Pressure Of CO2 In Water Research Articles

Drivers of inorganic carbon dynamics and air–water CO2 fluxes in two large tropical estuaries: Insights from coupled radon (222Rn) and pCO2 surveys

AbstractEstuaries and coastal waters are generally significant emitters of CO2 to the atmosphere. Globally, submarine groundwater discharge (SGD) is a significant driver of inorganic carbon dynamics and the partial pressure of CO2 in water [pCO2(water)] in estuaries and coastal waters. However, there are few studies of CO2 emission and SGD in large tropical estuaries. To investigate the drivers of pCO2(water) dynamics in two large tropical estuaries in India, the Hooghly and Matla estuaries, we conducted coupled radon and pCO2(water) surveys of groundwater and surface waters. We also collected high‐temporal‐resolution (1 min) data of related biogeochemical parameters. Using radon‐222 (222Rn) as a proxy for SGD, we found significant regulation of pCO2(water) by SGD in both studied estuaries. This observation can be considered direct evidence of the influence of SGD on pCO2(water) and consequent air–water CO2 fluxes in these two previously poorly studied estuaries. Our finding that total alkalinity (TAlk) and dissolved inorganic carbon (DIC) were also significantly higher in the groundwater than in the estuarine surface waters also supports a substantial contribution of SGD to the inorganic carbon dynamics of these estuaries. However, high groundwater TAlk to DIC ratios (> 1) indicate that SGD also enhances the carbonate buffering capacity in these estuaries. By contributing to an improved understanding of the role of SGD in inorganic carbon cycling in tropical estuaries and coastal oceans, this study will contribute to efforts to upscale regional‐scale coastal carbon budgets to a global scale.

Low CO2 evasion rate from the mangrove-surrounding waters of the Sundarbans

Globally, water bodies adjacent to mangroves are considered significant sources of atmospheric CO2. We directly measured the partial pressure of CO2 in water [pCO2(water)] and related biogeochemical parameters with high temporal resolution, covering both diel and tidal cycles, in the mangrove-surrounding waters around the northern Bay of Bengal during the post-monsoon season. Mean pCO2(water) was marginally oversaturated in two creeks (470 ± 162 µatm, mean ± SD) and undersaturated in the adjoining estuarine stations (387 ± 58 µatm) compared to atmospheric pCO2, and was considerably lower than the global average. We further estimated the pCO2(water) and buffering capacity of all possible sources of the mangrove-surrounding waters and concluded that their character as a CO2 sink or weak source is due to the predominance of marine water from the Bay of Bengal with low pCO2 and high buffering capacity. Marine water with high buffering capacity suppresses the effect of pCO2 increase within the mangrove system and lowers the CO2 evasion even in creek stations. The δ13C of dissolved inorganic carbon (DIC) in the mangrove-surrounding waters indicated that the DIC sources were a mixture of mangrove plants, pore-water, and groundwater, in addition to marine water. Finally, we showed that the CO2 evasion rate from the estuaries of the Sundarbans is much lower than the recently estimated world average. Our results demonstrate that mangrove areas having such low emissions should be considered when up-scaling the global mangrove carbon budget from regional observations.

Lateral carbon fluxes and CO2 evasion from a subtropical mangrove-seagrass-coral continuum

Mangrove, seagrass, and coral habitats often lie adjacent to each other in the tropics and subtropics. Lateral carbon fluxes and their consecutive effects on CO2 dynamics and air–water fluxes along the ecosystem continuum are often overlooked. We measured the partial pressure of CO2 in water and associated biogeochemical parameters with a high temporal resolution and estimated air–water CO2 fluxes along the ecosystem continuum. Their lateral fluxes were estimated by using a biogeochemical mass-balance model. The results showed that the waters surrounding mangrove, seagrass, and coral habitats acted as a strong, moderate, and weak source of atmospheric CO2, respectively. The mangrove zone acted as a net source for TAlk, DIC, and DOC, but as a net sink for POC. The contribution of riverine and mangrove-derived OM was substantially high in mangrove sediment, indicating that net transport of POC towards the coastal sea was suppressed by the sediment trapping function of mangroves. The seagrass zone acted as a net source of all carbon forms and TAlk, whereas the coral zone acted as a net sink of TAlk, DIC, and DOC. The lateral transport of carbon from mangroves and rivers offset atmospheric CO2 uptake in the seagrass zone. DOC degradation might increase DIC, and other biogeochemical processes facilitate the functioning of the coral zone as a DOC sink. However, as a result of DIC uptake by autotrophs, mainly in the coral zone, the whole ecosystem continuum was a net sink of DIC and atmospheric CO2 evasion was lowered. We conclude that lateral transport of riverine and mangrove-derived DIC, TAlk, and DOC affect CO2 dynamics and air–water fluxes in seagrass and coral ecosystems. Thus, studies of lateral carbon fluxes at local and regional scales can improve global carbon budget estimates.

Insights from year-long measurements of air–water CH<sub>4</sub> and CO<sub>2</sub> exchange in a coastal environment

Abstract. Air–water CH4 and CO2 fluxes were directly measured using the eddy covariance technique at the Penlee Point Atmospheric Observatory on the southwest coast of the United Kingdom from September 2015 to August 2016. The high-frequency, year-long measurements provide unprecedented detail on the variability of these greenhouse gas fluxes from seasonal to diurnal and to semi-diurnal (tidal) timescales. Depending on the wind sector, fluxes measured at this site are indicative of air–water exchange in coastal seas as well as in an outer estuary. For the open-water sector when winds were off the Atlantic Ocean, CH4 flux was almost always positive (annual mean of ∼0.05 mmol m−2 d−1) except in December and January, when CH4 flux was near zero. At times of high rainfall and river flow rate, CH4 emission from the estuarine-influenced Plymouth Sound sector was several times higher than emission from the open-water sector. The implied CH4 saturation (derived from the measured fluxes and a wind-speed-dependent gas transfer velocity parameterization) of over 1000 % in the Plymouth Sound is within range of in situ dissolved CH4 measurements near the mouth of the river Tamar. CO2 flux from the open-water sector was generally from sea to air in autumn and winter and from air to sea in late spring and summer, with an annual mean flux of near zero. A diurnal signal in CO2 flux and implied partial pressure of CO2 in water (pCO2) are clearly observed for the Plymouth Sound sector and also evident for the open-water sector during biologically productive periods. These observations suggest that coastal CO2 efflux may be underestimated if sampling strategies are limited to daytime only. Combining the flux data with seawater pCO2 measurements made in situ within the flux footprint allows us to estimate the CO2 transfer velocity. The gas transfer velocity and wind speed relationship at this coastal location agrees reasonably well with previous open-water parameterizations in the mean but demonstrates considerable variability. We discuss the influences of biological productivity, bottom-driven turbulence and rainfall on coastal air–water gas exchange.

Characterizing nutrient dynamics with relation to changes in partial pressure of CO2 in a tropical sewage‐fed aquaculture pond situated in a Ramsar wetland

AbstractThe changes in nutrient dynamics (nitrate, ammonium, silicate, phosphate and iron concentration) vis‐à‐vis partial pressure of CO2 in water [pCO2(water)] from tropical sewage‐fed aquaculture ponds (East Kolkota Wetlands, India) were analysed by means of a microcosm. A significant relationship between these nutrient’s removal from the system and reduction in pCO2(water) was observed (with few exceptions). These water bodies acted as significant sources of CO2 in pre‐monsoon and monsoon seasons despite having substantial quantity of chlorophyll‐a to make it a net autotrophic system. The study revealed that if conditions favourable for optimum photosynthesis can be maintained in these ponds, the CO2 source character of these ponds can be reversed. In the post‐monsoon season, when the pH of the water column was high, the system acted as sink for CO2 which suggests the use of lime to prevent these systems from becoming hypereutrophic and carbon source at the same time.

CO2 fluxes from aquaculture ponds of a tropical wetland: Potential of multiple lime treatment in reduction of CO2 emission

Partial pressure of CO2 in water [pCO2(water)] and air-water CO2 flux were estimated in two aquaculture ponds (one received no lime treatment (NTP) and in the other lime treatment was performed (LTP) four times a year) every month throughout an annual cycle, situated in East Kolkata Wetlands, a Ramsar Site in eastern India. It was hypothesized that lime treatment can potentially lower the pCO2(water) in aquaculture ponds and hence make these aquatic bodies sinks for CO2. The results portrayed that NTP acted as a source of CO2 throughout the year (annual mean: 1929 ± 1397 μmol m−2 h−1), whereas, LTP acted as CO2 sinks post lime addition (monthly mean ranged from −366 ± 16 to −449 ± 32 μmol m−2 h−1), though the effect of lime addition was found to diminish by the next month and it acted as source for CO2 in the months when no lime treatment was done (LTP annual mean: 1010 ± 1617 μmol m−2 h−1). Lime treatment increased the pH level and reduced the turbidity which facilitated optimum photosynthesis and the productivity increased rapidly. Beyond the critical pH value of 8.9–9.0, the pCO2(water) values became under-saturated with respect to atmospheric CO2 concentration. The effect of lime treatment was not found to prevail in the following months as a steady source of sewage from the Kolkata metropolis which feeds these aquaculture constantly bring in a huge carbon source both in inorganic and organic form. As soon as the flocculation effect of the lime dies off, the water column starts becoming turbid again which aids in converting the system into a net heterotrophic one from a net autotrophic. Based on the results we could successfully accept our hypothesis that lime treatment can not only reduce the CO2 emission but also make the system a CO2 sink.

Ảnh hưởng của nồng độ CO2 cao trong nước lên cân bằng acid và base của lươn đồng, Monopterus albus (Zuiew, 1973)

The study was conducted to investigate the variability of parameter in water with different stages as well as to determine the effect of high CO2 on the acid-base regulation of the eel. The field survey was measuring CO2 levels in 9 swamp eel grow-out tanks. The results showed that the partials pressure of CO2 in water was 9.5 mmHg and 28 mmHg in the middle and harvest of culture cycle (9 months), respectively. The laboratory experiment was conducted with 3 treatments including control, 14 and 30 mmHg CO2. Blood was sampled at 0, 3, 6, 24, 48, and 72-h. Blood pH decreased during the first 24-h and completely recovered after 72-h with value of 7.4±0.04 at the treatment of 14 mmHg CO2. In contrast, partial pressure of CO2 in the blood and plasma HCO3- increased significantly at the treatments of 14 and 30 mmHg CO2 during hypercapnic exposure compared to the control group (p

Physical and biogeochemical mechanisms of internal carbon cycling in Lake Michigan

AbstractThe lakewide seasonal carbon cycle of Lake Michigan is poorly quantified and lacks the mechanistic links necessary to determine impacts upon it from eutrophication, invasive species, and climate change. A first step toward a full appreciation of Lake Michigan's carbon cycle is to quantify the dominant mechanisms of its internal carbon cycle. To achieve this, we use the MIT general circulation model configured to the bathymetry of Lake Michigan and coupled to an ecosystem model to simulate the seasonal cycle of productivity, temperature, circulation, and the partial pressure of CO2 in water (pCO2). This biogeochemistry is designed to be appropriate for the prequagga mussel state of the lake. The primary mechanism behind the seasonal cycle of primary productivity is lake physics. The offshore spring phytoplankton bloom begins following a reduction in deep vertical mixing and ends with the depletion of nutrients via thermal stratification. The exception is the western shoreline, where summer winds drive coastal upwelling, providing hypolimnetic nutrients and generating significant productivity. Surface pCO2 is controlled by the net effect from temperature on solubility, and is modulated by biological uptake of dissolved inorganic carbon (DIC) and isothermal mixing of DIC‐rich water in winter. Temperature tends to have the greatest seasonal impact in nearshore regions, while local DIC has the greatest impact in offshore regions. Lakewide, the model suggests that carbon is absorbed from the atmosphere during the spring bloom and released to the atmosphere during winter mixing and when summer surface temperatures are at their maximum.

Influence of the organization of water-in-ionic liquid microemulsions on the size of silver particles during photoreduction

Metal particles of silver (Ag) have been synthesized by the photoreduction of silver nitrate (AgNO3) in water-in-ionic liquid (IL) microemulsions consisting of nonionic surfactant Tween 20 or Triton X-100, water and ionic liquid, 1-octyl-3-methylimidazolium hexafluorophosphate ([OMIm][PF6]). The formation of microemulsions as well as Ag particles produced by the photoreduction has been investigated by UV–vis, cryo-TEM, small-angle X-ray scattering (SAXS), and extended X-ray absorption fine structure (EXAFS) measurements. At the early stage of Ag particle formation under ambient pressure, the size of Ag particles in water/[OMIm][PF6]/TX-100 microemulsions was slightly larger than that in water/[OMIm][PF6]/Tween20 microemulsions. With an increase in photoirradiation time beyond 30min, precipitation of larger Ag aggregates occurred. In contrast to the preparation under ambient pressure, the growth of Ag particles and aggregates was suppressed in preparing under high pressure (25MPa) of CO2, leading to no precipitation of Ag aggregates. The average diameters of the finally-obtained metallic Ag particles prepared under high pressure of CO2 in water/[OMIm][PF6]/Tween20 and water/[OMIm][PF6]/TX-100 microemulsions were estimated from cryo-TEM to be 3.7nm and 2.8nm, respectively. By using Guinier plots at q (<0.16nm−1), it was demonstrated that the diameter of the water droplets during Ag particle formation under high pressure of CO2 remained unchanged in the range of 33–37nm due to their higher stability compared to water droplets, whereas under ambient pressure the diameter drastically increases from 28nm to 40nm during the first 60min of photoirradiation, resulting in the precipitation of larger Ag aggregates, especially in the case of water/[OMIm][PF6]/Tween20 microemulsions.

Coral calcification under increasing atmospheric CO2 concentration and global warming in the southern South China Sea

Mangrove, seagrass, and coral habitats often lie adjacent to each other in the tropics and subtropics. Lateral carbon fluxes and their consecutive effects on CO2 dynamics and air–water fluxes along the ecosystem continuum are often overlooked. We measured the partial pressure of CO2 in water and associated biogeochemical parameters with a high temporal resolution and estimated air–water CO2 fluxes along the ecosystem continuum. Their lateral fluxes were estimated by using a biogeochemical mass-balance model. The results showed that the waters surrounding mangrove, seagrass, and coral habitats acted as a strong, moderate, and weak source of atmospheric CO2, respectively. The mangrove zone acted as a net source for TAlk, DIC, and DOC, but as a net sink for POC. The contribution of riverine and mangrove-derived OM was substantially high in mangrove sediment, indicating that net transport of POC towards the coastal sea was suppressed by the sediment trapping function of mangroves. The seagrass zone acted as a net source of all carbon forms and TAlk, whereas the coral zone acted as a net sink of TAlk, DIC, and DOC. The lateral transport of carbon from mangroves and rivers offset atmospheric CO2 uptake in the seagrass zone. DOC degradation might increase DIC, and other biogeochemical processes facilitate the functioning of the coral zone as a DOC sink. However, as a result of DIC uptake by autotrophs, mainly in the coral zone, the whole ecosystem continuum was a net sink of DIC and atmospheric CO2 evasion was lowered. We conclude that lateral transport of riverine and mangrove-derived DIC, TAlk, and DOC affect CO2 dynamics and air–water fluxes in seagrass and coral ecosystems. Thus, studies of lateral carbon fluxes at local and regional scales can improve global carbon budget estimates.

Propranolol Impairs the Hyperventilatory Response to Acute Hypercapnia in Rainbow Trout

ABSTRACT This study investigated the possible role of catecholamines in the ventilatory response of rainbow trout (Oncorhynchus mykiss) to acute external hypercapnia. The ventilatory response to hypercapnia [partial pressure of CO2 in water of fish pre-treated with the selective β-adrenoceptor antagonist, D,L-propranolol, was compared with that of D-propranolol (an isomer with minimal β-antagonistic activity) and saline pre-treated fish (sham). A sustained 3.6-fold increase in gill ventilation volume was observed in the sham and D-propranolol-treated groups during the 30min interval of hypercapnia. Fish pre-treated with D,L-propranolol displayed a blunted hyperventilatory response to hypercapnia (1.9-fold increase at 30min). These results indicate that the β-component of an adrenergic response is involved in the usual hyperventilatory response to external hypercapnia. It is suggested that the impaired hyperventilatory response of the D,L-propranolol-treated group reflects an inhibition of central adrenergic mechanism(s) involved in the hyperventilatory reflex to respiratory acidosis.