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81.
Emission rates of biogenic volatile organic compounds emitted by the forests were estimated for five geographical regions as well as for all Switzerland. Monoterpene and isoprene emissions rates were calculated for each main tree species separately using the relevant parameters such as temperature, light intensity and leaf biomass density. Biogenic emissions from the forests were found to be about 23% of the total annual VOC emissions (anthropogenic and biogenic) in Switzerland. The highest emissions are in July and lowest in January. Calculations showed that the coniferous trees are the main sources of the biogenic emissions. The major contribution comes from the Norway spruce (picea abies) forests due to their abundance and high leaf biomass density. Although broad-leaved forests cover 27% of all the forests in Switzerland, their contribution to the biogenic emissions is only 3%. Monoterpenes are the main species emitted, whereas only 3% is released as isoprene. The highest emission rates of biogenic VOC are estimated to be in the region of the Alps which has the largest forest coverage in Switzerland and the major part of these forests consists of Norway spruce. The total annual biogenic VOC emission rate of 87 ktonnes y–1 coming from the forests is significantly higher than those from other studies where calculations were carried out by classifying the forests as deciduous and coniferous. The difference is attributed to the high leaf biomass densities of Norway spruce and fir (abies alba) trees which have a strong effect on the results when speciation of trees is taken into account. Besides the annual rate, emission rates were calculated for a specific period during July 4–6, 1991 when a photochemical smog episode was investigated in the Swiss field experiment POLLUMET. Emission rates estimated for that period agree well with those calculated for July using the average temperatures over the last 10 years. 相似文献
82.
粘滑失稳及其物理场时空分布的实验研究 总被引:6,自引:3,他引:6
摩擦滑动的物理场实验研究表明:(1)能量空间分布的差异是失稳的重要条件,单发型大事件常发生于高能量向低能量的突变带或高能量背景区内的相对低能量区;(2)单发型大事件的孕育过程常常经历若干个能量输入输出循环,产生多个前兆阶段,并在失稳前源区常有一个弱化过程。小震或群发型事件失稳前常常只有一个能量积累与强化的过程,失稳前兆阶段性反映较差;(3)粘滑失稳时断层的位错与声发射的大小未见明显关系 相似文献
83.
84.
Séverine Bernardie Jean-Pascal Gilbert François Lebert Hubert Fabriol 《Pure and Applied Geophysics》2007,164(1):177-197
The monitoring of the stability of old mines constitutes an important research objective for our institution, BRGM. The study
reported here shows the contribution of high-frequency (>30 kHz) acoustic emissions to the detection of the damage within
a rock mass, during an experiment within a pilot site of an old flooded iron mine. The experiment consisted of recording all
the hydroacoustic events in a broad frequency band (between 30 Hz and 180 kHz), during 18 months. The monitoring network has
been calibrated by a triggered block fall that made it possible to highlight a relationship between the occurrence of high-frequency/low-frequency
hydroacoustic emissions and rock falls. The events recorded have been associated with the micro-failure of the rock mass near
the roof, prior to the detachment of the blocks. This monitoring showed important high-frequency hydroacoustic activity, which
may be associated with mechanical instabilities generated by the evolution of water pressure during the experiment. In conclusion,
the high-frequency hydroacoustic activity appears to be a good indicator of instability and, therefore, this new technique
constitutes a promising tool for monitoring abandoned underground cavities. 相似文献
85.
电感耦合等离子体原子发射光谱法测定黄铁矿中微量元素 总被引:5,自引:7,他引:5
采用电感耦合等离子体原子发射光谱法检测了黄铁矿中Cd,Co,Cu,Mn,Pb,Zn和Ni。用干扰系数校正法消除黄铁矿中铁对上述元素的干扰,采用HCl-HNO3体系溶解矿样,不需化学分离,直接测定。方法已应用于国家标准物质GBW07267的测定。结果与标准值相符,相对标准偏差(n=8)为1.5%-7.3%。 相似文献
86.
87.
中国南京与美国德克萨斯稻田甲烷排放的比较 总被引:8,自引:0,他引:8
Field measurements of methane emission from rice paddies were made in Nanjing, China and in Texas, USA, respectively. Soil temperature at approximately 10 cm depth of the flooded soils was automatically recorded. Aboveground biomass of rice crop was measured approximately every 10 days in Nanjing and every other week in Texas. Seasonal variation of soil temperature in Nanjing was quite wide with a magnitude of 15.3℃ and that in Texas was narrow with a magnitude of 2.9℃. Analysis of methane emission fluxes against soil temperature and rice biomass production demonstrated that the seasonal course of methane emission in Nanjing was mostly attributed to soil temperature changes, while that in Texas was mainly related to rice biomass production. We concluded that under the permanent flooding condition, the seasonal trend of methane emission would be determined by the soil temperature where there was a wide variation of soil temperature, and the seasonal trend would be mainly determined by rice biomass production if there are no additional organic matter inputs and the variation of soil temperature over the rice growing season is small. 相似文献
88.
A global two-dimensional chemistry model is developed to study long-term trends of CH_4 sinceindustrial revolution.The sources of CH_4,CO and NO_x are parameterized as functions of latitudeand time.With two long-term emission scenarios,long-term trends of CH_4 are simulated.The resultshave a good agreement with observation from ice cores.The modeled CH_4 increased from 760 ppbvin 1840 to 1611.9 ppbv in 1991, while the modeled number concentration of tropospheric OHdecreased from 7.17×10~5 cm~(-3)in 1840 to 5.79×10~5 cm~(-3) in 1991.The increase of atmosphericCH_4 can be explained by the increase of emission of CH_4 and build-up because of decrease of OHradicals that remove CH_4 from the atmosphere.The model is also used to simulate the distribution of CH_4.Comparisons between the modelresults and observations show that the model can simulate both latitudinal distribution and seasonalvariation of CH_4 well. 相似文献
89.
A global two-dimensional chemistry model is developed to study long-term trends of CH4 since industrial revolution.The sources of CH4,CO and NOx are parameterized as functions of latitude and time.With two long-term emission scenarios,long-term trends of CH4 are simulated.The results have a good agreement with observation from ice cores.The modeled CH4 increased from 760 ppbv in 1840 to 1611.9 ppbv in 1991, while the modeled number concentration of tropospheric OH decreased from 7.17×105 cm-3 in 1840 to 5.79×105 cm-3 in 1991.The increase of atmospheric CH4 can be explained by the increase of emission of CH4 and build-up because of decrease of OH radicals that remove CH4 from the atmosphere.The model is also used to simulate the distribution of CH4.Comparisons between the model results and observations show that the model can simulate both latitudinal distribution and seasonal variation of CH4 well. 相似文献
90.
通过对岩石样品进行变形及破坏试验,研究断裂形成过程中的声发射记录(AE),以找到能解释地震前兆现象的方法.另外,对试验过程中获得的大量数据及资料进行了数理统计处理. 相似文献