Influence Of Biomass Burning Research Articles

Linking trace gas measurements and molecular tracers of organic matter in aerosols for identification of ecosystem sources and types of wildfires in Central Siberia

Summer 2012 was one of the extreme wildfire years in Siberia. At the surface air monitoring station “ZOTTO” (60°48'N, 89°21'E, 114 m a.s.l.) in Central Siberia we observed biomass burning (BB) influence on the ongoing atmospheric measurements within more than 50 % of the time in June-July 2012 that indicates a 30 times greater wildfire signal compared to previously reported ordinary biomass burning signature for the study area. While previous studies thoroughly estimated a relative input of BB into aerosol composition (i.e. size distribution, physical and optical parameters etc.) at ZOTTO, in this paper we characterize the source apportionment of the smoke aerosols with molecular tracer techniques from large-scale wildfires occurred in 2012 in the two prevailing types of Central Siberian ecosystems: complexes of pine forests and bogs and dark coniferous forests. Wildfires in the selected ecosystems are highly differed by their combustion phase (flaming/smoldering), the type of fire (crown/ground), biomass fuel, and nature of soil that greatly determines the smoke particle composition. Anhydrosugars (levoglucosan and its isomers) and lignin phenols taken as indicators of the sources and the state of particulate matter (PM) inputs in the specific fire plumes were used as powerful tools to compare wildfires in different environmental conditions and follow the role and contribution of different sources of terrestrial organic matter in the transport of BB pollutants into the pristine atmosphere of boreal zone in Central Siberia.

Characterization of submicron aerosols influenced by biomass burning at a site in the Sichuan Basin, southwestern China

Abstract. Severe air pollution in Asia is often the consequence of a combination of large anthropogenic emissions and adverse synoptic conditions. However, limited studies on aerosols have been conducted under high emission intensity and under unique geographical and meteorological conditions. In this study, an Aerodyne high-resolution time-of-flight aerosol mass spectrometry (HR-ToF-AMS) and other state-of-the-art instruments were utilized at a suburban site, Ziyang, in the Sichuan Basin during December 2012 to January 2013. The chemical compositions of atmospheric submicron aerosols (PM1) were determined, the sources of organic aerosols (OA) were apportioned, and the aerosol secondary formation and aging process were explored as well. Due to high humidity and static air, PM1 maintained a relatively stable level during the whole campaign, with the mean concentration of 59.7 ± 24.1 µg m−3. OA was the most abundant component (36 %) in PM1, characterized by a relatively high oxidation state. Positive matrix factorization analysis was applied to the high-resolution organic mass spectral matrix, which deconvolved OA mass spectra into four factors: low-volatility (LV-OOA) and semivolatile oxygenated OA (SV-OOA), biomass burning (BBOA) and hydrocarbon-like OA (HOA). OOA (sum of LV-OOA and SV-OOA) dominated OA as high as 71 %. In total, secondary inorganic and organic formation contributed 76 % of PM1. Secondary inorganic species correlated well (Pearson r = 0.415–0.555, p < 0.01) with relative humidity (RH), suggesting the humid air can favor the formation of secondary inorganic aerosols. As the photochemical age of OA increased with higher oxidation state, secondary organic aerosol formation contributed more to OA. The slope of OOA against Ox( = O3+NO2) steepened with the increase of RH, implying that, besides the photochemical transformation, the aqueous-phase oxidation was also an important pathway of the OOA formation. Primary emissions, especially biomass burning, resulted in high concentration and proportion of black carbon (BC) in PM1. During the episode obviously influenced by primary emissions, the contributions of BBOA to OA (26 %) and PM1 (11 %) were much higher than those (10–17 %, 4–7 %) in the clean and other polluted episodes, highlighting the significant influence of biomass burning.

Chemical composition of aerosol in São Paulo, Brazil: influence of the transport of pollutants

Sao Paulo is a Latin American megacity impacted by heavy traffic emissions and also affected by biomass burning and biogenic emissions. To better understand the sources of pollution during a highly polluted period, PM10 samples were collected in an intensive campaign in 2013. The concentrations of particulate matter, organic carbon (OC), elemental carbon (EC), biomass burning tracers (levoglucosan, mannosan, and galactosan), water-soluble ions, and polycyclic aromatic hydrocarbons (PAHs) were determined to identify the main sources affecting the air quality. The PAHs results were compared to an intensive campaign done in 2012. Backward air masses trajectories were used in other to investigate the influence of remote sources. The average benzo[a]pyrene equivalent index (BaPE) values represented a higher cancer risk in 2013 samples than in 2012; the diagnostic ratios indicated vehicular emissions for both campaigns but fresher particles emission for 2013 campaign. During the 2013 campaign, the samples presented good correlations between OC and EC with monosaccharides, suggesting an influence of biomass burning on the carbonaceous species. Levoglucosan to mannosan ratio indicated the influence of sugarcane burning; the backward air masses trajectories suggested transport of aerosol from the sugarcane production region in 60 % of the sampling days.

The contributions of biomass burning to primary and secondary organics: A case study in Pearl River Delta (PRD), China

Synchronized online measurements of gas- and particle- phase organics including non-methane hydrocarbons (NMHCs), oxygenated volatile organic compounds (OVOCs) and submicron organic matters (OM) were conducted in November 2010 at Heshan, Guangdong provincial supersite, China. Several biomass burning events were identified by using acetonitrile as a tracer, and enhancement ratios (EnRs) of organics to carbon monoxide (CO) obtained from this work generally agree with those from rice straw burning in previous studies. The influences of biomass burning on NMHCs, OVOCs and OM were explored by comparing biomass burning impacted plumes (BB plumes) and non-biomass burning plumes (non-BB plumes). A photochemical age-based parameterization method was used to characterize primary emission and chemical behavior of those three organic groups. The emission ratios (EmRs) of NMHCs, OVOCs and OM to CO increased by 27–71%, 34–55% and 67% in BB plumes, respectively, in comparison with non-BB plumes. The estimated formation rate of secondary organic aerosol (SOA) in BB plumes was found to be 24% faster than non-BB plumes. By applying the above emission ratios to the whole PRD, the annual emissions of VOCs and OM from open burning of crop residues would be 56.4 and 3.8Gg in 2010 in PRD, respectively.

Chemical characterization of carbonaceous carbon from industrial and semi urban site of eastern India.

Rigorous campaign was carried out from July 2013 to June 2014 at the remote and industrial site (Adityapur and Seraikela Kharsawan) in the eastern India aiming to identify and quantify the changes of aerosol chemical composition in the presence of industrial and biomass burning influence. The 24-h PM10 filter samples were analyzed by mass, carbonaceous species, organic ions. The results suggested that the average PM10 concentrations were 165 ± 43.93, 141 ± 30.86 μg/m3 in industrial and remote site respectively. Secondary organic ions (SOC) were the dominant pollutants of PM10. Total carbon was a significant component explaining above 15 % of PM10. The annual average mass concentration of EC, OC, WSOC 26.39 ± 4.56, 5.11 ± 1.82, 18.56 ± 5.30 and 16.27 ± 5.75, 7.70 ± 2.1, 9.65 ± 1.92 µg/m3, OC/EC, WSOC/OC 5.29 ± 1.08, 0.71 ± 0.17 and 2.34 ± 0.75, 0.67 ± 0.16) of industrial and remote site were respectively; and OC/EC particularly in industrial site it reached the highest 5.29 ± 1.08 which demonstrated that SOC should be a significant composition of PM10. The mass fraction of the highlighted species varies seasonally, resulting the air mass trajectories and corresponding cause severe strength. Based on exact mass concentration ratios of EC/OC, WSOC/OC, we predicted that industries and biofuel/biomass burning are a major source of atmospheric aerosols in the eastern part of India. This study provides the scientific baseline data of carbonaceous aerosols for eastern Jharkhand, India.

Biomass-burning impact on CCN number, hygroscopicity and cloud formation during summertime in the eastern Mediterranean

Abstract. This study investigates the concentration, cloud condensation nuclei (CCN) activity and hygroscopic properties of particles influenced by biomass burning in the eastern Mediterranean and their impacts on cloud droplet formation. Air masses sampled were subject to a range of atmospheric processing (several hours up to 3 days). Values of the hygroscopicity parameter, κ, were derived from CCN measurements and a Hygroscopic Tandem Differential Mobility Analyzer (HTDMA). An Aerosol Chemical Speciation Monitor (ACSM) was also used to determine the chemical composition and mass concentration of non-refractory components of the submicron aerosol fraction. During fire events, the increased organic content (and lower inorganic fraction) of the aerosol decreases the values of κ, for all particle sizes. Particle sizes smaller than 80 nm exhibited considerable chemical dispersion (where hygroscopicity varied up to 100 % for particles of same size); larger particles, however, exhibited considerably less dispersion owing to the effects of condensational growth and cloud processing. ACSM measurements indicate that the bulk composition reflects the hygroscopicity and chemical nature of the largest particles (having a diameter of ∼ 100 nm at dry conditions) sampled. Based on positive matrix factorization (PMF) analysis of the organic ACSM spectra, CCN concentrations follow a similar trend as the biomass-burning organic aerosol (BBOA) component, with the former being enhanced between 65 and 150 % (for supersaturations ranging between 0.2 and 0.7 %) with the arrival of the smoke plumes. Using multilinear regression of the PMF factors (BBOA, OOA-BB and OOA) and the observed hygroscopicity parameter, the inferred hygroscopicity of the oxygenated organic aerosol components is determined. We find that the transformation of freshly emitted biomass burning (BBOA) to more oxidized organic aerosol (OOA-BB) can result in a 2-fold increase of the inferred organic hygroscopicity; about 10 % of the total aerosol hygroscopicity is related to the two biomass-burning components (BBOA and OOA-BB), which in turn contribute almost 35 % to the fine-particle organic water of the aerosol. Observation-derived calculations of the cloud droplet concentrations that develop for typical boundary layer cloud conditions suggest that biomass burning increases droplet number, on average by 8.5 %. The strongly sublinear response of clouds to biomass-burning (BB) influences is a result of strong competition of CCN for water vapor, which results in very low maximum supersaturation (0.08 % on average). Attributing droplet number variations to the total aerosol number and the chemical composition variations shows that the importance of chemical composition increases with distance, contributing up to 25 % of the total droplet variability. Therefore, although BB may strongly elevate CCN numbers, the impact on droplet number is limited by water vapor availability and depends on the aerosol particle concentration levels associated with the background.

Concentration Variations in Primary and Secondary Particulate Matter near a Major Road in Korea

Particle-phase concentrations were measured at 10, 80, and 200 m from the roadside of a national highway near Seoul in January and May 2008. The highway has two lanes each way, with an average hourly traffic volume of 1,070 vehicles. In January 2008, PM 10 concentrations decreased from 10 to 80 m but increased at 200 m. Black carbon (BC) decreased only slightly with distance due to the influence of biomass burning and open burning from the surrounding areas. In May 2008, the effect of secondary formation on both PM 10 and PM 2.5 was significant due to high temperatures compared with January. Because on-road emissions had little effect on secondary formation for a short time, variations in PM 10 concentrations became smaller, and PM 2.5 concentrations increased with distance. The effects of fugitive dust on PM concentrations were greater in May than in January when the mean temperature was below freezing. In the composition variations, the amounts of primary ions, organic carbon (OC), and BC were larger in January, while those of secondary ions and others were larger in PM 10 , as well as PM 2.5 in May.

AIRUSE-LIFE+: a harmonized PM speciation and source apportionment in five southern European cities

Abstract. The AIRUSE-LIFE+ project aims at characterizing similarities and heterogeneities in particulate matter (PM) sources and contributions in urban areas from southern Europe. Once the main PMx sources are identified, AIRUSE aims at developing and testing the efficiency of specific and non-specific measures to improve urban air quality. This article reports the results of the source apportionment of PM10 and PM2.5 conducted at three urban background sites (Barcelona, Florence and Milan, BCN-UB, FI-UB and MLN-UB), one suburban background site (Athens, ATH-SUB) and one traffic site (Porto, POR-TR). After collecting 1047 PM10 and 1116 PM2.5 24 h samples during 12 months (from January 2013 on) simultaneously at the five cities, these were analysed for the contents of OC, EC, anions, cations, major and trace elements and levoglucosan. The USEPA PMF5 receptor model was applied to these data sets in a harmonized way for each city. The sum of vehicle exhaust (VEX) and non-exhaust (NEX) contributes between 3.9 and 10.8 µg m−3 (16–32 %) to PM10 and 2.3 and 9.4 µg m−3 (15–36 %) to PM2.5, although a fraction of secondary nitrate is also traffic-related but could not be estimated. Important contributions arise from secondary particles (nitrate, sulfate and organics) in PM2.5 (37–82 %) but also in PM10 (40–71 %), mostly at background sites, revealing the importance of abating gaseous precursors in designing air quality plans. Biomass burning (BB) contributions vary widely, from 14–24 % of PM10 in POR-TR, MLN-UB and FI-UB, 7 % in ATH-SUB, to < 2 % in BCN-UB. In PM2.5, BB is the second most important source in MLN-UB (21 %) and in POR-TR (18 %), the third one in FI-UB (21 %) and ATH-SUB (11 %), but is again negligible (< 2 %) in BCN-UB. This large variability among cities is mostly due to the degree of penetration of biomass for residential heating. In Barcelona natural gas is very well supplied across the city and is used as fuel in 96 % of homes, while in other cities, PM levels increase on an annual basis by 1–9 µg m−3 due to biomass burning influence. Other significant sources are the following. – Local dust, 7–12 % of PM10 at SUB and UB sites and 19 % at the TR site, revealing a contribution from road dust resuspension. In PM2.5 percentages decrease to 2–7 % at SUB-UB sites and 15 % at the TR site. – Industry, mainly metallurgy, contributing 4–11 % of PM10 (5–12 % in PM2.5), but only at BCN-UB, POR-TR and MLN-UB. No clear impact of industrial emissions was found in FI-UB and ATH-SUB. – Natural contributions from sea salt (13 % of PM10 in POR-TR, but only 2–7 % in the other cities) and Saharan dust (14 % in ATH-SUB, but less than 4 % in the other cities). During high pollution days, the largest sources (i.e. excluding secondary aerosol factors) of PM10 and PM2.5 are VEX + NEX in BCN-UB (27–22 %) and POR-TR (31–33 %), BB in FI-UB (30–33 %) and MLN-UB (35–26 %) and Saharan dust in ATH-SUB (52–45 %). During those days, there are also quite important industrial contributions in BCN-UB (17–18 %) and local dust in POR-TR (28–20 %).

Atmospheric composition in the Eastern Mediterranean: Influence of biomass burning during summertime using the WRF-Chem model

The composition of the atmosphere over the Aegean Sea (AS) during an ‘Etesian’ outbreak under the influence of biomass burning (BB) activity is investigated. Simulations with the fully coupled WRF-Chem model during the Aegean-GAME campaign (29/8-9/9/2011) are used to examine the BB effect over the region. Two distinct Etesian flow patterns characterized by different transport conditions are analysed. The influence of the off-line calculated BB emissions on the atmospheric chemical composition over the AS under these conditions is estimated. In addition, sensitivity runs are used to examine the influence of the biogenic emissions calculated on-line and the realistic representation of the stratosphere-troposphere exchange processes are investigated through the time-varying chemical boundary conditions from the MOZART global chemical transport model. The horizontal and vertical distributions of gaseous and aerosol species are simulated under long-range transport conditions and interpreted in relation to the evolution of the Planetary Boundary Layer (PBL). In the case of a weaker synoptic system (medium-range transport conditions), even a small variability of meteorological parameters in limited areas become critical for the spatial distribution of gases and aerosols. The BB activity increases O3, PM2.5 and organic matter concentrations up to 5.5 ppb, 5.8 μg m−3 and 3.3 μg m−3, respectively. The spatial extent of the simulated BB plumes is further examined by comparison with airborne measurements of hydrogen cyanide (HCN). The estimated effect of biogenic emissions on O3 and PM2.5 concentrations is either positive or negative (±6 ppb for O3 and up to ± 1 μg m−3 for PM2.5) depending on the emission algorithm employed. The realistic representation of the chemical boundary conditions reproduces an observed layer rich in O3 above 4 km, but also increases O3 concentrations inside the PBL by up to 40%.

Size-distribution of airborne polycyclic aromatic hydrocarbons and other organic source markers in the surroundings of a cement plant powered with alternative fuels

The distributions of polycyclic aromatic hydrocarbons (PAHs) and molecular tracer organic compounds for biomass combustion, traffic emissions, soil dust, and secondary aerosol processing have been studied in three fractions of ambient air particulate matter (PM10, 2.5, and 1) collected in the vicinity of a cement plant. PAH concentrations were used to estimate the carcinogenic risks in humans. Combustion related compounds, including PAHs, and those from secondary aerosol processing, predominated in the finest (PM<1) fraction, while saccharides related to organic soil dust predominated in the coarse fraction (2.5<PM<10). The molecular markers of biomass combustion were found in high concentrations, indicating the influence of biomass burning on PM. Most predominant PAHs were five and six rings species, related to a PAH profile characteristic of urban-industrial environments. The concentrations of benzo[a]pyrene varied between 0.2 and 1.0ng/m3, which is close but lower than the annual limit value of 1ng/m3 established by law. Exposure and inhalation carcinogenic risks from total PAHs were below the EPA threshold of acceptable risk (1·10−6).

Size distribution characteristics of carbonaceous aerosol in Xishuangbanna, southwest China: a sign for biomass burning in Asia.

In 2012, size-segregated aerosol samples were collected in Xishuangbanna, a forest station in southwest China. The concentrations of organic and elemental carbon (OC and EC for short) were quantified with thermal/optical carbon analyzer in the filter samples. OC and EC exhibited similar seasonal patterns, with the highest concentrations in spring, possibly due to the influence of biomass burning in south and southeast Asia. The mass size distributions of OC and EC were bimodal in all the sampling seasons, each with a dominant peak in the fine mode of 0.4-0.7 μm and a coarse peak in the size range of 2.1-4.7 μm. In fine mode, OC and EC showed smaller geometric mean diameters (GMDs) during winter. OC and EC were prone to be more concentrated in fine particles in spring and winter than in summer and autumn. Furthermore, EC was more abundant in fine particles than OC. Good correlations (R(2) = 0.75-0.82) between OC and EC indicated that they had common dominant sources of combustion such as biomass burning and fossil fuel combustion emissions. The daily average OC/EC ratios ranged from 2.1 to 9.1, more elevated OC/EC ratios being found in the winter.

Historic records of organic compounds from a high Alpine glacier: influences of biomass burning, anthropogenic emissions, and dust transport

Abstract. Historic records of α-dicarbonyls (glyoxal, methylglyoxal), carboxylic acids (C6–C12 dicarboxylic acids, pinic acid, p-hydroxybenzoic acid, phthalic acid, 4-methylphthalic acid), and ions (oxalate, formate, calcium) were determined with annual resolution in an ice core from Grenzgletscher in the southern Swiss Alps, covering the time period from 1942 to 1993. Chemical analysis of the organic compounds was conducted using ultra-high-performance liquid chromatography (UHPLC) coupled to electrospray ionization high-resolution mass spectrometry (ESI-HRMS) for dicarbonyls and long-chain carboxylic acids and ion chromatography for short-chain carboxylates. Long-term records of the carboxylic acids and dicarbonyls, as well as their source apportionment, are reported for western Europe. This is the first study comprising long-term trends of dicarbonyls and long-chain dicarboxylic acids (C6–C12) in Alpine precipitation. Source assignment of the organic species present in the ice core was performed using principal component analysis. Our results suggest biomass burning, anthropogenic emissions, and transport of mineral dust to be the main parameters influencing the concentration of organic compounds. Ice core records of several highly correlated compounds (e.g., p-hydroxybenzoic acid, pinic acid, pimelic, and suberic acids) can be related to the forest fire history in southern Switzerland. P-hydroxybenzoic acid was found to be the best organic fire tracer in the study area, revealing the highest correlation with the burned area from fires. Historical records of methylglyoxal, phthalic acid, and dicarboxylic acids adipic acid, sebacic acid, and dodecanedioic acid are comparable with that of anthropogenic emissions of volatile organic compounds (VOCs). The small organic acids, oxalic acid and formic acid, are both highly correlated with calcium, suggesting their records to be affected by changing mineral dust transport to the drilling site.

Fog composition at Baengnyeong Island in the eastern Yellow Sea: detecting markers of aqueous atmospheric oxidations

Abstract. Samples of fog water were collected at Baengnyeong Island (BYI) in the Yellow Sea during the summer of 2014. The most abundant chemical species in the fog water were NH4+ (mean of 2220 µM), NO3− (1260 µM), SO4−2 (730 µM), and Na+ (551 µM), with substantial contributions from other species consistent with marine and biomass burning influence on some dates. The pH of the samples ranged between 3.48 and 5.00, with a mean of 3.94, intermediate within pH values of fog/cloud water reported previously in Southeast Asia. Back trajectories (72 h) showed that high relative humidity ( &gt; 80 %) was encountered upwind of the sampling site by all but one of the sampled air masses, and that the fog composition at BYI can be impacted by several different source regions, including the Sea of Japan, southeastern China, northeastern China, and the East China Sea. Sulfur in the collected fog was highly oxidized: low S(IV) concentrations were measured (mean of 2.36 µM) in contrast to SO4−2 and in contrast to fog/cloud S(IV) concentrations from pollutant source regions; organosulfate species were also observed and were most likely formed through aging of mainly biogenic volatile organic compounds. Low-molecular-mass organic acids were major contributors to total organic carbon (TOC; 36–69 %), comprising a fraction of TOC at the upper end of that seen in fogs and clouds in other polluted environments. Large contributions were observed from not only acetic and formic acids but also oxalic, succinic, maleic, and other organic acids that can be produced in aqueous atmospheric organic processing (AAOP) reactions. These samples of East Asian fog water containing highly oxidized components represent fog downwind of pollutant sources and can provide new insight into the fate of regional emissions. In particular, these samples demonstrate the result of extensive photochemical aging during multiday transport, including oxidation within wet aerosols and fogs.

First Quantification of Imidazoles in Ambient Aerosol Particles: Potential Photosensitizers, Brown Carbon Constituents, and Hazardous Components.

Imidazoles are widely discussed in recent literature. They have been studied as a secondary product of the reaction of dicarbonyls with nitrogen containing compounds in a number of laboratory studies, potentially acting as photosensitizers triggering secondary organic aerosol growth and are forming constituents of light absorbing brown carbon. Despite the knowledge from laboratory studies, no quantitative information about imidazoles in ambient aerosol particles is available. Within the present study, five imidazoles (1-butylimidazole, 1-ethylimidazole, 2-ethylimidazole, imidazol-2-carboxaldehyde, and 4(5)-methylimidazole) were successfully identified and quantified for the first time in ambient aerosol samples from different environments in Europe and China. Their concentrations range between 0.2 and 14 ng/m(3). 4(5)-Methylimidazole was found to be the most abundant imidazole. The occurrence of imidazoles seems to be favored at sites with strong biomass burning influence or connected to more polluted air masses. No connection was found between aerosol particle pH and imidazole concentration. Our work corroborates the laboratory studies by showing that imidazoles are present in ambient aerosol samples in measurable amounts. Moreover, it further motivates to explore the potential photosensitizing properties of small alkyl-substituted imidazoles.

Impact of Smoke Intensity on Size-Resolved Aerosol Composition and Microstructure during the Biomass Burning Season in Northwest Vietnam

Aerosol particles significantly impact the regional environment, including climate change, specifically in periods of extensive biomass burning. The major agricultural and domestic combustion emission sources were assessed in near-source and ambient monitoring campaigns in northwestern Vietnam during the dry season. The composition and microstructure of on-field burning and cooking emissions were analyzed with a variety of techniques. A wide range of observed PM2.5 mass concentrations was categorized according to the smoke level, supported by the evolution of carbon fractions (OC and EC) as well as ionic species and molecular tracers (K+, levoglucosan, and mannosan). The OC/EC and individual organic compound ratios on days with high smoke levels indicate smoldering combustion of softwood and other local biomass species, impacting aerosol composition at the regional level. Acid and non-acid carbonyls, carboxylates, and aliphatic carbon functionalities in the PM2.5 size fraction evolved with increasing smoke intensity, together with carbonates in coarse (PM1–2.5 and PM2.5–10) size fractions, indicating a large impact of smoke emissions and soil lifted up by the intense fires. Biomass burning influence increased the abundance of soot and organic particles in the submicron fraction from 12% at low to 59% and 68% at moderate and high smoke levels, respectively. Smoke micromarkers of local biomass burning source emissions determined the microstructure of ambient aerosols representative for northern Southeast Asia.

Mixing state and sources of submicron regional background aerosols in the northern Qinghai–Tibet Plateau and the influence of biomass burning

Abstract. Transmission electron microscopy (TEM) was employed to obtain morphology, size, composition, and mixing state of background aerosols with diameter less than 1 μm in the northern Qinghai–Tibet Plateau (QTP) during 15 September to 15 October 2013. Individual aerosol particles mainly contained secondary inorganic aerosols (SIA – sulfate and nitrate) and organics during clean periods (PM2.5 mass concentration less than 2.5 μg m−3). The presence of K–Na–Cl associated with organics and an increase in soot particles suggest that an intense biomass burning event caused the highest PM2.5 concentrations (&gt; 30 μg m−3) during the study. A large number fraction of the fly-ash-containing particles (21.73 %) suggests that coal combustion emissions in the QTP significantly contributed to air pollutants at the medium pollution level (PM2.5: 10–30 μg m−3). We concluded that emissions from biomass burning and from coal combustion both constantly contribute to anthropogenic particles in the QTP atmosphere. Based on size distributions of individual particles at different pollution levels, we found that gas condensation on existing particles is an important chemical process for the formation of SIA with organic coating. TEM observations show that refractory aerosols (e.g., soot, fly ash, and visible organic particles) likely adhere to the surface of SIA particles larger than 200 nm due to coagulation. Organic coating and soot on surface of the aged particles likely influence their hygroscopic and optical properties, respectively, in the QTP. To our knowledge, this study reports the first microscopic analysis of fine particles in the background QTP air.

Source and meteorological influences on air quality (CO, CH4 &amp; CO2) at a Southern Hemisphere urban site

Abstract Wollongong, Australia is an urban site at the intersection of anthropogenic, biomass burning, biogenic and marine sources of atmospheric trace gases. The location offers a valuable opportunity to study drivers of atmospheric composition in the Southern Hemisphere. Here, a record of surface carbon monoxide (CO), methane (CH4) and carbon dioxide (CO2) was measured with an in situ Fourier transform infrared trace gas analyser between April 2011 and August 2014. Clean air was found to arrive at Wollongong in approximately 10% of air masses. Biomass burning influence was evident in the average annual cycle of clean air CO during austral spring. A significant negative short-term trend was found in clean air CO (−1.5 nmol mol−1 a−1), driven by a reduction in northern Australian biomass burning. Significant short-term positive trends in clean air CH4 (5.4 nmol mol−1 a−1) and CO2 (1.9 μmol mol−1 a−1) were consistent with the long-term global average trends. Polluted Wollongong air was investigated using wind-direction/wind-speed clustering, which revealed major influence from local urban and industrial sources from the south. High values of CH4, with anthropogenic ΔCH4/ΔCO2 enhancement ratio signatures, originated from the northwest, in the direction of local coal mining. A pollution climatology was developed for the region using back trajectory analysis and ΔO3/ΔCO enhancement ratios. Ozone production environments in austral spring and summer were associated with anticyclonic meteorology on the east coast of Australia, while ozone depletion environments in autumn and winter were associated with continental transport, or fast moving trajectories from southern latitudes. This implies the need to consider meteorological conditions when developing policies for controlling air quality.

Analysis of tropospheric ozone and carbon monoxide profiles over South America based on MOZAIC/IAGOS database and model simulations

We analysed ozone and carbon monoxide profiles measured by commercial aircrafts from the MOZAIC/IAGOS fleet, during ascending and descending flights over Caracas, in Venezuela, from August 1994 to December 2009, over Rio de Janeiro, from 1994 to 2004 and from July 2012 to June 2013, and over Sao Paulo, in Brazil, from August 1994 to 2005. For ozone, results showed a clean atmosphere over Caracas presenting the highest seasonal mean in March, April and May. Backward trajectory analyses with FLEXPART, of case studies for which the measured concentrations were high, showed that contributions from local, Central and North America, the Caribbean and Africa either from anthropogenic emissions, biomass burning or lightning were possible. Satellite products as fire counts from MODIS, lightning flash rates from LIS, and CO and O 3 from Infrared Atmospheric Sounding Interferometer and wind maps at different levels helped corroborate previous findings. Sensitivity studies performed with the chemical transport model GEOS-Chem captured the effect of anthropogenic emissions but underestimated the influence of biomass burning, which could be due to an underestimation of GFEDv2 emission inventory. The model detected the contribution of lightning from Africa in JJA and SON and from South America in DJF, possibly from the northeast of Brazil. Over Sao Paulo and Rio de Janeiro, GEOS-Chem captured the seasonal variability of lightning produced in South America and attributed this source as the most important in this region, except in JJA, when anthropogenic emissions were addressed as the more impacting source of ozone precursors. However, comparison with the measurements indicated that the model overestimated ozone formation, which could be due to the convective parameterisation or the stratospheric influence. The highest ozone concentration was observed during September to November, but the model attributed only a small influence of biomass burning from South America, with no contribution of long-range transport from Africa. Keywords: tropospheric ozone, carbon monoxide, MOZAIC/IAGOS, air pollution, GEOS-Chem, FLEXPART, South America, biomass burning, IASI (Published: 21 October 2015) Citation: Tellus B 2015, 67, 27884, http://dx.doi.org/10.3402/tellusb.v67.27884

Characteristics of ambient volatile organic compounds and the influence of biomass burning at a rural site in Northern China during summer 2013

Abstract Volatile organic compounds (VOCs) were measured at a rural site in the North China Plain during summer 2013, which focused on VOCs characteristics and impact of biomass burning. Alkanes and halocarbons made the largest contribution to the sum of the mixing ratio of each VOC compound (total VOCs). Most VOC species mixing ratios had similar day-to-day variability, indicating that the air mass at the sampling site had small local perturbation. Accumulation of pollutants due to biomass burning and advection of plumes from urbanized areas upwind had important impact on diurnal variation patterns of the VOC group. Ethylbenzene/m,p-xylene ratio and its relationship with O3 indicated that sampling site received an aged air parcel. The aromatics and alkenes were the dominant contributors to total ozone formation potential (OFP). The top 5 VOC species based on OFP were toluene, isoprene, ethene, propene and n-Hexane. During the biomass burning period, VOCs had higher OFP values, especially the aromatics and alkynes. The backward trajectories indicated that extensive transport of biomass burning from the Shandong and Hebei provinces had an important effect on VOCs pollution levels.

The Implications of Fire Management in the Andean Paramo: A Preliminary Assessment Using Satellite Remote Sensing

The upper ranges of the northern Andes are characterized by unique Neotropical, high altitude ecosystems known as paramos. These tundra-like grasslands are widely recognized by the scientific community for their biodiversity and their important ecosystem services for the local human population. Despite their remoteness, limited accessibility for humans and waterlogged soils, paramos are highly flammable ecosystems. They are constantly under the influence of seasonal biomass burning mostly caused by humans. Nevertheless, little is known about the spatial extent of these fires, their regime and the resulting ecological impacts. This paper presents a thorough mapping and analysis of the fires in one of the world’s largest paramo, namely the “Complejo de Páramos” of Cruz Verde-Sumapaz in the Eastern mountain range of the Andes (Colombia). Landsat TM/ETM+ and MODIS imagery from 2001 to 2013 was used to map and analyze the spatial distribution of fires and their intra- and inter-annual variability. Moreover, a logistic regression model analysis was undertaken to test the hypothesis that the dynamics of the paramo fires can be related to human pressures. The resulting map shows that the burned paramo areas account for 57,179.8 hectares, of which 50% (28,604.3 hectares) are located within the Sumapaz National Park. The findings show that the fire season mainly occurs from January to March. The accuracy assessment carried out using a confusion matrix based on 20 reference burned areas shows values of 90.1% (producer accuracy) for the mapped burned areas with a Kappa Index of Agreement (KIA) of 0.746. The results of the logistic regression model suggest a significant predictive relevance of the variables road distance (0.55 ROC (receiver operating characteristic)) and slope gradient (0.53 ROC), indicating that the higher the probability of fire occurrence, the smaller the distance to the road and the higher the probability of more gentle slopes. The paper sheds light on fires in the Colombian paramos and provides a solid basis for further investigation of the impacts on the natural ecosystem functions and biodiversity.