Tree and forest declines are noted in different areas of Japan and causal effects of acidic deposition are being disputed. Exposure experiments have been conducted to assess cause-effects relationships with acidic deposition and forest/tree decline. Total of 47 tree species were exposed to simulated acid rain to evaluate sensitivity by the injury occurrence. Growth responses of 16 species to wet deposition were analyzed after 27 months exposure experiments. Results suggested that sensitivity based on the growth responses were not always coincided with that by visible injury development. Rain acidity below pH 4.0 could induce deleterious direct effects on broad-leaved trees, however, coniferous trees did not show significant growth reduction. This suggests that current acidity of the precipitation does not have a direct linkage with tree/forest decline in Japan.
Simulated acid rain at pH 3.0 enhanced plant growth, however, its combination with ozone induced an imbalance of carbon allocation as indicated as increased top/root dry weight ratio with increasing ambient ozone concentration. This result suggests that increased nitrogen deposition probably as nitrate may aggravate predisposing ozone effects on tree growth.
Sulfur dioxide and/or ozone induced complicated differential growth responses than the wet deposition did. Some indicated additive harmful effects of sulfur dioxide with ozone and others showed synergistic adverse effects. The results suggest that current ambient level of ozone may have a subtle threat to ozone sensitive species. Differential sensitivity of plants to gaseous air pollutants and its critical level will be a more important factor to preserve natural vegetation and forests, rather than the soil acidification stress due to wet deposition.

View full abstract

Forest decline is one of the serious environmental problems worldwide. Although the causes and/or mechanisms of forest decline are different among the sites, tropospheric ozone (O₃) is considered to be environmental stress relating to these phenomena in North America and Europe. Therefore, there are many experimental studies on the effects of 0₃ on growth and physiological functions of tree species native to Europe and North America. Over the past 10 years, on the other hand, several research institutes and universities in Japan have been conducting experimental studies on the effects of 0₃ on Japanese forest tree species. In this review, we summarized the results obtained from experimental studies on the responses of forest tree species to O₃. Based on the studies conducted in North America, Europe and Japan, exposure to ambient levels of O₃ below 100 n1·1^-1 (ppb) for several months is sufficient to inhibit dry matter production and physiological functions such as photosynthesis of sensitive forest tree species such as Siebold's beech and Japanese zelkova. To evaluate critical level of 0₃ for protecting Japanese forest ecosystem, further experimental studies are needed on the effects of this pollutant on growth and physiological functions of Japanese forest tree species.

View full abstract

Bio-briquette is a sort of composite fuel consisting of 70 to 85 percent of coal and 15 to 30 percent of biomass by weight, produced by high pressure briquetting method with compression only in the roll press technique without any binder. The biomasses working as a binder are various woody wastes and agriculture wastes such as rice straw, rice bran, sorghum stalk, wheat straw and so on. Total yearly output of woody wastes and agriculture wastes in Chongqing of China amounted to ca. 18.0 million tons based on our investigating data. Using 5% of them, yearly output of bio-briquette will be ca. 3.60 million tons and enough as the domestic fuels. So, there were enough biomass materials to produce bio-briquette in Chongqing.
Ten types of biomasses including 4 types of agriculture wastes, 1 type of woody waste and wild grass, and 4 types of food manufacturing wastes collected in Chongqing were investigated for their combustion characteristics, emissions, binder action and breaking strength of bio-briquette prepared from each of them. The experimental results indicated that there were little emissions of air pollutants from biomass combustion and emission amounts for HCl and SO₂ were 35-912 and 52-1764mg per lkg of biomass, respectively. Compared with raw coal, the biomass can reduce the ignition temperature and increase the combustibility of the bio-briquette. The breaking strength of the bio-briquette increased with increase of addition amount and lignin contents of biomasses, which were in range of 12.1-33.3%. It is estimated based on our experimental results that the reduction efficiency of HC1, SO₂ and dust for the biobriquette ranged 26-61%, 82-87% and 55-83%, respectively. As a useful countermeasures for control of air pollutants discharged from civilian and small factory coal combustions, the bio-briquette with satisfactory strength could be produced by adding 25% biomasses without any special binder.

View full abstract

Triangle odor bag method which is adopted on the offensive odor control law is one of the sensory methods to evaluate offensive odor totally. In order to enhance the precision of triangle odor bag method, the research was carried out with changing parameter conditions of present method by computer simulation. As a result of the research, it was found that the precision of the present method for exhaust gas was satisfactory. However, the dilution ratio of the present method for ambient air should be changed according to the necessary information. Concretely, it is possible to measure the odor index with high precision by setting dilution ratios based on half of range lower limit of odor index and three times of range upper limit of odor index.

View full abstract

A simple method using a high-performance activated carbon column was developed for simultaneous determination of 23 kinds of volatile organic compounds (VOCs) in the air. An activated carbon (CQS) which had a larger specific surface area, a more extensive pore size distribution and less of an adsorption capacity of water vapor in comparison to the seven conventional adsorbents was selected for the sampling column. The recovery performance tests were carried out by using the column in which 0.7 g of CQS or each of the conventional adsorbent was packed. As a result, the recoveries from the CQS packed column were the highest. All the VOCs were eluted with 10 mL of n-decane at a flow rate of 0.3 mL/min from this CQS packed column. However, in the case of high humidity for a long period of time, the adsorption capacities of the VOCs whose boiling points were low and solubilities in water were high were decreased. If a desiccant pre-column packing with 25 g magnesium perchlorate of 0.83-2.4 mm was used, all the VOCs were able to recover completely. Furthermore, the cross-check tests by the present method and the canister method were carried out, and it was confirmed that the measured data by both methods agreed well. The reproducibility of the present method was better than±10%.
Consequently, 23 kinds of VOCs in the air could be measured simultaneously and accurately by the present method using the high-performance activated carbon column with the magnesium perchlorate column.

View full abstract

Corrosion inside pay phones was evaluated for the first time using the metal plate exposure method at this time. There have been no previous environmental investigations of the inside of pay phones located outdoors. The amount of corrosion inside and outside pay phones set up in nine in Kyusyu, which included a volcanic area, a coastal area, and several industrial areas, were evaluated by setting up silver plate and copper plate for about one month. The main results of the investigation are as follows.
(1) Sulfur and chlorine corrosion occurs in pay phones. This caused by the inflow of corrosive gases into the pay phone.
(2) The amount of sulfur corrosion inside pay phones is dependent on whether the pay phone is a volcanic area and an industrial region, etc. Putting the area aside, the ratio of the sulfur corrosion inside pay phones to that outside of pay phones is fixed at about 0.3.
(3) For the amount of chlorine corrosion inside pay phones, dependency on the type of area was comparatively low and almost constant.
(4) When the amount of corrosion inside pay phones was compared with the amount of corrosion inside NTT buildings in the Kanto area, the amount of sulfur corrosion inside pay phones was less than that inside the NTT buildings. However, the amount of the chlorine corrosion inside pay phones is larger than that inside the NTT buildings.

View full abstract