Michio Hirota

Gas-chromatographic measurement of atmospheric methane in Japan

Abstract In order to obtain the distribution and variation of atmospheric CH4 in Japan, measurement of CH4 in the surface air in Tsukuba was performed from June 1985 to March 1988. Vertical distributions were also measured up to an altitude of 7 km over Japan in 1986 and 1987. Mixing ratios of CH4 generally decreased from the surface to the altitude of 3 km. From 4 to 7 km, nearly constant mixing ratios were obtained. Yearly mean volume mixing ratios of CH4 at Tsukuba were 1.768 ppm in 1986 and 1.781 ppm in 1987. These values were much higher than those of other sites in the same latitudinal zone. There could be a longitudinal variation of atmospheric CH4, though the effect of the pollution from local sources such as paddy fields could not be excluded. From a linear fit for 12-month running means, the estimated growth rate was 9.0 ppb a−1. This is lower than the one observed in the early 1980s.

The reducibility and polarography of Pd(II) complexes in aqueous solution

Abstract A polarographic investigation of Pd(II) complexes has been attempted. Because the reduction waves for the complexes [Pd L 4 ] ( L = Cl, Br, SCN, NO 2 , 1 2 C 2 O 4 ) follow the dissolution wave for metallic mercury, it is not possible to determine the half wave potentials for these complexes. In the case of the chloro and bromo complexes, the surface of metallic mercury turns dark grey. No detectable change is observed in the case of the thiocyanato, nitro, and oxalato complexes. These results suggest that in the former case palladium metal deposits on the surface of metallic mercury, whereas in the latter case, the complexes form palladium amalgam. On the other hand, the complexes ( L = β, γ-picoline, CH 3 NH 2 , ethylenediamine, NH 3 , Cn) do not react with metallic mercury and half wave potentials can be measured. When N,N,N′,N′ -tetramethylparaphenylenediamine (TMPD) is used as the reducing reagent, similar results for the reducibility of the complexes are obtained. On the basis of the present experimental results, the reducibility of the Pd(II) complexes is determined in the following order. L = Cl, Br > SCN, NO 2 , C 2 O 4 > γ-picoline, β-picoline > CH 3 NH 2 , ethylenediamine > NH 3 > CN.

Polarographic reduction of palladium(II) cyano complex in aqueous solution

Abstract The electrode reactions of the palladium(II) cyano complex, [Pd(CN)4]2− in aqueous solution is studied by d.c.- and oscillo-polarography. The d.c. polarographic reduction of [Pd(CN)4]2− is irreversible and proceeds by a two-electron step. In the oscillopolarogram, three anodic waves are observed at the potentials of −2·25, −0·85 and −1·6 V (vs SCE), respectively. The third peak potential is near the cathodic peak potential of [Pd(CN)4]2− (−1·83 V). The peak potential of the second anodic wave is almost identical with the oxidation potential of the reduction product of [Pd(CN)4]2− by sodium amalgam. The half wave potential of the latter is −0·932 V. It is concluded that the palladium(O) and palladium(I) cyano complexes are produced in aqueous solution by the reduction of [Pd(CN)4]2− at the dropping mercury electrode.

Lidar Observations of the PSCs and Stratospheric Aerosols over Eureka in Canadian Arctic

The behavior of the polar stratospheric clouds, PSCs, and the stratospheric aerosols is very important to understand the ozone destruction in the polar stratosphere. Lidar observations of the PSCs and stratospheric aerosols have been carried out at the Arctic stratospheric ozone observatory, AStrO, near the Eureka weather station at 80°N, 86°W since February 1993, using a depolarization sensitive NdrYAG lidar. During the four winter campaigns from February 1993 to February 1996, no PSC was observed in the winter of 1992/1993 and 1993/1994, however, several PSC events were observed in the winter of 1994/1995 and 1995/1996. The first event appeared on December 12, 1994 and continued to December 16, 1994. The PSCs in this event are categorized into the TYPE la, which is considered to be crystallized nitric acid trihydrate (NAT) particles. The second event happened from January 5 and 14, 1995, with a short disappeared period on 10 and 11. In the later event, less depolarized component hung down to about 14 km altitude from the main peak, where the TYPE la existed, with higher depolarization around 20 km. The temperature in the hung down region was obviously higher than the freezing point of the NAT. This suggests that the compositions of the PSCs are not only NAT and/or ice but also other species such as sulfuric acid tetrahydrate (SAT) and sulfuric acid dihydrate (SAD) particles.