Greenhouse Effects due to Man-Mad Perturbations of Trace Gases

Dynamical Janus-Like Behavior Excited by Passive Cold-Heat Modulation in the Earth-Sun/Universe System: Opportunities and Challenges

The utilization of solar-thermal energy and universal cold energy has led to many innovative designs that achieve effective temperature regulation in different application scenarios. Numerous studies on passive solar heating and radiation cooling often operate independently (or actively control the conversion) and lack a cohesive framework for deep connections. This work provides a concise overview of the recent breakthroughs in solar heating and radiation cooling by employing a mechanism material in the application model. Furthermore, the utilization of dynamic Janus-like behavior serves as a novel nexus to elucidate the relationship between solar heating and radiation cooling, allowing for the analysis of dynamic conversion strategies across various applications. Additionally, special discussions are provided to address specific requirements in diverse applications, such as optimizing light transmission for clothing or window glass. Finally, the challenges and opportunities associated with the development of solar heating and radiation cooling applications are underscored, which hold immense potential for substantial carbon emission reduction and environmental preservation. This work aims to ignite interest and lay a solid foundation for researchers to conduct in-depth studies on effective and self-adaptive regulation of cooling and heating.

Light absorption potential of water-soluble organic aerosols in the two polluted urban locations in the central Indo-Gangetic Plain

PM_2.5 (particulate matter having aerodynamic diameter ≤2.5 μm) samples were collected during wintertime from two polluted urban sites (Allahabad and Kanpur) in the central Indo-Gangetic Plain (IGP) to comprehend the sources and atmospheric transformations of light-absorbing water-soluble organic aerosol (WSOA). The aqueous extract of each filter was atomized and analyzed in a high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS). Water-soluble organic carbon (WSOC) and WSOA concentrations at Kanpur were ∼1.2 and ∼1.5 times higher than that at Allahabad. The fractions of WSOC and secondary organic carbon (SOC) to total organic carbon (OC) were also significantly higher ∼53% and 38%, respectively at Kanpur compared to Allahabad. This indicates a higher abundance of oxidized WSOA at Kanpur. The absorption coefficient (b_abs-365) of light-absorbing WSOA measured at 365 nm was 46.5 ± 15.5 Mm^-1 and 73.2 ± 21.6 Mm^-1 in Allahabad and Kanpur, respectively, indicating the dominance of more light-absorbing fractions in WSOC at Kanpur. The absorption properties such as mass absorption efficiency (MAE₃₆₅) and imaginary component of refractive index (k_abs-365) at 365 nm at Kanpur were also comparatively higher than Allahabad. The absorption forcing efficiency (Abs SFE; indicates warming effect) of WSOA at Kanpur was ∼1.4 times higher than Allahabad. Enhancement in light absorption capacity was observed with the increase in f44/f43 (fraction of m/z 44 (f44) to 43 (f43) in organic mass spectra) and O/C (oxygen to carbon) ratio of WSOA at Kanpur while no such trend was observed for the Allahabad site. Moreover, the correlation between carbon fractions and light absorption properties suggested the influence of low-volatile organic compounds (OC3 + OC4 fraction obtained from thermal/optical carbon analyzer) in increasing the light absorption capacity of WSOA in Kanpur.

Mitigating climate disruption in time: A self-consistent approach for avoiding both near-term and long-term global warming

This study clarifies the need for comprehensive CO₂ and non-CO₂ mitigation approaches to address both near-term and long-term warming. Non-CO₂ greenhouse gases (GHGs) are responsible for nearly half of all climate forcing from GHG. However, the importance of non-CO₂ pollutants, in particular short-lived climate pollutants, in climate mitigation has been underrepresented. When historical emissions are partitioned into fossil fuel (FF)- and non-FF-related sources, we find that nearly half of the positive forcing from FF and land-use change sources of CO₂ emissions has been masked by coemission of cooling aerosols. Pairing decarbonization with mitigation measures targeting non-CO₂ pollutants is essential for limiting not only the near-term (next 25 y) warming but also the 2100 warming below 2 °C.

The ongoing and projected impacts from human-induced climate change highlight the need for mitigation approaches to limit warming in both the near term (<2050) and the long term (>2050). We clarify the role of non-CO₂ greenhouse gases and aerosols in the context of near-term and long-term climate mitigation, as well as the net effect of decarbonization strategies targeting fossil fuel (FF) phaseout by 2050. Relying on Intergovernmental Panel on Climate Change radiative forcing, we show that the net historical (2019 to 1750) radiative forcing effect of CO₂ and non-CO₂ climate forcers emitted by FF sources plus the CO₂ emitted by land-use changes is comparable to the net from non-CO₂ climate forcers emitted by non-FF sources. We find that mitigation measures that target only decarbonization are essential for strong long-term cooling but can result in weak near-term warming (due to unmasking the cooling effect of coemitted aerosols) and lead to temperatures exceeding 2 °C before 2050. In contrast, pairing decarbonization with additional mitigation measures targeting short-lived climate pollutants and N₂O, slows the rate of warming a decade or two earlier than decarbonization alone and avoids the 2 °C threshold altogether. These non-CO₂ targeted measures when combined with decarbonization can provide net cooling by 2030 and reduce the rate of warming from 2030 to 2050 by about 50%, roughly half of which comes from methane, significantly larger than decarbonization alone over this time frame. Our analysis demonstrates the need for a comprehensive CO₂ and targeted non-CO₂ mitigation approach to address both the near-term and long-term impacts of climate disruption.

Combined Effect of Catholyte Gap and Cell Voltage on Syngas Ratio in Continuous CO2/H2O Co-electrolysis

Electrochemical devices are constructed for continuous syngas (CO + H2) production with controlled selectivity between CO2 and proton reduction reactions. The ratio of CO to H2, or the faradaic efficiency toward CO generation, was mechanically manipulated by adjusting the space volume between the cathode and the polymer gas separator in the device. In particular, the area added between the cathode and the ion-conducting polymer using 0.5 M KHCO3 catholyte regulated the solution acidity and proton reduction kinetics in the flow cell. The faradaic efficiency of CO production was controlled as a function of the distance between the polymer separator and cathode in addition to that manipulated by the electrode potential. Further, the electrochemical CO2 reduction device using Au NPs presented a stable operation for more than 23 h at different H2:CO production levels, demonstrating the functional stability of the flow cell utilizing the mechanical variable as an important operational factor.

Dramatic source-sink transition of N2O in the water level fluctuation zone of the Three Gorges Reservoir during flooding-drying processes

Biogeochemical cycling of nitrous oxide (N₂O), a significant greenhouse gas (GHG), can influence global climate change. The production and emission of N₂O mediated by hydrological regimes is particularly active in water level fluctuation zones (WLFZs). However, the hydrological mechanisms affecting N₂O transformation and production across the water-sediment micro-interface remain unclear. In this study, intact sediment cores from the WLFZs of the Three Gorges Reservoir (TGR) were incubated for 24 days in a laboratory microcosm to identify the effects of the flooding-drying processes on the yield and emission of N₂O. Results showed a source-sink transition of N₂O in the first 1.5 days during the flooding period, with the water column subsequently acting as a sink relative to the atmosphere in the following experimental period. The source-sink transition was ascribed to changes in oxygen concentration in the water column and sediment regulation of NO₃^--N transformation, resulting in denitrification and N₂O production. Preliminary estimates on the mass budget of N₂O in a typical WLFZs of the TGR showed slight emission fluxes, ranging from 13.08 to 43.08 μmol m^-2 from flooding period to drying process. Although these N₂O emissions were relatively low, the emission peak detected during the initial period (first 1.5 days) of the flooding phase provides important knowledge on the mitigation of GHG emissions from hydropower sources, which should be incorporated into future reservoir operations.

Reaction of the hydrogen atom with nitrous oxide in aqueous solution – pulse radiolysis and theoretical study

The UB3LYP/cc-pVTZ computations using three solvent models and pulse radiolysis measurements show predominance of the direct reaction path via [H–ONN]^‡ in aqueous solution.

Remifentanil in Combination With Propofol Is Suitable for Use in the Dental Outpatient Setting

Although several adjuncts to the general anesthetic propofol have been proposed, there is insufficient research identifying the ideal agent, and in what dosage, to combine with propofol in dental outpatient anesthesia. Here we examined the combination of remifentanil or nitrous oxide and propofol in patients with severe dental avoidance undergoing dental treatment in the outpatient setting. Eighty patients were randomized to 4 groups and administered propofol/saline solution (PS; n = 20), propofol/remifentanil 0.25 μg/kg/min (PRe-0.25; n = 20), propofol/remifentanil 0.125 μg/kg/min (PRe-0.125; n = 20), or propofol/66% nitrous oxide (PN; n = 20). During anesthesia, the bispectral index value was kept between 40 and 60. Body movements and hemodynamic changes during anesthesia, emergence, and recovery as well as anesthetic cost were compared between the combinations. Body movements were observed in all patients administered PS but in no patients administered PRe-0.25, PRe-0.125, or PN. Postoperative nausea was observed in 5 patients (25%) administered PRe-0.25 and in 1 patient (5%) administered PN. Although both PRe-0.125 and PN were useful clinically, PRe-0.125 was the least expensive combination.

Bacterial community composition and predicted functional ecology of sponges, sediment and seawater from the thousand islands reef complex, West Java, Indonesia

In the present study, we assessed the composition of Bacteria in four biotopes namely sediment, seawater and two sponge species (Stylissa massa and Xestospongia testudinaria) at four different reef sites in a coral reef ecosystem in West Java, Indonesia. In addition to this, we used a predictive metagenomic approach to estimate to what extent nitrogen metabolic pathways differed among bacterial communities from different biotopes. We observed marked differences in bacterial composition of the most abundant bacterial phyla, classes and orders among sponge species, water and sediment. Proteobacteria were by far the most abundant phylum in terms of both sequences and Operational Taxonomic Units (OTUs). Predicted counts for genes associated with the nitrogen metabolism suggested that several genes involved in the nitrogen cycle were enriched in sponge samples, including nosZ, nifD, nirK, norB and nrfA genes. Our data show that a combined barcoded pyrosequencing and predictive metagenomic approach can provide novel insights into the potential ecological functions of the microbial communities. Not only is this approach useful for our understanding of the vast microbial diversity found in sponges but also to understand the potential response of microbial communities to environmental change.

The evolution of respiratory O2/NO reductases: an out-of-the-phylogenetic-box perspective

Complex life on our planet crucially depends on strong redox disequilibria afforded by the almost ubiquitous presence of highly oxidizing molecular oxygen. However, the history of O2-levels in the atmosphere is complex and prior to the Great Oxidation Event some 2.3 billion years ago, the amount of O2 in the biosphere is considered to have been extremely low as compared with present-day values. Therefore the evolutionary histories of life and of O2-levels are likely intricately intertwined. The obvious biological proxy for inferring the impact of changing O2-levels on life is the evolutionary history of the enzyme allowing organisms to tap into the redox power of molecular oxygen, i.e. the bioenergetic O2 reductases, alias the cytochrome and quinol oxidases. Consequently, molecular phylogenies reconstructed for this enzyme superfamily have been exploited over the last two decades in attempts to elucidate the interlocking between O2 levels in the environment and the evolution of respiratory bioenergetic processes. Although based on strictly identical datasets, these phylogenetic approaches have led to diametrically opposite scenarios with respect to the history of both the enzyme superfamily and molecular oxygen on the Earth. In an effort to overcome the deadlock of molecular phylogeny, we here review presently available structural, functional, palaeogeochemical and thermodynamic information pertinent to the evolution of the superfamily (which notably also encompasses the subfamily of nitric oxide reductases). The scenario which, in our eyes, most closely fits the ensemble of these non-phylogenetic data, sees the low O2-affinity SoxM- (or A-) type enzymes as the most recent evolutionary innovation and the high-affinity O2 reductases (SoxB or B and cbb3 or C) as arising independently from NO-reducing precursor enzymes.

Carbon acquisition and accumulation in microalgae Chlamydomonas: Insights from "omics" approaches

Understanding the processes and mechanisms of carbon acquisition and accumulation in microalgae is fundamental to enhance the cellular capabilities aimed to environmental and industrial applications. The "omics" approaches have greatly contributed to expanding the knowledge on these carbon-related cellular responses, reporting large data sets on microalgae transcriptome, proteome and metabolome. This review emphasizes the advances made on Chlamydomonas exploration; however, some knowledge acquired from studying this model organism, may be extrapolated to close algae species. The large data sets available for this organism revealed the identity of a vast range of genes and proteins which are integrating carbon-related mechanisms. Nevertheless, these data sets have also highlighted the need for integrative analysis in order to fully explore the information enclosed. Here, some of the main results from "omics" approaches which may contribute to the understanding of carbon acquisition and accumulation in Chlamydomonas were reviewed and possible applications were discussed.

BIOLOGICAL SIGNIFICANCE

A number of important publications in the field of "omics" technologies have been published reporting studies of the model green microalga Chlamydomonas reinhardtii and related to microalgal biomass production. However, there are only few attempts to integrate these data. Publications showing the results from "omics" approaches, such as transcriptome, metabolome and proteome, focused in the study of mechanisms of carbon acquisition and accumulation in microalgae were reviewed. This review contributes to highlight the knowledge recently generated on such "omics" studies and it discusses how these results may be important for the advance of applied sciences, such as microalgae biotechnology.

Evaluation of photoacoustic infrared spectroscopy for simultaneous measurement of N2 O and CO2 gas concentrations and fluxes at the soil surface

Simultaneous measurement of N2 O and CO2 flux at the soil surface with photoacoustic infrared spectroscopy (PAS) is gaining popularity due to portability, low maintenance, and ease-of-operation. However, the ability of PAS to measure N2 O with accuracy and precision similar to gas chromatography (GC) is uncertain due to overlap in N2 O, CO2 , and H2 O absorbance spectra combined with the large range in analyte concentrations. We tested the ability of six PAS units to simultaneously measure N2 O and CO2 gas concentrations and fluxes with accuracy and precision similar to two GC units. We also evaluated H2 O vapor and CO2 interferences with N2 O measurement. The accuracy and precision of standard gas concentration measurements with PAS and GC were similar. High water vapor (~26 600 ppm) and CO2 concentrations (~4500 ppm) did not interfere with N2 O measurement across the concentration range typically observed in static flux chambers at the soil surface (~0.5-3.0 ppm N2 O). On average, N2 O fluxes measured with the six PAS were 4.7% higher than one GC and 9.9% lower than the second GC.

Denitrification and total nitrate uptake in streams of a tropical landscape

Rapid increases in nitrogen (N) loading are occurring in many tropical watersheds, but the fate of N in tropical streams is not well documented. Rates of nitrate uptake and denitrification were measured in nine tropical low-order streams with contrasting land use as part of the Lotic Intersite Nitrogen eXperiment II (LINX II) in Puerto Rico using short term (24-hour) additions of K(15)NO3 and NaBr. Background nitrate concentrations ranged from 105 to 997 microg N/L, and stream nitrate uptake lengths were long, varying from 315 to 8480 m (median of 1200 m). Other indices of nitrate uptake (mass transfer coefficient, V(f) [cm/s], and whole-stream nitrate uptake rate, U [microg N m(-2) s(-1)]) were low in comparison to other regions and were related to chemical, biological, and physical parameters. Denitrification rates were highly variable (0-133 microg N m(-2) min(-1); median = 15 microg N m(-2) min(-1)), were dominated by the end product N2 (rather than N2O), and were best predicted by whole-stream respiration rates and stream NO3 concentration. Denitrification accounted for 1-97% of nitrate uptake with five of nine streams having 35% or more of nitrate uptake via denitrification, showing that denitrification is a substantial sink for nitrate in tropical streams. Whole-stream nitrate uptake and denitrification in our study streams closely followed first-order uptake kinetics, indicating that NO3 uptake is limited by delivery of substrate (NO3) to the organisms involved in uptake or denitrification. In the context of whole-catchment nitrogen budgets, our finding that in-stream denitrification results in lower proportional production of N2O than terrestrial denitrification suggests that small streams can be viewed as the preferred site of denitrification in a watershed in order to minimize greenhouse gas N2O emissions. Conservation of small streams is thus critical in tropical ecosystem management.

Termites: a potentially large source of atmospheric methane, carbon dioxide, and molecular hydrogen

Termites may emit large quantities of methane, carbon dioxide, and molecular hydrogen into the atmosphere. Global annual emissions calculated from laboratory measurements could reach 1.5 x 10(14) grams of methane and 5 x 10(16) grams of carbon dioxide. As much as 2 x 10(14) grams of molecular hydrogen may also be produced. Field measurements of methane emissions from two termite nests in Guatemala corroborated the laboratory results. The largest emissions should occur in tropical areas disturbed by human activities.

Nitrous oxide from soil denitrification: factors controlling its biological production

Increasing concentrations of nitrate, nitrite, and molecular oxygen enhanced production of nitrous oxide relative to molecular nitrogen during denitrification in soils. Soil acidity interacted with nitrate to increase the ratio of nitrous oxide to molecular nitrogen. In response to anoxic conditions, nitrous oxide production initially increased but nitrous oxide was then consumed, a pattern which resulted from the sequential synthesis of nitrogenous oxide reductases.

Variability of antarctic sea ice: and changes in carbon dioxide

A definitive long-term decrease in the extent of antarctic sea ice is not detectable from 9 years (1973 to 1981) of year-round satellite observations and limited prior data. Regional interannual variability is large, with sea ice decreasing in some regions while increasing in others. A significant decrease in overall ice extent during the mid-1970's, previously suggested to reflect warming induced by carbon dioxide, has not been maintained. In particular, the extent of ice in the Weddell Sea region has rebounded after a large decrease concurrent with a major oceanographic anomaly, the Weddell polynya. Over the 9 years, the trends are nearly the same in all seasons, but for periods of 3 to 5 years, greater winter ice maxima are associated with lesser summer ice minima. The decrease of the mid-1970's was preceded by an increase in ice extent from 1966 to 1972, further indicating the presence of cyclical components of variation that obscure any long-term trends that might be caused by a warming induced by carbon dioxide.

Climate impact of increasing atmospheric carbon dioxide

The global temperature rose by 0.2 degrees C between the middle 1960's and 1980, yielding a warming of 0.4 degrees C in the past century. This temperature increase is consistent with the calculated greenhouse effect due to measured increases of atmospheric carbon dioxide. Variations of volcanic aerosols and possibly solar luminosity appear to be primary causes of observed fluctuations about the mean trend of increasing temperature. It is shown that the anthropogenic carbon dioxide warming should emerge from the noise level of natural climate variability by the end of the century, and there is a high probability of warming in the 1980's. Potential effects on climate in the 21st century include the creation of drought-prone regions in North America and central Asia as part of a shifting of climatic zones, erosion of the West Antarctic ice sheet with a consequent worldwide rise in sea level, and opening of the fabled Northwest Passage.

Mount agung eruption provides test of a global climatic perturbation

The Mount Agung volcanic eruption in 1963 provides the best-documented global radiative perturbation to the earth's atmosphere currently available. Data on stratospheric aerosols produced by this eruption have been used as input to a model for the atmospheric thermal structure. The computed magnitude, sign, and phase lag of the temperature changes in both the stratosphere and the troposphere are in good agreement with observations, providing evidence that the climatic response to a global radiative perturbation is significant, as well as support for the use of theoretical models to predict climatic effects.

Greenhouse gases, radiative forcing, global warming potential and waste management--an introduction

Management of post-consumer solid waste contributes to emission of greenhouse gases (GHGs) representing about 3% of global anthropogenic GHG emissions. Most GHG reporting initiatives around the world utilize two metrics proposed by the Intergovernmental Panel on Climate Change (IPCC): radiative forcing (RF) and global warming potential (GWP). This paper provides a general introduction of the factors that define a GHG and explains the scientific background for estimating RF and GWP, thereby exposing the lay reader to a brief overview of the methods for calculating the effects of GHGs on climate change. An objective of this paper is to increase awareness that the GWP of GHGs has been re-adjusted as the concentration and relative proportion of these GHGs has changed with time (e.g., the GWP of methane has changed from 21 to 25 CO(2)-eq). Improved understanding of the indirect effects of GHGs has also led to a modification in the methodology for calculating GWP. Following a presentation of theory behind GHG, RF and GWP concepts, the paper briefly describes the most important GHG sources and sinks in the context of the waste management industry. The paper serves as a primer for more detailed research publications presented in this special issue of Waste Management & Research providing a technology-based assessment of quantitative GHG emissions from different waste management technologies.

Agricultural opportunities to mitigate greenhouse gas emissions

Agriculture is a source for three primary greenhouse gases (GHGs): CO(2), CH(4), and N(2)O. It can also be a sink for CO(2) through C sequestration into biomass products and soil organic matter. We summarized the literature on GHG emissions and C sequestration, providing a perspective on how agriculture can reduce its GHG burden and how it can help to mitigate GHG emissions through conservation measures. Impacts of agricultural practices and systems on GHG emission are reviewed and potential trade-offs among potential mitigation options are discussed. Conservation practices that help prevent soil erosion, may also sequester soil C and enhance CH(4) consumption. Managing N to match crop needs can reduce N(2)O emission and avoid adverse impacts on water quality. Manipulating animal diet and manure management can reduce CH(4) and N(2)O emission from animal agriculture. All segments of agriculture have management options that can reduce agriculture's environmental footprint.

Inhibition of NO3- and NO2- reduction by microbial Fe(III) reduction: evidence of a reaction between NO2- and cell surface-bound Fe2+

A recent study (D. C. Cooper, F. W. Picardal, A. Schimmelmann, and A. J. Coby, Appl. Environ. Microbiol. 69:3517-3525, 2003) has shown that NO(3)(-) and NO(2)(-) (NO(x)(-)) reduction by Shewanella putrefaciens 200 is inhibited in the presence of goethite. The hypothetical mechanism offered to explain this finding involved the formation of a Fe(III) (hydr)oxide coating on the cell via the surface-catalyzed, abiotic reaction between Fe(2+) and NO(2)(-). This coating could then inhibit reduction of NO(x)(-) by physically blocking transport into the cell. Although the data in the previous study were consistent with such an explanation, the hypothesis was largely speculative. In the current work, this hypothesis was tested and its environmental significance explored through a number of experiments. The inhibition of approximately 3 mM NO(3)(-) reduction was observed during reduction of a variety of Fe(III) (hydr)oxides, including goethite, hematite, and an iron-bearing, natural sediment. Inhibition of oxygen and fumarate reduction was observed following treatment of cells with Fe(2+) and NO(2)(-), demonstrating that utilization of other soluble electron acceptors could also be inhibited. Previous adsorption of Fe(2+) onto Paracoccus denitrificans inhibited NO(x)(-) reduction, showing that Fe(II) can reduce rates of soluble electron acceptor utilization by non-iron-reducing bacteria. NO(2)(-) was chemically reduced to N(2)O by goethite or cell-sorbed Fe(2+), but not at appreciable rates by aqueous Fe(2+). Transmission and scanning electron microscopy showed an electron-dense, Fe-enriched coating on cells treated with Fe(2+) and NO(2)(-). The formation and effects of such coatings underscore the complexity of the biogeochemical reactions that occur in the subsurface.

Increase of nitrous oxide flux to the atmosphere upon nitrogen addition to red mangroves sediments

Response of nitrous oxide N20 sediment/air flux to nitrogen addition was assessed in mangrove (Rhizophora mangle) sediments. Fluxes were enhanced with both ammonium and nitrate loading. Greatest fluxes (52 micromol m(-2) h(-1)) were obtained with ammonium addition and saturation was achieved with additions of 0.9 mol m(-2). Maximum flux following ammonium addition was 2785 times greater than control plots and 4.5 times greater during low tide than with equivalent ammonium addition at high tide. Nitrate enrichment resulted in exponential growth, with maximal mean flux of 36.7 micromolm(-2) h(-1) at 1.9 molm(-2); saturation was not achieved. Differential response to ammonium and nitrate, and to tide and elevation, indicate that microbial nitrification is responsible for most of the observed gas flux. Mangrove sediments constitute an important source of global atmospheric N20 and increases in nitrogen loading will lead to significant increases in the flux of this atmospherically active gas.