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991.
It has been suggested that part of the so-called “missing sink” of carbon dioxide introduced into the atmosphere by anthropogenic
activities, that is the imbalance between estimated anthropogenic carbon dioxide emissions and oceanic uptake, may be stored
in the vegetation in midlatitudes. Precise mechanisms of abstraction of additional carbon dioxide by vegetation, also known
as the “fertilization effect”, are poorly understood. Stable carbon and hydrogen isotope ratios of cellulose extracted from
annual growth rings (covering the time period 1980–1993) in an oak tree from Kalamazoo, SW Michigan provide a basis to investigate
at a physiological level how the fertilization effect may operate. The carbon isotope ratios show that the intercellular concentration
of carbon dioxide increased due to an increase in stomatal opening. Although increased intercellular concentration of carbon
dioxide translated to increased Water Use Efficiency and assimilation rates, it also resulted in increased transpiration rate
as shown by higher D/H of the fixed carbon. The two-fold significance of the isotope data are: first, they provide the first
field evidence based on isotope studies for excess CO2 induced biomass production and second, they suggest that this mechanism is likely to operate only in limited environments.
Vegetation in regions where moisture availability is not restricted so that there can be a gain in water use efficiency despite
increased leaf evaporation are best suited to sequester excess carbon from the atmosphere. 相似文献
992.
白云鄂博富稀土元素碳酸岩墙的
碳和氧同位素特征 总被引:7,自引:0,他引:7
重点解剖了一条距白云鄂博超大型REE-Nb-Fe矿床东矿北东方向2 k m、切割白云鄂 博群H1及H3岩性段的细粒方解石碳酸岩岩墙的碳和氧同位素地球化学特征。结果表明,碳酸 岩的碳同位素组成变化范围较小(δ13C值为-6.6‰ ~ -4.6‰),与正常地幔碳δ 13C值-5±2‰一致;而氧同位素组成变化范围较大(δ18O值为11.9‰~17.7‰ ),显著高于地幔的δ18O值5.7±1.0‰,表明碳酸岩浆在结晶过程中或之后曾与 低 温热液流体发生了同位素交换。碳酸岩墙中白云石与方解石之间的碳和氧同位素分馏均小于 0‰,处于不平衡状态,说明该碳酸岩墙中的白云石与方解石并非同成因矿物,白云石可能 为次生成因的。 相似文献
993.
湖北宜昌地区寒武系—下奥陶统的碳氧同位素记录 总被引:10,自引:0,他引:10
对宜昌地区寒武系和下奥陶统的碳酸盐碳、氧同位素进行测定,所得δ18O大 于-10‰且与δ13C不相关,表明研究区碳酸盐样品基本上保存了碳、氧同位素的初 始比值。δ18O在白云岩样品中呈现正漂移而在非白云岩样品中呈现负漂移,认为δ 18O反映海水古盐度变化,即δ18O随着古盐度升高而增大;δ13 C在缺氧沉积物中呈现负漂移,但负漂移的δ13C却不限于缺氧沉积物,推测δ13 C可能反映古海洋的初级生产力,即δ13C随着初级生产力的提高而降低。研究还指 出,由于Z值与δ13C密切正相关(相关系数为0.99),综合运用δ18O和δ 13C的经典盐度公式不适用于研究区古盐度环境的重建。 相似文献
994.
The CO2-rich thermal groundwater in the Betic Cordilleras in Spain has been studied with regard to the geological and hydrogeological
setting, physical and chemical characteristics, and 13C-isotope content. The study area is about 60 km northeast of Almería city, in southeastern Spain. The thermomineral waters
are plentiful and are related to regional geothermal anomalies. Temperatures of 20 −41°C, high bicarbonate concentrations
(183–1824 mg/L), and high amounts of PCO2 (<1.1 bar) characterize the groundwater. CO2 spatial variations are related to proximity to the Carboneras, Palomares, and Guadalentín fault systems, which may be the
surface representation of the zone of crustal thinning and magmatism. δ
13C values probably indicate a deep source for the CO2, either the mantle or perhaps carbonate rocks in the metamorphic substratum. The high amount of CO2 in the groundwater causes problems in wells and severely restricts water usage. The hydrothermal features of this area are
probably related to neotectonic activity.
Received, September 1998/Revised, June 1999, September 1999/Accepted, December 1999 相似文献
995.
The responses of the climate system to increase of atmospheric carbon dioxide(CO2)arestudied by using a new version of the Bureau of Meteorological Research Centre(BMRC)globalcoupled general circulation model(CGCM).Two simulations are run:one with atmospheric CO2concentration held constant at 330 ppm,the other with a tripling of atmospheric CO2(990 ppm).Results from the 41-year control coupled integration are applied to analyze the mean state,seasonal cycle and interannual variability in the model.Comparisons between the greenhouseexperiment and the control experiment then provide estimations of the influence of increased CO2on climate changes and climate variability.Especially discussed is the question on whether theclimate changes concerned with CO2 inerease will impact interannual variability in tropical Pacific,such as ENSO. 相似文献
996.
The responses of the climate system to increase of atmospheric carbon dioxide(CO_2)arestudied by using a new version of the Bureau of Meteorological Research Centre(BMRC)globalcoupled general circulation model(CGCM).Two simulations are run:one with atmospheric CO_2concentration held constant at 330 ppm,the other with a tripling of atmospheric CO_2(990 ppm).Results from the 41-year control coupled integration are applied to analyze the mean state,seasonal cycle and interannual variability in the model.Comparisons between the greenhouseexperiment and the control experiment then provide estimations of the influence of increased CO_2on climate changes and climate variability.Especially discussed is the question on whether theclimate changes concerned with CO_2 inerease will impact interannual variability in tropical Pacific,such as ENSO. 相似文献
997.
西江流域的有机碳侵蚀通量 总被引:12,自引:1,他引:11
在西江下游的马口水文站对径流进行了4个季节的有机碳采样分析。研究表明,西江径流有机碳的断面构成在各个季节均较为一致;季节性变化表现为,有机碳和悬浮物含量随流量的增加而增加。随着水体悬浮物含量的增加,悬浮物的有机碳含量呈对数趋势降低。西江流域的有机碳侵蚀通量为10.18×106gC/km2·yr.,是全球外流域有机碳侵蚀通量的2~3倍,其中以颗粒有机碳的侵蚀通量为主,达到8.30×106gC/km2·yr.,溶解有机碳的侵蚀通量为1.88×106gC/km2·yr.。反映了流域内较强的机械剥蚀过程,这与西江流域典型的季风气候、较大的地形高差,以及农业耕作历史长久、土地利用强度较大等因素有关。 相似文献
998.
通过对湖北清江和尚洞HS - 2号石笋的沉积特征及碳、氧同位素特征分析, 利用U系法定年, 获取了湖北地区19.0~6.9ka的古气候、古环境信息(平均分辨率为17a, 局部分辨率达到7a).得出如下结论: (1) 19.0~16.6ka, C, O同位素偏轻, 气候冷湿; (2) 16.6~11.1ka, C, O同位素偏重, 气候干热; (3) 11.1~10.3ka干热时期中的突然回冷事件对应于新仙女木事件; (4) 10.3~6.9ka气候温和, 雨量较丰, 后期逐渐变冷.反映了历史时期湿冷、干热、温暖交替变化的气候趋势, 得出了千年级和百年级的一些气候变化趋势 相似文献
999.
N. Ramaiah V. V. S. S. Sarma Mangesh Gauns M. Dileep Kumar M. Madhupratap 《Journal of Earth System Science》2000,109(4):443-451
Bacterial abundance and production, numbers, sizes and concentrations of transparent exopolymer particles (TEP) and total
organic carbon (TOC) were measured during the 1996 summer monsoon to understand the relationship between TEP, the most labile
particulate organic carbon, and bacteria. While high regional variability in the vertical distribution of TOC was discernible,
TEP concentrations were high in surface waters at 18–20°N along 64°E with concentrations well over 25 mg alginic acid equivalents
I−1 due to upwelling induced productivity. Their concentrations decreased with depth and were lower between 200 and 500 m. Bacterial
concentrations were up to 1.99 × 108 I–1 in the surface waters and decreased by an order of magnitude or more at depths below 500 m. A better relationship has been
found between bacterial abundance and concentrations of TEP than between bacteria and TOC, indicating that bacterial metabolism
is fueled by availability of TEP in the Arabian Sea. Assuming a carbon assimilation of 33%, bacterial carbon demand (BCD)
is estimated to be 1.017 to 4.035 g C m–2 d–1 in the surface waters. The observed TEP concentrations appear to be sufficient in meeting the surface and subsurface BCD
in the northern Arabian Sea. 相似文献
1000.
微量金化学光谱法标准系列配制及活性炭处理的改进 总被引:2,自引:0,他引:2
对微量金化学光谱法中活性炭自理及标准系列配制的方法进行了探索,改进了微量金化学光谱法活性炭处理及标准系列配制。将该法配制的标准系列应用于微量金化光谱测定,提高了分析结果的准确度。用标准试样分析及原子吸收(AAS)法验证,结果与标准值及AAS法相符。 相似文献