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Field Investigation Of PAHs In Soils Around Nara City In Japan

PAHs are the general term for compounds, having two or more benzene rings. These are discharged from diesel motor gas, tanker accidents, oil emissions by cars, and so on. They float in the atmosphere, and it is considered that they are absorbed in soil as a result of rain. Generally, compounds that have two and three benzene rings show only toxicity, whereas those having four or more benzene rings show toxicity, carcinogenicity and mutagenicity. Especially, benzo(a)pylene has been shown to be an endocrine disrupter. We investigated the action of 16 PAHs specified by the U.S. EPA in soil around Nara city in Japan. Soil was collected from different locations involving traffic and vegetation. Soils from three locations around our university were collected every month, to investigate seasonal movement. PAHs were extracted from soil by soxhlet extraction with dichloromethane. They were then analyzed quantitatively by HPLC/UV. We classed PAHs by number of rings, and examined the concentration and seasonal movements. All content of 16 PAHs in soils increased in proportion to traffic volume. At the same locations of traffic volume, the gravitation at a location with plant with all content of 16 PAHs in soils was, furthermore, found to have a low concentration. There were different seasonal movements of the 2, 3-ring and 4, 5, 6-ring PAHs. 4, 5, 6-ring PAHs have a strong correlation with each other ( r>0.79), but there were no correlations between 2, 3-ring and 4, 5, 6-ring PAHs. As a result, the traffic volumes are exposition sources of 4, 5, 6-ring PAHs in soils.