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G CO2 (g + co2)
Terms modified by G CO2 Selected AbstractsCarbon dioxide balance of a fen ecosystem in northern Finland under elevated UV-B radiationGLOBAL CHANGE BIOLOGY, Issue 4 2009JAANA K. HAAPALA Abstract The effect of elevated UV-B radiation on CO2 exchange of a natural flark fen was studied in open-field conditions during 2003,2005. The experimental site was located in Sodankylä in northern Finland (67°22,N, 26°38,E, 179 m a.s.l.). Altogether 30 study plots, each 120 cm × 120 cm in size, were randomly distributed between three treatments (n=10): ambient control, UV-A control and UV-B treatment. The UV-B-treated plots were exposed to elevated UV-B radiation level for three growing seasons. The instantaneous net ecosystem CO2 exchange (NEE) and dark respiration (RTOT) were measured during the growing season using a closed chamber method. The wintertime CO2 emissions were estimated using a gradient technique by analyzing the CO2 concentration in the snow pack. In addition to the instantaneous CO2 exchange, the seasonal CO2 balances during the growing seasons were modeled using environmental data measured at the site. In general, the instantaneous NEE at light saturation was slightly higher in the UV-B treatment compared with the ambient control, but the gross photosynthesis was unaffected by the exposure. The RTOT was significantly lower under elevated UV-B in the third study year. The modeled seasonal (June,September) CO2 balance varied between the years depending on the ground water level and temperature conditions. During the driest year, the seasonal CO2 balance was negative (net release of CO2) in the ambient control and the UV-B treatment was CO2 neutral. During the third year, the seasonal CO2 uptake was 43±36 g CO2 -C m,2 in the ambient control and 79±45 g CO2 -C m,2 in the UV-B treatment. The results suggest that the long-term exposure to high UV-B radiation levels may slightly increase the CO2 accumulation to fens resulting from a decrease in microbial activity in peat. However, it is unlikely that the predicted development of the level of UV-B radiation would significantly affect the CO2 balance of fen ecosystems in future. [source] Initial cultivation of a temperate-region soil immediately accelerates aggregate turnover and CO2 and N2O fluxesGLOBAL CHANGE BIOLOGY, Issue 8 2006A. STUART GRANDY Abstract The immediate effects of tillage on protected soil C and N pools and on trace gas emissions from soils at precultivation levels of native C remain largely unknown. We measured the response to cultivation of CO2 and N2O emissions and associated environmental factors in a previously uncultivated U.S. Midwest Alfisol with C concentrations that were indistinguishable from those in adjacent late successional forests on the same soil type (3.2%). Within 2 days of initial cultivation in 2002, tillage significantly (P=0.001, n=4) increased CO2 fluxes from 91 to 196 mg CO2 -C m,2 h,1 and within the first 30 days higher fluxes because of cultivation were responsible for losses of 85 g CO2 -C m,2. Additional daily C losses were sustained during a second and third year of cultivation of the same plots at rates of 1.9 and 1.0 g C m,2 day,1, respectively. Associated with the CO2 responses were increased soil temperature, substantially reduced soil aggregate size (mean weight diameter decreased 35% within 60 days), and a reduction in the proportion of intraaggregate, physically protected light fraction organic matter. Nitrous oxide fluxes in cultivated plots increased 7.7-fold in 2002, 3.1-fold in 2003, and 6.7-fold in 2004 and were associated with increased soil NO3, concentrations, which approached 15 ,g N g,1. Decreased plant N uptake immediately after tillage, plus increased mineralization rates and fivefold greater nitrifier enzyme activity, likely contributed to increased NO3, concentrations. Our results demonstrate that initial cultivation of a soil at precultivation levels of native soil C immediately destabilizes physical and microbial processes related to C and N retention in soils and accelerates trace gas fluxes. Policies designed to promote long-term C sequestration may thus need to protect soils from even occasional cultivation in order to preserve sequestered C. [source] CO2 exchange in three Canadian High Arctic ecosystems: response to long-term experimental warmingGLOBAL CHANGE BIOLOGY, Issue 12 2004Jeffrey M. Welker Abstract Carbon dioxide exchange, soil C and N, leaf mineral nutrition and leaf carbon isotope discrimination (LCID-,) were measured in three High Arctic tundra ecosystems over 2 years under ambient and long-term (9 years) warmed (,2°C) conditions. These ecosystems are located at Alexandra Fiord (79°N) on Ellesmere Island, Nunavut, and span a soil water gradient; dry, mesic, and wet tundra. Growing season CO2 fluxes (i.e., net ecosystem exchange (NEE), gross ecosystem photosynthesis (GEP), and ecosystem respiration (Re)) were measured using an infrared gas analyzer and winter C losses were estimated by chemical absorption. All three tundra ecosystems lost CO2 to the atmosphere during the winter, ranging from 7 to 12 g CO2 -C m,2 season,1 being highest in the wet tundra. The period during the growing season when mesic tundra switch from being a CO2 source to a CO2 sink was increased by 2 weeks because of warming and increases in GEP. Warming during the summer stimulated dry tundra GEP more than Re and thus, NEE was consistently greater under warmed as opposed to ambient temperatures. In mesic tundra, warming stimulated GEP with no effect on Re increasing NEE by ,10%, especially in the first half of the summer. During the ,70 days growing season (mid-June,mid-August), the dry and wet tundra ecosystems were net CO2 -C sinks (30 and 67 g C m,2 season,1, respectively) and the mesic ecosystem was a net C source (58 g C m,2 season,1) to the atmosphere under ambient temperature conditions, due in part to unusual glacier melt water flooding that occurred in the mesic tundra. Experimental warming during the growing season increased net C uptake by ,12% in dry tundra, but reduced net C uptake by ,20% in wet tundra primarily because of greater rates of Re as opposed to lower rates of GEP. Mesic tundra responded to long-term warming with ,30% increase in GEP with almost no change in Re reducing this tundra type to a slight C source (17 g C m,2 season,1). Warming caused LCID of Dryas integrafolia plants to be higher in dry tundra and lower in Salix arctic plants in mesic and wet tundra. Our findings indicate that: (1) High Arctic ecosystems, which occur in similar mesoclimates, have different net CO2 exchange rates with the atmosphere; (2) long-term warming can increase the net CO2 exchange of High Arctic tundra by stimulating GEP, but it can also reduce net CO2 exchange in some tundra types during the summer by stimulating Re to a greater degree than stimulating GEP; (3) after 9 years of experimental warming, increases in soil carbon and nitrogen are detectable, in part, because of increases in deciduous shrub cover, biomass, and leaf litter inputs; (4) dry tundra increases in GEP, in response to long-term warming, is reflected in D. integrifolia LCID; and (5) the differential carbon exchange responses of dry, mesic, and wet tundra to similar warming magnitudes appear to depend, in part, on the hydrologic (soil water) conditions. Annual net ecosystem CO2 -C exchange rates ranged from losses of 64 g C m,2 yr,1 to gains of 55 g C m,2 yr,1. These magnitudes of positive NEE are close to the estimates of NPP for these tundra types in Alexandra Fiord and in other High Arctic locations based on destructive harvests. [source] Designing supercritical carbon dioxide extraction of rice bran oil that contain oryzanols using response surface methodologyJOURNAL OF SEPARATION SCIENCE, JSS, Issue 8 2008Chih-Hung Wang Abstract This study examines the supercritical carbon dioxide (SC-CO2) extraction of oryzanols contained rice bran oil from powdered rice bran. The extraction efficiencies and concentration factors of oryzanols, free fatty acids and triglycerides in the SC-CO2 extracts were determined. With top-flow type SC-CO2 extraction the total oil yield was 18.1% and the extraction efficiencies of oryzanols and triglycerides were 88.5 and 91.3% respectively, when 2750 g CO2 was consumed during the extraction of 35 g rice bran powder. The concentration factors of oryzanols and triglycerides in SC-CO2 -extracted oil were higher than in the Soxhlet n -hexane extracted oil. SC-CO2 extractions indicated that pressure can be used more effectively than temperature to enhance the extraction efficiency and concentration factor of oryzanols. A two-factor central composite scheme of response surface methodology was employed to determine the optimal pressure (300 bar) and temperature (313 K) for increasing the concentration of oryzanols in the SC-CO2 extracted oil. [source] The contribution of stone cover to biological activity in the Negev desert, IsraelLAND DEGRADATION AND DEVELOPMENT, Issue 1 2001I. Lahav (Lavian) Abstract Ancient valley agriculture in the northern Negev highlands was based on the principle of directed collection of water and eroded material from the slopes and their consequent flow towards the valleys. The stones on these slopes were therefore removed and/or collected into piles known as ,grape mounds'. The aim of this study was to understand the contribution of stone cover and slope-facing to biological activity in soil. Soil samples from a depth of 0,5,mm from the soil surface were collected during the study period (December 1994,March 1996) from northern and southern hill slopes, from under limestones and between stones. Soil moisture, organic matter, chlorophyll-a and soil respiration were determined. The results obtained in field and laboratory studies demonstrated differences between the northern and southern slopes. The stone cover on the northern slope made up 33 per cent and in the southern slope 23 per cent, stone size ranging from 15,50,cm2 and 15,35,cm2, respectively. Soil moisture content varied from 12 per cent in December 1994 on both slopes to one-quarter of the initial value during the dry period. Organic matter content reached a maximal level of 14 per cent and 16 per cent on the northern and southern slopes, respectively. Values of chlorophyll-a on both the northern and southern slopes were 0.38,,g,g,1 dry soil during the wet season, decreasing to 0.05,,g,g,1 dry soil during the dry period. Soil samples from under the stones on both slopes produced high levels of CO2, ranging between 50 and 100,,g CO2,g;,1 dry soil h,1, whereas in the control samples the levels ranged between 30 and 70,,g CO2,g,1 dry soil h,1. In conclusion, the stone cover apparently plays an important role in the maintenance of biological activity through its contribution to slope biotope stability. Copyright © 2001 John Wiley & Sons, Ltd. [source] Effects of hydrostatic pressure, agitation and CO2 stress on Phytophthora nicotianae zoospore survivalPEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 7 2010Monday O Ahonsi Abstract BACKGROUND:Phytophthora nicotianae Breda de Haan is a common pathogen of ornamental plants in recycled irrigation systems. In a previous study, annual vinca (Catharanthus roseus Don) inoculated with zoospore suspensions using a CO2 -pressurized sprayer had less foliage blight than plants inoculated using a hand sprayer. Here, the impact of hydrostatic pressure, agitation and aeration with CO2 on the survival of P. nicotianae zoospores was examined. RESULTS: Exposure of zoospores to 840 kPa hydrostatic pressure for 8 min or agitation at a mixing intensity (G) of 6483 s,1 for 4 min at 22,23 °C did not kill zoospores, but resulted in viable cysts. Motile and forcefully encysted zoospores of P. nicotianae were equally infectious on vinca or lupine (Lupinus polyphylus Lindl.). Bubbling CO2 into zoospore-infested water at 110.4 mL (0.2 g) min,1 for 5 min caused 81% reduction in the number of germinated zoospores. Pressure at 630 kPa (16.3 g CO2) or 70 kPa (3.85 g CO2) facilitated CO2 injection and shortened the zoospore inactivation time to 30 s. When air was bubbled through the suspension, germination was similar to the control. CONCLUSIONS: Exposure to CO2 killed P. nicotianae zoospores in water. Neither pressure nor agitation had an effect on zoospore viability or infectivity. Based on results of this study, the authors designed a recycling CO2 water treatment system that is currently under evaluation. Copyright © 2010 Society of Chemical Industry [source] Extraction of Poppy Seed Oil Using Supercritical CO2JOURNAL OF FOOD SCIENCE, Issue 2 2003B. Bozan ABSTRACT: Extraction of poppy seed oil with supercritical carbon dioxide (SC-CO2) was performed and the effect of extraction conditions on oil solubility and yield as well as oil composition was evaluated. Within the temperature (50 to 70 °C) and pressure (21 to 55 MPa) ranges studied, 55 MPa/70 °C gave the highest oil solubility (24.1 mg oil/g CO2) and oil yield (38.7 g oil/100g seed). Fatty acid composition of the oil obtained with SC-CO2 at 55 MPa/70 °C was similar to that of petroleum ether-extracted oil (p > 0.05) with linoleic acid making up 69.0 to 73.7% of fatty acids. Tocol content of the SC-CO2 -extracted oils varied from 22.37 to 33.35 mg/100 g oil, which was higher than that of petroleum ether-extracted oil (15.28 mg/100 g oil). Poppy seed oil may have potential in the rapidly growing specialty oil market. [source] | ||||||||||