Reducing CO2 Levels Research Articles

The future of grazing research

The future of grazing research

Low-Flow Veno-Venous Extracorporeal CO2 Removal: First Clinical Experience in Lung Transplant Recipients

Low-flow extracorporeal CO2 removal devices are easy to setup and manage and may provide valuable ventilation support. We employed a new device (ProLUNG) recently introduced into the clinical arsenal that exploits a simple hemoperfusion technique sustained by blood flows lower than 500 ml/min to remove CO2 from the venous blood. It was used as an adjunctive support to mechanical ventilation during and after four lung transplantations in our center. Two patients with cystic fibrosis, one with pulmonary fibrosis, and one with emphysema were included. They underwent lung transplantation and presented hypercapnia and respiratory acidosis before, during, or after the surgical procedure. After 1 h of treatment with the ProLUNG circuit, all patients showed reduced CO2 levels and increased pH; these variables remained stable until the end of treatment. Our data suggest that this new device is effective in removing CO2 and stabilizing the pH.

Use of visual CO2 feedback as a retrofit solution for improving classroom air quality.

Carbon dioxide (CO2 ) sensors that provide a visual indication were installed in classrooms during normal school operation. During 2-week periods, teachers and students were instructed to open the windows in response to the visual CO2 feedback in 1week and open them, as they would normally do, without visual feedback, in the other week. In the heating season, two pairs of classrooms were monitored, one pair naturally and the other pair mechanically ventilated. In the cooling season, two pairs of naturally ventilated classrooms were monitored, one pair with split cooling in operation and the other pair with no cooling. Classrooms were matched by grade. Providing visual CO2 feedback reduced CO2 levels, as more windows were opened in this condition. This increased energy use for heating and reduced the cooling requirement in summertime. Split cooling reduced the frequency of window opening only when no visual CO2 feedback was present.

Elevation‐induced climate change as a dominant factor causing the late Miocene C4 plant expansion in the Himalayan foreland

During the late Miocene, a dramatic global expansion of C4 plant distribution occurred with broad spatial and temporal variations. Although the event is well documented, whether subsequent expansions were caused by a decreased atmospheric CO2 concentration or climate change is a contentious issue. In this study, we used an improved inverse vegetation modeling approach that accounts for the physiological responses of C3 and C4 plants to quantitatively reconstruct the paleoclimate in the Siwalik of Nepal based on pollen and carbon isotope data. We also studied the sensitivity of the C3 and C4 plants to changes in the climate and the atmospheric CO2 concentration. We suggest that the expansion of the C4 plant distribution during the late Miocene may have been primarily triggered by regional aridification and temperature increases. The expansion was unlikely caused by reduced CO2 levels alone. Our findings suggest that this abrupt ecological shift mainly resulted from climate changes related to the decreased elevation of the Himalayan foreland.

Meta-analysis reveals profound responses of plant traits to glacial CO2 levels.

A general understanding of the links between atmospheric CO2 concentration and the functioning of the terrestrial biosphere requires not only an understanding of plant trait responses to the ongoing transition to higher CO2 but also the legacy effects of past low CO2. An interesting question is whether the transition from current to higher CO2 can be thought of as a continuation of the past trajectory of low to current CO2 levels. Determining this trajectory requires quantifying the effect sizes of plant response to low CO2. We performed a meta-analysis of low CO2 growth experiments on 34 studies with 54 species. We quantified how plant traits vary at reduced CO2 levels and whether C3 versus C4 and woody versus herbaceous plant species respond differently. At low CO2, plant functioning changed drastically: on average across all species, a 50% reduction in current atmospheric CO2 reduced net photosynthesis by 38%; increased stomatal conductance by 60% and decreased intrinsic water use efficiency by 48%. Total plant dry biomass decreased by 47%, while specific leaf area increased by 17%. Plant types responded similarly: the only significant differences being no increase in SLA for C4 species and a 16% smaller decrease in biomass for woody C3 species at glacial CO2. Quantitative comparison of low CO2 effect sizes to those from high CO2 studies showed that the magnitude of response of stomatal conductance, water use efficiency and SLA to increased CO2 can be thought of as continued shifts along the same line. However, net photosynthesis and dry weight responses to low CO2 were greater in magnitude than to high CO2. Understanding the causes for this discrepancy can lead to a general understanding of the links between atmospheric CO2 and plant responses with relevance for both the past and the future.

Indoor Air Quality in U.K. School Classrooms Ventilated by Natural Ventilation Windcatchers

The provision of good IAQ in schools is important both for the health of students and in maximising educational achievement. It is, however, common for school classrooms to be significantly under-ventilated and this can lead to high levels of CO2 and other pollutants. Natural ventilation offers the potential to improve IAQ within schools whilst, at the same time reducing running and maintenance costs. Accordingly, this article examines a natural ventilation strategy based on the use of a roof mounted split-duct Windcatcher ventilator. Here, 16 U.K. classrooms are studied and CO2, temperature, relative humidity and ventilation rates are measured for the summer and winter seasons. Results show that, during the summer months, the ventilator is capable of significantly improving ventilation rates as well as reducing CO2 levels, especially when used in combination with open windows. However, in the winter months, the ventilator is seen not to open for a sufficient length of time and so CO2 levels rise above those required in the standards. Thus, the ventilator is shown to have the potential to improve IAQ within school classrooms, but the operation of the ventilator should be carefully controlled in order to realise these benefits.It is common for ventilation rates in school classrooms to fall below the levels required by relevant standards. The data presented here demonstrates that by using a top-down natural ventilation Windcatcher as part of a well designed natural ventilation strategy, ventilation rates in school classrooms can be significantly improved.

Changes in pH during transport of juvenile cod Gadus morhua L. and stabilisation using buffering agents

Salmonids have been transported from hatchery to ongrowing units for many years, but little information is available on optimal conditions for the transport of marine finfish species. This study examined the changes in pH that occur under various simulated transport conditions of stocking density and fish size, and thereby recommends protocols for live marine fish transportation. The pH of the transport water declined rapidly due to the respiration of carbon dioxide. Various buffers (sodium bicarbonate, TRIS, Magnaspheres) were compared and maintained pH close to normal seawater levels. The decline in pH was greater with small (18g) rather than larger (32g) fish, at identical loading biomass in tanks, indicating that fish size should be considered when planning transport. Although unionised ammonia level increased with increasing stocking density (10 to 30kgm−3) the pH did not decline significantly. The use of air aeration as well as oxygenation reduced CO2 levels indicating that aeration stripped the CO2 from the water. Non invasive measurements of free cortisol release into the tank water by juvenile cod indicated primary stress response to handling events. This study demonstrates that cod juveniles will be exposed to fluctuating pH in transport tanks, and buffering of the pH and stripping of CO2 by aeration to reduce fluctuations is recommended.

Ecological engineering for climate mitigation and adaptation—a case study for the North West Shelf

This paper introduces the Australian-developed Ocean Nourishment technology, as well as the science, its regulation, and its potential commercial application for the North West Shelf. Ocean nourishment is a form of ecological engineering, designed to transfer carbon from the ocean's sunlit surface zone to the largest carbon sink on the planet: the ocean. It is a scaleable and economical form of bio-mimicry; simulating the ocean's natural biological processes. Nourishing the surface ocean with macronutrients increases the movement of atmospheric CO2 into the deep-ocean carbon store. Short lifecycle microscopic plants—which are prolific carbon consumers—use sunlight to process the added nutrients. This additional marine productivity leads to reduced CO2 levels in both the upper ocean and in the atmosphere. Dispersing nitrogen alone allows the potential long-term (1,000 years) removal of one tenth (0.8 Gt carbon/annum) of present anthropogenic emissions. In addition to carbon sequestration, there is a desirable by-product of the process. The increased marine productivity will lead to increased fish stocks, which will assist in feeding the world's human population. Individual licensed sites would be capable of sequestering 5–8 Mt of CO2 at $25–35 per tonne. This is estimated to produce an additional harvest of 300,000 tonnes of fish each year. The path to commercialisation for such a promising technology with global reach and untried application requires focussed scientific application. Establishing revenue streams for carbon sequestration or fisheries enhancement is complex. International regulation is being addressed by the LondonConvention/London Protocol of the International Maritime Organisation.

Reducing CO2 levels—so many ways, so few being taken

Reducing CO2 levels—so many ways, so few being taken

Cell evolution and Earth history: stasis and revolution.

This synthesis has three main parts. The first discusses the overall tree of life and nature of the last common ancestor (cenancestor). I emphasize key steps in cellular evolution important for ordering and timing the major evolutionary innovations in the history of the biosphere, explaining especially the origins of the eukaryote cell and of bacterial flagella and cell envelope novelties. Second, I map the tree onto the fossil record and discuss dates of key events and their biogeochemical impact. Finally, I present a broad synthesis, discussing evidence for a three-phase history of life. The first phase began perhaps ca 3.5 Gyr ago, when the origin of cells and anoxic photosynthesis generated the arguably most primitive prokaryote phylum, Chlorobacteria (= Chloroflexi), the first negibacteria with cells bounded by two acyl ester phospholipid membranes. After this 'chlorobacterial age' of benthic anaerobic evolution protected from UV radiation by mineral grains, two momentous quantum evolutionary episodes of cellular innovation and microbial radiation dramatically transformed the Earth's surface: the glycobacterial revolution initiated an oxygenic 'age of cyanobacteria' and, as the ozone layer grew, the rise of plankton; immensely later, probably as recently as ca 0.9 Gyr ago, the neomuran revolution ushered in the 'age of eukaryotes', Archaebacteria (arguably the youngest bacterial phylum), and morphological complexity. Diversification of glycobacteria ca 2.8 Gyr ago, predominantly inhabiting stratified benthic mats, I suggest caused serial depletion of 13C by ribulose 1,5-bis-phosphate caboxylase/oxygenase (Rubisco) to yield ultralight late Archaean organic carbon formerly attributed to methanogenesis plus methanotrophy. The late origin of archaebacterial methanogenesis ca 720 Myr ago perhaps triggered snowball Earth episodes by slight global warming increasing weathering and reducing CO2 levels, to yield runaway cooling; the origin of anaerobic methane oxidation ca 570 Myr ago reduced methane flux at source, stabilizing Phanerozoic climates. I argue that the major cellular innovations exhibit a pattern of quantum evolution followed by very rapid radiation and then substantial stasis, as described by Simpson. They yielded organisms that are a mosaic of extremely conservative and radically novel features, as characterized by De Beer's phrase 'mosaic evolution'. Evolution is not evenly paced and there are no real molecular clocks.

Carbon dioxide cycling through the mantle and implications for the climate of ancient Earth

Abstract The continental cycle of silicate weathering and metamorphism dynamically buffers atmospheric CO 2 and climate. Feedback is provided by the temperature dependence of silicate weathering. Here we argue that hydrothermal alteration of oceanic basalts also dynamically buffers CO 2 . The oceanic cycle is linked to the mantle via subduction of carbonatized basalts and degassing of CO 2 at the mid-ocean ridges. Feedback is provided by the dependence of carbonatization on the amount of dissolved carbonate in sea water. Unlike the continental cycle, the oceanic cycle has no thermostat. Hence surface temperatures can become very low if CO 2 is the only greenhouse gas apart from water. Currently the continental cycle is more important, but early in Earth’s history the oceanic cycle was probably dominant. We argue that CO 2 greenhouses thick enough to defeat the faint early Sun are implausible and that, if no other greenhouse gases are invoked, very cold climates are expected for much of Proterozoic and Archaean time. We echo current fashion and favour biogenic methane as the chief supplement to CO 2 . Fast weathering and probable subduction of abundant impact ejecta would have reduced CO 2 levels still further in Hadean time. Despite its name, the Hadean Eon might have been the coldest era in the history of the Earth.

Photorespiration is More Effective than the Mehler Reaction in Protecting the Photosynthetic Apparatus against Photoinhibition

AbstractI. Isolated intact chloroplasts: Photosystem II, but not photosystem I, of the electron transport chain is rapidly photoinactivated even by very low intensities of red light when no large proton gradient can be formed and the electron transport chain becomes over‐reduced in the absence of oxygen and other reducable substrates. Electron acceptors including oxygen provide protection against photoinactivation. Nevertheless, photosystem II is rapidly, and photosystem I more slowly, photoinactivated by high intensities of red light when oxygen is the only electron acceptor available. Increased damage is observed at increased oxygen concentrations although catalase is added to destroy H2O2 formed during oxygen reduction in the Mehler reaction. Photoinactivation can be decreased, but not prevented by ascorbate which reduces hydrogen peroxide inside the chloroplasts and increases coupled electron flow.II. Leaves: Simple measurements of chlorophyll fluorescence permit assessment of damage to photosystem II after exposure of leaves to high intensity illumination. In contrast to isolated chloroplasts, chloroplasts suffer more damage in situ at reduced than at elevated oxygen concentrations. The difference in the responses is due to photorespiration which is active in leaves, but not in isolated chloroplasts. After photosynthesis and photorespiration are inhibited by feeding glyceraldehyde to leaves, photoinactivation is markedly increased, although oxygen reduction in the Mehler reaction is not affected by glyceraldehyde. In the presence of reduced CO2 levels, photorespiratory reactions, but not the Mehler reaction, can prevent the overreduction of the electron transport chain. Over‐reduction indicates ineffective control of photosystem II activity. Effective control is needed for protection of the electron transport chain against photoinactivation. It is suggested to be made possible by coupled cyclic electron flow around photosystem I which is facilitated by the redox poising resulting from the interplay between photorespiratory carbohydrate oxidation and the refixation of evolved CO2.

Metabolism and Export of 14C-Labelled Photosynthate From Water-Stressed Leaves

The effect of water stress on the translocation of 14C-labelled photosynthate from leaves was examined in four contrasting plant species, Sorghum sudanense (Piper) Stapf. (C4, monocot), Triticum aestivum L. (C3, monocot), Amaranthus caudatus L. (C4, dicot) and Helianthus annuus L. (C3, dicot). Water stress reduced the rate of loss of 14C from the leaves of all species following a pulse application of 14CO2, but the effects of stress were most apparent in sorghum and sunflower, the species with the highest control rates of export. Slower labelling of sucrose, following the application of 14CO2, could explain the reduced rate of export of 14C from stressed wheat leaves, but this would not explain the response in sorghum. An examination of the products of 14CO2 fixation in wheat leaves suggests that the changes in metabolism of 14C under stress may be due to reduced CO2 levels, resulting from stomatal closure. In contrast the change in metabolism of 14C-labelled photosynthate due to water stress in sorghum was very different from that expected in response to reduced CO2 levels. Prevention of translocation of photosynthate out of a leaf of either wheat or sorghum, by steam killing the tissue at the base of the blade, altered the pattern of labelling of metabolites with 14C following a pulse of 14CO2. However changes in translocation due to reduced export associated with a reduction in growth under water stress did not appear to play a part in the responses observed in these experiments.

The Gas Exchange Capacity of Plants in Relation to Vegetation Zonation in the White Mountains of California

Photosynthetic and respiration rates were measured in the field on plants of many species growing between the elevations of 4,500 and 12,700 ft in the White Mts. of California. No relation was found between photosynthetic rate and the elevation at which the plants were growing. However, plants representing both tree and shrub species of high elevations generally had greater respiration rates and lower photosynthesis/respiration ratios at the same temperature than did members of low elevation species. Gas exchange rates of plants of diverse elevational origin grown from seed in a uniform ernvironment were measured at a series of temperatures and CO2 levels. Certain of the trends and rates measured in the field were not maintained in the greenhouse-cultivated plants, indicating considerable, environmentally conditioned plasticity in gas exchange capacity. However, when cultivated in a uniform environment the high elevation plants generally displayed peak photosynthetic activity at temperatures lower than the low elevation plants. No relation was found between the elevation origin of a plant and photosynthetic efficiency at reduced CO2 levels.