Carbonaceous Content Research Articles

Long-range transport and source apportionment of marine fine particles in the Taiwan Strait and South China Sea Intersection: Spatiotemporal variations and chemical fingerprints

This study aims to investigate the spatiotemporal variation, chemical characteristics and source apportionment of marine fine particles (PM2.5), and to analyze the transport route towards the intersectional region of the Taiwan Strait and South China Sea. Sampling of PM2.5 was conducted simultaneously at Penghu and Dongsha Islands for 14 consecutive days each quarter from summer 2019 to spring 2020. PM2.5 samples were then returned for conditioning, weighting, and chemical analysis. The chemical mass balance (CMB) receptor model was used to identify the potential PM2.5 sources. It results show that the lowest PM2.5 concentrations were observed in summer, with a gradual increase starting fall, influenced by Asia Northeastern Monsoons (ANMs) transporting particles from the north to Penghu and Dongsha Islands. The most abundant water-soluble ionic species in PM2.5 were SO42−, NO3− and NH4+, catalogued as the secondary inorganic aerosols (SIAs). Meanwhile, the most abundant metals in PM2.5 were crustal elements (Mg, K, Ca, Fe, and Al), while the concentrations of trace metals (V, Cr, Mn, Ni, As, Cd, and Pb), mainly from anthropogenic sources, also increased from fall onwards. Organic carbon (OC) was the main species of carbonaceous content of PM2.5 in all seasons, and OC/EC ratios increased during the seasons with prevailing northeastern winds. Anhydrosugar, concentrations in winter and spring were generally higher than those in summer and fall, indicating significant biomass burning occurring in winter and spring. Correlation analysis showed a high correlation between PM2.5 concentrations and chemical composition between two subtropical islands. The correlation of chemical composition for different transportation routes revealed that northern routes had a higher correction than southern routes. Overall, the cross-boundary PM, accounted for 28.4–61.0% and 36.4–76.8% at Penghu and Dongsha Islands, respectively, significantly impacted local air quality, particularly at Dongsha Islands.

Long term trend of particulate matter in Philadelphia, Pennsylvania and its association with introduction of environmental policies

Since the 1970s, air quality has improved at the national level in the United States, coincident with the introduction of the Clean Air Act and other air pollution regulations at a greater frequency. We present a case study from Philadelphia, Pennsylvania—the sixth most populous city in the United States. The main objectives of this study are to analyze long-term trends of particulate matter (PM) from 1986 to 2021 in Philadelphia and to examine their association with the introduction of environmental policies relevant to air pollution at the federal, state, and local levels. We find that annual PM10 concentration decreased by 47% from 1986 to 2021 and annual PM2.5 concentration decreased by 31% from 2000 to 2021 in Philadelphia. We find that carbonaceous content (both elemental and organic carbon) has declined over the same period of 2000 to 2021, demonstrating its contribution to overall PM2.5 reduction in Philadelphia. In Philadelphia, high PM concentrations occur in the summer months; however, seasonal patterns have changed for PM10 in the last decade (2011–2020). Overall, PM reductions occurred over all seasons, with the greatest reductions occurring for PM2.5 during summer months and for PM10 during winter months. The Clean Air Act contributed to the creation of many regulatory policies that address unhealthy levels of PM. The introduction of various environmental policies that target the transportation sector has contributed to the reduction of PM levels in Philadelphia. Air quality would continue being improved by implementing such environmental policies specific to the emissions sectors.

Characterization and apportionment of carbonaceous aerosol emission factors from light-duty and heavy-duty vehicle fleets in Maharashtra, India

This study aims to investigate the characteristics of carbonaceous aerosols and estimate emission factor (EF) based on roadway tunnel measurements, from two distinct vehicular fleets: an all light-duty vehicle (LDV) fleet, and a mixed fleet of 80% LDV and 20% heavy-duty vehicle (HDV). Carbonaceous content (organic carbon: OC and elemental carbon: EC) in total fine particles (PM2.5) accounted for 41% ± 6.8% in LDV fleet and 48% ± 7.2% in mixed fleet. While higher volatile OC dominated in the LDV fleet emissions, in mixed fleet, lower volatile OC and EC emissions dominated due to the presence of higher HDV and super-emitter (SE) fractions which led to significantly higher optically active absorbing aerosols. Reconstructed HDV fleet EF was higher than LDV fleet by 36 times (PM2.5), 19 times (OC) and 51 times (EC). Our findings emphasize the significance of implementing vehicle inspection and maintenance programs, coupled with decarbonization of HDVs to mitigate on-road vehicular emissions in India.

Solving the mystery of natural pyrite flotation – A mineralogy-based approach

Many different types of pyrite have been observed in the mineral processing industry, varying in texture, chemical composition, electrochemical properties, and flotation response. One particular type of pyrite has been noted for its unusual behaviour is framboidal or “carbonaceous” pyrite. Specifically, a long history of carbonaceous pyrite presence has been recorded and studied at Glencore's Mount Isa Mines.This work is a detailed examination of the mineralogical characteristics of ore samples containing different pyrite types, to determine the underlying drivers of natural pyrite flotation. The work also revisits the original hypothesis that pyrite floatability is facilitated by the presence of carbonaceous material within the mineral matrix.Overall, this work closely mirrored that of previous studies, with the results closely aligned. The main difference is that when multiple ore domains are subjected to the same analysis, the flotation behaviour of carbonaceous content and pyrite appear to be independent. Instead, excessive natural flotation recoveries of pyrite are likely to be driven by factors that include the effect of galvanic interactions between chalcopyrite and pyrite.

Insights into the synergistic calcination of spent pot lining and red mud for stabilization of fluorine and recovery of iron

Spent pot-lining (SPL) and red mud (RM) are significant industrial solid wastes generated from the aluminum industry, holding valuable potential as secondary resources. This study addresses the pressing challenges of mitigating fluoride emissions resulting from the pyrometallurgical process of SPL and recovering iron (Fe) components from RM. To achieve these objectives, a synergetic reduction-stabilization process via co-calcination was proposed. During co-calcination, the carbonaceous content of SPL acts as a reducing agent, facilitating the reduction of Fe oxides in RM to magnetite (Fe3O4). The recovered Fe3O4 was efficiently separated through magnetic separation with 66.9% recovery efficiency. Additionally, the co-calcination process synergistically stabilizes fluoride emissions from SPL due to the presence of calcium oxide (CaO) in RM. This results in fluoride emissions reacting with CaO to form insoluble fluorite (CaF2), leading to significantly reduced fluoride leaching concentrations (18.3 mg L−1), well below national recommended standards (100 mg L−1). Mineral transformations revealed that Na3AlF6 from SPL decomposed into NaF, AlF3, and HF, with subsequent reactions with CaO leading to CaF2 formation. The selectivity of element combinations among Ca-Fe-F-O can be attributed to the distinct ionic potentials in the HF-CaO-Fe2O3-C system, where CaF2 arose from a hard acid (Ca(II))-hard base (F-) interaction, and Fe2O3 reduction was influenced by the weaker bonding between soft base O2- and borderline acid Fe(III)/Fe(II) repulsion, according to the Hard-Soft Acid-Base (HSAB) theory. This proposed synergistic utilization approach not only detoxifies harmful fluoride emissions but also offers a sustainable method for Fe recovery, holding significant potential for environmental and economic benefits in the context of aluminum industry waste management practices.

Preliminary assessment of road dust from Portuguese motorways: chemical profile, health risks, and ecotoxicological screening

Among non-exhaust emissions, road dust resuspension represents a rather important contribution to particulate matter in urban areas. This study aimed to achieve a chemical characterisation of road dust particulate matter (PM10) on two motorway sections, one rural and one urban, and to explore the related health and ecotoxicological risks. Measured PM10 dust loadings reached very low levels (0.66–1.49 mg m-2) compared to equivalent studies in other road environments in Portugal and other countries. Emission factors ranged from 33 to 62 mg veh−1 km−1. The carbonaceous content represented 14% of the total PM10 mass, whereas the highest contribution to the mass was given by mineral matter. Elements such as Si, Al, Ca, Fe and K accounted for almost three quarters of the total element mass for all samples, whilst Cu and Zn, mostly associated with brake and tyre wear, were the most enriched elements in relation to the soil composition. Nonetheless, Ti and Zr presented the highest non-carcinogenic risks for human health. Despite the low amounts of particulate matter in the aqueous solution, the ecotoxicological screening with the Aliivibrio fisheri bioluminescence inhibition bioassay allowed to classify the samples as toxic.

PM10 Resuspension of Road Dust in Different Types of Parking Lots: Emissions, Chemical Characterisation and Ecotoxicity

The thoracic fraction of road dust (PM10) was measured for the first time in Portugal in parking areas, both outdoors and indoors, with the aim of completing existing studies carried out in active lanes of various roads. An in situ resuspension chamber was used to collect a total of 23 samples in three parking areas of Aveiro, whilst the laboratory procedures included determination of carbonaceous content (OC and EC) by a thermo-optical technique, elemental composition by ICP-MS and ICP-OES after acid digestion, and the Aliivribrio fisherii bioluminescent bacteria ecotoxicity bioassay. Dust loadings (DL10) obtained were 18.5 ± 9.8 mg PM10 m−2, in outdoor parking, and 1.8–23.7 mg PM10 m−2 for indoor parking, corresponding to emission factors of 476 and 75–589 mg veh−1 km−1, respectively. OC represented 9–30 % of PM10 for the indoor parking areas. However, for the outdoor samples, the high iron oxide content jeopardised the OC-EC separation. In those samples, carbonates accounted for 10.0 ± 3.3% of the PM10 mass. The analysis of elemental components focused on major elements (Al, Ca, Fe, K, and Mg) as well as minor elements. The total mass fraction of element oxides accounted for 27.1% (outdoor) and 23.6–34.3% (indoor). ΣPAH calculated for all parking areas accounted for 8.38–36.9 μg g−1 PM10. The ecotoxicological bioassay showed that all aqueous solutions were toxic to bioluminescent bacteria, whereas no clear correlations could be made with specific component groups, with the exception of ΣPAH and EC50.

Molecular investigation of the multi-phase photochemistry of Fe(III)-citrate in aqueous solution.

Iron (Fe) is ubiquitous in nature and found as FeII or FeIII in minerals or as dissolved ions Fe2+ or Fe3+ in aqueous systems. The interactions of soluble Fe have important implications for fresh water and marine biogeochemical cycles, which have impacts on global terrestrial and atmospheric environments. Upon dissolution of FeIII into natural aquatic systems, organic carboxylic acids efficiently chelate FeIII to form [FeIII-carboxylate]2+ complexes that undergo a wide range of photochemistry-induced radical reactions. The chemical composition and photochemical transformations of these mixtures are largely unknown, making it challenging to estimate their environmental impact. To investigate the photochemical process of FeIII-carboxylates at the molecular level, we conduct a comprehensive experimental study employing UV-visible spectroscopy, liquid chromatography coupled to photodiode array and high-resolution mass spectrometry detection, and oil immersion flow microscopy. In this study, aqueous solutions of FeIII-citrate were photolyzed under 365 nm light in an experimental setup with an apparent quantum yield of (φ) ∼0.02, followed by chemical analyses of reacted mixtures withdrawn at increment time intervals of the experiment. The apparent photochemical reaction kinetics of Fe3+-citrates (aq) were expressed as two generalized consecutive reactions of with the experimental rate constants of j1 ∼ 0.12 min-1 and j2 ∼ 0.05 min-1, respectively. Molecular characterization results indicate that R and I consist of both water-soluble organic and Fe-organic species, while P compounds are a mixture of water-soluble and colloidal materials. The latter were identified as Fe-carbonaceous colloids formed at long photolysis times. The carbonaceous content of these colloids was identified as unsaturated organic species with low oxygen content and carbon with a reduced oxidation state, indicative of their plausible radical recombination mechanism under oxygen-deprived conditions typical for the extensively photolyzed mixtures. Based on the molecular characterization results, we discuss the comprehensive reaction mechanism of FeIII-citrate photochemistry and report on the formation of previously unexplored colloidal reaction products, which may contribute to atmospheric and terrestrial light-absorbing materials in aquatic environments.

A Systematic Review on Long Term Variation of Carbonaceous Aerosols in Pm2.5 at Different Sites of “Delhi” Capital City of India

Being a criteria pollutant Fine Particulate Matter (PM2.5) exposure not only affects human health but also deteriorates environmental health, air quality and artifacts. Traffic, biomass burning and industrial activities are important contributors to ambient fine particulate matter in major cities of the world. Therefore, to reduce fine particulate matter pollution and the considerable disease burden it causes solutions to bring down ambient fine particulate matter are needed. Carbonaceous aerosols are found to be a significant contributor to fine particulate matter. These aerosols are subdivided into organic carbon and elemental carbon. Elemental carbon is released from primary sources whereas organic carbon can be released either from primary or secondary sources. This paper presents a comprehensive critical review of the assessment of fine particulate matter and its carbonaceous content in the past decade on different sites in New Delhi, the capital of India. Considerable health effects of particulate pollution have also been discussed in the paper. Critically reviewed data showed a non – significant increase in the trend of particulate matter concentration. It was also shown through the data of each study that the emission standards of WHO exceeded by 15 times whereas for NAAQS they exceeded by 5 times respectively.

Inter-comparison of chemical fingerprint and source apportionment of marine fine particles at two islands through the west and east passages of the Taiwan Island

In this study, the concentrations of marine fine particles (PM2.5) and their chemical fingerprints were inter-compared at two islands located aside from the west and east waters of Taiwan Island and the variability of west and east passages (i.e., Routes A1 and A2) were explored. Marine PM2.5 was simultaneously sampled at the Green and Dongsha Islands and five chemical components (i.e., water-soluble ions, metallic elements, carbonaceous content, anhydrosugars, and organic acids) were further analyzed in PM2.5 to characterize their chemical fingerprints. The highest concentrations of chemical composition and PM2.5 were commonly observed during the Asian Northeastern Monsoons (ANMs) via long-range transport (LRT). Water-soluble ions (WSIs) were dominated by secondary inorganic aerosols (SIAs), and followed by oceanic spray. The major metallic content of PM2.5 was crustal elements, while trace metals originated from anthropogenic sources with an enrichment factor (EF) > 10. In terms of carbonaceous content in PM2.5, organic carbon (OC) was superior to elemental carbon (EC). High levoglucosan concentrations were also observed during the periods of ANMs. Secondary organic aerosols (SOAs) were formed by atmospheric chemical reactions during the LRT procedure. The PM2.5 concentration of Route A1 was 37.51 % higher than that of Route A2, and trace metals (V, Mn, Ni, Pb, Cr, and Cu) increased significantly by 96.16–325.83 %. Positive matrix factorization (PMF) results revealed that the dominant factor of PM2.5 for Route A1 was shipping emissions and vehicular exhausts (41.2 %), while that for Route A2 was oceanic spray (30.2 %). Route A1 was mainly attributed to highly industrialized regions, densely populated urbanized areas, and ship-intensive traffics in East Asia.

Characterisation of non-exhaust emissions from road traffic in Lisbon

Non-exhaust emissions from road transport include particles from brake and tyre wear, road surface abrasion and dust resuspension. Road dust loads and their chemical properties are heterogeneous and their knowledge is still scarce. This study aimed to characterise, for the first time in Lisbon, the thoracic fraction of road dust (PM10) by collecting samples directly from road pavements by an in situ resuspension chamber. The highest PM10 load (15.6 ± 8.75 mg m−2) was obtained on a cobblestone pavement, while for asphalt roads the mean PM10 load was 4.40 ± 0.16 mg m−2. Emission factors for asphalt pavements ranged from 83.5 to 274 mg veh−1 km−1. On average, 65.7% of the PM10 mass was reconstructed, taking into account the carbonaceous content and the sum of the elements in their oxidized form. Cu and Zn, associated with brake and tyre wear, were the most enriched elements in relation to the soil composition (EnF = 440 and 184, respectively). The highest potential ecological risk factor of individual metals (Eri) was also observed for Cu (EriCu = 393). In 90% of the sampled streets, the total carcinogenic risk was higher than 1E-4 for As, suggesting that exposure to this hazardous element may contribute to the development of cancer over a lifetime. The results showed the high contribution of certain dangerous chemical compounds associated with resuspension particles and their potential effects on human health.

Inhalation bioaccessibility of multi-class organic pollutants associated to atmospheric PM2.5: Correlation with PM2.5 properties and health risk assessment

Inhalation exposure to fine particulate matter (PM2.5) represents a global concern due to the adverse effects in human health. In the last years, scientific community has been adopted the assessment of the PM2.5-bound pollutant fraction that could be released (bioaccessible fraction) in simulated lung fluids (SLFs) to achieve a better understanding of PM risk assessment and toxicological studies. Thus, bioaccessibility of 49 organic pollutants, including 18 polycyclic aromatic hydrocarbons (PAHs), 12 phthalate esters (PAEs), 11 organophosphorus flame retardants (OPFRs), 6 synthetic musk compounds (SMCs) and 2 bisphenols in PM2.5 samples was evaluated. The proposed method consists of a physiologically based extraction test (PBET) by using artificial lysosomal fluid (ALF) to obtain bioaccessible fractions, followed by a vortex-assisted liquid-liquid microextraction (VALLME) and a final analysis by programmed temperature vaporization-gas chromatography-tandem mass spectrometry (PTV-GC-MS/MS). The highest inhalation bioaccessibility ratio was found for bisphenol A (BPA) with an average of 83%, followed by OPFRs, PAEs and PAHs (with average bioaccessibilities of 68%, 41% and 34%, respectively). Correlations between PM2.5 composition (major ions, trace metals, equivalent black carbon (eBC) and UV-absorbing particulate matter (UVPM)) and bioaccessibility ratios were also assessed. Principal Component Analysis (PCA) suggested that PAHs, PAES and OPFRs bioaccessibility ratios could be positively correlated with PM2.5 carbonaceous content. Furthermore, both inverse and positive correlations on PAHs, PAEs and OPFRs bioaccessibilites could be accounted for some major ions and metal (oid)s associated to PM2.5, whereas no correlations comprising considered PM2.5 major ions and metal (oid)s contents and BPA bioaccessibility was observed. In addition, health risk assessment of target PM2.5-associated PAHs via inhalation was assessed in the study area considering both total and bioaccessible concentrations, being averaged human health risks within the safe carcinogenic and non-carcinogenic levels.

Enrichment of residual carbon from coal gasification fine slag by spiral separator

Coal gasification is one of the most promising clean coal technologies. However, gasification process also produces a huge amount of solid waste of high carbon content, named coal gasification fine slag. The coal gasification fine slag is mainly handled by landfilling, which is not only a hazardous pollution, but also wasting the energy from residual carbon. Developing a technology to utilize coal gasification fine slag and recover the residual carbon is becoming essential for an eco-friendly coal chemical industry. In this paper, the enrichment behavior of residual carbon in coal gasification fine slag by a spiral separator is studied. The raw coal gasification fine slag sample and separator products are characterized on particle size distribution, size-depending ash content, reactivity, micromorphology and porous structure. The experimental results show that the spiral separator is efficient to remove ash and enriched carbonaceous components in coal gasification fine slag by separating feed (100%) into concentrate (81.2%), middlings (8.8%), and tailings (10.08%), where the ash content in tailings is up to 90%, accounting for 18.5% of total ash in feeding. The beneficial product “concentrate” has a good distribution of size-depending ash content, that most combustibles are enriched in these particles of diameter >100 μm. After spiral separator, the concentrate products have a more pure and developed porous structure with the surface area increasing from 199.8 m2/g (feeding) to 231.8 m2/g, as well as a better combustion reactivity of lower ignition temperature compared with feedings. Accordingly, an economic and feasible combination process of spiral separator connecting sieve can produce an enriched-carbon product of ∼45% yield and ∼80% carbonaceous content. The Iodine adsorption ability of sieved products increases by 47.6% compared with feed, and reaches up to about half of industry activated carbon. The finally sieved concentrate products have a good market prospect as fuel and adsorbent.

The Dopamine Assisted Synthesis of MoO3/Carbon Electrodes With Enhanced Capacitance in Aqueous Electrolyte.

A capacitance increase phenomenon is observed for MoO3 electrodes synthesized via a sol-gel process in the presence of dopamine hydrochloride (Dopa HCl) as compared to α-MoO3 electrodes in 5M ZnCl2 aqueous electrolyte. The synthesis approach is based on a hydrogen peroxide-initiated sol-gel reaction to which the Dopa HCl is added. The powder precursor (Dopa)xMoOy, is isolated from the metastable gel using freeze-drying. Hydrothermal treatment (HT) of the precursor results in the formation of MoO3 accompanied by carbonization of the organic molecules; designated as HT-MoO3/C. HT of the precipitate formed in the absence of dopamine in the reaction produced α-MoO3, which was used as a reference material in this study (α-MoO3-ref). Scanning electron microscopy (SEM) images show a nanobelt morphology for both HT-MoO3/C and α-MoO3-ref powders, but with distinct differences in the shape of the nanobelts. The presence of carbonaceous content in the structure of HT-MoO3/C is confirmed by FTIR and Raman spectroscopy measurements. X-ray diffraction (XRD) and Rietveld refinement analysis demonstrate the presence of α-MoO3 and h-MoO3 phases in the structure of HT-MoO3/C. The increased specific capacitance delivered by the HT-MoO3/C electrode as compared to the α-MoO3-ref electrode in 5M ZnCl2 electrolyte in a −0.25–0.70 V vs. Ag/AgCl potential window triggered a more detailed study in an expanded potential window. In the 5M ZnCl2 electrolyte at a scan rate of 2 mV s−1, the HT-MoO3/C electrode shows a second cycle capacitance of 347.6 F g−1. The higher electrochemical performance of the HT-MoO3/C electrode can be attributed to the presence of carbon in its structure, which can facilitate electron transport. Our study provides a new route for further development of metal oxides for energy storage applications.

Improving Air Quality Standards in Europe: Comparative Analysis of Regional Differences, with a Focus on Northern Italy

The study reports a consistent comparison of emission inventories, concentration trends, and PM source apportionment in different European regions and, mostly, a thorough investigation of meteorological parameters influencing atmospheric pollutants’ dispersion. The study focuses on the reasons why Northern Italy still has difficulties complying with EU air quality standards for PM10 and NO2, despite strong emission reductions. The study demonstrates that, in the colder seasons, wind speed, PBL height, and atmospheric pressure in the Po basin are three to five times less efficient at diluting and dispersing pollutants than those occurring in regions north of the Alps. Since air quality standards aim at countering health impacts, it is advisable to consider atmospheric particulate toxicity in addition to PM10/PM2.5 mass concentration as a limit value. A discussion is reported about PM toxicity factors depending on source-specific aerosols and PM composition. We obtained PM toxicity factors that can vary by 10 times (according to carbonaceous content) across Europe, suggesting that, even at the same mass concentration, the effects of PM10/PM2.5 on human health are significantly variable. Modern PM source apportionment and reliable toxicity and epidemiological analyses represent the correct tools to build a new consistent health metric for ambient PM.

Chemical significance and source apportionment of fine particles (PM2.5) in an industrial port area in East Asia

This study explored the chemical significance, seasonal variation, spatial distribution, and source apportionment of fine particles (PM2.5) in an industrial port area. 24-h PM2.5 was simultaneously sampled at three port sites. Five chemical contents in PM2.5 including water-soluble ions (WSIs), metallic elements, carbonaceous content, anhydrosugars, and organic acids were then analyzed. The source apportionment of PM2.5 was further resolved by trajectory simulation, principal component analysis (PCA), and chemical mass balance (CMB) receptor model. Both local sources and long-range transport contributed to the rise-up of PM2.5 levels. Secondary inorganic aerosols (SIAs) dominated WSIs in PM2.5. Crustal elements (Mg, Al, Ca, Fe, and K) dominated the metallic content of PM2.5, while trace elements (Ni, V, Cr, Zn, and Pb) were originated from anthropogenic sources. Ship emissions in the seaport and offshores caused high V/Ni ratios in summer. High OC/EC (2.04–2.23) and SOC/OC (28–34%) ratios were observed in fall and winter, implying the potential formation of secondary organic aerosols (SOAs) in atmosphere. High correlation of levoglucosan and K+ indicated that PM2.5 was greatly influenced by biomass burning (BB) in winter. Polluted air masses with high PM2.5 levels of 43.33 ± 11.84 μg/m3 in winter were blown from the norths by Asian Northeastern Monsoons (ANMs), while clean air masses with low PM2.5 levels of 9.13 ± 2.75 μg/m3 in summer came mainly from the oceans via Asian Southwestern Monsoons (ASMs). Source apportionment resolution showed that the dominant sources of PM2.5 in the Kaohsiung Seaport were industrial emissions, secondary aerosols (SIAs/SOAs), ship/vehicular exhausts, oceanic spray, and soil dust.

Short-Term and Long-Term Effects of Natural and Artificial Carbonaceous Substrates on Greenhouse Gas Fluxes

The emissions of two greenhouse gases (GHG), carbon dioxide (CO2) and nitrous oxide (N2O), from six substrates with different carbonaceous content were compared in short and long-term incubation experiments. Three natural soils and three artificial chars were mixed with carbon (C) poor soil (Cambisol) to simulate real conditions after application of char to farmland. The natural soils were a Cambisol, an Anthrosol and a Histosol with C contents of 1.3%, 4.4% and 13.2%, respectively. The three chars produced through thermal conversion of wood chips by hydrothermal carbonisation (HTC), fluidized bed gasification and pyrolysis had C contents of 56.9%, 75.4% and 79.9%, respectively. Emission rates of CO2 and N2O from the rewetted substrates were measured by gas chromatography over a short time of 72 h and over a long period of nearly two years. The short-term CO2 emissions from the natural soils showed a clear relationship to their C content. The emission rate for the Histosol/Cambisol mixture was three times higher than that for the pure Cambisol, 77.1 vs. 23.5 mg CO2-C kg−1 organic matter (OM) per hour. The C emission rates for the char/Cambisol mixtures were much lower, ranging between 3.0 and 9.1 mg CO2-C kg OM−1 h−1 , and did not correspond to their total C contents. Comparison between the two incubation lengths showed that the long-term CO2 emission rates were generally one order of magnitude lower than the short-term rates. The final emission rates for natural substrates over a period of two years were still twice those for artificial char substrates, between 2.2–3.5 mg CO2-C kg OM−1 h−1 and 1.3–1.8 mg CO2-C kg OM−1 h−1 , respectively. Although the contents of total nitrogen (Ntot) and extractable nitrogen (Nmin) were considerable in the chars under study, enhanced N2O release was not observed in the incubation experiments. Instead, N2O emission rates in the three mixtures of chars and Cambisol were lower by one to two orders of magnitude compared to the pure Cambisol in short-term incubations. Even long-term N2O emissions were 5 to 9 times lower. The highest degree of N2O reduction was found for the HTC char. Because of the high global warming potential of N2O, this positive effect of chars may play an important role in mitigating emissions of CO2 equivalents. Both CO2 and N2O must be taken into account when balancing GHG emitted after chars (biochar, gasifier char, HTC char) are applied to soil.

Methodology to Create Reproducible Validation/Reference Materials for Comparison of Filter-Based Measurements of Carbonaceous Aerosols That Measure BC, BrC, EC, OC, and TC

A simple method that reproducibly creates validation/reference materials for comparison of methods that measure the carbonaceous content of atmospheric particulate matter deposited on filter media at concentrations relevant to atmospheric levels has been developed and evaluated. Commonly used methods to determine the major carbonaceous components of particles collected on filters include optical attenuation for “Black” (BC) and “Brown” (BrC) carbon, thermal-optical analysis (TOA) for “Elemental” (EC) and “Organic” (OC) carbon, and total combustion for “Total” carbon (TC). The new method uses a commercial inkjet printer to deposit ink containing both organic and inorganic components onto filter substrates at programmable print densities (print levels, as specified by the printer–software combination). A variety of filter media were evaluated. The optical attenuation (ATN) of the deposited sample was determined at 880 nm and 370 nm. Reproducibility or precision (as standard deviation or in percent as coefficient of variation) in ATN for Teflon-coated glass-fiber, Teflon, and cellulose substrates was better than 5%. Reproducibility for other substrates was better than 15%. EC and OC measured on quartz-fiber filters (QFF) compared to ATN measured at 880 nm and 370 nm on either QFF or Teflon-coated glass-fiber yielded R2 > 0.92 and >0.97, respectively. Four independent laboratories participated in a round robin study together with the reference laboratory. The propagated standard deviation among the five groups across all print levels was <2.2 ATN at 880 nm and <2.7 ATN at 370 nm with a coefficient of variation of <2% at ~100 ATN.

Inter-comparison of chemical characteristics and source apportionment of PM2.5 at two harbors in the Philippines and Taiwan

This study inter-compared the concentration and chemical characteristics of PM2.5 at two harbors in East Asia, and identified the potential sources of PM2.5 and their contribution. Two sites located at the Kaohsiung (Taiwan) and Manila (the Philippines) Harbors were selected for simultaneous sampling of PM2.5 in four seasons. The sampling of 24-h PM2.5 was conducted for continuous seven days in each season. Water-soluble ions, metallic elements, carbonaceous content, anhydrosugars, and organic acids in PM2.5 were analyzed to characterize their chemical fingerprints. Receptor modeling and trajectory simulation were further applied to resolve the source apportionment of PM2.5. The results indicated that the Kaohsiung Harbor was highly influenced by long-range transport (LRT) of polluted air masses from Northeast Asia, while the Manila Harbor was mainly influenced by local emissions. Secondary inorganic aerosols were the most abundant ions in PM2.5. Crustal elements dominated the metallic content of PM2.5, but trace elements were mainly originated from anthropogenic sources. Higher concentrations of organic carbon (OC) than elemental carbon (EC) was found in PM2.5, with secondary OC (SOC) dominant to the former. Levoglucosan in PM2.5 at the Manila Harbor were superior to those at the Kaohsiung Harbor due to biomass burning surrounding the Manila Harbor. Additionally, high mass ratios of malonic and succinic acids (M/S) in PM2.5 indicated the formation of SOAs. Overall, the ambient air quality of Manila Harbor was more polluted than Kaohsiung Harbor. The Kaohsiung Harbor was more severely affected by LRT of polluted air masses from Northeast Asia, while those toward the Manila Harbor came from the oceans. The major sources resolved by CMB and PMF models at the Kaohsiung Harbor were secondary aerosols, ironworks, incinerators, oceanic spray, and ship emissions, while those at the Manila Harbor were secondary aerosols, soil dust, biomass burning, ship emissions, and oceanic spray.

Characterization of Burning Behaviors and Particulate Matter Emissions of Crop Straws Based on a Cone Calorimeter.

Crop residue burning is one of the major sources of particulate matter (PM) in the air. The burning behaviors and PM emissions of the three typical crop residues (rice straw, wheat straw, corn straw) in China were characterized by a cone calorimeter (CONE) coupled with a laser dust meter. The water-soluble compounds, carbonaceous content, and morphology of PM were measured by ion chromatography, elemental analyzer, transmission electron microscopy (TEM) and energy-dispersive X-ray spectrometer (EDS). The results showed that thermal stability of corn straw was the worst among the three crop straws. The heat release rate (HRR) curves of the three crop straws were the typical curves of thermally thick charring (residue forming) samples. Wheat straw had the highest smoke yield, which was 2.9 times that of rice straw. The PM emission factor of wheat straw was 180.91 µg/g, which was about three times that of rice straw. The contents of K+, Na+, and Cl− in PM were significantly higher than those of the other six water-soluble inorganic ions. The ratio of organic carbon and elemental carbon (OC/EC) ranged from 14.82 to 30.82, which was similar to the results of open burning. There were mainly three kinds of aggregates in the PM of crop straws: network, chain-like, and soot. Individual particles were mixtures of KCl and organic matters. Core-shell structures were found in PM of rice straw and corn straw. The results in this study were provided based on CONE, an ISO-standard apparatus, which could avoid data conflicts caused by the difference of combustion devices. The relationship between the burning behavior and PM emission characteristics of crop straws was established, which is helpful to understand emissions of crop straws and to find a novel way to solve the problems from the burning of crop residues.