CO2 Balance Research Articles

Inducible nitric oxide synthase inhibition improves intestinal microcirculatory oxygenation and CO2 balance during endotoxemia in pigs

We examined whether selective inhibition of inducible nitric oxide synthase (iNOS) promotes intestinal microvascular oxygenation (microPO2) and CO2 off-load after endotoxic shock. Prospective, controlled experimental study in a university animal research laboratory. 13 domestic pigs. After baseline measurements shock was induced by 1 microg kg-1 h-1 endotoxin until mean arterial pressure fell below 60 mmHg. After 30 min in shock the animals were resuscitated with either fluid alone (control, n=6) or fluid and the iNOS inhibitor N-[3-(aminomethyl)benzyl]acetamidine hydrochloride (1400W, n=7). As final experimental intervention all animals received the nonselective NOS inhibitor L-NAME. Systemic and regional hemodynamic and oxygenation parameters were measured at baseline, during endotoxemia and shock, hourly for 3 h of 1400W therapy, and 30 min after the final L-NAME administration. microPO2 was assessed by the Pd-porphyrin phosphorescence technique, and the arterial to intestinal PCO2 gap was determined by air tonometry. Endotoxemia and shock resulted in a decrease in ileal mucosal and serosal microPO2 and a rise in PCO2 gap. The combination of 1400W and fluid resuscitation, but not fluid alone, normalized both the serosal microPO2 and the intestinal PCO2 gap. Administration of L-NAME decreased cardiac output and oxygen delivery and intestinal microPO2 and blood flow in both groups. Partial blockade of NO production by 1400W increased serosal microvascular oxygenation and decreased the intestinal CO2 gap. This findings are consistent with the idea that 1400W corrects pathological flow distribution and regional dysoxia within the intestinal wall following endotoxic shock.

Evidence for Paleoproterozoic cap carbonates in North America

The early Paleoproterozoic Snowy Pass Supergroup of the Medicine Bow Mountains and Sierra Madre, Wyoming, USA and Huronian Supergroup, Ontario, Canada were deposited along the present-day southern flank of the Wyoming and Superior cratons. Whereas three discrete levels of glacial diamictite are developed in both successions, carbonate strata are known only directly above the middle diamictite (Vagner and Bottle Creek formations in Medicine Bow Mountains and Sierra Madre, respectively, and Espanola Formation in southern Ontario) in these thick correlative siliciclastics-dominated strata. The carbonates from each succession record negative δ 13C values (−4.0 to −0.8‰, V-PDB) and attenuated carbon isotopic difference between organic and inorganic phases. Oxygen in carbonates is strongly depleted in 18O suggesting exchange with hot fluids, which is consistent with pervasive recrystallization of carbonates and remobilization of elements. However, the stratigraphic coherence of carbon isotopic compositions and the general lack of correlation between δ 13C and either δ 18O values or trace element concentrations supports a primary origin for 13C-depleted carbonates, which are interpreted here to reflect anomalous oceanic compositions. The intimate association of thick carbonate units containing abundant carbonate debris flows with immediately underlying glacial strata indicates that chemical precipitation resulted from a rapid flux of carbonate alkalinity onto ocean margins during post-glacial transgression. Although these early Paleoproterozoic carbonates are similar to Neoproterozoic ‘cap dolomites’ in stratigraphic position and carbon isotopic compositions, the older post-glacial accumulations begin with limestone and lack many of the sedimentary structures typical of Neoproterozoic deposits. Furthermore, it is not understood why carbonates only occur above the middle of the three glacial horizons whereas these deposits are ubiquitous above Neoproterozoic diamictites. The differences might reflect lower overall carbonate saturation in early Paleoproterozoic oceans which contrasts sharply with Archean and later Paleoproterozoic intervals and higher siliciclastic inputs in rift environments, which shut down carbonate deposition. Geological and geochemical indicators suggest a stepwise increase in atmospheric oxygen across the Paleoproterozoic glacial epoch. The tempo and mode of atmospheric oxygen rise has significant consequences for the abundance of the important greenhouse gases CH 4 and CO 2 and hence for oceanic acidity. If we accept that atmospheric oxidation of methane to carbon dioxide resulted in each of the three discrete glaciations, it implies that atmospheric CH 4 remained high throughout the interval and that pulsed oxidation events, plausibly linked to higher primary productivity and lower hydrothermal activity, led to surface refrigeration. If correct, the unique presence of cap carbonate above the middle Paleoproterozoic diamictite may reflect an appropriate balance of CO 2 and CH 4 sufficient to provide enough alkalinity to seawater through silicate weathering, but not so high that carbonate preservation would be inhibited by enhanced acidity.

Formaldehyde and acetaldehyde exchange during leaf development of the Amazonian deciduous tree species Hymenaea courbaril

Abstract The effect of leaf age on the formaldehyde (HCHO) and acetaldehyde (CH3CHO) exchange pattern of the deciduous Amazonian tree species Hymenaea courbaril was investigated under field conditions. Branch enclosure measurements on senescent, young, and mature leaves showed that leaf development had a pronounced impact on the aldehyde exchange behavior with respect to both the direction and the magnitude of the exchange. The emission activity of senescent leaves was associated with a negative CO2 balance, even during daytime, indicative of a catabolic metabolism and decomposition processes leading to an increased aldehyde production within the leaf. The low exchange rates observed in young leaves were attributed to low stomatal conductance, while in mature leaves stomatal conductance and metabolic activities allowed efficient uptake. Within each leaf class the diurnal variations in the exchange of both aldehyde compounds were found to be mainly dependent on the respective ambient air concentrations. High ambient air concentrations resulted in decreased emission rates of senescent leaves and in enhanced uptake in young and mature leaves. CH3CHO compensation points decreased from 1.8 to 1.1 ppb with leaf maturation. We provide evidence that leaf-age-dependent variations in the stomatal conductance can account for the major share of differences in the CH3CHO deposition velocity. The results indicate that leaf surfaces of young and mature leaves may represent an effective additional non-stomatal sink for atmospheric aldehydes.

Seasonal sea-surface carbon dioxide in the Azores area

The seasonal evolution of total inorganic carbon and CO 2 air–sea fluxes in the Eastern North Atlantic Subtropical Gyre (Azores area) was investigated by means of studying a data set from 10 cruises covering a seasonal cycle. Monthly CO 2 fugacity was modelled as a function of surface temperature and month for 1998. So, the seasonal cycle of CO 2 and its air–sea fluxes were obtained using monthly average surface data in the area. Over the year, the Azores area (2.25·10 12 m 2) acts as a weak net sink of CO 2 (0.38 mmol m −2 day −1). From December to May, the zone is a rather strong sink for CO 2 (10.3 mmol m −2 day −1), while between June and November, it behaves as a CO 2 source (9.9 mmol m −2 day −1), August presents the highest outgassing (3.88 mmol m −2 day −1). Moreover, a box budget was established to evaluate the relative contribution of the physical and biological processes affecting the seasonal CO 2 variability in the mixed layer of the Azores area. The most important contributor to the average mass balance of CO 2 was the mixing with the lower layer (7.8 mmol m −2 day −1) and biological activity (−8.9 mmol m −2 day −1). Conversely, air–sea exchange (0.17 mmol m −2 day −1) and advection (1.7 mmol m −2 day −1) contribute with a very small input. There is a strong coupling between biological activity, advection, and mixing in the mixed layer depth. The biological activity is supported by mixing and advection that provide CO 2 and nutrients to the mixed layer, so we combine the three processes in only one term (ΔC AMB) that represents the net biology production in the water column, and re-evaluated the CO 2 mass balance to discriminate the importance of the physical and biological contributions. The effect of temperature, wind, and net biological process contribute in 42%, 12%, and 46%, respectively, to the explained variance of total CO 2 mass balance in the upper layer.

327 シベリア森林火災のモデリングと将来の炭酸ガス収支に対する火災影響(環境数値シミュレーション,大気・水保全技術)

Forest in Siberia plays important role for absorbing carbon dioxide. However, resent increase in forest fires, due to both human negligence and global warming, appears to cause significant damage on the forest. The present research tries to establish simulation model, which enables to predict forest fire effect over thousand years, and to evaluate the effects of forest fire on long term balance of CO_2 in Siberia. The result of the analysis shows that the major factor affecting on long-term forest area is the probability of fire extension and the number of fires in a year would not make apparent difference in the forest area due to feedback mechanism of fire sizes. The prediction was confirmed by the analysis of the remote sensing data. The paper shows the substantial danger of global warming effect on long-term forest area, whereas human negligence effect may be small.

COMPARISON OF DIRECT VS. INDIRECT VENTILATION RATE DETERMINATIONS IN LAYER BARNS USING MANURE BELTS

Direct measurement of building ventilation rate in livestock housing is a formidable task due to uncontrollablevariations in fan and system performance that are caused by factors such as building static pressure, fan belt slippage, anddust accumulation on shutters and blades. Estimating building ventilation rate by an indirect method based on a CO2 balanceoffers a potentially viable alternative to direct measurement. The validity of the CO2 balance method depends on the validityof relationship between CO2 production inside the building and metabolic rate of the animals and the knowledge of CO2generation by the housing environment. Metabolic rates of modern laying hens have recently been quantified in intensivelarge-scale laboratory measurements. However, performance of the indirect method remains to be evaluated under fieldconditions. This article compares building ventilation rates obtained by direct measurement and by a CO2 balance. The testwas conducted at a commercial laying hen house that used manure belts with daily manure removal. The results indicate thatventilation rates estimated by the indirect method were not significantly different (P > 0.2) from those as determined by thedirect measurement when the averaging or integration time interval was 2 h or longer. Careful application of the indirectmethod could greatly improve the affordability and versatility of endeavors toward quantifying air emissions from confinedanimal housing.

Sensitivity of C Sequestration in Reintroduced Sphagnum to Water‐Level Variation in a Cutaway Peatland

Abstract The reintroduction of Sphagnum fragments has been found to be a promising method for restoring mire vegetation in a cutaway peatland. Although it is known that moisture controls Sphagnum photosynthesis, information concerning the sensitivity of carbon dynamics on water‐level variation is still scarce. In a 4‐year field experiment, we studied the carbon dynamics of reintroduced Sphagnum angustifolium material in a restored (rewetted) cutaway peatland. Cutaway peatland restored by Sphagnum reintroduction showed high sensitivity to variation in water level. Water level controlled both photosynthesis and respiration. Gross photosynthesis (PG) had a unimodal response to water‐level variation with optimum level at −12 cm. The range of water level for high PG (above 60% of the maximum light‐saturated PG) was between 22 and 1 cm below soil surface. Water level had a dual effect on total respiration. When the water level was below soil surface, peat respiration increased rapidly along the lowering water level until the respiration rate started to slow down at approximately −30 cm. Contrary to peat respiration, the response of Sphagnum respiration to water‐level variation resembled that of photosynthesis with an optimum at −12 cm. In optimal conditions, Sphagnum reintroduction turned the cutaway site from carbon source to a sink of 23 g C/m2 per season (mid‐May to the end of September). In dry conditions, lowered photosynthesis together with the higher peat respiration led to a net loss of 56 g C/m2. Although the water level above the optimum amplitude restricted CO2 fixation, a decrease in peat respiration led to a positive CO2 balance of 9 g C/m2.

Materials selection guidelines for membranes that remove CO 2 from gas mixtures

Membrane technology has been investigated for removing CO 2 from mixtures with light gases such as CH 4, N 2 and H 2, and optimal membranes with high CO 2 permeability and high CO 2/light gas selectivity are of great interest. This overview describes the material science approaches to achieve high CO 2 solubility and CO 2/light gas solubility selectivity by introducing polar groups in polymers. CO 2 solubility and CO 2/N 2 solubility selectivity in both liquid solvents and solid polymers containing a variety of polar groups are discussed. Optimum materials appear to have a solubility parameter of about 21.8 MPa 0.5 to achieve both high solubility and high solubility selectivity. However, the introduction of polar groups can decrease CO 2 diffusion coefficients and can make a material more size-selective, which is detrimental to, for example, CO 2/H 2 separation properties. So far, ether oxygens in ethylene oxide (EO) units appear to provide a good balance of CO 2 separation and permeation properties. One drawback of using pure poly(ethylene oxide) (PEO) is its strong tendency to crystallize. This report reviews strategies for incorporating high concentrations of EO units into polymers while suppressing crystallization. A simple model, based on free volume theory, is used to correlate a wide range of CO 2 permeability coefficients in PEO containing materials, and the results are satisfactory, particularly given the simplicity of the model. Crosslinked poly(ethylene glycol) acrylate (XLPEO) containing branches with methoxy end groups exhibit the highest CO 2 permeability (i.e. 570 Barrers) and highest CO 2/H 2 selectivity (i.e. 12) at 35 °C and infinite dilution among all PEO containing materials reported to date. Because such materials do not crystallize at typically accessible temperatures, CO 2/H 2 selectivity can be further improved by decreasing temperature. For example, at an upstream pressure of 4.4 atm, CO 2/H 2 pure gas selectivity reaches a value of 40 at −20 °C while maintaining a CO 2 permeability of 52 Barrers.

Green hydropower: a new assessment procedure for river management

AbstractHydropower is the most important renewable electricity source worldwide. It shows clear advantages for the global CO2 balance but creates serious ecological impacts on a local scale. As a consequence, concern for the conservation of natural river ecosystems is growing within society and more people are willing to pay extra for so‐called ‘green electricity’. The definition of ‘green’, however, is not straightforward and customers cannot directly examine the quality of electricity products. Therefore, credible certification of high ecological standards is essential for successful green electricity marketing.In this paper we introduce a new assessment procedure for evaluating environmentally compatible hydropower production. This so‐called ‘Green Hydro’ concept was developed in the context of a multidisciplinary case study on a 400 MW hydropower scheme in the Southern Alps of Switzerland. The concept guarantees both general standards for different schemes operating in different types of watersheds and flexibility for local particularities. We developed an environmental management matrix that considers basic criteria and eco‐investments and covers five environmental areas of concern (i.e. hydrological character, connectivity, morphology, landscape, and biological communities). The ecological perspective is complemented by five management domains (i.e. instream flow regimes, hydropeaking, reservoir and bedload management, and power plant structures). Applying assessment and modelling tools for the Green Hydro procedure showed that dynamic habitat models allowed quantification of the effects of different instream flow regulations at morphologically distinct sites. In this case, morphological restoration could be more beneficial than increasing the minimum flow.The first experience with the Green Hydro certification is encouraging. So far, 13 facilities have successfully passed the certification procedure. They produce a total of 186 GWh green electricity per year, which is sufficient for the supply of almost 40 000 households in Switzerland. Copyright © 2004 John Wiley & Sons, Ltd.

Die Rolle der Wälder im Protokoll von Kyoto – Abschätzung ihres Kohlenstoffvorrates gestützt auf Satellitendaten | The role of the forest in the Kyoto Protocol – Estimation of carbon reserve using satellite data

Switzerland became a signatory to the climate convention in 1993 and ratified the Kyoto Protocol in 2003. This means that in the period from 2008 to 2012 the country is committed to reducing its greenhouse gas emissions by 8%compared to 1990. Switzerland has to deposit its annual greenhouse gas inventory with the Climate Convention Secretariat. This also includes accounts of the CO2 of the forest. Within the framework of its Data User Programme the European Space Agency (ESA) has offered to test the use of its Remote Collected Data System for forest reporting for the Kyoto Protocol. By participating in this project Switzerland aims to examine in how far it can automate its annual forest CO2 balance using objective data taken directly from the satellite.

Efficient energy systems with CO2 capture and storage from renewable biomass in pulp and paper mills

This paper investigates the impact of combining CO2 capture and storage with alternative systems for biomass-based combined heat and power production (CHP) in Kraft pulp and paper mills. We compare heat, power, and CO2 balances of systems with alternative configurations of the CHP and CO2-capture systems. Because the captured CO2 comes from renewable biomass, the studied systems yield negative CO2 emissions. It is shown that pulp mills and integrated pulp and paper mills have the potential to become net exporters of biomass-based electricity while at the same time removing CO2 from the atmosphere on a net basis. The study shows that that the overall best CO2 abatement is achieved when CO2 capture is carried out within a biomass integrated gasifier with combined cycle where the syngas undergoes a CO-shift reaction. This configuration combines efficient energy conversion with a high CO2 capture efficiency. Furthermore, cost curves are constructed, which show how the cost of CO2 capture and storage in pulp and paper mills depends on system configuration and the CO2 transportation distance.

CO2 and water vapor exchange of a larch forest in northern Japan

In the northern part of East Asia, forests dominated by larch are extensively distributed and probably play an important role in the global carbon cycle. However, a knowledge of the CO2 balance of larch forests based on long-term flux measurements is very restricted in East Asia. Thus, a long-term flux measurement has been started in 2000 at a larch plantation on a flat terrain in Hokkaido, Japan to obtain more information on the CO2 and energy balances of larch forests. From September 2000 to August 2001 the net ecosystem CO2 exchange (NEE) changed seasonally in accordance with the annual cycles of phenology and climate. NEE was negative for six months of the growing season, May—September; the larch ecosystem was a carbon sink with a peak intensity of –0.38 mol m−2 d−1 for this period. In the leafless season from November to April the forest ecosystem was a carbon source with an intensity ranging between 0 and 0.05 mol m−2 d−1. Annual NEE from September 2000 to August 2001 was −24.4 to −32.4 mol m−2 yr−1 (=−293 to −389 gC m−2 yr−1); this value is compatible with those reported from other temperate forests. Annual evapotranspiration for the same period was 367 mm, which was only 29% of annual precipitation.

Minor Changes in Vegetation and Carbon Gas Balance in a Boreal Mire under a Raised CO2 or NH4NO3 Supply

Increasing concentrations of carbon dioxide (CO2) in the atmosphere or continuous nitrogen (N) deposition might alter the carbon (C) cycle in boreal mires and thus have significant impacts on the development of climate change. The atmospheric impact of the C cycle in mires is twofold: C accumulation attenuates and CH4 release strengthens the natural greenhouse effect. We studied the effects of an increased supply of CO2 or NH4NO3 on the vegetation and annual CO2 exchange in lawns of a boreal oligotrophic mire in eastern Finland over a 2-year period. Ten study plots were enclosed with mini-FACE (Free Air Carbon Dioxide Enrichment) rings. Five plots were vented with CO2-enriched air (target 560 ppmv), while their controls were vented with ambient air; five plots were sprayed with NH4NO3, corresponding to a cumulative addition of 3gNm 2 a 1 , while their controls were sprayed with distilled water only. A raised NH4NO3 supply seemed to affect the composition of the moss layer. Raised CO2 did not affect the vegetation, but gross photosynthesis increased significantly. The change in net CO2 exchange depended on the annual weather conditions. Our results suggest that C accumulation may increase in wet years and compensate for the warming effect caused by the increase in CH4 release from this mire. In contrast, a relatively dry and warm growing period favors decomposition and can even make the CO2 balance negative. Along with the increased CH4 release under raised CO2, the decreased C accumulation then increases the radiative forcing of boreal mires.

Annual CO2 balance of a subarctic fen in northern Europe: Importance of the wintertime efflux

The annual balance of CO2 was measured on a subarctic flark fen located in northern Finland (69°08′N, 27°17′E). Measurements were conducted using the micrometeorological eddy covariance method during the period from April 1998 to April 1999. Special emphasis was put on the importance of the wintertime CO2 balance as a component of the annual budget. The CO2 fluxes observed during the winter were relatively small (0.0055 mg CO2 m−2 s−1), but due to the long duration of the snow cover period, they play an important role in the annual balance of CO2. The efflux during the coldest periods, when soil surface temperatures fell below −10 °C, was enabled by markedly higher peat temperatures (close to 0 °C) in deeper layers. The typical nighttime respiration observed in summer was 0.10 mg CO2 m−2 s−1. The net photosynthesis had a typical daytime peak value of about −0.20 mg CO2 m−2 s−1 in July. Corresponding with the instantaneous CO2 fluxes, the highest daily sink balances of about −9 g CO2 m−2 d−1 were observed in July, while the highest daily respiration balances of about 2.5 g CO2 m−2 d−1 were observed before and after the sink period. The CO2 balance for the winter period (105 g CO2 m−2) was greater than the absolute value of the total annual balance (−68 g CO2 m−2), which shows the importance of the wintertime efflux. After taking into account estimates for CH4 efflux and carbon leaching, an annual carbon balance of −7 ± 5 g C m−2 was obtained for the fen.

Ecological significance of net photosynthesis activation by water vapour uptake in Ramalina capitata from rain-protected habitats in central Spain

The reactivation of net photosynthesis and dark respiration from water vapour and from liquid water in the lichen Ramalina capitata var. protecta (H. Magn.) Nimis from sheltered habitats in Central Spain was investigated. CO 2 gas-exchange response and thallus water content were measured in the laboratory as dry thalli were allowed to equilibrate by water vapour uptake under different relative humidities, and as saturated thalli dried. Water content of thalli from different habitats was also measured in the field during rainfall. The results show that the lichen is very efficient in using water vapour from the air for photosynthesis. Net photosynthetic rates were measured at very low water potentials (up to −26·9 Megapascal) with water contents of the thalli below 30% dry weight. Maximum net photosynthetic rates measured after water vapour uptake were in some cases similar to those obtained after hydration by liquid water, while respiration rates were always lower after water vapour uptake, indicating a relatively larger activation of the photobiont. Moreover, photosynthetic rates at thallus water contents below 60% dry weight were higher when hydration was achieved through water vapour uptake than with liquid water. Field measurements had shown that this lichen reached water contents through water vapour absorption of 40% dry weight that would allow a positive balance of CO 2 uptake. Possible ecological implications of differences in photosynthetic activation depending on the water source are discussed in terms of the carbon gain under natural conditions of this ombrophobous lichen.

Stable carbon isotope constraints on mixing and mass balance of CO 2 in an urban atmosphere: Dallas metropolitan area, Texas, USA

The concentrations and δ 13C values of atmospheric CO 2 were measured in ∼150 air samples collected at 8 sites in the Dallas metropolitan area over the period August 1998 to December 1999. Measured concentrations (C) of atmospheric CO 2 ranged from 369 to 475 ppm, while the δ 13C values ranged from –12.0 to –8.1‰. These values contrast with a “global” concentration at the time of this study of approximately 367 ppm and a corresponding δ 13C value of about –8.0‰. δ 13C was linearly correlated with 1/C for samples collected at heights of ∼2 m at 3 sites adjacent to streets with significant automobile traffic. Extrapolation of this two-component mixing line to 1/C=0 yielded a δ 13C value of about –27‰ for the CO 2 input—i.e., the same as that of gasoline. A simple box model, incorporating photosynthesis, respiration, and anthropogenic addition of CO 2, indicates that differences between downwind and upwind concentration-weighted δ 13C values ( Δ[ C ∗ δ 13C]) of atmospheric CO 2 may be linearly correlated with downwind and upwind differences in concentration ( C d ∗− C u ∗ ), where C ∗ is reported as mol/m 3. The model predicts that measurable effects of photosynthetic withdrawal of atmospheric CO 2 are manifested by data arrays with slopes more positive than about –16. This effect of photosynthesis is evident in a linear array of “warm weather”, Dallas atmospheric CO 2 data (slope of –12.7‰). Collectively, the data for all 8 sites exhibited considerable scatter about binary mixing lines that depict the addition of CO 2 from combustion of natural gas and gasoline. However, when model slopes ( m) were calculated for binary mixing between a “background” atmospheric CO 2 and each individual sample, it was found that, in general, m increases with decreasing temperature. The effects of photosynthesis and respiration complicate this relationship, but the overall pattern suggests that, as temperature decreases, the proportion of anthropogenic CO 2 derived from combustion of natural gas increases. This increase appears to reflect increased use of natural gas for home heating, etc., in cooler weather. Therefore, seasonally changing patterns of fossil fuel use are detectable in the atmospheric CO 2 of this urban environment.

High-Performance Microtiter Plates for Immunosorbent Assays Made of Renewable Resources: Polylactic Acid Biopolymer as a Substitute for Synthetic Polystyrene

Most immunoassays are based on microtiter plates with conventional polystyrene (PS) as a solid support. PS is produced from crude oil. The production of PS plates consumes several hundred thousands tons of valuable raw material of limited supply. Also, disposing of PS plates by incineration produces a complex mixture of pollutants including dioxins and polycyclic aromatic hydrocarbons (1), and it adds excess CO2 to the atmosphere. In contrast, biopolymers such as polylactic acids (PLAs) are produced from renewable resources; they are biodegradable and their CO2 balance is neutral. PLA-based polymers have successfully replaced synthetic polymers in several applications, including some recent applications in immunology (2)(3). For the development of a PLA formula suitable as a matrix for immunoassays, the physical properties and surface characteristics of the polymer had to be improved for the present study. Surface characteristics are affected by factors such as monomer content, the nature and concentration of various additives, and molding and releasing conditions. Moreover, lot-to-lot reproducibility is affected by industrial fermentation and extraction procedures. For this study, the injection-molding process commonly used for PS was adapted to the PLA polymer to produce an experimental batch of 96-well microtiter plates from suitable PLA formulations. The performance of these plates in an ELISA was compared with conventional commercial PS plates. We used recombinant measles virus hemagglutinin protein (H-ELISA) as antigen for the detection of measles-specific IgG (4)(5)(6). We analyzed a panel of 426 human sera using 96-well prototype microtiter plates made of PLA. The procedure was applied essentially as described (5). All study participants or their parents gave informed consent. Results were compared with those obtained with the same antigen and commercial PS Maxisorp microtiter plates (NUNC). Statistical analysis of data was performed with SigmaStat software (Jandel Scientific). A z …

On eco-efficiency and sustainable development in Estonia

The basic idea of sustainable development is a firm understanding that all resources, renewable as well as non-renewable, are limited. Human activities should not exceed the buffering capacity of the earth's ecosystems and the replenishment potential of material cycles. Use of non-renewable, mainly mineral, resources should be kept at the minimum possible level, postponing the depletion of resources as far as possible. Concepts of environmental space and dematerialisation lie at the foundation of the practical launching of sustainable development. Analysis of regional sustainability and ecological efficiency of energy production, the balance of CO2, water, etc. were analysed for Estonia and Ida-Virumaa, the north-eastern region of the country. The analysis carried out should be considered as a first step in the development and implementation of a national "green" accounting system and environmental tax system based on the concept of environmental space.

Comparative ecosystem–atmosphere exchange of energy and mass in a European Russian and a central Siberian bog II. Interseasonal and interannual variability of CO2 fluxes

Net ecosystem–atmosphere exchange of CO2 (NEE) was measured in two boreal bogs during the snow-free periods of 1998, 1999 and 2000. The two sites were located in European Russia (Fyodorovskoye), and in central Siberia (Zotino). Climate at both sites was generally continental but with more extreme summer–winter gradients in temperature at the more eastern site Zotino. The snow-free period in Fyodorovskoye exceeded the snow-free period at Zotino by several weeks. Marked seasonal and interannual differences in NEE were observed at both locations, with contrasting rates and patterns. Amongst the most important contrasts were: (1) Ecosystem respiration at a reference soil temperature was higher at Fyodorovskoye than at Zotino. (2) The diurnal amplitude of summer NEE was larger at Fyodorovskoye than at Zotino. (3) There was a modest tendency for maximum 24 h NEE during average rainfall years to be more negative at Zotino (−0.17 versus −0.15 mol m−2 d−1), suggesting a higher productivity during the summer months. (4) Cumulative net uptake of CO2 during the snow-free period was strongly related to climatic differences between years. In Zotino the interannual variability in climate, and also in the CO2 balance during the snow-free period, was small. However, at Fyodorovskoye the bog was a significant carbon sink in one season and a substantial source for CO2-C in the next, which was below-average dry. Total snow-free uptake and annual estimates of net CO2-C uptake are discussed, including associated uncertainties.

The summer metabolic balance in the epilimnion of southeastern Quebec lakes

On the basis of data collected in Quebec lakes, del Giorgio and Peters (1994) and Carignan et al. (2000) have come to opposite conclusions regarding the metabolic balance between heterotrophy and autotrophy in lakes in general. In the present study, epilimnetic oxygen and carbon dioxide saturation was measured in 33 lakes from the St. Lawrence Lowlands region of Quebec to examine the extent of epilimnetic net heterotrophy (i.e., O2:CO2 balance) in lakes of different characteristics. We found that ~75% of the lakes were undersaturated with oxygen and supersaturated with CO2. There was a strong negative relationship between the departures of O2 and CO2 from saturation. What has not been noted elsewhere is that oxygen concentrations were negatively related to dissolved organic carbon (DOC) concentration, and, therefore, metabolic gas balances could be predicted from DOC; a value between 4 and 6 mg L−1 DOC corresponds to metabolic equilibrium. Because most of the lakes in del Giorgio and Peters (1994) had DOC concentrations above this threshold and most lakes in Carignan et al. (2000) were below, their apparently contradictory conclusions can be reconciled within a larger general theory. Contrary to studies elsewhere, however, we found that the degree of oxygen undersaturation increased with lake trophic status, expressed either as total phosphorus or nitrogen concentrations.