summer (seasonal mean ± std: 333 ± 183 μg m⁻³). Organic carbon (OC: 11.9 ± 7.0 μg m⁻³) and elemental carbon (EC: 5.1 ± 2.2 μg m⁻³) exhibited distinct seasonal variations from TSP, with the highest values occurring in winter. A high concentration of Ca²⁺ was observed (11.9 ± 9.2 μg m⁻³), accounting for 50.8% of the total ions and reflecting the considerable influence of dust on aerosols. Among the measured organic molecular tracers, levoglucosan was the predominant compound (632 ± 770 ng m⁻³), and its concentration correlated significantly with OC and EC during the study period. These findings highlight biomass burning (BB) as an important contributor to the particulate air pollution in Dushanbe. High ratios of levoglucosan to mannosan, and syringic acid to vanillic acid suggest that mixed hardwood and herbaceous plants were the main burning materials in the area, with softwood being a minor one. According to the diagnostic tracer ratio, OC derived from BB constituted a large fraction of the primary OC (POC) in ambient aerosols, accounting for an annual mean of nearly 30% and reaching 63% in winter. The annual contribution of fungal spores to POC was 10%, with a maximum of 16% in spring. Measurements of plant debris, accounting for 3% of POC, divulged that these have the same variation as fungal spores.

Biomass burning (BB) is one of the largest sources of carbonaceous aerosols with adverse impacts on air quality, visibility, health and climate. BB emits a few specific aromatic acids (p-hydroxybenzoic, vanillic, syringic and dehydroabietic acids) which have been widely used as key indicators for source identification of BB-derived carbonaceous aerosols in various environmental matrices. In addition, measurement of p-hydroxybenzoic and vanillic acids in snow and ice cores have revealed the historical records of the fire emissions. Despite their uniqueness and importance as tracers, our current understanding of analytical methods, concentrations, diagnostic ratios and degradation processes are rather limited and scattered in literature. In this review paper, firstly we have summarized the most established methods and protocols for the measurement of these aromatic acids in aerosols and ice cores. Secondly, we have highlighted the geographical variability in the abundances of these acids, their diagnostic ratios and degradation processes in the environments. The review of the existing data indicates that the concentrations of aromatic acids in aerosols vary greatly with locations worldwide, typically more abundant in urban atmosphere where biomass fuels are commonly used for residential heating and/or cooking purposes. In contrast, their concentrations are lowest in the polar regions which are avoid of localized emissions and largely influenced by long-range transport. The diagnostic ratios among aromatic acids can be used as good indicators for the relative amounts and types of biomass (e.g. hardwood, softwood and herbaceous plants) as well as photochemical oxidation processes. Although studies suggest that the degradation processes of the aromatic acids may be controlled by light, pH and hygroscopicity, a more careful investigation, including closed chamber studies, is highly appreciated.

Cryoconite is a dark, dusty aggregate of mineral particles, organic matter, and microorganisms transported by wind and deposited on glacier surfaces. It can accelerate glacier melting and alter glacier mass balances by reducing the surface albedo of glaciers. Biomass burning in the Tibetan Plateau, especially in the glacier cryoconites, is poorly understood. Retene, levoglucosan, mannosan and galactosan can be generated by the local fires or transported from the biomass burning regions over long distances. In the present study, we analyzed these four molecular markers in cryoconites of seven glaciers from the northern to southern Tibetan Plateau. The highest levels of levoglucosan and retene were found in cryoconites of the Yulong Snow Mountain and Tienshan glaciers with 171.4 ± 159.4 ng g⁻¹ and 47.0 ± 10.5 ng g⁻¹ dry weight (d.w.), respectively. The Muztag glacier in the central Tibetan Plateau contained the lowest levels of levoglucosan and retene with mean values of 59.8 ng g⁻¹ and 0.4 ± 0.1 ng g⁻¹ d.w., respectively. In addition, the vegetation changes and the ratios of levoglucosan to mannosan and retene indicate that combustion of conifers significantly contributes to biomass burning of the cryoconites in the Yulong Snow Mountain and Tienshan glacier. Conversely, biomass burning tracers in cryoconites of Dongkemadi, Yuzhufeng, Muztag, Qiyi and Laohugou glaciers are derived from the combustion of different types of biomass including softwood, hardwood and grass.

Biomass burning tracers have been widely used to identify biomass burning types, but such tools can sometimes cause large uncertainties in the source attribution studies of PM₂.₅ (particles with an aerodynamic diameter of smaller than 2.5 μm). To quantify the relative importance of the major biomass burning tracers in PM₂.₅ released from biofuels combusted in the North China Plain, combustion experiments under the smoldering and flaming combustion conditions were conducted using nine types of typical household biofuels including two types of agricultural wastes, five types of hardwoods, one softwood, and one mixed wood briquette. PM₂.₅ samples were collected from the combustion experiments and source profiles of PM₂.₅ were thus determined for various biofuels under the two different combustion conditions. Carbonaceous species including organic carbon (OC) and elemental carbon (EC) were the major chemical components of the PM₂.₅ released from combustion of all the tested biofuels, with mass fractions of 37–45% and 4–7% under the smoldering condition and 11–25% and 7–29% under the flaming condition, respectively. Higher mass fractions of water-soluble inorganic ions (WSIIs, e.g., K⁺ and Cl⁻) in PM₂.₅ were observed under the flaming than smoldering combustion condition, while anhydrosugars (levoglucosan (LG) and mannosan (MN)) presented in an opposite pattern. The average LG/MN ratio in PM₂.₅ changed significantly with biofuel type (20–55 for agricultural wastes, 10–22 for hardwoods (except elm) and 3–6 for softwood), but varied little with combustion condition. In contrast, the K⁺/LG ratio in PM₂.₅ varied significantly between smoldering (<0.2) and flaming (>0.6) combustion conditions for all the biofuel types except softwood. Results from this study suggested that the ratio LG/MN was the best tracer for identifying the biofuel types and the ratio K⁺/LG is suitable for identifying the combustion conditions in this region.

Fine particles (PM2.5) samples, collected at Weizhou Island over the Gulf of Tonkin on a daytime and nighttime basis in the spring of 2015, were analyzed for primary and secondary organic tracers, together with organic carbon (OC), elemental carbon (EC), and stable carbon isotopic composition (δ13C) of total carbon (TC). Five organic compound classes, including saccharides, lignin/resin products, fatty acids, biogenic SOA tracers and phthalic acids, were quantified by gas chromatography/mass spectrometry (GC/MS). Levoglucosan was the most abundant organic species, indicating that the sampling site was under strong influence of biomass burning. Based on the tracer-based methods, the biomass-burning-derived fraction was estimated to be the dominant contributor to aerosol OC, accounting for 15.7% ± 11.1% and 22.2% ± 17.4% of OC in daytime and nighttime samples, respectively. In two episodes E1 and E2, organic aerosols characterized by elevated concentrations of levoglucosan as well as its isomers, sugar compounds, lignin products, high molecular weight (HMW) fatty acids and β-caryophyllinic acid, were attributed to the influence of intensive biomass burning in the northern Southeast Asia (SEA). However, the discrepancies in the ratios of levoglucosan to mannosan (L/M) and OC (L/OC) as well as the δ13C values suggest the type of biomass burning and the sources of organic aerosols in E1 and E2 were different. Hardwood and/or C4 plants were the major burning materials in E1, while burning of softwood and/or C3 plants played important role in E2. Furthermore, more complex sources and enhanced secondary contribution were found to play a part in organic aerosols in E2. This study highlights the significant influence of springtime biomass burning in the northern SEA to the organic molecular compositions of marine aerosols over the Gulf of Tonkin.

Reconstructions of 250 years historical inputs of two distinct types of black carbon (soot/graphitic black carbon (GBC) and char-BC) were conducted on sediment cores from two basins of the Puget Sound, WA. Signatures of polycyclic aromatic hydrocarbons (PAHs) were also used to support the historical reconstructions of BC to this system. Down-core maxima in GBC and combustion-derived PAHs occurred in the 1940s in the cores from the Puget Sound Main Basin, whereas in Hood Canal such peak was observed in the 1970s, showing basin-specific differences in inputs of combustion byproducts. This system showed relatively higher inputs from softwood combustion than the northeastern U.S. The historical variations in char-BC concentrations were consistent with shifts in climate indices, suggesting an influence of climate oscillations on wildfire events. Environmental loading of combustion byproducts thus appears as a complex function of urbanization, fuel usage, combustion technology, environmental policies, and climate conditions.

Three monosaccharide anhydrides levoglucosan, mannosan and galactosan were detected in winter snowfall samples of 2012 in urban Beijing. Concentrations of three isomers vary from 0.15 to 54.43ngmL−1, with an average value of 10.49ngmL−1. Levoglucosan is the most abundant component. Winter snowfalls are contaminated by biomass burning emissions seriously in urban Beijing. The main sources are softwood and crop residue burnings around Beijing from late autumn to early winter, while long-range transport of biomass burning emissions contribute more during the late winter. Concentrations of monosaccharide anhydrides in snowfall samples may be affected by both topography and the meteorological conditions around urban Beijing.

PM1 aerosol, collected during winter campaign in urban area situated close to a large automobile factory, was analysed on content of selected organic compounds, namely monosaccharide anhydrides, diterpenoids (including retene and resin acids), n-alkanes (including pristane and phytane), polycyclic aromatic hydrocarbons (including picene), monosaccharides, disaccharides, polyols, hopanes and steranes.Monosaccharide anhydrides (MAs, markers for biomass burning) were the most abundant organic compounds (the mean sum of concentration of 513 ng m−3). The sum of MAs constituted in average 70.0% of the mass of all analysed organic compounds and 1.91% of the PM1 mass. Diterpenoids, markers for softwood combustion, were the second most abundant analysed organic compounds (the mean concentration of 119 ng m−3). The mean concentrations of other studied organic compounds were smaller, namely saccharides 31.6 ng m−3, n-alkanes, including isoprenoids 35.3 ng m−3, PAHs 15.6 ng m−3 and hopanes, including one sterane 1.54 ng m−3.Combustion of solid fuels (coal and wood) for household heating was the dominant emission source of carbonaceous aerosols sampled during the campaign. The composition of aerosols collected in the studied locality was affected by local emissions and also by regional transport of polluted air from small villages nearby Mladá Boleslav.Two unit risks (WHO and CalEPA) were applied for the estimation of carcinogenic risk of PAHs exposure. The computed lifetime cancer risk at the studied locality during the campaign period was 1.93 × 10−4 (WHO unit risk) and 2.43 × 10−6 (CalEPA unit risk) on average. However, the real cancer risk for the lifetime exposure (70 years) is lower at the studied locality because our measurement lasted only 2 weeks in winter when the concentrations of PAHs were higher than in other seasons of the year.

Forest soils (mainly soil organic carbon) play an important role in the retention of nitrogen and mercury, and loss of the forest floor during wildfires can stimulate N and Hg losses. In this paper, we investigate long-term impacts of forest fire on soil N and Hg concentrations at Acadia National Park (ANP) in Maine. Acadia National Park experienced a severe fire in 1947. Within the national park, Hadlock Brook watershed was left unburned, whereas most of Cadillac Brook watershed was intensely burned, with substantial loss of the forest floor. Post-fire regeneration in Cadillac was mostly as hardwood species, whereas vegetation in Hadlock remained predominantly softwood. We sampled soils in both watersheds in 2015, approximately 70 years after the fire. The soils were analyzed for total carbon (TC), total nitrogen (TN), total mercury (THg), and methylmercury (MeHg) content. Compared to Hadlock, Cadillac soils had ~ 50% lower TC, ~ 40% lower TN, and ~ 50% lower THg content, reflecting the loss of forest floor 70 years ago. Methylmercury concentrations in Cadillac were approximately 2 times the concentrations in Hadlock, indicating that conditions were more conducive to methylation, potentially due to differences in forest type. Long-term comparisons of stream DOC, NO₃⁻, and THg concentrations between the two watersheds demonstrated that concentrations were significantly lower in Cadillac Brook, reflecting greater retention in Cadillac and a legacy of lower atmospheric deposition in the hardwood as compared to softwood watershed. This study provides insights on the multi-decadal recovery from a stand-replacing disturbance and underscores the persistence of altered soil biogeochemistry.

Annually, sawmills and other wood-processing factories generate a significant amount of scrap materials which are sent to landfills or incinerated. The amount of residue generated in Australia annually is estimated at 200,000 tonnes. A research project conducted at RMIT University explored utilizing these waste materials as particleboard furnish. The research team has now established a methodology for making particleboard in the laboratory using 100% hardwood sawmill residues, developing a particleboard product made in the laboratory which has acceptable mechanical properties and density profiles in accordance with the Australian Standards. However, this board product has some perceived issues which have been hindering ready commercial uptake. The current product requires a 10% higher resin load, has a 10% higher board density, and requires 10% longer pressing times compared to normal softwood particleboard. The paper presents an analysis of the current production process of particleboard to investigate the economic feasibility of particleboard production using hardwood sawmill residues. A major challenge in the analysis is converting the environmental benefit of utilizing large quantities of sawmill residue to a monetary term. Investigation of the global impact of particleboard by considering emission of carbon dioxide to the atmosphere is also included. A comparison is presented between different methods of disposing wood residues to understand the environmental benefit of using hardwood residue in particleboard.