Applying model simulation and photochemical indicators to evaluate ozone sensitivity in southern Taiwan

Ozone sensitivity was investigated using CAMx simulations and photochemical indicator ratios at three sites （Pingtung City, Chao-Chou Town, and Kenting Town） in Pingtung County in southern Taiwan during 2003 and 2004. The CAMx simulations compared fairly well with the hourly concentrations of ozone. Simulation results also showed that Pingtung City was mainly a volatile organic compounds （VOC）-sensitive regime, while Chao-Chou Town was either a VOC-sensitive or a NOx-sensitive regime, depending on the seasons. Measurements of three photochemical indicators （H202, HNO3, and NOy） were conducted, and simulated three transition ranges of H202/HNO3 （0.5-0.8）, O3/HNO3 （10.3-16.2） and O3/NOy （5.7-10.8） were adopted to assess the ozone sensitive regime at the three sites. The results indicated that the three transition ranges yield consistent results with CAMx simulations at most times at Pingtung City. However, both VOC-sensitive and NOx-sensitive regimes were important at the rural site Chao-Chou Town. Kenting Town, a touring site at the southern end of Taiwan, was predominated by a NOx-sensitive regime in four seasons.

Emissions of C_2-C_(12) hydrocarbons in the Hsuehshan tunnel,Taiwan

The concentrations of 56 hydrocarbons from C2 to C12 were measured simultaneously in the southbound bore,the northbound bore and the exhaust air shafts of the Hsuehshan tunnel near Yilan,Taiwan for 12 days during 2007 and 2008.A total of 60 integrated air samples were collected using stainless steel canisters and analyzed using GC/FID and GC/MS.The five most abundant species in all samples were ethylene,acetylene,isopentane,propylene and toluene.The exit/entrance ratios of total non-methane hydrocarbons（NMHC） concentration were 7.8 and 4.8 for the southbound and northbound bores,respectively.Furthermore,the exhaust from the vertical shafts a？ects air quality in the neighborhood.The most abundant species of emission rate（ER） was toluene（21.93-42.89 mg/sec）,followed by isopentane,ethylene,propylene and 1-butene,with ER ranging from 2.50 to 9.31 mg/sec.The species in the three exhaust air shafts showed that the reactivities of these emissions are similar to those of vehicle emissions.Notably,the control of emissions in the vertical shafts of the vehicle tunnel will be important in the future.

Rapid synthesis of Ti-MCM-41 by microwave-assisted hydrothermal method towards photocatalytic degradation of oxytetracycline

This study employed microwave-assisted hydrothermal method to synthesize Ti-MCM-41,which are mesoporous materials with a high surface area and excellent photocatalytic ability. Fourier transform infrared spectroscopy（FTIR）, X-ray diffraction（XRD）, X-ray photoelectron spectroscopy（XPS）, transmission electron microscopy（TEM）, and ultraviolet–visible spectroscopy（UV–Vis） were employed. The XRD findings showed that Ti-MCM-41 exhibited a peak at 2θ of 2.2°, which was attributed to the hexagonal MCM-41 structure. The BET（Brunauer–Emmett–Teller） results agreed with the TEM findings that Ti-MCM-41 has a pore size of about 3–5 nm and a high surface area of 883 m-2/g. FTIR results illustrated the existence of Si–O–Si and Si–O–Ti bonds in Ti-MCM-41. The appearance of Ti2 p peaks in the XPS results confirmed the FTIR findings that the Ti was successfully doped into the MCM-41 structure. Zeta（ζ）-potential results indicated that the iso-electric point（IEP） of Ti-MCM-41 was at about pH 3.02. In this study, the photocatalytic degradation of oxytetracycline（OTC） at different pH was investigated under Hg lamp irradiation（wavelength 365 nm）. The rate constant（K′obs） for OTC degradation was 0.012 min-1at pH 3. Furthermore, TOC（total organic carbon） and high resolution LC–MS（liquid chromatography–mass spectrometry） analyses were conducted to elucidate the possible intermediate products and degradation pathway for OTC. The TOC removal efficiency of OTC degradation was 87.0%, 74.4% and 50.9% at pH 3, 7 and 10, respectively. LC–MS analysis results showed that the degradation products from OTC resulted from the removal of functional groups from the OTC ring.

Photocatalytic degradation of Rhodamine B by microwave-assisted hydrothermal synthesized N-doped titanate nanotubes

Microwave-induced nitrogen-doped titanate nanotubes（NTNTs） were characterized by transmission electron microscopy（TEM）, X-ray diffraction（XRD）, X-ray photoelectron spectroscopy（XPS）, Fourier transform infrared spectroscopy（FT-IR）, Zeta potential analysis,specific surface area（SBET）, and UV-Visible spectroscopy. TEM results indicate that NTNTs retain a tubular structure with a crystalline multiwall and have a length of several hundred nanometers after nitrogen doping. XRD findings demonstrate that the crystalline structure of NTNTs was dominated by anatase, which is favored for photocatalytic application. The Ti-O-N linkage observed in the XPS N 1s spectrum is mainly responsible for narrowing the band gap and eventually enhancing the visible light photoactivity. FT-IR results demonstrated the existence of H3O＋, which could be excited by photo-generated holes to form hydroxyl radicals and degrade environmental pollutants. After sintering at 350°C, the UV-Vis absorbance edges of NTNTs significantly shift to the visible-light region, which indicates N atom doping into the nanotubes. Photocatalytic degradation of Rhodamine B（RhB） via NTNTs show good efficiency, with pseudo first-order kinetic model rate constants of 3.7 × 10-3, 2.4 × 10-3and 8.0 × 10-4sec-1at pH 3, 7, and 11, respectively.