Katsuyuki Izumi

Formaldehyde measurements in residential indoor air using a developed sensor element in the Kanto area of Japan

UNLABELLED We undertook this to determine the formaldehyde concentration in Japanese houses and the relationship between formaldehyde levels and the age and temperature of a house using a sensor element that we developed for time-integrated measurements of formaldehyde concentration in actual environments. We evaluated the correlation between the formaldehyde concentration estimated by the dinitrophenylhydrazine (DNPH)-derivatization method and that obtained with our sensor element. We found a linear relationship between the two results indicating that reliable measurements can be performed using the developed sensor element in actual environments. The indoor concentration of formaldehyde was determined in a study of 34 homes in the Kanto area of Japan, between September 28 and October 27, 2007. We obtained the highest formaldehyde concentrations of 92 ± 15 μg/m(3) for apartments 0-2 years after their renovation, and a simple linear relationship was found between formaldehyde concentration and the age of the apartment. We also found that the formaldehyde concentration in a room containing furniture increased by 10% when the temperature increased by 1°C. PRACTICAL IMPLICATIONS This study contributed to the measurements of indoor formaldehyde levels. We have used a newly developed sensor for time-integrated measurements of formaldehyde concentrations. This sensor does not need a power supply during exposure to air, and does not need special skills to use. This research showed that homeowners successfully deployed the sensor at the desired place and desired period in their house by themselves. Formaldehyde is emitted by various off-gassing sources, such as furniture. Therefore, for example, homeowners may want to measure the change of formaldehyde levels in their house before and after installing new furniture. This sensor may also be deployed by occupants to reduce the cost of a large-scale exposure assessment study.

EXPERIMENTAL AND THEORETICAL ANALYSIS OF MECHANICAL COATING PROCESS OF PARTICLES WITH THE THETA COMPOSER

Studies were carried out on coating glass beads with fine hematite particles by use of the theta composer, a newly developed high-shearing-type mixer. Topics of study included the effects of rotational speed of the rotor, N r , (i.e., tangential velocity of the rotor tip, vr ), and a gap width between the rotor and the wall of the vessel, l, on the coating process. The amount of hematite particles deposited on glass beads was plotted versus a parameter that relates a cumulative shear force acting on particles over a coating period t. All experimental data could be fitted by a single curve, and the parameter ϵ was found to describe the coating process in the theta composer. Compression of core particles by the rotor was also analyzed using a 3-D DEM simulation. Average contact force by the rotor was found to be proportional to vr and inversely proportional to l. Thus, a cumulative shear force acting on a core particle is proportional to (vr /l)(vr t) after the particle passes through the gap N r t times. Reasonable agreement was found between the experimental results and those of simulation. The coating process can be properly described by the parameter ϵ.

Interferences of various gases on porous glass-based formaldehyde sensors

In order to examine the influences of various gases on sensor elements developed recently for the detection of gaseous formaldehyde, experiments were made in which the elements were exposed to air including one of the test gases. The elements are made of a porous glass sheet in which beta-diketone (acetylacetone or 1-phenyl-1,3-butanedione) and ammonium ion are impregnated and both of the elements turn yellow from colorless upon exposures to formaldehyde. The experiments were made under a concentration of 2000 ppm and a 50% relative humidity. As a result, aromatics such as benzene, toluene and ethylbenzene were found to cause no color changes. On the other hand, aldehydes and compounds having one or more C-C double bonds turned the two elements yellow. However the effects of these compounds are expected to be negligible under the realistic conditions, in view of the facts that the values of absorbance of light at peak wavelengths for these compounds were small and that the concentrations of the gases tested in this study were several orders of magnitude higher than those in the real atmosphere, even in the indoor environment.

Fine Particle Dry Deposition onto a Cropland — a Trial to Estimate Deposition Velocity

The dry deposition velocity of fine particles is usually on the order of several tenths of cm s−1, and accordingly, the concentration gradient of particles above the surface is very small. This makes the application of the gradient method to the determination of the particle deposition velocity very difficult. This study is a trial to find a way around this difficulty. The idea is to evaluate the thickness of the molecular diffusion layer, zb by simultaneously measuring the concentration gradient of gaseous species such as SO2 ; zb is obtained by combining the turbulent and molecular transport equations for the gas. Then the particle deposition velocity is estimated on the basis of zb and the Brownian diffusion coefficient with an assumption that zb is equal to the thickness of the Brownian diffusion layer. By applying this method to the data collected in a field observation, the velocity of deposition onto a cropland was estimated for submicron particles.

Evaluation of air quality with simple and easy chemical sensors: Development of porous glass-based elements

The authors are tackling the development of novel chemical sensor elements for detecting air pollutants. The base material of the sensor elements is porous glass, which has favorable features such as transparency and porosity. The sensor elements were prepared by impregnating reagents in a sheet of porous glass. The reagents were the Saltzman reagent for the detection of nitrogen dioxide, beta-diketones for formaldehyde and potassium iodide for oxidant. The resultant elements were colorless. The first element was highly sensitive and changed to clear wine red upon exposures to nitrogen dioxide. The second element for formaldehyde developed yellow and was detectable as low as a few tens ppb for an exposure time of 8 h. The third element for oxidant also showed high sensitivity. Evaluation of the effects of various gases on these elements, which are indispensable in applying them to the real atmosphere, is underway except for the NO2 elements. The concept leading to the present study is briefly explained.

Rate of Sulfur Dioxide Removal Artificial Cloud Experiments Utilizing a Long Vertical Shaft

Removal of sulfur dioxide through the absorption into cloud droplets is the initial stage of acid rain formation. We studied this process by forming an artificial cloud with a spatial scale close to the real one. We used a vertical shaft of 430 m in length in an abandoned mine, and operating an electric fan placed at the top of the shaft, generated an updraft of about 1 m s−1 of the air humidified by underground water. This produced an artificial cloud rising about 400m above the cloud base observed at a height of about 35 m from the bottom. At the bottom of the shaft, we emitted SO2 gas into the air stream, and measured its concentration profile by an SO2-meter loaded on an elevator going up and down in the shaft. From the slope of the observed decay curve, we evaluated the rate constant for the absorption to be 0.010 s−1. This value was found to agree in order of magnitude with an estimate derived on the basis of the laminar film model for mass transfer.