Solubility Of CO2 In Seawater Research Articles

Marine Heatwave and Terrestrial Drought Reduced CO2 Uptake in the East China Sea in 2022

Against the background of climate warming, marine heatwaves (MHWs) and terrestrial drought events have become increasingly frequent in recent decades. However, the combined effects of MHWs and terrestrial drought on CO2 uptake in marginal seas are still unclear. The East China Sea (ECS) experienced an intense and long-lasting MHW accompanied by an extreme terrestrial drought in the Changjiang basin in the summer of 2022. In this study, we employed multi-source satellite remote sensing products to reveal the patterns, magnitude, and potential drivers of CO2 flux changes in the ECS resulting from the compounding MHW and terrestrial drought extremes. The CO2 uptake of the ECS reduced by 17.0% (1.06 Tg C) in the latter half of 2022 and the Changjiang River plume region shifted from a CO2 sink to a source (releasing 0.11 Tg C) in July-September. In the majority of the ECS, the positive sea surface temperature (SST) anomaly during the MHW diminished the solubility of CO2 in seawater, thereby reducing CO2 uptake. Moreover, the reduction in nutrient input associated with terrestrial drought, which is unfavorable to phytoplankton growth, further reduced the capacity of CO2 uptake. Meanwhile, the CO2 sink doubled for the offshore waters of the ECS continental shelf in July-September 2022, indicating the complexity and heterogeneity of the impacts of extreme climatic events in marginal seas. This study is of great significance in improving the estimation results of CO2 fluxes in marginal seas and understanding sea–air CO2 exchanges against the background of global climate change.

Low molecular weight carbohydrate patterns of mangrove macroalgae from different climatic niches under ocean acidification, warming and salinity variation

Ocean acidification has increased due to the enhanced solubility of CO2 in seawater. Mangrove macroalgae in tropical and subtropical coastal regions can benefit from the higher availability of CO2 for photosynthesis and primary production. However, they can be negatively affected by the simultaneously occurring warming and increased salinity in estuaries. Thus, we analyzed the isolated effects of ocean acidification and the interactive effects of increased temperature and salinity on the low molecular weight carbohydrate (LMWC) contents of the mangrove red macroalgae Bostrychia montagnei and Bostrychia calliptera from Brazilian tropical and subtropical populations. Specimens from both climatic niches were tolerant to pH decreased by CO2 enrichment and enhanced their LMWC contents under increased availability of CO2. Specimens from both climatic niches also accumulated their dulcitol and sorbitol contents to cope with warming and salt stress. Nevertheless, temperature of 34 °C was lethal for tropical macroalgae, while 29 °C and 31 °C were lethal for subtropical B. calliptera under salinity of 35. Tropical and subtropical B. montagnei synthesized dulcitol (5–110 mmol kg−1 dry weight) and sorbitol (5–100 mmol kg−1 dry weight) as osmoregulatory, energy and thermal protection compounds, whereas tropical and subtropical B. calliptera synthesized mainly dulcitol (10–210 mmol kg−1 dry weight). Although digeneaside has an energy function in Bostrychia spp., it is not an osmolyte or thermal protection compound. Our data demonstrated that both tropical and subtropical Bostrychia spp. benefit from ocean acidification by CO2 enrichment, increasing their LMWC contents. However, warming and increased salinity in estuaries will be detrimental to them, even they producing protective metabolites. Multifactorial approaches are recommended to investigate whether negative effects of increased temperature and salinity nullify positive effects of ocean acidification on these Bostrychia species/populations.

The ocean carbon pool: a vital component of the global carbon cycle

The global carbon cycle is an integral part of the Earth System. Of the land, atmosphere, and ocean components of the global carbon cycle that exchange carbon on the timescales of decades to centuries, the ocean contains more than 90% of carbon. The ocean carbon pool represents a critical component of the Earth's carbon cycle, playing a pivotal role in regulating atmospheric carbon dioxide (CO2) levels and influencing climate dynamics. The exponential increase of total anthropogenic CO2 emissions in the industrial era implies the ocean's uptake has increased exponentially, reaching 2.5 ± 0.6 Pg C yr-1 for 2009-2018. Without the ocean and land sinks, atmospheric CO2 levels would be close to 600 ppm. The ocean carbon pool comprises dissolved inorganic carbon (DIC), organic carbon, and particulate organic matter, collectively responsible for the sequestration and release of carbon into the atmosphere. Phytoplankton, the microscopic marine plants, play a fundamental role in the oceanic carbon cycle by photosynthesizing and fixing atmospheric CO2 into organic matter. This organic matter can be transferred to the deep ocean through the biological pump, further contributing to the storage of carbon in the form of sinking particles. The bulk of the global ocean margin represents a carbon sink of ~0.1-0.2 Pg C. Oceanic processes, such as ocean circulation and upwelling, help redistribute carbon from surface waters to the deep ocean. The solubility pump, which is driven by changes in temperature and salinity, also affects the solubility of CO2 in seawater. These natural processes work to mitigate the increase in atmospheric CO2 concentrations and help regulate global temperatures.

Spatiotemporal distributions of air-sea CO2 flux modulated by windseas in the Southern Indian Ocean

The Southern Indian Ocean is a major reservoir for rapid carbon exchange with the atmosphere, plays a key role in the world’s carbon cycle. To understand the importance of anthropogenic CO2 uptake in the Southern Indian Ocean, a variety of methods have been used to quantify the magnitude of the CO2 flux between air and sea. The basic approach is based on the bulk formula—the air-sea CO2 flux is commonly calculated by the difference in the CO2 partial pressure between the ocean and the atmosphere, the gas transfer velocity, the surface wind speed, and the CO2 solubility in seawater. However, relying solely on wind speed to measure the gas transfer velocity at the sea surface increases the uncertainty of CO2 flux estimation. Recent studies have shown that the generation and breaking of ocean waves also significantly affect the gas transfer process at the air-sea interface. In this study, we highlight the impact of windseas on the process of air-sea CO2 exchange and address its important role in CO2 uptake in the Southern Indian Ocean. We run the WAVEWATCH III model to simulate surface waves in this region over the period from January 1st 2002 to December 31st 2021. Then, we use the spectral partitioning method to isolate windseas and swells from total wave fields. Finally, we calculate the CO2 flux based on the new semiempirical equation for gas transfer velocity considering only windseas. We found that after considering windseas’ impact, the seasonal mean zonal flux (mmol/m2·d) increased approximately 10%-20% compared with that calculated solely on wind speed in all seasons. Evolution of air-sea net carbon flux (PgC) increased around 5.87%-32.12% in the latest 5 years with the most significant seasonal improvement appeared in summer. Long-term trend analysis also indicated that the CO2 absorption capacity of the whole Southern Indian Ocean gradually increased during the past 20 years. These findings extend the understanding of the roles of the Southern Indian Ocean in the global carbon cycle and are useful for making management policies associated with marine environmental protection and global climatic change mitigation.

Performance evaluation and environment risk assessment of steel slag enhancement for seawater to capture CO2

Major CO2 emitters are concentrated in coastal areas of China. The seawater with potential to capture CO2 was used as an absorbent and the addition of steel slag (SS) enhanced CO2 absorption by seawater. CO2 solubility in steel-slag-enhanced seawater was measured by an on-line chromatography apparatus, and the characterization analysis, thermodynamics, and kinetics were researched. CO2 solubility in seawater with a steel slag of 1.00 wt% increases by 64.27% relative to that in seawater, but is smaller than that in simulated-steel-slag-seawater (increasing by 29.86% relative to that in seawater with real steel slag). The results of XRD, TGA, IR and SEM-EDS show that Ca(OH)2 in the steel slag reacts with CO2 to form CaCO3. More quantity of CaO in simulated steel slag reacted with CO2 compared to real steel slag from XRF analysis. Increasing the concentration of steel slag and decreasing particle size of steel slag can also improve CO2 solubility and CO2 absorption rate. The steel slag and products after capturing CO2 are not hazardous waste and the steel slag can operate the solidification/stabilization of toxic metals. Steel slag can enhance CO2 absorption by seawater and perennially segregate CO2, providing CO2 capture and storage for coastal zones.

Henry's Law constant for CO2 in aqueous sodium chloride solutions at 1 atm and sub-zero (Celsius) temperatures

The solubility of CO2 in seawater is known to increase at colder temperatures, but few studies have examined the CO2 solubility in seawater and in sea-ice brines at sub-zero (Celsius) temperatures. The thermodynamic Henry's Law constant (KH) for CO2 in concentrated NaCl solutions was determined for the first time at sub-zero temperatures and salinities resembling those of the cryospheric seawater and sea-ice brine environments in polar and sub-polar oceans. The temperature (T, in Kelvin) dependence of the KH within the temperature and salinity ranges of this study (263 ≤ T ≤ 272 K and 35 ≤ S ≤ 152) is described by the following best-fit equation: ln KH = −2.484 + 2.775 × 10−2(274 − T) − 9.854 × 10−2/(274 − T) − 1.009 × 10−1 ln (274–T). The results show that the general practice, in geochemical and coupled climate‑carbon cycling models, of extrapolating KH values from above-zero to sub-zero temperatures underestimates the solubility of CO2 by up to 19%.

Study of CO2 capture by seawater and its reinforcement

Numerous coal-fired power plants, cement plants and steel mills are concentrated in coastal areas of China, and are three major CO2 emitters. Seawater may be a potential resource to capture CO2 in coastal areas. In this study, we used seawater as a CO2 absorbent to capture CO2. An online chromatography apparatus was used to determine CO2 solubility in seawater with different temperatures, pressures and salinities. Then, the thermodynamics and kinetics were studied for the influences of temperature and salinity on CO2 capture in seawater. The experimental results show that increasing temperature and salinity were adverse to CO2 capture by seawater because of an increase in Henry's constant from a thermodynamics aspect. The kinetic results show that high temperature and low salinity can increase the CO2 absorption rate. In order to improve the CO2 absorption ability of seawater and promote CO2 fixation in carbonate precipitation, we added CaO as major components of industrial alkaline substances to enhance the seawater absorption of CO2. CO2 solubility in seawater with 0.4% CaO increased by 79.25%. It shows that the addition of CaO can enhance greatly seawater capture of CO2. The seawater and its reinforcement with CaO is a potential method to capture CO2.

Study of CO<sub>2</sub> Solubility in Brine under Different Temperatures and Pressures

The solubility of CO2 in water and aqueous solutions of NaCl, KCl, CaCl2, NaCl+KCl (weight ratio= 1:1), NaCl+CaCl2 (weight ratio= 1:1), KCl+CaCl2 (weight ratio= 1:1) and NaCl+KCl+CaCl2 (weight ratio= 1:1:1) was determined experimentally at 35, 45 and 55°C up to 16 MPa and the concentration of the salt was up to 14.3 wt% while in simulation the salt ions of Na+, K+, Ca2+, and Cl- was determined at wide temperature-pressure-ionic strength range (273 to 533 K, from 0 to 2000 bar, and from 0 to 4.5 molality of salts). Based on experiment data, the solubility increased with increase in pressure but decreased with increasing the temperature and salt concentration. Meanwhile, the model also predicted the CO2 solubility in seawater at two phase coexistence (vapour-liquid or liquid-vapor) and at three-phase coexistence (CO2 hydrate-liquid water-vapor CO2).

Unraveling dynamical controls on the North Pacific carbon sink

A broad swath across the North Pacific basin uptakes a disproportionately large amount of atmospheric CO2every year, with the region of most intense uptake located in the North Pacific transition zone, from ∼30°N to 40°N–45°N. Though a net carbon sink on a mean annual basis, the region varies seasonally between a strong sink in winter and a neutral to weak source in summer. Herein we use observational carbon data to investigate processes regulating air‐sea CO2 flux in this region on seasonal and annual timescales by quantifying the impacts of temperature, biology, and physics on seawater pCO2. Temperature effects dominate the pCO2 signal seasonally, yet support only a portion of the annual CO2 uptake in the region, via their impact on the solubility of CO2 in seawater. Instead, processes removing carbon from surface waters dominantly support the region's uptake of CO2 on annual timescales: the vertical export of organic carbon to depth, and the geostrophic advection of dissolved inorganic carbon laterally out of the region. We find the location of this carbon sink region, traditionally attributed to a combination of biological and temperature effects, to instead be driven by the steady geostrophic divergence of DIC at these latitudes.

Transport Process of Carbon Dioxide in Seawater and Synthetic Seawater

Carbon dioxide (CO2) ocean sequestration technologies, such as dissolution into seawater, are important to mitigate global warming. In this study, solution processes of CO2 gas in seawater and synthetic seawater were experimentally and theoretically studied under various pressures and temperatures to evaluate the transport process of CO2 in seawater. The solubilities of CO2 in seawater and synthetic seawater were measured by a change in pressure due to absorption at temperatures ranged from 277 K to 333 K near atmospheric pressures, and ranged from 277 K to 298 K at pressures of 1 MPa, 2 MPa, and 3 MPa. It was obtained that the solubilities of CO2 increase with an increase in pressure, but decrease with an increase in temperature. The solubility of CO2 in synthetic seawater decreases with an increase in salt concentration. An empirical correlation for solubility of CO2 in seawater at various temperatures and pressures was obtained based on the experimental data. In the theoretical analysis for the solution of single CO2 bubble in seawater, the single CO2 bubble was assumed to be stationary and surrounded by infinite liquid seawater. The rate of solution of bubble in liquid is affected strongly by various parameters, such as solubility, diffusion coefficient, bubble radius, and temperature.

Rate of Increasing Concentrations of Atmospheric Carbon Dioxide Controlled by Natural Temperature Variations

Studies of the temperature anomalies during the last 27 years show a close relationship with the varying increase of CO2 in the atmosphere. Volcanic eruptions and La Niñas reduce CO2 values and El Niños increase them. This close relationship strongly indicates that ocean temperatures and the solubility of CO2 in seawater control the amount of CO2 being absorbed or released by the oceans. It is therefore likely that the increased CO2 concentration in the atmosphere is due to a natural global warming and that CO2 produced through fossil fuel combustion by humans can not disrupt this balance. An advanced statistical multiregression analysis confirms this conclusion. Therefore it is likely that there is no anthropogenic climate change on a global scale. The natural exchange of CO2 between ocean, biomass on land and the atmosphere is very large. In only four to five years all the CO2 in the atmosphere has been recycled through the oceans and the biomass system. The annual anthropogenic human production of CO2 is neutralized by nature in as little as 12 days. Recent studies of the solar forcing, changes in cosmic radiation and its role in cloud formations explain the global warming that has taken place since 1910.

Effect of Carbon Dioxide in Seawater on Desalination: A Comprehensive Review

The two main methods of removing salt from ocean water currently in use for large scale applications are: distillation using thermal desalination and membrane reverse osmosis separation. A detailed knowledge of the CO2 solubility in the seawater at the conditions prevailing in the system is required for the modeling of CO2 release in the multi‐stage flash distillers. The measurement of the solubility of CO2 in pure water has been extensively studied in the literature, whereas there is a lack of saline solutions studies. Several studies have investigated the solubility of CO2 in seawater under different temperatures and pressures without covering the conditions that prevailed in the desalination plants for example low pressures and high temperatures. The gas solubility can be theoretically estimated by considering the ionic strength and the salting‐out parameter in the low‐pressure regime, i.e., near atmospheric pressure. The measurements of gas solubility can be made as a function of the seawater temperature and salinity at low pressure where effect of pressure can be considered negligible. Alkaline scale formation causes fouling in the MSF plants and it is known that the rate of formation of calcium carbonate and magnesium hydroxide in seawater depends on a number of parameters such as temperature, pH, concentration of bicarbonate ions, rate of CO2 release, concentration of Ca2+ and Mg2+ ions, and total dissolved solids. This review shows an overview of the carbon dioxide solubility in the high concentrated saline water, carbonate equilibriums in the seawater and the various correlations used to characterize the CO2‐seawater system.

Study of Solution Process of Carbon Dioxide in Seawater

Carbon dioxide (CO2) ocean sequestration technologies, such as dissolution into seawater, are important to mitigate global warming. In this study, solution processes of CO2 gas in seawater and pure water were experimentally studied under various pressures and temperatures to evaluate the solubilities of CO2 in seawater. The solubilities of CO2 in seawater and pure water were measured by a change in pressure due to absorption at pressures up to 30 MPa and the temperatures ranged from 4°C to 60°C. It was obtained that the solubilities of CO2 were between 0.27 × 10-3 and 1.26 × 10-3 in seawater, and between 0.26 × 10-3 and 0.6 × 10-3 in pure water near atmospheric pressure. The values increase with an increase in pressure, but decrease with an increase in temperature. The Henry's law constant of CO2 was about 105 MPa at a temperature of 4°C in seawater under atmospheric pressure, and increased with an increase in temperature. The solubility of CO2 in seawater was lower than that in pure water. Empirical correlations for solubilities of C02 in seawater and pure water at various temperatures under atmospheric pressure were obtained based on the experimental data.

Poring over the Past

The concentration of CO2 in the atmosphere is understood to be a primary controller of climate, and high values are thought to be the main cause of a number of extended warm periods over the geological history of Earth. Additionally, atmospheric CO2 exerts a fundamental influence on the carbonate chemistry of the ocean, due to the solubility of CO2 in seawater, and therefore on calcifying marine organisms. A direct record of atmospheric CO2 concentration is available for less than the past 1 million years, so earlier periods must be studied by modeling or via proxies.

Role of deep sea temperature in the carbon cycle during the last glacial

To characterize the response of Earth's climate system to increases in atmospheric CO2, climate modelers define climate sensitivity as the change in global mean temperature in response to prescribed forcing. Here we turn this approach around and use estimates of ocean temperature change to investigate the mechanisms driving CO2 variations over the last glacial. New records provide evidence of a link between deep ocean temperature and atmospheric CO2 over the last glacial cycle. Two mechanisms simultaneously couple pCO2 and deep ocean temperature: the temperature‐dependent solubility of CO2 in seawater and the atmospheric CO2‐dependent radiative forcing of temperature. Each of these forcing mechanisms leaves a unique slope of covariation between CO2 and deep ocean temperature, which we estimate using numerical models of climate and the carbon cycle. The pCO2/T slopes derived from paleoclimate data differ between the deglaciation and shorter 5‐kyr duration events in marine isotope stage 3 (MIS 3), revealing different mechanisms driving atmospheric CO2 variability. The amplitude of changes over the deglaciation coincides with estimates for CO2 forcing of temperature; however, CO2 changes during MIS 3 can be explained solely by temperature‐dependent solubility driving variations in atmospheric pCO2. The deep water temperature changes during MIS 3 may reflect changes in the temperature or relative contribution of Antarctic Bottom Water and play a role in the “bipolar seesaw.”