若尔盖草甸退化对土壤碳、氮和碳稳定同位素的影响

为了解不同退化阶段高寒草甸土壤碳、氮和碳稳定同位素的差异,对若尔盖湿地内沼泽草甸、草原化草甸、退化草甸3个阶段土壤的碳、氮和碳稳定同位素进行了分析.结果表明:若尔盖湿地草甸土壤δ¹³C 值介于-26.21‰～-24.72‰之间,土壤δ¹³C 值随土层加深而增大.土壤δ¹³C 值与有机碳含量对数值呈线性负相关.表层土壤(0～10 cm)δ¹³C值大小顺序为草原化草甸>退化草甸>沼泽草甸,β值大小顺序为草原化草甸>沼泽草甸>退化草甸.沼泽草甸、草原化草甸、退化草甸0～30 cm 土壤碳含量分别为105.32、42.11和31.12 g·kg^-1,氮含量分别为8.74、3.41和2.81 g·kg^-1,C/N分别为11.26、11.23和10.89.随着草甸的退化,土壤碳、氮呈降低趋势,退化草甸C/N值低于沼泽草甸和草原化草甸.随着土层深度加深,碳、氮含量呈现降低趋势.草甸退化导致的土壤δ¹³C 值差异主要发生在表层0～10 cm.3个退化阶段中,退化草甸土壤的β值和C/N最低,表明退化草甸土壤矿化作用较强.     

辽宁省森林植被碳储量和固碳速率变化

利用CBM-CFS3模型,结合森林资源相关数据,研究辽宁省森林植被碳储量和固碳速率;并基于是否造林的两种假设情境,预测了未来辽宁省森林植被碳储量、碳密度和固碳速率的时空变化趋势.结果表明： 2005年辽宁省森林植被碳储量为133.94 Tg,碳密度为25.08 t·hm^-2,其中,栎类的碳储量最大,刺槐碳储量最小;落叶松和阔叶林碳密度较大,油松、栎类和刺槐碳密度基本相当.全省森林植被碳密度呈东高西低的分布规律,辽东地区由于森林多为成熟林和过熟林,未来植被碳密度增加潜力不大,辽宁南部和北部的中幼龄林未来将成为植被碳密度增长的高值区.在假设未来不造林的情景下,辽宁省森林植被碳储量上升缓慢,固碳速率下降较快;在无林地造林情景下,全省森林植被碳储量、固碳速率将明显提高.说明造林在增加森林植被碳储量和碳密度、提高森林的固碳速率中起到了重要作用.     

Carbon assimilation pathways in sulfate reducing bacteria. Formate,carbon dioxide,carbon monoxide,and acetate assimilation by Desulfovibrio baarsii

Desulfovibrio baarsii is a sulfate reducing bacterium, which can grown on formate plus sulfate as sole energy source and formate and CO₂ as sole carbon sources. It is shown by ¹⁴C labelling studies that more than 60% of the cell carbon is derived from CO₂ and the rest from formate. The cells thus grow autotrophically. Labelling studies with [¹⁴C]acetate, ¹⁴CO and [¹⁴C]formate indicate that CO₂ fixation does not proceed via the Calvin cycle. The labelling patterns of alanine, aspartate, glutamate, and glucosamine indicate that acetate (or activated acetic acid) is an early intermediate in formate and CO₂ assimilation; the methyl group of acetate is derived from formate, and the carboxyl group from CO₂ via CO; pyruvate is formed from acetyl-CoA by reductive carboxylation. The capacity to synthesize an acetate unit from two C₁-compounds obviously distinguishes D. baarsii from those Desulfovibrio species, which require acetate as a carbon source in addition to CO₂.     

A sensitive continuous and discontinuous photometric determination of oxygen, carbon dioxide, and carbon monoxide in gases and fluids.

The paper describes a sensitive, rapid, and precise photometric method for the continuous and discontinuous determination of O₂, CO₂, and CO. The method is based on highly specific color reactions: O₂ is determined by its reaction with alkaline catechol + Fe²⁺ yielding intensively colored products, CO₂ is determined by its color reaction with a solution of fuchsin + hydrazine; and CO is determined by its reaction with hemoglobin. The basic experimental equipment is that of the AutoAnalyzer (cf.Wolf, Zander, and Lang, 1976, Anal. Biochem.74, 585), with an additional chamber for the injection of small gas samples in the case of the discontinuous analysis. Continuously analyzing in a standardized gas flow of 1 ml · min^?1 (STPD), the lower limits of the sensitivities are 50 ppm for O₂, 100 ppm for CO₂, and 50 ppm for CO. The discontinuous analysis of the three gases requires the basic experimental equipment plus an airtight chamber. The lower limits of the amounts are 0.1 μl (STPD) for O₂, 0.2 μl for CO₂, and 0.1 μl for CO.     

Cardiac anoxia tolerance of carbon monoxide-poisoned, hypoxia-exposed and normal rats.

Under nitrogen anoxia heart rate (HR) persists at a high level for 1 min longer in rats exposed chronically to carbon monoxide and hypoxia than in unexposed control rats. Although declining sharply, HR of exposed animals continues higher than HR of controls during min 1-4 of anoxia. However, during min 5 and 6 of anoxia HR of CO-poisoned rats becomes similar to that of controls, while HR of hypoxia-exposed rats remains above control HR for 3 min longer. The data are discussed in light of cardiovascular changes induced by CO and hypobaric hypoxia.     

Photosynthesis,carbon allocation,and growth of sulfur dioxide ecotypes ofGeranium carolinianum L.

Summary This study investigated ways in which genetically determined differences in SO₂ susceptibility resulting from ecotypic differentiation inGeranium carolinianum were expressed physiologically. The SO₂-resistant and SO₂-sensitive ecotypes were exposed to a combination of short- and long-term SO₂ exposures to evaluate the responses of photosynthesis, H₂S efflux from foliage (sulfur detoxification), photoassimilate retention, leaf-diffusive resistance to CO₂, and growth. When exposed to SO₂, both ecotypes re-emit sulfur in a volatile, reduced form, presumably as H₂S. Because H₂S efflux rates at various SO₂ concentrations were comparable between ecotypes, genetic differences inG. carolinianum could not be attributed to a re-emission of excess sulfur as H₂S. Incipient SO₂ effects on photosynthesis were observed as cumulative SO₂ flux into the leaf interior excecded 0.40 nmol·m^–2 in the resistant ecotype and 0.26 nmol·m^–2 in the sensitive ecotype. Although initial SO₂-induced changes in photosynthesis in both ecotypes were mediated through an increase in stomatal resistance to CO₂, the ecotype-specific patterns as a function of pollutant concentration and exposure time were associated with marked increases in residual resistance to CO₂. Patterns in photosynthesis, photoassimilate retention, and growth following long-term SO₂ exposures were also ecotype-specific. Although physiological accommodation of SO₂ stress was observed in both ecotypes, it was more pronounced in the resistant ecotype. The physiological mechanisms underlying genetic differences inG. carolinianum in response to SO₂ stress were concluded to be (1) dissimilar threshold levels of response to SO₂ and/or its toxic derivatives and (2) differences in homeostatic processes governing the rate of repair or compensation for physiological injury.Research sponsored by the Office of Health and Environmental Research, U.S. Department of Energy, under contract No. DEAC05-840R21400 with Martin Marietta, Energy Systems, Inc. and the U.S. Environmental Protection AgencyPublication No. 2610, Environmental Sciences Division, Oak Ridge National Laboratory     

Transport and fate of dissolved organic carbon in the Lake Pontchartrain esutary,Louisiana, U.S.A.

Cycling dynamics of dissolved organic carbon (DOC) were examinedin Lake Pontchartrain estuary, Louisiana, in relation to changesin freshwater inputs. DOC concentrations ranged from 5.3 to 8.5mg C L-1 reaching their highest during high river inflow.The percentage of DOC represented by HMW DOC (or colloidal material)was greatest (ca. 11%) at stations where freshwaterdischarge from rivers and surrounding wetlands was most significant.Moreover, the lignin-phenol content of this material (ranged from 0.09 to 0.33 and from 0.11 to 0.39)confirmed that a significant fraction of colloidal organic carbon wasderived from terrestrial sources. Riverine and benthic fluxes representedthe dominant sources of DOC to the estuary. On an annual basis, riverineand benthic DOC concentrations were estimated to be 2.8 ×10 10 g C yr-1 and 8.8 × 10 10 g C yr-1, respectively, while the totalDOC pool in the estuary was 3.8 × 10 10 gC. Annual average concentrations of dissolved inorganic carbon (DIC)(1298 M) and pCO2 (5774 atm)were comparable to those found in other freshwater systems that reachedCO2 saturation levels. Net losses of DOC in the LakePontchartrain estuary appeared to be primarily controlled by heterotrophicconsumption (conversion of CO2) – whichmay have been amplified by the long residence time (approximately 120days) of DOC in this system.     

Growth response of axenic Entamoeba histolytica to hydrogen, carbon dioxide, and oxygen.

Entamoeba histolytica required CO2 for growth in axenic culture while growth was inhibited by H2. The organism was tolerant to 5% O2 in the gas phase and it was able to detoxify products of O2 reduction in the medium. The ameba did not require a negative oxidation-reduction potential for axenic growth. However, little or no free O2 was present in media exposed to 5% O2 in the gas phase. Growth was improved by adding yeast extract to the medium.     

Soil organic carbon dynamics jointly controlled by climate,carbon inputs,soil properties and soil carbon fractions

Soil organic carbon (SOC) dynamics are regulated by the complex interplay of climatic, edaphic and biotic conditions. However, the interrelation of SOC and these drivers and their potential connection networks are rarely assessed quantitatively. Using observations of SOC dynamics with detailed soil properties from 90 field trials at 28 sites under different agroecosystems across the Australian cropping regions, we investigated the direct and indirect effects of climate, soil properties, carbon (C) inputs and soil C pools (a total of 17 variables) on SOC change rate (r_C, Mg C ha^?1 yr^?1). Among these variables, we found that the most influential variables on r_C were the average C input amount and annual precipitation, and the total SOC stock at the beginning of the trials. Overall, C inputs (including C input amount and pasture frequency in the crop rotation system) accounted for 27% of the relative influence on r_C, followed by climate 25% (including precipitation and temperature), soil C pools 24% (including pool size and composition) and soil properties (such as cation exchange capacity, clay content, bulk density) 24%. Path analysis identified a network of intercorrelations of climate, soil properties, C inputs and soil C pools in determining r_C. The direct correlation of r_C with climate was significantly weakened if removing the effects of soil properties and C pools, and vice versa. These results reveal the relative importance of climate, soil properties, C inputs and C pools and their complex interconnections in regulating SOC dynamics. Ignorance of the impact of changes in soil properties, C pool composition and C input (quantity and quality) on SOC dynamics is likely one of the main sources of uncertainty in SOC predictions from the process‐based SOC models.     

Activity and stability comparison of immobilized NADH oxidase on multi-walled carbon nanotubes,carbon nanospheres,and single-walled carbon nanotubes

Nanomaterials have been studied widely as the supporting materials for enzyme immobilization because in theory, they can provide low diffusion resistance and high surface/volume ratio. Common immobilization methods, such as physical adsorption, covalent binding, crosslinking, and encapsulation, often cause problems in enzyme leaching, 3D structure change and strong mass transfer resistance. We have previously demonstrated a site-specific enzyme immobilization method, which is based on the specific interaction between a His-tagged enzyme and functionalized single-walled carbon nanotubes (SWCNTs), that can overcome the foresaid constraints. In this work, we broadened the use of this immobilization approach by applying it on other nanomaterials, including multi-walled carbon nanotubes and carbon nanospheres. Both supporting materials were modified with N_α,N_α-bis(carboxymethyl)-l-lysine hydrate prior to enzyme immobilization. The resulting nanomaterial–enzyme conjugates could maintain 78–87% of the native enzyme activity and showed significantly better stability than the free enzyme. When compared with the SWCNT–enzyme conjugate, we found that the size variance among these supporting nanomaterials may affect factors such as surface curvature, surface coverage and particle mobility, which in turn results in differences in the activity and stability among these immobilized biocatalysts.     

石灰碳汇综述

以“碳失汇”科学之谜和碳捕集与封存技术发展为背景,从石灰碳化原理、影响因素和石灰在化工、冶金、建筑以及石灰窑灰处理等领域的利用方式,综述了石灰物质流动过程的碳汇研究.结果发现: 石灰材料和环境条件是影响碳化的主要因素;石灰碳汇主要集中在化工、冶金和建筑领域;已有研究侧重分析石灰碳汇的机理、影响因素,但缺乏系统的碳汇核算方法.今后的研究工作应从以下几方面加强: 从物质流动的角度出发,建立系统完整的石灰碳汇核算方法;量化我国乃至全球的石灰碳汇量,阐明石灰生产过程中排放的CO₂抵消比例;分析石灰碳汇对碳失汇的贡献比例,明晰部分失踪碳汇;推动石灰碳捕集与封存技术发展,为我国应对气候变化国际谈判提供科学依据.     

陆地碳循环研究中的模型方法

陆地碳循环是全球变化研究中的重要内容,碳循环模型已成为研究陆地碳循环的必要方法．其中气候变化、大气ＣＯ２浓度上升以及人类活动引起的土地利用和土地覆盖变化导致陆地生态系统在结构、功能、组成和分布等方面的变化及其反馈关系对陆地碳循环的影响是模型模拟的关键问题．生物地理模型和生物地球化学模型是碳循环模型的两大类型,建模方法、模型性质、特点和应用范围各异．碳循环模型的发展方向是综合两类模型的特点,建立全球动态碳循环模型．     

西双版纳地区人工橡胶林生物量、固碳现状及潜力

选取西双版纳地区橡胶树适宜和次适宜种植区6个年龄段(5、9、14、19、23、26年生)的橡胶林,对其生长参数进行了实测,利用生物量回归方程得到了橡胶林的生物量和固碳量,并探讨了橡胶林的固碳潜力。结果表明:西双版纳适宜种植区橡胶林地上净初级生产力(ANPP)在19年生时达到最大,为(16.22±3.47)t.hm-2.a-1;次适宜种植区橡胶林ANPP在23年生时达到最大,为(8.65±3.46)t.hm-2.a-1。适宜和次适宜种植区橡胶林地上总生物量(WA)最大值分别为205.82和139.76t.hm-2。对应的生物量内禀增长率分别为21%和14%。适宜和次适宜种植区橡胶林碳储量最大值分别达123.49和83.86tC.hm-2,均明显低于西双版纳热带季节雨林生态系统的总固碳量(311.41±66.46)tC.hm-2,适宜种植区橡胶林固碳量略高于世界热带森林的平均水平(121tC.hm-2)。截至2008年,西双版纳橡胶林总固碳量约为16.54×106tC。     

Measurement of dissolved carbon dioxide.

Several probes for measuring dissolved carbon dioxide (CO2) concentration were installed in a 68-litre fermentor and their effectiveness compared. Submerged silastic rubber tubing gave reproducible results over a wide range of operating conditions and was generally superior to all other probes evaluated. The silastic rubber probe was used to compare the partial pressure of CO2 in viscous fermentation media with that in the fermentor exhaust gas. No significant difference was found. Results show that determination of the CO2 partial pressure in the exhaust gas gives an excellent approximation of the partial pressure of dissolved CO2 in the liquid medium, eliminating the need for measurement of CO2 concentration in the broth.     

Cooperative reactions of poly-L-lysine-heme complex with molecular oxygen, carbon monoxide, or cyanide ion.

The interaction of the alpha-helical poly-L-lysine-heme complex with molecular oxygen, carbon monoxide, or cyanide ion was studied. Binding equilibrium curve and activation parameters for the reactions were determined. Sigmoid responses were observed for the absorption of molecular oxygen or carbon monoxide by the complex and the cooperative parameter was found to be 2.1. This indicated a cooperative interaction between hemes situated on a cylindrical alpha-helix of poly-L-lysine. But those of other polymer-ligand-heme complexes were 1.0. The cooperative reaction mechanism, in which an alpha-helical poly-L-lysine plays an important role, was suggested.     

Incorporation rate of glucose carbon, palmitate carbon and leucine carbon into metabolites in relation to enzyme activities and RNA levels in human skeletal muscles.

The activities (Vmax) of hexokinase, glycogen phosphorylase, glucose-6-phosphate dehydrogenase, phosphofructokinase, lactate dehydrogenase, citrate synthase, cytochrome c oxidase, and 3-OH-acyl-CoA dehydrogenase in human skeletal muscles were compared with the in vitro utilization of glucose and palmitic acid assessed under optimal conditions. Statistically significant correlations between substrate fluxes and enzyme activities were found suggesting that the substrate incorporation rate in vitro in some way reflects the capacity of metabolic pathways. The incorporation rate of leucine into muscle proteins was also statistically significantly correlated to the RNA concentration in the muscle tissue. Glycolytic and glycogenolytic enzymes correlated significantly to each other and correlations were also found between aerobic enzymes supporting the validity of constant proportions between certain key enzymes in human skeletal muscles.