The potential CO2 and CH4 production in Japanese paddy fields were estimated from chemical properties of paddy soils of respective soil series, their acreage and thermal regimes during rice growing period. Total carbon mineralization (CO2 plus CH4) was calculated from the estimation of nitrogen mineralization of soil organic matter under anaerobic incubation. The assignment of mineralized carbon to CH4 portion was calculated from the ratio of oxidation capacity, represented by free iron content of soil, to reduction capacity, represented by estimated NH4 production during rice growing period. The CO2 and CH4 production from Japanese paddy fields were estimated to be 3.8×106 and 9.6×104 ton-C/one crop season, respectively. Soils classified to Gray Lowland Soil Soil Series Group (SSG) produced most (37% and 41% of the total CO2 and CH4 production), followed by soils of Gley Soil SSG (26% and 20%). As for the CO2 and CL production per the unit area, soils of Andosol SSG produced most in CO2 (2.4 ton-C/ha) and soils of Gleyed Andosol SSG most in CH4 (73 kg-C/ha). The CL production increased sharply as the fields locate more south. The CL production was influenced more by the temperature during rice growing period and by the type of SSG than the CO2 production.

View full abstract

Volatile chlorinated hydrocarbons (VCHs) in the soil and air were measured at a rural, semi-rural, and industrial area. Trichloroethylene, tetrachloroethylene, 1, 1, 1-trichloroethane, dichloromethane and chloroform were always detected in the soil even at rural and semi-rural areas (Nikko and NIES). The concentrations at these areas were in the range of 10-2-100ng/g soil, and had vertical profiles with maxima near the soil surface. These findings suggest that VCHs are transported from the atmosphere into the soil. On the other hand, at the polluted area where the underground-water was known to be heavily contaminated with VCHs, much higher concentrations were detected in the soil, with the highest being observed in the deeper soil, showing an upward movement of VCHs.

View full abstract

High concentration of air pollutants like nitrogen oxides found in an urban area during the nighttime was shown to be closely related to urban boundary layer (UBL) heights and wind speed. The UBL heights were estimated from continuous measure ments of aerosol profiles with a Mie lidar. Since the aerosol profiles reflect the structures of UBL, they can be used to infer the heights of UBL. When defining a stagnant factor as an average of the reciprocal of the product between the height of UBL and the wind speed, the nighttime averages of nitrogen oxide and nitrogen dioxide were shown to be linearly proportional to the stagnant factor.

View full abstract

In a previous paper, we proposed a simple procedure for measuring the acidneutralizing capacity (ANC) of soil, which determines the amounts of exchangeable bases and carbonates making up (ANC) c of soil and the amount of exchangeable OH making up (ANC) a and then calculates ANC from both values. The equations for ANC were derived by considering the fact that the effectiveness of (ANC) a depends on the anion composition (the equivalent ratio of SO₄²- ; α) of precipitation. At that time, H+ was regarded as the only cation in precipitation and the equivalent ratio of H+, ξ, was assumed to be unity. As natural precipitation, however, includes other cations such as NH₄⁺ and Ca²⁺, ξis lower than unity. This means that ANC is underestimated under the α<ξ<1 condition. In this paper, the ANC equations are improved by considering the ξ<1 condition, and the applicability of the new equations is verified through soil-column experiments. The improved equations are as follows :(1) ANC=(ANC)c/1-α/ξ, provided α/ξ<(ANC)a/(ANC)c+(ANC)a (2) ANC= (ANC)c+ (ANC)a, provided the other conditions The results for ANC calculated from the improved equations gave good agreement with those obtained from soil-column experiments using simulated acid rains (pH 3) with ionic compositions adjusted to meet the conditions ξ>α, ξ=α and ξ<α.

View full abstract

The relationships among the distributions of secondary air pollutants represented with oxidant index (OxI), precipitation in the growing season (ATP), and the distribution of declined Japanese cedar (Cryptomeria japonica D. Don) trees in the Kansai-Setouchi District were discussed. OxI is the average total number of hours per year from May to September in 1980 to 1984 for which oxidants exceeded the Japanese environmental standard of 0.06 ppm/hr and ATP is the average total precipitation from May to September in 1979 to 1987. The distribution of declined Japanese cedar comprised a large region coinciding roughly with the regions having an OxI more than 100. These regions tended to be inland areas suffering the effects of air pollutants transported long-range and coastal regions where air pollutants were circulated by the action of land and sea breezes. However, in spite of a high OxI, damage was less pronounced in those areas with an ATP more than 800mm. This suggests that a combination of high levels of secondary air pollutants and low levels of precipitation during the cedar growing season is a possible contributing factor to Japanese cedar decline.

View full abstract

[in Japanese]

View full abstract