某深基坑支护设计及监测分析

以广州南方房产大厦深基坑支护结构为例,介绍了深基坑支护的设计指导思想和监测。文中介绍的方法对类似工程的设计有一定指导意义。     

应用岩体声发射技术监测采场顶板稳定性的研究

该矿南矿带自1992年采用上向水平分层进路式充填法开采以来,由于采场顶板的矿岩裸露,易发生冒顶事故,为了寻求对顶板的监测预报的手段,1994年冶金工业部安全环保研究院和我矿共同开展岩体声发射技术应用研究。在此基础上,我矿利用YSS型岩体声发射监测仪对南矿带上向采场的岩体声发射参数进行监测收集、整理分析,并结合现场情况判断采场顶板的稳定性,对有冒落可能的作出预报,进而采取措施避免事故发生。     

Direct spectral analysis and determination of high content of carcinogenic bromine in bread using UV pulsed laser induced breakdown spectroscopy

Laser induced breakdown spectroscopy (LIBS) was applied for the detection of carcinogenic elements like bromine in four representative brands of loaf bread samples and the measured bromine concentrations were 352, 157, 451, and 311 ppm, using Br I (827.2 nm) atomic transition line as the finger print atomic transition. Our LIBS system is equipped with a pulsed laser of wavelength 266 nm with energy 25 mJ pulse^?1, 8 ns pulse duration, 20 Hz repetition rate, and a gated ICCD camera. The LIBS system was calibrated with the standards of known concentrations in the sample (bread) matrix and such plot is linear in 20–500 ppm range. The capability of our system in terms of limit of detection and relative accuracy with respect to the standard inductively coupled plasma mass spectrometry (ICPMS) technique was evaluated and these values were 5.09 ppm and 0.01–0.05, respectively, which ensures the applicability of our system for Br trace level detection, and LIBS results are in excellent agreement with that of ICPMS results.     

Method of median semi-variance for the analysis of left-censored data: Comparison with other techniques using environmental data

In environmental monitoring, variables with analytically non-detected values are commonly encountered. For the statistical evaluation of these data, most of the methods that produce a less biased performance require specific computer programs. In this paper, a statistical method based on the median semi-variance (SemiV) is proposed to estimate the position and spread statistics in a dataset with single left-censoring. The performances of the SemiV method and 12 other statistical methods are evaluated using real and complete datasets. The performances of all the methods are influenced by the percentage of censored data. In general, the simple substitution and deletion methods showed biased performance, with exceptions for L/2, Inter and L/√2 methods that can be used with caution under specific conditions. In general, the SemiV method and other parametric methods showed similar performances and were less biased than other methods. The SemiV method is a simple and accurate procedure that can be used in the analysis of datasets with less than 50% of left-censored data.     

The joint effects of sulfonamides and their potentiator on Photobacterium phosphoreum: differences between the acute and chronic mixture toxicity mechanisms

Organisms are typically exposed to mixtures of chemicals over long periods of time; thus, chronic mixture toxicity analysis is the best way to perform risk assessment in regards to organisms. However, most studies focus on the acute mixture toxicity. To investigate the difference between chronic mixture toxicity and acute mixture toxicity, Photobacterium phosphoreum were exposed to chronic (24 h exposure) and acute (15 min exposure) toxicity of single sulfonamide (SA) and their potentiator (trimethoprim, TMP), both individually and mixtures (SA with TMP). A comparison of chronic vs. acute mixture toxicity revealed the presence of an interesting phenomenon, that is, that the joint effects vary with the duration of exposure; the acute mixture toxicity was antagonistic, whereas the chronic mixture toxicity was synergistic. Based on the approach of Quantitative Structure Activity Relationships (QSARs) and molecular docking, this phenomenon was proved to be caused by the presence of two points of dissimilarity between the acute and chronic mixture toxicity mechanism: (1) the receptor protein of SAs in acute toxicity was Luc, while in chronic toxicity it was Dhps, and (2) there is a difference between actual concentration of binding-Luc in acute toxicity and individual binding-Dhps in chronic toxicity. This deep insight into the difference between chronic and acute mixture toxicity will benefit environmental science, medical science, and other disciplines. The existence of these differences poses a challenge for the assessment of routine combinations in medicine, risk assessment, and mixture pollutant control, in which, previously, only a synergistic effect has been observed between SA and their potentiator.     

农药厂周边有机磷农药在生物体中残留的检测方法研究

测定南京某农药厂附近大米、蔬菜及肉类中11种有机磷农药含量,通过使用气相色谱/质谱联用的方法,建立GC／MS定性定量分析方法,检出限达到0．05μg／kg（肉类）和0．1μg／kg（大米和蔬菜）,回收率均符合测定要求。环境样品监测结果显示,大米和蔬菜中有机磷农药的含量高于肉类中的含量,说明在大米和蔬菜表面残留的农药量要高于进入生物体体内的含量。南京蔬菜样品中有机磷农药高于常州蔬菜样品,说明农药厂对蔬菜表面残留农药量有影响。不同的有机磷农药在不同的介质中,检出情况不一样,说明不同的环境介质对有机磷农药的保留水平不一样。     

地下轨道交通结构噪声与振动频率特性分析

通过研究地下轨道交通现行国家标准与地方标准监测方法与评价量,探讨标准中存在的不足之处。并通过对受地下轨道交通运行过程影响的建筑物进行室内噪声与振动实地测试和数据分析,大胆提出了监测地下轨道交通排放的新思路。即采用1/3倍频程时间历程方法对列车通过全过程产生的结构传声排放与振动排放全时记录,借鉴声暴露级的方法,通过实测各频率数值变化截取列车通过时噪声事件的振动分频振级与结构传声1/3倍频程声压级。对此种方法的数据结果进行各频率噪声与振动相关性分析,得出地下轨道交通运行所产生结构传声污染排放的低频排放特性。通过研究和测量发现,轨道交通所引起的室内结构传声与振动污染能量主要集中于500 Hz 以下低频部分,其峰值出现于40～60 Hz 附近。将其与现行国家或地方标准进行比较,提出了采用特征频率作为事件判别的依据,并将各事件的最终测量结果以低频分频数据进行评价的方式,最终归纳总结了实际地下轨道交通排放频率特性并展望其测量方法。     

不同环境介质中抗生素的污染现状及其检测方法研究进展

综述了环境中抗生素的来源、国内外不同环境介质中抗生素的污染水平及检测方法。现有研究表明,抗生素污染已遍布土壤、水体、动植物组织等介质中,且国内抗生素污染水平较国外相对偏高。通过不同检测技术的优劣对比,得出固相萃取技术与液相色谱质谱联用技术是目前最常用的样品前处理技术和检测方法,具有灵敏度高和精确度好的特点。     

如何降低水中VOC分析的检测限

环境中挥发性有机污染物（ＶＯＣ）的存在很复杂,随着ＶＯＣ治理的进步,环境水中ＶＯＣ浓度有不断降低的趋势,要求ＶＯＣ分析具有更低的检测限。通过对环境水前处理过程采用优化吹扫捕集条件来扩大试样量,选择高灵敏度的检测器以及降低前处理过程的空白值,提纯分析用水;优化ＶＯＣ色谱分离条件,确保色谱峰良好分离来降低试样和空白值的标准偏差的研究,表明可以有效降低水中ＶＯＣ分析方法的检测限。     

常州市扁担河桥断面水质提升方案研究

河流断面水质受到多种因素的影响,当前区域水环境整治方案的制定常常只是笼统地从工业、农业、生活污染控制方面提出一些措施,实际工作中缺乏有针对性的水质提升方案。以常州市扁担河桥断面为研究对象,在污染构成测算和削减目标计算的基础上,制定系统的、切实可行的水质提升方案,并对方案的可达性进行对比分析。通过测算2012年扁担河桥断面需要削减氨氮为59.45t/a,通过水质提升方案的实施,形成削减能力氨氮64.2t/a。