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31.
Xuefeng Xia Douglas Ian Stewart Lirong Cheng Kai Wang Jing Li Dan Zhang Aizhong Ding 《水文研究》2020,34(25):4973-4984
Column experiments containing an aquifer sand were subjected to static and oscillating water tables to investigate the impact of natural fluctuations and rainfall infiltration on the groundwater bacterial community just below the phreatic surface, and its association with the geochemistry. Once the columns were established, the continuously saturated zone was anoxic in all three columns. The rate of soil organic matter (SOM) mineralization was higher when the water table varied cyclically than when it was static due to the greater availability of NO3− and SO42−. Natural fluctuations in the water table resulted in a similar NO3− concentration to that observed with a static water table but the cyclic wetting of the intermittently saturated zone resulted in a higher SO42− concentration. Rainfall infiltration induced cyclic water-table variations resulted in a higher NO3− concentration than those in the other two columns, and a SO42− concentration intermediate between those columns. As rainwater infiltration resulted in slow downward displacement of the groundwater, it is inferred that NO3− and SO42− were being mobilized from the vadose zone. NO3− was mainly released by SOM mineralization (which was enhanced by the infiltration of oxygenated rainwater), but the larger amount of SO42− release required a second mechanism (possibly desorption). Different groundwater bacterial communities evolved from initially similar populations due to the different groundwater histories. 相似文献
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利用1999~2016年秦巴山区范围内的81个气象站实测逐日降水资料,对TRMM 3B42卫星降水数据在秦巴山区的适用性进行了评估。结果表明:TRMM 3B42数据在月、季、年尺度上具有较高的精度,3~11月精度较高,1月略低,四季中冬季精度较低。TRMM所反映的降水变化过程与实测降水过程基本一致,但在降水量上存在一定差异,TRMM有略微高估降水的特征。按不同雨量等级对比,发现卫星资料对中雨及以上级别的降水具有较高的精度,无雨及小雨精度略低,原因是TRMM对0.1~0.9mm微量降水的探测能力较弱。无雨、小雨、暴雨日TRMM估计与站点实测具有相反的年际变化趋势,中雨、大雨日具有相同的年际变化趋势。研究结果对秦巴山区资料缺乏地区的气象过程研究具有重要的应用价值。 相似文献
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G. M. Hill A. F. J. Moffat † N. St-Louis P. Bartzakos 《Monthly notices of the Royal Astronomical Society》2000,318(2):402-410
We have obtained complete phase coverage of the WC7+O binaries WR 42 = HD 97152 and WR 79 = HD 152270 with high signal-to-noise ratio (S/N), moderate-resolution spectra. Remarkable orbital phase-locked profile variations of the C iii λ 5696 line are observed and interpreted as arising from colliding wind effects. Within this scenario, we have modelled the spectra using a purely geometrical model that assumes a cone-shaped wind–wind interaction region which partially wraps around the O star. Such modelling holds the exciting promise of revealing a number of interesting parameters for WR+O binaries, such as the orbital inclination, the streaming velocity of material in the interaction region and the ratio of wind momentum flux. Knowledge of these parameters in turn leads to the possibility of a better understanding of WR star masses, mass-loss rates and wind region characteristics. 相似文献
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全球植被分布对气候影响的数值试验 总被引:4,自引:3,他引:4
利用一个新的陆-气双向耦合模式R42_AVIM, 通过有无植被覆盖的对比试验分析, 探讨了全球植被分布对气候和大气环流产生的潜在影响。得出: 陆面植被覆盖使得地表特征参数发生行星尺度的明显改变, 在叶面积指数大的热带和中高纬度森林带尤其显著。在现实植被分布下, 陆地表面反照率减小, 地表净辐射收支和地表潜热通量增加, 而地表感热通量减小。植被叶面积指数比较大的区域地表温度降低, 并且这种温度的改变一直延伸到对流层中上层, 在热带表现为斜压结构, 而在中高纬表现为相当正压结构。植被的存在使热带和中高纬度森林带的蒸发和相应的高层凝结潜热加热增强, 从而增强了经圈环流的上升支, 使得冬季在热带和南半球中纬度降水增多, 夏季在热带和北半球中高纬地区降水明显增多; 而经圈环流下沉支的增强致使副热带降水减少且更干旱。同时, 植被的存在使大陆潜热释放增强, 气温下降, 减小了海陆温度对比, 亚洲夏季风也有所减弱。 相似文献
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Cloud is one of the uncertainty factors influencing the performance of a general circulation model (GCM).Recently,the State Key Laboratory of Atmospheric Sciences and Geophysical Fluid Dynamics,Institute of Atmospheric Physics(LASG/IAP)has developed a new version of a GCM(R42L9).In this 相似文献
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Calcium Isotopic Fractionation and Compositions of Geochemical Reference Materials 总被引:1,自引:0,他引:1
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Fang Liu Hong L. Zhu Xin Li Gui Q. Wang Zhao F. Zhang 《Geostandards and Geoanalytical Research》2017,41(4):675-688
High‐precision calcium isotopic compositions of a set of geological reference materials from the IAG (OU‐6), ANRT (UB‐N), MPI‐DING, USGS and GSJ, relative to NIST SRM 915a, are reported here. Measurements were performed by thermal ionisation mass spectrometry (Triton instrument) using a 42Ca–43Ca double spike. δ44/40Ca values of selected reference materials, mainly felsic rocks, are reported for the first time. Felsic rock values of δ44/40Ca ranged from 0.13‰ to 1.17‰, probably implying Ca isotopic fractionation could occur during magma evolution. δ44/40Ca values of ultramafic rocks, ranging from 0.74‰ to 1.51‰, were positively correlated with MgO and negatively with CaO contents, possibly owing to Ca isotopic fractionation during partial melting. δ44/40Ca of intermediate‐mafic rocks were around 0.78‰ and displayed limited variation, suggesting Ca isotopic fractionation is insignificant during magma evolution processes. As expected, δ44/40Ca of sedimentary and metamorphic rocks varied widely due to complex geological processes. 相似文献
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