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81.
82.
T. Feseker T. Pape K. Wallmann S.A. Klapp F. Schmidt-Schierhorn G. Bohrmann 《Marine and Petroleum Geology》2009
The sediment temperature distribution at mud volcanoes provides insights into their activity and into the occurrence of gas hydrates. If ambient pressure and temperature conditions are close to the limits of the gas hydrate stability field, the sediment temperature distribution not only limits the occurrence of gas hydrates, but is itself influenced by heat production and consumption related to the formation and dissociation of gas hydrates. Located in the Sorokin Trough in the northern Black Sea, the Dvurechenskii mud volcano (DMV) was in the focus of detailed investigations during the M72/2 and M73/3a cruises of the German R/V Meteor and the ROV Quest 4000 m in February and March 2007. A large number of in-situ sediment temperature measurements were conducted from the ROV and with a sensor-equipped gravity corer. Gas hydrates were sampled in pressurized cores using a dynamic autoclave piston corer (DAPC). The thermal structure of the DMV suggests a regime of fluid flow at rates decreasing from the summit towards the edges of the mud volcano, accompanied by intermittent mud expulsion at the summit. Modeled gas hydrate dissociation temperatures reveal that the gas hydrates at the DMV are very close to the stability limits. Changes in heat flow due to variable seepage rates probably do not result in changes in sediment temperature but are compensated by gas hydrate dissociation and formation. 相似文献
83.
分别在室内培养箱、海滨室外跑道池和不同自然海区,通过一次性和半连续添加营养、以及检测海区水质和藻体生长的方法,研究了不同氮浓度、温度和氮磷比条件下,长心卡帕藻氮吸收速率的变化和氮吸收速率随时间变化,以及栽培该藻的环境生态贡献。小型实验、中试放大和海区规模栽培结果表明:(1)在10—50μmol/L范围内,该藻吸收氮速率随氮浓度增加而增大;(2)当氮浓度一定时,氮磷比在1—50范围内对该藻吸收氮速率没有产生显著影响(P>0.05);(3)温度对该藻吸收氮速率有显著影响(P<0.05),其中温度在28℃时氮的吸收速率最高;(4)尽管一次性添加营养实验中长心卡帕藻吸收氮速率随时间变化表现出先快后慢的趋势,但是进一步的半连续添加营养实验证实,导致吸收速率下降系底物氮浓度限制,而不是藻本身吸收能力下降,结果还显示卡帕藻具有连续吸收同化无机氮能力;在自然光温度变化和不受底物浓度限制条件下,该藻藻体去除无机氮效率最大维持在0.3μmol/(gFW·h);(5)海南陵水黎安海湾水质数据显示,栽培该藻去除海水富营养化和净化水质作用显著,其去除海水富营养化的年贡献为33t氮素。 相似文献
84.
John G. Pope Jannike Falk-Pedersen Simon Jennings Jake C. Rice Henrik Gislason Niels Daan 《Deep Sea Research Part II: Topical Studies in Oceanography》2009,56(21-22):2097
Historically colder regions of the North Atlantic had fisheries dominated by only a few fish species; principally cod and capelin. Possible population dynamic mechanisms that lead to such dominance are investigated by considering how a charmingly simple published multispecies model of the North Sea would react if the system operated at a lower temperature. The existing model equations were modified to describe temperature effects on growth, fecundity and recruitment and the model was rerun based on typical temperatures for the North Sea and a colder system. The results suggest that total fish biomass in the colder system increases but the community is more vulnerable to a given rate of fishing mortality. In the colder system, within species density dependence is reduced but relative predation rates are higher. Consequently, intermediate-sized species are vulnerable to relatively high levels of predation throughout their life history and tend to be excluded, leading to a system dominated by small and large species. The model helps to explain how temperature may govern coexistence and competitive exclusion in fish communities and accounts for the observed dominance of small and large species in Boreal/Arctic ecosystems. 相似文献
85.
采用温度和盐度单一和组合因子设计实验方法,系统地研究了温度、盐度对栉孔扇贝胚胎和幼虫的影响。结果表明,栉孔扇贝胚胎发育适宜温度为16.0—22.0℃,盐度为27.5—32.5;最佳温度为18.0~22.0℃,盐度为30.0—32.5;幼虫培育适宜温度为16.0—26.0℃,盐度为27.0—39.0;最佳温度为19.0—22.0℃,盐度为27.0—32.0。相对而言,栉孔扇贝胚胎和幼虫对低温高盐适应能力较强,温度显著影响胚胎孵化和幼虫发育,盐度显著影响幼虫生长;二者组合影响对胚胎孵化不显著:随着幼虫的发育。组合影响对幼虫存活十分显著;对幼虫生长不显著。 相似文献
86.
基于辐射传输模型MonoRTM计算天空亮温度,使用多元线性统计回归方法和BP神经网络方法分别对大气温度和水汽密度廓线进行了反演,检验并分析了两种方法的反演精度.结果表明,多元线性回归方法反演的温度偏差总体不大于6K,反演的水汽密度偏差小于4 g/m3;神经网络方法反演的温度偏差小于2K,反演的水汽密度误差总体不大于2 g/m3.与探空数据的对比表明,对于大气温度和水汽密度反演,BP神经网络方法的反演结果都要比多元线性回归方法的反演结果更接近探空资料值. 相似文献
87.
88.
A 2000-yr reconstruction of air temperature in the Great Basin of the United States with specific reference to the Medieval Climatic Anomaly 总被引:1,自引:0,他引:1
Scott A. Reinemann David F. Porinchu Glen M. MacDonald Bryan G. Mark James Q. DeGrand 《Quaternary Research》2014
A sediment core representing the past two millennia was recovered from Stella Lake in the Snake Range of the central Great Basin in Nevada. The core was analyzed for sub-fossil chironomids and sediment organic content. A quantitative reconstruction of mean July air temperature (MJAT) was developed using a regional training set and a chironomid-based WA-PLS inference model (r2jack = 0.55, RMSEP = 0.9°C). The chironomid-based MJAT reconstruction suggests that the interval between AD 900 and AD 1300, corresponding to the Medieval Climate Anomaly (MCA), was characterized by MJAT elevated 1.0°C above the subsequent Little Ice Age (LIA), but likely not as warm as recent conditions. Comparison of the Stella Lake temperature reconstruction to previously published paleoclimate records from this region indicates that the temperature fluctuations inferred to have occurred at Stella Lake between AD 900 and AD 1300 correspond to regional records documenting hydroclimate variability during the MCA interval. The Stella Lake record provides evidence that elevated summer temperature contributed to the increased aridity that characterized the western United States during the MCA. 相似文献
89.
The paper describes prediction of thermal conductivity in terrestrial soil media. The model operates statistically by probability of occurrence for contacts between particular fractional compounds. It combines physical properties, specific to particular compounds, into one apparent conductance specific to the mixture. The concept of substituting grain compounds by hypothetical spheres is an essential tool to control porosity by the number of spheres, their radii and probability of contacts between them. The spheres are equal in radii. The spheres substitute compounds, regardless of the phase state. Control of particular phase states is possible by means of specific properties assigned to the spheres, at the input to the model. Performance of the model is successfully proved for many diverse terrestrial soil media in a wide range of bulk density, composition, water and water vapour content. Only the compounds of sand decline from the expected values and require introducing a correction to the thermal conductivity of sand grains. One possible explanation is that the thermal conductivity of sand is uncertain. Nevertheless, the model is useful and worth extending beyond terrestrial purposes. 相似文献
90.
The HCN emission features near 3 μm recently detected by Geballe et al. (2003, Astrophys. J. 583, L39) are analyzed with a model for fluorescence of sunlight in the ν3 band of HCN. The emission spectrum is consistent with current knowledge of the atmospheric temperature profile and the HCN distribution inferred from millimeter-wave observations. The spectrum is insensitive to the abundance of HCN in the thermosphere and the thousand-fold enhancement relative to photochemical models suggested by Geballe et al. (2003, Astrophys. J. 583, L39) is not required to explain the observations. We find that the spectrum can be matched with temperatures from 130 to 200 K, with slightly better fits at high temperature, contrary to the temperature determination of 130±10 K of Geballe et al. (2003, Astrophys. J. 583, L39). The HCN emission spectrum is sensitive to the collisional de-excitation probability, P10, for the ν3 state and we determine a value of 10−5 with an accuracy of about a factor of two. Analysis of absorption lines in the C2H2ν3 band near 3 μm, detected in the same spectrum, indicate a C2H2 mole fraction near 0.01 μbar of 10−5 for P10=10−4. The derived mole fraction, however, is dependent upon the value adopted for P10 and lower values are required if P10 at Titan temperatures is less than its room temperature value. 相似文献