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Microfluidic devices have become a powerful tool for chemical and biologic applications. To control different functional parts on the microchip, valve plays a key role in the device. In conventional methods, physio-mechanical valves are usually used on microfluidic chip. Herein, we reported a chemo-mechanical switchable valve on microfluidic chip by using a thermally responsive block copolymer. The wettability changes of capillary with copolymer modification on inner surface were investigated to verify the function as a valve. Capillaries with modification of poly-(N-isopropylacrylamide-co-hexafluoroisopropyl acrylate) (P(NIPAAm-co-HFIPA)) with a 20% HFIPA was demonstrated capable of control aqueous solution stop or go through. Then short capillaries with copolymer modification were integrated in microchannels as valves. With the temperature changing around lower critical solution temperature (LCST), the integrated chemo-mechanical switchable valve exhibited excellent “OPEN–CLOSE’’ behavior for microflow control. After optimization of the block copolymer sequences and molar ratio, a switching time as low as 20 s was achieved. The developed micro valve was demonstrated effective for flow control on microchip.

In Japan, concentrations of precursors of photochemical oxidants such as nitrogen oxides (NOx) and non-methane hydrocarbons (NMHCs) are decreasing year by year, but an improvement regarding photochemical oxidants is recently stagnant. To elucidate the reason, we have planned seasonal intensive observations in Tokyo, in which comprehensive measurements of speciated reactive nitrogen NOy and non-methane volatile organic compounds are performed. In summer of 2022, the observation was carried out at a campus of Tokyo Metropolitan University, a suburban area of Tokyo. In the intensive observation, NO, NO2, ΣPANs, ΣONs, HONO, HNO3, H2O2, SO2, O3, NH3, 28 NMHCs, and 10 oxygenated volatile organic compounds (OVOCs) were measured simultaneously. The ΣPANs and ΣONs were measured by thermal dissociation-cavity attenuated phase shift (CAPS) spectroscopy. The HONO, HNO3, and H2O2 were measured by negative ion chemical ionization mass spectrometry using I−·(H2O)n as the reagent ion. The NMHCs, OVOCs and NH3 were measured by selected ion flow tube mass spectrometry and the data of NMHCs were compared and corrected with the data from gas chromatography/flame ionization detector (GC/FID). The ozone formation in Tokyo will be discussed.

Metabolism of a single cell, even within the same organization, differs from other cells by orders of magnitude. Single-cell analysis provides key information for early diagnosis of cancer as well as drug screening. Any slight change in the microenvironment may affect the state of a single cell. Timely and effective cell monitoring is conducive to better understand the behavior of single cells. The immediate response of a single cell described in this study is a liquid transfer-based approach for real-time electrochemical detection. The cell was in situ stimulated by continuous flow with glucose, and lactate secreted from the cell would diffuse into the microflow. The microflow was aspirated into the detection channel where lactate was then decomposed by coupled enzyme reactions and detected by an electrode. This work provides a novel approach for detecting lactate response from a single cell by noninvasive measurements, and the position resolution of the microfluidic probe reaches the level of a single cell and permits individual heterogeneity in cells to be explored in the diagnosis and treatment of cancer as well as in many other situations.

Gold nanowires are expected to be applied to biosensing due to their advantages, such as high stability and biocompatibility. However, it is still inconvenient to fabricate a single gold nanowire at a precise position, and without a special demanding environment. In this study, we present an open-space laminar flow approach for fabricating a single gold nanowire at a precise position under normal conditions. The fabricated gold nanowire demonstrated excellent biosensing of IgA with an extremely low limit of detection (1 aM).

Affordable methods for ultra-sensitive biomarkers detection may improve the standard of living in resource-constrained countries. Nanowire biosensor is preponderant in ultra-sensitive protein detection. However, current strategies for nanowire sensor (NWS) fabrication often require sophisticated instruments, being inaccessible in less-resourced laboratories. Herein, we circumvent this challenge by developing a simple methodology, localized hydrodynamic flow confinement assisted nanowire sensor fabrication, enable the detection with limits of detection (LOD) for IgA and IgG measurement were 0.089 fg/mL and 0.93 fg/mL, respectively, demonstrating a 10-fold increase in detection sensitivity compared with the published NWS. Noteworthy, an X-Y positioner combined with a homemade microchemical pen (MCP) for tunable chemical deposition were sufficient to complete the fabrication of the nanowire biosensor without other expensive and demanding equipment. Overall, a particularly accessible, competitive, and low-cost approach of nanowire sensor fabrication for ultra-sensitive protein detection was developed, which could widely facilitate the application of nanowire biosensors. Besides, the nanowire sensor can also be employed to detect other analytes of interest by the use of different stimuli-responsive biosystems.

Sea-salt particles are major aerosol constituents in the marine boundary layer (MBL) and are chemically modified by acidic substances from anthropogenic, volcanic, and biogenic sources. When these acidic substances react with sea-salt particles, they can be easily scavenged from the MBL. This scavenging process influences the concentration of cloud condensation nuclei in the MBL. In this study, differences in chemical compositions of sea-salt particles collected over the Pacific Ocean and its marginal seas were investigated based on an individual particle analysis. The sources of the acidic substances that modified sea-salt particles were also estimated. Approximately 70% of the analyzed particles were fresh sea-salt particles. However, a sample collected near Guam was dominated by sulfates and was affected by polluted air masses that originated over the Asian continent. The aerosols collected around the Aleutian Islands included a large number of sulfates and modified sea-salt particles. Individual particle composition analyses indicate that these sea-salt particles were modified by methanesulfonic acid produced from marine biota and sulfuric acid from volcanic gas from the Kamchatka Peninsula. The gravitational deposition velocities of sulfates and modified sea-salt particles were calculated based on measured particle sizes. The results suggested that if acidic substances react with sea-salt particles, their lifetime in the atmosphere could be shortened due to dry deposition. Therefore, it is necessary to consider the scavenging effect of sea-salt particles for estimating the climate cooling effect by clouds over the ocean.

Lightning is an important source of nitrogen oxides (LNOx). The actual global production of LNOx is still largely uncertain. One of the reasons for this uncertainty is the limited available observation data. We measured the concentrations of total reactive nitrogen (NOy), nitric oxide (NO) and nitrogen dioxides (NO2) and then obtained NOx oxidation products (NOz: NOz = NOy - NOx) at a station at the top of Mount Fuji (3776 m a.s.l.) during the summer of 2017. Increases in NOy and NO2 were observed on 22 August 2017. These peaks were unaccompanied by increases in CO, which suggested that the observed air mass did not contain emissions from combustion. The backward trajectories of the above air mass indicated that it moved across areas where lightning occurred. The NOy concentration was also calculated by using a chemical transport model, which did not take NOx produced by lightning into account. Therefore, the NOy concentration due to lightning can be inferred by subtracting the calculated NOy from the observed NOy concentrations. The concentration of NOy at 13:00 on 22 August 2017 originating from lightning was estimated to be 1.11 ± 0.02 ppbv, which comprised 97 ± 2% of the total NOy concentration. The fractions of NO2 and NOz in the total NOy were 0.54 ± 0.01 and 0.46 ± 0.03, respectively. The NO concentration was below the detection limit. We firstly observed increase of concentrations of NOy originating from lightning by ground-based observation and demonstrated the quantitative estimates of LNOx using model-based calculation.

application/pdf, Article, Atmospheric Environment. 196, p.20-26

A controlled drug delivery system (DDS) was designed by integrating the thermoresponsive copolymer poly(N-isopropylacrylamide-co-methacrylic acid) (poly(NIPAAm-co-MAA)) with core–shell 1,6-hexanediol diacrylate (HDDA) microparticles. The monodisperse HDDA particles with a hollow core and a nanoporous shell were fabricated in a continuous manner by an initially proposed inkjet printing process combined with UV polymerization. The thermoresponsive poly(NIPAAm-co-MAA) copolymer was grafted onto the surface of HDDA microcapsules by free radical initiated polymerization. Particularly, the lower critical solution temperature (LCST) of the copolymer was adjusted to human physiological temperature by the optimal comonomer ratio of MAA. With temperature changes at around the LCST, the copolymer, which was modified on the internal nanopore, served as a “retractable gate” by virtue of its changes in conformation between swollen and collapsed structures. Thus, controlled drug release was achieved by the reversible “open–close” transition characteristics of the nanopores. Fluorescein as a hypothetical drug molecule was loaded in the microcapsules and used to investigate the controlled release of the material. The results confirmed that this system represents a promising candidate for use in preparing controlled DDSs.

The abundance of humic-like substances in the atmosphere has received considerable attention since these substances play an important role in various atmospheric processes. The wide variety of quantitative techniques used to study humic-like substances produce dissimilar results, making data comparison difficult. Also, global background concentrations and the transfer of atmospheric humic-like substances are poorly known. Here, we compared resins to extract humic-like substances in aerosols, and we measured contents in aerosols from Mt. Fuji. Results show that diethylaminoethyl cellulose resins extracted more humic-like substances than the diethylaminoethyl resin (hydroxylated methacrylic polymer). The mean humic-like substances concentrations in the free troposphere in East Asia is similar to that in Europe, suggesting that the global background level of humic-like substances is 0.05 μg C m−3, based on the humic-like substances concentrations on Mt. Fuji and Mt. Sonnblick. Humic-like substances concentrations, especially fulvic acids concentration, at the summit of Mt. Fuji increased when air masses came from the continent along with the carbon monoxide and ozone.

This work presents diurnal variations of gas- and particle-phase dicarbonyls (glyoxal (Gly) and methylglyoxal (Mgly)) in the atmosphere, which are important compounds that contribute to the formation and growth of atmospheric particulate matter. To obtain variations in partitioning, continuous collection of gaseous dicarbonyls was performed using a parallel plate wet denuder, and at the same time, the dicarbonyls in particle were collected using a spray-type particle collector downstream. Hourly samples were analyzed by high performance liquid chromatography–electrospray ionization–tandem mass spectrometry. This method is advantageous to monitor the gaseous and particulate carbonyls separately without loss during sampling. Sampling was performed in summer and winter in a midsize city (Kumamoto, Japan). The concentrations of the dicarbonyls increased in the summer daytime, which suggests that they are mostly formed by secondary production in the local atmosphere. The dicarbonyls and formaldehyde (HCHO) wer...

Total OH reactivity, which gives the instantaneous loss rate of OH radicals due to reactive species, is an invaluable technique to understand regional air quality, as it gives the overall reactivity of the air mass, the fraction of each trace species reactive to OH, the fraction of missing sinks, O3 formation potential, etc. Total OH reactivity measurement was conducted in a small suburban forest located ∼30 km from Tokyo during the air quality study at field museum TAMA (AQUAS-TAMA) campaign in early autumn 2012 and summer 2013. The average measured OH reactivities during that autumn and summer were 7.4 s−1 and 11.4 s−1, respectively. In summer, isoprene was the major contributor, accounting for 28.2% of the OH reactivity, as a result of enhanced light-dependent biogenic emission, whereas NO2 was major contributor in autumn, accounting for 19.6%, due to the diminished contribution from isoprene as a result of lower solar strength. Higher missing OH reactivity 34% was determined in summer, and linear regression analysis showed that oxygenated VOCs could be the potential candidates for missing OH reactivity. Lower missing OH reactivity 25% was determined in autumn and it was significantly reduced (11%) if the interference of peroxy radicals to the measured OH reactivity were considered.

Manipulation of light transmission/absorbance and reflection/emission has a great significance in smart windows and displaying media like liquid crystal. Here, we report the usage of an external electric field to reversibly switch the molecular spectra of a model molecule on the basis of its interaction with an electroresponsible polymer brush. Both the UV-vis absorbance spectrum and the fluorescence emission spectrum of the model molecule were confirmed to be electroswitchable. The electroswitchable spectra were experimentally demonstrated to be induced by the electroswitchable statuses of medium anionic poly-allyloxy hydroxypropyl sulfonate (poly-AHPS) brush. Insightfully, the molecular aggregated status of model proflavine molecules could be electrically controlled via the electroresponsible poly-AHPS brushes and then the molecular spectra of the model proflavine molecule also could be electrically and controllably shifted. The success in the manipulation of molecular spectra opens up a wide range of applications not only for displaying but also for nonlinear optics, in vivo imaging, sensors, and environmental inspection.

Field measurements performed in the Keihin coastal industrial area during summer 2019 were used to characterize the air quality and ozone production potential. The total hydroxyl radical (OH) reactivity was found to be moderate, peaking with a 2-h average of 29.0 s−1, corresponding to an OH lifetime of ∼34 ms. The average hourly total OH reactivity was 11.4 ± 5.2 s−1 (average ± standard deviation), and the measured OH sinks (from over 90 trace species) accounted for 92.3% of the total OH reactivity. Compared with a previous series of campaigns in urban/suburban Japan, this field work investigated an area often overlooked for atmospheric observations and found the smallest missing OH reactivity (on average, 0.88 s−1). The near-zero missing OH reactivity indicated that photochemical procedures were less important to the Yokohama air quality study (AQUAS–Yokohama) than the ubiquitous substantial secondary products in other areas. This study also demonstrated that oceanic air masses may quickly flush coastal industrial areas and that a limited activity of photochemistry due to elevated NOx effectively terminates OH radical recycling. A comparison with other campaigns in Japan exhibited a positive correlation with oxidants (ozone and formaldehyde), indicating secondary products have a critical role in explaining missing OH reactivity. The ozone production potential was corresponding to a volatile organic compound (VOC)-limited regime, while the missing OH reactivity led to an ∼8% increase in ozone formation. Finally, a positive correlation was found between the ozone production rate and the reactivity ratio between VOCs and NOx, in both the current study and various other field campaigns in urban areas.

As a new approach to investigating formation processes of secondary organic aerosol (SOA) in the atmosphere, ozone-induced potential aerosol formation was measured in summer at a suburban forest site surrounded by deciduous trees, near Tokyo, Japan. After passage through a reactor containing high concentrations of ozone, increases in total particle volume (average of 1.4 × 109 nm3/cm3, which corresponds to 17% that of pre-existing particles) were observed, especially during daytime. The observed aerosol formations were compared with the results of box model simulations using simultaneously measured concentrations of gaseous and particulate species. According to the model, the relative contributions of isoprene, monoterpene, and aromatic hydrocarbon oxidation to SOA formation in the reactor were 24, 21, and 55%, respectively. However, the model could explain, on average, only ∼40% of the observed particle formation, and large discrepancies between the observations and model were found, especially around noon and in the afternoon when the concentrations of isoprene and oxygenated volatile organic compounds were high. The results suggest a significant contribution of missing (unaccounted-for) SOA formation processes from identified and/or unidentified volatile organic compounds, especially those emitted during daytime. Further efforts should be made to explore and parameterize this missing SOA formation to assist in the improvement of atmospheric chemistry and climate models.

The change in the ozone production rate on reducing its precursors, namely, ozone production sensitivity, is important information for developing a strategy to reduce ozone. We expanded a conventional sensitivity analysis theory by including peroxy radical loss by uptake onto particle surfaces in the aim of examining their potential impact. We also propose a new concept of absolute sensitivity that enables us to evaluate the quantitative effectiveness of precursor reduction toward mitigating ozone production over a given period and area. This study applies the theory to observations in Tsukuba, a city in Japan. The relative sensitivity analysis shows that ozone production was more sensitive to volatile organic compounds (VOCs) in the morning and evening, and it became more sensitive to NOx in the afternoon. NO depletion was a main trigger in this sensitivity regime transition. The absolute sensitivity analysis indicates that the VOC-sensitive period in the morning determines the total ozone production sensitivity in a day. While particles did not have significant impact on regime classification in Tsukuba, they have a potential to decrease the mitigating effect of VOC reduction on ozone production and to moderate the enhancement effect of NOx reduction depending upon uptake coefficients. A further study will benefit from a combination with an observation-constrained box model simulation or chemical transport modeling system, which may provide sensitivity analysis over a large spatial and temporal range.

We investigated the degradation of polycyclic aromatic hydrocarbons (PAHs) during long-range transport. Aerosols were collected simultaneously at remote sites on Tuoji Island, China; Fukue Island, Japan; and the Cape Hedo Atmosphere and Aerosol Measurement Station (CHAAMS), Okinawa, Japan in April, October, and December from 2012 to 2013. These remote sites were convenient for investigating the degradation of PAHs during long-range transport. PAHs were analyzed via gas chromatography/mass spectrometry. We identified air masses that passed over all sites and combined our measurements with a chemical transport model. We estimated the relative contributions of the PAHs at the three sites by normalizing the PAH concentrations to elemental carbon. Benzo[a]pyrene persisted in 5-16% of samples. The results of this study are consistent with laboratory studies in which secondary organic aerosol (SOA) coatings protected PAHs from degradation by ozone. We detected an inhibition of the degradation PAHs by SOA coatings by collecting PAHs simultaneously at the three sites. To elucidate the major sources of the SOAs, we carried out a positive matrix factorization analysis to identify the major sources of SOA coating, which controls the lifetime of PAHs. In spring and winter, the contribution of vehicle emissions was higher (46%) at Tuoji Island than at CHAAMS (13%). In contrast, the contribution of coal combustion was higher at CHAAMS (59%) than at Tuoji Island (28%). This result implies that during long-range transport, PAHs derived from coal combustion are more slowly degraded than PAHs derived from vehicle emissions. We found that the viscosity of SOA coatings derived from vehicle emissions in China was low, and the corresponding PAHs were rapidly degraded. In contrast, the viscosity of SOA coatings derived from coal combustion was high, and degradation of the corresponding PAHs was relatively slow. These results imply that PAHs derived from coal combustion have long lifetime.

The concentrations of atmospheric gaseous elemental mercury (GEM), gaseous oxidized mercury (GOM), and particle-bound mercury (particles with diameter smaller than 2.5 &mu, m, PBM2.5) were continuously observed for a period of over 10 years at Cape Hedo, located on the north edge of Okinawa Island on the border of the East China Sea and the Pacific Ocean. Regional or global scale mercury (Hg) pollution affects their concentrations because no local stationary emission sources of Hg exist near the observation site. Their concentrations were lower than those at urban and suburban cities, as well as remote sites in East Asia, but were slightly higher than the background concentrations in the Northern Hemisphere. The GEM concentrations exhibited no diurnal variations and only weak seasonal variations, whereby concentrations were lower in the summer (June&ndash, August). An annual decreasing trend for GEM concentrations was observed between 2008 and 2018 at a rate of &minus, 0.0382 &plusmn, 0.0065 ng m&minus, 3 year&minus, 1 (&minus, 2.1% &plusmn, 0.36% year&minus, 1) that was the same as those in Europe and North America. Seasonal trend analysis based on daily median data at Cape Hedo showed significantly decreasing trends for all months. However, weaker decreasing trends were observed during the cold season from January to May, when air masses are easily transported from the Asian continent by westerlies and northwestern monsoons. Some GEM, GOM, and PBM2.5 pollution events were observed more frequently during the cold season. Back trajectory analysis showed that almost all these events occurred due to the substances transported from the Asian continent. These facts suggested that the decreasing trend observed at Cape Hedo was influenced by the global decreasing GEM trend, but the rates during the cold season were restrained by regional Asian outflows. On the other hand, GOM concentrations were moderately controlled by photochemical production in summer. Moreover, both GOM and PBM2.5 concentrations largely varied during the cold season due to the influence of regional transport rather than the trend of atmospheric Hg on a global scale.

This study conducted mercury (Hg) isotopic analysis, which has been expected as a new indicator for understanding the behavior of atmospheric Hg. The dominant atmospheric Hg species, namely gaseous elemental mercury (GEM, Hg0), were collected at the Cape Hedo Atmosphere and Aerosol Monitoring Station (CHAAMS) in Okinawa, Japan, for evaluating possible source(s) and transformation process(es) of Hg. The Hg isotopic compositions of GEM samples showed that the mass-dependent fractionation (MDF) of δ202Hg and the mass-independent fractionation (MIF) of Δ199Hg ranged from −2.15‰ to 0.79‰ and from −0.32‰ to 0.00‰, respectively. The results were classified into two groups: (1) negative δ202Hg and near-zero Δ199Hg in summer and (2) near-zero δ202Hg and negative Δ199Hg in the other season. According to the NOAA Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model, the dominant air masses traveled from East Asia during winter and South and East Asia during summer. However, the air masses also traveled from mainland Japan and rotated around Okinawa before reaching CHAAMS. In contrast, clear positive correlations between δ202Hg values and CO and PM2.5 concentrations were observed during summer. A small peak of Ox concentration was observed at three atmospheric monitoring stations, namely Nago, Naha, and Miyako Island during summer. Since Miyako Island is located ∼370 km southwest of CHAAMS, the main emission source of GEM transported to CHAAMS was not from mainland Okinawa but traveled from the southwest during summer.

Air samples were collected at Mt. Fuji Research Station (FRS) for the measurements of volatile organic compounds (VOCs) in the summers of 2015 and 2016. In this study, 24 compounds were analyzed, of which only 12 halocarbons were quantified in 2015. The average total concentrations of target VOCs were 2.62 ± 1.38 and 2.99 ± 0.95 ppb in 2015 and 2016, respectively. The concentrations of individual VOCs ranged from a few ppt to a few ppb, indicating a highly inhomogeneous feature at the FRS. A cluster analysis of 3-day backward trajectories was performed for the sampling time. Except for the aromatic compounds, the VOCs showed relatively low concentrations in association with air masses originating from the coastal region in the low latitudes (15°N–35°N) of East Asia in 2015. By contrast, the clusters with elevated VOC concentrations mainly came from the high latitudes (35°N–60°N) of the Asian continent in 2016. No particular diurnal pattern was found for VOCs and CO, which might have resulted from suppressed mountain-valley winds at the FRS. Halocarbons regulated by the Montreal Protocol showed low variability and were in favorable agreement with background values at the Gosan station (GSN) and those reported in the literature. Other partially halogenated compounds with higher variability, such as CH3Cl and CHCl3, showed discrepancies at the FRS and GSN. 1,2-dichloroethane (R-150), 1,1-dichloroethane (R-150a), and 1,4-dichlorobenzene (p-DCB) were also measured at the FRS with concentrations of 24 ± 14, 38 ± 13, and 13 ± 10 ppt, respectively, in 2015. A close relationship between n-pentane and i-pentane with R2 more than 0.85 was found in both 2015 and 2016. Low ratios of n/i-pentane ranging from 0.25 to 0.67 were observed in the free troposphere at the FRS, comparable to most mountain stations.

The paper describes a new online quantitative electrophoretically mediated microanalysis (EMMA) for use in immunoassays based on the unique drop-by-drop introduction of a sample by means of an inkjet for capillary electrophoresis (CE). Plugs of a fluorescein-labeled antibody (Anti-humanIgG-DyL550) and human IgG were alternately injected into a capillary using the inkjet, followed by the merging of the plugs and the subsequent immune reaction. The antigen-antibody complex that was formed in the merged zone was then separated by CE. As a proof-of-concept, the method was used to determine human IgG. As a result, both the consumption of the reaction solution and the analysis time were significantly reduced. The method showed a wide linear range (10–2000 ng mL−1, R2 = 0.9912) of calibration and the detection limit (5 ng mL−1) was substantially lower than that by for conventional methods.

We have performed long-term measurements of organic carbon (OC) and elemental carbon (EC) in atmospheric aerosols at Cape Hedo Atmosphere and Aerosol Monitoring Station (CHAAMS). Large-scale East Asian continental outflows of aerosols have frequently been observed at CHAAMS in both winter and spring, but large-scale air pollution (LSP) events in winter have not yet been described in the literature. Examination of PM 2.5 in LSP events showed that it consisted mainly of carbonaceous aerosols and sulfate. We compared OC and EC concentrations measured at CHAAMS during LSP events with those measured at the same time in East Asian cities, and with concentrations measured at CHAAMS during an Asian dust event in spring 2006. The maximum OC and EC concentrations at Cape Hedo during LSP events were comparable to those at China Atmosphere Watch Network sites in China. The average OC concentration was also similar to concentrations measured at urban sites in Taipei (Taiwan), Seoul (Korea), and Tokyo (Japan); EC, however, was several times lower at Cape Hedo than EC concentrations at these urban sites. We identified three types of air masses associated with LSP events: Type 1, a polluted air mass composed of freshly emitted pollutants; Type 2, an air mass that underwent photochemical aging during transport from China to Okinawa; and Type 3, an air mass that was almost fully aged in China before being transported to Japan. Simulations of LSP events with a 3-D chemical transport model (Chemical Weather Forecasting System) indicated that Type 1 air masses were associated with “cone type” transport in a low-pressure system, and Type 2 air masses were associated with “giant puff type” transport by a migratory high-pressure system. Generally speaking, air pollutants are transported from China to CHAAMS in winter in association with the north or northwest monsoon. High levels of air pollutants in China in winter are due to higher emissions and poorer dispersion because of the low boundary layer height and low wind speeds. Our results suggest that LSP events occur when a cold front forms under accumulated air pollutants. The mass contribution of carbonaceous materials to PM 2.5 during the LSP event in winter 2008 was 36%, much larger than the contribution of 19% during the spring 2006 dust event.

A fluorescence enhanced phenomenon was found within a micrometer-sized liquid droplet, and it was adopted to construct droplet enhanced fluorescence (DEF) for ultrasensitive fluorescence detection. In this paper, an inkjet was utilized to eject perfect spherical droplets to construct a microspherical resonator and to develop a DEF system. It was utilized to implement ultrasensitive fluorescence detection in a liquid specimen with a volume of several microliters. The DEF detection of fluorescent molecules, fluorescein sodium, was used as a model to validate the proposed enhanced fluorescence detection method. A low limit of detection (LOD) for fluorescein sodium of 124 pM was obtained. The sensitive detection of single stranded DNA (ssDNA) was experimentally completed, with a wide range of linearity with a LOD of 312 pM. The proposed mechanism can be used as an ultrasensitive detection technique for analyzing microliters of liquid samples.

A quantitative sample introduction method based upon inkjet injection was applied to capillary electrophoresis coupled with stacking and sweeping on-line concentration techniques. Methylxanthines were used as model compounds for the proof-of-concept of the method. The volume of injected sample could be easily manipulated by controlling the number of ejected droplets in the injection procedure. Under optimized conditions, a linear relationship between the ejected droplet number and peak area was obtained when the droplet number introduced into the capillary was less than 100. Under optimized quantitative on-line concentration conditions, the limits of detection for theobromine, caffeine, and theophylline were 1.0, 2.0, and 1.0 μM, respectively. The inkjet injection system was evaluated by comparing it with conventional injection methods. The electropherogram of the inkjet injection mode was the same as that for hydrodynamic injection mode, and no sample discrimination was observed compared with the electrokinetic injection mode. The established method was applied to the determination of methylxanthines in bottled green tea. The recoveries of theobromine, caffeine, and theophylline were 94.1, 110.6, and 86.8%, respectively. We conclude that proposed method can be used for quantitative concentration for capillary electrophoresis, thus resulting in an improved accuracy.

There has been only limited information about the vertical chemical structure of the atmosphere, so far. We conducted aerial observations on 11, 12, and 14 December 2010 over the northern part of the East China Sea to analyze the spatial distribution of atmospheric pollutants from East Asia and to elucidate transformation processes of air pollutants during the long-range transport. On 11 December, a day on which Asian dust created hazy conditions, the average PM10 concentration was 40.69 μg m−3, and we observed high concentrations of chemical components such as Ca2+, NO3–, SO42−, Al, Ca, Fe, and Zn. The height of the boundary layer was about 1200 m, and most species of pollutants (except for dust particles and SO2) had accumulated within the boundary layer. In contrast, concentrations of pollutants were low in the boundary layer (up to 1000 m) on 12 December because clean Pacific air from the southeast had diluted the haze. However, we observed natural chemical components (Na+, Cl–, Al, Ca, and Fe) at 3000 m, the indication being that dust particles, including halite, were present in the lower free troposphere. On 14 December, peak concentrations of SO2 and black carbon were measured within the boundary layer (up to 700 m) and at 2300 m. The concentrations of anthropogenic chemical components such as NO3–, NH4+, and Zn were highest at 500 m, and concentrations of both anthropogenic and natural chemical components (SO42−, Pb, Ca2+, Ca, Al, and Fe) were highest at 2000 m. Thus, it was clearly indicated that the air above the East China Sea had a well-defined, layered structure below 3000 m.

Aerial observations of atmospheric pollutants were made over the East China Sea to analyze the transport of air pollutants, especially nitrogen oxides, from East Asia. Three flights each were conducted in October 2009 (autumn) and December 2010 (winter). Onboard measurements of gaseous total odd nitrogen species, gaseous nitric acid (HNO3(g)), O3, SO2, CO and black carbon were made and particles were collected on filters for ionic and metal component analyses. The NO3−(p)/T.NO3 (T.NO3 = HNO3(g) + NO3−(p); NO3−(p) indicates particulate nitrate) ratios were less than 0.5 in most cases. Exceptions were 17 October and 11 December, when high concentrations of dust particles (Kosa) were transported. The average T.NO3/NOy (NOy indicates total odd nitrogen species) ratio in winter was 0.59, and that in autumn was 0.71. In addition, positive and negative correlations between NOy − T.NO3 and ozone were observed in autumn and winter, respectively. These results indicate that the main components of NOy − T.NO3 are NOx and its descendant photochemical products, such as peroxyacyl nitrates and alkyl nitrates, in winter and autumn, respectively. Ratios of Na+ to Cl− + NO3− in particles were close to the seawater ratio for observations in both autumn and winter, save for the Kosa events. The main NO3−(p) formation process was the reaction of HNO3(g) with sea salt aerosols during autumn and winter. On the other hand, NO3−(p) was generated by the reaction of HNO3(g) with dust particles and sea salt during the Kosa events. The fraction of NH4NO3 in NO3−(p) was very small.

We conducted continuous measurements of NOy and total nitrate (T.NO3 = HNO3 + NO 3 − ( p ) ) at Fukue Island, Nagasaki, and Cape Hedo, Okinawa, Japan. We compared variations of NOy or T.NO3 concentrations measured at two remote sites when the air masses were originated from the same regions of the Asian Continent. Long-range transport events from the Asian Continent were extracted by CO concentration peaks at Fukue and Hedo and backward trajectory analyses. We compared the transport time difference at two sites from the Asian continent with the ratios of NOy at Hedo to that at Fukue (=R(NOy)) to find the predominant factor in NOy removal. R(NOy) were less than unity and decreased with the transport time difference. The ratios of NOy/CO at Hedo to those at Fukue (R(NOy/CO)) was assumed to be affected by the deposition process. R(NOy/CO) showed negative correlation with transport time difference as the same the case of R(NOy). This indicates that NOy was mainly removed by deposition rather than dilution. Air mass ages were classified by the ratio of T.NO3 to NOy at Fukue: T.NO3/NOy

We report the UV-light-induced formation of water aerosol/droplets in air based on laser-light scattering measurements, differential mobility analyses and cavity ring-down laser spectroscopy (CRDS)...

Biogenic emissions supply the largest fraction of non-methane volatile organic compounds (VOC) from the biosphere to the atmospheric boundary layer, and typically comprise a complex mixture of reactive terpenes. Due to this chemical complexity, achieving comprehensive measurements of biogenic VOC (BVOC) in air within a satisfactory time resolution is analytically challenging. To address this, we have developed a novel, fully automated Fast Gas Chromatography (Fast-GC) based technique to provide higher time resolution monitoring of monoterpenes (and selected other C9-C15 terpenes) during plant emission studies and in ambient air. To our knowledge, this is the first study to apply a Fast-GC based separation technique to achieve quantification of terpenes in ambient air. Three chromatography methods have been developed for atmospheric terpene analysis under different sampling scenarios. Each method facilitates chromatographic separation of selected BVOC within a significantly reduced analysis time compared to conventional GC methods, whilst maintaining the ability to quantify individual monoterpene structural isomers. Using this approach, the C9-C15 BVOC composition of single plant emissions may be characterised within a 14.5 min analysis time. Moreover, in-situ quantification of 12 monoterpenes in unpolluted ambient air may be achieved within an 11.7 min chromatographic separation time (increasing to 19.7 min when simultaneous quantification of multiple oxygenated C9-C10 terpenoids is required, and/or when concentrations of anthropogenic VOC are significant). These analysis times potentially allow for a twofold to fivefold increase in measurement frequency compared to conventional GC methods. Here we outline the technical details and analytical capability of this chromatographic approach, and present the first in-situ Fast-GC observations of 6 monoterpenes and the oxygenated BVOC (OBVOC) linalool in ambient air. During this field deployment within a suburban forest ~30 km west of central Tokyo, Japan, the Fast-GC limit of detection with respect to monoterpenes was 4–5 ppt, and the agreement between Fast-GC and PTR-MS derived total monoterpene mixing ratios was consistent with previous GC/PTR-MS comparisons. The measurement uncertainties associated with the Fast-GC quantification of monoterpenes are ≤ 12%, while larger uncertainties (up to ~25%) are associated with the OBVOC and sesquiterpene measurements.

Total OH reactivity was measured during the Bio-hydro-atmosphere interactions of Energy, Aerosols, Carbon, H 2 O, Organics and Nitrogen-Southern Rocky Mountain 2008 field campaign (BEACHON-SRM08) held at Manitou Experimental Forest (MEF) in Colorado USA in August, 2008. The averaged total OH reactivity was 6.7 s −1 , smaller than that measured in urban (33.4 s −1 , Yoshino et al., 2012 ) and suburban (27.7 s −1 , Yoshino et al., 2006 ) areas in Tokyo in the same season, while sporadically high OH reactivity was also observed during some evenings. The total OH reactivity measurements were accompanied by observations of traces species such as CO, NO, NO y , O 3 and SO 2 and Volatile Organic Compounds (VOCs). From the calculation of OH reactivity based on the analysis of these trace species, 46.3% of OH reactivity for VOCs came from biogenic species that are dominated by 2-methyl-3-buten-2-ol (MBO), and monoterpenes. MBO was the most prominent contribution to OH reactivity of all trace species. A comparison of observed and calculated OH reactivity shows that the calculated OH reactivity is 29.5% less than the observed value, implying the existence of missing OH sinks. One of the candidates of missing OH is thought to be the oxidation products of biogenic species.

Continuous ground-based measurements of O 3 and its precursors were conducted in Dhaka, Bangladesh during April 2002–December 2005 in order to investigate ozone precursor characteristics and their distribution. Seasonal and diurnal variations of the O 3 , CO, NOx and SO 2 concentrations — are studied and their possible causes are identified. It is shown that most of the trace gases have peak concentrations in winter and base in monsoon period. Two major emission sources, vehicles and brick kilns, are attributed to the high levels of trace gases in winter. O 3 formation was mainly due to local activity and relied on photochemical processes with precursors. The occurrence patterns and the shape of a distribution of trace gases are obtained from histogram distribution. In most cases, the frequency distributions of observed trace gases show a peak to the lower concentration ranges (e.g. 0–10 ppb for O 3 , 0–500 ppb for CO, 0–20 ppb for NO, NO 2 and 0–10 ppb for SO 2 ) with a long tail to the right and unimodal in most of the cases.CO, NOx and SO 2 are significantly correlated throughout the entire data set, reflecting the overall influence of anthropogenic emissions.

Chromophoric water-soluble organic matter in atmospheric aerosols potentially plays an important role in aqueous reactions and light absorption by organics. The fluorescence and chemical-structural characteristics of the chromophoric water-soluble organic matter in submicron aerosols collected in urban, forest, and marine environments (Nagoya, Kii Peninsula, and the tropical Eastern Pacific) were investigated using excitation-emission matrices (EEMs) and a high-resolution aerosol mass spectrometer. A total of three types of water-soluble chromophores, two with fluorescence characteristics similar to those of humiclike substances (HULIS-1 and HULIS-2) and one with fluorescence characteristics similar to those of protein compounds (PLOM), were identified in atmospheric aerosols by parallel factor analysis (PARAFAC) for EEMs. We found that the chromophore components of HULIS-1 and -2 were associated with highly and less-oxygenated structures, respectively, which may provide a clue to understanding the chemical formation or loss of organic chromophores in atmospheric aerosols. Whereas HULIS-1 was ubiquitous in water-soluble chromophores over different environments, HULIS-2 was abundant only in terrestrial aerosols, and PLOM was abundant in marine aerosols. These findings are useful for further studies regarding the classification and source identification of chromophores in atmospheric aerosols.

In order to elucidate an impact of Beijing outflow on air quality in the mountainous area, measurement campaign was carried out in Mt. Mang, located 40 km north of Beijing in September 2007. Volatile Organic Compounds (VOC) observed at the site were mainly influenced by air masses arriving from urban areas. No significant impact of local emission was found. Correlation plots between selected VOC suggests several major emission sources as internal combustion, industrial emission, and coal, oil and biofuel burning. Air masses were classified into “polluted” (influence of Beijing and its satellite cities) and “clean” air mass by using backward trajectory analysis. Two air mass categories revealed significant different characteristics and mixing ratios. Reaction with OH is a major factor controlling mixing ratio of “clean” air mass while impact of dilution is also play important role on “polluted” air mass. Estimation of photochemical age of “polluted” air mass by assuming “clean” air mass for background mixing ratios reveals an averaged of 1.5–1.8 days.

Compressed Natural Gas (CNG) is an inexpensive, indigenous energy resource which currently accounts for the majority of automobile and domestic energy consumption in Bangladesh. This extensive CNG usage, particularly within the capital city, Dhaka, heavily influences the atmospheric composition (and hence air quality), yet to date measurements of trace gases in regions dominated by CNG emissions are relatively limited. Here we report continuous observations of the atmospherically important trace gases O3, CO, SO2, NOx and volatile organic compounds (VOC), in ambient air in Dhaka City, Bangladesh, during May 2011. The average mixing ratios of O3, CO, SO2 ,a nd NO x for the measurement period were 18.9, 520.9, 7.6 and 21.5 ppbv, respectively. The ratios of CO to NO reveal that emissions from gasoline and CNG-fuelled vehicles were dominant during the daytime (slope of w26), while in contrast, owing to restrictions imposed on diesel fuelled vehicles entering Dhaka City, emissions from these vehicles only became significant during the night (slope of w10). The total VOC mixing ratio in Dhaka was w5e10 times higher than the levels reported in more developed Asian cities such as Tokyo and Bangkok, which consequently gives rise to a higher ozone formation potential (OFP). However, the most abundant VOC in Dhaka were the relatively long-lived ethane and propane (with mean mixing ratios of w115 and w30 ppbv, respectively), and as a consequence, the ozone formation potential per ppb carbon (ppbC) was lower in Dhaka than in Tokyo and Bangkok. Thus the atmospheric composition of air influenced by extensive CNG combustion may be characterized by high VOC mixing ratios, yet mixing ratios of the photochemical pollutant ozone do not drastically exceed the levels typical of Asian cities with considerably lower VOC levels.

Measurement of Volatile Organic Compound (VOC) was carried out in suburban Bangkok during July 2–8, 2008. Analysis was performed using GC-FID and GC-MS. High mixing ratios of VOCs detected during the morning and evening are most likely due to vehicular emissions. Averaged VOC mixing ratios revealed distinct difference between mixing ratios of weekdays and weekend, which the latter were found to be lower. The most abundance species were propane and toluene. Ratios of benzene over toluene suggested that additional toluene mixing ratios was owing to industrial emission, which was particularly larger during weekdays. Comparison between C 2 Cl 4 and CH 3 Cl mixing ratios obtained for suburban Tokyo reveal a relatively lower influence of biomass burning than suburban Bangkok. Elucidating by Ozone Formation Potential, toluene was found to contribute the most to O 3 production followed by ethylene, m- , p- xylene, and propylene.

GC-FID analysis of polluted urban air samples detects a considerable number of unidentified peaks of volatile organic compounds (VOCs). In this study, a new method is proposed to estimate the contribution of the OH reactivity of such unidentified VOCs using a relative rate method. An air sample was analyzed by two methods: the conventional GC-FID method and a method where the sample was first exposed to the OH radicals generated in the photolysis of water vapor using a pen ray mercury lamp and then analyzed by the same conventional method. The difference in the peak areas of each species with and without OH exposure ideally depends on the OH reactivity of the species of interest. This difference in a standard gas sample that included 56 VOCs was observed through test measurements, and the validity of the system using the proposed technique was confirmed. An ambient air sample obtained in suburban Tokyo was then examined. From the peak area change of the identified species, the contribution of the unidentified VOCs to the OH reactivity was found to be about 22% of that of the identified VOCs. In a separate experiment, simultaneous measurements of the total OH reactivity, various trace gases, and the proposed technique to estimate the contribution of unidentified VOCs were conducted at a Tokyo suburb. The contribution of the unidentified VOCs to the total OH reactivity in suburban air was up to about 6% of the total OH reactivity, and the difference between the observed and estimated total OH reactivity was up to 20%.

Simultaneous ground-based measurements of ozone and carbon monoxide were performed at Oki, Japan, from January 2001 to September 2002 in order to investigate the O(3) and CO characteristics and their distributions. The observations revealed that O(3) and CO concentrations were maximum in springtime and minimum in the summer. The monthly averaged concentrations of O(3) and CO were 60 and 234 ppb in spring and 23 and 106 ppb in summer, respectively. Based on direction, 5-day isentropic backward trajectory analysis was carried out to determine the transport path of air masses, preceding their arrival at Oki. Comparison between classified results from present work and results from the year 1994-1996 was carried out. The O(3) and CO concentration results of classified air masses in our analysis show similar concentration trends to previous findings; highest in the WNW/W, lowest in N/NE and medium levels in NW. Moreover, O(3) levels are higher and CO levels are lower in the present study in all categories.

Aerial observation was conducted during spring (March-April) 2008 over the East China Sea to analyze the transport of atmospheric pollutants from East Asia and the transformation processes during transport. Concentrations of sulfur dioxide (SO2), ozone (O3), total reactive nitrogen (NOy), carbon monoxide (CO), and black carbon (BC) were measured on board the aircraft, and chemical analyses of aerosols were performed subsequently by high-volume filter sampling of aerosols and ion chromatography and inductively coupled plasma-mass spectroscopy (ICP-MS) analyses. The distributions of gases and aerosols clearly suggested a layered structure to the air mass, in good agreement with predictions of the CFORS (Chemical weather FORecast System) model. The non-sea-salt (nss)-(sulfate (SO4 2- ))/((SO2) + nss(SO4 2- )) ratio value, which increased from north to south along the aircraft flight track, indicated oxidation of SO2 to form sulfuric acid during transport. In addition, pronounced chlorine loss suggested that substantial production of acidic substances occurred in the air mass as it moved away from China. The negative correlation between the Cl - /Na + ratio and the nss-sulfate concentration suggested that the reaction of sulfuric acid with sea salt was the main cause of the strong chlorine loss. On 28 March a very clear layered structure of the air mass was observed that could be clearly explained by the CFORS computer simulation model. Therefore, here the observation results obtained on 28 March 2008 are reported.

Non-methane hydrocarbons (NMHCs) are known to have an important role on air quality due to their high reactivity. NMHC analysis has been performed on 148 ambient air samples collected at five different sites in the Kanto area (Tokyo metropolitan area and surrounding six prefectures) of Japan in summer and winter of 2008, and fifty NMHCs have been determined and quantified. A field measurement campaign has been conducted at one of the busiest intersections in Tokyo metropolitan area in winter of 2008. NMHC emissions are evaluated through comparison of distributions of individual NMHCs emitted from motor vehicles, which are estimated from the measurements, with those determined from the current emissions inventory. The comparison revealed that the measured distributions of acetylene, ethylene and toluene showed a good agreement with those estimated from the emissions inventory (the values estimated from the measurements are a factor of 1.5, 0.56 and 2.3 larger than the emissions inventory in median, respectively), however, propane and isobutane are found to be significantly underestimated in the emissions inventory (the measured values were a factor of 18 and 5.1 larger than the emissions inventory, respectively). The significant underestimate of propane can be explained by that the current emissions inventory does not consider emissions from liquefied propane gas (LPG) fueled vehicles. However, for isobutane, reasons for the underestimate are still unclear. Another field measurement has been conducted in summer of 2008, where the air samples have been collected at three different sites on the ground and by a helicopter as well. Remarkable high concentrations of 1-butene and cis- and trans-2-butenes have been sporadically observed in the samples collected at Urayasu in the coastal area of Tokyo bay. Calculated propylene equivalent (PE) concentrations of butenes revealed that those have a significantly important role in ozone formation when the air plume is affected by emissions from their emission sources. The PE concentrations of butenes varied from 0.1 to 39 ppbC, and accounted for 1.5–75% of total PE concentrations at Urayasu. Most of the continuous air quality monitoring stations does not record concentrations of individual hydrocarbons, therefore, the importance of reactive and low concentration hydrocarbon such as butenes might be overlooked in the current emissions inventory and/or air quality model. In this paper, the reliability of NMHC emissions is evaluated based on the field measurements. Their possible impacts on air quality in the Kanto area are discussed as well, based on the calculated propylene equivalent concentrations.

Owing to recent industrialization, Central East China has become a significant source of air pollutants. To examine the processes controlling the chemistry and transport of tropospheric ozone, we performed on-line measurements of non-methane volatile organic compounds (NMVOCs) as part of an intensive field campaign at Mount Tai, China, in June 2006 (MTX2006), using proton transfer reaction mass spectrometry (PTR-MS). Temporal variations of NMVOCs were recorded in mass-scan mode from m/z17 to m/z 300 during 12–30 June 2006. More than thirty kinds of NMVOCs were detected up to m/z 160, including alkenes, aromatics, alcohols, aldehydes, and ketones. In combination with non-methane hydrocarbon data obtained by a gas chromatography with flame ionization detection, it was found that oxygenated VOCs were the predominant NMVOCs. Diurnal variations depending mainly on local photochemistry were observed during 24–28 June. During the night of 12 June, we observed an episode of high NMVOCs concentrations attributed to the burning of agricultural biomass. The ΔNMVOCs/ΔCO ratios derived by PTR-MS measurements for this episode (with biomass burning (BB) plume) and during 16–23 June (without BB plume) are compared to emission ratios from various types of biomass burning as reviewed by Andreae and Merlet (2001) and to ratios recently measured by PTR-MS in tropical forests (Karl et al., 2007) and at urban sites (Warneke et al., 2007).