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1.
Top Curr Chem (Cham) ; 378(1): 11, 2020 Jan 06.
Artigo em Inglês | MEDLINE | ID: mdl-31903506

RESUMO

The dramatic increase in atmospheric carbon dioxide (CO2) concentrations has attracted human attention and many strategies about converting CO2 into high-value chemicals have been put forward. Metal-organic frameworks (MOFs), as a class of versatile materials, have been widely used in CO2 capture and chemical conversion, due to their unique porosity, multiple active centers and good stability and recyclability. Herein, we focused on the processes of chemical conversion of CO2 by MOFs-based catalysts, including the coupling reactions of epoxides, aziridines or alkyne molecules, CO2 hydrogenation, and other CO2 conversion reactions. The synthesized methods and high catalytic activity of MOFs-based materials were also analyzed systematically. Finally, a brief perspective on feasible strategies is presented to improve the catalytic activity of novel MOFs-based materials and explore the new CO2 conversion reactions.


Assuntos
Dióxido de Carbono/química , Estruturas Metalorgânicas/química , Alcenos/química , Aminas/química , Aziridinas/química , Catálise , Compostos de Epóxi/química , Hidrogenação , Líquidos Iônicos/química
2.
J Zoo Wildl Med ; 50(4): 1026-1030, 2020 Jan 09.
Artigo em Inglês | MEDLINE | ID: mdl-31926542

RESUMO

The Galápagos shearwater, Puffinus subalaris, is a seabird endemic to the Galápagos archipelago. Hematology, blood chemistry, and general health parameters have not been published for this species. Analyses were run on blood samples drawn from 20 clinically healthy Galápagos shearwaters captured by hand at their nests at Islote Pitt on San Cristóbal Island in July 2016. A portable blood analyzer (iSTAT) was used to obtain near immediate field results for pH, pO2, pCO2, TCO2, HCO3 -, hematocrit, hemoglobin, sodium, potassium, chloride, ionized calcium, creatinine, urea nitrogen, anion gap, and glucose. Blood lactate was measured using a portable Lactate Plus analyzer. The reported results provide baseline data that can be used for comparisons among populations and in detecting changes in health status among Galápagos shearwaters.


Assuntos
Bicarbonatos/sangue , Aves/sangue , Dióxido de Carbono/sangue , Hematócrito/veterinária , Oxigênio/sangue , Equilíbrio Ácido-Base , Animais , Glicemia , Cálcio/sangue , Cloretos/sangue , Creatinina/sangue , Hemoglobinas , Concentração de Íons de Hidrogênio , Lactatos/sangue , Potássio/sangue , Sódio/sangue
3.
Water Res ; 171: 115457, 2020 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-31931377

RESUMO

Although estimates of total CO2 emissions from global estuaries are gradually decreasing, current numbers are based on limited data and the impacts of anthropogenic and seasonal disturbances have not been studied extensively. Our study estimates annual and seasonal CO2 fluxes in China's Yellow River Estuary (YRE) which incorporated spatiotemporal variations and the effects of water and sediment regulation (WSR). Aquatic metabolism was estimated using Odum's open water dissolved oxygen methods and used to represent the production and assimilation of CO2. Net ecosystem production (NEP) was used to represent the CO2 flux from biological activities and estimate the major CO2 emitters in the YRE. According to our measurements, the annual CO2 release was 6.14 ± 33.63 mol C m-2 yr-1 from 2009 to 2013 and the annual CO2 efflux from the 1521.3 km2 of estuarine surface area was 0.11 ± 0.61 Tg C yr-1 in the YRE. High CO2 emissions in autumn were balanced by high CO2 sequestration in summer, leading to a lower than expected annual net CO2 efflux. The system is an atmospheric CO2 source in spring and winter, near neutral in early summer, a large sink in late summer after WSR, and finally a large atmospheric CO2 source in autumn. Discharge events and seasonality jointly affect estuarine CO2 flux. High CO2 sequestration in summer is due mainly to a combination of high water temperature, chlorophyll a levels, dissolved inorganic carbon, and solar radiation and low turbidity, discharge, and chemical oxygen demand (COD) after WSR. WSR supports the high gross primary productivity rate which exceeds the increase in ecosystem respiration. Although the YRE, as a whole, is a source of atmospheric CO2, the amount of CO2 released is lower than the average estuarine value of mid-latitude regions. Our findings therefore suggest that global CO2 release from estuarine systems is overestimated if spatiotemporal variations and the effects of anthropogenic disturbance are excluded. The NEP method is effective for estimating the CO2 flux, especially in estuaries where CO2 variation is mainly due to biological processes.


Assuntos
Estuários , Rios , Dióxido de Carbono , China , Clorofila A , Ecossistema , Monitoramento Ambiental , Processos Heterotróficos , Estações do Ano
4.
J Environ Manage ; 256: 109971, 2020 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-31989987

RESUMO

Wetland ecosystems have a disproportionally large influence on the global carbon cycle. They can act as carbon sinks or sources depending upon their location, type, and condition. Rehabilitation of wetlands is gaining popularity as a nature-based approach to helping mitigate climate change; however, few studies have empirically tested the carbon benefits of wetland restoration, especially in freshwater environments. Here we investigated the effects of passive rehabilitation (i.e. fencing and agricultural release) of 16 semi-arid rain-filled freshwater wetlands in southeastern Australia. Eight control sites were compared with older (>10 year) or newer (2-5 year) rehabilitated sites, dominated by graminoids or eucalypts. Carbon stocks (soils and plant biomass), and emissions (carbon dioxide - CO2; and methane - CH4) were sampled across three seasons, representing natural filling and drawdown, and soil microbial communities were sampled in spring. We found no significant difference in soil carbon or greenhouse gas emissions between rehabilitated and control sites, however, plant biomass was significantly higher in older rehabilitated sites. Wetland carbon stocks were 19.21 t Corg ha-1 and 2.84 t Corg ha-1 for soils (top 20 cm; n = 137) and plant biomass (n = 288), respectively. Hydrology was a strong driver of wetland greenhouse gas emissions. Diffusive fluxes (n = 356) averaged 117.63 mmol CO2 m2 d-1 and 2.98 mmol CH4 m2 d-1 when wet, and 124.01 mmol CO2 m2 d-1 and -0.41 mmol CH4 m2 d-1 when dry. Soil microbial community richness was nearly 2-fold higher during the wet phase than the dry phase, including relative increases in Nitrososphaerales, Myxococcales and Koribacteraceae and methanogens Methanobacteriales. Vegetation type significantly influenced soil carbon, aboveground carbon, and greenhouse gas emissions. Overall, our results suggest that passive rehabilitation of rain-filled wetlands, while valuable for biodiversity and habitat provisioning, is ineffective for increasing carbon gains within 20 years. Carbon offsetting opportunities may be better in systems with faster sediment accretion. Active rehabilitation methods, particularly that reinstate the natural hydrology of drained wetlands, should also be considered.


Assuntos
Ecossistema , Áreas Alagadas , Austrália , Dióxido de Carbono , Metano , Chuva , Solo
5.
Oecologia ; 192(2): 515-527, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31950262

RESUMO

Biodiversity loss and climate warming are occurring in concert, with potentially profound impacts on ecosystem functioning. We currently know very little about the combined effects of these changes on the links between the community structure, dynamics and the resulting in situ CO2 concentrations in freshwater ecosystems. Here we aimed to determine both individual and combined effects of temperature and non-resource diversity (species inedible for a given consumer) on CO2 concentration. Our analysis further aimed to establish both direct effects on CO2 concentrations and potential indirect effects that occur via changes to the phytoplankton and zooplankton biomasses. Our results showed that there were no interactive effects of changes in temperature and diversity on CO2 concentration in the water. Instead, independent increases in either temperature or non-resource diversity resulted in a substantial reduction in CO2 concentrations, particularly at the highest non-resource diversity. The effects of non-resource diversity and warming on CO2 were indirect, resulting largely from the positive impacts on total biomass of primary producers. Our study is the first to experimentally partition the impacts of temperature and diversity on the consumer-resource dynamics and associated changes to CO2 concentrations. It provides new mechanistic insights into the role of diverse plankton communities for ecosystem functioning and their importance in regulating CO2 dynamics under ongoing climate warming.


Assuntos
Dióxido de Carbono , Ecossistema , Animais , Biodiversidade , Biomassa , Água Doce , Temperatura Ambiente , Zooplâncton
6.
Ying Yong Sheng Tai Xue Bao ; 31(1): 72-82, 2020 Jan.
Artigo em Chinês | MEDLINE | ID: mdl-31957382

RESUMO

Photosynthetically active radiation (PAR) is a key environmental factor affecting the change of net ecosystem exchange (NEE) during the daytime. However, the coordinate system of PAR measured by horizontal radiometers over sloping terrain does not match that of NEE after tilt-corrected of the ultrasonic anemometer. Using the temperate deciduous broad-leaved forest at the Maoershan site with an average slope of 9° and a azimuth of 296° as a case, we investigated the diurnal variations in NEE and its driving factors in the growing season (May to September) of 2016. We assessed the differences in estimating light response parameters and the explanations of NEE by other environmental factors between the PAR measured by horizontal and slope-parallel radiometers. The results showed that the diurnal change of NEE in each month of the growing season presented a morning-afternoon asymmetrically unimodal curve: the value was negative (net carbon absorption) about 2.5 h after sunrise, reached the peak around 12:00, then approached zero again at two hours before sunset. The daily net uptake maximized in July and minimized in May. During the whole growing season, the time-lag and difference in the PAR measured by the horizontal versus slope-parallel radiometers led to that the PAR values measured by the horizontal radiometer increased photosynthetic quantum yield (α) and daytime respiration rate (Rd) by 13.3% and 11.5%, respectively, and decreased the maximum photosynthetic efficiency (Amax) by 7.7%. The light response curves of NEE were asymmetrical in the morning and afternoon, with Rd and Amax in the afternoon being greater than that in the morning. Weather conditions affected light response parameters: on cloudy days, Amax was higher than that in sunny days, the α and Rd were lower versus those in sunny days for most conditions. However, the monthly Amax and Rd were generally higher for horizontally measured PAR than for slope-parallelly measured PAR, especially for Amax in the cloudy afternoon. The radiometer-orientation affected the explanation of daytime NEE by air temperature (Ta) and vapor pressure deficit (VPD). The correlation of NEE residual based on the slope-parallel radiometer with Ta and VPD (r ranged: 0.013 to 0.197, 0.098 to 0.224) was tighter than that based on the horizontal radiometer (r ranged: 0.082 to 0.219, 0.162 to 0.282) when the negative correlations with Ta for September was excluded. Our results indicated that the measurements of PAR on the inclined terrains could cause errors in the environmental interpretations of NEE. Such findings had implications for the radiometric measurement of mountain vegetation and the reasonable interpretation of carbon exchange in terrestrial ecosystems.


Assuntos
Carbono , Ecossistema , Dióxido de Carbono , China , Florestas , Fotossíntese , Estações do Ano
7.
J Environ Manage ; 258: 110030, 2020 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-31929066

RESUMO

The greenhouse effect is closely related to elevated atmospheric CO2 concentrations and therefore, carbon capture and storage (CCS) has attracted attention worldwide as a method for preventing the release of CO2 into the atmosphere, which highlights the importance of monitoring CO2 released from subsurface deposits. In this study, CO2 gas with a δ13C value of -30‰ was injected into soil through pipes installed at a depth of 2.5 m, and samples of CO2 gas released from the soil surface and three soil depths were collected from September 2015 to March 2016 to estimate subsurface CO2 movement. Before and after CO2 injection, the δ13C values of CO2 released from the soil surface ranged from -24.5 to -13.4‰ (average -20.2 ± 2.1‰, n = 25) and from -31.6 to -11.9‰ (average -23.2 ± 4.3‰, n = 49), respectively. The results indicated that the leakage of injected CO2 was successfully detected at the surface. The δ13C values were visualized using an interpolation map to estimate the subsurface CO2 distribution, which confirmed that diffusion of the injected CO2 gas extended to the soil zone where CO2 was not injected. Additionally, variation in δ13C for soil CO2 was detected at the three soil depths (15, 30, and 60 cm), where the values were -16.1, -20.0, and -22.1‰, respectively. Different δ13C values horizontally and vertically indicated that soil heterogeneity led to different CO2 migration pathways and rates. We suggest that the carbon isotope ratio of CO2 is an effective tool for concurrently monitoring CO2 leakage on and under surface in a soil zone if a thorough baseline study is carried out in the field.


Assuntos
Dióxido de Carbono , Solo , Atmosfera , Isótopos de Carbono , República da Coreia
8.
Top Curr Chem (Cham) ; 378(1): 14, 2020 Jan 13.
Artigo em Inglês | MEDLINE | ID: mdl-31933069

RESUMO

Classical molecular simulations can provide significant insights into the gas adsorption mechanisms and binding sites in various metal-organic frameworks (MOFs). These simulations involve assessing the interactions between the MOF and an adsorbate molecule by calculating the potential energy of the MOF-adsorbate system using a functional form that generally includes nonbonded interaction terms, such as the repulsion/dispersion and permanent electrostatic energies. Grand canonical Monte Carlo (GCMC) is the most widely used classical method that is carried out to simulate gas adsorption and separation in MOFs and identify the favorable adsorbate binding sites. In this review, we provide an overview of the GCMC methods that are normally utilized to perform these simulations. We also describe how a typical force field is developed for the MOF, which is required to compute the classical potential energy of the system. Furthermore, we highlight some of the common analysis techniques that have been used to determine the locations of the preferential binding sites in these materials. We also review some of the early classical molecular simulation studies that have contributed to our working understanding of the gas adsorption mechanisms in MOFs. Finally, we show that the implementation of classical polarization for simulations in MOFs can be necessary for the accurate modeling of an adsorbate in these materials, particularly those that contain open-metal sites. In general, molecular simulations can provide a great complement to experimental studies by helping to rationalize the favorable MOF-adsorbate interactions and the mechanism of gas adsorption.


Assuntos
Gases/isolamento & purificação , Estruturas Metalorgânicas/química , Adsorção , Dióxido de Carbono/isolamento & purificação , Simulação por Computador , Hidrogênio/isolamento & purificação , Modelos Químicos , Modelos Moleculares , Método de Monte Carlo , Eletricidade Estática , Termodinâmica
9.
Environ Technol ; 41(5): 617-626, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-30074855

RESUMO

The microalgae Chlorella vulgaris ATCC 13482 was used in the present study for municipal wastewater treatment. Batch experiments were performed in bubble column photobioreactors of 7 L working volume maintained at 25 ± 2°C and 14 h/10 h of photo and dark cycle. The treatment process was enhanced by using CO2-augmented air (5% CO2 v/v) supply into the microalgal culture in comparison to the use of normal air (0.03% CO2 v/v). For a period of 7 days, C. vulgaris effected maximum removals of 74.4% soluble fraction of chemical oxygen demand, 72% ammonia (NH4-N), 60% nitrate (NO3-N) and 81.93% orthophosphate (PO4-P) with use of normal air, whereas 84.6% sCOD, 88% NH4-N, 72% NO3-N and 92.8% PO4-P removals, respectively, with use of 5% CO2/air supply. Using kinetic study data, the specific rates of ammonia and phosphate uptake (qammonia and qphosphate) by C. vulgaris at 5% CO2/air supply were found to be 2.41 and 0.85 d-1, respectively. Using the algal remediation technology, nitrogen-phosphorus-potassium recovery from sewage treatment plant of 37.5 million litres per day wastewater influent capacity was calculated to be ∼298.5, 55.4 and 83.7 kg d-1, respectively.


Assuntos
Chlorella vulgaris , Microalgas , Biomassa , Dióxido de Carbono , Nitrogênio , Nutrientes , Fotobiorreatores , Águas Residuárias
10.
Arch Dis Child Fetal Neonatal Ed ; 105(1): 87-93, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31123057

RESUMO

OBJECTIVE: High-flow nasal cannula (HFNC) therapy is increasingly used in preterm infants despite a paucity of physiological studies. We aimed to investigate the effects of HFNC on respiratory physiology. STUDY DESIGN: A prospective randomised crossover study was performed enrolling clinically stable preterm infants receiving either HFNC or nasal continuous positive airway pressure (nCPAP). Infants in three current weight groups were studied: <1000 g, 1000-1500 g and >1500 g. Infants were randomised to either first receive HFNC flows 8-2 L/min and then nCPAP 6 cm H2O or nCPAP first and then HFNC flows 8-2 L/min. Nasopharyngeal end-expiratory airway pressure (pEEP), tidal volume, dead space washout by nasopharyngeal end-expiratory CO2 (pEECO2), oxygen saturation and vital signs were measured. RESULTS: A total of 44 preterm infants, birth weights 500-1900 g, were studied. Increasing flows from 2 to 8 L/min significantly increased pEEP (mean 2.3-6.1 cm H2O) and reduced pEECO2 (mean 2.3%-0.9%). Tidal volume and transcutaneous CO2 were unchanged. Significant differences were seen between pEEP generated in open and closed mouth states across all HFNC flows (difference 0.6-2.3 cm H2O). Infants weighing <1000 g received higher pEEP at the same HFNC flow than infants weighing >1000 g. Variability of pEEP generated at HFNC flows of 6-8 L/min was greater than nCPAP (2.4-13.5 vs 3.5-9.9 cm H2O). CONCLUSIONS: HFNC therapy produces clinically significant pEEP with large variability at higher flow rates. Highest pressures were observed in infants weighing <1000 g. Flow, weight and mouth position are all important determinants of pressures generated. Reductions in pEECO2 support HFNC's role in dead space washout.


Assuntos
Oxigenoterapia/métodos , Respiração com Pressão Positiva , Síndrome do Desconforto Respiratório do Recém-Nascido/terapia , Peso Corporal , Dióxido de Carbono/sangue , Pressão Positiva Contínua nas Vias Aéreas , Estudos Cross-Over , Feminino , Humanos , Recém-Nascido , Recém-Nascido Prematuro , Masculino , Oxigênio/sangue , Estudos Prospectivos , Volume de Ventilação Pulmonar , Sinais Vitais
11.
Bioresour Technol ; 297: 122448, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31771810

RESUMO

In this work, a single microbial electrochemical system was developed for multiple goals simultaneously - CO2 reduction, biogas purification, upgrading and sulfur recovery. This system consists of a methanogen-inoculated biocathode for CO2 reduction and a ferrous ion (Fe2+)-mediated abiotic anode for hydrogen sulfide (H2S) oxidation. In the cathodic chamber, methane production rate of 20.6 ± 1.0 µmol·h-1 and high upgrading level (up to 98.3% methane content) were achieved. In the anodic chamber, H2S was completely removed and selectively converted into elemental sulfur particles. The system showed stable performance during continuous operation for treating both pure CO2 and mixed gases, with a cathodic coulombic efficiency of up to 85.2%. This simple system holds a great potential for practical application for biogas upgrading and sulfur recovery from waste water/gases.


Assuntos
Biocombustíveis , Dióxido de Carbono , Metano , Enxofre , Águas Residuárias
12.
Oecologia ; 192(1): 273-280, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31768738

RESUMO

The global phenomenon of mangrove encroachment into saltmarshes has been observed across five continents. It has been proposed that this encroachment is driven in part by rising atmospheric CO2 concentration and reduced salinity in saltmarshes resulting from rising sea levels enhancing the establishment success of mangrove seedlings. However, this theory is yet to be empirically tested at the community-level. In this study, we examined the effect of CO2 and salinity on seedling growth of two mangrove species, Aegiceras corniculatum and Avicennia marina, grown individually and in a model saltmarsh community in a glasshouse experiment. We found that the shoot (210%) and root (91%) biomass of the saltmarsh species was significantly greater under elevated CO2. As a result, both mangrove species experienced a stronger competitive effect from the saltmarsh species under elevated CO2. Nevertheless, A. marina seedlings produced on average 48% more biomass under elevated CO2 when grown in competition with the saltmarsh species. The seedlings tended to allocate this additional biomass to growing taller suggesting they were light limited. In contrast, A. corniculatum growth did not significantly differ between CO2 treatments. However, it had on average 36% greater growth under seawater salinity compared to hypersaline conditions. Avicennia marina seedlings were not affected by salinity. From these results, we suggest that although CO2 and salinity are not universal drivers determining saltmarsh-mangrove boundaries, it is likely that rising atmospheric CO2 concentration and reduced salinity associated with sea level rise will enhance the establishment success of mangrove seedlings in saltmarshes, which may facilitate mangrove encroachment in the future.


Assuntos
Avicennia , Plântula , Biomassa , Dióxido de Carbono , Salinidade
13.
Life Sci ; 240: 117081, 2020 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-31756342

RESUMO

BACKGROUND AND GOAL OF THE STUDY: Pulmonary inflammation, increased vascular permeability, and pulmonary edema, occur in response to primary pulmonary infections like pneumonia but are also evident in endotoxemia or sepsis. Mechanical ventilation augments pre-existing lung injury and inflammation resulting from exposure to microbial products. The objective of this study was to test the hypothesis that low-tidal-volume prevent ventilation induced lung injury in sepsis. MATERIALS AND METHODS: 10-12-week-old male C57BL/6N-mice received an intraperitoneal (i.p.) injection with equipotent dosages of LPS, 1668-thioate, 1612-thioate, or PBS. 120 min after injection, mice were randomized to low- (LV, 7 ± 1 ml/kg) or high-tidal-volume (HV, 25 ± 1 ml/kg) ventilation. Hemodynamic and ventilatory parameters were recorded and inflammatory markers were analyzed form BAL that was generated after 90 minute ventilation. RESULTS AND DISCUSSION: Arterial blood pressures declined during mechanical ventilation in all groups. pO2 decreased in LPS injected and CO2 increased in sham, LPS, and 1612-thioate administered mice at 45 min and in 1668-thioate injected mice after 90 minute LV ventilation compared to respective HV groups. BAL protein concentrations increased in HV ventilated and 1668- or 1612-thioat pre-treated mice. BAL TNF-α protein concentrations increased in both LPS- and 1668-thioate-injected and IL-1ß protein concentrations only in LPS-injected and HV ventilated mice. Most notably, no increased protein concentrations were observed in any of the LV ventilated groups. CONCLUSION: We conclude that low-tidal-volume ventilation may be a potential strategy for the prevention of ventilator induced lung injury in a murine model of systemic TLR agonist induced lung injury.


Assuntos
Inflamação/terapia , Sepse/terapia , Volume de Ventilação Pulmonar , Lesão Pulmonar Induzida por Ventilação Mecânica/prevenção & controle , Animais , Pressão Arterial , Líquido da Lavagem Broncoalveolar , Dióxido de Carbono/sangue , Hemodinâmica , Inflamação/complicações , Inflamação/patologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Oxigênio/sangue , Mecânica Respiratória , Sepse/complicações , Sepse/patologia , Lesão Pulmonar Induzida por Ventilação Mecânica/patologia
14.
Bioresour Technol ; 297: 122417, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31759856

RESUMO

This study evaluates the effect of replacement of N2 with CO2 as atmosphere in catalytic pyrolysis of waste lignocellulosics with acidic and metal-modified zeolites, respectively, on the 16 EPA priority pollutant polycyclic aromatic hydrocarbons (PAHs) in bio-oils. By coupling solid phase extraction pretreatment with single ion monitoring detection, it is found that the replacement alleviates PAHs in bio-oil concerning synchronously abating the 16 PAHs with low, medium and high molecular weights, and the benzo[a]pyrene equivalent toxicity of bio-oil decreases. Meanwhile, CO2 decreases the content of small oxygenates, e.g. furans, ketones, acids, and increases phenolics and aromatics affording more stable and valuable bio-oils. Moreover, CO2 enhances carbon conversion efficiency, especially in combination with Fe-modified zeolite, which presents a synergistic effect. This study indicates the practical application of CO2 as an atmosphere in catalytic pyrolysis to improve the bio-oil quality by suppressing PAHs formation and adjusting compound constituent.


Assuntos
Hidrocarbonetos Policíclicos Aromáticos , Atmosfera , Dióxido de Carbono , Nitrogênio , Pirólise
15.
Water Res ; 170: 115299, 2020 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-31760360

RESUMO

The formation of carcinogenic N-nitrosamines from reactions between solvent amines and flue gas NOx is an important concern for the application of amine-based processes to capture CO2 post-combustion. Using an advanced test rig with interconnected absorber and desorber units, we evaluated the importance for N-nitrosamine formation of the desorber relative to the absorber, and any synergism between the two units. Variations in desorber temperature and in flue gas composition indicated that N-nitrosamine formation from fresh monoethanolamine (MEA) occurred predominantly in the absorber. N-nitrosamine formation was driven by high NO2 and O2 flue gas concentrations, although NO also contributed. In contrast, N-nitrosamine formation from piperazine (PZ) was driven by reactions with nitrite in the heated desorber, and accelerated concurrent with nitrite accumulation. A complementary experiment simulating aged MEA solvent (high nitrite, 1.5% sarcosine as a proxy of secondary amine degradation products) suggested the desorber becomes an order of magnitude more important than the absorber for N-nitrosamine formation. For fresh MEA solvent, increasing the desorber temperature from 110 °C to 130 °C promoted thermal decomposition of N-nitrosamines, reducing N-nitrosamine accumulation rates two-fold. Compared to the test rig, the prevailing practice of using separate absorber columns and autoclave-like treatments to mimic desorber units predicted the direction, but underestimated the magnitude of N-nitrosamine formation. Because N-nitrosamine accumulation rates are the net result of competing formation and thermal decomposition processes, use of continuously cycling test rigs may be necessary to understand the impacts of different operating conditions.


Assuntos
Carbono , Nitrosaminas , Aminas , Dióxido de Carbono , Nitritos
16.
Bioresour Technol ; 297: 122385, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31761625

RESUMO

This work mainly studied B. braunii adapted to different CO2 concentrations with cobalt enrichment, and developed a process for CO2 capture, hydrocarbon production and cobalt removal. The results showed that B. braunii favored rapid growth at 5.0% (v/v) CO2, and the highest biomass was 1.89 g.L-1 with 4.5 mg.L-1 of cobalt. Hydrocarbon productivity in high concentration CO2 (5.0% and 10.0%) with cobalt enrichment was higher than that in Chu 13 medium. The change in cobalt removal efficiency mainly corresponded to the growth of B. braunii. The LCE of B. braunii in cobalt-rich with high CO2 concentration (5.0% and 10.0%) was 15.7%, and 14.9%, respectively, which was higher than that in normal medium. CO2 fixation rates were also higher in cobalt enrichment coupled with high CO2 concentration. This study not only provides ideas for the removal of toxic metal cobalt, but also has great potential for CO2 biofixation.


Assuntos
Dióxido de Carbono , Clorófitas , Biomassa , Cobalto , Hidrocarbonetos
17.
Water Res ; 170: 115331, 2020 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-31811989

RESUMO

Inland lakes receive growing attentions on eutrophication and their roles in global carbon cycle. However, understanding how inland lakes contribute to global carbon cycle is seriously hampered due to a shortage of long-term records. This study investigated the carbon dioxide (CO2) flux from the Lake Taihu, a large (2400 km2) and shallow (mean depth 1.9 m) eutrophic lake in subtropical region, based on a long-term (2000-2015) measurement of the partial pressure of carbon dioxide (pCO2) at high spatiotemporal resolution. We found that the Lake Taihu was a significant source of atmospheric CO2 with an average CO2 emission flux at 18.2 ± 8.4 mmol m-2 d-1 (mean±1standard deviation) and a mean annual pCO2 value of 778 ± 169 µatm. The highest pCO2 and CO2 flux were observed in eutrophic zone with a high external input of carbon and nutrient, and the lowest in non-eutrophic zones with no direct external input of nutrient and carbon. A substantial seasonal pattern in pCO2 was observed, particularly in eutrophic pelagic area, and was significantly negatively correlated with chlorophyll a. Long-term measurement showed the interannual variation in annual lake CO2 dynamics, which was highly sensitive to human-induced nutrient input. Watershed input of carbon and nutrient leads to the high CO2 level, counterbalancing the in-lake primary production. All lines of evidence suggest that human activities may have predominate contribution to CO2 source in the Lake Taihu, and this mechanism might be widespread in global freshwater lakes.


Assuntos
Dióxido de Carbono , Lagos , Ciclo do Carbono , China , Clorofila A , Eutrofização , Humanos
18.
Water Res ; 170: 115327, 2020 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-31810031

RESUMO

Releases of greenhouse gases (GHGs) from the subsurface can result in atmospheric emissions and the degradation of water quality. These effects require attention in today's changing climate to properly quantify emissions, reduce risk and inform sound policy decisions. Flowing subsurface GHGs, including methane and carbon dioxide, present a risk in the form of two environmental expressions: i) to the atmosphere (surface expression) and ii) to shallow groundwater (aqueous expression). Results based on high-resolution observations in an analog experimental system and analytical modelling show that these expressions depend on the rate of gas flow and the velocity of the flowing groundwater. In deeper systems, the emission of flowing subsurface GHGs could be significantly limited by dissolution into groundwater, adversely impacting water resources without surficial evidence of an underlying issue. This work shows that mass transfer in the subsurface must be considered to quantify, monitor and mitigate risks of leaking subsurface GHGs.


Assuntos
Gases de Efeito Estufa , Dióxido de Carbono , Efeito Estufa , Metano , Óxido Nitroso
19.
Glob Chang Biol ; 26(1): 300-318, 2020 01.
Artigo em Inglês | MEDLINE | ID: mdl-31670435

RESUMO

With accumulation of carbon cycle observations and model developments over the past decades, exploring interannual variation (IAV) of terrestrial carbon cycle offers the opportunity to better understand climate-carbon cycle relationships. However, despite growing research interest, uncertainties remain on some fundamental issues, such as the contributions of different regions, constituent fluxes and climatic factors to carbon cycle IAV. Here we overviewed the literature on carbon cycle IAV about current understanding of these issues. Observations and models of the carbon cycle unanimously show the dominance of tropical land ecosystems to the signal of global carbon cycle IAV, where tropical semiarid ecosystems contribute as much as the combination of all other tropical ecosystems. Vegetation photosynthesis contributes more than ecosystem respiration to IAV of the global net land carbon flux, but large uncertainties remain on the contribution of fires and other disturbance fluxes. Climatic variations are the major drivers to the IAV of net land carbon flux. Although debate remains on whether the dominant driver is temperature or moisture variability, their interaction,that is, the dependence of carbon cycle sensitivity to temperature on moisture conditions, is emerging as key regulators of the carbon cycle IAV. On timescales from the interannual to the centennial, global carbon cycle variability will be increasingly contributed by northern land ecosystems and oceans. Therefore, both improving Earth system models (ESMs) with the progressive understanding on the fast processes manifested at interannual timescale and expanding carbon cycle observations at broader spatial and longer temporal scales are critical to better prediction on evolution of the carbon-climate system.


Assuntos
Dióxido de Carbono , Ecossistema , Carbono , Ciclo do Carbono , Fotossíntese , Temperatura Ambiente
20.
Glob Chang Biol ; 26(1): 200-218, 2020 01.
Artigo em Inglês | MEDLINE | ID: mdl-31580516

RESUMO

Production and consumption of nitrous oxide (N2 O), methane (CH4 ), and carbon dioxide (CO2 ) are affected by complex interactions of temperature, moisture, and substrate supply, which are further complicated by spatial heterogeneity of the soil matrix. This microsite heterogeneity is often invoked to explain non-normal distributions of greenhouse gas (GHG) fluxes, also known as hot spots and hot moments. To advance numerical simulation of these belowground processes, we expanded the Dual Arrhenius and Michaelis-Menten model, to apply it consistently for all three GHGs with respect to the biophysical processes of production, consumption, and diffusion within the soil, including the contrasting effects of oxygen (O2 ) as substrate or inhibitor for each process. High-frequency chamber-based measurements of all three GHGs at the Howland Forest (ME, USA) were used to parameterize the model using a multiple constraint approach. The area under a soil chamber is partitioned according to a bivariate log-normal probability distribution function (PDF) of carbon and water content across a range of microsites, which leads to a PDF of heterotrophic respiration and O2 consumption among microsites. Linking microsite consumption of O2 with a diffusion model generates a broad range of microsite concentrations of O2 , which then determines the PDF of microsites that produce or consume CH4 and N2 O, such that a range of microsites occurs with both positive and negative signs for net CH4 and N2 O flux. Results demonstrate that it is numerically feasible for microsites of N2 O reduction and CH4 oxidation to co-occur under a single chamber, thus explaining occasional measurement of simultaneous uptake of both gases. Simultaneous simulation of all three GHGs in a parsimonious modeling framework is challenging, but it increases confidence that agreement between simulations and measurements is based on skillful numerical representation of processes across a heterogeneous environment.


Assuntos
Dióxido de Carbono , Óxido Nitroso , Metano , Probabilidade , Solo
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