Methanol has been a common additive to promote denitrification in the active sludge method of sewage treatment. However, we found that methanol itself is not a substrate for denitrifying bacteria : the denitrifying bacteria actually utilize the organic compounds with C-C bonds which are produced from methanol by aerobic methylotrophs. Furthermore, a large quantity of scum, which was considered to be an aggregate of the aerobic methylotrophs, was formed and caused difficulties to treat when methanol was added. Glucose, the most favorable substrate for almost all the heterotrophic bacteria, was found to be an inefficient additive to promote denitrification. This may be caused by a rapid and marked drop in pH due to formation of a large amount of organic acids. On the contrary, fumaric acid was confirmed to be a very efficient additive to promote denitrification. And fumaric acid was completely utilized during nitrate presented in the sewage. It was considered that this compounds was utilized quickly and completely by denitrifying bacteria.

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Long-term background ozone data monitored at the clean remote sites in the Japan Islands between latitudes 28°N and 44°N, longitudes 128°E and 143°E were analyzed. It is found that the background ozone in the lower troposphere shows distinct seasonal variation and diurnal variation. The former variation exhibits a regular pattern with a maximum in spring and with a minimum in summer or autumn. It is considered that this pattern is a common feature of the lower tropospheric ozone at middle latitudes in the northern hemisphere. It is assumed that high ozone concentration in spring is due to injection from the stratosphere. While diurnal variation shows three kinds of characteristic patterns according with the topographical conditions at the monitoring sites. Some influence of anthropogenic pollution is inevitable at almost clean remote sites in the Japan Islands. Long-range transport of ozone in the lower troposphere was studied. By means of the trajectory analysis utilizing ozone and meteorological data at Mt. Yamizo, Mt. Odaigahara and the others, it was confirmed clearly that the ozone produced by photochemical reaction in the atmosphere polluted by anth ropogenic sources, i.e. the southern Kanto and the Osaka plain, was transported to the remote clean atmosphere, i.e. Mt. Yamizo and Mt. Odaigahara respectively in summer.

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Soil sampling is the key step in investigating soil pollution. Soil is by nature a heterogeneous material and element concentrations in soil differ from one site to another. Thus, it is essential to examine closely the relationship between soil sam pling procedure and the representativeness of the data obtained. We have tried to derive the relationship between number of soil samples n collected from a 1 ha plot (100 m×100 m) and a bias of estimated average element concentration Cn in surface soil at the plot to actual value C. For this purpose, four background sites (St. 1-3 in Hokkaido and St. 4 in Aomori Prefecture) were selected as representative sites, and variations of concentration of two major elements (Si and Al) and five trace elements (As, Cd, Cr, Cu, and Hg) in surface soil at a 1 ha plot were examined in detail at each site. The % difference between Cn and C was derived to be where σ is the geometric standard deviation of the element concentrations in surface soil at a 1 ha plot. In this paper, the effectiveness of increasing n in reducing D is discussed according to the relationship between D and n obtained for each element at each site. Furthermore, the correlation of distribution of the element concentrations in surface soils, the vertical distribution of the element concentrations and the varia tion of the Enrichment Discrimination Factor for the elements at the background sites are discussed.

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