温差对泉州四至井水氡测值的影响分析

温度变化是影响水氡观测值的主要因素之一.通过1986-2009年泉州台四至井观测数据资料的分析,说明:调整观测室室内温度使其超过采集水样的原始温度,在运输水样过程中对水样采取保温措施,减小取样水温和鼓泡后水温的温差,能够得到更真实、准确的观测值.     

Diffusive equilibrium in thin films provides evidence of suppression of hyporheic exchange and large‐scale nitrate transformation in a groundwater‐fed river

The hyporheic zone of riverbed sediments has the potential to attenuate nitrate from upwelling, polluted groundwater. However, the coarse‐scale (5–10 cm) measurement of nitrogen biogeochemistry in the hyporheic zone can often mask fine‐scale (<1 cm) biogeochemical patterns, especially in near‐surface sediments, leading to incomplete or inaccurate representation of the capacity of the hyporheic zone to transform upwelling NO₃^?. In this study, we utilised diffusive equilibrium in thin‐films samplers to capture high resolution (cm‐scale) vertical concentration profiles of NO₃^?, SO₄^2?, Fe and Mn in the upper 15 cm of armoured and permeable riverbed sediments. The goal was to test whether nitrate attenuation was occurring in a sub‐reach characterised by strong vertical (upwelling) water fluxes. The vertical concentration profiles obtained from diffusive equilibrium in thin‐films samplers indicate considerable cm‐scale variability in NO₃^? (4.4 ± 2.9 mg N/L), SO₄^2? (9.9 ± 3.1 mg/l) and dissolved Fe (1.6 ± 2.1 mg/l) and Mn (0.2 ± 0.2 mg/l). However, the overall trend suggests the absence of substantial net chemical transformations and surface‐subsurface water mixing in the shallow sediments of our sub‐reach under baseflow conditions. The significance of this is that upwelling NO₃^?‐rich groundwater does not appear to be attenuated in the riverbed sediments at <15 cm depth as might occur where hyporheic exchange flows deliver organic matter to the sediments for metabolic processes. It would appear that the chemical patterns observed in the shallow sediments of our sub‐reach are not controlled exclusively by redox processes and/or hyporheic exchange flows. Deeper‐seated groundwater fluxes and hydro‐stratigraphy may be additional important drivers of chemical patterns in the shallow sediments of our study sub‐reach. © 2015 The Authors. Hydrological Processes Published by John Wiley & Sons Ltd.     

最不利设计地震动研究

实际记录到的真实地震动在工程结构的抗震研究、分析和设计中往往作为一种施加到结构上使结构振动，直至破坏的地震荷载．如何合理选择真实的地震动记录作为研究结构地震反应的输入，一直是国内外抗震研究和设计中引人关注的重要问题．本文首先提出了最不利设计地震动的概念；然后在收集到的国内外5000余条被认为有重要意义的地震动记录基础上，利用综合估计地震动潜在破坏势的方法，对４种场地类型分别给出了长周期、短周期和中周期结构的国内外最不利设计地震动；最后通过几类不同结构的地震反应分析，初步验证了本文所确定的最不利设计地震动的可靠性和合理性．      

北极海冰变化特征分析

本文利用NASA的海冰密集度资料(时间为1978年10月～2002年9月,分辨率为1.0×0.25),计算并分析了1978～2002年的北极海冰面积、范围的时间变化趋势以及变化的空间分布。     

Comparative assessment of the relationship of satellite data with the above ground biomass of Sal trees (<Emphasis Type="Italic">Shorea robusta</Emphasis>) determined from phenologically different time periods

The Above Ground Biomass(AGB) estimates of vegetation comprise both the bole biomass determined through a volumetric equation and litter biomass collected from the ground.For mature trees,the AGB estimated in phenologically different time periods is directly affected by the litter biomass since the Diameter at Breast Height(DBH) and height(H) of such trees that are used in the estimation of bole biomass would remain unchanged over a reasonable time period.In the present study,we have determined the AGB of Sal trees(Shorea robusta) in two contrasting seasons:the peak green period in October being devoid of lit-ter on the ground and the leaf shedding period in February with abundant amount of litter present on the ground.Estimation of AGB for the month of February included the litter biomass.In contrast,the AGB for October represented only the bole biomass.AGB was estimated for ten different plots selected in the study area.The AGB estimated from ten sampling plots for each time period was re-gressed with the individual tree parameters such as the average DBH and height of trees measured from the corresponding plots.The regression analysis exhibited a significantly stronger relationship between the AGB and DBH for the month of October as compared to February.Furthermore,the correlation between the remotely sensed derived data and AGB was also found to be significantly higher for the month of October than February.This observation indicates that inclusion of the litter biomass in AGB will tend to decrease the re-gression relationship between AGB and DBH and also between the remotely sensed data and AGB.Therefore,these conclusions invite careful consideration while estimating AGB from satellite data in phenologically different time periods.     

岩溶洞穴次生碳酸盐沉积铀及其同位素组成古气候环境研究进展

洞穴沉积铀含量及其同位素初始234U/238U[（234U/238U)0]变化均与过去气候环境变化关系密切。文章分别对石笋中U含量和(234U/238U)0的气候意义进行统计分析发现,多数研究认为洞穴沉积U含量和(234U/238U)0可能指示土壤湿度和有效降水变化。然而,不管是对洞穴沉积的U含量还是(234U/238U)0,其气候环境意义解读还存在两种观点。但无论如何,这些研究成果都显示了洞穴沉积的U含量和(234U/238U)0是研究过去气候环境变化的重要替代指标。在未来的研究中,除了土壤环境和过程,还应关注U来源的相对贡献变化和其他微量元素与U元素的关系。这一指标可能在对东亚地区的大气粉尘活动和冬季风演化、地表生物量的变化研究等方面发挥重要作用。      

Gamma-Hadron Separation using Čerenkov Photon Density Fluctuations

In the atmospheric Čerenkov technique γ-rays are detected against the abundant background produced by hadronic showers. In order to improve the signal to noise ratio of theexperiment, it is necessary to reject a significant fraction of hadronic showers. Traditional background rejection methods based on image shape parameters have been extensively used for the data from imaging telescopes. However, non-imaging Čerenkov telescopes have to develop very different means of statistically identifying and removing cosmic ray events. Some of the parameters, which could be potentially important for non-imaging arrays, are the temporal and spectral differences, the lateral distributions and density fluctuations of Čerenkov photons generated by γ-ray and hadron primaries. Here we study the differences in fluctuations of Čerenkov photon density in the light pool at the observation level from showers initiated by photons and those initiated by protons or heavier nuclei. The database of simulated events for the PACT array has been used to evaluate the efficiency of the new technique. Various types of density fluctuations like the short range and medium range fluctuations as well as flatness parameter are studied. The estimated quality factors reflect the efficiencies with which the hadrons can be rejected from the data. Since some of these parameters are independent, the cuts may be applied in tandem and we demonstrate that the proton rejection efficiency of ∼90% can be achieved. Use of density fluctuations is particularly suited for wavefront sampling observations and it seems to be a good technique to improve the signal to noise ratio. This revised version was published online in July 2006 with corrections to the Cover Date.     

Sensitivity assessment of strontium isotope as indicator of polluted groundwater for hydraulic fracturing flowback fluids produced in the Dameigou Shale of Qaidam Basin

Hydrogeochemical processes that would occur in polluted groundwater and aquifer system, may reduce the sensitivity of Sr isotope being the indicator of hydraulic fracturing flowback fluids(HFFF) in groundwater. In this paper, the Dameigou shale gas field in the northern Qaidam Basin was taken as the study area, where the hydrogeochemical processes affecting Sr isotope was analysed. Then, the model for Sr isotope in HFFF-polluted groundwater was constructed to assess the sensitivity of Sr isotope as HFFF indicator. The results show that the dissolution can release little Sr to polluted groundwater and cannot affect the εSr(the deviation of the 87 Sr/86 Sr ratio) of polluted groundwater. In the meantime, cation exchange can considerably affect Sr composition in the polluted groundwater. The Sr with low εSr is constantly released to groundwater from the solid phase of aquifer media by cation exchange with pollution of Quaternary groundwater by the HFFF and it accounts for 4.6% and 11.0% of Sr in polluted groundwater when the HFFF flux reaches 10% and 30% of the polluted groundwater, respectively. However, the Sr from cation exchange has limited impact on Sr isotope in polluted groundwater. Addition of Sr from cation exchange would only cause a 0.2% and 1.2% decrease in εSr of the polluted groundwater when the HFFF flux reaches 10% and 30% of the polluted groundwater, respectively. These results demonstrate that hydrogeochemical processes have little effect on the sensitivity of Sr isotope being the HFFF indicator in groundwater of the study area. For the scenario of groundwater pollution by HFFF, when the HFFF accounts for 5%(in volume percentage) of the polluted groundwater, the HFFF can result in detectable shifts of εSr(ΔεSr=0.86) in natural groundwater. Therefore, after consideration of hydrogeochemical processes occurred in aquifer with input of the HFFF, Sr isotope is still a sensitive indicator of the Quaternary groundwater pollution by the HFFF produced in the Dameigou shale of Qaidam Basin.     

Trace Metals in Selected Benthic Invertebrates from Belgian Coastal Waters (1981–1996)

Mercury, cadmium, lead, copper, zinc and chromium were assessed in brown shrimp (Crangon crangon), swimming crab (Liocarcinus holsatus), hermit crab (Pagurus bernhardus), starfish (Asterias rubens) and cut trough shell (Spisula subtruncata) from ten sampling stations off the Belgian coast, including three dredge spoils disposal sites. Calculations of time trends indicated that on the whole concentrations of trace metals had significantly decreased since 1981, also on dredged material dumping sites. Starfish and hermit crab were found to be the most promising benthic indicator species for metal contamination. Globally, the location of the sites, including the dredge spoils disposal zones, showed to be of little influence on the concentrations of trace metals.     

公路路面热效应对环境气温的影响分析

为定量研究公路对气温观测的影响,本文使用2014年1—5月在陕西省开展的两组公路观测试验的逐分钟温度、风向、风速等气象资料,对比分析了合阳县国道和渭蒲高速公路在不同季节、不同天空状况以及不同背景风速条件下对周围环境气温观测的影响程度和影响距离。试验结果表明:公路对周围的环境温度有一定的增温影响,合阳国道对环境温度的增温影响至75m,增温效应达0.25~0.4℃。高速公路的增温影响至125m,增温效应达0.2~0.4℃。冬季,两条公路白天增温效应较夜间明显,春季,高速公路夜间增温更明显。晴天、多云天气比阴天、降雨天气增温程度大。公路对气温的增温影响存在风速阈值,当风速小于对应阈值时,增温效应明显。公路上来往车流量对气温有一定的叠加增温影响,合阳国道白天车流量150~350辆,叠加增温效应0.05~0.1℃,蒲渭高速白天车流量2000~3500辆,叠加增温效应0.16℃。