Characterization of colloidal arsenic at two abandoned gold mine sites in Nova Scotia, Canada, using asymmetric flow-field flow fractionation-inductively coupled plasma mass spectrometry

Asymmetric flow-field flow fractionation-inductively-coupled plasma-mass spectrometry was used to determine whether colloidal arsenic(As) exists in soil pore water and soil extract samples at two arsenic-contaminated abandoned gold mines(Montague and Goldenville, Nova Scotia). Colloidal arsenic was found in 12 out of the 80 collected samples(= 15%), and was primarily associated with iron(Fe) in the encountered colloids. The molar Fe/As ratios indicate that the colloids in some samples appeared to be discrete iron–arsenic minerals, whereas in other samples, they were more consistent with As-rich iron(oxy)hydroxides. Up to three discrete size fractions of colloidal As were encountered in the samples, with mean colloid diameters between 6 and 14 nm. The pore water samples only contained one size fraction of As-bearing colloids(around 6 nm diameter), while larger As-bearing colloids were only encountered in soil extracts.     

华东某铀矿区地表水中放射性核素铀含量特征分析

以华东某铀矿区为研究对象,利用X-Series II电感耦合等离子体质谱仪测定铀矿区和对照区共114个地表水样品中放射性核素铀含量,采用单因子指数法评价放射性铀污染,以查明铀矿区地表水铀污染现状。结果表明:(1)研究区地表水铀平均含量39.89μg/L,分别是含矿未采区、江西省背景值、对照区的32.17倍、64.34倍和199.45倍;各亚区地表水的铀含量平均值从大到小顺序为:水冶场区开采矿井区废弃矿井区尾矿库区;废弃矿井区、水冶场区、开采矿井区等亚区地表水铀含量受到较强人为活动影响;(2)单因子污染指数评价结果表明各亚区地表水铀污染程度为:水冶场区开采矿井区废弃矿井区尾矿库区。其中,水冶场区、开采矿井区、废弃矿井区、尾矿库区地表水的铀污染程度均为重度污染;对照区未污染。结合研究区铀含量特征,铀矿开采、运输与选冶等实际情况,建议从改善矿石运输条件、改善废水处理设备,提高废水处理技术等方面进行地表水铀污染防治。     

Disposal of hexachlorodisilane and its hydrolyzed deposits

Hexachlorodisilane (Si₂Cl₆, HCDS) is an important precursor used in semiconductor device manufacturing. It is a flammable as well as a water reactive liquid which hydrolyzes rapidly upon contact with water or moisture. The hydrolyzed deposits are also known to be shock-sensitive with explosion energy equivalent to trinitrotoluene (TNT). In this work, two phases of test program including disposal of HCDS and disposal of the shock sensitive HCDS hydrolyzed deposits were conducted. The first phase of the program was to find an agent that can completely dissolve/react the HCDS vapor without forming shock sensitive deposits. The second phase of the program attempted to find a suitable agent to suppress the Si–Si bonds, one of the essential roles of chemical functional groups in shock sensitivity of the HCDS hydrolyzed deposits to suppress the shock sensitivity. A variety of agents such as sulfuric acid solutions, aqueous sodium hydroxide (NaOH) solutions, aqueous potassium hydroxide (KOH) solutions, KOH/alcohol solutions were utilized as the suppressants in this work. Samples mixed with suppressants were not only tested for shock sensitivity by a Fall-hammer apparatus but also analyzed for chemical functional groups to identify the effect of each agent. Concentrated sulfuric acid was found to suppress the shock sensitivity of the liquid HCDS hydrolyzed deposits by acting as a medium that helps the hydrolyzed deposit to retain moisture. KOH/alcohol solutions can turn HCDS vapor into non-hazardous silica, so that, it provided a safe way to dispose HCDS. Finally, practical recommendations about handling and eliminating the risk of shock sensitivity are given for HCDS liquid spill, HCDS vapor vent and HCDS hydrolyzed deposits.     

贵州开阳磷矿洋水矿区环境地质问题分析

由于开磷矿区地处山区,矿区自然地质条件较差,地表切割强烈,沟谷纵横,加之建矿几十年的矿山开采, 尤其是近十几年来个别乡镇企业对矿山掠夺性开采,矿区引发了一系列的环境地质问题,如山体崩塌,水土大量流失、滑坡、泥石流等地质灾害,本文通过对开阳磷矿洋水矿区环境地质问题及主要成因进行分析,提出因地制宜地采取有效措施控制、防止不良地质现象和地质作用的发生发展,合理地利用环境资源,加快对人为破坏活动的治理,稳步恢复区域生态系统的良性循环,以达到生态的最佳效益。     

Photocatalytic reduction of organic pollutant under visible light by green route synthesized gold nanoparticles

We report a rapid method of green chemistry approach for synthesis of gold nanoparticles(AuNPs)using Lagerstroemia speciosa leaf extract(LSE). L. speciosa plant extract is known for its effective treatment of diabetes and kidney related problems. The green synthesis of Au NPs was complete within 30 min at 25°C. The same could also be achieved within 2 min at a higher reaction temperature(80°C). Both UV–visible spectroscopy and transmission electron microscopy results suggest that the morphology and size distribution of Au NPs are dependent on the pH of gold solution,gold concentration,volume of LSE,and reaction time and temperature. Comparison between Fourier transform infrared spectroscopy(FT-IR)spectra of LSE and the synthesized Au NPs indicate an active role of polyphenolic functional groups(from gallotannins,lagerstroemin,and corosolic acid)in the green synthesis and capping of Au NPs. The green route synthesized Au NPs show strong photocatalytic activity in the reduction of dyes viz.,methylene blue,methyl orange,bromophenol blue and bromocresol green,and 4-nitrophenol under visible light in the presence of Na BH_4. The non-toxic and cost effective LSE mediated Au NPs synthesis proposed in this study is extremely rapid compared to the other reported methods that require hours to days for complete synthesis of Au NPs using various plant extracts. Strong and stable photocatalytic behavior makes Au NPs attractive in environmental applications,particularly in the reduction of organic pollutants in wastewater.     

Investigation on the urea deposit formation and thermal decomposition characteristics in the SCR aftertreatment system of a diesel engine

Selective catalytic reduction is the most efficient and reliable equipment for NOx control in current diesel engines. However, the issue of urea crystallization becomes increasingly serious with the implement of the new emissions standards. In this paper, urea deposit samples collected from engine test bed and tube furnace were characterized by thermogravimetric analysis and Fourier transform-infrared analysis to aid the comprehension of urea deposit formation. Moreover, thermogravimetric tests were conducted to disclose the effects of catalyst on the thermal decomposition processes of urea deposit. The results indicated that less temperature resistant species are formed in the engine test bed than in the tube furnace at conditions with the same temperatures. The main compositions in the World Harmonized Transient Cycle (WHTC) urea deposits are urea, cyanuric acid (CYA) and ammelide, implying that accelerating the decomposition of these species could prevent the accumulation of urea deposit. CuWTi, Cuβ and CuZSM catalysts could lead to increased yield of CYA during pure urea thermolysis. Cuβ, CuWTi and VWTi catalysts tend to promote the thermolysis of CYA while VWTi has the most significant catalytic effects on the thermal decomposition of ammelide and ammeline.     

±500kV直流复合绝缘子沿串积污特性研究

复合绝缘子的积污特性与瓷绝缘子和玻璃绝缘子有所不同,研究其积污规律对防止污闪有着重要意义。为此,以3支实际运行后的±500kV直流复合绝缘子为研究对象,系统测量其沿串不同位置的污秽度,用等值盐密(ESDD)和灰密(NSDD)表征。试验发现绝缘子不同伞上下表面的等值盐密和灰密大多呈现出U形的分布规律,尤其以等值盐密的U形分布更为明显,而且不同伞上下表面污秽U形分布规律性的强弱有一定差异。讨论了积污过程中电场对污秽沉积的作用以及自清洗过程中雨水冲洗的随机作用,更好地解释了直流复合绝缘子的沿串积污规律。     

The onset of surface-enhanced Raman scattering for single-particle detection of submicroplastics

Microplastics represent an emerging environmental problem worldwide, raising ecological and food safety concerns. Compared to microplastics, there is growing evidence of an even higher abundance of submicro- and nanoplastics in the environment, but a reliable monitoring method for detecting these smaller-sized plastics is lacking. Herein we presented the application of surface-enhanced Raman scattering (SERS) for this purpose. Particles of polystyrene (PS; 600 nm) were used as the probe analyte. Gold nanourchins (AuNU; 50 nm), i.e. urchin-shaped nanoparticles with irregular spikes around the core, were used as the SERS-active substrate. The effectiveness of SERS on PS was evaluated at a single-particle level with different numbers of AuNU in order to determine the minimum conditions required for the onset of the SERS effect. Our findings suggest that SERS of a single particle of PS can be induced by as few as 1–5 particles of AuNU, and that the use of excitation wavelength at 785 nm is appropriate to meet the red-shifted surface plasmon resonance of AuNU upon aggregation. These specifications provide additional information for the development of SERS-based tools for detecting plastic particles < 1 µm in food and environmental samples.     

淡水沼泽湿地泥炭沉积中氮素分布特征

采用冬季采样,现场分层的方法,系统地研究了我国面积最大的淡水沼泽湿地--三江平原沼泽湿地中河床-河漫滩型泥炭地和谷底洼地型泥炭沉积中TN、NH₄⁺-N和NO₃^--N的分布特征.结果表明,在不同沉积层中,NH₄⁺-N、NO₃^--N明显富集于Aso层,TN在Hil层含量最高.TN含量随着泥炭粒级的减小而明显增加,NH₄⁺-N主要分布在粒级0.149～0.074mm的泥炭机械组分中,NO₃^--N主要分布在粒级0.03～0.149mm的泥炭机械组分中.     

Technology,managerial, and policy initiatives for improving environmental performance in small-scale gold mining industry

This paper reviews a series of strategies for improving environmental performance in the small-scale gold mining industry. Although conditions vary regionally, few regulations and policies exist specifically for small-scale gold mining activity. Furthermore, because environmental awareness is low in most developing countries, sites typically feature rudimentary technologies and poor management practices. A combination of policy-, managerial- and technology-related initiatives is needed to facilitate environmental improvement in the industry. Following a broad overview of these initiatives, a recommended strategy is put forth for governments keen on improving the environmental conditions of resident small-scale gold mines.