The Base Catalyzed Decomposition (BCD) process has been applied to contaminated soil in two successive steps: soil treatment including thermal desorption of PCBs with partial dechlor-ination from soil; and dechlorination of the desorbed PCBs after condensation. A continuous pilot scale experimental plant was fabricated to examine the characteristics of BCD process in a soil treatment process. The pilot plant, which consists of a reactor, a pre-treatment equipment, and a post-treatment equipment, can be conveyed on a trailer.
Treatment of soil samples containing 32 to 72 mg-PCBs / kg-soil resulted in a 1 mg / kg or less residual PCBs, accounting for a 99.5% removal of PCB from the soils. PCBs in the sample soil were desorbed with partial dechlorination, and the most of the desorbed PCBs were collected as a condensate. Because PCBs in flue gas mostly existed as mist, a compact ejector was sufficient to collect PCBs in the flue. Throughout the treatment of PCB-contaminated soil by the BCD process, no formation of Dioxins were observed. Applicability of the BCD process to a soil contaminated by PCBs was proved.

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Water samples from the Chao Phraya River, the main river in Thailand, were collected and analyzed during 1988-1995. The Organochlorine pesticides such as HCHs, DDTs, aldrin, dieldrin and chlordanes were determined. Aldrin and dieldrin occured frequently in water samples. The medians of concentrations of pesticides were approximately one order of magnitude higher than total HCHs and DDTs. Levels of aldrin were relatively high in the upstream while levels of DDTs were high in the urban area of Bangkok during 1989-1990. p, p'DDE levels were relatively high in 1992. Relatively high levels of endosulfan sulfate were frequently found in lower part of the river in 1995. The trends of the residue level of pesticides found were fluctuated along the river.

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There is a remarkable tendency for the hydrogen ion concentration in snowmelt water in the early spring to be higher than that in the late spring. Falling fresh snow catches atmospheric acid substances in the atmosphere. The fresh fallen snow on the ground is compressed by repeated dissolution and crystallization and forms icy granular snow. The repetition causes sulfate, nitrate and chloride ions to be concentrated near the surface of the icy granular snow. Some laboratory experiments were performed to examine this concentration phenomenon by the formation of spherical ice crystallized from sulfate-containing water and by dissolution of the formed ice crystals.
On dissolution, the inclusion amount and the distribution of sulfate ions in ice crystals were measured. The distribution of sulfate in the crystals was found to be biased; the sulfate amount near the surface was larger than that around the center, when each crystal was melted from the surface to the center in organic solvent. It was also found that the higher initial concentration of sulfate tended to create a uniform distribution of sulfate.
When the ice crystals were packed in a column (2.0cm inner diameter, 30cm length) and dissolved at room temperature, a higher concentration of sulfate was observed in the first effluent. The concentration ratio was higher than the estimated value at the surface using the organic solvent method. With the dissolution of the natural granular snow, similar results were obtained; higher concentrations of sulfate ions were observed in the first effluent and lower con-centrations in the later effluent.

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A new type of umu test using chemiluminescence detection was developed. This method is made up of measurement of chemiluminescence which is generated from the glucose yielded as a enzyme reaction product of β-galactosidase, after several reaction steps. Salmonella typhimur-ium TA1535/pSK1002 and lactose was used as the tester strain and the substrate to measure β-galactosidase activity as an index of mutagenicity, respectively. This method was as sensitive as the fluorescence assay previously reported, and was also effective for detection of promutagens.

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A new method for the screening test of genotoxicity to volatile and insoluble compounds such as halon replacements using mammalian cell culture was developed. The method was composed of two systems; a gas handling system producing sample gas of a particular concentration from original material in a Tedlor bag, and a gas exposure system on the cells in a glass culture bottle by incubation for one day. A positive control, Bromochloromethane, exposed by this gas exposure system induced sister-chromatid exchanges (SCEs) as a dose depended manner within concentrations of 0.5-2.0%. Among 8 halon-related compounds tested by the system, 7 samples did not induce significant levels of SCEs while Halon 1301 alone gave weakly positive result, i.e., apporoximately twice of the control SCEs. It was suggested that this gas exposure system could use as a screening test for genotoxicity using mammalian cell culture of volatile and insoluble compounds such as halon replacements.

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Two kinds of surface soils were sampled at Shapotou in Tengger Desert and Yanchi Shabianzi in Maowusu Desert, two well known areas as origin of sand storm, in order to prepare a typical artificial kosa aerosol. Those original desert soils were separated, by sieving, to three different particle sizes (>100, 100-50, and< 50μm) . The artificial kosa aerosol with particle size around 10μm was successfully separated from particle fraction of < 50μm by wind-driven mode tunnel system. The amount of the two artificial kosa aerosol samples thus prepared were about 2kg each from 250kg (Shapotou) and 150kg (Yanchi Shabianzi) of original desert surface soils with less than 100 μm in particle size. The minerals in artificial kosa aerosol were compared with those in natural ones collected at Lanzhou and in Japan by X-ray diffraction analysis. The artificial samples prepared were found to be very similar to Lanzhou sample rather than Japanese one. The size distributions of these artificial kosa aerosol samples were confirmed similar to a natural sample that was collected at Lanzhou in May 1993 when a strong sand storm occurred.

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A list of hazardous air pollutants has been newly assigned for emission regulation in amended ordinance of Osaka Prefectural Government.
Measurement methods for listed pollutants in exhaust/flue gas have been developed/selected for the implementation of amended ordinance. Round robin tests for methods evaluation have been performed among many laboratories in Osaka. Most of the methods showed good recovery (higher than 80%) and precision (better than 20%) . After some revision/improvement, methods have been established, and manuals have been prepared.

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