To obtain some fundamental knowledge to suppress the formation of long-lived and highly reactive gasphase radicals from combustion smoke of combustibles like polymethyl methacrylate (PMMA), we have studied about suppression effects of amines and halogenated compounds, using the electron spin resonance (ESR) spin-trapping technique.
As a result, gas-phase radicals were not formed from combustion smoke of amines and halogenated compounds, and when those compounds were added to PMMA, the amounts of gas-phase radicals were remarkably reduced. These effects may come from the suppression of the formation of meta -stable compounds like dialkyltrioxide, which is thought as the source of long-lived gas-phase radicals, by hydrogen cyanide or hydrogen halide formed from the added amines or halogenated compounds in the combustion.

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In order to study the effect of road structure and road side planting on soil heavy metal content, the variation of these contents in soils were examined. Soil samples were collected at Joban Highway for bank, viaduct, cut, canal, semi underground structures and near tunnel and at National road route No.16 for level structure. National road route No.296 was selected as control site. Acid soluble metal contents in the soil were analyzed by an atomic spectrophotometer.
Results of studies are as follows:
1) Metal content in the roadside decreased with distance from the roadside or noise barrier. Metals content within the area 7 to 16 m from the roadedge or noise barriar indicated zinc, lead, copper and acid soluble iron in the roadside of level road structure were higher than those of near tunnel, semi underground, canal, viaduct, bank and cut road structure. The highest concentration of manganese and acid soluble calcium were measured at the cut and bank road structure, respectively.
2) Roadside trees planting influenced metals content of soil. We found that lead content in the soil with roadside trees planting was higher than that in the open field. However, zinc and acid soluble calcium content were higher in the open field. Zinc and acid soluble calcium content in the soil with trees planting decreased drastically with distance than that in the open field. In the planting area, calcium content decreased charply at the point of 3 m from roadside, and after that no reduction was observed.
3) Zinc, lead and acid soluble calcium contents in the soil may be influenced by the particulate that originated from the road. On the other hand, marked variation in the copper, manganese and acid soluble iron content were not observed. Therefore their variation may be due to difference in the soil characters of investigated road.
4) The extent of dispersion and deposition of particulate near road were influenced by the factors such as road structures, the presence of roadside planting and with direction. To clarify their effect more studies are necessary.

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To evaluate the deposition of air pollutants, several sampling sites were selected in a forest (forest top; about 310 m above sea level) in the southern part of Fukuoka Prefecture. The tops of the cedar trees observed on the western slope (about 100 m above sea level) of this forest are dying. Thin films such as nitron film, carbon film (after treatment with BaCl2), carbon film (after treatment with AgNO₃) and copper thin film, which were all prepared on a mesh for a transmittance electron microscope, and coppercoated glass plates were exposed for whole days at the sites at 40 m, 180 m and 230 m elevations in the forest. Fnvironmental air was sucked through filters for each full day at the forest site 230 m above sea level.
The copper film exposed at the upper site was corroded severely only by particulate NO₃-deposition. Strong corrosion pits on the thin films were observed with transmission electron microscope. Particulate NO₃-was also deposited on thin films exposed at the base of the forest. The corrosion on copper-coated glass plates was weak. The deposition of NO₃-was mainly observed on a clear day both at the upper area and the base of the forest. Similar deposition and corrosion phenomena were observed at a nearby forest (forest top; about 920 m above sea level). The concentrations of gaseous NH₃ at the forest top were substantially lower than those at ground level.
Therefore, it was concluded that the chemical from of nitrate particles deposited on the upper area of the forest was different from those deposited at the base of the forest. The nitrate particles deposited on the upper area were mainly in the form of particulate HNO₃. On the other hand, the nitrate particles deposited at the base of the forest were largely neutral particles such as NH₄NO₃ and/or NaNO₃. These phenomena were observed in forests at both 310 m and 920 m above sea level.

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Effects of simulated acid rain on the dry weight growth and gas exchange rate of two-year-old Japanese cedar (Crypotomeria japonica D. Don), six-year-old Nikko fir (Abies homolepis Siebold et Zuccarini) and one-vear-0ld Japanese white birch (Betula platyphylla Sukatchev var. japonica (Miq.) Hara) seedlings were investigated. The seedlings were exposed to simulated acid rain (5: 2: 3 equivalent mixture of sulfate, nitrate and chloride) of pH 2.0, 3.0, 4.0 or deionized water (control, pH 5.6) three times per wee for 20 weeks (from April 26 to September 12, 1993).
The red-brown visible foliar injuries were observed in seedlings of all species exposed to the rain of pH 2.0. and Nikko fir and Japanese white birch seedlings defoliated. Three species examined in this report did not show any visible foliar injury symptoms at pH 3.0 or higher. At the final sampling (September 12), the total dry weights of Japanese cedar and white birch seedlings exposed to the rain of pH 2.0 significantly reduced compared with the control. Those of fir seedlings at pH 3.0 or lower were significantly less than those of the control. The relative growth rate (RGR) and net assimilation rate (NAR) of cedar and birch seedlings at pH 2.0 were lower than those at pH 3.0 or higher. Those of fir seedlings decreased with lowering the rain pH. The dark respiration rates of current-year leaves in all species at pH 2.0 were higher than those of the control. At 20 weeks after starting the exposure, the net photosynthetic rate of birch leaves at pH 2.0 was significantly less than that at pH 3.0 or higher.
These results suggested that Nikko fir is more sensitive to acid rain than Japanese cedar and white birch in tems of the growth inhibition.

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Three-year old cutting seedlings of Japanese cedar (Sugi: Cryptomeria japonica D. Don), Japanese cryress (Hinoki: Chama, ecvbaris obtusa Sieb. et Zucc.) and Sawara cypress (Sawara: Chamaecyparis pisifera Sieb. et Zucc.) grown in Dots with andosol were exposed to simulated acid rain (SAR) for 23 months. The stock solution of SAR was a mixture of sulfuric, nitric and chloric acids at equivalent ratio of 5: 2: 3 in this order. This solution was volumetrically diluted to pH 2.0, 3.0, and 4.0 by deionized water of pH 5.6 which also used as a control.
Half of Dots were fertilized at a rate of 80-80-80 kg/ha/yr of N-P₂O₅-K₂O, and others were not fertilized. The amount of total pecipitation from April to September as a growing season were 720, 1440, or 2160 mm. Exposure rate of SAR during a growing season was 2.5 mm/hr, 10-30 mm/event, 3 times/week, and 5-10 mm/ week during a dormant season. Whole treatment design was 4 pH levels×2 fertilizer levels×3 precipitation levels.
Independent of the fertilizer or precipitation level, exposure to SAR at pH 2.0 induced visible injuries: reddish-brown necrosis in leaves of all conifer seedlings investigated and defoliation in Hinoki and Sawara. However, Sugi did not show any defoliation at pH 2.0, and none of the conifer seedlings showed visible symptoms at pH 3.0 or higher.
Plant height, stem diameter and total dry weight of three conifer seedlings growth in potted andosol supplied with fertilizer were greater than those of plants grown without fertilizer. Such nutrient condition modified growth responses to the exposure to SAR. Seedlings of all these conifers supplied with fertilizer reduced total dry weights after their exposure to SAR at pH 2.0. However, Sugi without fertilizer increased dry weights even though they developed reddish brown necrosis in large Darts of tons at pH 2.0. Increase in total amount of precipitation during the growing season increased growth reduction at pH 2.0, while any growth reduction did not occur in any conifer seedlings after 23 months exposure to SAR at pH 3.0 and 4.0.
Susceutibility to extremely low pH of acidic rain in Sawara and Hinoki was greater than that in Sugi, based on the reduction in total dry weight of plants exposed to SAR at pH 2.0 compared to that of plants exposed to pH 5.6. Increased acidity of precipitation associated with increased input of S and N may accelerate plant growth in the asymptomatic range of pH.

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Total of 364 one-year-old leaf samples of Japanese cedar (Cryptomeria jatonica D. Don) were collected from 123 sites of 9 suburban areas in the nationwide field survey. Contents of 21 elements (K, Ca, Mg, Na, P, S, Mn, Fe, Zn, Cu, B, Mo, Al, Be, Cd, Co, Cr, Ni, Pb, Sr and V) were simultaneously determined with an inductively coupled plasma atomic emission spectroscopy (ICP-AES). Characteristics in the contents of foliar nutrient elements in declined trees, their causes have not been identified, were discussed.
Samples were collected from 4 healthy and 5 declined areas contaning healthy to severely damaged sites. Elernental contents of the 233 samples collected from healthy trees in all areas did not show any characteris-tic differences between healthy and declined areas.
Trees were classified into four declined stages based on the degree of needle losses: healthy or normal appearance, slightly damaged, moderately or severely damaged. Foliar contents of P, S and Ni in specimens collected from damaged trees were greater than those in healthy ones. Contents of Al and Fe in declined trees were likely to be greater than those in healthy ones. However, contents of K, Ca and Mg in leaves from declined trees did not show any significant reduction. These results indicated that the leaves of declined Japanese cedar did not show the foliar nutrient imbalance as observed in plants under soil acidification stresses.

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