Carbon Mass Balance Research Articles

Hydrogenation of Cyclic 1,3-Diones to Their 1,3-Diols Using Heterogeneous Catalysts: Toward a Facile, Robust, Scalable, and Potentially Bio-Based Route.

Cyclopentane-1,3-diol (4b) has gained renewed attention as a potential building block for polymers and fuels because its synthesis from hemicellulose-derived 4-hydroxycyclopent-2-enone (3) was recently disclosed. However, cyclopentane-1,3-dione (4), which is a constitutional isomer of 3, possesses a higher chemical stability and can therefore afford higher carbon mass balances and higher yields of 4b in the hydrogenation reaction under more concentrated conditions. In this work, the hydrogenation of 4 into 4b over a commercial Ru/C catalyst was systematically investigated on a bench scale through kinetic studies and variation of reaction conditions. Herein, the temperature, H2-pressure, and the solvent choice were found to have significant effects on the reaction rate and suppression of undesired dehydration of 4. The cis–trans ratio of 4b is naturally generated as 7:3 in these reactions. However, at elevated reaction temperatures, 4b epimerizes, yielding more trans products. This effect was also studied and rationalized from a thermodynamic perspective using DFT. The combined optimized reaction conditions provided 78% yield for 4b, and successful applications to 8-fold scaled up reactions (40 g) and a substrate scope of several 1,3-diones demonstrate the general applicability of this catalytic approach.

Atmospheric Chemistry of c-C5HF7 and c-C5F8: Temperature-Dependent OH Reaction Rate Coefficients, Degradation Products, Infrared Spectra, and Global Warming Potentials.

c-C5HF7 (1H-heptafluorocyclopentene) and c-C5F8 (perfluorocyclopentene) are potent greenhouse gases presently used as replacement compounds in Si etching. A thorough understanding of their potential impact on climate and air quality necessitates studies of their atmospheric reactivity, radiative properties, and atmospheric degradation pathways. The predominant atmospheric removal process for these compounds is expected to be via reaction with the OH radical. In this study, rate coefficients, k, for the gas-phase reaction of the OH radical with c-C5HF7 and c-C5F8 were measured over a range of temperatures (242-370 K) and pressures (50-100 Torr, He) using a pulsed laser photolysis-laser-induced fluorescence technique. In addition, a complementary relative rate technique, employing multiple reference compounds, was used to study the reactions between 273 and 372 K at 100 Torr (He) total pressure. Reaction rate coefficients were found to be independent of pressure over this range of conditions with k1(296 K) = (4.59 ± 0.10) × 10-14 cm3 molecule-1 s-1 and k1(T) = (4.00 ± 0.40) × 10-13 exp(-(631 ± 30)/T) cm3 molecule-1 s-1 for c-C5HF7 and k2(296 K) = (4.90 ± 0.14) × 10-14 cm3 molecule-1 s-1 and k2(T) = (3.59 ± 0.4) × 10-13 exp(-(591 ± 25)/T) cm3 molecule-1 s-1 for c-C5F8. Stable end-products were measured following the OH radical-initiated degradation of c-C5HF7 and c-C5F8 in the presence of O2. F(O)CCF2CF2CF2CH(O), CF2O, and CO2 were observed as the major end-products in the oxidation of c-C5HF7 with molar yields of 0.64, 1.27, and 0.53, respectively. For c-C5F8, F(O)CCF2CF2CF2CF(O), CF2O, and CO2 were observed with molar yields of 0.66, 0.63, and 0.43, respectively. The total carbon mass balance in both systems was 1.0 ± 0.15. The high yield of a C5-dicarbonyl end-product is consistent with a ring opening at the carbon-carbon double bond site for both c-C5HF7 and c-C5F8. A comparison of the present kinetic and degradation product results with previously published studies is presented. A rate coefficient upper limit for the gas-phase reaction of O3 with c-C5HF7 and c-C5F8 of 1 × 10-21 cm3 molecule-1 s-1 was measured as part of this work. Atmospheric lifetimes for c-C5HF7 and c-C5F8 are estimated to be 252 and 236 days, respectively. Infrared absorption spectra of c-C5HF7 and c-C5F8 were also measured and found to agree, to within 5%, with results from previous studies. The well-mixed and lifetime adjusted radiative efficiencies (RE, W m-2 ppb-1) and 100 year time horizon global warming potential (GWP) for c-C5HF7 are 0.35, 0.24, and 46.7 and for c-C5F8 are 0.38, 0.25, and 46.2, respectively.

Investigation of growth limitation by CO2 mass transfer and inorganic carbon source for the microalga Chlorella vulgaris in a dedicated photobioreactor

An experiment was set up using a well-controlled photobioreactor to characterize the CO2 transfer and assimilation by photosynthetic microorganisms. This lab-scale system enabled accurate monitoring of the carbon sources in liquid and gas phases for in-depth characterization of the CO2 physical transfer and biological consumption of dissolved carbon.This paper presents a validation of the set-up by assessing the carbon mass balance in various absorption/desorption experiments. This is represented by the Carbon Recovery Percentage, which was found to be equal to 1 ± 0.1 confirming the accuracy of the time monitoring for the various carbon fluxes. These carbon fluxes were modeled to determine on-line the gas-liquid mass transfer coefficient (kLa). This enabled investigation of some aspects of CO2 dissolution in water, such as the effect of the culture medium composition and its pH value. Finally, carbon assimilation and growth limitation by the carbon source were studied for the microalga Chlorella vulgaris.

Leaf-litter consumption slows crab growth but transforms mangrove food chains

Leaf litter consumption has implications for growth and nutrient balances of mangrove crabs and mangrove trophic pathways. This study (1) addressed the impact of leaf litter quality and quantity on crab life history and growth, and (2) proposed keystone roles of crabs in mangrove material fluxes. Estimates of crab standing stocks, growth, and carbon and nitrogen mass balances were obtained for a field population of Parasesarma messa, a primary consumer of leaf litter in Queensland mangroves. P. messa exhibited slow growth and individuals took >>4 yr to reach maximum size. Females appeared to breed once per year with high reproductive effort relative to other crabs. An apparent trade-off between growth and reproduction in the dry-wet transition season was caused by a shortage of available leaf litter. A nitrogen mass balance indicated that the population ingested twice the amount of nitrogen that could be supplied by leaf litter. Assuming mortality was mainly due to predation, the estimated loss to predators (28 kg ha-1 yr-1) supported a hypothesis that crab consumption by fish short-circuits mangrove food chains. Faecal production by crabs (0.48 Mg C ha-1 yr-1 and 0.03 Mg N ha-1 yr-1) represents a substantial contribution to deposit-feeding food chains. P. messa is a keystone species whose impact on ecosystem processes is large relative to its abundance and biomass.

An evaluation of source apportionment of fine OC and PM2.5 by multiple methods: APHH-Beijing campaigns as a case study.

This study aims to critically evaluate the source apportionment of fine particles by multiple receptor modelling approaches, including carbon mass balance modelling of filter-based radiocarbon (14C) data, Chemical Mass Balance (CMB) and Positive Matrix Factorization (PMF) analysis on filter-based chemical speciation data, and PMF analysis on Aerosol Mass Spectrometer (AMS-PMF) or Aerosol Chemical Speciation Monitor (ACSM-PMF) data. These data were collected as part of the APHH-Beijing (Atmospheric Pollution and Human Health in a Chinese Megacity) field observation campaigns from 10th November to 12th December in winter 2016 and from 22nd May to 24th June in summer 2017. 14C analysis revealed the predominant contribution of fossil fuel combustion to carbonaceous aerosols in winter compared with non-fossil fuel sources, which is supported by the results from other methods. An extended Gelencsér (EG) method incorporating 14C data, as well as the CMB and AMS/ACSM-PMF methods, generated a consistent source apportionment for fossil fuel related primary organic carbon. Coal combustion, traffic and biomass burning POC were comparable for CMB and AMS/ACSM-PMF. There are uncertainties in the EG method when estimating biomass burning and cooking OC. The POC from cooking estimated by different methods was poorly correlated, suggesting a large uncertainty when differentiating this source type. The PM2.5 source apportionment results varied between different methods. Through a comparison and correlation analysis of CMB, PMF and AMS/ACSM-PMF, the CMB method appears to give the most complete and representative source apportionment of Beijing aerosols. Based upon the CMB results, fine aerosols in Beijing were mainly secondary inorganic ion formation, secondary organic aerosol formation, primary coal combustion and from biomass burning emissions.

Volcanic activity and gas emissions along the South Sandwich Arc

The South Sandwich Volcanic Arc is one of the most remote and enigmatic arcs on Earth. Sporadic observations from rare cloud-free satellite images—and even rarer in situ reports—provide glimpses into a dynamic arc system characterised by persistent gas emissions and frequent eruptive activity. Our understanding of the state of volcanic activity along this arc is incomplete compared to arcs globally. To fill this gap, we present here detailed geological and volcanological observations made during an expedition to the South Sandwich Islands in January 2020. We report the first in situ measurements of gas chemistry, emission rate and carbon isotope composition from along the arc. We show that Mt. Michael on Saunders Island is a persistent source of gas emissions, releasing 145 ± 59 t day−1 SO2 in a plume characterised by a CO2/SO2 molar ratio of 1.8 ± 0.2. Combining this CO2/SO2 ratio with our independent SO2 emission rate measured near simultaneously, we derive a CO2 flux of 179 ± 76 t day−1. Outgassing from low temperature (90–100 °C) fumaroles is pervasive at the active centres of Candlemas and Bellingshausen, with measured gas compositions indicative of interaction between magmatic fluids and hydrothermal systems. Carbon isotope measurements of dilute plume and fumarole gases from along the arc indicate a magmatic δ13C of − 4.5 ± 2.0‰. Interpreted most simply, this result suggests a carbon source dominated by mantle-derived carbon. However, based on a carbon mass balance from sediment core ODP 701, we show that mixing between depleted upper mantle and a subduction component composed of sediment and altered crust is also permissible. We conclude that, although remote, the South Sandwich Volcanic Arc is an ideal tectonic setting in which to explore geochemical processes in a young, developing arc.

Dissolved organic carbon (DOC) is essential to balance the metabolic demands of four dominant North‐Atlantic deep‐sea sponges

AbstractSponges are ubiquitous components of various deep‐sea habitats, including cold water coral reefs, and form deep‐sea sponge grounds. Although the deep sea is generally considered to be a food‐limited environment, these ecosystems are known to be hotspots of biodiversity and carbon cycling. To assess the role of sponges in the carbon cycling of deep‐sea ecosystems, we studied the carbon budgets of six dominant deep‐sea sponges of different phylogenetic origin, with various growth forms and hosting distinct associated microbial communities, in an ex situ aquarium setup. Additionally, we determined biomass metrics—planar surface area, volume, wet weight, dry weight (DW), ash‐free dry weight, and organic carbon (C) content—and conversion factors for all species. Oxygen (O2) removal rates averaged 3.3 ± 2.8 μmol O2 g DWsponge h−1 (mean ± SD), live particulate (bacterio‐ and phytoplankton) organic carbon removal rates averaged 0.30 ± 0.39 μmol C g DWsponge h−1 and dissolved organic carbon (DOC) removal rates averaged 18.70 ± 25.02 μmol C g DWsponge h−1. Carbon mass balances were calculated for four species and revealed that the sponges acquired 1.3–6.6 times the amount of carbon needed to sustain their minimal respiratory demands. These results indicate that irrespective of taxonomic class, growth form, and abundance of microbial symbionts, DOC is responsible for over 90% of the total net organic carbon removal of deep‐sea sponges and allows them to sustain themselves in otherwise food‐limited environments on the ocean floor.

Greenhouse gas and ammonia emissions from stored manure from beef cattle supplemented 3-nitrooxypropanol and monensin to reduce enteric methane emissions

The investigative material 3-nitrooxypropanol (3-NOP) can reduce enteric methane emissions from beef cattle. North American beef cattle are often supplemented the drug monensin to improve feed digestibility. Residual and confounding effects of these additives on manure greenhouse gas (GHG) emissions are unknown. This research tested whether manure carbon and nitrogen, and GHG and ammonia emissions, differed from cattle fed a typical finishing diet and 3-NOP [125–200 mg kg−1 dry matter (DM) feed], or both 3-NOP (125–200 mg kg−1 DM) and monensin (33 mg kg−1 DM) together, compared to a control (no supplements) when manure was stockpiled or composted for 202 days. Consistent with other studies, cumulative GHGs (except nitrous oxide) and ammonia emissions were higher from composted compared to stockpiled manure (all P < 0.01). Dry matter, total carbon and total nitrogen mass balance estimates, and cumulative GHG and ammonia emissions, from stored manure were not affected by 3-NOP or monensin. During the current experiment, supplementing beef cattle with 3-NOP did not significantly affect manure GHG or NH3 emissions during storage under the tested management conditions, suggesting supplementing cattle with 3-NOP does not have residual effects on manure decomposition as estimated using total carbon and nitrogen losses and GHG emissions.

Carbon mass balance model to investigate biochar and activated carbon amendment effects on the biodegradation of stable-isotope labeled toluene in gravelly sand

Fully stable isotope-labeled toluene was used as a model volatile petroleum hydrocarbon (VPH) to investigate the mineralization of VPHs and soil organic matter (SOM) by soil microorganisms in the presence and absence of 2%%(w/w) wood-chip biochar or bitumen-derived activated carbon. Biodegradation of 13C7 -toluene was monitored in batch microcosms for 19 days by measuring headspace CO2 and toluene concentrations. A numerical carbon mass balance model was developed to interpret the experimental observations. Increased 44CO2 and 45CO2 headspace concentrations following 13C7 -toluene addition as compared to live and abiotic controls indicated a stimulation of microbial activity. By fitting a maximum specific growth rate (μmax) of 0.6 h −1 (in line with published rates), it was possible to match model predictions of 45CO2 and 44CO2 concentrations with the experimentally determined data. Half-saturation constants (Ks) of 4.06 × 103 mgL −1, 7.76 × 102 mgL −1 and 1.83 × 102 mgL −1 were predicted for soil, soil & BC and soil & AC respectively, much higher than previously reported values. Differences in the half-saturation constant suggests that sorbent amendment affects the microbial ecology, by making microorganisms which can utilize substrates at lower concentrations more competitive. Consequently, amending soils with 2% BC or AC changed the biokinetics of VPH degradation by rendering VPHs less bioavailable, but did not appear to have any detrimental effects on VPH degradation and may serve as a sustainable, cost-effective approach for enhancing the natural attenuation of VPHs in soil on the long term.

Identifying and addressing knowledge gaps for improving greenhouse gas emissions estimates from tropical peat forest fires

Tropical peatlands are areas of high carbon density that are important in biosphere-atmosphere interactions. Drainage and burning of tropical peatlands releases about 5% of global greenhouse gas (GHG) emissions, yet there is great uncertainty in these estimates. Our comprehensive literature review of parameters required to calculate GHG emissions from burnt peat forests, following the international guidelines, revealed many gaps in knowledge of carbon pools and few recent supporting studies. To improve future estimates of the total ecosystem carbon balance and peatfire emissions this study aimed to account for all carbon pools: aboveground, deadwood, pyrogenic carbon (PyC) and peat of single and repeatedly burnt peat forests. A further aim was to identify the minimum sampling intensity required to detect with 80% power significant differences in these carbon pools among long unburnt, recently burnt and repeatedly burnt peat swamp forests.About 90 Mg C ha−1 remains aboveground as deadwood after a single fire and half of this remains after a second fire. One fire produces 4.5 ± 0.6 Mg C ha−1 of PyC, with a second fire increasing this to 7.1 ± 0.8 Mg C ha−1. For peat swamp forests these aboveground carbon pools are rarely accounted in estimates of emissions following multiple fires, while PyC has not been included in the total peat carbon mass balance. Peat bulk density and peat carbon content change with fire frequency, yet these parameters often remain constant in the published emission estimates following a single and multiple fires. Our power analysis indicated that as few as 12 plots are required to detect meaningful differences between fire treatments for the major carbon pools. Further field studies directed at improving the parameters for calculating carbon balance of disturbed peat forest ecosystems are required to better constrain peatfire GHG emission estimates.

Carbon-Dioxide and Hydrogen-Sulfide Removal from Simulated Landfill Gas Using Steel Slag

Municipal solid waste landfills are a source of major greenhouse gases such as methane (CH4) and carbon dioxide (CO2) and emit a trace amount of hydrogen sulfide (H2S). Recently, steel slag has extensively been used for mineral CO2 sequestration to minimize the CO2 releases to the atmosphere. This study explores the potential of basic oxygen furnace (BOF) steel slag to simultaneously remove CO2 and H2S from landfill gas (LFG). Various batch and column tests were conducted to evaluate the CO2 and H2S removal potential of the BOF slag under various conditions such as moisture content and particle size of the BOF slag. The three different particle sizes of BOF slag (coarse, as-is, and fine) were exposed to continuous flow of a synthetic LFG [50% CO2, 48.25% CH4, and 1.75% H2S by volume (v/v)] in a column reactor to evaluate the effect of particle size on CO2 and H2S removal capacity of the slag. Similarly, the BOF slag was exposed to synthetic LFG as well as 20% (v/v) of H2S alone in batch reactors at varying moisture contents (10%–30% by weight) to evaluate the effect of moisture content on the CO2 and H2S removal capacity of the slag. A significant H2S removal of 27 g H2S kg−1 BOF slag and CO2 removal of 76 g CO2 kg−1 BOF slag were obtained in the batch reactor. The fine BOF slag (<0.106 mm) showed the maximum CO2 removal (300 g CO2 kg−1 BOF slag) and H2S removal (38 g H2S kg−1 BOF slag) upon exposure to continuous synthetic LFG flow in the column reactor. The quantitative X-ray diffraction (QXRD) analysis showed the highest increase in carbon (77.5 g C kg−1 BOF slag) and sulfur (28 g S kg−1 BOF slag) contents in the fine BOF slag, which was consistent with the mass balance of carbon and sulfur from CO2 and H2S uptake in column tests. The major reaction product with H2S was elemental sulfur depicted by the significant increase in the sulfur content in the X-ray fluorescence analysis. The key minerals involved in carbonation reactions were lime, portlandite, and larnite, as these minerals showed significant reduction in weight percentage (100%, 82%, and 80%, respectively) in the QXRD analysis. Overall, BOF slag showed promising results in mitigating CO2 and H2S from LFG.

Marine organic carbon burial increased forest fire frequency during Oceanic Anoxic Event 2

Volcanic-driven nutrient flux to the oceans stimulated marine productivity and organic matter burial during Oceanic Anoxic Event 2 (OAE2; ~94 million years ago). While the preferential burial of 13C-depleted organic matter led to a general 13C enrichment of sediments during the event, a 2‰ 13C depletion punctuated the first half of the event (known as the Plenus), raising questions about carbon cycle feedbacks during OAE2. Here we present organic geochemical evidence (for example, pyrogenic polycyclic aromatic hydrocarbons) from the Western Interior Seaway that indicates increased forest fire frequency in the western United States during the Plenus. Carbon mass balance equations, which account for the amount and carbon isotopic composition of atmospheric CO2 and forest biomass during OAE2, potentiate fires in the western United States as part of a widespread increase in forest fires that could have alone caused the global 2‰ 13C depletion during the Plenus. Plant biomarkers suggest that local precipitation and plant type did not change significantly, indicating that elevated atmospheric oxygen levels from widespread organic carbon burial increased the frequency of fires in wet forest ecosystems that were extensive during OAE2. Plant biomarkers also indicate that forest fires amplified the flux of terrestrial organic matter and nutrients to the oceans, which may have enhanced marine productivity, organic carbon burial and the return to 13C-enriched sediments at the end of the Plenus. The extent that this feedback impacted global biogeochemistry during the Plenus and the rest of OAE2, as well as other events in Earth history, warrants further investigation. A global carbon cycle perturbation during Oceanic Anoxic Event 2 was probably due to elevated oxygen levels leading to a transient increase in wildfire activity, according to a record of plant biomarkers tracking fire frequency in western North America.

Restoring Pre-Industrial CO2 Levels While Achieving Sustainable Development Goals

Unless humanity achieves United Nations Sustainable Development Goals (SDGs) by 2030 and restores the relatively stable climate of pre-industrial CO2 levels (as early as 2140), species extinctions, starvation, drought/floods, and violence will exacerbate mass migrations. This paper presents conceptual designs and techno-economic analyses to calculate sustainable limits for growing high-protein seafood and macroalgae-for-biofuel. We review the availability of wet solid waste and outline the mass balance of carbon and plant nutrients passing through a hydrothermal liquefaction process. The paper reviews the availability of dry solid waste and dry biomass for bioenergy with CO2 capture and storage (BECCS) while generating Allam Cycle electricity. Sufficient wet-waste biomass supports quickly building hydrothermal liquefaction facilities. Macroalgae-for-biofuel technology can be developed and straightforwardly implemented on SDG-achieving high protein seafood infrastructure. The analyses indicate a potential for (1) 0.5 billion tonnes/yr of seafood; (2) 20 million barrels/day of biofuel from solid waste; (3) more biocrude oil from macroalgae than current fossil oil; and (4) sequestration of 28 to 38 billion tonnes/yr of bio-CO2. Carbon dioxide removal (CDR) costs are between 25–33% of those for BECCS with pre-2019 technology or the projected cost of air-capture CDR.

Effect of the admixture of N2 to low pressure, low temperature H2-CH4-CO2 microwave plasmas used for large area deposition of nanocrystalline diamond films

In a distributed antenna array reactor, microwave H2-CH4-CO2 plasmas with admixture of N2 used for the low-temperature deposition of nanocrystalline diamond (NCD) films are studied by in situ infrared laser absorption spectroscopy (LAS) and optical emission spectroscopy techniques. The experiments are carried out in order to analyze the dependence of temperatures and species densities as a function of the admixture of nitrogen. The evolution of the concentrations of the methyl radical (CH3), and of five stable molecules (NH3, HCN, CH4, C2H2, and CO), are monitored in the plasma processes by LAS using tunable lead salt diode lasers and external-cavity quantum cascade lasers (EC-QCL) as radiation sources. OES is performed simultaneously to obtain complementary information about (i) the degree of dissociation of H2 precursor gas, (ii) the gas temperature and therefore (iii) the density of atomic hydrogen, a key species in the chemistry of NCD deposition plasmas. The species temperatures are not significantly affected by the nitrogen addition. The concentrations of the various species are in the range between 1011 to 1015 molecules cm−3. HCN and CO are the major products in the plasma besides atomic hydrogen. The analysis of the nitrogen and carbon mass balances of the measured species shows that in addition to NH3 and HCN other nitrogen containing species are produced in the plasma which were not probed. It is shown that the formation of HCN consumes C atoms that can be provided from hydrocarbon species and from the deposition of carbon-containing films on the reactor walls, which results in a decrease of the measured densities of hydrocarbon species.

Determination of gaseous and particulate emission factors from road transport in a Middle Eastern capital

Road transport is a major source of anthropogenic emissions especially in the Middle East where the regulations enforcement is generally poor. This study aims to quantify the Emission Factors (EF) of traffic-related gaseous and particulate pollutants inside the Salim Slam urban tunnel in Beirut, Lebanon. The fuel-based emission factors of measured pollutants were from the carbon mass balance model. The EF determined showed general higher values than those reported in recent studies from European and American countries, even for speciated NMVOC. The average CO and NOx emission factors for the mixed fleet (HDV + LDV) were determined to be 10.52 ± 3.00 g km−1 and 2.20 ± 0.57 g km−1 respectively, while the EF for PM2.5 55 ± 27 mg km−1. Moreover, IVOC species from gaseous phase were reported for the first time in the region. A reduction trend was observed in comparison with the previous tunnel study from Lebanon, however there is still a need to have tougher regulations to control the local practices such as removal of catalytic converter, adjustment of engine parameters for inspection, etc. The comparison of the EF to those calculated through EMEP or IPCC methodologies shows the need to take local practices while establishing national emission inventories.

Growth Dynamics of Bacterial Populations in a Two-Compartment Biofilm Bioreactor Designed for Continuous Surfactin Biosynthesis.

Biofilm bioreactors are promising systems for continuous biosurfactant production since they provide process stability through cell immobilization and avoid foam formation. In this work, a two-compartment biofilm bioreactor was designed consisting of a stirred tank reactor and a trickle-bed reactor containing a structured metal packing for biofilm formation. A strong and poor biofilm forming B. subtilis 168 strain due to restored exopolysaccharides (EPS) production or not were cultivated in the system to study the growth behavior of the planktonic and biofilm population for the establishment of a growth model. A high dilution rate was used in order to promote biofilm formation on the packing and wash out unwanted planktonic cells. Biofilm development kinetics on the packing were assessed through a total organic carbon mass balance. The EPS+ strain showed a significantly improved performance in terms of adhesion capacity and surfactin production. The mean surfactin productivity of the EPS+ strain was about 37% higher during the continuous cultivation compared to the EPS- strain. The substrate consumption together with the planktonic cell and biofilm development were properly predicted by the model (α = 0.05). The results show the efficiency of the biofilm bioreactor for continuous surfactin production using an EPS producing strain.

Quantification methods of forest and land fires impact on the atmospheric environment (case study: oil palm plantation in Kayuagung District, OKI Regency, South Sumatra)

The impact of forest and land fires on the atmospheric environment can be classified into three components, namely ambient air quality, its contribution to greenhouse gases, and microclimate change. Each component has a different method for assessing and measuring the magnitude of its impact. The aim of the study is to obtain quantitative methods to assess the magnitude of the impact of forest and land fires on the atmospheric environment so that they can be used for the valuation of environmental losses. The magnitude of the impact of the air quality component is measured based on the Air Pollution Index (ISPU) and visibility, the component of the greenhouse gas is assessed by approaching the amount of GHG emissions and / or loss of carbon stocks, while changes in the microclimate by assessing changes in the level of thermal comfort. Gas and particulate emissions values of forest and land fires use the carbon mass balance approach and emission factors. Analysis of air pollution dispersion is conducted use the Gaussian model, with case study is the incidence of land fires in oil palm plantations located in Kayuagung sub-district, Ogan Komering Ilir Regency, South Sumatra Province in 2015, 2016 and 2017. The data used in this study consisted of Landsat 8 satellite imagery, MODIS and VIIRS Hotspots, measurements of vegetation biomass in the field, organic C-peat and climate data during fires. The results of the assessment show that land fires covering 551 ha in 2015, 59 ha in 2016 and 253 ha in 2018 have resulted in changes in the air pollutant standard index in Kayuagung from the medium category (ISPU PM10 = 75) to very unhealthy (ISPU PM10 = 272) in 2015, unhealthy (ISPU CO = 116) in 2016 and very unhealthy (ISPU CO = 205) in 2018. Visibility in an area of about 500-600 meters in the direction of the wind from the fire’s location was less than 1 km with PM10 of more than 176 µg m−3. The contribution of GHGs to each fire’s year is 26.8, 2.8 and 12.3 kilo tons of CO2e consist of CO2 and CH4. The results of this study can be used to quantify the magnitude of the land fires impact on the atmospheric environment.

The Influence of Vanadium Additions on Isothermally Formed Bainite Microstructures in Medium Carbon Steels Containing Retained Austenite

The influence of V additions on isothermally formed bainite in medium carbon steels containing retained austenite has been investigated using in-situ high energy X-ray diffraction (HEXRD) and ex-situ electron energy loss spectroscopy (EELS) and energy dispersive X-ray analysis (EDX) techniques in the transmission electron microscope (TEM). No significant impact of V in solid solution on the bainite transformation rate, final phase fractions or on the width of bainite laths was seen for transformations in the range 375–430 °C. No strong influence on the dislocation density could be detected, although quantitative analysis was impeded by ferrite tetragonality. A reduction in the carbon content of retained austenite Cγ that is not believed to be due to competition with VC or cementite precipitation was observed. No influence of V on the carbon supersaturation in bainitic ferrite Cb could be directly measured, although carbon mass balance calculations suggest Cb slightly increases. A beneficial refinement of blocky MA and a corresponding size effect induced enhancement in austenite stability were found at the lowest transformation temperature. Overall, V additions result in a slight increase in strength levels.

Performance and mechanism of carbon dioxide fixation by a newly isolated chemoautotrophic strain Paracoccus denitrificans PJ-1

CO2 is regarded as a major contributor to the global warming. CO2 utilization is promising to reduce the CO2 emissions. Currently, the biofixation of CO2 using chemoautotrophs has markedly gain interest in CO2 utilization. In this study, a newly isolated chemoautotroph, Paracoccus denitrificans PJ-1, was used for the biofixation of CO2 under anaerobic condition. Experimental results revealed that Paracoccus denitrificans PJ-1 achieved a high carbon fixation rate (13.25 mg·L−1·h−1) which was ∼10 times faster than the previous reported chemotrophic bacteria using thiosulfate as electron donor. The best CO2 fixation activity of Paracoccus denitrificans PJ-1 was achieved at the pH value of 9.0 and CO2 concentration of 20 vol%. Meanwhile, a high CO2 fixation yield of 106.03 mg·L−1 was reached. The presence of oxygen was adverse to the biofixation, indicating that strain PJ-1 was more suitable for CO2 fixation in anaerobic environments. Carbon mass balance analysis revealed that the carbon from CO2 was mainly fixed into the extracellular organic carbon rather than the biomass. GC-MS analysis and cbbL gene test revealed that Paracoccus denitrificans PJ-1 fixed CO2 through the Calvin-Benson-Bassham cycle and mainly converted CO2 to oxalic acid and succinic acid. Overall, the excellent CO2 fixation capacity of Paracoccus denitrificans PJ-1 suggests that it had potential for CO2 utilization.

Tracking the evolution of particulate organic matter sources during summer storm events via end-member mixing analysis based on spectroscopic proxies

Despite the growing attention to the effects of hydrological precipitation on organic carbon export along the continuum land-river-ocean, limited effort has been made to understand the export and the reactivity of particulate organic carbon (POC) compared to those of dissolved organic carbon (DOC). Yet, further understanding of the controlling mechanisms on the export of particulate organic matter (POM) from terrestrial systems is fundamental. In this study, we assessed the temporal changes of the source contributions to riverine POM in two adjacent rivers of the same watershed during two summer storm events, which included the early and the late events, using end-member mixing analysis (EMMA) based on spectroscopic proxies. The EMMA showed relatively high contributions of terrestrial materials to the riverine POM for both rivers during the early summer storm event. However, this trend did not persist until the late summer storm event, which presented the decreased contributions of the terrestrial sources and less dynamic changes in the source distributions compared to those observed in the early summer rain event. These results demonstrate the combined impacts of the land use/surrounding area, the hydrology, and the intra-seasonal variations on the dominant riverine POM sources. This study provides an interesting insight into the importance of the intense hydrological events on the export of the terrestrial OM and further on the potential modification of the existing carbon mass balance along the continuum land-river-ocean.