荧光光谱法分析油气化探样品中的芳烃

荧光光谱法避免了色谱法所需的大量分离工作,具有灵敏度高、检测限低、分析速度快等特点,非常适用于油气化探样品分析。本文对常规荧光光谱分析的样品前处理方法和仪器测定参数进行优化,建立了适用于测定油气化探样品中芳烃的荧光光谱分析方法。实验采用农残级正己烷作为溶剂,简化了溶剂提纯操作,采用振荡器间歇振荡方式有效地提高了芳烃的提取效果。在优化的仪器条件下对油气化探样品中的芳烃进行检测,选择萘、菲、艹屈三种标准物质,采用单点外标法对样品激发波长265 nm,发射波长为320 nm、360 nm、405 nm的三个特征光谱峰进行定量分析,测定结果采用量化后的浓度值代替常用的荧光强度值,使不同实验室、不同型号仪器间的荧光指标具有统一的定量标准,提高了数据的可比性。本方法检测限为1.8ng/g(以萘计算),优于行业标准(SY/T 6009.8—2003)规定的检出限≤2 ng/g要求,方法精密度(RSD,n=12)为4.5%(320 nm)、9.6%(360 nm)、14.7%(405 nm)。通过质量控制与质量管理体系的完善,本方法已经在大庆地区油气化探工作中得到实际应用,荧光指标对样品采样深度确定及异常点发现具有良好的指示作用。     

微波消解-电感耦合等离子体质谱法测定生物样品中微量硒的方法研究

生物样品中微量元素硒的分析检测,经典方法是湿法消解-氢化物发生原子荧光光谱法(HGAFS)。湿法消解处理生物样品需使用大量试剂,并且消解时间长,样品背景值高;HG-AFS的分辨率较低,已经不能满足微量硒的分析需求。解决生物样品的消解过程缓慢、试剂用量大的问题是提高样品中微量元素硒的检出限和分辨率的前提。本文采用湿法消解和微波消解两种消解体系处理样品,对两种方法制备的溶液分别采用HG-AFS和电感耦合等离子体质谱法(ICP-MS)进行测定,通过对比试验确定了微波消解ICP-MS方法可以实现生物样品中微量硒的准确测定。对比试验表明:采用高压密闭微波消解前处理样品技术可以大大缩短消解时间,减少试剂用量,降低了样品背景值;利用ICP-MS直接进行测定,方法检出限为0.01μg/g,精密度(RSD,n=12)小于4%,低于HG-AFS的检出限(0.03μg/g)和精密度(10%)。微波消解ICP-MS方法操作简单快捷,降低了方法检出限,提高了样品分析的准确度和精密度。     

40Ar/39Ar年代学中几个重要问题的讨论

40Ar/39Ar年代学是同位素地质年代学中重要的两个"金钉子"手段之一(另一个为U-Pb法),广泛应用于重大地质事件、地质界线的精确定年,是确定地质年表的主要手段。40Ar/39Ar年代学测定的母体元素钾为常量元素,且实现分析时由于只需测定Ar同位素的比值,因而具有很高的分析精度,因此可以测定非常年轻(数千年)地质体的年龄。此外,由于在自然界中不易发生(物理、化学)反应的特性,Ar在矿物中的扩散可被准确地定量描述,因此40Ar/39Ar年代学也是热年代学的重要支柱,被广泛应用于地球深部物质上涌、折返、剥露、变质的冷却历史,率先提供了解析造山带、地壳作用过程等热历史的定量模型。这些特点使得40Ar/39Ar年代学成为地质年代学的三大支柱之一。那么,近年来该方法发展到了什么程度,其精确度和准确度达到了怎样的高度?为何年轻火山样品中极少发现过剩Ar?高压环境中的样品过剩Ar为何难以辨认?压力影响矿物的封闭温度吗?缓慢冷却K-长石的年龄谱是否可以真实地反映岩体所经历的热历史?多重扩散域模型(MDD)遇到了哪些挑战、该如何应用?40Ar/39Ar法和U-Pb法在构造热过程研究中有何不同的应用?本文对这些问题进行了思考和讨论,以期推动大家对40Ar/39Ar年代学的深入探索,推动其在我国地质研究中的应用。     

高频红外法测定石墨样品中的固定碳

采用硝酸酸化处理,低温焙烧氧化除去无机碳及有机碳,样品于高频红外碳硫分析仪测定固定碳质量分数,经国家标准物质验证,测定值与标准值相符,方法精密度RSD%为0.71,检出限为0.02%,满足石墨低品位固定碳质量分数分析质量要求。     

较低稀释比熔片制样X射线荧光光谱法测定磷矿石中12种主次痕量组分

当前应用X射线荧光光谱熔片制样技术分析测定较低含量、低荧光产额氟组分时,准确度较低,精密度较差、检出限较高。本文运用5:1较低稀释比熔样制片技术,采用波长色散X射线荧光光谱法测定磷矿石中12个主次量组分(F、Na₂O、MgO、Al₂O₃、SiO₂、P₂O₅、K₂O、CaO、TiO₂、MnO、TFe₂O₃和痕量SrO)。采用磷矿石、岩石国家一级标准物质、磷矿石管理样品和人工配制标准样品校准,经验系数法进行基体校正,结果表明12个组分分析方法的精密度和准确度较好,检出限较低,未知样品的分析结果比较满意;氟的精密度、准确度和检出限均好于文献中10:1熔样稀释比得出的结果。该方法解决了压片制样测定氟组分,熔片制样测定其他主次量组分的技术问题,同时也降低了熔片制样技术测定氟的检出限。     

Risk de-aggregation and system reliability analysis of slope stability using representative slip surfaces

This paper develops a risk de-aggregation and system reliability approach to evaluate the slope failure probability, p_f, using representative slip surfaces together with MCS. An efficient procedure is developed to strategically select the candidate representative slip surfaces, and a risk de-aggregation approach is proposed to quantify contribution of each candidate representative slip surface to the p_f, identify the representative slip surfaces, and determine how many representative slip surfaces are needed for estimating the p_f with reasonable accuracy. Risk de-aggregation is performed by collecting the failure samples generated in MCS and analyzing them statistically. The proposed methodology is illustrated through a cohesive soil slope example and validated against results from previous studies. When compared with the previous studies, the proposed approach substantially improves the computational efficiency in probabilistic slope stability analysis. The proposed approach is used to explore the effect of spatial variability on the p_f. It is found that, when spatial variability is ignored or perfect correlation assumed, the p_f of the whole slope system can be solely attributed to a single representative slip surface. In this case, it is theoretically appropriate to use only one slip surface in the reliability analysis. As the spatial variability becomes growingly significant, the number of representative slip surfaces increases, and all representative slip surfaces (i.e., failure modes) contribute more equally to the overall system risk. The variation of failure modes has substantial effect on the p_f, and all representative surfaces have to be incorporated properly in the reliability analysis. The risk de-aggregation and system reliability approach developed in this paper provides a practical and efficient means to incorporate such a variation of failure modes in probabilistic slope stability analysis.     

Granitic and monzonitic rocks dredged from the southeast Australian continental margin

Four Middle Devonian (381 Ma) granodiorite samples have been recovered from two dredge sites approximately 65 km east of Green Cape, New South Wales. The granodiorite samples are similar in age and composition to members of the Moruya Suite and probably form an along‐strike extension of that suite. The location of granodiorite on the southeastern margin requires that a piece of continental lithosphere was located to the present east of the study area in the Devonian. This piece of lithosphere may now be located somewhere on the western Lord Howe Rise.

A sample of Early Cretaceous leuco‐quartz monzodiorite was also recovered from a dredge site approximately 45 km north‐northeast of Dalmeny, New South Wales. It represents a body that was intruded at essentially the same time as, and is inferred to be of similar origin to, the syenite rocks of the nearby Mt Dromedary and Montague Island complexes.     

玉龙雪山西麓原状冰碛土CT扫描试验研究

冰碛土是冰川行进融化过程中漂石、碎石、砂砾、粉土和黏土在毫无分选的条件下快速混杂堆积生成的一种特殊岩土材料,由其引发的工程问题日益受到岩土工程界关注。砾石颗粒细观组构是冰碛土独特沉积历史的反映,直接影响土体的岩土力学性质,但迫于原状冰碛土样极难取得,岩土工程领域迄今罕有研究。对此,采用人工精细切削的方式,成功取得了玉龙雪山西麓原状冰碛土样,并对取回的6块冰碛土原状样进行了CT扫描,首次获得了冰碛土内部真实细观组构图像。借助Matlab对CT图片进行二值化和消噪处理后,运用常规统计方法对冰碛土内砾石颗粒的面含石量、颗粒定向以及颗粒形状等剖面组构指标进行了描述。结果表明,垂直剖面之间的统计数据差异较小,但垂直剖面与水平剖面之间差异较大。     

地球化学样品分析中污染物研究

样品是地球科学研究工作的根本依据,样品一旦遭受污染,实验结果难免失准,之后的研究过程则是徒劳。这方面的工作较少有人专门研究,但其重要性却不容忽视。试验表明:地化样品在前处理和保存过程中,很容易被污染,而污染物的主要成分与地化样品的成分极为相似,这就意味着地化样品一旦被污染,很难区分哪些是污染物,哪些是样品本身固有的成分,不仅会对实验结果造成干扰,甚至会完全掩盖地质样品的原貌,误导研究工作,给科研和生产带来损失。