Atmospheric O2 Concentrations Research Articles

Spatial and temporal variations in atmospheric VOCs, NO2, SO2, and O3 concentrations at a heavily industrialized region in Western Turkey, and assessment of the carcinogenic risk levels of benzene

Ambient concentrations of volatile organic compounds (VOCs), nitrogen dioxide (NO2), sulphur dioxide (SO2) and ground-level ozone (O3) were measured at 55 locations around a densely populated industrial zone, hosting a petrochemical complex (Petkim), a petroleum refinery (Tupras), ship-dismantling facilities, several iron and steel plants, and a gas-fired power plant. Five passive sampling campaigns were performed covering summer and winter seasons of 2005 and 2007. Elevated concentrations of VOCs, NO2 and SO2 around the refinery, petrochemical complex and roads indicated that industrial activities and vehicular emissions are the main sources of these pollutants in the region. Ozone concentrations were low at the industrial zone and settlement areas, but high in rural stations downwind from these sources due to NO distillation. The United States Environmental Protection Agency's positive matrix factorization receptor model (EPA PMF) was employed to apportion ambient concentrations of VOCs into six factors, which were associated with emissions sources. Traffic was found to be highest contributor to measured ∑VOCs concentrations, followed by the Petkim and Tupras.Median cancer risk due to benzene inhalation calculated using a Monte Carlo simulation was approximately 4 per-one-million population, which exceeded the U.S. EPA benchmark of 1 per one million. Petkim, Tupras and traffic emissions were the major sources of cancer risk due to benzene inhalation in the Aliaga airshed. Relative contributions of these two source groups changes significantly from one location to another, demonstrating the limitation of determining source contributions and calculating health risk using data from one or two permanent stations in an industrial area.

Simulation research on the natural degradation process of PBDEs in soil polluted by e-waste under increased concentrations of atmospheric O3

There have been increased concerns regarding the effect of polybrominated diphenyl ethers (PBDEs) on the environment. These compounds are widely utilized by the electronics industry and also function as fire retardants. More data on the basic characteristics of PBDEs are needed to better understand and used to describe their environmental fate. The aim of this study was to investigate the degradation of BDE-209 with different degrees of bromination under changes in the atmospheric environment. BDE-209 was able to be removed quickly due to the strong oxidizing ability of ozone in the atmosphere environment. Less-brominated BDEs, ranging from BDE-28 to BDE-183, were formed progressively, and the reaction of ozone gradually occupied the main position along with an increase in ozone flow time. Degradation reaction rates of PBDEs increased with increasing ozone concentration but decreased with increasing soil depth. Under UV-irradiation, BDE-209 was quickly transformed into less-brominated BDEs and the photodegradation reactions were faster than solar irradiation. The conditions of high ground temperature in the summer and alkaline soil were both contributors to the degradation of PBDEs. These results could facilitate the improvement of waste treatment designs and lead to better predictions of the outcome of PBDEs in the environment.

Changing oxygen concentration around the rootstock alters spear elongation and sprouting of white asparagus

We investigated the effects of manipulating the atmospheric oxygen (O2) concentration around white asparagus rootstocks planted in pots to evaluate the applicability of this technique for growth regulation in white asparagus production. The O2 concentrations around the pots were adjusted to 5%, 10%, 20%, 40%, 60%, and 80%, and plants were exposed to these conditions over a 38-d period. We found that the time of both initial sprouting (i.e., when the length of the first emerging spears reached >30mm) and harvesting were delayed when the O2 concentration around the pots was 5%; moreover, decreases in the soluble solids contents (SSCs) of the storage roots were inhibited at 5% O2 relative to the control (20% O2). These delays were likely due to a hypoxic effect, which inhibits the metabolism of some respiratory substrates such as sugars and/or organic acids. Under the 5% O2 treatment, the O2 concentration during the gaseous phase of the soil in the pot was estimated to be 12.4–14.4%; therefore, sprouting should be delayed when the O2 concentration around the roots is <15%. Our results also showed that the rate of spear elongation decreased when the O2 concentration around the spears was within the range of 60–80%. Considering that the 40% O2 concentration did not affect the rate of spear elongation, it appears that the threshold for this phenomenon is an O2 concentration of 40–60%. When the rootstocks grown under each O2 treatment were replanted and cultured under normal atmospheric conditions for 25d, no significant differences were found in growth and yield ability, such as the time of initial harvesting, number of harvested spears, yield, and spear weight. Therefore, the effects of different atmospheric O2 concentrations did not continue after cessation of the experimental treatments. Our results suggest that controlling the O2 concentration around rootstocks may be a new method for the growth regulation of white asparagus. We also expect that the new method can be applied in a closed cultivation system as well as in a plant factory.

Elevated O₃ enhances the attraction of whitefly-infested tomato plants to Encarsia formosa.

We experimentally examined the effects of elevated O3 and whitefly herbivory on tomato volatiles, feeding and oviposition preferences of whiteflies and behavioural responses of Encarsia formosa to these emissions on two tomato genotypes, a wild-type (Wt) and a jasmonic acid (JA) defence-enhanced genotype (JA-OE, 35S). The O3 level and whitefly herbivory significantly increased the total amount of volatile organic compounds (VOCs), monoterpenes, green leaf volatiles (GLVs), and aldehyde volatiles produced by tomato plants. The 35S plants released higher amount of total VOCs and monoterpene volatiles than Wt plants under O3+herbivory treatments. The feeding and oviposition bioassays showed that control plants were preferred by adult whiteflies whereas the 35S plants were not preferred by whiteflies. In the Y-tube tests, O3+herbivory treatment genotypes were preferred by adult E. Formosa. The 35S plants were preferred by adult E. formosa under O3, herbivory and O3+herbivory treatments. Our results demonstrated that elevated O3 and whitefly herbivory significantly increased tomato volatiles, which attracted E. formosa and reduced whitefly feeding. The 35S plants had a higher resistance to B. tabaci than Wt plant. Such changes suggest that the direct and indirect defences of resistant genotypes, such as 35S, could strengthen as the atmospheric O3 concentration increases.

Ozone pollution influences soil carbon and nitrogen sequestration and aggregate composition in paddy soils

Background and aims Much attention has focused on the effects of tropospheric ozone (O3) on terrestrial ecosystems and plant growth. Since O3 pollution is currently an issue in China and many parts of the world, understanding the effects of elevated O3 on soil carbon (C) and nitrogen (N) sequestration is essential for efforts to predict C and N cycles in terrestrial ecosystems under predicted increases in O3. Thus the main objective of this study was to determine whether an increases in atmospheric O3 concentration influenced soil organic C (SOC) and N sequestration.

O2constraints from Paleoproterozoic detrital pyrite and uraninite

Redox-sensitive detrital grains such as pyrite and uraninite in sedimentary successions provide one of the most conspicuous geological clues to a different composition of the Archean and early Paleoproterozoic atmosphere. Today, these minerals are rapidly chemically weathered within short transport distances. Prior to the rise of oxygen, low O2 concentrations allowed their survival in siliciclastic deposits with grain erosion tied only to physical transport processes. After the rise of oxygen, redox-sensitive detrital grains effectively vanish from the sedimentary record. To get a better understanding of the timing of this transition, we examined sandstones recorded in a scientifi c drill core from the South African 2.415 Ga Koegas Subgroup, a mixed siliciclastic and iron formation–bearing unit deposited on the western deltaic margin of the Kaapvaal craton in early Paleoproterozoic time. We observed detrital pyrite and uraninite grains throughout all investigated sandstone beds in the section, indicating the rise of oxygen is younger than 2.415 Ga. To better understand how observations of detrital pyrite and uraninite in sedimentary rocks can quantitatively constrain Earth surface redox conditions, we constructed a model of grain erosion from chemical weathering and physical abrasion to place an upper limit on ancient environmental O2 concentrations. Even conservative model calculations for deltaic depositional systems with suffi cient transport distances (approximately hundreds of kilometers) show that redox-sensitive detrital grains are remarkably sensitive to environmental O2 concentrations, and they constrain the Archean and early Paleoproterozoic atmosphere to have <3.2 × 10 –5 atm of molecular O2. These levels are lower than previously hypothesized for redox-sensitive detrital grains, but they are consistent with estimates made from other redox proxy data, including the anomalous fractionation of sulfur isotopes. The binary loss of detrital pyrite and uraninite from the sedimentary record coincident with the rise of oxygen indicates that atmospheric O2 concentrations rose substantially at this time and were never again suffi ciently low (<0.01 atm) to enable survival and preservation of these grains in short transport systems.

Diurnal variation of ozone flux over corn field in Northwestern Shandong Plain of China

High concentration ground-level ozone (O3) has adverse effects on plant growth and photosynthesis. Compared to the O3 concentration-based index, the O3 flux-based (especially stomatal O3 uptake) index has been considered the better criterion for assessing the impact of ozone on vegetation and ecosystems. This paper reports on a study of O3 flux using the eddy covariance technique over a corn field in the Northwestern Shandong Plain of China. Diurnal variation of atmospheric O3 concentration, deposition velocity and flux, and their relationships to environmental factors are analyzed. The results show that: (1) During the observation period (9 August-28 September, 2011), there was a strong diurnal variation of O3 concentration, with low (16.5 nL L−1) and high (60.1 nL L−1) O3 mean concentrations observed around 6:30 and 16:00, respectively. Mean O3 concentrations during daytime (6:00–18:00) and nighttime (18:00–6:00) were 39.8±23.1 and 20.7±14.1 nL L−1 (mean±std), respectively. The maximum observed concentration was 97.5 nL L−1. The concentration was mainly affected by solar radiation and air temperature. (2) Whether daytime or nighttime, ground-level O3 flux is always downward. The diurnal course of mean deposition velocity was divided into 4 phases: a low and stable process during nighttime, fast increasing in early morning, relatively large and steady changes around noon, and quickly decreasing in later afternoon. Daytime and nighttime mean deposition velocities were 0.29 and 0.09 cm s−1, respectively. The maximum deposition velocity was 0.81 cm s−1. The magnitude of deposition velocity was influenced by the corn growth period, and its diurnal variation was significantly correlated with global radiation and relative humidity. (3) O3 flux was affected by variations of both O3 concentration and deposition velocity, with mean O3 fluxes −317.7 and −70.2 ng m−2 s−1 during daytime and nighttime, respectively. There was strong correlation between O3 flux and CO2 flux or latent heat flux. By comparing the deposition velocities of daytime and nighttime, we infer that stomatal uptake was probably the main sink of ground-level O3.

Exposure of embryos to oxygen at low concentration in an oocyte donation program with cleavage stage transfer

Some studies performed in animals suggest that atmospheric O2 concentration could have a detrimental effect on embryo culture due to the generation of reactive oxygen species that could affect to embryo metabolism and gene expression. In clinical human IVF, embryos have traditionally been cultured under atmospheric oxygen concentration (20%) until the development of new incubators that allow culturing them in a low oxygen concentration (2-8%). The goal of this study is to compare the effect of embryo culture until day 3 of development in two different oxygen concentrations conditions.

Anoxia promotes gravitropic curvature in rice pulvini but inhibits it in wheat and oat pulvini

Gravitropic curvature of pulvini of wheat and oat stem segments gradually declined with decreasing atmospheric O2 concentration and was almost completely blocked under anoxia, whereas that of rice stem segments was enhanced under hypoxia and anoxia. Anoxia substantially increased the ethanol content in pulvini of gravistimulated stem segments in rice, wheat and oat, but the ethanol content showed no marked difference between rice pulvini and wheat and oat pulvini. The concentrations of exogenous ethanol and acetaldehyde required to inhibit the gravitropic curvature of pulvini were significantly higher in rice segments than in wheat and oat segments. However, in all three species, the concentrations of ethanol and acetaldehyde required to completely inhibit curvature were several-fold higher than the endogenous levels that accumulated in pulvini gravistimulated in N2. The pulvini of rice segments gravistimulated in N2 did not contain much more ATP than those of wheat or oat segments gravistimulated in N2. When applied unilaterally to the pulvini of vertically oriented stem segments incubated in N2, indole-3-acetic acid induced bending in rice stem segments but not in wheat and oat stem segments. Transference of graviresponsive pulvini of rice, as well as those of wheat and oat, from aerobic conditions to anaerobic conditions led to cessation of gravitropic curvature within several minutes, but subsequently only gravitropic curvature of anoxic rice pulvini was completely recovered within 2h. A large portion of this recovery was blocked by cordycepin, a transcription inhibitor. These results suggested that anoxia-induced expression of any gene or genes enables rice pulvini to respond to gravistimulation under anaerobic conditions, and that such a gene or genes might be unrelated to ethanol fermentation and ATP production in anaerobic conditions.

Mercury isotopes in a forested ecosystem: Implications for air‐surface exchange dynamics and the global mercury cycle

Forests mediate the biogeochemical cycling of mercury (Hg) between the atmosphere and terrestrial ecosystems; however, there remain many gaps in our understanding of these processes. Our objectives in this study were to characterize Hg isotopic composition within forests, and use natural abundance stable Hg isotopes to track sources and reveal mechanisms underlying the cycling of Hg. We quantified the stable Hg isotopic composition of foliage, forest floor, mineral soil, precipitation, and total gaseous mercury (THg(g)) in the atmosphere and in evasion from soil, in 10‐year‐old aspen forests at the Rhinelander FACE experiment in northeastern Wisconsin, USA. The effect of increased atmospheric CO2 and O3 concentrations on Hg isotopic composition was small relative to differences among forest ecosystem components. Precipitation samples had δ202Hg values of −0.74 to 0.06‰ and ∆199Hg values of 0.16 to 0.82‰. Atmospheric THg(g) had δ202Hg values of 0.48 to 0.93‰ and ∆199Hg values of −0.21 to −0.15‰. Uptake of THg(g) by foliage resulted in a large (−2.89‰) shift in δ202Hg values; foliage displayed δ202Hg values of −2.53 to −1.89‰ and ∆199Hg values of −0.37 to −0.23‰. Forest floor samples had δ202Hg values of −1.88 to −1.22‰ and ∆199Hg values of −0.22 to −0.14‰. Mercury isotopes distinguished geogenic sources of Hg and atmospheric derived sources of Hg in soil, and showed that precipitation Hg only accounted for ~16% of atmospheric Hg inputs. The isotopic composition of Hg evasion from the forest floor was similar to atmospheric THg(g); however, there were systematic differences in δ202Hg values and MIF of even isotopes (∆200Hg and ∆204Hg). Mercury evasion from the forest floor may have arisen from air‐surface exchange of atmospheric THg(g), but was not the emission of legacy Hg from soils, nor re‐emission of wet‐deposition. This implies that there was net atmospheric THg(g) deposition to the forest soils. Furthermore, MDF of Hg isotopes during foliar uptake and air‐surface exchange of atmospheric THg(g) resulted in the release of Hg with very positive δ202Hg values to the atmosphere, which is key information for modeling the isotopic balance of the global mercury cycle, and may indicate a shorter residence time than previously recognized for the atmospheric mercury pool.

Modelling 18O2 and 16O2 unidirectional fluxes in plants. IV: Role of conductance and laws of its regulation in C3 plants

Numerous studies focus on the measurement of conductances for CO2 transfer in plants and especially on their regulatory effects on photosynthesis. Measurement accuracy is strongly dependent on the model used and on the knowledge of the flow of photochemical energy generated by light in chloroplasts. The only accurate and precise method to quantify the linear electron flux (responsible for the production of reductive energy) is the direct measurement of O2 evolution, by 18O2 labelling and mass spectrometry. The sharing of this energy between the carboxylation (P) and the oxygenation of photorespiration (PR) depends on the plant specificity factor (Sp) and on the corresponding atmospheric concentrations of CO2 and O2 (André, 2013). The concept of plant specificity factor simplifies the equations of the model. It gives a new expression of the effect of the conductance (g) between atmosphere and chloroplasts. Its quantitative effect on photosynthesis is easy to understand because it intervenes in the ratio of the plant specificity factor (Sp) to the specificity of Rubisco (Sr). Using this ‘simple’ model with the data of 18O2 experiments, the calculation of conductance variations in response to CO2 and light was carried out.The good fitting of experimental data of O2 and CO2 exchanges confirms the validity of the simple model. The calculation of conductance variation during the increase of external CO2 concentration reveals a linear law of regulation between external and internal CO2 concentrations. During CO2 variations, the effects of g regulation tend to maintain a higher level of oxygenation (PR) in expense of a better carboxylation (P). Contrary to CO2, the variation of O2 creates a negative feedback effect compatible with a stabilization of atmospheric O2. The regulation of g amplifies this result. The effect of light in combination with CO2 is more complex. Below 800μmolquantam–2s–1 the ratio PR/P is maintained unchangeable in expense of carboxylation efficiency. Above that irradiance value, PR/P increases dramatically. It appears that the saturation curves of photosynthesis under high light could be simply due to the regulation by the conductance g and not by any biochemical or biophysical limitation. In conclusion, the regulatory effect of conductance operates in a way that it preserves the rate of photorespiration. This confirms a positive and protective role of photorespiration at the biochemical, whole plant and atmosphere levels. Since the effects of photorespiration are linked to the properties of Rubisco, they add new arguments for a co-evolution of plant and atmosphere, including the evolution of CO2 conductance.

Biogeochemistry and microbiology of microaerobic Fe(II) oxidation

Today high Fe(II) environments are relegated to oxic-anoxic habitats with opposing gradients of O2 and Fe(II); however, during the late Archaean and early Proterozoic eons, atmospheric O2 concentrations were much lower and aqueous Fe(II) concentrations were significantly higher. In current Fe(II)-rich environments, such as hydrothermal vents, mudflats, freshwater wetlands or the rhizosphere, rusty mat-like deposits are common. The presence of abundant biogenic microtubular or filamentous iron oxyhydroxides readily reveals the role of FeOB (iron-oxidizing bacteria) in iron mat formation. Cultivation and cultivation-independent techniques, confirm that FeOB are abundant in these mats. Despite remarkable similarities in morphological characteristics between marine and freshwater FeOB communities, the resident populations of FeOB are phylogenetically distinct, with marine populations related to the class Zetaproteobacteria, whereas freshwater populations are dominated by members of the Gallionallaceae, a family within the Betaproteobacteria. Little is known about the mechanism of how FeOB acquire electrons from Fe(II), although it is assumed that it involves electron transfer from the site of iron oxidation at the cell surface to the cytoplasmic membrane. Comparative genomics between freshwater and marine strains reveals few shared genes, except for a suite of genes that include a class of molybdopterin oxidoreductase that could be involved in iron oxidation via extracellular electron transport. Other genes are implicated as well, and the overall genomic analysis reveals a group of organisms exquisitely adapted for growth on iron.

Ecophysiological Responses of Northern Birch Forests to the Changing Atmospheric CO2 and O3 Concentrations

The effects on birch (Betula spp.) of elevated carbon dioxide (<TEX>$CO_2$</TEX>) and ozone (<TEX>$O_3$</TEX>), which are both increasing in the troposphere, are surveyed in detail based on the literature. Birches establish themselves in the open field after disturbances, and then become dominant trees in temperate or boreal forests. Ecophysiological approaches include the measurement of photosynthesis, biomass, growth, and survival of seedlings and trees. Elevated <TEX>$CO_2$</TEX> levels give rise to a net enhancement of the growth of birch trees, whereas high <TEX>$O_3$</TEX> generally reduces growth. Although the effects of the two are opposed, there is also an interactive effect. Basic physiological responses of the single genus Betula to <TEX>$CO_2$</TEX> and <TEX>$O_3$</TEX> are set out, and some data are summarized regarding ecological interactions between trees, or between trees and other organisms.

Seasonal changes in the daily emission rates of terpenes by Quercus ilex and the atmospheric concentrations of terpenes in the natural park of Montseny, NE Spain

We studied the daily patterns in the rates of terpene emissions by the montane holm oak, Quercus ilex, in three typical days of winter and three typical days of summer in Montseny, a natural park near Barcelona, and related them to the air concentrations of terpenes, ozone and NO2. Terpene emission rates were about 10 times higher in summer than in winter. Emissions virtually stopped in the dark. In both seasons, rates of terpene emissions were well correlated with light, air temperature and relative humidity. Rates of emissions were also correlated with stomatal conductance and the rates of transpiration and photosynthesis. Almost all the individual terpenes identified followed the same pattern as total terpenes. The most abundant terpene was α-pinene, followed by sabinene + β-pinene, limonene, myrcene, camphene and α-phellandrene. Atmospheric terpene concentrations were also about 10 times higher in summer than in winter. A significant diurnal pattern with maxima at midday was observed, especially in summer. The increase by one order of magnitude in the concentrations of these volatile isoprenoids highlights the importance of local biogenic summer emissions in these Mediterranean forested areas which also receive polluted air masses from nearby or distant anthropic sources. Atmospheric concentrations of O3 and NO2 were also significantly higher in summer and at midday hours. In both seasons, concentrations of O3 were significantly correlated with concentrations of terpenes and NO2 in the air and with rates of terpene emission.

Depth-dependency of trembling aspen and paper birch small-root responses to eCO2 and eO3

Background and Aims Projected changes in the atmospheric concentrations of CO2 and tropospheric O3 over the next 50 years are of significant concern due to the linkages in the cycling of carbon and water in forested ecosystems. Responses of tree roots to elevated CO2 (eCO2) and O3 (eO3) have been characterized primarily by studies of relatively shallow roots, yet deeper roots often play a disproportionately large role in water acquisition relative to their biomass. We undertook the present study to determine if there were significant root responses to eCO2 and eO3 below the maximum soil depths typically studied.

Numerical simulations examining the possible role of anthropogenic and volcanic emissions during the 1997 Indonesian fires

The regional atmospheric chemistry and climate model REMOTE has been used to conduct numerical simulations of the atmosphere during the catastrophic Indonesian fires of 1997. These simulations represent one possible scenario of the event, utilizing the RETRO wildland fire emission database. Emissions from the fires dominate the atmospheric concentrations of O3, CO, NO2, and SO2 creating many possible exceedances of the Indonesian air quality standards. The scenario described here suggests that urban anthropogenic emissions contributed to the poor air quality due primarily to the fires. The urban air pollution may have increased the total number of people exposed to exceedances of the O3 1-h standard by 17%. Secondary O3 from anthropogenic emissions enhanced the conversion of SO2 released by the fires to {rm{SO}}_4^{2-}, demonstrating that the urban pollution actively altered the atmospheric behavior and lifetime of the fire emissions. Under the conditions present during the fires, volcanic SO2 emissions had a negligible influence on surface pollution.

Abiotic stress and transgenics: Implications for reproductive success and crop-to-wild gene flow in Brassicas

Various abiotic and biotic stressors affect crop and weed plant performance in agroecosystems. Ozone (O3) tolerance in plants is partly regulated by the genotype and phenotypical properties, and it varies greatly in related species of wild and crop backgrounds. Thus, a continuous increase in atmospheric O3 concentration could change population dynamics of sexually compatible crop and weed species, and consequently affect crop-to-wild gene flow in the future. One way to build resistance against a biotic stressor, in this case insect-mediated herbivory, in crop plants is transgene-mediated insecticidal toxin production. In this study we aimed to describe how the physiological and phenological responses in a crop Brassica and its weedy relatives functioned to affect their comparative O3 tolerance. Furthermore, we studied how harbouring a transgene affects these responses in B. napus and B. rapa × transgenic B. napus BC2F2 backcross hybrid plants to reveal any within-plant trade-offs among toxin production, growth and O3 tolerance. We found a higher number of O3 symptoms but more effective compensatory assimilate allocation directed to reproduction for wild B. rapa compared to crop B. napus under elevated O3. This result suggested that the invasion-orientated strategy of producing a high number of seeds when vegetative growth is limited might improve the performance of weedy species under elevated O3. The probabilities for crop-to-wild transgene flow could be increased through higher seed production in hybrids under elevated O3, but the germination of hybrid seeds in particular was hampered by O3. The presence of transgenes did not perturb fecundity, within-plant biomass allocation or O3 tolerance of B. napus. Verschiedene abiotische und biotische Faktoren beeinflussen die Performanz der Nutz- und Unkrautpflanzen in Agrarökosystemen. Die Ozon-(O3)-Toleranz der Pflanzen wird teilweise durch den Genotyp und durch phänotypische Eigenschaften reguliert und variiert in großem Maße bei verwandten Pflanzen mit einem wilden bzw. Nutzpflanzen-Hintergrund. Deshalb könnte eine kontinuierlich steigende O3-Konzentration in der Atmosphäre die Populationsdynamik von sexuell kompatiblen Nutz- und Unkrautarten verändern und in der Zukunft als Konsequenz den Genfluss von Nutz- zu Unkrautarten beeinflussen. Ein Weg um eine Resistenz gegenüber einem biotischen Stressor, in diesem Fall die Herbivorie durch Insekten, bei einer Nutzpflanze aufzubauen, ist die transgen vermittelte Produktion von insektiziden Toxinen. In dieser Untersuchung war es unser Ziel, zu beschreiben, wie die physiologischen und phänologischen Reaktionen bei der Nutzpflanze Brassica und ihren verwandten Unkräutern funktionierten, um ihre O3-Toleranz im Vergleich zu beeinflussen. Darüber hinaus untersuchten wir, wie die Anwesenheit eines Transgens diese Reaktionen bei B. napus und transgenen B. rapa x B. napus BC2F2 Rückkreuzungshybriden beeinflusst, um irgendwelche “trade offs” zwischen der Toxinproduktion, dem Wachstum und der O3-Toleranz innerhalb der Pflanzen festzustellen. Im Vergleich zu genutztem B. napus fanden wir unter erhöhtem O3-Gehalt eine größere Anzahl von O3-Symptomen aber auch eine effektivere, kompensatorische Assimilate-Allokation in Richtung auf die Reproduktion bei wildem B. rapa. Dieses Ergebnis lässt vermuten, dass, wenn das vegetative Wachstum limitiert ist, die invasionsorientierte Strategie durch die Produktion einer großen Anzahl von Samen die Performanz der unkrautartigen Arten bei erhöhtem O3-Gehalt verbessern könnte. Die Wahrscheinlichkeit für den Genfluss von transgenen Nutz- zu Wildpflanzen könnte durch die höhere Samenproduktion bei Hybriden bei erhöhtem O3-Gehalt erhöht sein, wenn auch die Keimung der Hybridsamen bei erhöhtem O3-Gehalt behindert wurde. Die Anwesenheit von Transgenen störte bei B. napus weder die Fruchtbarkeit, noch die Biomassenallokation innerhalb der Pflanze oder die O3-Toleranz.

Nitrogen nutrition of poplar trees

Many forest ecosystems have evolved at sites with growth-limiting nitrogen (N) availability, low N input from external sources and high ecosystem internal cycling of N. By contrast, many poplar species are frequent constituents of floodplain forests where they are exposed to a significant ecosystem external supply of N, mainly nitrate, in the moving water table. Therefore, nitrate is much more important for N nutrition of these poplar species than for many other tree species. We summarise current knowledge of nitrate uptake and its regulation by tree internal signals, as well as acquisition of ammonium and organic N from the soil. Unlike herbaceous plants, N nutrition of trees is sustained by seasonal, tree internal cycling. Recent advances in the understanding of seasonal storage and mobilisation in poplar bark and regulation of these processes by temperature and daylength are addressed. To explore consequences of global climate change on N nutrition of poplar trees, responses of N uptake and metabolism to increased atmospheric CO(2) and O(3) concentrations, increased air and soil temperatures, drought and salt stress are highlighted.

Continuous measurements of atmospheric oxygen and carbon dioxide on a North Sea gas platform

Abstract. A new atmospheric measurement station has been established on the North Sea oil and gas production platform F3, 200 km north off the Dutch coast (5°51' N, 4°44' E). Atmospheric concentrations of O2 and CO2 are continuously measured using fuel cell technology and compact infrared absorption instruments, respectively. Furthermore, the station includes an automated air flask sampler for laboratory analysis of the atmospheric concentrations of CO2, CH4, CO and O2 and isotope measurements of δ13C, δ18O and Δ14C from CO2. This station is the first fixed sea based station with on-site continuous O2 and CO2 measurements and therefore yields valuable information about the CO2 uptake in coastal marine regions, specifically the North Sea. This paper presents the measurement station and the used methodologies in detail. In comparison to land-based stations, the data show low day-to-day variability, as they are practically free of nightly inversions as well as human influences, due to the station's remoteness. Therefore, the data set collected at this measurement station serves directly as background data for the coastal northwest European region. Additionally, the first data are presented showing the seasonal cycle as expected during August 2008 through June 2009. Furthermore, some short-term O2 and CO2 signals are presented. The observations at the platform include several large and fast changing negative atmospheric O2 excursions without an accompanying change in the CO2 signal, which most likely indicate marine O2 uptake.

Geological sulfur isotopes indicate elevated OCS in the Archean atmosphere, solving faint young sun paradox

Distributions of sulfur isotopes in geological samples would provide a record of atmospheric composition if the mechanism producing the isotope effects could be described quantitatively. We determined the UV absorption spectra of 32SO2, 33SO2, and 34SO2 and use them to interpret the geological record. The calculated isotopic fractionation factors for SO2 photolysis give mass independent distributions that are highly sensitive to the atmospheric concentrations of O2, O3, CO2, H2O, CS2, NH3, N2O, H2S, OCS, and SO2 itself. Various UV-shielding scenarios are considered and we conclude that the negative Delta33S observed in the Archean sulfate deposits can only be explained by OCS shielding. Of relevant Archean gases, OCS has the unique ability to prevent SO2 photolysis by sunlight at lambda >202 nm. Scenarios run using a photochemical box model show that ppm levels of OCS will accumulate in a CO-rich, reducing Archean atmosphere. The radiative forcing, due to this level of OCS, is able to resolve the faint young sun paradox. Further, the decline of atmospheric OCS may have caused the late Archean glaciation.