Effects of CH4 and CO on the reduction of nitric oxide to nitrogen in a discharge reactor

Additives are often added to enhance the efficiency of NO removal. This study uses a radio frequency (rf) discharge to consider the effect of added CH4 and CO to simulated NO/N2/O2/H2O mixtures on the elevation of NO conversion and the reduction of NO into N2. The enhancement levels of NO conversion when using various additives were found to be in this order: +CH4 > +CO > no additive. NO conversion reached 99.3%, 86.2%, and 77.6% when adding CH4, CO, and without additive, respectively, at inlet additive/NO molar ratio (R) = 5 and at 120 W. Moreover, the fraction of total N atoms converted from NO into N2 (FN2) was very high, reaching 99.4% and 99.5% when adding CH4 and CO, respectively, at R = 1 and at 120 W. The better operating conditions are using CH4 as the additive at R > or = 1 and a power of > 60 W to reach a higher NO conversion with a higher FN2. However, it should be noted that this rf plasma approach is not practical at this stage because of its relative low pressure.     

Structural and functional variations of phytoplankton communities in the face of multiple disturbances

The global decline of freshwater biodiversity caused by climate change and human activities are supposed to disrupt ecosystem services related to water quality and alter the structure and function of aquatic communities across space and time, yet the effects of the combination of these factors on plankton community ecosystem has received relatively little attention. This study aimed to explore the impacts of disturbances (e.g. human activity, temperature, precipitation, and water level) on phytoplankton community structure (i.e. community evenness and community composition) and function (i.e. resource use efficiency) in four subtropical reservoirs over 7 years from 2010 to 2016. Our results showed that community turnover (measured as community dissimilarity) was positively related to disturbance frequency, but no significant correlation was found between phytoplankton biodiversity (i.e. evenness) and disturbance frequency. Phytoplankton resource use efficiency (RUE = phytoplankton biomass/ total phosphorus) was increased with a higher frequency of disturbance with an exception of cyanobacteria. The RUE of Cyanobacteria and diatoms showed significantly negative correlations with their community evenness, while the RUE of Chlorophyta exhibited a positive correlation with their community turnover. We suggest that multiple environmental disturbances may play crucial roles in shaping the structure and functioning of plankton communities in subtropical reservoirs, and mechanism of this process can provide key information for freshwater uses, management and conservation.     

Evaluation of an In Situ,On-Line Purging System for the Cone Penetrometer

Abstract

Materials that will be used to construct an in situ, on-line purging system for the cone penetrometer were evaluated. Transfer efficiencies for volatile organic compounds (VOCs) through stainless steel, nickel, aluminum, and Teflon® tubings were determined using a gas-phase mixture of VOCs containing trichloromethane, tetrachloromethane, 1,1,1- trichloroethane, tetrachloroethene, hexane, benzene, toluene, and 1,2-dimethylbenzene. The water content of the gas stream had an insignificant effect on the quantitative transfer of VOCs through Teflon® tubing but was critical to efficiently transfer the compounds through metal tubing, particularly nickel. Transfer efficiencies for all eight analytes in moist gas streams through stainless steel were greater than 95%. Toluene, tetrachloroethene, and 1,2-dimethylbenzene were transferred with 93%, 81%, and 80% efficiency, respectively, when they were drawn through Teflon® PFA (perfluoroalkoxy) tubing. In general, the retention of the VOCs by Teflon® increases with decreasing aqueous solubility of the analyte. The efficiencies at which VOCs were purged from aqueous standards in Teflon® PFA, Type 304 stainless steel, and glass vessels were similar. Stainless steel was superior to nickel, aluminum, and the Teflon® polymers as a material for an in situ, on-line purging system for the cone penetrometer.     

Characteristic Study of Ambient Air Total Gaseous Mercury (TGM) Concentrations During Rainy and Non-Rainy Periods at a Traffic Site in Taiwan

This investigation studied the concentrations of ambient air total gaseous mercury (TGM) during the rainy periods at the Hung-Kuang traffic sampling site in central Taiwan from May 26 to June 16, 2014. The results were compared with those of a previous study for ambient air TGM during non-rainy daytime and nighttime periods at the Hung-Kuang traffic sampling site, which was conducted during March 21 to July 20, 2012. The observed mean concentration of ambient air TGM was 1.16 ng/m³ during the rainy periods at the Hung-Kuang traffic sampling site. The mean ambient air TGM concentrations were higher in the non-rainy sampling period in daytime than in the rainy sampling period from this study. The mean ratio of non-rainy sampling period in daytime to that of rainy sampling period for ambient air TGM were 3.15. Furthermore, the mean ambient air TGM concentrations were higher in the non-rainy sampling period in nighttime in than in the rainy sampling period for this study. The mean rations for non-rainy sampling period in nighttime to that of the rainy sampling period for ambient air TGM were 2.70. The results obtained in this study also revealed that the ambient air TGM concentrations during the rainy period had the lowest concentrations when compared with the other sampling sites in other world regions.     

Assessment of Organochlorine Pesticide Residues in Water,Sediment, and Fish of the Songhua River,China

This study examined residual concentrations and associated ecological risks of the organochlorine pesticides (OCPs) hexa- chlorocyclohexane (HCH) and dichloro-diphenyl-trichloroethane (DDT) in water, sediment, and fish of the Songhua River in Zhaoyuan County, China. In June 2012, 10 water, 10 sediment, and 20 fish samples were collected. Residual concentrations of ΣHCH and ΣDDT ranged from 10.0–35.59 ng L^?1 (mean 28.03 ± 11.66 ng L^?1) and 5.12–39.66 ng L^?1 (mean 32.36 ± 11.58 ng L^?1) for water. Residual concentrations of ΣHCH and ΣDDT ranged from 0.52–3.00 ng g^?1 (mean 2.04 ± 0.73 ng g^?1) and 0.34–3.41 ng g^?1 (mean 2.38 ± 0.92 ng g^?1) for sediment. The ratios of α-HCH/γ-HCH were close to 1 at the majority of sampling points, indicating considerable new pollution from the use of lindane. The ratios of p,p′-DDE + p,p′-DDD/ΣDDT were less than 0.5, indicating recent inputs from DDT impurities in dicofol. All HCH and DDT isomers except for p,p′-DDD were detected in fish tissue samples, but the associated ecological risks were estimated to be below levels of concern. The study revealed a historical usage of OCPs in the Zhaoyuan section of the Songhua River and new OCP from the use of lindane and dicofol.     

Polycyclic aromatic hydrocarbons in household dust near diesel transport routes

A river-dredging project has been undertaken in Nantou, Taiwan. A large number of diesel vehicles carrying gravel and sand shuttle back and forth on the main roads. Ten stations along major thoroughfares were selected as the exposure sites for testing, while a small village located about 9 km from a main traffic route was selected as the control site. Levels of household dust loading at the exposure sites (60.3 mg/m²) were significantly higher than those at the control site (38.2 mg/m²). The loading (μg/m²) of t-PAHs (total polycyclic aromatic hydrocarbons) in the household dust at the exposure sites was significantly higher (P < 0.05) than was the case at the control site. The diagnostic ratios of PAHs showed that diesel emissions were the dominant source of PAHs at the exposure sites. The lack of a significant correlation between the concentrations of Fe and t-PAHs suggested that the t-PAHs in household dust might come from diverse sources. However, a significant correlation (P = 0.003) between the concentrations of Mo and t-PAHs implied that the most of the t-PAHs in the household dust might have resulted from diesel emissions. The lifetime cancer risks of BaP_eq from household dust exposure were markedly higher than those resulting from inhalation exposure.     

近20年来鄱阳湖流域泛滥平原沉积物微量元素含量与污染变化

查明鄱阳湖流域微量元素的污染状况、识别其潜在来源并评估生态风险,对制定保护流域生态系统的有效策略至关重要.为了全面了解鄱阳湖流域5条主要支流泛滥平原沉积物中Cd、Hg、Pb、As、Cu、Zn、Cr、Ni、Mn、Sb、W和Sn等12种微量元素间隔近20 a的含量、污染水平和生态风险的时空变化状况,采用富集因子（EF）和修正综合污染指数（MPI）评价了微量元素的污染水平,应用潜在生态风险因子（E_r）和修正生态风险指数（MRI）量化了微量元素引发的生态风险,并对污染水平显著变化区域的污染源进行了分析和探讨.研究结果显示,近20年来,鄱阳湖流域泛滥平原沉积物中Cd、Zn、Mn、W和Pb含量分别升高了134%、26%、41%、25%和8%,Hg、As、Cr、Ni、Sb和Sn含量分别降低了35%、15%、22%、10%、14%和13%,Cu含量无明显变化;饶河、赣江和信江流域的Cd含量分别升高了331%、151%和107%,抚河、赣江和修水流域的Hg含量分别降低了87%、41%和40%;其污染变化主要表现为Cd污染加剧和Hg污染降级,整个赣江流域Cd污染升级至中度和中度-重度,饶河乐安江Cd污染升级至重度,抚河流域Hg污染降至无或轻微;Cd污染加剧导致综合污染升级,极度和重度污染点位比例由17%升至33%;极高生态风险点位的比例由11%升至22%,其高MRI贡献率元素由Hg变为Cd,源于Hg污染的极高生态风险点降至中等生态风险.鄱阳湖流域泛滥平原沉积物中微量元素的显著污染变化主要源于矿产开发与冶炼、工业和农业生产等人为活动.研究成果可为河流污染防治和流域生态系统的优化管理提供科学依据.     

Stabilization of residues obtained from the treatment of laboratory waste: Part 2--transformation of plasma vitrified slag into composites

The Sustainable Environment Research Center of National Cheng Kung University in Taiwan has set up a treatment plant to dispose of laboratory waste. In the treatment process, the residue from the incineration system and the physical and chemical system is vitrified by a plasma melting system. Part 1 of this study described the treatment path of metals during vitrification. In Part 2, plasma vitrified slag is reused by using a molding technology. Unsaturated polyester resin and glass fiber were used as the molding material and additive, respectively, in the molding process. With an appropriate mixing ratio of unsaturated polyester resin, glass fiber, and slag, the physical properties of composites improved, and the ultimate tensile strength reached 17.6 MPa. However, an excess amount of slag reduced the strength and even retarded the production of composites. Differential thermal analysis and the water bathing test results show that the composite decomposed at 80 degrees C and that it vaporized at 187 degrees C. Although the unsaturated polyester resin decomposed, the metal encapsulated in the slag did not leach out. The results show that the reuse of slag using molding technology should be taken into consideration.     

Role of sodium ions in the vitrification process: Glass matrix modification,slag structure depolymerization,and influence of metal immobilization

This study investigates the role of Na ions, a common flux, in the vitrification process. Artificial glass systems composed of Al₂O₃, CaO, and SiO₂ with various Na concentrations were melted at 1450 °C. The specimens were cooled by air cooling and water quenching and the metal mobility was evaluated using a sequential extraction procedure. The X-ray diffraction analysis and scanning electron microscopy observations showed that Na ions governed the air-cooled slag’s structure. Na ions initially depolymerized CaSiO₃-linked chains into CaSiO₃ chains, and further cut them into shorter and nonuniform ones, making the slag structure amorphous. With even more Na ions, CaSiO₃ chains were divided into single SiO₄ tetrahedrons and formed Na-related crystals (Na₂Ca₃Si₂O₈ and NaAlSiO₄). The phase distributions of Al, Cr, Cu Mn, and Ni showed that Na has a positive effect on the immobilization of heavy metals at suitable concentrations, but a negative effect when in excess amounts.

Implications:Vitrification has been widely used to treat hazardous materials. The Na-bearing additives were often used as a flux to improve the melting process. This study described the role of Na played in the vitrification process. The Na ions acted as glass modifier and depolymerize the chain structure of slag. With adequate addition amount of Na ions, the immobilization of heavy metals was improved. The results provided much information about the crystalline phase variation, metal mobility, and surface characteristics while Na serves as a flux.     

Preparation and Properties of Poly (Lactic Acid) Nanocomposites Filled with Functionalized Single-Walled Carbon Nanotubes

This work prepared poly (lactic acid) (PLA)/single-walled carbon nanotubes (SWCNTs) composites using a solution blend method, and investigated the influence of the physical properties of PLA/SWCNTs composites. In order to enhanced interfacial interactions between PLA and SWCNTs, the purified SWCNTs were given functionalisation treatments with a nitric acid/sulfuric acid mixture. These acid-treated SWCNTs (A-SWCNTs) were then grafted with 3-isocyanatopropyl triethoxysilane (A-SWCNTs-Si). When these functionalized SWCNTs were used to fill the PLA matrix, the fractured surface of composite does not present the pullout phenomenon. The dimensional stability obviously increased by a factor of approximately 72. The storage modulus was also significantly improved. The surface resistivity of the PLA/SWCNTs composites decreased from 1 × 10¹⁶ to 2.22 × 10⁴ Ω/cm².