Development Of City Size Distributions For The Egyptian Urban System, 1897–1960 1

Two scenarios of CO₂-induced climatic change and projections of population and consumptive use of water to the year 2035 are utilized in a climate impact assessment of future water resources in the Great Lakes basin. When expressed as a streamflow/population index, results indicate a sharp decline of this index. Future index values are projected to be similar to those presently recorded for the Colorado River basin.     

大气CO2浓度变化与全球气候变化关系初步探讨

2007年IPCC公布的第四次评估报告AR4指出：过去50a观测到的地球平均温度升高很可能（90％以上）是由人类活动引起的,其中主要是人类活动引起的温室气体排放的增加．而地质气候记录证明,早在人类排放能够影响大气以前的CO2浓度变化均不同程度地滞后于气温变化．地质时期CO2浓度的波动是跟随气候变化而变化,是被大气温度驱动的结果,而非相反的CO,驱动温度变化．将现在全球变暖完全归因于人类排放CO2的增加,无法解释1940-1978年的降温事件．通过更长尺度的对比研究可以发现,现在气候是处于全新世变干变冷的大趋势之中,即使现在全球略有变暖,也只是处于变干变冷大趋势中的次级变暖波动．将近代全球气候变暖片面夸大归因于人类活动排放温室气体,而忽略了自然因素的贡献,其依据显得缺乏科学说服力,其做法不免有些令人担忧．     

Impacts of CO2 Enrichment on Water Use Efficiency in Terrestrial Ecosystems: A Meta-analysis of Experimental Manipulations

Elevated CO₂ (eCO₂) has important impacts on plants, especially on water use efficiency (WUE). A meta-analysis was performed to determine the responses of WUE to enriched CO₂. We summarized 242 studies on WUE research under ambient and enriched CO₂ conditions that were published between 1989 and 2019. Our results showed that WUE had positive responses to elevated CO₂ with an increase of about 46% and high heterogeneity. Elevated CO₂ increased leaf, grain, biomass and whole plant WUE by 76%, 9%, 30% and 37%, respectively. The effect size on leaf WUE was higher than the other three WUE types, and the effect size on whole plant WUE was higher than grain WUE (P<0.05). In another respect, the response of WUE in forests was higher than in cropland (P<0.05). Regarding different experimental methods, WUE had a stronger response to elevated CO₂ by the method of climate-controlled chamber than by the methods of OTC (Open Top Chamber) or greenhouses (P<0.05). However, the effect size obtained by the method of greenhouse was higher than that obtained by the methods of either OTC or climate chamber for whole plant WUE (P<0.05). Furthermore, our results found WUE had a positive linear relationship with the magnitude of CO₂ enrichment (P<0.05). Meanwhile, the effect size of elevated CO₂ on grain WUE had a positive linear relationship with the duration of CO₂ enrichment. This study found that the impacts of CO₂ enrichment on WUE are unique and specific for different WUE types and the various experimental conditions.     

Temperature coefficient of seawater pH as a function of temperature,pH, DIC and salinity

pH is a measure of the hydrogen ion activity in a solution, which is a function of temperature. Under normal seawater conditions, it is well constrained. Nowadays, with an increasing interest in complex environments(e.g.,sea ice), a better understanding of the temperature change on pH under extreme conditions is needed. The objective of this paper was to investigate the temperature coefficient of the seawater pH(?pH/?T) over a wide range of temperature, pH, dissolved inorganic carbon(DIC) and sa...     

Effect of water excess on soil carbon dioxide,seepage water chemistry,and calcite speleothem growth: An experimental and modelling approach

The effect of the water excess in soil on soil gaseous carbon dioxide concentrations (c_CO2) was studied based on field experiments. The gradual water addition of 15 and 30 L m⁻² to leptosols and anthrosols, simulating 15 and 30 mm precipitation, respectively, caused the overall c_CO2 increase of 1.53 × 10⁻¹ mol m⁻³ (increase by 60%) and 1.61 × 10⁻¹ mol m⁻³ (increase by 112%) in the soil airs. The effect of the c_CO2 increment on seepage water, cave dripwater chemistry, and calcite speleothem overgrowths was deduced from geochemical modelling. It showed that the c_CO2 increments may lead to the increments in total dissolved carbon, aqueous calcium, and dissolved solids of 1.10 × 10⁻³ mol L⁻¹ (increase by 35%), 4.45 × 10⁻⁴ mol L⁻¹ (increase by 30%), and 1.55 × 10⁻³ mol L⁻¹ (increase by 34%), respectively. After the total degassing of CO₂ in the cave, the increment in the saturation index of dripwater, SI, could reach up to ΔSI = 0.31, which means an increase by hundreds of percent. The water excess of 5 L m⁻² following a dry period would cause the increment in saturation index ΔSI = 0.17. The modelling further showed that the c_CO2 increase associated with the 30 L m⁻² water excess could induce the calcite overgrowth up to 1 μm thick per 1 m² surface area. The effect of water excess with additional water supplies gradually weakens, probably due to reduced CO₂ diffusivity and soil microorganism activity. It can be assumed that the most contrasting peaks in dripwater chemistry are associated with the individual precipitation events after short dry periods. The increased supersaturation of dripwater is expected to lead to faster growth of speleothem and changes in calcite textures.     

Aptian palaeoclimates and identification of an OAE1a equivalent in shallow marine environments of the southern Tethyan margin: Evidence from Southern Tunisia (Bir Oum Ali section,Northern Chott Chain)

Alternations between siliciclastic, carbonate and evaporitic sedimentary systems, as recorded in the Aptian mixed succession of southern Tunisia, reflect profound palaeoceanographic and palaeoclimatic changes in this area of the southern Tethyan margin. The evolution from Urgonian-type carbonates (Berrani Formation, lower Aptian) at the base of the series, to intervals dominated by gypsum or detrital deposits in the remainder of the Aptian is thought to result from the interplay between climate change and tectonic activity that affected North Africa.Based on the evolution of clay mineral assemblages, the early Aptian is interpreted as having been dominated by slightly humid conditions, since smectitic minerals are observed. Near the early to late Aptian boundary, the onset of a gypsiferous sedimentation is associated with the appearance of palygorskite and sepiolite, which supports the installation of arid conditions in this area of the southern Tethyan margin. The evaporitic sedimentation may have also been promoted by the peculiar tectonic setting of the Bir Oum Ali area during the Aptian, where local subsidence may have been tectonically enhanced linked to the opening of northern and central Atlantic. Stress associated with the west and central African rift systems may have triggered the development of NW–SE, hemi-graben structures. Uplifted areas may have constituted potential new sources for clastic material that has been subsequently deposited during the late Aptian.Chemostratigraphic (δ¹³C) correlation of the Bir Oum Ali succession with other peri-Tethyan regions complements biostratigraphic findings, and indicates that a potential expression of the Oceanic Anoxic Event (OAE) 1a may be preserved in this area of Tunisia. Although the characteristic negative spike at the base of this event is not recognized in the present study, a subsequent, large positive excursion with δ¹³C values is of similar amplitude and absolute values to that reported from other peri-Tethyan regions, thus supporting the identification of isotopic segments C4–C7 of the OAE1a. The absence of the negative spike may be linked to either non preservation or non deposition: the OAE1a occurred in a global transgressive context, and since the Bir Oum Ali region was located in the innermost part of the southern Tethyan margin during most of the Aptian, stratigraphic hiatuses may have been longer than in other regions of the Tethys. This emphasizes the importance of integrating several stratigraphic disciplines (bio-, chemo- and sequence stratigraphy) when performing long-distance correlation.     

Albian oceanic anoxic events in northern Tunisia: Biostratigraphic and geochemical insights

Albian pelagic successions of the Nebeur area in northwestern Tunisia consist of radiolarian-bearing and organic-rich black shale beds, which represent the lower part of the Fahdene Formation. The carbonate content of the organic-rich beds ranges between 40 and 48%. Total organic carbon (TOC) analyses via Rock Eval pyrolysis yielded values ranging between 0.7 and 2.8% and a mixed marine/terrestrial origin. T_max values vary between 424 and 450 °C, indicative of submature to mature organic matter. High resolution planktic foraminiferal and radiolarian biostratigraphy suggest that the black shales beds span the mid- to late Albian, confined to the middle part of the Ticinella primula zone, upper Biticinella breggiensis zone and lower appeninica + buxtorfi zone. Episodes of organic-rich deposition in the “Tunisian Trough” are interpreted as being the sedimentary record of the global oceanic anoxic events OAE1b, c, and d respectively. Age-diagnostic radiolarian assemblages recovered from late Albian organic-rich black shales lie within the UA13–UA14 boundary biochronozones. The abundance of radiolarian and calcispheres (i.e. pithonella) within the black shales suggests high productivity periods and eutrophic conditions probably triggered by upwelling currents.     

双叶模型在冬小麦田冠层CO2通量多层模拟中的应用

综合考虑农田生态系统中水、热、CO2输送所涉及的大气、水文、生物等生物物理过程,以Farquhar等提出的叶片尺度光合作用生物化学过程机理模型为理论基础,对其进行空间尺度扩展,并改进冠层分层方法,建立了均匀农田与大气之间物质输送和能量交换的多层模式,在模式中运用双叶模型,同时考虑叶片氮素水平垂直差异,对2008年4—5月华北平原冬小麦生长旺季农田生态系统中冠层CO2通量进行了模拟研究,并利用涡度相关观测的通量数据对模型的有效性加以验证,结果表明:在冠层多层空间,小麦拔节至孕穗期和开花至乳熟期叶片氮含量随冠层高度的衰减系数分别为0.793(R2=0.698)和1.374(R2=0.728),冠层内叶片氮含量的空间分布可以用以相对累积叶面积指数为自变量的函数来描述;模型分别计算各层阴、阳叶的光截取、气孔传导、光合作用等,最终计算冠层上方CO2通量,冬小麦农田净生态系统生产力模拟值与实测值相关显著(R2=0.78),模拟的CO2通量日变化特征晴天昼间比阴雨天和夜间的效果好;在考虑丛聚影响的叶片非随机分布的密集农田中,阴叶对总初始生产力的贡献率在35.7%左右,对生产力贡献很重要。分层统计显示,作物最终产量的形成主要...     

Capturing and storage of CO<Subscript>2</Subscript> by micron-nano minerals: Evidence from the nature

The increase of CO2 in atmosphere is a main factor leading to "greenhouse effect", which causes more and more serious global environmental problems. The reduction of CO2 is a challenge for the survival of human beings, and it is also a big technical problem. CO2 fluid-rock interaction is a key scientific problem involved in geo-logical storage. The CO2 fluid-rock interaction has a variety of multi-scale changes. Due to great differences in the quantity of surface atoms and surface energy between micron-nano-sized minerals, and ions and crystals, the speed and efficiency of CO2 fluid-rock interaction on a micron-nano scale are much higher than those on other scales. As is known from the natural world, the micron-nano structures of pores and the surface chemical modification of natural porous minerals (zeolite, diatomite, sepiolite, palygorskite, halloysite, etc.) should be further investigated, which can be used as the micron-nano -mineral porous materials with high capacity and high efficiency for capturing CO2. Through simulating the adsorption capacity and process of CO2 by minerals in the natural world, the micron-nano technology is applied to calcium- and magnesium-based minerals (olivine, pyroxene, feldspar, clay, etc.) so as to improve the activity of calcium and magnesium and enlarge the reaction contact area. In this way, the efficiency of capturing and storage of CO2 by calcium- and magnesium-based minerals can be greatly improved. These minerals can also be used as the micron-nano-mineral materials with large capacity and high efficiency for capturing and storing CO2.