Yasuhiro Sadanaga

Ultrasound-assisted production of biodiesel fuel from vegetable oils in a small scale circulation process.

Biodiesel production from canola oil with methanol was performed in the presence of a base-catalyst by a circulation process at room temperature. In this process, the transesterification was accelerated by ultrasonic irradiation of low frequency (20 kHz) with an input capacity of 1 kW. The influences of various parameters on the transesterification reaction, including the amount of catalyst, the molar ratio of methanol to oil and the reaction time, were investigated. The objective of this work was to produce biodiesel satisfying the biodiesel-fuel standards of low energy consumption and material savings. The optimal conditions were: methanol/oil molar ratio of 5:1 and 0.7 wt.% catalyst in oil. Under these conditions, the conversion of triglycerides to fatty acid methyl esters was greater than 99% within the reaction time of 50 min. Crude biodiesel was purified by washing with tap water and drying at 70 degrees C under reduced pressure.

A two-step continuous ultrasound assisted production of biodiesel fuel from waste cooking oils: A practical and economical approach to produce high quality biodiesel fuel

A transesterification reaction of waste cooking oils (WCO) with methanol in the presence of a potassium hydroxide catalyst was performed in a continuous ultrasonic reactor of low-frequency 20 kHz with input capacity of 1 kW, in a two-step process. For the first step, the transesterification was carried out with the molar ratio of methanol to WCO of 2.5:1, and the amount of catalyst 0.7 wt.%. The yield of fatty acid methyl esters (FAME) was about 81%. A yield of FAME of around 99% was attained in the second step with the molar ratio of methanol to initial WCO of 1.5:1, and the amount of catalyst 0.3 wt.%. The FAME yield was extremely high even at the short residence time of the reactants in the ultrasonic reactor (less than 1 min for the two steps) at ambient temperature, and the total amount of time required to produce biodiesel was 15h. The quality of the final biodiesel product meets the standards JIS K2390 and EN 14214 for biodiesel fuel.

Development of a measurement system of OH reactivity in the atmosphere by using a laser-induced pump and probe technique

A novel instrument for measuring OH reactivity in the troposphere has been developed by using a laser-induced pump and probe technique. Air was introduced into a flow tube and OH was produced artificially using O3 photolysis by 266 nm laser. The OH decay rate in the flow tube was monitored by the time-resolved laser-induced fluorescence technique. In this article, the instrument, that is, the measurement principle, the flow tube and the fluorescence detection cell, is presented in detail. Interference by absorption of the 266 nm laser light by O3, and photolysis of NO2 and HCHO was found to be negligible. The influence of recycled OH from the HO2+NO reaction on the measured OH reactivity was estimated by a box model calculation. The systematic error of the measured decay rate was found to be less than 5% even in high NO condition ([NO]=20 ppbv). The dependence of the measured decay rate on the flow rate in the reaction tube was investigated. A slight change in the total flow rate does not influence the me...

Development of a ground-based LIF instrument for measuring HOx radicals : Instrumentation and calibrations

An instrument for measuringtropospheric OH/HO2 radicals by laser-inducedfluorescence developed in our laboratory is presentedin detail. It is based on FAGE (fluorescence assay bygas expansion) technique and OH is both excited anddetected at 308 nm corresponding to its A-X(0,0) band.The alignment of the laser beam, the design of thesample gas inlet, and the devices for the fluorescencedetection are optimized so as to reduce the backgroundsignal while keeping the OH sensitivity as high aspossible. A thermalized position of the expanding gasbeam is probed in our system and we did not observe asevere decrease of the HOx sensitivities under humidconditions. An optical fiber is used for deliveringthe laser light to the fluorescence detection cellmounted outside at a high position. Thus the laserbeam alignment is by far simplified and is made highlyreproducible, once settled properly. For thecalibration, two methods are employed: a system withlaser absorption measurements of OH and a system ofsimultaneous photolysis of H2O and O2. Thecalibration factors are compared well within thecombined uncertainty. Using the latter system, theconversion efficiency of HO2 to OH by NO additionis measured to be around 90%. The detection limitsfor OH and HO2 (S/N = 2) are estimated to be3.3 × 106 and 3.6 × 106cm−3 at noon,respectively, with an integration time of 1 min. Theresults of test observations at our institute are alsopresented.

Daytime HO2 concentrations at Oki Island, Japan, in summer 1998: Comparison between measurement and theory

The daytime variation of hydroperoxy (HO 2 ) radical concentration was observed by an instrument based on laser-induced fluorescence with NO addition at Oki Island, Japan, in July/August 1998. Although OH was not detected due to the high detection limit of the instrument, HO 2 was determined with the detection limit of 0.8 parts per trillion by volume (pptv) (S/N=2, integration time of 1 min). On average, HO 2 showed a maximum concentration of around 9 pptv in the early afternoon hours. During the field campaign, chemical species and meteorological parameters such as O 3 , CO, nonmethane hydrocarbons(C 2 -C 6 ), NO/NO 2 , HCHO/CH 3 CHO, SO 2 , HNO 3 and J(NO 2 ) were also observed. Unfortunately, the absolute value of J(O 1 D) was not measured. Model calculations for radical concentrations were performed and they were compared to the observed hourly HO 2 concentrations. On August 9 the calculated HO 2 matched the observation very well within the uncertainties of observations (±26%, 1σ) and the model (±24%, 1σ). This indicates a good performance of model calculations in estimating HO 2 under certain conditions with plenty of isoprene. On other days, however, model usually overestimated HO 2 by a factor of 2, especially in the hours around noon. It is deduced that some important HO, loss chemistry is missing in the model. Although the cause of the discrepancy is not fully understood, possible mechanisms to explain the overestimation are studied. A hypothesis with additional loss of HO 2 would be more plausible than that with additional OH loss. The additional loss rate for HO 2 that can reduce the calculated HO 2 to the measured level was computed for each hour. Its variation correlated well with those of H 2 O and some photochemical products. The possibilities of HO 2 loss on aerosol surface, unknown acceleration of HO 2 reactions in the presence of high HO 2 and HO 2 reactions with carbonyl species are discussed.

Nighttime observation of the HO2 radical by an LIF instrument at Oki Island, Japan, and its possible origins

HO2 (hydroperoxy) radical of unexpectedly high concentration around 3 ppt was measured by an instrument based on laser-induced fluorescence with NO addition at Oki Island, Japan, on the night of August 9/10, 1998. We confirmed that the interference by atmospheric organic peroxy (RO2) radicals was insignificant and concluded that the measured signal originated from nighttime HO2. Model calculations constrained to ancillary measurements indicated that HO2 and RO2 were produced primarily via the reactions of ozone with olefins, especially those with internal olefins, and that NO3 chemistry was relatively unimportant. HO2 concentration was kept high by nighttime NO (∼10 ppt) via RO2 + NO reactions. Low NO2 (∼150 ppt) slowed NO3 production rate. Thus, the high observed HO2 suggests that the reactions of O3 with olefins are important HOx primary production mechanisms in the relatively clean atmosphere.

Photochemical reactions in the urban air : Recent understandings of radical chemistry

Abstract In this review article, recent understandings of the urban atmosphere are briefly presented, focusing on NOx (NO and NO2), NO3 and HOx (OH and HO2), which are the key species for photochemical ozone production in the urban air. For NOx chemistry, relationship between NOx and HOx, and photostationary state (PSS) of the conversion between NO and NO2 are introduced with examples of recent research. Chemistry of nitrate radicals in the nighttime is also introduced. In addition, recent and representative techniques for the measurements of reactive nitrogen species in the troposphere are presented. As for HOx radicals, important formation and loss processes and measurement methods developed recently are introduced. Recent campaign-based observations of HOx radicals in the troposphere are also presented.

Behavior of OH and HO2 radicals during the Observations at a Remote Island of Okinawa (ORION99) field campaign: 1. Observation using a laser-induced fluorescence instrument

The hydroxyl (OH) and hydroperoxyl (HO2) radicals were measured by a laser-induced fluorescence instrument at Cape Hedo, Okinawa Island, Japan, in summer 1999 during the Observations at a Remote Island of Okinawa (ORION99) field campaign. The field deployment of the instrument and its calibrations are described in detail. From the frequent calibrations during the field campaign, it was shown that the instrument, utilizing an optical fiber to transmit the laser light to the detection cell located on a tower, had a sufficiently stable sensitivity to OH and HO2 in order to trace their diurnal and day-to-day variations. The detection limit of the instrument was typically around 4 × 106 radicals cm−3 with an integration time of 1 min. We could not examine fast OH variations. However, hourly averaged OH concentrations during daytime were statistically significant. The HO2 concentrations were higher and the detailed variations were detected. On average, OH and HO2 showed daytime maxima of around 4 × 106 radicals cm−3 and of around 17 pptv, respectively. The median, tenth, and ninetieth percentiles of the measured daytime HO2/OH concentration ratio were 76, 32, and 143, respectively. The power law dependence of HO2 on J(O1D) was about 0.5 when the NO concentration was lower than 300 pptv and was about 1 when the NO concentration was higher than 1 ppbv, which was consistent with the known radical chemistry in the lower troposphere.

Numerical study of the atmospheric input of anthropogenic total nitrate to the marginal seas in the western North Pacific region

[1] Atmospheric input of anthropogenic total nitrate to marginal seas in the western North Pacific region was simulated using a regional chemical transport model over East Asia based on year-to-year emission estimates during 1980-2003. Seasonal cycles and concentration levels of gas and aerosol were examined using observation data from various studies. The model simulated total nitrate deposition over the East China Sea (ECS) as 140 GgN/yr, which is the same order of the annual river discharge from the Yangtze River. The ratio of dry and wet deposition over ECS was obtained as approximately 6: 4. Total nitrate deposition over ECS corresponds to 3.2% (N base) of total NO x emission in China. The total deposition at present is three times larger than that of 1980, corresponding with increased NO x emissions.

Transport and transformation of total reactive nitrogen over the East China Sea

[1] Ground-based measurement of total reactive nitrogen (NOy), NO y(g) (gas phase NO x + HNO 3 ), and particulate NO 3 - was carried out at the Cape Hedo Atmosphere and Aerosol Monitoring Station (CHAAMS) in Okinawa, Japan, from spring to winter in 2006. The concentrations of NO y NO y(g) , and particulate NO 3 were simultaneously high in spring but low in summer. This difference was mainly caused by air mass history, which was strongly associated with the typical weather pattern observed in the east Asian region for each season. The chemical transformation process of particulate NO 3 - during transport was examined using the data measured at Qingdao, China, in spring 2006. As the transport time of air masses increased, particulate NO 3 - continuously shifted from fine mode to coarse mode. It was found that the chemical transformation of particulate NO 3 - was mainly associated with the transport time of air masses, the geographical position of CHAAMS, and the transition from NH 4 NO 3 to gas phase HNO 3 . In air masses from Qingdao, China, the ratio of NOy concentration observed at CHAAMS to that at Qingdao was about 0.1, which was lower than that of SO y (SO 2 + nss-SO 2- 4 ). Sulfate was found in fine particles at CHAAMS in contrast to particulate NO 3 - . As the lifetimes of NOy and SO y depend on the particle size, the difference in chemical transformation process during transport largely influences the abundance of transported NO y The variations of NO y(g) and particulate NO 3 - were analyzed when dust plumes reached CHAAMS. The presence of dust causes the formation of particulate NO 3 - in coarse mode from NO y(g) and an increase of its fraction in NO y The effect of volcanic activity on particulate NO 3 - concentration was also analyzed. It is suggested that particulate NO 3 - escaped to gas phase HNO 3 through the uptake of abundant volcanic H 2 SO 4 by aerosols.