Sampling and analysis of volatile organics emitted from wastewater treatment plant and drain system of an industrial science park

Volatile organic compounds (VOCs) were monitored in the different sections of a wastewater treatment plant (WWTP), the outlet of both the WWTP and rainfall water, and the downstream of the WWTP joining the river in the area or vicinity of an industrial science park located in Hsinchu, Taiwan. Levels of VOCs were determined by collecting air samples over several sampling points and analyzed using gas chromatography. Among VOCs identified in the drainage and effluent system in each season, acetone, isopropanol (IPA) and dimethyl sulfide (DMS) were the major emission species and maximum concentrations were 400.4, 22.8 and 641.2 ppbv, respectively. The ambient air and wastewater sample analysis from neighboring wastewater streams identified pollutants being discharged from unaccounted sources other than the industrial park. According to the 24 h semi-continuous monitoring data (27/7/2002-29/7/2002), the total VOC concentration was an average of 93 ppbv (acetone contributed ∼78%) with a dramatic variation during the day and night. The emission rate of measured VOCs estimated using fixed box model projected an average of 2-4 μg m⁻² h⁻¹) during the day and 9-17 μg m⁻² h⁻¹ during the night. In addition, the isopleth maps show that the acetone and DMS emissions influence adversely the nearby residential area located at less than 100 m downwind from the plant. Eventually, based on this study, an on-line monitoring and alerting system could be built for a long-term performance, and with regular information on the varying pollutants over time construction of a green strategy and creation of a sustainable environment can be achieved.     

Measurement of non-methane hydrocarbons in Taipei city and their impact on ozone formation in relation to air quality

Air pollutants data from semi-continuous measurements at multiple sampling sites in Taipei metropolitan area of Taiwan was obtained by collecting air samples in canisters. The hydrocarbon composition was determined by using GC/MS and GC/FID. The air samples were pre-concentrated onto glass beads prior to separation by PLOT and DB-1 columns of GC. The method showed detection limit of <1 ppb and relative standard deviation in the range of 5-30% for different compounds. Aromatic hydrocarbons (toluene, benzene, etc.) and aliphatic hydrocarbons (ethylene, acetylene, propane, etc.) were correlated primarily to determine the source of emission. The estimated hydrocarbons were ranked according to their abundance and photochemical reactivity. The criteria pollutants, ozone and NO₂ were measured by UV-differential optical absorption spectroscopy (UV-DOAS), and were utilized to determine the relative importance of non-methane hydrocarbons (NMHC) and significant contribution of NO₂ in limiting ozone formation. The obtained results suggest that ozone formation in Taipei city is probably limited by the supply of non-methane hydrocarbons. The concentration profile of targeted pollutants was compared to other metropolitan areas to determine air quality and the pollutant sources.     

重金属的生物吸附机理及吸附平衡模式研究*

各种生物吸附剂包括海洋微生物、发酵工业的菌丝体废渣及活性污泥的提取物等对金属离子的吸附特性已被广泛研究,本文就生物体对金属离子的吸附机理及吸附平衡模式研究进行了综述,阐明了今后的研究方向。     

Temperature dependent responsivity of quantum dot infrared photodetectors

Temperature dependent behavior of the responsivity of InAs/GaAs quantum dot infrared photodetectors was investigated with detailed measurement of the current gain. The current gain varied about two orders of magnitude with 100 K temperature change. Meanwhile, the change in quantum efficiency is within a factor of 10. The dramatic change of the current gain is explained by the repulsive coulomb potential of the extra carriers in the QDs. With the measured current gain, the extra carrier number in QDs was calculated. More than one electron per QD could be captured as the dark current increases at 150 K. The extra electrons in the QDs elevated the Fermi level and changed the quantum efficiency of the QDIPs. The temperature dependence of the responsivity was qualitatively explained with the extra electrons.     

Direct fabrication and IV characterization of sub-surface conductive channels in diamond with MeV ion implantation

In the present work we report about the investigation of the conduction mechanism of sp² carbon micro-channels in single crystal diamond. The structures are fabricated with a technique which employs a MeV focused ion-beam to damage diamond in conjunction with variable thickness masks. This process changes significantly the structural properties of the target material, because the ion nuclear energy loss induces carbon conversion from sp³ to sp² state mainly at the end of range of the ions (few micrometers). Furthermore, placing a mask with increasing thickness on the sample it is possible to modulate the channels depth at their endpoints, allowing their electrical connection with the surface. A single-crystal HPHT diamond sample was implanted with 1.8 MeV He⁺ ions at room temperature, the implantation fluence was set in the range 2.1×10¹⁶-6.3×10¹⁷ ions cm^-2, determining the formation of micro-channels with a graded level of damage extending down to a depth of about 3 μm. After deposition of metallic contacts at the channels’ endpoints, the electrical characterization was performed measuring the I-V curves at variable temperatures in the 80-690 K range. The Variable Range Hopping model was used to fit the experimental data in the ohmic regime, allowing the estimation of characteristic parameters such as the density of localized states at the Fermi level. A value of 5.5×10¹⁷ states cm^-3 eV^-1 was obtained, in satisfactory agreement with values previously reported in literature. The power-law dependence between current and voltage is consistent with the space charge limited mechanism at moderate electric fields.     

Endemic infrared divergences in QED3 at finite temperature

We demonstrate that massless QED in three dimensions contains endemic infrared divergences. It is argued that these divergences do not affect observables; furthermore, it is possible to choose a gauge that renders the theory finite.     

On the cryogenic magnetic transition and martensitic transformation of the austenite phase of 7MoPLUS duplex stainless steel

The magnetic behaviour and martensitic transformation at cryogenic temperatures (down to 4 K) of the austenite phase of the duplex stainless steel (DSS), 7MoPLUS, were studied. As regards the prediction of Neel temperature, the empirical expressions for austenitic stainless steels are not applicable to the austenite phase of 7MoPLUS, although the composition of the austenite phase falls within the composition ranges within which the expressions were developed. Regarding the prediction of martensitic point Ms, the applicability of ‘old’ and recently developed expressions has been examined. The recently developed expressions, which take into account more alloying elements and their interactions, are not suitable for the austenite phase of 7MoPLUS. But for the ‘old’, simpler expressions, they seem to be valid in the sense that they all predict high stability of the austenite phase. Results obtained from 7MoPLUS were qualitatively the same as those obtained from another DSS, designated as 2205. Reasons for the applicability and inapplicability of these empirical expressions are suggested.     

Base-induced photorearrangements from 3-styrylfurans to 2-methylnaphthalenes

Irradiation of 3-(4-substituted styryl)furans in basic media yielded a series of 7-substituted-2-methylnaphthalenes, including methoxy, isopropyl, ethyl, methyl, fluoro, and cyano substituents. This base-induced photorearrangement involves cis-trans photoisomerization, 6e photocyclization, base-induced elimination, and a Norrish Type I photoreaction and is a novel method to synthesize unsymmetrical 2,7-disubstituted naphthalenes.