Continuous measurement of methane flux over a larch forest using a relaxed eddy accumulation method

We measured the methane flux of a forest canopy throughout a year using a relaxed eddy accumulation (REA) method. This sampling system was carefully validated against heat and CO₂ fluxes measured by the eddy covariance method. Although the sampling system was robust, there were large uncertainties in the measured methane fluxes because of the limited precision of the methane gas analyzer. Based on the spectral characteristics of signals from the methane analyzer and the diurnal variations in the standard deviation of the vertical wind velocity, we found the daytime and nighttime precision of half-hourly methane flux measurements to be approximately 1.2 and 0.7?μg?CH₄?m^?2?s^?1, respectively. Additional uncertainties caused by the dilution effect were estimated to affect the accuracy by as much as 0.21?μg?CH₄?m^?2?s^?1 on a half-hourly basis. Diurnal and seasonal variations were observed in the measured fluxes. The biological emission from plant leaves was not observed in our studies, and thus could be negligible at the canopy-scale exchange. The annual methane sink was 835?±?175?mg?CH₄?m^?2?year^?1 (8.35?kg?CH₄?ha^?1?year^?1), which was comparable to the flux range of 379–2,478?mg?CH₄?m^?2?year^?1 previously measured in other Japanese forest soils. This study indicated that the REA method could be a promising technique to measure canopy scale methane fluxes over forests, but further improvement of precision of the analyzer will be required.     

Imaging polarimetry of Comet 9P/Tempel before and after the Deep Impact

The NASA's Deep Impact mission was the first impact experiment to a cometary nucleus. The target of the mission was Comet 9P/Tempel, one of the Jupiter family comets. The impact was performed on July 4th, 2005. Imaging polarimetric observations were carried out by Polarimetric Imager for COmets (PICO) mounted on the Lulin One-meter Telescope (LOT) at Lulin Observatory, Taiwan. Intensity and linear polarization degree maps were obtained on July 3-5, 2005. Impact ejecta plume was clearly recognized in the enhanced intensity map. Furthermore, arc-shaped region of high polarization was recognized in the polarization map. Dust grains in this region had larger expansion velocity than the grains which provided the brightest area in the intensity map. comparing our results with the MIR spectroscopy obtained by Subaru Telescope we conclude that very small carbonaceous grains might be responsible for the region of high polarization.     

Concentration of polychlorinated biphenyls (PCBs) in beached resin pellets: variability among individual particles and regional differences

Concentrations of polychlorinated biphenyls (PCBs) in beached resin pellets were examined to reveal variability between individual particles and differences among beaches. Fifty-five resin pellets from a beach in Tokyo were individually analyzed for PCBs, and showed concentrations ranging from <28 to 2,300 ng/g. This indicates that concentrations are highly variable between particles. Among several characters, discoloration (e.g., yellowing) had a positive relationship with PCB concentration: discolored pellets contained more PCBs than others on most of the beaches sampled. Given the color-selective ingestion of food by some organisms, this may be ecotoxicologically important. Measurements of samples from 47 beaches in Japan showed regional differences in PCB concentrations in resin pellets consistent with those in mussels. Sporadic high concentrations of PCBs were also found in pellets from remote islands, suggesting that resin pellets could be the dominant route of exposure to the contaminants at remote sites. The similarity of PCB concentrations between resin pellets and mussels suggests a potential use of resin pellets to monitor pollution in seawater.     

An improved method for the determination of phytoplankton chlorophyll using N,N-dimethylformamide

Non volatile N, N-dimethylformamide (DMF) at room temperature is proposed as a new solvent for determining the chlorophylla in cultured and natural phytoplankton samples. Advantages of DMF compared to the solvents ordinarily used are (1) higher extraction efficiency, (2) rapid extraction time of 30 min, (3) simple extraction procedure requiring neither extra heating nor grinding, but soaking, and (4) a long stable life of chlorophylla (at least one month at 5°C in the dark).     

Polychlorinated biphenyl (PCB) concentrations and congener composition in masu salmon from Japan: A study of all 209 PCB congeners by high-resolution gas chromatography/high-resolution mass spectrometry (HRGC/HRMS)

We collected two subspecies of masu salmon: Oncorhynchus masou masou from four localities (southern Sea of Japan northward to Hokkaido) and O. masou ishikawae from upstream from Ise Bay close to a heavy industrial area. All 209 PCB congeners were analyzed using HRGC/HRMS. PCA ordination of congener concentrations divided data into three groups: (i) ssp. masou from Hokkaido, (ii) ssp. masou from the other regions and (iii) ssp. ishikawae. The highest ∑ PCB concentration (40.39 ng/wet wt) was in ssp. ishikawae followed by ssp. masou from southern waters; however the TEQ_{dioxin-like PCBs} was highest in ssp. masou from southern water (1.96 pg-TEQ_{dioxin-like PCBs}/g wet wt.) due to the high proportion of congener #126 in its complement (#126 has the highest toxic equivalency factor among congeners). There is likely a contamination source offshore in the southern Sea of Japan and/or along the migratory route of ssp. masou.