Low Concentrations Of Carbon Dioxide Research Articles

FTIR measurements of acid‐gas–methyldiethanolamine systems

AbstractThe standard industrial process for the purification of natural gas is to remove acid gases, mainly hydrogen sulfide and carbon dioxide, by the absorption and reaction of these gases with alkanolamines, but the lack of reliable and accurate vapor–liquid equilibrium (VLB) data impedes the commercial application of more efficient alkanolamine systems. A novel Fourier‐transform infrared (FTIR) technique was developed to make in‐situ VLE measurements of acid‐gas‐aqueous alkanolamine systems and to improve the accuracy of VLE measurements at low hydrogen sulfide and carbon dioxide concentrations. VLE measurements of low carbon dioxide and hydrogen sulfide concentrations in aqueous mixtures of methyldiethanolamine (MDEA) are reported using the new FTIR technique.

Complete recovery after near-fatal venous air embolism during cesarean section

During replacement to the abdomen of the exteriorized uterus at cesarean section under epidural block, a previously healthy woman developed cardiorespiratory arrest. Tracheal intubation revealed low endtidal carbon dioxide concentration suggesting embolization. Resuscitative efforts were successful. Uterine exteriorization — as well as the Trendelenburg position - significantly increase the risk of air embolization so that routine use of appropriate monitors is indicated to facilitate early diagnosis.

Assessment of Several Test Methods for the Determination of the Anaerobic Biodegradability of Polymers

Anaerobic degradation of eight commercially available biodegradable polymers was compared in two anaerobic tests using digestion sludge, according to ISO 11734 and ASTM D.5210-91. Cotton, polyhydroxybutyrate/hydroxyvalerate copolymer (PHB/PHV), starch blend, thermoplastic cellulose acetate, and cellulose acetate fibers proved to be anaerobically degradable, but only a low extent of degradation was found for polylactide, polyvinylalcohol, and polycaprolactone. Both test methods gave the same overall results, but with the ISO medium, longer lag phases and greater ranges of variation in the results were observed. These effects are presumably due to low concentrations of carbon dioxide in the ISO medium. Carbon dioxide has been demonstrated to be essential for the growth of various anaerobic bacteria, notably homoacetogenic and methanogenic bacteria.

FTIR method for VLE measurements of acid‐gas–alkanolamine systems

AbstractThe standard industrial process for the purification of natural gas is to remove acid gases, mainly hydrogen sulfide and carbon dioxide, by the absorption and reaction of these gases with alkanolamines, but the lack of reliable and accurate vapor‐liquid equilibrium (VLE) data impedes the commercial application of more efficient alkanolamine systems. The objective of this research was to develop an FTIR apparatus and an in‐situ technique capable of making VLE measurements of acid‐gas–aqueous alkanolamine systems and to improve the accuracy of vapor–liquid equilibrium measurements at low hydrogen sulfide and carbon dioxide concentrations. The new FTIR apparatus and technique were tested in VLE measurements of low concentrations of carbon dioxide and hydrogen sulfide in aqueous mixtures of diethanolamine.

Oxygen uptake in coprophilous beetles (Aphodius, Geotrupes, Sphaeridium) at low oxygen and high carbon dioxide concentrations

Abstract. The rate of O2 consumption was measured in five coprophilous beetle species (common in Denmark) at O2 concentrations from 1–21%. With the exception of the mainly soil‐living Geotrupes spiniger (Marsham) (Geotrupidae), these beetles are probably exposed to severe hypoxia in fresh cattle pats. Aphodius fossor (Linnaeus), A. contaminatus (Herbst) (Aphodiidae) and Sphaeridium lunatum Fabricius (Hydrophilidae) maintained normal movements and a normal rate of 02 uptake (for at least 30 min) at only 1% O2. There is no evidence, therefore, that the beetles switch to anaerobic metabolism under these conditions. This ability to regulate respiration, and hence to extract 02 at very low concentrations, is exceptional even among terrestrial arthropods living in soil or other potentially hypoxic substrates. In A. rufipes (Linnaeus), respiration declined at ambient concentrations below 2% O2, and in G. spiniger the ability to regulate respiration seemed to fail at even higher concentrations. In four of the species (G. spiniger was not tested), about 11% CO2 (the level in a dung pat at 2% O2) did not affect the O2 uptake at 2% O2.

Hepatic lipidosis in anorectic, lactating holstein cattle: a retrospective study of serum biochemical abnormalities.

The association between hepatic lipidosis (HL) and disease in 59 anorectic, ketotic, lactating Holstein heifers and cows was investigated. Severe HL, as determined by histologic evaluation of liver tissue, was present in 46 animals; only half of these animals required intensive treatment for ketosis, and only half had serum biochemical evidence of liver disease, as determined by the presence of a last value of 2-fold or greater than the upper limit of the reference ranges for at least 2 of the 4 serum tests: gamma-glutamyl transferase, aspartate aminotransferase, and sorbitol dehydrogenase activities and bile acid concentrations. Most cattle with biochemical evidence of liver disease and severe HL had been lactating for 14 or more days. Cows that required intensive treatment inconsistently had serum biochemical evidence of liver disease. Although cattle with severe HL had significantly higher serum bilirubin concentrations and aspartate aminotransferase and sorbitol dehydrogenase activities than cattle with less severe lipidosis, the specificity of abnormally high serum sorbitol dehydrogenase activity or bilirubin concentration for severe lipidosis was only 8%. Abnormally high serum aspartate aminotransferase activity was 83% sensitive and 62% specific for severe lipidosis. Serum glucose and total carbon dioxide concentrations were significantly lower in cattle with severe lipidosis than in those with mild or moderate lipidosis, and low serum glucose or total carbon dioxide concentrations were rare in cattle without severe lipidosis. From these data, we conclude that the use of a single biochemical or histopathologic criterion to define severity of disease or degree of liver compromise in anorectic, ketotic cows results in the misidentification of many animals.

Variation in growth stimulation by elevated carbon dioxide in seedlings of some C3 crop and weed species

Seven C3 crop and three C3 weed species were grown from seed at 360 and at 700 cm3 m–3 carbon dioxide concentrations in a controlled environment chamber to compare dry mass, relative growth rate (RGR), net assimilation rate (NAR), leaf area ratio (LAR) and photosynthetic acclimation at ambient and elevated carbon dioxide. The dry mass at the final harvest at elevated carbon dioxide relative to that at ambient carbon dioxide was highly correlated with the RGR at the lower carbon dioxide concentration. This relationship could be quite common, because it does not require that species differ in the response of RGR or photosynthesis to elevated carbon dioxide, and holds even when species differ moderately in these responses. RGR was also measured for a limited period at the end of the experiment to determine relationships with leaf gas exchange measured at this time. Relative increases in RGR at elevated carbon dioxide at this time were more highly correlated with the relative increase in NAR at elevated carbon dioxide than with the response of LAR. The amount of acclimation of photosynthesis was a good predictor of the relative increase in NAR at elevated carbon dioxide, and the long‐term increase in photosynthesis in the growth environment. No differences between crops and weeds or between cool and warm climate species were found in the responses of growth or photosynthetic acclimation to elevated carbon dioxide.

The origin of unusual gas seeps from onshore Papua New Guinea

In September 1989, gas seepage samples and associated oils and waters were collected from onshore in the Aure Thrust Belt of Papua New Guinea and analysed to characterise the petroleum sourcing system in the basin. The oil samples are extensively biodegraded as is typical of seeps. They are derived from a dominantly marine source, although in some samples there is evidence of higher land plant input. The thermal maturity of the samples is variable, from low to moderately high. Some of the gas samples are clearly biogenic, some are thermogenic and some contain a mixture of both source types. δD analysis on selected samples helped identify two biogenic groups which are characterised by: (a) high carbon dioxide content and light δD, and (b) lower carbon dioxide content and heavier δD. These characteristics reflect the microbial pathway of biogenic methane production: the first group is predominantly a product of acetate fermentation and is associated with low salinity samples (recent meteoric water); the second group is a product of CO 2 reduction and is associated with higher salinity water samples. The δD values for the second group are characteristic of biogenic gas produced in marine environments although the salinity of the associated waters has a halite dissolution character rather than that of mixing with sea water. The unique character of these gases suggests the presence of biogenic accumulations in the subsurface. The thermogenic gases are associated with water samples of intermediate salinity and demonstrate exceptionally heavy δ 13C for the carbon dioxide component (up to +28%. PDB).

The Use of Microelectrodes to Study the Precipitation of Calcite upon Algal Biofilms

Calcium and pH ion-selective microelectrodes are used for the first time to measure chemical activity profiles above laboratory-grown algal biofilms (green alga,Chlorococcumsp). The results are used to calculate the solution composition changes above an actively photosynthesizing biofilm. These changes include the total calcium concentration, degree of supersaturation of the solution with respect to calcite, and the partial pressure of carbon dioxide. Measurements are made in a flow-cell, which was designed to hold the templates on which the biofilms are grown. Measurements show pronounced gradients of pH and calcium concentration, within a distance of approximately 500 μm above the biofilm. The high degree of supersaturation caused by the low concentrations of carbon dioxide near the biofilm surface leads to the precipitation of calcite on the biofilm. SEM micrographs illustrate the close association of calcite crystals with the algal cells. Preliminary results are presented of the precipitation rates estimated from the diffusion flux of calcium at the biofilm surface. The results are in broad agreement with the rates expected from calcite seed growth experiments in similar solution conditions.

Characteristics of the large-scale circulation during episodes with high and low concentrations of carbon dioxide and air pollutants at an arctic monitoring site in winter

The impact of large-scale atmospheric flow systems on the time variation of atmospheric carbon dioxide and aerosols at an Arctic monitoring site has been studied for winter seasons. Episodes with high and low concentrations of atmospheric carbon dioxide and aerosols were identified. Synoptic 500 hPa geopotential height maps and sea-level pressure maps were used to study the large-scale circulation. We found that polluted air, that is elevated in aerosol concentrations and carbon dioxide, arrived from northwestern Russia, whereas nonpolluted air and air with low concentrations of carbon dioxide arrived from the Norwegian Sea during winter. Part of the study was devoted to an investigation of the impact of atmospheric blocking and planetary-scale waves on episodes with high and low concentrations of atmospheric carbon dioxide and aerosols at the monitoring site. Unlike other similar studies we found that atmospheric blockings do not have a large impact on these episodes, unless the blocking is located east of 40°E. Such blockings are not as frequent as those over eastern Atlantic and western Europe. However, they are prerequisites for episodes with high concentrations of atmospheric carbon dioxide and air pollutants. We also found that the planetary-scale waves do not contribute much to episodes with high concentrations of carbon dioxide and air pollutants. The result obtained in the first part of the study, viz. that polluted air and air with high concentrations of atmospheric carbon dioxide arrive from northwestern Russia, whereas nonpolluted air and air with low concentrations of carbon dioxide arrive from the Norwegian Sea, was tested by using different data (particulate sulfur in the air) and using a different method of identifying episodes with high and low concentrations. The test showed that the results were essentially the same. We conclude that the wind direction in the lower troposphere is the parameter that has the largest impact on concentrations of atmospheric carbon dioxide and air pollutants at Spitsbergen in winter.

Volumetric Properties of Pentane + Carbon Dioxide at High Pressures

The volumetric behavior of carbon dioxide + pentane has been investigated at 323, 348, 373, 398, and 423 K at pressures up to 70 MPa using a variable-volume view cell. Densities for pure components and fluid mixtures containing 10, 20, 35, 50, 62, 72, 80, and 88% by weight carbon dioxide are presented as a function of pressure at each temperature. With increasing pressure (above 20 MPa) the density of carbon dioxide becomes greater than that of pentane, and mixture densities show a crossover with composition. At a given temperature and pressure, under a majority of the conditions evaluated, the excess volume for the mixtures shows a sigmoidal variation with composition, being negative at low carbon dioxide content and becoming positive with increasing carbon dioxide content. With increasing pressure, excess volumes become less negative.

Increased biological productivity and export production in the glacial Southern Ocean

A range of complementary radionuclide proxies in sediments of the southernmost Atlantic Ocean over the past 140,000 years indicate that glacial periods were characterized by greatly increased fluxes of biogenic detritus out of surface waters. This increase in export production, which may have contributed to lower concentrations of carbon dioxide in the glacial atmosphere, was accompanied by more than a fivefold increase in accumulation of lithogenic iron transported by winds from Patagonian deserts. These observations support the hypothesis that the iron limitation of today's Southern Ocean productivity was relieved in glacial periods by a greater supply of iron from wind-blown dust.

Electrophysiological responses of receptor neurons in mosquito maxillary palp sensilla to carbon dioxide

Sensilla basiconica on the maxillary palps of female Aedes aegypti contain a receptor neuron which produces a phasic-tonic pattern of action potential response to low concentrations (150-300 ppm) of carbon dioxide (CO2), a stimulus known to be involved with host seeking behavior. These receptor neurons respond reliably to small increments in CO2 concentration (e.g., 50 ppm). We were particularly interested in evaluating the possibility that the sensitivity to step increases in CO2 concentration could be modulated by alterations in the background levels of CO2, over a range which might be encountered during host-seeking behavior. We report here that the response (impulses/s) to a single pulse of a given concentration of CO2 appears to be independent of the background level of CO2, unless that level is equal to or greater than the concentration of the stimulus pulse. Females of other mosquito species, including: Anopheles stephensi, Culex quinquefasciatus, Culiseta melanura, and Aedes taeniorhynchus, also possess sensilla with receptor neurons that respond with comparable sensitivity to CO2 stimulation. However, there is much interspecific variation in both the external morphology of the maxillary palp and the distribution of sensilla along the palp. Male Ae. aegypti have morphologically similar sensilla which also contain a receptor neuron that responds to CO2.

Concentration of carbon dioxide in the Late Cretaceous atmosphere

Stable carbon isotope data from Late Cretaceous (Maastrichtian) palaeosols in India are used to estimate the concentration of carbon dioxide in the Late Cretaceous atmosphere. We show that the Maastrichtian atmosphere is unlikely to have contained more than about 1300 ppm by volume of CO 2 .This value agrees with an independently modeled value of CO 2 in the Late Cretaceous atmosphere. A low concentration of the greenhouse gas carbon dioxide in the Maastrichtian atmosphere (relative to concentrations in the earlier Cretaceous) is consistent with palaeotemperature information from terrestrial plant and marine fossils, which suggest that the global climate cooled toward the end of the Cretaceous Period.

Induced lactic acid fermentation during the preservation stage of ripe olives from Hojiblanca cultivar

The influence of initial sodium chloride concentration (6 and 0%, w/v), acetic acid concentration (0.6, 0.3 and 0.0%, v/v), type of process (natural and inoculated), and storage system (anaerobic and aerobic) on the inducement of a lactic fermentation for the preservation stage of Hojiblanca cultivar ripe olives was investigated. The addition of 6% NaCl prevented colonization by lactic acid bacteria in all cases. A high level of acetic acid (0.6%) was effective in preserving olives for 2 months, although yeast growth was not inhibited for longer periods of storage. Natural growth of Lactobacillus plantarum did not occur. Inoculation with this micro‐organism was effective only in the two treatments with tap water (with no NaCl) as the initial covering solution, although survival was reduced to a half of the added organisms when the initial pH was corrected with 0.3% acetic acid. In these two treatments pH quickly reached appropriate values (<4.0) for olive stabilization. Aerobic conditions led to low concentrations of carbon dioxide, without disturbing growth of lactic acid bacteria. Thus, the aerobic lactic acid fermentation, with tap water initially, was the most adequate preservation procedure for the storage of ripe olives prior to their oxidation treatment. Results of trials conducted on an industrial scale showed the same pattern and confirmed the viability of the new procedure.

Effects of reduced waterflow (increased loading) in soft water on Atlantic salmon smolts ( Salmo salar L.) while maintaining oxygen at constant level by oxygenation of the inlet water

Atlantic salmon ( Salmo salar L.) smolts were exposed to three different waterflows: 0.49–0.59 (control), 0.27–0.33 (medium) and 0.16–0.21 liter kg −1min −1 (low) for about two months in soft water. Oxygen was added to the inlet water prior to the medium and low waterflow tanks in order to ensure adequate dissolved oxygen levels. However, as a result of the reduced waterflow to the medium and low waterflow groups, carbon dioxide and total ammonia concentrations were increased and pH was reduced. The concentration of un-ionized ammonia was about the same for the three groups and far lower than established criteria for freshwater fish. The amount of food spillage seemed to be highest in the low waterflow group, probably because of less appetite and a reduced self-cleaning efficiency of the tanks. The respiration frequency of the medium group was slightly increased (although not significantly) during most of the exposure period. After 65 days, the smolts in this group showed reduction in weight and condition factor when compared to the control group. However, the length was not significantly different from the control group. The smolts in the low waterflow group showed increased respiration frequency during most of the exposure period. After 62–65 days of exposure, the hematocrit and hemoglobin levels were increased and plasma chloride, fish weight, length and condition factor were significantly reduced. Histological examination revealed chronic gill lesions with lamellar hypertrophy and hyperplasia. However, a high mortality rate was not observed. When the three groups later were exposed to equalconditions in seawater for 77 days, their mean weight and length were not significantly different. Compensation mechanisms had been stimulated to regain the weight reduction observed during the freshwater exposure. After 102 days in seawater the gill epithelium of the low waterflow group had obviously recovered.

Isotopic Evidence for Reduced Productivity in the Glacial Southern Ocean

Records of carbon and nitrogen isotopes in biogenic silica and carbon isotopes in planktonic foraminifera from deep-sea sediment cores from the Southern Ocean reveal that the primary production during the last glacial maximum was lower than Holocene productivity. These observations conflict with the hypothesis that the low atmospheric carbon dioxide concentrations were introduced by an increase in the efficiency of the high-latitude biological pump. Instead, different oceanic sectors may have had high glacial productivity, or alternative mechanisms that do not involve the biological pump must be considered as the primary cause of the low glacial atmospheric carbon dioxide concentrations.

Cyanobacteria dynamics in a restored Finnish lake: a long term simulation study

Several explanations have been presented for the formation of lacustrine cyanobacteria blooms. These include elevated water temperature, nutrient enrichment, low N/P ratios, low light energy requirements, high pH and/or low carbon dioxide concentration, selective zooplankton grazing, excretion of compounds which suppress the growth of competing algae, and migration. The impact of the first four were studied in Lake Tuusulanjarvi, a eutrophic Finnish lake, using deterministic simulation. The study, which covered 15 years, included a sequence of cases on the recovery of the lake after the implementation of two restoration measures: aeration of the hypolimnion, and termination of municipal waste discharge, both of which were done during the study period. The focus was on Microcystis and Oscillatoria, and on the N-fixing cyanobacteria, Anabaena and Aphanizomenon. Eukaryotic phytoplankton were also included in the study. Monitoring data were used. The roles of the hypotheses were discussed, from the point of view of the utility of the information in water resources management.

Echinocytosis in horses: 54 cases (1990)

Summary: Retrospective review of CBC and serum chemical data from 124 horses admitted to the veterinary teaching hospital over a 9-month period (Feb 1, 1990 to Oct 31, 1990) indicated that 54 horses had echinocytosis (prevalence = 44%). In horses with echinocytosis, the most frequent diagnosis was colitis (23 horses; 43%). Odds ratios (measure of association) were calculated to determine the association of echinocytosis with specific hematologic and biochemical abnormalities. When evaluated in a multivariate model, low serum sodium concentration (< 136 mEq/L) was the only variable significantly associated with the incidence of echinocytosis. Within the group of 54 horses with echinocytosis, hyponatremia (35 horses; 65%), hypochloremia (35 horses; 65%), low total carbon dioxide concentration (35 horses; 65%), hypoosmolality (30 horses; 55%), and hypocalcemia (22 horses; 41%) were the most common biochemical abnormalities. It was concluded that hyponatremia was associated with increased incidence of echinocytosis. It was suggested that systemic electrolyte depletion might be involved in the induction of echinocyte formation.

Expansion of C4 ecosystems as an indicator of global ecological change in the late Miocene

THE most common and the most primitive pathway of the three different photosynthetic pathways used by plants is the C3 pathway, or Calvin cycle, which is characterized by an initial CO2 carboxylation to form phosphoglyceric acid, a 3-carbon acid. The carbon isotope composition (δ13C) of C3 plants varies from about −23 to −35%l–3 and averages about −26%. Virtually all trees, most shrubs, herbs and forbs, and cool-season grasses and sedges use the C3 pathway. In the C4 pathway (Hatch–Slack cycle), CO2 initially combines with phosphoenol pyruvate to form the 4-carbon acids malate or aspartic acid, which are translocated to bundle sheath cells where CO2 is released and used in Calvin cycle reactions1–4. The carbon isotope composition of C4 plants ranges from about −10 to −14%, averaging about −13% for modern plants1–3. Warm-season grasses and sedges are the most abundant C4 plants, although C4 photosynthesis is found in about twenty families5. The third photosynthetic pathway, CAM, combines features of both C3 and C4 pathways. CAM plants, which include many succulents, have intermediate carbon isotope compositions and are also adapted to conditions of water and CO2 stress. The modern global ecosystem has a significant component of C4 plants, primarily in tropical savannas, temperate grasslands and semi-desert scrublands. Studies of palaeovegetation from palaeosols and palaeodiet from fossil tooth enamel indicate a rapid expansion of C4 biomass in both the Old World and the New World starting 7 to 5 million years ago. We propose that the global expansion of C4 biomass may be related to lower atmospheric carbon dioxide levels because C4 photosynthesis is favoured over C3 photosynthesis when there are low concentrations of carbon dioxide in the atmosphere.