Effects Of Long-term CO Research Articles

Long-term effects of CO2-water-coal interactions on structural and mechanical changes of bituminous coal

Structural integrity and mechanical stability of coal are important regarding the long-term safety of CO 2 sequestration in coal. To date, little understanding exists on long-term effects of CO 2 injection at presence of water on structural and mechanical properties of coal. In this study, bituminous coal samples were saturated with CO 2 at pressures from 4 to 10 MPa, with presence of water, for saturation time up to 25 weeks. Uniaxial compression tests and X-ray computed tomography were conducted to study changes in mechanical properties and microstructures of coal. The results show, after CO 2 injection with presence of water, the mechanical properties of coal changed, including the reduction of uniaxial compression strength (up to ~50%) and Young's modulus (up to ~65%). The reduction of mechanical properties was closely related to the structural damage due to sorption-induced cracking. The changes of mechanical properties were significantly affected by CO 2 phase state and slightly affected by saturation time. Rapid reduction of mechanical properties was found when CO 2 transitioned from subcritical to supercritical state and the failure modes changed from a brittle failure (shear fractures) to a ductile failure (multiple fractures) during this transition. When saturation duration increased from 3 up to 25 weeks, limited further reduction occurred and it was related to the wormhole formation due to coal matrix dissolution. Overall, the dominated cause for coal softening after CO 2 injection in presence of water was sorption-induced cracking, which is similar to the case of pure CO 2 injection without water. However, the reduction extent after CO 2 injection in presence of water seems to be less at the same pressure conditions compared to that after pure CO 2 injection. This is because the presence of water may potentially hinder CO 2 sorption on coal. • The structural and mechanical properties of coal treated by CO 2 at presence of water for long-term were investigated. • The CO 2 +water treatment caused reductions of UCS values up to ~50% and the Young’s modulus up to ~65%. • The reductions of mechanical properties were closely related to the structural damage due to sorption-induced cracking. • The mechanical properties were significantly affected by CO 2 phase state and slightly affected by saturation time. • Rapid reductions in mechanical properties happened when CO 2 transitioned from subcritical to supercritical state. • The failure modes of coal changed from a brittle failure to a ductile failure during CO 2 phase transition.

Effects of ocean acidification on macroalgal communities

There are high levels of uncertainty about how coastal ecosystems will be affected by rapid ocean acidification caused by anthropogenic CO 2, due to a lack of data. The few experiments to date have been short-term (< 1 year) and reveal mixed responses depending on the species examined and the culture conditions used. It is difficult to carry out long-term manipulations of CO 2 levels, therefore areas with naturally high CO 2 levels are being used to help understand which species, habitats and processes are resilient to the effects of ocean acidification, and which are adversely affected. Here we describe the effects of increasing CO 2 levels on macroalgal communities along a pH gradient caused by volcanic vents. Macroalgal habitat differed at taxonomic and morphological group levels along a pH gradient. The vast majority of the 101 macroalgal species studied were able to grow with only a 5% decrease in species richness as the mean pH fell from 8.1 to 7.8. However, this small fall in species richness was associated with shifts in community structure as the cover of turf algae decreased disproportionately. Calcitic species were significantly reduced in cover and species richness whereas a few non-calcified species became dominant. At mean pH 6.7, where carbonate saturation levels were < 1, calcareous species were absent and there was a 72% fall in species richness. Under these extremely high CO 2 conditions a few species dominated the simplified macroalgal assemblage and a very few exhibited enhanced reproduction, although high CO 2 levels seemed to inhibit reproduction in others. Our data show that many macroalgal species are tolerant of long-term elevations in CO 2 levels but that macroalgal habitats are altered significantly as pH drops, contributing to a scant but growing body of evidence concerning the long-term effects of CO 2 emissions in vegetated marine systems. Further study is now needed to investigate whether the observed response of macroalgal communities can be replicated in different seasons and from a range of geographical regions for incorporation into global modelling studies to predict effects of CO 2 emissions on Earth's ecosystems.

Long-term effects of CO&lt;sub&gt;2&lt;/sub&gt; enrichment on bud phenology and shoot growth patterns of Norway spruce juvenile trees

Bud phenology and shoot elongation growth were monitored on Norway spruce (Picea abies [L.] Karst.) trees grown inside glass domes with adjustable windows for six years under ambient (355 &amp;micro;mol CO&lt;sub&gt;2&lt;/sub&gt;∙mol&lt;sup&gt;&amp;ndash;1&lt;/sup&gt;) and elevated (700 &amp;micro;mol CO&lt;sub&gt;2&lt;/sub&gt;∙mol&lt;sup&gt;&amp;ndash;1&lt;/sup&gt;) atmospheric CO&lt;sub&gt;2&lt;/sub&gt; concentrations CO&lt;sub&gt;2&lt;/sub&gt;. Each treatment consisted of two stand densities &amp;ndash; sparse (5,000 trees∙ha&lt;sup&gt;&amp;ndash;1&lt;/sup&gt;) and dense (10,000 trees∙ha&lt;sup&gt;&amp;ndash;1&lt;/sup&gt;). The age of spruce trees was 10 years at the beginning of the experiment.Elevated CO&lt;sub&gt;2&lt;/sub&gt; slightly accelerated the consequential bud germinating phases and it significantly induced shoot elongation growth, especially of sun-exposed shoots in a stand with sparse density. This accelerated growth lasted one to three weeks after full bud development in E compared to A. At the end of the growing season the total shoot length did not show any differences between the treatments. We supposed that limiting nitrogen supply to needles slowed down subsequent shoot elongation growth in E treatment. Nevertheless, faster shoot growth in elevated CO&lt;sub&gt;2&lt;/sub&gt; conditions can enhance the carbon sink in spruce due to prolongation of the growing season.

Effects of long-term CO 2 fumigation on fungal communities in a temperate forest soil

This study aimed at determining the impact of long-time elevated CO 2 fumigation on fungal communities in a temperate forest soil. In addition to the CO 2 concentration, both time and its interaction with the CO 2 affected the activity of 1,4-β-N-acetylglucosaminidase that is mainly of the fungal origin in the soil. No significant change in Shannon's indexes (from 18S rDNA-PCR–DGGE) was observed between the ambient and elevated CO 2 treatments. Analysis of time-course indicated that the succession of soil fungal community was altered by the elevated CO 2 fumigation, and the variations in the soil samples under Pinus koraiensis Sieb. et Zucc were larger than those under the Pinus sylvestriformis (Takenouchi) T. Wang ex Cheng samples. The results suggest that the increase in atmospheric CO 2 concentrations could alter the temporal patterning of soil fungal communities.

Improving wellbore seal integrity in CO2 injection wells

Abstract Work on Carbon Sequestration in subterranean formations has renewed interest in investigating the long term effects of CO 2 on Portland cements. Portland cement will react with the injected CO 2 , and while recent research indicates these conventional cements are not a concern, additional work is ongoing to further improve the long term effectiveness of the wellbore sealant. This paper discusses various solutions to the challenges of selecting a proper wellbore sealant for a CO 2 injection well. Additionally, the paper reviews the available sealant technologies, their application, and includes a discussion of stress modelling for these wells. A brief case history review of the design considerations for two high-rate acid gas injection wells in Wyoming is discussed.

Effects of long term CO2enrichment on microbial community structure in calcareous grassland

Elevated CO 2 generally increases plant productivity, and has been found to alter plant community composition in many ecosystems. Because soil microbes depend on plant-derived C and are often associated with specific plant species, elevated CO 2 has the potential to alter structure and functioning of soil microbial communities. We investigated soil microbial community structure of a species-rich semi-natural calcareous grassland that had been exposed to elevated CO 2 (600 μL L -1 ) for 6 growing seasons. We analysed microbial community structure using phospholipid fatty acid (PLFA) profiles and DNA fingerprints obtained by Denaturing Gradient Gel Electrophoresis (DGGE) of 16S rDNA fragments amplified by the Polymerase Chain Reaction (PCR). PLFA profiles were not affected by CO 2 enrichment and the ratio of fungal and bacterial PLFA did not change. Ordination analysis of DNA fingerprints revealed a significant relation between CO 2 enrichment and variation in DNA fingerprints in summer (P = 0.01), but not in spring. This variation was due to changes in low-intensity bands, while dominant bands did not differ between CO 2 treatments. Diversity of the bacterial community, as assessed by number of bands in DNA fingerprints and calculation of Shannon diversity indices, was not affected by elevated CO 2 . Overall, only minor effects on microbial community structure were detected, corroborating earlier findings that soil carbon inputs did probably change much less than suggested by plant photosynthetic responses.

Influence of ocean CO 2 sequestration on bacterial production

Carbon dioxide in the atmosphere is a major greenhouse gas. Increasing atmospheric concentrations are believed to be responsible for a gradual warming of the Earth. Strategies to reduce anthropogenic CO 2 emissions to the atmosphere by sequestration underground or in the deep ocean are being investigated. An international collaboration to conduct a field experiment on CO 2 ocean sequestration was initiated in December 1997. The primary objective of this project is to obtain data that can be applied to assess environmental impacts of direct injection of CO 2 into the deep ocean. The collaboration is being implemented by a research team comprising engineers and scientists from five nations: Japan, the US, Norway, Canada, and Australia. This paper focuses on studies being conducted as part of the field experiment to investigate the influence of decreased seawater pH from CO 2 dissolution on bacterial production in the ocean. A preliminary analysis of the variation in bacterial production under different values of pH and temperature, conducted in July 1999, indicated that there was no measurable effect on the microbial population in the first 24 h of the experiment. However, there was a rapid decline in bacterial production with decreases in pH over a 96 h incubation period. In addition, the impact of reduced pH was more pronounced when the bacteria were grown at warmer temperatures, i.e. with a more rapid potential production rate. Subsequent laboratory experiments were conducted in June 2000 using pressure chambers to determine the effect of depressurization on bacterial production. For this effort, seawater samples were collected from a 600 m deep pipeline off the Kona coast of the island of Hawaii. Water was placed in a pressure chamber and allowed to stabilize for 48 h at the ambient pressure and temperature of 600 m depth at the sampling location. After 48 h, the water was depressurized and acidified with CO 2 to pH values of 6.95 and 5.6. The acidified water and an un-amended sample were incubated at 5, 10 and 15 °C for 96 h and sampled every 24 h. Similar impacts to those observed previously on the bacterial production were noted. The overall result was that longer incubation times and warmer temperatures reduced bacterial production in samples exposed to the lower pH. This observation is beneficial to develop an understanding of the long term effects of CO 2 releases on basic elemental cycles that support aquatic food chains. Future work needs to investigate long term variation in the bacterial community, the impact on nutrient recycling, and the population growth efficiency.

Effects of long-term CO 2 enrichment and nutrient availability in Norway spruce. II. Foliar chemistry

Branches on 30-year-old Norway spruce trees [Picea abies (L.) Karst.] were exposed to ambient (AMB) or ambient plus 350 μmol CO2 mol–1 (EL) for 4 years (except winters), using the branch bag technique (BB). The trees were growing on plots with low (control) and high (irrigated-fertilised) availability of soil nutrients. The seasonal variation in foliar macronutrients and non-structural carbohydrates in current and 1-year-old shoots was monitored throughout the treatment period. When the branches were harvested at the end of treatment, macronutrients were analysed in five age classes of foliage. The concentration of all elements, except magnesium, generally increased in AMB, i.e. a ’bag effect’, but decreased as an effect of EL, i.e. a ’CO2 effect’. At the final harvest K, P, N and S were reduced in young needles by EL, whereas Mg was reduced in older needles on both plots. A change in needle morphology by EL possibly caused a dilution effect in irrigated-fertilised needles, but not in control needles. Reductions in K and Mg are suggested to be an effect of increased phloem transport from the branch, in consequence of higher rates of carbon fixation in EL. Foliage in BBs had higher concentration of Ca, but there was no significant effect of the EL-treatment, indicating that elevated CO2 had no effect on stomatal conductance. Quinic acid concentration decreased, but shikimic acid concentration increased in BBs, independently of CO2 treatment. Concentrations of starch and sugars increased in the EL-treatment, but pinitol decreased.

Effects of long-term CO

Effects of long-term CO

Effects of long-term CO 2 and temperature elevation on crown nitrogen distribution and daily photosynthetic performance of Scots pine

Single Scots pines ( Pinus sylvestris L.), aged 20–25 years, were grown in open-top chambers and exposed to elevated temperature (Elev. T), elevated CO 2 (Elev. C) and a combination of elevated CO 2 and temperature (Elev. C + T) for 4 years. The vertical distribution of needle nitrogen concentration was measured simultaneously with gas exchange of attached shoots. Based on the measurements, the dependencies on needle nitrogen concentrations of four photosynthetic parameters, i.e., RuP 2 (ribulose 1,5-bisphosphate)-saturated rate of carboxylation ( V cmax), maximum potential electron transport ( J max), the rate of respiration in the light ( R d) and light-use-efficiency factor (δ), were determined. Using a crown multilayer model, the performance of daily crown photosynthesis in Scots pine was predicted. Compared to the control treatment, the mean concentration of nitrogen in the foliage decreased by 20% and by 17% for trees grown under Elev. C and under Elev. C + T, respectively, but increased by 4% for trees grown under Elev. T. However, the total content of foliage nitrogen per unit ground area increased by 25% for trees grown under Elev. C, by 19% for trees grown under Elev. C + T and by 6% for trees grown under Elev. T; these were due to the increase in the total needle area index. Regressions showed that the foliage grown under Elev. C and Elev. C + T had steeper slopes representing the responses of V cmax, R d and δ to leaf nitrogen concentrations, while Elev. C + T and Elev. T had steeper slopes representing the response of J max to needle nitrogen concentrations. Predictions showed that, on a typical sunny day, the daily total of crown photosynthesis increased 22% and 27%, separately for Elev. C and Elev. C + T, and by only 9% for Elev. T alone. Furthermore, the increased daily crown photosynthesis, resulting from treatments involving elevated CO 2, can be attributed mainly to an increase in the ambient CO 2 concentration and the needle area index, while modification of the intrinsic photosynthetic capacity had only a marginal effect. Based on the current pattern of crown nitrogen allocation, the prediction showed also that the relationship between daily crown photosynthesis and crown nitrogen content was strongly dependent on the daily incident PAR and air temperature. The CO 2-elevated treatments led to an increase in the sensitivity of daily crown photosynthesis to changes in crown nitrogen content, daily incident PAR and temperature, while the temperature-elevated treatment had the opposite effect on the sensitivity.

Long-term effects of CO2enrichment and temperature increase on the carbon balance of a temperate grass sward

Perennial ryegrass swards were grown in large containers on a soil, at two N fertilizer supplies and were exposed during two years in highly ventilated plastic tunnels to elevated (700 μl l−1 [CO2) or ambient atmospheric CO2 concentration at outdoor temperature and to a 3°C increase in air temperature in elevated CO2. The irrigation was adjusted to obtain a soil water deficit during summer. The daily net C assimilation was increased in elevated CO2 by 29 and 36% at the low and high N supplies, respectively. Canopies grown in elevated CO2 for 14 to 27 months photosynthetized significantly less rapidly, in both elevated and normal CO2 concentrations, than their counterparts developed in ambient CO2 but the magnitude of this effect was small (−8% to −13%). Elevated CO2 resulted in a large increase in the fructan concentration in the pseudostems and laminae (+46% and +189%, respectively). In elevated CO2, the hexose and sucrose pool increased by 28% in the laminae, whereas it did not vary significantly in the pseudo-stems. A 3°C temperature increase in elevated CO2 did not affect significantly the average WSC concentrations in the pseudostems and laminae. The elevated CO2 effects on the net C assimilation and on the nocturnal shoot respiration were greater in summer than in spring. On average, a 35% increase in the below-ground respiration was measured in elevated CO2. At the high N supply, a 3°C increase in air temperature led to a decline in the below-ground respiration due to a low soil moisture. The below-ground carbon storage was increased by 32% and 96% in elevated CO2 at the low and high N supplies, respectively, with no significant increased temperature effect. The role for the below-ground carbon storage of CO2-induced changes in the root fraction of the grass and of temperature-induced changes in the moisture content of the soil are discussed.

Interactions of CO 2 enrichment and temperature on carbohydrate accumulation and partitioning in rice

The objective of this study was to determine the long-term effects of CO 2 concentration and temperature on carbohydrate partitioning and status in rice ( Oryza sativa L. cv. IR-30). The plants were grown season-long in sunlit, controlled-environment chambers with CO 2 concentrations of 330 or 660 μmol mol −1, and daytime air temperatures of 28, 34 or 40°C. In leaf blades, the priority between partitioning of carbon into storage or into export changed with CO 2 concentration and temperature. Leaf sucrose concentration increased with CO 2 enrichment at all temperature regimes. Over the season, elevated CO 2 resulted in an increase in total non-structural carbohydrate (TNC) concentration in leaf blades, leaf sheaths and culms at all temperature treatments. Elevated CO 2 had no effect on carbohydrate concentration in the grain at maturity, however, grain TNC concentration was significantly lowered by increasing temperature. Under the highest temperature regime, the plants in the 330 μmol mol −1 CO 2 treatment died during stem extension while the CO 2 enriched plants survived but produced sterile panicles. The results suggest that CO 2-enriched plants could survive and maintain carbohydrate production rates at higher temperatures than the non-enriched plants; however, the optimum temperature for TNC accumulation was 28°C at both CO 2 concentrations.