植物碳同位素组成的环境影响因素及在水分利用效率中的应用

碳同位素值（δ13C）综合反映了植物光合作用过程中气孔的传导和CO2的固定,可以作为植物在环境中生理机能变化的指标,应用于研究植物生理与生态环境之间的关系。本文主要讨论植物碳同位素组成在不同环境中的变化,并对影响程度和机理进行了探讨。降水、温度、光照、土壤盐度、大气CO2浓度等不同程度影响植物的气孔传导和CO2的固定,植物的δ13C值相应产生不同的变化。降水因素对δ13C值影响最明显,温度对δ13C值产生的影响较复杂。一般情况下,大气中CO2都是通过影响植物叶片的内外压力,造成植物碳同位素值的差异。由于δ13C值不仅可以反映植物在光合作用过程中水分的利用,而且,δ13C值与水分利用效率具有正相关性,因此,碳同位素技术应用于植物生态研究中。     

天山北坡土壤有机碳δ~(13)C组成随海拔梯度的变化

本文选择天山北坡三工河流域作为研究区,基于碳稳定同位素技术,分析土壤有机碳(SOC)δ~(13)C值随降雨量的变化,研究不同海拔梯度土壤剖面δ~(13)C值随采样深度的变化。结果显示,三工河流域降雨量在300mm以下的采样点,SOCδ~(13)C值随降雨量的增加呈递减趋势(R2=0.97),而降雨量在300mm~500mm的采样点,δ~(13)C值随降雨量变化不明显(R2=0.04);三工河流域纯C3植物采样点土壤剖面δ~(13)C值随采样深度呈现明显的富集效应,即土壤剖面下层δ~(13)C值大于上层,其平均差值为1.01‰,与其他相关区域研究结果一致;而沙质荒漠和土质荒漠采样点剖面下层与上层SOCδ~(13)C平均差值为4.33‰,其变化趋势与纯C3植物采样点相反,且其表层δ~(13)C值接近C4植物来源,底层接近C3植物来源,推断其地上历史植被可能经历了由C3到C4的演替过程。     

The Hydrothermal System Beneath Owakudani on Hakone Volcano,Japan; Traced by Stable Isotopic Ratios of H2O

In this study, we sampled natural fumarolic gases, the gas from a steam well drilled to 800 m depth and natural hot spring waters from the Owakudani geothermal area, Hakone Volcano, Japan. We then measured the chemical composition and the D/H and ¹⁸O/¹⁶O ratios of H₂O within the samples. On the basis of the analytical results, we investigated the differentiation processes of the magmatic fluid during ascent to the surface. Volcanic gas discharged from the No. 52 steam well has a CO₂/H₂O ratio that is much higher than those from fumarolic gases. The isotopic ratio of H₂O in the gas are also much higher than those in the fumarolic gases, and the gas also contains high concentrations of SO₂ and HCl. The above observations indicate a magmatic origin for the gas from the No. 52 steam well. The hydrothermal system is principally explained by the mixing of a magmatic vapor, represented by the gas from the No. 52 steam well, and cold local meteoric water. Following mixing of the fluids, a separation of primary vapor and liquid occurs. The primary liquid is discharged as a component of hot spring water, and has high isotopic ratios. The primary vapor is mixed with vapor derived from the boiling of local meteoric water. The mixed vapor is then discharged to the surface, interacting with shallow meteoric water and undergoing partial condensation of H2O vapor. Hot spring water with isotopic ratios lower than those of the primary liquid is derived from the boiling of local meteoric water.     

Applications of spectral computer simulation to surface analysis of materials

This work involves surface analysis by nuclear techniques, which are non-destructive, and computer simulation. The energy analysis method for the nuclear reaction analysis is implemented. Energy spectra are computer simulated and compared to experimental data, giving target composition and concentration profile information. The simulations use, mainly, the target parameterization and the available nuclear data. The method is successfully applied to the determination of uniform concentration profiles of ¹²C, along considerable depths, for a thick target, and for a very thin film. Uniform concentration profiles of ¹⁶O are obtained from (d,p) and (d,α) reactions along large depths. A uniform step concentration profile of ¹⁸O in a thick oxide target is also obtained. Elastic scattering is used in the context of a thin Ag film. SEM proves to be a useful technique for checking surface topography.     

Depth resolution enhancement by combined DSIMS and TOF-LEIS profiling

A combination of dynamic secondary ion mass spectroscopy (DSIMS) and time-of-flight low-energy ion scattering (TOF-LEIS) has been applied to acquire a composition depth profile of MoSi multilayers. During the sequential Ar⁺ sputtering secondary ions were monitored while in-between the sputtering cycles the TOF-LEIS spectra of scattered He neutrals were acquired. All the measured TOF-LEIS spectra versus sputtering time were displayed in one bitmap from which the depth profiles for different scattering depths were derived and analyzed. Analyzing the TOF-LEIS spectra of He particles scattered from the areas below the layer altered by ion-beam mixing led to an improvement of the depth resolution. In this way the resolution limits due to mixing phenomena can be overcome. Finally, the direct comparison of the DSIMS and TOF-LEIS depth profiles was carried out.     

湖泊沉积物中污染有机质及碳酸盐的δ13C影响因素分析

摘要：本文以松嫩平原湖泊表层沉积为研究对象。通过对沉积物有机质正构烷烃组分的分析,了解湖泊中有机质的来源和沉积环境。结合湖泊水介质和沉积物特征,综合分析了沉积物有机质和碳酸盐碳同位素组成的影响因素。结果显示出湖泊沉积物中不同有机质类型对碳同位素组成有较大的作用,生物有机质的大量输入使碳酸盐的碳同位素组成明显偏轻,而石油类污染的输入对应于碳酸盐中的碳同位素组成稍偏重。     

三七各部位氢氧同位素特征及其与灌溉水关系

分析不同产地三七各部位(茎叶、芦头、块根、筋条、须根)及灌溉水中稳定氢氧同位素特征、相关性及影响因素,为其能否作为产地溯源指标提供技术支撑.在三七产区——广西靖西片区、云南文山片区、云南新拓展片区采集43个春三七样点植株和相应的灌溉水并测定其稳定氢氧同位素比率,现场测定经纬度、海拔,进行差异分析和相关性分析.结果表明,...     

利用石生苔藓中硫同位素示踪大气硫源的变化规律

为探讨石生苔藓硫同位素组成特征对区域性大气硫源的指示作用,连续两年采集鄱阳湖生态经济区内的石生苔藓样品,测定δ³⁴S值;并结合已有的雨水、煤的硫同位素值等相关研究数据进行对比分析。样品δ³⁴S值均偏正,平均为+4.9‰,取值范围为+1.9‰~+9.6‰;石生苔藓δ³⁴S值与空气中SO₂浓度呈负相关关系;南昌、抚州两市苔藓δ³⁴S值的取值范围与其对应城市大气降水δ³⁴S值的变化区间相接近;研究区内土壤相对富集重硫,且土壤中可溶性硫主要受大气硫沉降影响。结果表明,石生苔藓的硫同位素组成对区域性大气硫源具有指示意义,鄱阳湖生态经济区大气硫沉降的硫源主要来自人为成因硫和生物成因硫,可能还有远距离传输硫等其他硫源的影响。     

Reef coral δ15O thermometer in Hainan island waters,South China Sea

An 18-year-long (1981-1998) study was conducted in Hainan Island wa ters (22°20＇N, 110°39′E) to determine the relationship between δ18O in skeletal arag onite carbonate and sea surface temperature (SST) in porites lutea of reef-building corals. δ18O values in skeletal aragonite carbonate were measured by means of mass spectrometry. Coral samples grew at 5m depth at Longwan Bay. Monthly measure ments of the SST from 1960 to 1998 were taken at Qinglan Bay adjacent to the place of the collected samples. The thermometer shows that SST=-4.16 δ18OpDB + 4.9 (r=0.80) and dδ18O/dT=-0.24 permil/°C. The δ18O thermometer is strongly influ enced by the rainfall and runoff. Using the thermometer, the SST in the past hundred years with monthly resolution will be reconstructed and the climatic change in the northern area of South China Sea will be hindcasted     

野外试验场黄土包气带水分入渗试验研究

黄土介质特有的垂直节理和大孔隙发育性质 ,使黄土包气带水分入渗过程具有与其它均匀土壤的非饱和水分运动不同的特征。通过试验场黄土包气带水分入渗试验和土壤水动力学理论分析 ,说明非饱和条件下黄土介质中的垂直节理对水分入渗几乎不起作用 ,而大孔隙对水分入渗起着显著的阻滞作用。     

Ion-beam induced compositional changes in alloys at elevated temperatures

Near-surface compositional changes in alloys during ion bombardment have been studied theoretically. The scheme employed ensures pressure relaxation of the target, and the effects of preferential sputtering, collisional mixing, radiation-enhanced diffusion, and Gibbsian and radiation-induced segregation are allowed for. High-fluence composition profiles were determined directly from a nonlinear integro-differential equation by means of an efficient iteration procedure developed recently. The dependence of the composition profile on input parameters such as target temperature and defect mobility was examined for Ni---Cu and Ni---Pd alloys.     

Surface structure of an ionic liquid with high-resolution Rutherford backscattering spectroscopy

The surface of an ionic liquid, trimethylpropylammonium bis(trifluoromethanesulfonyl)imide ([TMPA] [TFSI]), is observed by high-resolution Rutherford backscattering spectroscopy (HRBS). The composition depth profiles are derived from the observed HRBS spectra through spectrum simulation. The observed composition is in good agreement with the stoichiometric composition at depths larger than ∼1 nm. The observed composition profiles, however, show pronounced structures at the surface. Fluorine profile has a sharp peak at ∼0.1 nm and a broad peak at ∼1.0 nm. The sulfur profile also has a peak at ∼0.35 nm. These results indicate that the molecules show preferred orientations at the surface. From the observed profiles, it was concluded that the C₁ conformer of the [TFSI] anion is dominant over the C₂ conformer at the surface in contrast to bulk, where the C₂ conformer is known to be dominant. It was also found that C₁ conformers are oriented with their CF₃ groups pointing toward the vacuum in the outermost molecular layer.     

Isotopic Effect in Ion-Induced Re-Emission of Hydrogen Implanted into Graphite

The re-emission of H and D atoms, implanted into graphite, induced by 1.5 MeV He⁺bombardment has been studied by means of the elastic recoil detection (ERD) technique by changing the initial peak concentration of H and D, the temperature and the He⁺ ion flux. The experimental re-emission profiles were analyzed solving analytically the mass balance equations. The whole re-emission profiles are shown to be excellently reproduced in terms of the ion- induced detrapping (σd), trapping (or retrapping) (Σ_T ) and local molecular recombination (k) between an activated (free) hydrogen atom and a trapped one and that the effective detrapping cross sections Σ_dK/Σ_T for H and D are determined as the best fitting parameter to be 2.9xl0-¹⁸ and 7.7x 10-¹⁹ cm², respectively. It is also shown from the experimental data on little dependence of the re-emission profile on the He⁺ ion flux that the local molecular recombination plays a major role in the ion-induced re-emission. Furthermore, the difference between the effective detrapping cross sections for H and D is reasonably explained in terms of isotopic difference in the values of K for H and D.     

CFD simulation of steam jet-induced thermal mixing in subcooled water pool

This study examined the IRWST thermal mixing phenomena induced by a steam jet in a subcooled water pool. Due to the limitation of the current CFD code to simulate condensation, the steam condensation region model was developed to evaluate the thermal mixing phenomena. Within this region, all the steam was condensed into water, and the steam mass and energy inputs were treated as the source. This calculation was treated using single-phase CFD methods. The benchmark calculation for a thermal mixing experiment in the water tank was performed to develop an optimized 3D evaluation methodology of the thermal-hydraulic behavior in APR1400 IRWST. Steam discharge through the sparger and condensation phenomenon was modeled with the choking flow and thermal mixing model in the quenching tank using CFX11.Three types of thermal mixing experiments, local phenomena test, thermal mixing tests in cylindrical water pool and annulus water pool, were designed to provide data representative of the behavior of the prototype for CFD simulations of the thermal-hydraulic behavior in IRWST. A comparison of the calculated and experimentally measured temperature profiles showed some disagreement particularly around the sparger. The main reason for this disagreement was caused by the difference in the test and simulating conditions at the tank wall. However, moving away from the sparger, the trends of the temperature rise became similar to that in the experiment. Despite these problems, this model is the best way of evaluating the thermal mixing phenomena caused by a steam jet in a subcooled water pool.     

中子土壤水分探测仪在农田建设和土壤改良中的应用

当快中子与土壤中的氢发生弹性碰撞时,快中子慢化成热速度,中子仪是根据中子的特性制造的,以便测定土壤的水分含量。在农田建设和土壤改良中经常需了解土壤的含水量和它随深度和时间的变化。 根据上述数据,人们可以计算土壤剖面的水量平衡和储量以及水分的亏损。因此决定灌溉淋洗盐碱土的需水量和作物的需水量。 中子仪可以提供一种快速非破坏的监测土壤含水量的方法和土壤水分随空间和时间上的变化。     

重水中氢氧同位素的质谱分析

用高分辨率质谱计分析了重水中氢与氧的同位素组成；分析了重水的分子组成、质谱中的单电荷离子；利用高分辨率质谱峰相对强度，计算了重水中的氢氧同位素组成。结果表明，高分辨率质谱法分析重水，可同时分析其中的氢同位素和氧同位素，并且用样量小，结果可靠。     

基于稳定同位素比率差异的西湖龙井茶产地溯源分析

通过测定不同产区扁形茶稳定同位素比率,借助化学计量学工具探索建立西湖龙井茶产地区分模型。从山东、四川、浙江、贵州等扁形茶主产区代表性取样,采用稳定同位素质谱测定样品中碳、氢、氧、氮、锶、铅、镉稳定同位素比率,对其进行方差分析,采用逐步线性判别（FLDA）、决策树C5.0和神经网络方法构建模型进行产地区分。结果表明,不同产地扁形茶中稳定同位素比率表现出产地差异。δD、δ¹⁸O受陆地效应和高程效应影响较大,并且二者有较好的正相关关系,⁸⁸Sr/⁸⁶Sr比值随地区纬度增加而增大,在不同产地扁形茶间差异尤为显著。FLDA和BP-ANN模型对外部样本的预测能力相对较差,分别为76%和84%;决策树算法模型回代验证准确率为91.35%,对外部样本的预测准确度达到92%。结果表明,在西湖龙井茶产地判别中,采用基于稳定同位素比率的决策树算法模型可取得较好的效果。     

不同棒束结构稠密栅元通道内的湍流CFD研究

采用URANS（UnsteadyReynoldsAveragedNavierStokes）方法对不同棒束结构稠密栅元通道（P/D=1.001～1.2）内的湍流流动进行CFD模拟。研究分析了不同Re（Re=5000~215000）的湍流流动的主流速度、壁面剪应力、湍动能等参数。研究表明：在较稠密的棒束（P/D<1.1）通道内,P/D的变化对子通道内主流速度和剪应力分布均有较大影响。本文的模拟结果也验证了在达到临界P/D前（即使δ/D<0.011）,交混因子Y和δ/D成反比关系。对于固定的棒束结构（P/D=1.062）,当Re达到一定值（Re=9600）时,子通道内主流速度和剪应力分布对Re的变化不敏感。     

Isotope Effect and Isotope Separation: A Chemist's View

The behavior of uranyl fluoride complexes containing different isotopic species [¹⁶O-U-¹⁶O]²⁺, [¹⁶O-U-¹⁸O]²⁺, [¹⁸O-U-¹⁸O]²⁺ in isopropanol solutions under UV irradiation was studied. The rate of decrease in concentration of uranyl complexes containing isotopic species [¹⁶O-U-¹⁸O]²⁺ is higher than that for uranyl containing [¹⁸O-U- ¹⁸O]²⁺ species. It was shown that this phenomenon is not caused by difference in extinction energy of vaious isotopic species.     

Pollution assessment in the Trancão river basin (Portugal) by PIXE, EDXRF and isotopic analysis

This paper reports on the inorganic contamination assessment of a river basin and local water resources in order to establish quality standards. PIXE was applied to the elemental determination of the freeze-dried water dry residue and EDXRF was used for the evaluation of elemental content of sediments. To infer the water provenance the electrical conductivity was measured as well as the isotopic composition of surface waters using the ¹⁸O/¹⁶O ratio. The combined isotopic and elemental composition information enables to establish dominant contamination contributions from the several tributaries. Moreover, the variability observed for certain parameters, associates them with specific basin regions as for instance, dry residue mass, conductivity and Br, or S, Cl and As or Cr, Ni, Zn and Pb which permit to establish both pollution characterisation and their origin (agriculture, industrial, etc.). At certain locations, enhanced concentrations of elements as Cr, Cu, Zn and Pb are observed both in sediments and in the surface water. The elemental particular associations also permit to characterise pollution sources.