Hiroshi Hara

Temporal variations of nitrogen wet deposition across Japan from 1989 to 2008

[1]xa0To evaluate temporal variations in nitrogen wet deposition across Japan during 1989–2008, we analyzed results of a chemical transport model (the Models-3 Community Multiscale Air Quality) and observational data. The model successfully reproduced the general patterns of spatial and temporal variations of observed NO3− wet deposition rates. Wet deposition rates of NO3− across Japan increased during 1989–2008, with rates of increase of 2–5%/yr. Sensitivity simulations indicated that the increase of NO3− wet deposition rates was mostly (61%–94%) explained by the increased emissions of atmospheric pollutants in China. Contributions of Chinas emissions increased from 29%–35% during 1989–1993 to 43%–61% during 2004–2008, suggesting that transboundary pollution had a large impact on NO3− wet deposition in Japan. The contribution of observed NO3− to total nitrogen wet deposition (i.e., NO3− + NH4+) increased in southwestern Japan, and currently, NO3− and NH4+ make similar contributions to nitrogen wet deposition across Japan. Interannual variation of NO3− wet deposition was further evaluated using a meteorological index, area-weighted surface pressure anomaly (ASPA). When ASPA was negative, air masses from the Asian continent were more directly transported to Japan, and NO3− concentrations across Japan became high. Thus, anomalies of NO3− concentrations were negatively correlated with ASPA. Anomalies of NO3− wet deposition rates, however, showed a weak positive correlation with ASPA, reflecting a positive correlation between anomalies in precipitation rates and ASPA. This result strongly suggests that precipitation patterns have a large impact on the interannual variation of NO3− wet deposition across Japan.

Ammonia denuder for field sampling of sulfuric acid particles

Abstract The oxalic acid coating procedure for an ammonia denuder for the field sampling of sulfuric acid particles is modified. The denuder consisted of four glass tubes (100cm length, 0.8cm i.d.), coated on the inside with 4 % oxalic acid in 90 % aqueous ethanol. It gave a good Gormley-Kennedy plot at a total flow rate of 20l min −1 . In ambient air sampling, it removed more than 95 % of the gaseous ammonia without any appreciable particle loss in the submicrometer size range.

Field investigation of the radio transmission performance and distance in a environmental wireless sensor network

One of the problems affecting sensor networks in natural environments is the attenuation of radio waves due to high humidity. This attenuation is greatest in the case of a 2.4-GHz radio wave. A system is being developed that uses a transmission control method to estimate communication environment fluctuations caused by changes in the natural environment. This paper discusses the transmission performance in wireless sensor networks in terms of the relationships between wireless transmission performance, distance, and environmental conditions observed in field experiments. Measurements were made with sensor nodes equipped with a weather-sensing device at an experimental field of the university, called the Field Museum (FM) Tamakyuryo in Tokyo. Over the course of the two-month experiment, measurements of the parameters throughput, signal strength, humidity, and atmospheric pressure were taken in the field. The results confirmed that the distance between sensor nodes and the season of measurement affect the throughput and stability of data transmission. Therefore, it is suggested that node position, distance between nodes, and environmental conditions are important factors in improving transmission performance and battery efficiency for environmental wireless sensor networks.

Increases of wet deposition at remote sites in Japan from 1991 to 2009

Temporal trends in wet deposition of major ions were explored at nationwide remote sites in Japan from April 1991 to March 2009 by using the seasonal Kendall slope estimator and the nonparametric seasonal Kendall test. For the trend analysis, datasets from eight remote sites (Rishiri, Echizenmisaki, Oki, Ogasawara, Shionomisaki, Goto, Yakushima, and Amami) were selected from the Japanese Acid Deposition Survey (JADS) conducted by the Ministry of the Environment. Deposition of H+ has been increasing at remote sites in Japan on a national scale. Significant (pu2009≤u20090.05) increases in H+ deposition were detected with changes of +3–+9xa0%u2009year−1 at seven sites, while insignificant increases were observed at one site. Depositions of non-sea salt (nss)-SO42− and NO3− significantly increased at four and six sites, respectively, with changes of +1–+3xa0%u2009year−1. Significant increases in precipitation at four sites would have contributed to the increase in depositions of H+, nss-SO42−, and NO3−. The emission trends of SO2 and NOx did not corresponded to the deposition trends of nss-SO42− and NO3−. The different trends indicated that temporal variation of precipitation amount trend dominated the deposition trends.

Differences in the Spatial Variability Among CO2, CH4, and N2O Gas Fluxes from an Urban Forest Soil in Japan

The spatial variability of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) fluxes from forest soil with high nitrogen (N) deposition was investigated at a rolling hill region in Japan. Gas fluxes were measured on July 25th and December 5th, 2008 at 100 points within a 100xa0×xa0100xa0m grid. Slope direction and position influenced soil characteristics and site-specific emissions were found. The CO2 flux showed no topological difference in July, but was significantly lower in December for north-slope with coniferous trees. Spatial dependency of CH4 fluxes was stronger than that of CO2 or N2O and showed a significantly higher uptake in hill top, and emissions in the valley indicating strong influence of water status. N2O fluxes showed no spatial dependency and exhibited high hot spots at different topology in July and December. The high N deposition led to high N2O fluxes and emphasized the spatial variability.

Field experiments for developing transmission control based on weather estimation in an environmental wireless sensor network

One of the problems affecting sensor networks for natural environments is the attenuation of radio waves due to high humidity, and the attenuation is worst in the case of a 2.4 GHz radio wave. We are developing a transmission control method that estimates communication environment fluctuations caused by changes in the natural environment. This paper discusses a transmission performance in wireless sensor networks in terms of correlations between wireless transmission performance and environmental conditions observed in filed experiments. Measurements were made with sensor nodes equipped with a weather sensing device at an experimental filed of the university, Field Museum (FM) Tamakyuryo in Tokyo. During a one-week experiment, measurements of some parameters, a Throughput, signal strength, humidity, and atmospheric pressure were taken in the field. The results confirmed that increasing humidity definitely decreased the throughput. Temporal changes of the atmospheric pressure during the ongoing measurements will foresee short-term weather changes, which would enable to keep the transmission in control under the foreseen weather conditions.

A PMF-based trajectory methodology applied to daily precipitation and wet deposition data in Japan

Positive matrix factorization (PMF) was applied to daily wet deposition data from three stations in Japan to find the source profiles from which the precipitation samples are constituted. For most ions more than 90% of the weighted variation was explained with 4 factors. The factors are characterized by the following compounds: strong acids (H2SO4 and HNO3), (NH4)2SO4, NaCl, and CaSO4. The anion-cation balance was fairly good in the factors. Based on the chemical compositions of the factors, a time series of the factor contributions, and the results from trajectory analysis, the factors are considered to represent sea salt, soil, (NH4) 2SO4 and acidity. Although the total nss-SO4 wet deposition amount decreased in the last 7 years at Wajima station, the contributions of the (NH4) 2SO4 factor to nss-SO4 wet deposition were fairly constant (ca.50%). The acidity seemed to be controlled by the neutralization by soil particles.

The Morphology of Paper-making Non-wood Fibres in China

中国で製紙用原料として使用されている非木材植物のうち, 竜鬚草 (〓須草), 芒稈 (芒〓), 竹, 竹の皮, 麦わら, 黄麻じん皮部の6種について, その構造および細胞形態を光学顕微鏡により検鏡した。さらに各植物の繊維および代表的な細胞のディメンションを測定した。この結果, 単子葉植物の竜鬚草, 芒稈, 竹, 竹の皮, 麦わらの稈および葉の構造, 構成細胞は類似しているが, 各細胞のディメンション, 形態に各々特徴がみられた。黄麻じん皮部は, じん皮繊維と師部柔細胞のみからなり, じん皮繊維の形態に特徴が見い出された。