Apoplastic ascorbate contributes to the differential ozone sensitivity in two varieties of winter wheat under fully open-air field conditions

We studied leaf apoplastic ascorbates in relation to ozone (O₃) sensitivity in two winter wheat (Triticum aestivum L.) varieties: Yangfumai 2 (Y2) and Yangmai 16 (Y16). The plants were exposed to elevated O₃ concentration 27% higher than the ambient O₃ concentration in a fully open-air field from tillering stage until final maturity. The less sensitive variety Y16 had higher concentration of reduced ascorbate in the apoplast and leaf tissue by 33.5% and 12.0%, respectively, than those in the more sensitive variety Y2, whereas no varietal difference was detected in the decline of reduced ascorbate concentration in response to elevated O₃. No effects of O₃ or variety were detected in either oxidized ascorbate or the redox state of ascorbate in the apoplast and leaf tissue. The lower ascorbate concentrations in both apoplast and leaf tissue should have contributed to the higher O₃ sensitivity in variety Y2.     

Exposure to elevated ozone levels differentially affects the antioxidant capacity and the redox homeostasis of two subtropical Phaseolus vulgaris L. varieties

Ozone (O₃) has become one of the most toxic air pollutants to plants worldwide. However, investigations on O₃ impacts on crops health and productivity in South America countries are still scarce. The present study analyzed the differences on the enzymatic and non-enzymatic antioxidant system in foliar tissue of two subtropical Phaseolus vulgaris varieties exposed to high O₃ concentration. Both varieties were negatively impacted by the pollutant, but the responses between each variety were quite distinct. Results revealed that Irai has higher constitutive levels of reactive oxygen species (ROS) and ascorbate (AsA) concentration, but lower total thiol levels and catalase immunocontent. In this variety catalase protein concentration was increased after O₃ exposure, indicating a better cellular capacity to reduce hydrogen peroxide. On the opposite, Fepagro 26-exposed plants increased ROS generation and AsA concentration, but had the levels of total thiol content and catalase protein unchanged. Furthermore, O₃ treatment reduced the levels of chlorophylls a and b, and the relationship analysis between the chlorophyll ratio (a/b) and protein concentration were positively correlated indicating that photosynthetic apparatus is compromised, and thus probably is the biomass acquisition on Fepagro 26. Differently, O₃ treatment of Irai did not affect chlorophylls a and b content, and loss on the protein content was lower. Altogether, these data suggest that early accumulation of ROS on Fepagro 26 are associated with an insufficient leaf antioxidant capacity, which leads to cell structure disruption and impairs the photosynthesis. Irai seems to be more tolerant to O₃ toxic effects than Fepagro 26, and the observed differences on O₃ sensitivity between the two varieties are apparently based on constitutive differences involved in the maintenance of intracellular redox homeostasis.     

Pseudomonas S2-3菌株对Cr(VI)的耐受性及去除

针对分离得到的Cr(VI)耐受菌株S2-3进行了基本生长特征、16S rRNA序列分析、Cr(VI)对菌株生长影响、菌株生长代谢与铬的去除的关系等研究。结果表明:该菌株属于假单胞菌,与Pseudomonas chlororaphis(Z76673)相似性最高(99.8%);Cr(VI)对菌株生长有着明显的抑制作用,其耐受上限可达到1500 mg/L左右;Cr(VI)导致菌体细胞大小分布变宽,同时使得细胞表面的-OH和-NH基团减少。当初始Cr(VI)浓度为100 mg/L时,48 h内菌株S2-3对Cr(VI)去除效率可达到85.9%,对总铬去除率为24.1%。在高Cr(VI)浓度(1000 mg/L)下,菌株对Cr(VI)和总铬仍有一定的去除效果,分别为58.7%和3.3%。菌株S2-3主要通过还原Cr(VI)的方式去除Cr(VI)。Cr(VI)的还原与菌液ORP以及细胞表面的-OH和-NH有关;总铬的去除不是因为形成了氢氧化铬沉淀,而是Cr(III)被吸附在了细胞表面的-C=O上。     

Evolution of tolerance to PCBs and susceptibility to a bacterial pathogen (Vibrio harveyi) in Atlantic killifish (Fundulus heteroclitus) from New Bedford (MA, USA) harbor

A population of the non-migratory estuarine fish Fundulus heteroclitus (Atlantic killifish) resident to New Bedford (NB), Massachusetts, USA, an urban harbor highly contaminated with polychlorinated biphenyls (PCBs), demonstrates recently evolved tolerance to some aspects of PCB toxicity. PCB toxicology, ecological theory, and some precedence supported expectations of increased susceptibility to pathogens in NB killifish. However, laboratory bacterial challenges of the marine pathogen Vibrio harveyi to wild fish throughout the reproductive season and to their mature laboratory-raised progeny demonstrated comparable survival by NB and reference killifish, and improved survival by NB males. These results are inconsistent with hypothesized trade-offs of adaptation, and suggest that evolved tolerance in NB killifish may include mechanisms that minimize the immunosuppressive effects of PCBs. Compensatory strategies of populations persisting in highly contaminated environments provide a unique perspective for understanding the long-term ecological effects of toxic chemicals.     

Integrated biological responses of zebrafish (Danio rerio) to analyze water quality in regions under anthropogenic influence

This study analyzed water quality in regions around Patos lagoon (Southern Brazil) that are under anthropogenic pressure. Water samples were collected from five different sites, including one used as a source for human consumption (COR) and others known to be influenced by human activities (IP). Danio rerio (Teleostei, Cyprinidae) organisms were exposed for 24 h to these water samples, plus a control group. It was observed that: (1) reactive oxygen species levels were lower in COR and IP than in the control group; (2) glutamate-cysteine ligase (catalytic subunit) expression was higher in COR than in other sites; (3) exposure to all water samples affected long-term memory (LTM) when compared to control group. Thus, some water samples possess the ability to modulate the antioxidant system and to induce a decline in cognitive functions, as measured by LTM. The obtained results indicate that a combination of variables of different organization level (molecular, biochemical and behavioral) can be employed to analyze water quality in impacted regions.     

Study on the formation and transport of ozone in relation to the air quality management and vegetation protection in Tenerife (Canary Islands)

An experimental study on the formation and transport of ozone in ambient air was performed in Tenerife (Canary Islands) in order to investigate the processes affecting ozone levels and air quality. The special features of Tenerife (prevalence of the trade wind pattern (NE), orography and the specific location of the local ozone sources) permit to quantify the role of the ‘long-range transport from northern latitudes' versus the ‘formation and transport of ozone downwind of the main urban areas' of Tenerife. Levels of O₃, NO₂ and O_X were monitored in different types of environments to achieve this purpose. The results showed that: (1) upwind of the urban areas ozone is mainly transported from the ocean by trade winds, (2) local ozone titration (by NO) and ozone replenishment from the ocean are the main causes of ozone variations in urban and suburban areas, and (3) photochemical ozone production occurs downwind of the urban areas. Photochemical production causes daylight O₃ and O_X levels downwind of urban areas to be frequently (60% and 35% days/year, respectively) higher than upwind of the urban sites (O₃ and O_X excess frequently in the range 5–20 ppbv). Due to the above processes, different daily ozone cycles occur in short distances (<30 km), with maximum O₃ levels during daylight or night depending on the site. Ozone phytotoxicity was assessed by calculating the AOT40 index upwind and downwind of the main urban areas. The critical value for the 5-day-AOT40 index was simultaneously exceeded at the two sites (few times/year) during long-range transport events. During the additional exceedances of the critical value downwind of the urban area, relatively high 5-day-AOT40 values were recorded upwind of the urban site. Thus, long-range transport from northern latitudes may produce relatively high 5-days-AOT40 levels in the oceanic boundary layer. These results are important for the protection of the large number of endemic plants in the Canaries. The conceptual model discussed in this study may be qualitatively applied to other islands which possess features similar to those of Tenerife.     

Response of hydrogen peroxide scavenging system in two soybean cultivars exposed to SO2: experimental evidence for the detoxification of SO2 by enhanced H2O2 scavenging components

The impact of SO(2) on superoxide dismutase (SOD) and the ascorbate-glutathione cycle was investigated in a tolerant (cv. Punjab-1) and a sensitive (cv. JS 7244) cultivar of soybean (Glycine max (L.) Merr.). In spite of SO(2) stimulated SOD activities in both the cultivars, only cv. JS 7244 has significantly enhanced Malondialdehyde (MDA) contents. This differential response was attributed to the ability of cv. Punjab-1 to enhance glutathione reductase (GR) activity and to maintain high GSH/GSSG and ASA/DHA ratios. Post-fumigation analysis indicated the ability of cv. Punjab-1 to maintain SO(2)-enhanced antioxidants, whilst they declined in cv. JS 7244 the moment fumigation was terminated. Exposure of SO(2)-acclimated plants (cv. Punjab-1) with their enhanced antioxidants to 250 microg m(-3) SO(2) for 6 h exhibited no enhanced cellular injury (MDA content) when compared to that of control plants with their normal antioxidant levels. These results indicate a relation between the ability of a plant to maintain reduced glutathione (GSH) and ascorbate (ASA) and SO(2) tolerance, and they also present evidence for the ability of plants, with elevated antioxidants, to tolerate SO(2)-induced oxygen-free radical toxicity.     

Isozyme markers associated with O(3) tolerance indicate shift in genetic structure of ponderosa and Jeffrey pine in Sequoia National Park, California

Effects of canopy ozone (O(3)) exposure and signatures of genetic structure using isozyme markers associated with O(3) tolerance were analyzed in approximately 20-, approximately 80-, and >200-yr-old ponderosa (Pinus ponderosa Dougl. ex Laws.) and Jeffrey pine (Pinus jeffreyi Grev. & Balf.) in Sequoia National Park, California. For both species, the number of alleles and genotypes per loci was higher in parental trees relative to saplings. In ponderosa pine, the heterozygosity value increased, and the fixation index indicated reduction of homozygosity with increasing tree age class. The opposite tendencies were observed for Jeffrey pine. Utilizing canopy attributes known to be responsive to O(3) exposure, ponderosa pine was more symptomatic than Jeffrey pine, and saplings were more symptomatic than old growth trees. We suggest that these trends are related to differing sensitivity of the two species to O(3) exposure, and to higher O(3) exposures and drought stress that younger trees may have experienced during germination and establishment.     

Seasonal changes of CO(2), CH(4) and N(2)O fluxes in relation to land-use change in tropical peatlands located in coastal area of South Kalimantan

Tropical peatland could be a source of greenhouse gases emission because it contains large amounts of soil carbon and nitrogen. However these emissions are strongly influenced by soil moisture conditions. Tropical climate is characterized typically by wet and dry seasons. Seasonal changes in the emission of carbon dioxide (CO(2)), methane (CH(4)) and nitrous oxide (N(2)O) were investigated over a year at three sites (secondary forest, paddy field and upland field) in the tropical peatland in South Kalimantan, Indonesia. The amount of these gases emitted from the fields varied widely according to the seasonal pattern of precipitation, especially methane emission rates were positively correlated with precipitation. Converting from secondary forest peatland to paddy field tended to increase annual emissions of CO(2) and CH(4) to the atmosphere (from 1.2 to 1.5 kg CO(2)-C m(-2)y(-1) and from 1.2 to 1.9 g CH(4)-C m(-2)y(-1)), while changing land-use from secondary forest to upland tended to decrease these gases emissions (from 1.2 to 1.0 kg CO(2)-C m(-2)y(-1) and from 1.2 to 0.6 g CH(4)-C m(-2)y(-1)), but no clear trend was observed for N(2)O which kept negative value as annual rates at three sites.     

Investigation of a new approach to decompose two potent greenhouse gases: photoreduction of SF(6) and SF(5)CF(3) in the presence of acetone

In this paper, we addressed the utilization of photochemical method as an innovative technology for the destruction and removal of two potent greenhouse gases, SF(6) and SF(5)CF(3). The destruction and removal efficiency (DRE) of the process was determined as a function of excitation wavelength, irradiation time, initial ratio of acetone to SF(5)X (X represented F or CF(3)), initial SF(5)X concentration, additive oxygen and water vapor concentration. A complete removal was achieved by a radiation period of 55min and 120min for SF(6)-CH(3)COCH(3) system and SF(5)CF(3)-CH(3)COCH(3) system respectively under 184.9nm irradiation. Extra addition of water vapor can enhance DRE by approximately 6% points in both systems. Further studies with GC/MS and FT-IR proved that no hazardous products such as S(2)F(10), SO(2)F(2), SOF(2), SOF(4) were generated in this process.     

Wild fire impact on copper, zinc, lead and cadmium distribution in soil and relation with abundance in selected plants of Lamiaceae family from Vidlic Mountain (Serbia)

Fire has been considered as an improving factor in soil quality, but only if it is controlled. Severe wild fire occurred in the summer 2007 on the Vidlic Mountain (Serbia) overspreading a huge area of meadows and forests.Main soil characteristics and content of heavy metals (Cu, Pb, Cd, Zn) in different fractions obtained after sequential extraction of soil from post-fire areas and from fire non disturbed areas were studied. In four plant species of Lamiaceae family (Ajuga genevensis L., Lamium galeobdolon (L.) L., Teucrium chamaedrys L., Acinos alpinus (L.) Moench.), that grow in typical habitats of the mountain, distribution of heavy metals in aerial parts and roots was investigated too.For all samples from post-fire area cation exchange capacity and soil organic matter content are increased while rH is decreased. Fire caused slightly increased bioavailability of the observed metals but more significant rise happened in metal amounts bound to oxides and organics. The plants showed variable behavior. T. chamaedrys collected on the post-fire area contained elevated concentrations of all analyzed metals. A. alpinus showed higher phytoaccumulation for Zn and Cd, while the other two plant species for Pb and Cd in the post-fire areas.     

Effects of decadal exposure to interacting elevated CO2 and/or O3 on paper birch (Betula papyrifera) reproduction

We studied the effects of long-term exposure (nine years) of birch (Betula papyrifera) trees to elevated CO(2) and/or O(3) on reproduction and seedling development at the Aspen FACE (Free-Air Carbon Dioxide Enrichment) site in Rhinelander, WI. We found that elevated CO(2) increased both the number of trees that flowered and the quantity of flowers (260% increase in male flower production), increased seed weight, germination rate, and seedling vigor. Elevated O(3) also increased flowering but decreased seed weight and germination rate. In the combination treatment (elevated CO(2)+O(3)) seed weight is decreased (20% reduction) while germination rate was unaffected. The evidence from this study indicates that elevated CO(2) may have a largely positive impact on forest tree reproduction and regeneration while elevated O(3) will likely have a negative impact.     

膜生物反应器中EPS对污泥絮体形成的影响及其膜污染特性研究

为了给减缓膜生物反应器(MBR)膜污染提供新思路,对MBR中EPS各组分对污泥聚集性能的影响及其膜污染特性进行研究。通过分析MBR中污泥的聚集性,发现原始污泥的聚集速率常数为0.0151,提取EPS后污泥的聚集速率常数为0.00181,由此可以看出EPS在污泥聚集的过程中起重要作用。为了进一步明确EPS各组分对MBR中污泥聚集性能的影响,利用扩展的DLVO理论研究MBR中EPS及其各组分对污泥聚集性能的影响,发现MBR中EPS里粘液的二级能量最小值大约为-0.94 KT,松散型EPS(LB-EPS)为-2.98 KT,紧密型EPS(TB-EPS)为-3.87 KT,说明TB-EPS在污泥聚集的过程中起重要作用。进一步通过三维荧光光谱及EPS浓度分析,发现EPS各组分浓度及结构的不同导致EPS各组分对污泥聚集性起不同的作用。通过吸附实验、原子力显微镜观察发现EPS各组分的膜污染速率为:上清液 < 粘液 < LB-EPS < TB-EPS,由此,可以推测出减少粘液和LB-EPS含量可有效降低膜污染,同时对污泥絮体结构影响较小。     

Seasonal variations of CH(4) and N(2)O emissions in response to water management of paddy fields located in Southeast China

Water management is one of the most important practices that affect methane (CH₄) and nitrous oxide (N₂O) emissions from paddy fields. A field experiment was designed to study the effects of controlled irrigation (CI) on CH₄ and N₂O emissions from paddy fields, with traditional irrigation (TI) as the control. The effects of CI on CH₄ and N₂O emissions from paddy fields were very clear. The peaks of CH₄ emissions from the CI paddies were observed 1-2 d after the water layer disappeared. Afterward, the emissions reduced rapidly and remained low until the soil was re-flooded. A slight increase of CH₄ emission was observed in a short period after re-flooding. N₂O emissions peaks from CI paddies were all observed 8-10 d after the fertilization at the WFPS ranging from 78.1% to 85.3%. Soil drying caused substantial N₂O emissions, whereas no substantial N₂O emissions were observed when the soil was re-wetted after the dry phase. Compared with TI, the cumulative CH₄ emissions from the CI fields were reduced by 81.8% on the average, whereas the cumulative N₂O emissions were increased by 135.4% on the average. The integrative global warming potential of CH₄ and N₂O on a 100-year horizon decreased by 27.3% in the CI paddy fields, whereas no significant difference in the rice yield was observed between the CI and TI fields. These results suggest that CI can effectively mitigate the integrative greenhouse effect caused by CH₄ and N₂O emissions from paddy fields while ensuring the rice yield.     

Chronic toxicity of ZnO nanoparticles, non-nano ZnO and ZnCl2 to Folsomia candida (Collembola) in relation to bioavailability in soil

The chronic toxicity of zinc oxide nanoparticles (ZnO-NP) to Folsomia candida was determined in natural soil. To unravel the contribution of particle size and free zinc to NP toxicity, non-nano ZnO and ZnCl₂ were also tested. Zinc concentrations in pore water increased with increasing soil concentrations, with Freundlich sorption constants K_f of 61.7, 106 and 96.4 l/kg (n = 1.50, 1.34 and 0.42) for ZnO-NP, non-nano ZnO and ZnCl₂ respectively. Survival of F. candida was not affected by ZnO-NP and non-nano ZnO at concentrations up to 6400 mg Zn/kg d.w. Reproduction was dose-dependently reduced with 28-d EC50s of 1964, 1591 and 298 mg Zn/kg d.w. for ZnO-NP, non-nano ZnO and ZnCl₂, respectively. The difference in EC50s based on measured pore water concentrations was small (7.94-16.8 mg Zn/l). We conclude that zinc ions released from NP determine the observed toxic effects rather than ZnO particle size.     

改性炭化谷壳负载纳米Fe3O4对含As(V)废水的吸附性能

以谷壳为原料,通过600℃缺氧高温热解制备一种炭化谷壳（CRH-I）,并利用CRH-I通过改性负载方法获得另一种新型的负载纳米Fe3O4的碱改性炭化谷壳（CRH-II）。经过对比表面积进行表征分析发现,CRH-II相较CRH-I的BET比表面积增大约30%,达到182 m2·g-1,微比表面积和微孔体积都扩大了6倍左右。FTIR分析结果表明,相比CRH-I,CRH-II分子间的羧基和酚羟基官能团有所增加,产生了芳构化反应和脂肪醚类物质。吸附实验表明,相对CRH-I而言,CRH-II对As（V）的吸附率明显提高。pH=2时,CRH-II对溶液中As（V）的吸附率达到98.3%;但是As的吸附率随着溶液pH值升高而逐渐降低,pH=11时下降最为明显,吸附率只有63.4%。CRH-II吸附反应满足准动力学二级方程,其相关系数为R2=0.999;在不同温度下,将CRH-II对As（V）的吸附验数据进行Langmuir方程和Freundlich等温方程拟合,结果更符合Langmuir方程;在25℃时,相关系数R2=0.985。解吸吸附实验证明,CRH-II依然具备良好的吸附性能,且再生吸附性能稳定。     

Gene expression responses of paper birch (Betula papyrifera) to elevated CO2 and O3 during leaf maturation and senescence

Gene expression responses of paper birch (Betula papyrifera) leaves to elevated concentrations of CO₂ and O₃ were studied with microarray analyses from three time points during the summer of 2004 at Aspen FACE. Microarray data were analyzed with clustering techniques, self-organizing maps, K-means clustering and Sammon's mappings, to detect similar gene expression patterns within sampling times and treatments. Most of the alterations in gene expression were caused by O₃, alone or in combination with CO₂. O₃ induced defensive reactions to oxidative stress and earlier leaf senescence, seen as decreased expression of photosynthesis- and carbon fixation-related genes, and increased expression of senescence-associated genes. The effects of elevated CO₂ reflected surplus of carbon that was directed to synthesis of secondary compounds. The combined CO₂ + O₃ treatment resulted in differential gene expression than with individual gas treatments or in changes similar to O₃ treatment, indicating that CO₂ cannot totally alleviate the harmful effects of O₃.     

Use of sap flow measurements to validate stomatal functions for mature beech (Fagus sylvatica) in view of ozone uptake calculations

For a quantitative estimate of the ozone effect on vegetation reliable models for ozone uptake through the stomata are needed. Because of the analogy of ozone uptake and transpiration it is possible to utilize measurements of water loss such as sap flow for quantification of ozone uptake. This technique was applied in three beech (Fagus sylvatica) stands in Switzerland. A canopy conductance was calculated from sap flow velocity and normalized to values between 0 and 1. It represents mainly stomatal conductance as the boundary layer resistance in forests is usually small. Based on this relative conductance, stomatal functions to describe the dependence on light, temperature, vapour pressure deficit and soil moisture were derived using multivariate nonlinear regression. These functions were validated by comparison with conductance values directly estimated from sap flow. The results corroborate the current flux parameterization for beech used in the DO₃SE model.     

Responses of CH(4), CO(2) and N(2)O fluxes to increasing nitrogen deposition in alpine grassland of the Tianshan Mountains

To assess the effects of nitrogen (N) deposition on greenhouse gas (GHG) fluxes in alpine grassland of the Tianshan Mountains in central Asia, CH₄, CO₂ and N₂O fluxes were measured from June 2010 to May 2011. Nitrogen deposition tended to significantly increase CH₄ uptake, CO₂ and N₂O emissions at sites receiving N addition compared with those at site without N addition during the growing season, but no significant differences were found for all sites outside the growing season. Air temperature, soil temperature and water content were the important factors that influence CO₂ and N₂O emissions at year-round scale, indicating that increased temperature and precipitation in the future will exert greater impacts on CO₂ and N₂O emissions in the alpine grassland. In addition, plant coverage in July was also positively correlated with CO₂ and N₂O emissions under elevated N deposition rates. The present study will deepen our understanding of N deposition impacts on GHG balance in the alpine grassland ecosystem, and help us assess the global N effects, parameterize Earth System models and inform decision makers.     

Ageing of chromium(III)-bearing slag and its relation to the atmospheric oxidation of solid chromium(III)-oxide in the presence of calcium oxide

Slag arising in ferrochromium and stainless steel production is known to contain residual levels of trivalent chromium. As the chromium is normally bound in the slag matrix in various silicate or spinel phases, and hence not easily mobilised, utilisation or controlled disposal of such slag is generally considered unproblematic. Experimental test work with a number of slag materials indicates, however, that very gradual oxidation of trivalent to hexavalent chromium does occur when the slag is exposed to atmospheric oxygen, rendering a quantifiable but small portion of chromium in this much more mobile and toxic form. Mechanisms and rates of the oxidation reaction were investigated in a number of long-term studies using both original slag materials and artificial mixes of chromium and calcium oxides. Powders of these materials, some of them rolled into balls, were left to age under different conditions for periods of up to 12 months. In the slag samples, which contained between 1 and 3 wt.% chromium, 1000–10 000 μg Cr(VI) were found per gram of chromium within 6–9 months of exposure to an ambient atmosphere. The rate of the oxidation reaction decreased exponentially, and the reaction could generally be said to have ceased within 12 months. In mixtures of calcium and chromium oxides the oxidation reaction is presumed to occur at the boundaries between chromium oxide and calcium oxide phases through diffusion of oxygen along the grain boundaries and of Cr³⁺ across the boundaries, resulting in the formation of calcium chromate. In the slags, where calcium and chromium oxide can form a solid solution, the oxidation is likely to occur at the exposed surface of grains containing this solution.