Responses of rice growth to copper stress under free-air CO2 enrichment （FACE）

The responses of rice to the second degree contamination of copper were studied by pot experiments under free-air CO2 enrichment （FACE） with 570 μmol ·mol^-1 of CO2. The results showed that the content of copper in rice leaves was reduced with the CO2 concentration reaching 570 μmol· mol^-1 and this happened more significantly under the second degree contamination of copper. Under FACE, activities of superoxide dismutase （SOD） enzyme in rice leaves treated by copper contamination were induced, whereas the contents of glutathione （GSH） and glutathione disulfide （GSSG） had no significant difference from the control. In the presence of ambient CO2, activities of SOD enzyme treated by copper pollution were suppressed during the whole rice growth, however, the contents of GSH and GSSG were induced at tillering and jointing stages, and then restored to the control levels in later growth under the second degree contamination of copper. With the rice growing, the content of malondialdehyde （MDA） rises continuously, but there had been no significant difference between the treatments at the same growth stage. Further studies are needed on the response mechanism of rice to Cu stress under elevated CO2.     

Features of major greenhouse gases in loess, Shanxi Province, China

According to the investigations of five loess sections in Shanxi Province, China, it was found that the concentrations of the major greenhouse gases CO₂, CH₄ and N₂O in loess-paleosol sequences are generally high, even sometimes may be several times or scores of times higher than their atmospheric concentrations respectively. Although the CO₂ concentration in the same loess section shows poor regularity among different layers, it increases slowly from north to south in space. The CH₄ concentration in the layers under Malan Loess is much higher than that in the atmosphere, although it is not high in Malan Loess. Most of the δ¹³C values of CO₂ in loess are -11.14‰—15.48‰ (relative to PDB standard). Analysis of carbon isotopic compositions of CO₂ indicates that the main source of CO₂ in loess section is decomposition of ‘stable’ organic matters by microbes. The δ¹³C_g of CO₂ is a little heavier than organic source for exchanging carbon isotope with carbonate in loess. The abundant carbonate in loess not only makes the loess a huge carbon reservior but also adjusts     

Methane emissions from wetlands on the Qinghai-Tibet Plateau

The areal extent of cold freshwater wetlands on the Qinghai-Tibet Plateau (QTP) is estimated at 0.133 × 10⁶ km², suggesting a significant methane potential. Methane fluxes from wet alpine meadows, peatlands,Hippuris vulgaris mires and secondary marshes were 43.18, 12.96, −0.28 and 45.90 mg · m⁻² · d⁻¹, respectively based on the transect flux studies at the Huashixia Permafrost Station (HPS) from July to August 1996. Average CH₄ fluxes in the thaw season were extrapolated at 5.68 g · m⁻² according to the areal percentage of wetland areas in the Huashixia region. The CH₄ fluxes at four fixed sites, representative of similar ecosystems, ranged from −19.384–347.15 mg · m⁻² · d⁻¹, and the average CH₄ fluxes varied from 6.54 to 71.97 mg · m⁻² · d⁻¹ at each site during the observation period from April to September 1997. The CH₄ emissions at each site during the entire thaw season was estimated from 1.21 to 10.65 g · m⁻², displaying strong spatial variations. Seasonal variations of CH₄ fluxes also were observed at four sites: CH₄ outbursts occurred upon the spring thaw in May and June, CH₄ fluxes increased afterwards with rising soil temperatures. Episodic fluxes were observed in summer, which influenced the average CH₄ fluxes considerably. Annual CH₄ emissions from cold wetlands on the QTP were estimated at about 0.7–0.9 Tg based on the distribution of wetlands, representative CH₄ fluxes, and number of thaw days. The centers of CH₄ releasing were located in the sources of the Yangtze and Yellow rivers, and Zoigê Peatlands.     

Impact of technology advances on China’s CO2 emission reduction

Global warming tends to be the major characteristics of the dramatic global climate change. To deal with these changes, the impact of reducing greenhouse gas (GHG) emission on Chinese future economic and social development has to be assessed. In this paper, a Regional Integrated model of Climate and the Economy (RICE), which is well known and accepted widely, has been used for Chinese economic assessment of climate change after introduction, assimilation and verification. Based on a sensitivity analysis of technical parameters in the RICE model and constrained targets proposed for energy saving and emissions reduction technological advance programs of China from 2000 to 2050, the economic impact of the programs is examined. The results indicate that when technology advances, Chinese CO₂ emission, climate loss, and the growth rate of atmospheric CO₂ concentration and temperature will all decrease. It is assumed that in 2010, the CO₂ emission is 20% lower than in 2005, CO₂emission in 2050 would only double the level in 2000, the accumulative CO₂ emission would be decreased by 12.4 GtC, and the atmospheric CO2 concentration and temperature in 2050 would reduce by 35 GtC and 0.04°C respectively from 2000 to 2050. The accumulative climate loss from 2000 to 2050 will drop down by 4.6 billion dollar, which only accounts for 6% of the global total benefits. However, the economic benefit the developed countries will obtain is 10 times that for China under such a technological advance scenario. The decrease of the CO₂ emission control rate is 1% in cooperation policy while 4.6% in non-cooperation policy, which would relieve China’s burden in the control of CO₂ total emission and thereby benefit China in participation of the international cooperation for CO₂ emission reduction.     

Static opaque chamber-based technique for determination of net exchange of CO<Subscript>2</Subscript> between terrestrial ecosystem and atmosphere

Terrestrial carbon cycling is one of the hotspots in global change issues. In this paper, we presented the rationale for determination of net exchange of CO₂ between terrestrial and the atmosphere (NEE) and the methods for measuring several relevant components. Three key processes for determination of NEE were addressed, including the separation of shoot autotrophic respiration from total CO₂ emissions of the ecosystem, the partition of root respiration from soil CO₂ efflux, and the quantification of rhizodeposition C from NPP. With an understanding of the processes involved in the CO₂ exchange between terrestrial and the atmosphere, we estimated NEE of rice ecosystem in Nanjing based on field measurements of CO₂ emissions and several relevant biotic components as well as abiotic factors. The field measurements of CO₂ emissions were made over the rice-growing seasons in 2001 and 2002 with the static opaque chamber method. Calculations indicated that the seasonal pattern of NEE is comparable for two seasons. Either net carbon emission or fractional carbon fixation occurred during 3 weeks after rice transplanting and thereafter net carbon fixation appeared with an increasing trend as rice growing. Higher net carbon fixation occurred in the rice developmental period from elongating to heading. A decline trend in the fixation was documented after rice heading. The mean daily NEE was -6.06 gC·m⁻² in 2001 season and -7.95 gC·m⁻² in 2002 season, respectively. These values were comparable to the results obtained by Campbell et al. who made field measurements with the Bowen ratio-energy balance technique in irrigated rice, Texas USA. Moreover, the mean daily NEE in this study was also comparable to the values obtained from a Japanese rice paddy with the eddy covariance method under the similar water regime, either drainage course or waterlogged. It is concluded that NEE determined by the static opaque chamber method is comparable and in agreement with those measured by Bowen ratioenergy balance and eddy covariance methods.     

Responses of plant rhizosphere to atmospheric CO2 enrichment

Plant root growth is generally stimulated under elevated CO₂. This will bring more carbon to the below-ground through root death and exudate. This potential increase in below-ground carbon sink may lead to changes in long-term soil sequestration and relationship between host plants and symbions. On the other hand, changes in litter components due to the changes in plant chemical composition may also affect soil processes, such as litter decomposition, soil organic matter sequestration and hetero-nutritional bacteria activities. These issues are discussed.     

Stimulation by ammonium-based fertilizers of methane oxidation in soil around rice roots

Methane is involved in a number of chemical and physical processes in the Earth's atmosphere, including global warming. Atmospheric methane originates mainly from biogenic sources, such as rice paddies and natural wetlands; the former account for at least 30% of the global annual emission of methane to the atmosphere. As an increase of rice production by 60% is the most appropriate way to sustain the estimated increase of the human population during the next three decades, intensified global fertilizer application will be necessary: but it is known that an increase of the commonly used ammonium-based fertilizers can enhance methane emission from rice agriculture. Approximately 10-30% of the methane produced by methanogens in rice paddies is consumed by methane-oxidizing bacteria associated with the roots of rice; these bacteria are generally thought to be inhibited by ammonium-based fertilizers, as was demonstrated for soils and sediments. In contrast, we show here that the activity and growth of such bacteria in the root zone of rice plants are stimulated after fertilization. Using a combination of radioactive fingerprinting and molecular biology techniques, we identify the bacteria responsible for this effect. We expect that our results will make necessary a re-evaluation of the link between fertilizer use and methane emissions, with effects on global warming studies.     

Changes of photosynthetic capacity of some plant species under very high CO2 concentrations in Biosphere 2

Conclusions The initial slope of A/ light curve became steep under high CO₂ (700 μmol · mol^-1) compared with that under low CO₂ (350 μmol · mol^-1) for the C₃ species growing in very high CO₂(>2 200 μmol · mol^-1) for a long period. The light compensation points remained unchanged, but the light saturation points were found increased. The ϕ_m,_app and A_max of the C₃ species increased respectively by 79 % and 80 %, while those of C₄ species decreased by 10% and 14%, respectively. The shape of A/light curve of C₄ species did not change. Such results indicated that C₃ species increased the capacity of photosynthesis, while C₄ did not change, otherwise it decreased a little. This work only compared the changes of capacity in photosynthesis of some species under different CO₂ levels in Biosphere 2. We need further investigation on the effects of high CO₂ on the same species outside Biosphere 2, in order to fully undertand the effects and mechanism of response of plants to the elevated CO₂.     

CO2/H2S共存条件下集输管道选材的新方法及应用

在CO₂/H₂S共存条件下集输管道中,管道发生腐蚀的可能性急剧增大,因此集输管道的选材至关重要。若选择管材级别较低,则会严重影响管道的正常生产;若管材级别较高,会引起经济成本的浪费。为了使集输管道在CO₂/H₂S共存条件下选材更加合理。在CO₂/H₂S共存腐蚀速率预测模型的基础上,提出了一种新的集输管道选材方法,新方法的步骤为：计算材质的均匀腐蚀速率,腐蚀速率应满足NACE 标准中腐蚀速率的控制值(小于0.076mm/a),结合管道的设计寿命、剩余强度和经济性评价,确定在CO₂/H₂S共存体系下集输管道的材质。以某油田集输管道为示例,根据新方法选择的材质与实验得到的管材结果一致,验证了新方法的准确性。集输管道选材新方法在保证集输管道安全运行的前提下,能够有效降低管材质选择的成本,有利于保证集输管道的安全性和经济性。     

Vegetation evolution on the central Chinese Loess Plateau since late Quaternary evidenced by elemental carbon isotopic composition

There are many controversial issues in loess studies such as natural vegetation types on the Chinese Loess Plateau during the historical periods and the spatial and temporal evolution of C3/C4 plants. Elemental carbon isotopic composition （δ^13Cec） in the loess section may offer new evidence for these problems. Elemental carbon （EC） is produced by incomplete combustion of vegetation, and its carbon isotopic composition has a very small difference from that of the formal vegetation, then δ^13Cec can be used as a record to recover the changes of vegetation. Elemental carbon was extracted by applying the oxidation method from the Ioess-paleosol sequence in the central Chinese Loess Plateau, and its car- bon isotope composition was analyzed by the isotope mass spectrometer. The results showed that the vegetation in this region was a mixed type of C3 and C4 plants, dominated with C3 plants in most of the time. Since late Quaternary, C3/C4 plants may not follow a simple glacial-interglacial cycle mode on the Chinese Loess Plateau, but showing fluctuations. C3 plants increased gradually in L4 period, and more C3 plants occurred during $3 period, and C4 plants increased again during L3-- L2 periods, after that, Cs plants dominated again during S1 --S0 periods. During periods of paleosol development, C3 plants were abundant in S3 and S1, and there were more Ca plants in S2 and SO. During periods of loess sedimen- tation, there were more C3 plants in L4 and L1, and there were more C4 plants in L3 and L2. On the orbital timescale, the vegetation variations revealed by δ^13Cec record are consistent with the results of pollen data and also similar to the results obtained by organic carbon isotopic composition since the last glacial period.     

亚高山红桦根及根际土壤生化特性对升高温度和CO2的响应

通过川西亚高山野外大型控制实验,研究了红桦不同密度下的根系生物量、根际土壤微生物数量和根际土壤酶活性对短期升高温度（ET,相对室外平均升温2.4±0.4 ℃）、升高大气CO2浓度（EC,平均增加15.5±1.0 μmol·L^-1）及交互作用（ETC,生长室相对室外平均升温2.2±0.5　℃并CO₂浓度平均增加15.8±1.2　μmol·L^-1）的响应.初步结果表明：升高大气温度或CO₂浓度均能够显著促进红桦低密度和高密度下单株根系生物量;升高温度和CO₂浓度及二者共同升高对微生物类群和数量影响不同,升高温度细菌、真菌数量以及低密度下放线菌数量显著增加,而高密度下放线菌数量显著下降;升高CO₂浓度下高密度时细菌和真菌数量增加而低密度下均显著下降;升高温度（ET）显著抑制高、低密度下红桦根际土壤多酚氧化酶活性,升高CO₂（EC）根际土壤过氧化氢酶活性在2种密度条件下均不同程度升高,土壤脲酶和多酚氧化酶活性则降低;ETC条件下,根际土壤多酚氧化酶和过氧化氢酶在2种密度下均表现出不同程度的降低,但脲酶活性在高、低密度条件下对ETC表现出不同的响应结果.     

挥发性油藏酸气回注的最小混相压力与组分优化

高含H_2S和CO_2酸性气体的低渗透挥发性油藏在开发过程中,H_2S和CO_2会以溶解气的形式被采出,并占有较高的摩尔分数。分离器条件下的气态轻烃通过回注地层,在油藏压力高于最小混相压力(MMP)时达到混相驱动,一方面可以显著提高驱油效率,另一方面可以起到减缓压力衰竭的目的。H_2S和CO_2作为污染气体,分离和回收成本较高;而与烃气一同回注地层势必会对MMP产生影响。因此,需要研究酸性气体对溶解气回注MMP的影响规律并且合理地优化回注气组分。在对目标区块原油组分拟合重组的基础上,通过混合单元格法预测MMP,研究了溶解气主要组分的混相能力以及H_2S和CO_2对烃气驱MMP的影响规律,通过正交试验方法优化了注入气比例。结果表明:作为酸性杂质气体H_2S和CO_2具有较强的混相能力,可以降低注气MMP;最优注气形式为溶解气直接回注地层。     

光电催化还原CO2金属氧化物催化材料研究进展

光电催化还原CO₂在众多减排技术中因其洁净环境友好成为研究热点。通过对比光催化,电催化和光电催化的原理,论证光电催化还原CO₂在节能减排领域的应用价值。以Ti,Zr,Fe,Cu为基本元素的4个催化材料体系为研究对象,对同一体系不同催化材料从材料合成方法,合成难易程度,催化效率,选择性和催化能耗等不同方面做出综合比较和评价,并对光电催化还原CO₂的研究方向和应用前景作出了展望。     

CO2和O2共注入下方解石溶解对黄铁矿氧化固铀的影响

我国大型可地浸砂岩型铀矿床普遍存在黄铁矿和方解石与铀矿物密切共生现象。中性地浸采铀过程中O₂和CO₂的共注入会诱导黄铁矿氧化和方解石溶解,目前针对二者共存体系中方解石溶解对黄铁矿氧化固铀的影响尚不明确。本文通过静态批实验和数值模拟的方法对比研究了CO₂和O₂条件下方解石溶解对黄铁矿氧化固铀的影响。结果表明:无CO₂分压下中性Tris缓冲体系中黄铁矿氧化对U(VI)的吸附率高达90%,有CO₂分压下碳酸铀酰体系中铀的固定率明显降低,约有32%的铀被吸附。在方解石和黄铁矿共存体系中,单独通O₂条件下铀的吸附率为27%,CO₂和O₂共通时黄铁矿氧化对铀的吸附率仅为2%,结合数值模拟结果表明O₂₊黄铁矿+方解石体系和CO₂₊O₂₊黄铁矿+方解石体系中Ca₂(UO₂)(CO₃)₃质量比分别为80%和95%。X射线衍射(X-ray diffraction,XRD)、X射线光电子能谱(X-ray photoelectron spectroscopy,XPS)和傅里叶红外光谱(Fourier transform infrared,FT-IR)结果表明黄铁矿表面发生微氧化形成针铁矿和纤铁矿会增加U(VI)的吸附,方解石溶解促进Ca-UO₂-CO₃络合物的形成影响了黄铁矿及其氧化产物对U(VI)的固定,提高了U(VI)的迁移能力。     

Re-examining the reliability of tree-ring isotope ratio as a historical CO2 proxy

To examine the reliability of using tree ring δ¹³C and the model of isotopic fractionation in reconstructing atmospheric CO₂ levels, we studied the variations of some important parameters of several subtropical species under natural field conditions. It was found that, different from other researchers’ results, leaf conductance to CO₂ transfer, g, did not change in proportion to the change in rate of CO₂ assimilation, A, with the result that intercellular concen- tration of CO₂, C_i, could not keep constant. Thus, we conclude that the use of tree-ring isotope ratios in the reconstruction of atmospheric CO₂ variation based on the presupposition that C_i keeps constant during assimilation is not reliable under current circumstances.     

层状化合物K0.81Li0.27Ti1.73O4的合成

研究以K₂CO₃,Li₂CO₃和TiO₂为反应原料合成层状钛酸盐K_0.81Li_0.27Ti_1.73O₄过程中合成条件对产物的影响. 结果表明: 反应温度在
1 000~1 200 ℃, 反应原料配比为n(K₂CO₃) ∶n(Li₂CO₃) ∶n(TiO₂)=(0.405~0.42) ∶(0.135~0.165) ∶1.73时, 均可以得到产物K_0.81Li_0.27Ti_1.73O₄, 延长反应时间及升高反应温度均有利于产物的生成; 在1 200 ℃高温条件下, 使用刚玉坩埚为反应容
器时, 最佳的反应条件是： 反应温度为1 100 ℃, 反应原料配比为n(K₂CO₃) ∶n(Li₂CO₃) ∶n(TiO₂)=0.405 ∶0.135 ∶1.73, 反应24 h.     

δ13C difference between plants and soil organic matter along the eastern slope of Mount Gongga

Carbon isotope ratios (δ¹³C) of plants, litter and soil organic matter (0–5 cm, 5–10 cm and 10–20 cm) on the eastern slope of Mount Gongga were measured. The results show that δ¹³C values of plants, litter and soil organic matter all decrease first and then increase with altitude, i.e δ¹³C values gradually decrease from 1200 to 2100 m a.s.l., and increase from 2100 to 4500 m a.s.l. The δ¹³C altitudinal variations are related to the distribution of C₃ and C₄ plants on the eastern slope of Mount Gongga, because C₄ plants are observed to grow only below 2100 m, while C3 plants occur at all altitudes. There are significantly positive correla-tions among δ¹³C of vegetation, δ¹³C of litter and δ¹³C of soil organic matter, and litter, 0–5 cm, 5–10 cm and 10–20 cm soil or-ganic matter are 0.56‰, 2.87‰, 3.04‰ and 3.49‰ greater in δ¹³C than vegetation, respectively. Considering the influences of rising concentration of atmospheric CO₂ and decreasing δ¹³C of atmospheric CO₂ since the industry revolution on δ¹³C of plants, 1.57‰ is proposed to be the smallest correction value for reconstruction of paleovegetation using δ¹³C of soil organic matter.     

Fractal analysis for root growth of plant seedlings under doubled CO2 concentration

Fractal geometry was applied and box dimension was used as an indicator to analyze the effects of doubled CO₂ concentration on the root growth of plant seedlings. Results showed that doubled CO₂ concentration displayed different effects on root branching characteristics of C₃ and C₄ plants. There was an obvious increase of root branches in spring wheat while there were no significant effects on roots of sweet sorghum. In different soil layers, root branching of spring wheat was stimulated and this promotion was most significant in the second layer (10–20 cm), which denoted that elevated CO₂ altered the root branching pattern. That means higher CO₂ concentration influences not only root growth but also its differentiation and development.     

Pedogenic carbonate isotope record of vegetational evolution since late Miocene in Loess Plateau

Isotopic analyses for paleovegetational evolution have been carried out on samples of the pedogenic carbonate nodules in the Red Clay-Loess sequence at Lingtai (35°N), the Loess Plateau. Stable carbon isotopic composition indicates that ( i ) C4 plants might be present at least by7.0 Ma; ( ii ) C4 plants expanded gradually between ～4.0 and ～3.2 Ma, and their biomass fraction was up to 50% ; and (Ⅲ ) the biomass of C4 vegetation since ～2.0 Ma seems to have been decreased to the level (about 20%) before 4.0 Ma. C4 plant expansion at Lingtai cannot be fully understood with the "global C4 expansion" model because it occurred much later up to 3.0 Ma than in Pakistan, which indicates that some changes in the regional climatic system may also contribute to C3/C4 shift except changes in atmospheric CO2 concentrations and temperature. The latitudinal zone for C3/C4 transition seems to move southwards slightly in East Asia, compared with the case in North America where 37°N癗 is the ideal boundary for the C4 expansion.     

CO<Subscript>2</Subscript> gas emplacement age in the Songliao Basin: Insight from volcanic quartz <Superscript>40</Superscript>Ar-<Superscript>39</Superscript>Ar stepwise crushing

Due to a lack of suitable minerals, the gas/oil emplacement ages have never been accurately obtained before. CH₄-CO₂-saline- bearing secondary inclusions are found in quartz from the volcanic rocks of the Yingcheng Formation, the container rocks of the deep CO₂ gas reservoir in the Songliao Basin. The inclusion fluid was trapped into microcracks in quartz during the gas emplacement and accumulation, providing an optimal target for the ⁴⁰Ar-³⁹Ar stepwise crushing technique to determine the CO₂ gas emplacement age. ⁴⁰Ar-³⁹Ar dating results of a quartz sample by stepwise crushing yield a highly linear-regression isochron with an age of 78.4±1.3 Ma, indicating that the accumulation of the deep CO₂ gas reservoir in the Songliao Basin occurred in the late Cretaceous. This is the first time to report an exact isotopic age for a CO₂ gas reservoir, which indicates that the ⁴⁰Ar-³⁹Ar dating can serve as a new technique to date the oil/gas emplacement ages.