Biogenic Sources Research Articles

CO2 Emissions Estimate From Mexico City Using Ground‐ and Space‐Based Remote Sensing

AbstractThe Mexico City Metropolitan Area (MCMA) stands as one of the most densely populated urban regions globally. To quantify the urban emissions in the MCMA, we independently assimilated observations from a dense column‐integrated Fourier transform infrared (FTIR) network and OCO‐3 Snapshot Area Map observations between October 2020 and May 2021. Applying a computationally efficient analytical Bayesian inversion technique, we inverted for surface fluxes at high spatio‐temporal resolutions (1‐km and 1‐hr). The fossil fuel (FF) emission estimates of 5.08 and 6.77 Gg/hr reported by the global and local emission inventories were optimized to 4.85 and 5.51 Gg/hr based on FTIR observations over this 7 month period, highlighting a convergence of posterior estimates. The modeled biogenic flux estimate of −0.14 Gg/hr was improved to −0.33 to −0.27 Gg/hr, respectively. It is worth noting that utilizing observations from three primary sites significantly enhanced the accuracy of estimates (13.6 29.2%) around the other four. Using FTIR posterior estimates can improve simulation with the OCO‐3 data set. OCO‐3 shows a similar decreasing trend in FF emissions (from 6.37 Gg/hr to 6.36 and 5.04 Gg/hr) as FTIR, but its correction trends for biogenic sources differ, changing from 0.37 to 0.48 Gg/hr. The primary reason is OCO‐3's lower temporal sampling density. Aligning the FTIR inversion timing with that of OCO‐3 yielded comparable corrections for FF emissions, yet discrepancies in biogenic emissions persisted, which can be attributed to their different sampling locations in the rural region and discrepancy in X observations. Our findings mark a significant step toward validating OCO‐3 and FTIR inversion results in metropolitan region.

Radiocarbon as a tracer of the fossil fraction of regional carbon monoxide emissions

Abstract Carbon monoxide (CO) is an atmospheric pollutant with a positive net warming effect on the climate. The magnitude of CO sources and the fraction of fossil vs biogenic sources are still uncertain and vary across emissions inventories. Measurements of radiocarbon (14C) in CO could potentially be used to investigate the sources of CO on a regional scale because fossil sources lack 14C and reduce the 14C/C ratio (Δ14C) of atmospheric CO more than biogenic sources. We use regional Lagrangian model simulations to investigate the utility of Δ14CO measurements for estimating the fossil fraction of CO emissions and evaluating bottom-up emissions estimates (United Kingdom Greenhouse Gas, UKGHG, and TNO Copernicus Atmosphere Monitoring Service, TNO) in London, UK. Due to the high Δ14CO in atmospheric CO from cosmogenic production, both fossil and biogenic CO emissions cause large reductions in Δ14CO regionally, with larger reductions for fossil than biogenic CO per ppb added. There is a strong seasonal variation in Δ14CO in background air and in the sensitivity of Δ14CO to fossil and biogenic emissions of CO. In the UK, the CO emissions estimate from TNO has a higher fraction from fossil fuels than UKGHG (72\% vs 67\%). This results in larger simulated decreases in Δ14C per ppb CO for TNO emissions. The simulated differences between UKGHG and TNO are likely to be easily detectable by current measurement precision, suggesting that Δ14CO measurements could be an effective tool to understand regional CO sources and assess bottom-up emissions estimates.

Comparative effects of micron-sized silicon sources and Si nanoparticles on growth, defense system and cadmium accumulation in wheat (Triticum aestivum L.) cultivated in Cd contaminated soil

Elevated levels of cadmium (Cd) in soils posesignificant challenges to global agricultural crop production. The potential of silicon (Si) nanoparticles (NPs) and biogenic Si sources of different sizes to mitigate Cd stress in wheat remains largely unexplored. A pot experiment was conducted to evaluate the effectiveness of various sizes of biogenic Si sources: rice husk biochar (RHB), sugarcane bagasse (SB), and rice straw (RS); categorized by particle size (<150 μm, 150–250 μm, and 250–1680 μm, denoted as S1, S2, and S3, respectively), and Si NPs on wheat growth and Cd accumulation. The application of RHB (<150 μm) significantly increased plant height (105 %), spike length (94 %), shoot dry weight (93 %), root dry weight (83 %), and grain weight (89 %) compared to the control. The RHBS1 treatment delivered the greatest reduction in the bioavailable fraction of soil Cd (-74 %), as well as Cd levels in roots (-85 %), shoots (-93 %), and grains (-97 %) compared to the polluted control. Additionally, RHB (<150 μm) showed the highest increase in antioxidant enzyme activities compared to the Cd-spiked treatment. Interestingly, the various biogenic Si sources have the potential to mitigate Cd stress in wheat plants. Further research is required to understand the underlying mechanisms and to investigate the effectiveness of different biogenic Si sources and particle sizes in alleviating Cd stress in crops.

Rethinking Nanoparticle Synthesis: A Sustainable Approach vs. Traditional Methods.

This review portrays a comparison between green protocols and conventional nanoparticle (NP) synthesis strategies, highlighting each method's advantages and limitations. Various top-down and bottom-up methods in NP synthesis are described in detail. The green chemistry principles are emphasized for designing safe processes for nanomaterial synthesis. Among the green biogenic sources plant extracts, vitamins, enzymes, polysaccharides, fungi (Molds and mushrooms), bacteria, yeast, algae, and lichens are discussed. Limitations in the reproducibility of green protocols in terms of availability of raw material, variation in synthetic protocol, and selection of material due to geographical differences are elaborated. Finally, a conclusion is drawn utilizing green chemical principles, & a circular economy strategy to minimize waste generation, offering a promising framework for the synthesis of NPs emphasizing sustainability.

Enhanced O3 concentration due to biogenic emissions during a hot summer in 2018 over the Tokyo metropolitan area, Japan

Abstract Photochemical ozone (O3) is an important chemical component in the atmosphere as an indicator of air pollution. Anthropogenic sources, such as domestic automobiles and industries, have been considered a main source of O3 especially in urban areas; however, recent emission regulations have led to declining trends in anthropogenic sources. Therefore, other sources, such as biogenic emissions, could be important in the near future. In addition, increasing temperatures caused by global warming will relate to increasing biogenic emissions. In this study, the role of biogenic volatile organic compounds (BVOC) on O3 concentration was focused. The target period was a hot summer in 2018 in Japan, and O3 concentration by simulating with and without biogenic emissions over the Tokyo metropolitan area was analyzed. The result clarified that around 20% (up to 63%) of O3 was produced from biogenic sources at high temperatures, even in the Tokyo metropolitan area. This study suggested that the biogenic sources should be paid attention to and taken into account in the regulation of anthropogenic emissions.

Characterization and source apportionment of ambient VOC concentrations: Assessing ozone formation potential in the Barnett shale oil and gas region

Atmospheric concentration and distribution of volatile organic compounds (VOC) are influenced by localized emissions and the fate and transport of secondary products formed through photochemical reactions. This study identifies the sources of VOC and its contribution to ozone formation in the Barnett Shale region, specifically in Denton, Texas, during the ozone seasons of 2015 through 2022. A total of 31 critical ozone precursor VOC compounds were observed at this site with an average total VOC concentration of 146 ppb-C, with n-alkanes from extensive oil and gas activities in the area contributing to 96.64% of the total VOC. Source apportionment using dispersion normalized positive matrix factorization (DN-PMF) identified eight VOC sources, with natural gas emissions (72%) being the dominant source followed by a combined source of natural gas combustion and aviation emissions (8.3%). Ozone formation potential (OFP) by VOC species was calculated using the propylene-equivalent concentration (propy-equiv) method. OFP calculated for all the apportioned sources highlighted that natural gas sources contributed significantly to the ozone formation in this region besides isoprene from biogenic sources and reactive alkenes from urban and industrial activities. This study underscores the critical role of slow-reacting n-alkanes along with other highly reactive VOC from urban and industrial sources influencing ambient air quality and it identifies strategies for mitigating ground-level ozone in urban areas affected by oil and gas extraction and production.

In-vitro and thermal stability study of bioglass synthesized from biogenic sources

In this work, the bioactive glasses are derived from biowaste resources such as corn husk ash, sugarcane leaves ashes, and eggshell powder via the melt quench method. The raw materials were melted in a platinum rhodium crucible at 1550 °C, followed by rapid cooling to obtain a glassy phase. In order to assess the in-vitro bioactivity, glasses were soaked in simulated body fluid at 37 °C for different time durations, i.e., 7,14, 21, and 28 days. Biocompatibility of these glasses was also tested on MG-63 cell lines using a 3-(4,5-dimethylthiazol-2-yl) 2,5-diphenyl tetrazolium bromide (MTT) assay test. X-ray diffraction, Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS) were used to analyze the hydroxyapatite (HAp) layer formation and the thermal stability of soaked samples. SEM micrographs showed the cauliflower and flakes type morphology of hydroxyapatite (HAp) on the glass surfaces after 7 days of soaking in SBF. The EDS analysis also confirmed the formation of a hydroxyapatite layer with a Ca/P ratio that varies from 1.6 to 3.9. MTT assay revealed the biocompatibility for different dosages (1, 2, 5, and 10 mg/ml) of the as-prepared glasses with MG-63 cell lines. The heat treatment of soaked glasses converts the amorphous HAp layer into a crystalline HAp layer, followed by its conversion in stable diopside as main and Ca2.589Mg0.41(PO4)2 as minor phase. The tested glasses exhibited good bioactivity and biocompatibility particularly higher CaO content glass, suggesting for use in bone regeneration applications.

Isotopic seasonality of fluvial-derived greenhouse gases implies active layer deepening

Abstract Climate change in the northern circumpolar regions is rapidly thawing organic-rich permafrost soils, releasing substantial dissolved CO2 and CH4 into fluvial systems. This mobilization impacts local ecosystems and global climate feedback loops, playing a crucial role in the Arctic carbon cycle. Here, we analyze the stable carbon (δ13C) and radiocarbon (F14C) isotopic composition of dissolved CO2 and CH4 in the Sagavanirktok and Kuparuk River watersheds on the North Slope, Alaska. By examining spatial and seasonal variations in these isotopic signatures, we identify patterns of carbon release and transport along the river continuum. We find consistent CO2 isotopic signatures across the fluvial continuum, reflecting a mixture of geogenic and biogenic sources integrated throughout the watershed. Bayesian mixing models further demonstrate a systematic depletion in 13C and 14C signatures of dissolved CO2 sources from spring to fall, indicating increasing contributions of aged carbon as the active layer deepens seasonally. This seasonal deepening allows percolating groundwater to access deeper, older soil horizons, transporting CO2 produced by aerobic and anaerobic soil respiration to streams and rivers. In contrast, we observe no clear relationships between the 13C and 14C compositions of dissolved CH4 and landscape properties. Given the reduced solubility of CH4, which facilitates outgassing and limits its transport in aquatic systems, the isotopic signatures are likely indicative of localized contributions from streambeds, adjacent water saturated soils, and lake outflows. Our study demonstrates that dissolved greenhouse gases are sensitive indicators of the release of old carbon from thawing permafrost and serve as early warning signals for permafrost carbon feedback. It establishes a crucial baseline for understanding their role in regional carbon cycling and Arctic environmental change.&amp;#xD;

Disentangling the effects of meteorology and emissions from anthropogenic and biogenic sources on the increased surface ozone in Eastern China

China's Clean Air Actions have substantially improved ambient PM2.5 air quality since 2013. However, ozone (O3) pollution in urban areas has worsened in recent years, particularly in the eastern region. The formation of O3 in these high emission areas is highly complex and regulated by numerous factors. Utilizing the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem), this study conducted a comprehensive analysis through nine sensitivity experiments for the years 2013 and 2017, aimed at disentangling the relative contributions of major factors (e.g., meteorological factors, anthropogenic emissions, biogenic emissions, and aerosol feedback mechanisms) to the observed O3 concentration trends in Jiangsu, a developed region of China with increasing trend of O3 level. Our findings indicate a pronounced increase in mean daily maximum 8-h average (MDA8) O3 levels in the economically vibrant southern Jiangsu, contrasted with a decrease in the less developed northern regions. The study identifies anthropogenic emissions change as the primary driver of O3 variations, with significant impacts also attributed to meteorological conditions and aerosol feedback effects, while biogenic emission shifts play a lesser role. In terms of meteorological factors, we discovered that the alteration in meteorological thermal factors (enhanced solar radiation and temperatures) in 2017, compared to 2013, exerted a more pronounced influence on the formation of O3 than the change in thermally driven dynamic factors (boundary layer height and wind speed). Moreover, the study observes a shift in O3 formation sensitivity from VOC-sensitive to transitional or NOX-sensitive regimes, signifying a notable transformation in the regional atmospheric chemistry conducive to O3 generation. Aerosol feedback effects, through complex pathways including photolysis rate alterations and modifications in the vertical O3 distribution, further compound the challenge of mitigating O3 levels. Our research underscores the necessity for adaptive, region-specific strategies to mitigate O3 pollution, providing potential insights for policymakers to formulate effective control measures.

Extraction and Physicochemical Characterization of Hydroxyapatites From Horse Humerus Bones of Different Ages (1, 3, 6, and 8 Years old) Calcined at Low Temperature.

The aim of this work is to investigate the changes in the physicochemical properties of hydroxyapatite (HAp) extracted from horse humerus bones of different ages (1, 3, 6, and 8 years) subjected to low temperature calcination (600°C). Thermal analysis revealed significant mass loss due to water, collagen, organic compounds, carbonates, and age-related magnesium out-diffusion. Higher fat content in older bones contributed to increased mass loss. Phosphorus content remained constant across age groups, while calcium and sodium showed age-related fluctuations. Magnesium levels decreased with age, emphasizing its importance for early bone development. The Ca/P ratio deviated from the stoichiometric values due to additional ions from biogenic sources. Infrared spectroscopy identified functional groups in carbonated HAp, with changes observed before and after calcination. The full width at half maximum (FWHM) of the 961 cm-1 band decreased with age, indicating improved crystalline quality. The molar absorption coefficients provided information on the changes in molecular concentration and emphasized the differences between the age groups. X-ray analysis revealed nanocrystalline HAp in all samples, with crystallite size increasing with age. Rietveld analysis showed that the lattice parameters were affected by the presence of organic material, but the lattice constants remained stable, confirming high crystallinity independent of age. TEM analysis confirmed nanocrystalline structures, with crystallite size increasing with age. SEM images showed the characteristic porosity of calcined HAp, with particle size correlating positively with age. Calcination at 600°C preserved the nanoscale properties and microcrystal formation. Raman spectroscopy confirmed the identity of HAp, with FWHM variations indicating age-related changes in crystalline quality. EHAp1 showed increased FWHM, indicating lower crystalline quality and increased trace element content.

Predominant biogenic contribution of dissolved inorganic carbon in karst rivers, Southwest China

Dissolved inorganic carbon (DIC) holds significant importance within river systems, particularly in karst regions. The concentration of DIC is intricately linked to both biological processes, such as the respiration of organic matter, and geological processes, notably the strength of carbonate weathering. This dual influence exerts a profound impact on regional and global carbon cycles. However, the precise biological and geological origins of DIC in karst rivers remain a subject of debate. In this study, we delineate the sources of DIC in a typical karst catchment (Houzhai catchment) through isotopic analysis coupled with water chemistry examination. The results showed that δ13CDIC and Δ14CDIC variations range from −14.0 ‰ to −7.3 ‰ and − 426 ‰ to −31 ‰, respectively, with average values of −10.5 ‰ and − 180 ‰. Results derived from the isotopic mixing model suggest that approximately 83 % of DIC emanates from the soil CO2, while 17 % originates from carbonate sources. This indicates that biological processes exert a greater influence on DIC within the study area compared to geological processes. Seasonal variation, exemplified by higher DOC concentrations and Δ14CDIC values, alongside with lower DIC concentrations and δ13CDIC values during the wet season indicate increased input from biogenic sources, closely related to temperature and moisture conditions. Our study underscores an unbalanced contribution from biogenic and geogenic sources in karst rivers, highlighting potential inaccuracies in past carbon sink flux calculations. The roles of biogenic and geogenic sources in the carbon cycling of karst rivers, as well as their responses to future climate change, warrant a reevaluation.

Origin of the Ca-phosphate inclusions in Ivory Coast and Australasian Muong-Nong-type tektites

Tektites are reduced (Fe2+) glasses formed by the quenching of molten material ejected from Earth’s surface as a result of a hypervelocity impact. The vast majority of tektites are usually homogeneous glasses, but rare samples containing mineral inclusions can provide insights about the source material, sample thermal history, and tektite formation process. Tektites from two distinct strewn fields presenting Ca-phosphate inclusions detected from anomalous magnetic susceptibility were studied: one sample from the Ivory Coast tektite (ICT) field ejected at 1.07 Ma from the Bosumtwi crater (10.5 km in size) in Ghana and two Muong Nong type samples from the Australasian tektite field (MN-AAT) ejected at 0.79 Ma from a crater possibly situated in southeast Asia. In ICT, Ca-phosphate inclusions are systematically embedded in lechatelierite (SiO2 glass). In MN-AAT Ca-phosphate are either embedded in lechatelierite or in Fe-rich glass forming schlieren. Multiscale petrographic characterization using correlative microscopy associating scanning electron microscopy, microprobe and, transmission electron microscopy reveals that rounded inclusions in ivoirite are composed of acicular Ca-phosphates (merrillite) embedded in an amorphous P-rich glass. In MN-AAT, inclusions consist mostly of single droplets of Fe-Mg rich Ca-phosphate (structurally related to apatite), but few droplets often forming an emulsion texture show a complex assemblage of apatite, magnetite, pyroxene, and spinel growing from a Pt-rich nucleus. Diffusion profile around lechatelierite domains reveals maximum temperatures greater than 2200–2400 °C in the impact plume of the Australasian tektite and the Ivory coast tektite. Heating time is of the order of seconds-tens of seconds rather than minutes as previously suggested (20 s for MN-AAT and 5 s for ICT). The number, the density, and the fact that inclusions are entirely crystallized in MN-AAT support relatively slow cooling rates (<200 °C/h), in comparison with the faster cooling rates (>2000 °C/h) indicated by the precipitation of amorphous P-rich glass in ICT. In both impact events, ejecta that had been heated to high temperatures did not remain in the vapor plume for an extended period of time and landed rapidly (within tens of seconds) at a relatively high temperature (>1000 °C) on the Earth’s surface.Phosphate inclusions systematically embedded in lechatelierite in ICT provide clues about the source material. It suggests that the parent material for these silica-rich inclusions is not conventional detrital quartz. Rather, parts of lechatelierite domains may be inherited from a biogenic source that could be consistent with tropical soil (source of the phosphor) and its biomass (silica of plant origin). The reduction process that tektites record during their formation may be explained by superficial material since forests can contain a sizable mass of carbon that can reduce iron in tektites and produce platinoid-rich metallic nuclei and the Fe3+/ΣFe gradient recorded by the dendritic spinels.

Using in situ measurements of δ13C in methane to investigate methane emissions from the western Canada sedimentary basin

During COP26, Canada joined the Global Methane Pledge aiming to reduce global methane (CH4) emissions by 30% below 2020 levels by 2030. Rapid reduction of anthropogenic CH4 emissions in the atmosphere is considered one of the most effective strategies to slow global warming in concert with carbon dioxide mitigation measures. In Canada, a large part of anthropogenic CH4 emissions can be attributed to the oil and gas industry in the Western Canada Sedimentary Basin (WCSB), which is the fourth largest reserve of fossil fuel in the world. Recent studies highlighted big discrepancies between CH4 emissions reported in Canada's National Inventory and emissions estimated with approaches using atmospheric measurements for the oil and gas sector. Measuring the isotopic signature of CH4 (δ13CH4) at different atmospheric monitoring stations and comparing these measurements to detailed archives of δ13CH4 from oil and gas wells and associated CH4 leaks in the WCSB could help better characterize the emissions from different CH4 sources over the region. In this study, we compare two independent sets of data: (1) thousands of δ13CH4 of samples from oil and gas production wells and their associated leaks (surface casing vents and ground migration) collected across the WCSB, and (2) atmospheric mixing ratios of CH4 and their δ13CH4 measured successively at three locations across this region between 2016 and 2020 combined with their atmospheric footprints modeled with HYSPLIT-STILT. We observed a gradient in the isotopic signatures of the oil and gas samples within the WCSB with δ13CH4 being more depleted in the Southeast than in the Northwest. The analysis of these samples showed that the isotopic signature of CH4 emitted by the production of fossil fuel depends on the geological formations from which it is extracted. Also, CH4 isotopic signatures vary more depending on the region where CH4 comes from than on the type of fossil fuel extracted (natural gas, oil, heavy oil, shale gas). The atmospheric measurements showed a strong seasonality of δ13CH4 at one of the atmospheric monitoring sites with isotopic signatures associated with thermogenic sources in winter and isotopic signatures associated with a mix of biogenic and thermogenic sources in summer. Using the δ13CH4 archive database from oil and gas samples, we estimated that 28–39 % of the CH4 emitted near this site in summer was coming from a biogenic source (most likely wetlands). Ultimately, atmospheric measurements collected during winter combined with their associated HYSPLIT-STILT footprints presented a spatial distribution of δ13CH4 over the WCSB comparable to the one observed in the archive database from the oil and gas sector, confirming that the oil and gas sector is the main source of CH4 in this region.

Urban sources of methane characterised by long-term eddy covariance observations in central Europe

Multiyear eddy covariance measurements of methane and carbon dioxide were performed in Innsbruck, Austria, a mid-sized European city in the Alps. Annual mean methane and carbon dioxide fluxes were on the order of 21.6 nmol/m2/s and 11.7 μmol/m2/s respectively. Methane fluxes increased significantly with decreasing temperature and showed a negligible weekend to weekday effect. Accompanying non-methane volatile organic compound (NMVOC) measurements provided additional constraints on urban methane sources during an intensive 6-week campaign in 2021. Positive matrix factorization analysis identified a unique and dominant methane source. Contributions from biomass burning and vehicle emissions were found to be small. No evidence was found for a large unknown biogenic source. A second intensive campaign in 2023 revealed that the measured ethane to methane enhancement in turbulent plumes showed a typical ratio of 5.2 ± 0.6%, close to the unburned ratio of natural gas (5%) in Austria. The analysis suggests that urban methane fluxes are likely to be dominated by end-user releases rather than natural gas leaks in the pipeline system. Long-term eddy flux observations also allowed identifying the existence of urban super-emitters, which brought area weighted methane fluxes up to 39 nmol/m2/s in 2022. On average, the 100 y global warming potential of methane emitted by natural gas combustion activities is 6% relative to the total urban CO2 flux, and ∼12% relative to CO2 emissions from the residential, commercial and public sectors in Innsbruck.

Role of the Biogenic Carbon Physicochemical Properties in the Manufacturing and Industrial Transferability of Mill Scale-Based Self-Reducing Briquettes

The recovery of iron contained in mill scale rather than iron ore can be considered a promising valorization pathway for this waste, especially if carried out through reduction using biogenic carbon sources. Nevertheless, the physicochemical properties of the latter may hinder the industrial transferability of such a pathway. In this work, the mechanical and metallurgical behavior of self-reduced briquettes composed of mill scale and four biogenic carbons (with increasing ratios of fixed carbon to volatile matter and ash) was studied. Each sample achieved mechanical performance above the benchmarks established for their application in metallurgical furnaces, although the presence of alkali compounds in the ash negatively affected the water resistance of the briquettes. In terms of metallurgical performance, although agglomeration successfully exploited the reduction by volatiles from 750 °C, full iron recovery and slag separation required an amount of fixed carbon higher than 6.93% and a heat treatment temperature of 1400 °C. Finally, the presence of Ca-, Al-, and Si- compounds in the ash was essential for the creation of a slag compatible with steelmaking processes and capable of retaining both phosphorus and sulfur, hence protecting the recovered iron.

The Influence of Green Manure Planting on the Spectroscopic Characteristics of Dissolved Organic Matter in Freshwater-Leached Saline–Alkali Soil at Different Depths

This study investigated the influence of green manure planting on the spectroscopic properties of dissolved organic matter (DOM) in saline–alkali soil under freshwater leaching conditions at different soil depths. The UV254, UV253/UV203, α300, α355, SUVA254, SUVA260, and SR ultraviolet parameters indicated reductions in the content of large molecular substances, benzene ring substitution degree, colored dissolved organic matter, aromaticity, and hydrophobic components in the soil leachate DOM with an increasing soil depth. Compared with the non-green manure treatment control, green manure planting mitigated the leaching of dissolved organic matter in soil during saline irrigation, with rape green manure demonstrating superior effectiveness. Utilizing three-dimensional fluorescence combined with parallel factor analysis, this study analyzed three fluorescent components of soil leachate DOM: C1 (visible-light fulvic acid), C2 (humic acid), and C3 (tyrosine-like protein). The combined contribution of the two humic substance components (C1 + C2) was approximately 70%, indicating the dominance of humic substances in leachate DOM. The fluorescence parameters of soil leachate DOM included an average of the fluorescence index (FI) values between 1.4 and 1.9, low humification index (HIX) values consistently below 4, and biological index (BIX) values ranging from 0.8 to 1.0, suggesting a mixed source, low humification degree, poor stability, and moderate self-source characteristics. Compared with the non-green manure treatment control, both the green manure treatments exhibited a relatively higher proportion of biogenic sources and humification degree in soil leachate DOM. This suggests that planting green manure can reduce the relative DOM content under freshwater leaching conditions, increase the proportion of biogenic sources in soil leachate DOM, and enhance soil humification. Planting rapeseed green manure can diminish the leaching of DOM from land sources and augment soil humification.

Evaluation of modelled versus observed non-methane volatile organic compounds at European Monitoring and Evaluation Programme sites in Europe

Abstract. Atmospheric volatile organic compounds (VOCs) constitute a wide range of species, acting as precursors to ozone and aerosol formation. Atmospheric chemistry and transport models (CTMs) are crucial to understanding the emissions, distribution, and impacts of VOCs. Given the uncertainties in VOC emissions, lack of evaluation studies, and recent changes in emissions, this work adapts the European Monitoring and Evaluation Programme Meteorological Synthesizing Centre – West (EMEP MSC-W) CTM to evaluate emission inventories in Europe. Here we undertake the first intensive model–measurement comparison of VOCs in 2 decades. The modelled surface concentrations are evaluated both spatially and temporally, using measurements from the regular EMEP monitoring network in 2018 and 2019, as well as a 2022 campaign. To achieve this, we utilised the UK National Atmospheric Emissions Inventory to derive explicit emission profiles for individual species and employed a tracer method to produce pure concentrations that are directly comparable to observations. The degree to which the modelled and measured VOCs agree varies depending on the specific species. The model successfully captures the overall spatial and temporal variations of major alkanes (e.g. ethane, n-butane) and unsaturated species (e.g. ethene, benzene) but less so for propane, i-butane, and ethyne. This discrepancy underscores potential issues in the boundary conditions for the latter species and in their primary emissions from, in particular, the solvent and road transport sectors. Specifically, potential missing propane emissions and issues with its boundary conditions are highlighted by large model underestimations and smaller propane-to-ethane ratios compared to the measurement. Meanwhile, both the model and measurements show strong linear correlations among butane isomers and among pentane isomers, indicating common sources for these pairs of isomers. However, modelled ratios of i-butane to n-butane and i-pentane to n-pentane are approximately one-third of the measured ratios, which is largely driven by significant emissions of n-butane and n-pentane from the solvent sector. This suggests issues with the speciation profile of the solvent sector, underrepresented contributions from transport and fuel evaporation sectors in current inventories, or both. Furthermore, the modelled ethene-to-ethyne and benzene-to-ethyne ratios differ significantly from measured ratios. The different model performance strongly points to shortcomings in the spatial and temporal patterns and magnitudes of ethyne emissions, especially during winter. For OVOCs, the modelled and measured concentrations of methanal and methylglyoxal show a good agreement, despite a moderate underestimation by the model in summer. This discrepancy could be attributed to an underestimation of contributions from biogenic sources or possibly a model overestimation of their photolytic loss in summer. However, the insufficiency of suitable measurements limits the evaluation of other OVOCs. Finally, model simulations employing the CAMS inventory show slightly better agreements with measurements than those using the Centre on Emission Inventories and Projections (CEIP) inventory. This enhancement is likely due to the CAMS inventory's detailed segmentation of the road transport sector, including its associated sub-sector-specific emission profiles. Given this improvement, alongside the previously mentioned concerns about the model's biased estimations of various VOC ratios, future efforts should focus on a more detailed breakdown of dominant emission sectors (e.g. solvents) and the refinement of their speciation profiles to improve model accuracy.

The impacts of photochemical loss on the source apportionment of ambient volatile organic compounds: A case study in Northern China

Volatile organic compounds (VOCs) play a crucial role as precursors in the formation of ozone (O3) and secondary PM2.5. It is well-established that some VOC species exhibit high photochemical reactivity, leading to deviations between measured and initial concentrations. Therefore, precise source apportionment must consider these photochemical reaction which called photochemical losses. The study was conducted in Langfang, which located in an important site for pollution transferring to Beijing, with August to October as the sampling period. The initial concentrations of the VOC species were estimated using a photochemical age-based parameterization method. The effects of photochemical losses on source apportionment were compared by the positive matrix factorization (PMF) results, based on observed and initial concentration data. The results showed that neglecting photochemical losses would result in an underestimation of VOCs concentration by 6.7% compared to the measured values obtained in this study. Furthermore, olefins and aromatic hydrocarbons were found to be the key components involved in photochemical reactions, with a photochemical loss rate of 28.3% and 23.7%, respectively. VOCs source apportionment revealed that the impact of photochemical loss on source apportionment was significant. Results indicated that biogenic sources (−6.8%) and solvent usage (−5.9%) made a higher contribution based on initial VOCs compared to measured VOCs, while gasoline vehicular emissions showed a lower contribution (+7.9%) than that observed from measured VOCs data. Analysis results also demonstrated that the combustion sources accounted for 14.2% based on measured concentrations and that accounted for 9.5% based on initial concentrations.

Effects of VOC emission reduction on atmospheric photochemistry and ozone concentrations during high-ozone episodes

We studied atmospheric volatile organic compounds (VOCs) characteristics and sources during fifteen high ozone (O3) episodes (daily 1-h maximum >100 ppbv and maximum 8-h average > 80 ppbv) in Nanjing, China, and used a photochemical box model to study the O3 formation sensitivity of VOCs, O3 photochemistry, radical budget, and reactivity for different emission reduction scenarios together with the base case ones. Overall, emission reduction from biogenic sources, followed by combustion sources, multiple sources, and solvent usage, had the major impacts on the O3 concentrations. According to photochemical box model simulations, isoprene was the most sensitive or influential VOC in the formation of O3, followed by ethylene, o-xylene, and cis-2-pentene. A 20.6 ± 11.7% concentration reduction of the sixteen most sensitive VOCs (SV16) for the production of O3 could bring the O3 concentration below the national standard level (daily 1-h maximum <100 ppbv). Besides, a 30% emission reduction from all the anthropogenic sources was more than enough to bring the O3 concentration below the national standard level. The total emission reduction of alkenes was always enough to bring the O3 concentration below the national standard level, which was not the case for aromatics under severe pollution conditions. The simulated OH reactivity analysis illustrates the importance of alkenes and aromatics, which account for about half of the total OH reactivity. The highest OH reactivity decreased due to the emission reduction for biogenic sources, followed by combustion and multiple sources. Alkenes played a major role in the OH, HO2, and RO2 radical's formation in the study area. The biggest drop in OH, HO2, and RO2 radical concentrations was noticed for biogenic emission reduction, followed by combustion and multiple sources. Due to the emission reduction from VOC sources, the highest O3 formation rates decreased for biogenic sources, followed by combustion and multiple sources. The acquired information is valuable to the scientific community and policymakers for formulating and implementing O3 pollution control strategies.

Distributions, sea-to-air fluxes, and biological consumption of carbon monoxide in the Bohai and Yellow Seas during winter

Carbon monoxide (CO) concentrations in the atmosphere and ocean are mainly influenced by anthropogenic inputs, abiotic photoproduction, biogenic sources, and bacterial consumption. This study, for the first time, investigated the distributions, sea-to-air fluxes, and microbial consumption rates of CO in the Bohai Sea (BS) and the Yellow Sea (YS) in winter to identify the main factors controlling CO distributions in both the atmosphere and seawater in colder temperature. Atmospheric CO mixing ratios ([CO]atm) and the concentrations of CO in surface seawater ([CO]surf) ranged from 176.8 to 1245.8 ppbv (mean value: 551.4 ± 214 ppbv) and from 0.49 to 3.1 nmol L−1 (mean value: 0.98 ± 0.55 nmol L−1), respectively. In addition, the spatial distribution of [CO]atm and [CO]surf showed that anthropogenic sources dominated the distribution of [CO]atm, but abiotic photoproduction processes were the main influencers of the distribution of [CO]surf. The surface water at most sampling stations was supersaturated with CO, with a mean saturation factor of 1.9, and the sea-to-air fluxes of CO were estimated to range from −13.88 to 123.88 nmol m−2 h−1 (12.59 ± 21.32 nmol m−2 h−1), suggesting that the BS and the YS were the source of atmospheric CO, and were estimated to contribute 0.009% to 1.4% to the global ocean emission. Microbial consumption experiments indicated that the microbial CO consumption rate constants (Kbio) ranged from 0.15 to 2.14 h−1, and showed that CO concentrations decreased exponentially with incubation time, suggesting that anaerobic CO consumption would limit CO accumulation in winter, thereby affecting the flux of [CO]surf to [CO]atm.