Carbon Profiles Research Articles

Degradation of melamine in aqueous systems by vacuum UV-(VUV-) photolysis. An alternative to photocatalysis

Abstract VUV-irradiation experiments with aqueous solutions of melamine and related triazine derivatives were carried out in the presence or absence of molecular oxygen. Substrate degradation, total organic carbon and evolution profiles of intermediates were monitored. Relevant mineralization of the substrates was observed, in particular for melamine, its extent depending on the concentration of dissolved O2 and on the number of amino substituents at the s-triazine moiety of the substrate. In all experiments, cyanuric acid was found to be the only persistent final product. Experimental results indicate that the route of reactions leading to mineralization is independent of that leading to amino group substitution. Mechanistic hypotheses are proposed and compared with findings coming from TiO2-based photocatalysis.

Comparing and modeling sedimentary profiles of elemental carbon and polycyclic aromatic hydrocarbons between early- and newly-urbanized areas in Shanghai

Rapid urbanization created unique urban environment with a characteristic of dramatic modification of land cover, consequently causing profound perturbations in the transport and fate of pollutants in urban ecosystem. Taking a hyper-urbanization city (Shanghai) as an example to reveal the influence of urbanization development on pollutant footprint, this study reconstructed and compared historical evolutions of elemental carbon (EC) and polycyclic aromatic hydrocarbons (PAHs) based on two lake sediment cores (DSL: Dianshan Lake; LXL: Luxun Lake) from early- and newly-urbanized areas, respectively. Historical fluxes of EC and total PAH (Σ16PAHs) showed similar and sharply fluctuant increases occurring after the 1950s in the DSL core later than the LXL core after the 1900s. In modern times (after 2000), the mean fluxes of EC and Σ16PAHs in the LXL core were 2.68- and 1.38-fold greater than those in the DSL core, respectively, indicating the stronger influence from more intensive human activities and longer industrial history in early urbanized area. Based on the significant correlations among socioeconomic factors with EC and Σ16PAH fluxes, the extended STIRPAT (stochastic impacts by regression on population, affluence and technology) models were successfully constructed, revealing that significance of these driving factors were in the order of population > the proportion of heavy industry > coal consumption > gross domestic product (GDP) per capita > vehicle amount. In general, the obvious discrepancy in historical stage and intensity of sedimentary EC and PAH accumulations implied that some newly fast-developing cities still have a chance to adjust urban development strategy to avoid more serious pollution.

Intensified oceanic circulation during Early Carboniferous cooling events: Evidence from carbon and nitrogen isotopes

The Early Carboniferous was a climatic transition interval from a mid-Paleozoic greenhouse world into the Late Paleozoic Ice Age. It was marked by a long-term cooling trend that was punctuated by short glaciations in the Tournaisian and Visean (early to mid-Early Carboniferous). Here, we generated organic carbon and nitrogen isotope profiles for two widely separated Lower Carboniferous sections (Arrow Canyon Range, Nevada, and Namur-Dinant Basin, Belgium) in order to assess the global nature and timing of changes in the carbon‑nitrogen cycles linked to oceanic productivity and redox conditions during this climatic transition interval. The carbon and nitrogen isotope profiles of both study sections record major perturbations during the mid-Tournaisian and Visean. A mid-Tournaisian event (TICE) is marked by increases in δ13Ccarb, δ13Corg, and δ15Nbulk at Arrow Canyon (from +0.6 to +7.0‰, −25.2 to −23.7‰, and –0.6 to +8.9‰, respectively) and Namur-Dinant (from −0.3 to +4.7‰, −27.9‰ to −22.2‰, and –5.7 to +5.2‰, respectively). An early Visean event (VICE; named herein) is marked by increases in δ13Ccarb, δ13Corg, and δ15Nbulk at Arrow Canyon (from −0.6 to +3.1‰, −28.4 to −23.6‰, and +1.4 to +9.4‰, respectively) and Namur-Dinant (from +2.1 to +4.3‰, −26.7 to −25.0‰, and –1.4 to +3.3‰, respectively). The positive excursions in all three isotopic records during these events are consistent with increased fractional burial of organic carbon and enhanced denitrification, implying intensification of marine productivity and expansion of hypoxia in the global ocean. Given that each event coincided with lowering of sea-surface temperatures and increased glaciation (as documented from published conodont δ18O and sea-level records), we hypothesize that global cooling led to intensified oceanic circulation and upwelling on continental margins, triggering increased marine productivity and attendant redox changes within the affected upwelling zones. Our results provide new insights into changes in Early Carboniferous oceanic conditions in response to the initial stages of cooling leading into the Late Paleozoic Ice Age.

Hybrid Input-Output Analysis of Embodied Carbon and Construction Cost Differences between New-Build and Refurbished Projects

Refurbishing buildings helps reduce waste, and limiting the amount of embodied carbon in buildings helps minimize the damaging impacts of climate change through lower CO2 emissions. The analysis of embodied carbon is based on the concept of life cycle assessment (LCA). LCA is a systematic tool to evaluate the environmental impacts of a product, technology, or service through all stages of its life cycle. This study investigates the embodied carbon footprint of both new-build and refurbished buildings to determine the embodied carbon profile and its relationship to both embodied energy and construction cost. It recognizes that changes in the fuel mix for electricity generation play an important role in embodied carbon impacts in different countries. The empirical findings for Hong Kong suggest that mean embodied carbon for refurbished buildings is 33–39% lower than new-build projects, and the cost for refurbished buildings is 22–50% lower than new-build projects (per square meter of floor area). Embodied carbon ranges from 645–1059 kgCO2e/m2 for new-build and 294–655 kgCO2e/m2 for refurbished projects, which is in keeping with other studies outside Hong Kong. However, values of embodied carbon and cost for refurbished projects in this study have a higher coefficient of variation than their new-build counterparts. It is argued that it is preferable to estimate embodied energy and then convert to embodied carbon (rather than estimate embodied carbon directly), as carbon is both time and location specific. A very strong linear relationship is also observed between embodied energy and construction cost that can be used to predict the former, given the latter. This study provides a framework whereby comparisons can be made between new-build and refurbished projects on the basis of embodied carbon and related construction cost differentials into the future, helping to make informed decisions about which strategy to pursue.

Prediction of Carbon Profiles and Alloy Design in Vacuum Carburizing Steels Based on Thermodynamic Calculation

Prediction of Carbon Profiles and Alloy Design in Vacuum Carburizing Steels Based on Thermodynamic Calculation

Concentrations and congener group profiles of short- and medium-chain chlorinated paraffins in animal feed materials

Chlorinated paraffins (CPs) are ubiquitous environmental pollutants that are lipophilic and can accumulate in the food chain. Animal-derived products are predominant contributors to human CP exposure. CPs in animal feed might accumulate in domestic animals through dietary exposure, leading to potential contamination of animal-derived food products and human health risks. However, information on the presence of CPs in animal feed materials is scarce. In this study, 16 animal feed material samples were collected in China in 2016. Thirteen of the samples were of animal origin and three were of plant origin. The concentrations and carbon and chlorine congener group profiles of shortchain chlorinated paraffins (SCCPs) and medium-chain chlorinated paraffins (MCCPs) in these animal feed materials were investigated. The concentrations of SCCPs were higher than those of MCCPs in all of the samples. The SCCP concentration range was 120 to 1700 ng/g (mean 640 ng/g), and the MCCP concentration range was 6.4 to 260 ng/g (mean 78 ng/g). Fish meal had the highest SCCP and MCCP concentrations. The lowest SCCP and MCCP concentrations were detected in peanut meal and whey powder, respectively. The concentrations of SCCPs and MCCPs varied among the types of animal feed materials. SCCP and MCCP concentrations also varied among samples of the same type of animal feed material. Relatively high concentrations of SCCPs and MCCPs were detected in feed materials of animal origin. The predominant congener groups in the animal feed materials were C10-11Cl6-7 for SCCPs and C14Cl7 for MCCPs. The carbon and chlorine congener group profiles of SCCPs indicated that SCCP contamination in the animal feed materials might arise from commercial CP mixtures.

Vertical profiles of sedimentary polycyclic aromatic hydrocarbons and black carbon in the Gulf of Gdańsk (Poland) and Oslofjord/Drammensfjord (Norway), and their relation to regional energy transitions

The analysis of undisturbed sediment cores is a powerful tool for understanding spatial and temporal impacts of anthropogenic emissions from the energy and transport sectors at a regional scale. The spatial and vertical distribution of polycyclic aromatic hydrocarbons (PAHs) and black carbon (BC) were determined in 12 cores of recent (up to 20cm long) sediments from the Gulf of Gdańsk in Poland, and Oslofjord/Drammensfjord in Norway. The Σ12PAHs levels in individual sediment layers varied from 250 to 4500ng/g d.w. in the Gulf of Gdańsk, and from 210 to 4580ng/g d.w. in the Norwegian fjords. Analysis of PAH ratios indicates that PAHs in both studied areas originated mainly from pyrogenic sources. The BC concentrations in sediments were up to 0.9% and were generally higher in the Gulf of Gdańsk (mean - 0.39%) than in Oslofjord/Drammensfjord (mean - 0.19%). The deposition history of anthropogenic emissions over the last 100years was reconstructed based on the analysis of dated and well-laminated sediment cores from two stations from the Gulf of Gdańsk and two stations from the Norwegian fjords. The evolution in energy structure was especially evident in the Oslofjord, where transition from fossil fuel combustion to hydropower after 1960 coincided with a sharp decrease in sedimentary PAHs. Despite significant changes in the economic development in Poland, temporal patterns in PAH concentrations/profiles in the Gulf of Gdańsk were not as obvious. The historical PAH trends in the Gulf of Gdańsk may be related to the overwhelming PAH inputs from domestic combustion of solid fuels (coal, wood) for heating purposes. The implementation of legislation and other activities addressed to restrict the use of solid fuels in residential heating should reduce PAH emissions.

The distribution of active iron-cycling bacteria in marine and freshwater sediments is decoupled from geochemical gradients.

Microaerophilic, phototrophic and nitrate-reducing Fe(II)-oxidizers co-exist in coastal marine and littoral freshwater sediments. However, the in situ abundance, distribution and diversity of metabolically active Fe(II)-oxidizers remained largely unexplored. Here, we characterized the microbial community composition at the oxic-anoxic interface of littoral freshwater (Lake Constance, Germany) and coastal marine sediments (Kalø Vig and Norsminde Fjord, Denmark) using DNA-/RNA-based next-generation 16S rRNA (gene) amplicon sequencing. All three physiological groups of neutrophilic Fe(II)-oxidizing bacteria were found to be active in marine and freshwater sediments, revealing up to 0.2% anoxygenic photoferrotrophs (e.g., Rhodopseudomonas, Rhodobacter, Chlorobium), 0.1% microaerophilic Fe(II)-oxidizers (e.g., Mariprofundus, Hyphomonas, Gallionella) and 0.3% nitrate-reducing Fe(II)-oxidizers (e.g., Thiobacillus, Pseudomonas, Denitromonas, Hoeflea). Active Fe(III)-reducing bacteria (e.g., Shewanella, Geobacter) were most abundant (up to 2.8%) in marine sediments and co-occurred with cable bacteria (up to 4.5%). Geochemical profiles of Fe(III), Fe(II), O2 , light, nitrate and total organic carbon revealed a redox stratification of the sediments and explained 75%-85% of the vertical distribution of microbial taxa, while active Fe-cycling bacteria were found to be decoupled from geochemical gradients. We suggest that metabolic flexibility, microniches in the sediments, or interrelationships with cable bacteria might explain the distribution patterns of active Fe-cycling bacteria.

Mixed-unit hybrid life cycle assessment applied to the recycling of construction materials

The construction industry contributes around 18% of greenhouse gas emissions, 40% of depletion of natural resources, and 25% of wastes globally. To reduce these impacts, construction industries can adopt low-carbon alternatives for construction materials and waste minimisation strategies, including the recycling of construction and demolition waste. However, a comprehensive understanding of the full life cycle carbon profile of low-carbon and recyclable construction materials is required to accurately assess the efficacy of decarbonisation strategies in the built environment. Despite recent progress in hybrid life cycle assessment (hybrid LCA) methods, some weaknesses remain with respect to the inherent uncertainty relating to price variations and aggregated sectors that are unable to provide detailed waste-specific information in hybrid LCA. Furthermore, attributional, hybrid LCA for a functional unit does not reflect the actual, economy-wide physical flows of materials in a real economy. In this study, a mixed-unit hybrid LCA approach based on a combination of process life cycle inventory, input–output, and material flow data is used to model the economy-wide potential use of recycled construction materials in Australia. A comparison between methods of life cycle emissions of geopolymer concrete revealed that the mixed-unit hybrid LCA approach produced a more accurate and Australian-specific result. The usefulness of the proposed mixed-unit IO model is demonstrated through quantifying the cradle-to-gate embodied emissions of recycled construction materials and by-products utilised in concrete and steel sectors in Australia. The results yield a 1% reduction when recycled concrete aggregate completely replaces natural aggregate in both ordinary Portland cement and geopolymer concrete. Greenhouse gas emissions reduction of 30% is quantified for geopolymer concrete using recycled concrete aggregate compared with ordinary Portland cement concrete utilising natural aggregate and 43% is estimated for electric arc furnace route using iron and steel scrap compared with basic oxygen furnace route. The method merges physical and monetary units of industrial systems related to low-carbon alternatives and recycled construction materials to enable the calculations of embodied carbon with improved accuracy. The results of this study can help inform decarbonisation strategies in the built environment sector.

Carbon diagenesis in different sedimentary environments of the subtropical Beibu Gulf, South China Sea

Abstract The depositional environment in the subtropical Beibu Gulf area is highly complex, and the sediments accumulate under specific combinations of hydrodynamics, physiography and sediment sources. In the present study, six sedimentary gravity cores were collected from three different depositional zones of the Beibu Gulf. We measured the geochemical and carbon isotopic compositions of pore water and solid sediments to characterize the benthic early diagenesis of carbon. Our results indicate that marine organic matter is rapidly remineralized in delta deposits and the Central Beibu Gulf. Terrestrial organic matter, however, seem to be more important at the bottom of the Central and Northern Coastal Beibu Gulf, which probably formed in an estuarine or fluvial environment before the Holocene or Pleistocene transgression. Organic matter degradation via microbial sulfate reduction is the most important source for isotopically light DIC (dissolved inorganic carbon) added to the pore waters at most sites. In the Central Beibu Gulf, however, the carbon isotope signatures of DIC indicate an additional source of light carbon and pore water profiles exhibit a characteristic pattern reflecting the occurrence of the anaerobic oxidation of methane. Moreover, we find that the pore water δ13Cadded is greater than the δ13C of total organic carbon net loss in solid sediments in the zones with relatively strong current environments. This result hints that the frequent physical reworking and reoxidation of bottom deposits are likely key factors controlling carbon isotopic fractionation between the sedimentary organic carbon and DIC. Overall, our results further reveal that carbon sources and transformations in the sediments sensitively respond to changes in depositional conditions. Pore water modeling give strong hints for non-steady state processes impacting diagenesis at several sites.

Profile of organic carbon and nitrogen removal by a continuous flowing conventional activated sludge reactor with pulse aeration

Abstract This study aimed to investigate the effect of pulse aeration (on/off time 5/10 min) on the pollutants removal efficiencies and on the evolution of the denitrifying bacteria communities of a continuous flowing completely mixed activated sludge reactor. Organic matters and nitrogen removal were evaluated and the denitrifying bacteria community structure was analyzed by MiSeq sequencing technology. Results showed that the TOC removal rates were steadily above 81.6% and the NH4+-N removal rates were 92.1% ± 0.5% when the pulse aerated activated sludge reactor was operated with the optimized pulse aeration cycle (PAC) of 5/10 min. There was no significant impact on both TOC and NH4+-N removal efficiencies, while the average TN removal rate of the pulse aerated reactor (58.4%) was significantly higher than that of the constantly aerated one (30.6%). The removal efficiencies of both organics and nitrogen were stable during the 60-day acclimation period regardless of the changing DO concentration fluctuated in pulse mode. Although the denitrifier bacterial compositions varied between the pulse aerated group and the constantly aerated group, the denitrifier community richness and diversity were similar. Boost of the TN removal was mainly due to the anoxic denitrifying environment provided by the non-aerated phase in each PAC.

Alloying Factors and Parameter of Alloying Elements for Carbon and Nitrogen Uptake during Carbonitriding as Basis for Simulation

Abstract Carbonitriding serves to increase the strength and wear properties of steel components. The carbon and nitrogen concentration and the depth distribution decisively determine the resulting properties. Optimal profiles create an ideal microstructure of martensite, residual austenite, finely distributed nitrides, carbonitrides and inherent compressive stress in the surface zone. The reliability of carbonitriding heat treatment process is strongly dependent on the possibilities of process control. Previous investigations aimed at measuring the nitrogen potential of the atmosphere by means of an ammonia sensor in the exhaust gas as well as by a wire sensor. Carbon potential is conventionally controlled using an oxygen probe. In order to further increase the process reliability of carbonitriding, simulation of the carbon and nitrogen profiles and of any precipitation of carbides and nitrides are necessary. The first step is the determination of interdependent alloying influences on the carbon and nitrogen contents. The carbon and nitrogen activities in the atmosphere and the alloy surface are near equilibrium after long-time carbonitriding. Depending on the composition of the material, significantly different effects can be described. These influences must be considered. In addition to the reached equilibrium content, the diffusion, the position of phase boundaries in the phase diagrams and the formation of precipitation with influence of carbon and nitrogen as well as interactions with other alloying elements are to be worked out in order to further develop controlled carbonitriding for the reliable adjustment of the heat treatment results.

Changes in vegetation type on the Chinese Loess Plateau since 75 ka related to East Asian Summer Monsoon variation

Floral communities in terrestrial habitats such as steppes are highly sensitive to regional climate changes. Here, we generated carbon and nitrogen isotope profiles for soil organic matter (SOM) in the Weinan loess-paleosol section in order to investigate changes in floral communities on the Chinese Loess Plateau (CLP) and their relationship to climate variation since 75 ka. δ13CSOM at Weinan ranges from −23.6 to −18.0‰ and δ15NSOM ranges from +3.4 to +5.5‰. Modeling based on the δ13CSOM record suggests that the proportion of C4 plants (%C4) has varied from lower during cold intervals (with minima of 24–32% at 73.1 ka, 20.9 ka (LGM), and 0.6 ka) to higher during warm intervals (with maxima of 62–64% at 53.0 ka and 8.2 ka). The δ13CSOM and δ15NSOM profiles are strongly correlated (r = +0.82; p(α) <0.001), suggesting that the N-isotope composition of SOM was also largely controlled by inputs of C4 versus C3 plants, consistent with known patterns of N-isotope variation among modern plants. The %C4 profile exhibits significant covariation with reconstructed mean annual temperatures (MAT) (r = +0.42; p(α) <0.001), mean annual precipitation (MAP) (r = +0.42; p(α) <0.001), and summer monsoon intensity (r = +0.50; p(α) <0.001), suggesting that paleovegetation was controlled by each of these climate variables to a degree. Comparing the Weinan record to SOM profiles across the CLP region, we identified three zones of varying monsoonal influence, with the East Asian Summer Monsoon (EASM) exerting the strongest influence on the southeastern margin of the CLP, and the East Asian Winter Monsoon (EAWM) greater influence on its northwestern margin. This paper provides new insights into deciphering paleovegetation patterns and their links to paleoclimate change on the basis of paired C- and N-isotope records.

The early Earth geochemical and isotope record of serpentinizing environments from Archean stichtite (Mg6Cr2(OH)16[CO3]·4H2O)

A record of the conditions and duration of Archean serpentinization is preserved as chemical, isotopic, and textural properties of the magnesium-chromium hydroxycarbonate mineral stichtite. This provides a window into the conditions associated with a potentially habitable environment on early Earth and Mars. Stichtite is associated with Archean chromite-rich serpentinite rocks of South Africa, Western Australia and Southern India. Stichtite compositions range within the Cr-Fe-Al hydrotalcite group, with trends unique to each discrete serpentinite host body. Elemental and textural analysis of stichtite-associated chromite indicates that stichtite forms in fore-arc/layered intrusive/boninite setting rocks through interaction of chromite and methane-rich serpentinizing fluids. The degree to which chromite is replaced by stichtite is inferred to correlate with the length of time that the host rocks spent within the “stichtite window.” Carbon stable-isotope values of Archean stichtite suggest carbon sourcing from marine kerogen with minor marine dissolved inorganic carbonate in most samples, as opposed to the strongly kerogen-dominated Phanerozoic stichtite. The carbon and hydrogen stable isotope profile of Archean stichtite ranges from the methane fields of active serpentinizing zones, to geothermal, with trends suggestive of methane oxidation rather than the substrate depletion noted in Phanerozoic stichtite. Thus, isotope values of stichtite appear to record oceanic oxygenation levels. The association of the stichtite 2H polytype (nee barbertonite) with aragonite ± antigorite suggests this is a higher pressure/temperature polytype of stichtite. Reaction textures, isotopic values, and qualitative mineral thermobarometric indicators indicate that stichtite forms during serpentinization in a methane/H2-rich environment within fluid conduits, ranging from near the surface, to depths where pressure is up to 2.8 GPa and temperature is up to ∼300 °C.

Multiproxy geochemical and isotope stratigraphy records of a Neoproterozoic Oxygenation Event in the Ediacaran Sete Lagoas cap carbonate, Bambuí Group, Brazil

Abstract In order to investigate the geochemical responses of Earth's oceans and atmosphere after a Snowball glaciation, we studied an Ediacaran cap carbonate profile pertaining to the base of the Bambui Group (Sete Lagoas Formation) in the central portion of the Sao Francisco basin, east central Brazil, for trace elements (including REE + Y) and C, O, Sr, Nd, Pb and Cr isotopes. The section can be divided in three portions, from bottom to top: (i) a two-meter thick cap dolostone preserving a drop of δ13C values from −3.8 to −4.2‰, overlain by (ii) a ca. 123 meters-thick, reddish limestone rhythmite deposited in a tidal flat, with an important isotopic shift observed at 60 m, with δ13C values below averaging −5‰ and above shifting abruptly to around −0.5‰; and (iii) a topmost ca. 2 meters thick black calcarenite with positive δ13C (+0.9‰) and 87Sr/86Sr = 0.7076. A new, tightly constrained Pb-Pb whole rock isochron of 608 ± 19 Ma provides additional support for deposition during the early Ediacaran. We put forward a model for the deposition of the Sete Lagoas cap carbonate which starts with the glacial aftermath, when the thin cap dolostone and the basal reddish limestone were deposited due to glacier melting and subsequent sea level rise, with important mixing of glacial meltwaters with anoxic bottom waters. A decreasing trend of eNd(630Ma) values, from −6 at the base to ca. −8 at the 60 meters-mark, indicates continued input of continentally-derived detrital particles to the basin. During this phase, intermittent subaerial exposure was responsible for meteoric diagenetic alteration, which shifted 87Sr/86Sr to higher values (>0.710) and δ18O towards lower values. Towards the top of the sequence, the late postglacial succession is marked by marine-like REE + Y (Y/Ho = ca. 46) and lower Al and Mn contents, reflecting the diminishing of glacial meltwater input, a renewed sea level rise, and a change to more distal depositional environments, away from the coastal lines. At this moment, a vigorous input of U(VI) and 53Cr-rich Cr(VI), reflecting in a sharp rise of U/Th ratios and positive δ53Cr, suggests that fully oxygenated conditions finally predominated in post-glacial surface waters in the middle to late Ediacaran. Our results add to a growing body of data for other Ediacaran cap carbonate sequences around the world (e.g. Otavi Group, Namibia and Doushantuo Formation, China) that suggest that after ca 1 Ga of anoxia (the “Boring Billion”) following the first Great Oxygenation Event, the oceans became increasingly oxygenated after the end of the Marinoan glaciation ca. 635 Ma ago, ultimately leading to the explosion of complex macroscopic life that followed this Neoproterozoic Oxygenation Event.

Carbon Geochemistry of Gas Hydrate‐associated Sediments in the Southwestern Taiwan Basin

AbstractMarine gas hydrates, one of the largest methane reservoirs on Earth, may greatly affect the deep sea sedimentary environment and biogeochemistry; however, the carbon geochemistry in gas hydrate‐bearing sediments is poorly understood. In this study, we investigated the carbon variables in sediment core 973‐3 from the southwestern Taiwan Basin in the South China Sea to understand the effect of environmental factors and archaeal communities on carbon geochemistry. The carbon profiles suggest the methanogenesis with the incerase of dissolved inorganic carbon (DIC) and high total organic carbon (TOC) (mean = 0.46%) originated from terrigenous organic matter (mean δ13CTOC value of −23.6±) driven by the abundant methanogen ‘Methanosaeta and Methanomicrobiales'. The active anaerobic oxidation of methane is characterized by the increase of DIC and inorganic carbon (IC), and the depleted δ13CIC, coupled with the increase of TOC and the decrease of δ13CTOC values owing to the methanotroph ‘Methanosarcinales/ANME’ in 430–840 cm. Environmental factors and archaeal communities in core 973‐3 are significantly correlated to carbon variables owing to methane production and oxidation. Our results indicate that the carbon geochemical characteristics are obviously responding to the formation and decomposition of gas hydrates. Furthermore, pH, Eh and grain size, and Methanosaeta greatly affect the carbon geochemistry in gas hydrate‐associated sediments.

Use of tomography to understand the influence of preconditioning on carbonation tests in cement-based materials

Recognition of the rising amount of atmospheric CO2 has brought renewed interest in understanding the effects of carbonation on reinforced concrete performance. In laboratory testing, the specimens must be preconditioned to effectively study carbonation. This paper studied the influence of several preconditioning schemes on the carbonation profiles of cement paste specimens subjected to accelerated carbonation tests. The evolution of microstructure and moisture during carbonation were investigated accordingly. Bulk of the work was based on an extended X-ray attenuation method (XRAM), which relied on X-ray computed tomography (CT). A novel method was introduced to evaluate the extent of damage due to drying. Based on extent of damage, the paper recommends standard-cured specimens for carbonation tests as compared to water-cured specimens. Also, when comparing between oven drying and mass balancing, the latter was shown to be more suitable, as the inner moisture distribution becomes more uniform after this drying protocol, and less fluctuation of humidity will occur during carbonation.

Carbonations and carbonate profile forming processes of rendzinas of the Podilski Tovtry

The peculiarities of content and profile distribution of carbonates in rendzinas and soil-forming rocks of the Podilski Tovtry are investigated. It has been determined that the predominant process of weathering of carbonate rocks is a chemical dissolution, in which carbonates are converted into bicarbonates and, in the case of washing water regime, are applied from the soil (the process of decarbonization) and mechanical grinding and destruction of the remaining carbonate inclusions in the process of soil cultivation. The dissolution of carbonate rocks causes accumulation in the soil profile of an insoluble residue, the intensity of which depends on the composition of carbonate rocks, the rate of filtration of aqueous solutions, their aggressiveness and the concentration of destructive substances. The most intensive such accumulation occurs in acidic medium, at a low rate of infiltration of solutions and at high concentrations of CO2. It was established that the highest proportion of CaCO3 is characterized by lithotamium limestone (up to 90–93 %), and the lowest – carbonate polygenetic loams (up to 35–40 %). The feature of the profile distribution of the content of carbonates in rendzinas is its gradual growth in the upper part of the soil profile and rapid in the middle and lower parts. It is determined that the rendzinas of the Podilski Tovtry carbonates are represented predominantly in the form of wreckage of initial soil-forming rocks of different sizes and shapes, as well as amorphous solid-phase crude and finely dispersed products of weathering in the form of powdery and powdery carbonate dusting. It is established that in dense crystallized lithotamium limestones of the main strand, the carbonate mass weakly passes moisture, and the main process of weathering occurs due to surface corrosion. The accumulation of secondary carbonates in the form of mycelium and veins is characteristic on the slopes of the Tovtry (mostly in brown rendzinas and pararendzinas), due to the vertical and lateral migration flows of the dissolved forms of CaCO3. Key words: rendzinas, Podilski Tovtry, carbonates, carbonate profile.

Concentration profile of elemental and organic carbon and personal exposure to other pollutants from brick kilns in Durango, Mexico

Emission factors and personal exposure measurements were obtained in the working environment of a brick kiln yard in the municipality of Victoria de Durango, Mexico. Two kinds of kiln were evaluated; one was a fixed traditional kiln (FTK); the other was a local variation of an improved kiln called the ecological Marquez brick kiln (MK2). To distinguish it from the original design, we call it the Marquez kiln Durango (MKD). Ambient emission gases of carbon dioxide (CO2), carbon monoxide (CO), methane (CH4), and non-methane hydrocarbons (NMHC) were continuously followed using Fourier transform infrared spectrophotometry (FTIR). Elemental carbon (EC) and organic carbon (OC) ambient emissions were sampled on quartz filters and analyzed by chemical coulombimetry. Personal exposure to CO was continuously followed using portable monitors, and personal exposure to inhalable particles with diameters of generally 2.5 μm and smaller (PM2.5) was obtained using Teflon filters in portable particle samplers followed by gravimetric analysis. Results show that the FTK emits more PM2.5, EC, and OC per cooking stage than the MKD. In terms of PM2.5 emission factors, relative to the FTK, the MK2 is 61% smaller and the MKD emission factor is 39% smaller. Against our expectations, the MKD showed higher work environment exposure levels. This is due to the untested changes to the original MK2 design and a mismanagement of the operation processes. Personal exposure to CO and PM2.5 of local brick kiln workers was about three times higher than indoor exposure from the use of three-stone wood cookstoves in Mexico. The analysis of emission plumes from FTK and MKD using a coupled emission model dispersion model allowed us to evaluate the impacts, transport, and deposition area of the particle matter in the area surrounding Durango Brickyard (DB).

Mapa digital del perfil del carbono orgánico en los suelos de Andalucía, España

Armas, D., Guevara, M., Alcaraz-Segura, D., Vargas, R., Soriano-Luna, M.A., Durante, P., Oyonarte, C. 2017. Digital map of the organic carbon profile in the soils of Andalusia, Spain. Ecosistemas 26(3):80-88. Doi.: 10.7818/ECOS.2017.26-3.10 To know and understand the spatial distribution of soil organic carbon (SOC) is the first step for management of this important pool in the global carbon cycle, and to develop actions to address climate change. The objective of this work was to generate maps of percent SOC across Andalucia through the use of consistent models, quantifying the associated uncertainty and identify controls of the spatial variability. We used a legacy soil profile collection with 1500 soil profiles and 20 environmental covariates as prediction factors for climate, topography, and ecosystem functional attributes related to the dynamic of primary production. A combination of linear models and an ensemble of regression trees coupled with geostatistics was used to estimate the spatial distribution (horizontal and vertical) of SOC, maps of SOC distribution across six soil depths (0-5, 5-15, 15-30, 30-60, 60-100 y 100-200 cm). Explained variance of our models varied between 63 to 57 %, with high uncertainty at sites with the highest values of SOC (up to 8%). The variability of SOC corresponded to a complex interaction of factors, whereas precipitation is an outstanding predictive factor across all depths, annual primary production (EVI) at the superficial horizons, and topography across deep horizons. Generated maps result in a useful tool for environmental policy, because they facilitate the periodical update of SOC and provide information for the management of this pool.