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Chemical weathering plays an important role in modulating Earth's climate. However, chemical weathering is usually influenced by multiple factors simultaneously (e.g., climate, topography and lithology), and it is difficult to understand how these variables modulate the effect of chemical weathering on atmospheric p CO 2. In this study, we collected and analyzed water chemistry and multiple isotopes (δ34S SO4 , δ18O SO4 and δ18O H2O) in the Bailong River catchment to decipher how these variables influence chemical weathering and its effect on atmospheric p CO 2. We used the Monte Carlo inversion model to partition the sources of major cations and SO 4 2 − , and the results reveal that carbonate weathering is the dominant source contributing cations in river. Sulfide oxidation is the most important source for SO 4 2 − and a supply-limited process that is highly dependent on slope. We thus think slope is main factor modulating the effect of chemical weathering on atmospheric p CO 2. Steep slope increases sulfide oxidation rate by elevating erosion, resulting in chemical weathering acting as a CO 2 source. In contrast, gentle slope could facilitate a thick regolith that contributes long-term silicate weathering and limits sulfide oxidation, resulting in chemical weathering acting as a CO 2 sink. And it has been found that the influence of temperature on chemical weathering becomes progressively pronounced with increasing altitude. This study investigated sulfide weathering in eroding Qinghai-Tibet Plateau, highlighting the geomorphologically controlled CO 2 effects of chemical weathering. • There is significant spatial heterogeneity in climate, topography and lithology, influencing rock weathering in the Bailong River. • Sulfide oxidation is the most important source for SO 4 2 − , and the contribution of sulfide oxidation to SO 4 2 − is highly dependent on slope. • Slope is the main factor modulating the effect of rock weathering on atmospheric p CO 2. • The effect of temperature on rock weathering becomes progressively more pronounced with increasing altitude. [ABSTRACT FROM AUTHOR]

Fertilizer application is key for plant yield promotion, but also has side effects on microbes, organic carbon storage and aggregate size distributions. However, links between these factors and especially how different amounts of organic and mineral fertilizers affect microbial-driven CO 2 release at the aggregate scale remains largely unknown. We quantified carbon decomposition gene abundance and diversity, microbial residual carbon and CO 2 release from the labile or stable carbon pools in three soil aggregate size fractions in organic and mineral fertilized soil. Compared to mineral fertilizer, organic fertilizer increased abundances of carbon decomposition genes, extracellular enzyme activities, microbial residual carbon and CO 2 released from the labile carbon pool, but decreased CO 2 released from the stable carbon pool in microaggregates. Likewise, organic fertilizer increased the proportion of macroaggregates, microbial residual carbon and CO 2 released from the labile carbon pool, but had no effect on carbon degradation gene abundance and extracellular carbon enzyme activity. Taken together, we illustrate that organic fertilizer application decreases CO 2 release via increasing the proportion of macroaggregates, leading to increased carbon storage that can provide a means to lessening atmospheric carbon. [Display omitted] • Organic fertilizer decreases CO 2 release via increasing macroaggregates fractions • Organic fertilizer increased carbon degradation gene abundances in microaggregates • Organic fertilizer decreased CO 2 release from the stable carbon pool in three aggregate fractions [ABSTRACT FROM AUTHOR]

Abstract Humification plays a critical role in the environmental fate of organic wastes, and MnO 2 holds great promise for enhancing this reaction. However, the effects of MnO 2 on the enhancement of the humification reaction remain ambiguous. To better reveal the mechanism by which MnO 2 enhances the reaction and investigate the fate of the humification products, abiotic humification experiments were performed using increasing concentrations of dissolved organic matter (DOM) to a fixed amount of MnO 2. DOM was represented by model humic precursors consisting of catechol, glucose and glycine. The results indicate that the reduction of MnO 2 played a dominant role in the formation of fulvic-like acids (FLAs), and the subsequent reduction products, MnOOH and Mn(II), acted as catalysts in the formation of humic-like acids (HLAs). Moreover, CO 2 release occurred during the formation of FLAs, and a strong linear correlation between CO 2 release and the formation of FLAs was observed (p < 0.01), where 0.73–1.87 mg of CO 2 was released per mg dissolved organic carbon (DOC) FLAs. Furthermore, the concentration of MnO 2 had a pronounced influence on the product behavior, where a lower MnO 2 concentration decreased the quantity of FLAs produced. Graphical abstract Proposed oxidation catalysis mechanisms of MnO 2 and the related reduction products in the abiotic humification of organic matter. Unlabelled Image [ABSTRACT FROM AUTHOR]

Highlights: [•] C mineralization process in urban soils is described by several kinetic models. [•] C mineralization in urban soils is related to many different features. [•] The kinetic models identify two differently degradable organic pools. [ABSTRACT FROM AUTHOR]

Abstract: High-speed CO2 release experiments from a pressurized vessel have been conducted for a range of storage pressures nozzle diameters. The experiments are conducted to validate and develop models for accidental releases of CO2 during transport. In cooperation with DNV-KEMA lab (Groningen, The Netherlands), medium scale experiments with a 500 liter tank have been designed and performed in spring of 2012. The results of this experiment are reported in a separate GHGT paper by Ahmad et al. [5]. In preparation of these experiments, some optical measurement techniques have been tested in a smaller set-up of a 1liter vessel, carried out at the TNO Rijswijk facility. These preparatory experiments will be discussed in the current document. A number of optical techniques are evaluated in relation to the observed phenomena. The tested techniques are: HD resolution standard optical camera, HS (high speed) camera and IR (infra-red) camera. In addition some experiments were performed using the PIV (Particle Image Velocimetry) technique, which is reported in a separate paper by de Jong et al. [4]. [Copyright &y& Elsevier]

Abstract: In the current work evaluation of CO2 release velocity profiles is determined using Particle Image Velocimetry (PIV). The formation of solid CO2 particles using the rapid expansion of nozzle flow is used as a seeder particle, making the method truly nonintrusive and negates the use of special seeder equipment. Preliminary tests have been conducted on low speed large CO2 particles. High-speed release PIV experiments have been conducted for a range of storage pressures between 60 and 150 bars using a 13mm (1/2 inch) diameter nozzle. The current paper is reporting combined research with a second paper by Dam et al. [4]. The current investigation is a small scale experiment prior to reported mid scale experiments reported in Ahmed et al. [5]. [Copyright &y& Elsevier]

Abstract: The release of non-condensable (NC) gases, essentially carbon dioxide, oxygen and nitrogen, from the evaporating brine in desalination distillers notably affects the heat transfer for condensation, the energy consumption, the performance and the material life span of the distillers. A better knowledge of CO2 release and of the interaction with the carbonate system in desalination distillers is very important for the design of the venting system and a stable distiller operation. Since CO2 release and scale formation are closely related to the carbonate system of the brine, a better understanding of CO2 release may contribute to the knowledge of scale formation in desalination distillers and improve scale prediction and prevention methods. A model has been developed for the prediction of the CO2 release rates in falling film evaporators with vertical tubes. The theory of mass transfer coupled with chemical reaction kinetics (chemical desorption) was applied to the problem of CO2 release. The mass transfer and the chemical reaction kinetics were studied for the conditions prevailing in falling film seawater evaporators. In addition to the CO2 release rates the model allows for calculation of the HCO3 −, CO3 2−, CO2, H+, and OH− concentrations in the carbonate system of the brine. The model was applied to a falling film evaporator at various operating conditions. The release rates of CO2 along the flow path of the falling film were determined. The paper presents the main principles of the model and discusses the simulation results. The effects of process parameters and the seawater properties such as evaporation temperature, seawater salinity, and pH value on the CO2 release rates are shown. Moreover, the paper discusses in which desorption regime (e.g. slow, fast, instantaneous) the CO2 release process takes place and whether the mass transfer is enhanced by the chemical reactions. [Copyright &y& Elsevier]

Abstract: The release of CO2 in multiple-effect distillers has scarcely been investigated and little has been published about it. There is no approach available to reliably predict the release rates in individual stages and the effects of influencing parameters. Until now the dimensioning of the design venting rates has been based mainly on experience and very sparse experimental data. The present work was aimed at gaining an in-depth understanding of the physical and chemical processes involved in CO2 release and the carbonate system in multiple-effect distillers. A model has been developed that describes the CO2 release and the carbonate system in multiple-effect distillers. Included is the flow path of brine through the final condenser and the evaporator stages. The desorption of CO2 was described as a problem of coupled mass transfer with chemical reaction. The mass transfer coefficient and the phase interface area were studied for the fluid dynamics of falling water films on horizontal tubes. [Copyright &y& Elsevier]

Abstract: Artificial covers were designed and used to study the effects of crust constraints on bread expansion and gas release during baking. The results were interpreted by comparison with the results of simulations using a mathematical model of baking. The cover levels were set at 45mm, 50mm and 55mm, as the maximum height reached by the dough without cover under the conditions studied was 60mm. MRI images were used to evaluate the local porosity of the crumb. Porosity kinetics showed that different cover levels resulted in densification within the crumb structure: the later the dough encountered the cover, the deeper the dense crumb formed in the loaf. The kinetics of CO2 release were monitored with an infrared detector and the results showed that the lower the cover level the shorter the induction time. The predominant role of crust setting in the CO2 release response was demonstrated. [Copyright &y& Elsevier]

Abstract: Scale formation in seawater distillers is mainly caused by crystallization of the inversely soluble salts calcium carbonate, magnesium hydroxide, and calcium sulphate. The formation of the alkaline scales CaCO3 and Mg(OH)2 strongly depends on temperature, pH, the release rate of CO2 as well as the concentrations of HCO3 −, CO3 2−, Ca2+, and Mg2+ ions. The release of CO2 from the evaporating brine shifts the pH to higher values and considerably influences the concentrations of HCO3 − and CO3 2− ions in the brine. Thus, it plays an important role in alkaline scale formation. Based on simulation results for the CO2 release and the carbonate system in a reference multiple-effect distiller, the scale forming potential was inferred from the composition of the brine by using the Langelier Saturation Index (LSI) and the Ryznar Stability Index (RSI). In the first stage of the reference distiller at a top brine temperature of 64 °C, the LSI based on the solubility product of aragonite increases from 1 on the first tube row to 1.5 on the last tube row. The RSI decreases from 5.9 on the first tube row to 5.0 on the last tube row. Thus it appears that the supersaturation with CaCO3 and the scale forming potential grow along the flow path of brine from the first to the last tube row. The LSI for the brine decreases from 1.5 at the outlet of the first stage to 1.3 at the outlet of the last stage. The RSI increases from 5.0 at the outlet of the first stage to 5.4 at the outlet of the last stage. Since the scaling tendency increases the more the Ryznar Stability Index falls below 6, scale formation is much more likely to occur in the high temperature stages. A larger quantity of scale is to be expected in the first stages on the lower tube rows. [Copyright &y& Elsevier]

Abstract: The knowledge of the CO2 release from the evaporating brine in multi-stage flash (MSF) and multiple-effect (ME) distillers is very important for the design, the operation, and the cost of desalination distillers as well as for the recarbonation of the distillate. The CO2 released in MSF plants can be used for the recarbonation of the distillate. The recarbonation method using CO2 from the vent gases of MSF plants has gained importance, since the post-treatment of potable water can be effected without additional CO2 production by combustion processes. The paper discusses if this approach may also be applied to ME distillers. The amounts of CO2 required for the recarbonation are compared with the amounts released. To this end, the CO2 release rates were calculated on the basis of two previously developed models. One consequence of the differences between MSF and ME systems regarding evaporation mechanisms, fluid flow, operating temperatures, and concentrations is that in MSF distillers the specific phase interface areas are lower and the mass transfer coefficients are higher compared to ME distillers. Consequently, the specific CO2 release in MSF plants is significantly higher than in ME plants. The total CO2 release in MSF recycle distillers amounts to about 82 g CO2 per ton of distillate at a top brine temperature of 100°C. The calculations show that, for the limestone/carbon dioxide method, MSF recycle distillers produce sufficient CO2 to allow recarbonation of the distillate up to an alkalinity of 187 ppm as CaCO3 at a top brine temperature of 100°C. The total CO2 release in ME distillers amounts to about 55 g CO2 per ton of distillate at a top brine temperature of 64°C. Utilizing the CO2 for the limestone recarbonation process would result in an alkalinity in the distillate of 124 ppm as CaCO3. Provided that the alkalinity values aimed at in the distillate range from 50 to 80 ppm as CaCO3, the calculations suggest that the CO2 release in ME distillers may be just sufficient in terms of stoichiometric consumption to allow for recarbonation using the limestone method. [Copyright &y& Elsevier]

A model has been developed that describes the CO2 release and the carbonate system in multiple-effect distillers. Included is the flow path of seawater through the final condenser and the evaporator stages. The desorption of CO2 was described as a problem of coupled mass transfer with chemical reaction.A computer program was written for simulating the CO2 release and the carbonate system. The CO2 release rates as well as the HCO3−, CO32−, CO2, H+ and OH− concentrations in the brine were simulated for a multiple-effect distiller with typical dimensions at various operating conditions. The effects of top brine temperature, concentration factor, seawater salinity and pH on CO2 release and the carbonate system were studied. The release rates of CO2 decrease from the first to the last stage. CO2 release increases with increasing top brine temperature. The total CO2 release (sum of the CO2 release in the stages) increases from about 14 g CO2 per ton of feed water at a top brine temperature of 60°C to about 18.2 g/t at 70°C. Between 14% and 18% of the total inorganic carbon content in the feed water is released as CO2. CO2 release rates increase with decreasing concentration factor. Relating the desorption rates to the feed water flow rates, the specific CO2 release increases with the concentration factor. CO2 release rises with increasing salinity and decreasing pH of the seawater. [Copyright &y& Elsevier]

Continuous changes in methane (CH4) and carbon dioxide (CO2) concentrations inside a closed chamber were measured on the forest floor at three sites: a deciduous forest and a coniferous forest in Hokkaido, Japan, and a birch forest in West Siberia, Russian Federation. Flux estimations by three types of regression methods, exponential, nonlinear, and linear, were examined using field-collected concentration data. The pattern of change with time of the gas concentration in the headspace differed, mainly according to site but also, to a lesser extent, according to the gas. This was a function of both the chamber height and surface soil property relating to soil gas diffusion and the gas concentration profile. Flux estimations did not differ statistically between the exponential and nonlinear methods for either gas at any site, because both of those regression methods were based on diffusion theory. However, the flux values estimated by linear regression were significantly different from those estimated by the other two methods for both CH4 and CO2 at the deciduous forest site and for CO2 at the coniferous forest site. Shortening the chamber deployment period improved the linearity of the curve, but did not completely eliminate the error. Our results suggest that linear regression is not a good model of the change in headspace concentration with time. [Copyright &y& Elsevier]

For predicting the CO2 release rates in multiple-effect distillers, the theory of desorption with chemical reaction was applied. The mass transfer processes and the reaction kinetics controlling the CO2 release were described. In the pH and temperature range found in the evaporator stages of multiple-effect distillers, the alkaline reaction mechanism with the steps CO2 + OH− ↔ HCO3− and HCO3− + OH− ↔ CO32− + H2O predominates. The reaction CO2 + OH− ↔ HCO3− is relatively slow, and therefore it is the rate-determining step in the reaction mechanism. Information for predicting mass transfer coefficients in water films flowing over horizontal tubes is still limited. Different approaches were shown. The phase interface area for CO2 release was described as the sum of the surface area of the liquid film on the tubes plus the surface area of the liquid between the tubes, assuming that liquid columns can be expected to occur between the tubes. Depending on the magnitude ofthe mass transfer coefficient, it was found that CO2 desorption from the evaporating brine either takes place in the transition regime from a slow to a fast reaction or in the fast reaction regime. Mass transfer and chemical reactions simultaneously take place in the boundary layer at the phase interface. Mass transfer is slightly enhanced by the reaction. The chemical rate constant becomes more important and the mass transfer coefficient less important in the correlation for the CO2 release rate. [Copyright &y& Elsevier]

Eucalypt litter, which decomposes slowly, exhibits a high content of phenolic compounds, and the disappearance of these compounds during decomposition is expected to improve faunal consumption, litter decomposition and incorporation into the soil. The aim of this study was to measure the disappearance rate of the phenolic compounds in eucalypt litter during laboratory and field decomposition. The outstanding result was the fast disappearance of soluble phenolic compounds and tannins, either in vitro or in the field. Laboratory experiments suggested that the rapid loss of phenolics observed during decomposition could not be ascribed to leaching only, and that degradation might play an important part. When initial litter quality is taken into account in the interpretation of decomposition studies, the disappearance rate of soluble phenolics, should also be considered. [Copyright &y& Elsevier]

• Mass and CO 2 efflux of the litter retained within a 40-m tall canopy were measured. • Mass of the retained litter was the greatest at a height of 0–2 m. • CO 2 efflux from the retained litter did not differ with height. • The retained litter sporadically contributed to carbon storage. • The retained litter contributed little to aboveground carbon release. Litter usually drops to the ground, but some is retained within the canopy. Mass and CO 2 efflux from retained litter may play a significant role in carbon cycling in tropical rainforests where emergent trees with complicated canopy structures are observed. This study aimed to show vertical variation in the mass and CO 2 efflux (R litter) of the retained litter and examined its contribution to carbon cycling in a Bornean tropical rainforest. The retained litter was collected from six 40 m tall columns with a radius of 1.6 m using an 85 m tall crane at six subplots. Dry mass and R litter were measured in the laboratory. The mass of the retained litter from the sampling points ranged from 0.35 g to 187.0 g, and R litter of the retained litter (42.4 ± 43.4 mg CO 2 kg−1 h −1) was significantly lower than that of the soil surface litter (85.9 ± 39.2 mg CO 2 kg−1 h −1) because of the lower water content in the retained litter. The mean mass of the retained litter measured from the ground to the canopy was 40.6 ± 22.2 g m −2. The greatest mass was observed at a height of 0–2 m. The ratio of the retained litter mass to the soil surface litter mass ranged from 1.0 to 11.5% with a mean of 5.2%, suggesting that litter retained within the canopy can contribute to carbon storage in this forest. On the other hand, R litter did not differ with height, and the ratio of R litter to aboveground autotrophic respiration was less than 1%. This study is the first to show that the litter retained within the canopy can sporadically be a moderate hot spot for C storage, but it is not a significant source of released CO 2. [ABSTRACT FROM AUTHOR]

• Oxygen isotopes in river water sulfate enable partitioning of sulfate source. • Isotope data demonstrates 56% of sulfate in the Mekong River is derived from pyrite. • Pyrite oxidation releases CO 2 through weathering of carbonates with sulfuric acid. • Carbon consumption from silicate weathering offset in large rivers. The weathering of carbonate rocks with sulfuric acid releases carbon dioxide (CO 2) to the atmosphere, offsetting the CO 2 drawdown from carbonic acid weathering of silicates thought to regulate global climate. Quantifying CO 2 release from sulfuric acid weathering requires the partitioning of riverine sulfate between its two main sources: sedimentary sulfate and sulfide. Although the sulfur (δ 34 S S O 4 ) and oxygen (δ 18 O S O 4 ) isotope ratios of sedimentary sulfates (gypsum and anhydrite) of different ages are well constrained, the δ 34 S of sulfide minerals is highly variable, restricting the utility of δ 34 S for partitioning sulfur sources. Here, we use oxygen isotope ratios in the river water (δ 18 O H 2 O) and sulfate molecules (δ 18 O S O 4 ) to partition the fraction of sulfate and associated uncertainty delivered by the oxidative weathering of pyrite (f pyr). The partitioning is illustrated using the Mekong River, one of the world's largest river basins, presenting new δ 18 O S O 4 , δ 18 O H 2 O and δ 34 S S O 4 data collected on 18 tributaries and 6 mainstem sites over two field seasons at peak flux. The geological, geomorphological and climatic diversity of the Mekong River basin make it an ideal field site to quantify the role of sulfuric acid weathering and its implications for the carbon cycle. There is a 12‰ range in both the difference between δ 18 O S O 4 and δ 18 O H 2 O (Δ 18 O S O 4 − H 2 O) and δ 34 S in the river waters of the basin. In the Mekong tributaries, sources of sulfate are highly variable with the fraction of sulfate derived from pyrite oxidation (f pyr) ranging from 0.19 to 0.84. In the mainstem, f pyr reflects the flux-weighted mean of these tributary inputs, with 56 ± 7 % (1 σ) of the sulfate delivered to the ocean at the Mekong mouth being derived from the oxidative weathering of pyrite. As a result, we estimate that ∼70% of CO 2 consumed through silicate weathering in the Mekong basin is offset by the release of CO 2 via the dissolution of carbonates by sulfuric acid. [ABSTRACT FROM AUTHOR]

• Real-time monitoring of CO 2 release. • Measurements of water column pH and pCO 2 via towed Video-CTD system. • Assessment of towed sensors capacity to detect potential CO 2 leakage in the water column. • Estimation of thresholds for the detection of anomalous pCO 2. Within the framework of the STEMM-CCS project, a controlled CO 2 release experiment was conducted under real-life conditions in the Goldeneye complex area, a depleted gas field located in the UK sector of the North Sea. Here, the viability of water column monitoring for the detection of the injected CO 2 is evaluated. Real-time pH and pCO 2 measurements were taken in the water column during the CO 2 release experiment. Monitoring was carried out throughout the full water column, from the near-seafloor to the sea surface, in order to assess the spatial extent of the CO 2 release. The dispersion of the CO 2 plume was strongly influenced by tidal circulation in the area. The strongest signals were detected within 8 m of the bubble stream during low tide. The lowest pH and highest pCO 2 values were 7.965 and 942.1 µatm, respectively, corresponding to variations of 16.4% [ H +] and 125.6% from baseline values. The pCO 2 baseline dynamics of Goldeneye area were assessed by the evaluation of the natural pCO 2 -O 2 covariance. The estimation of seasonal thresholds for anomalous pCO 2 (pCO 2 :O 2 ratio May = 1.63 ± 0.04) allowed us to assess with confidence the non-biological origin of the detected CO 2 during the release experiment. [ABSTRACT FROM AUTHOR]

• Weather, soil moisture, CO 2 concentration and fluxes were monitored for 965 days in South Korea. • Heterogeneities of soils have little effect on simulated CO 2 fluxes. • Increased soil moisture content results to high CO 2 concentration in soil profile. In Eumseong, Republic of Korea, a controlled CO 2 release site was designed by Korea CO 2 Storage Environmental Management (K-COSEM) Research Center to evaluate properly integrated CO 2 monitoring tools at the soil surface. CO 2 was released from the 55 m-length PVC-pipe buried at 2.5 m-depth, and then, CO 2 concentration and flux were monitored from August 1, 2015 to March 21, 2018 (965 days). Influencing environmental factors such as meteorological data, soil moisture and temperature at 5 different depths were monitored concurrently. The measured soil moisture content decreased rapidly when the soil temperature dropped below 0 °C. When CO 2 release began, both surface CO 2 flux and soil CO 2 concentration increased with a time lag. However, with occurrence of precipitation events, CO 2 flux decreased to almost 0 cm3 cm−2 day−1 but soil CO 2 concentration increased rapidly. The HYDRUS-SOILCO2 predicted soil moisture, temperature and natural background CO 2 flux compared to measured data (R2 = 0.74, 0.89, and 0.85). The 10 scenarios were constructed with different soil characteristic curves. Unlike soil moisture content, the simulated natural CO 2 flux did not depend heavily on soil characteristics. The mass of released CO 2 was estimated by the difference between the measured CO 2 flux data during the release test and natural CO 2 prediction model. At the 2nd CO 2 release test, there was 1.5 times difference between the actual released CO 2 mass and calculated CO 2 mass. [ABSTRACT FROM AUTHOR]