調査報告
東京都多摩地域地下水中のメチル-tert-ブチルエーテルの調査
2004 年 27 巻 4 号 p. 267-272
詳細
2004 年 27 巻 4 号 p. 267-272
An analytical method for methyl tertiary butyl ether (MTBE), which is added to gasoline as an oxygenate, by purge and trap gas chromatography - mass spectrometry was tested. The standard method for volatile organic chemicals (23 VOCs), which is used for determining the Japanese drinking-water criteria, was used for its analysis. The quantitative limit for MTBE by the selective ion monitoring mode was 0.01 μg·l-1, and the coefficient of variation at 0.01 μg·l-1 was 9.2 %. The recovery of spiked groundwater (0.01 μg·l-1) was 101±8.6 %. We found that it was possible to determine MTBE and the 23 VOCs simultaneously by this method. MTBE in groundwater was investigated in 246 wells at the Tama district in Tokyo. MTBE was detected from 26.5% of shallow wells and 19.7% of deep wells. The detected concentrations ranged from 0.01-47.7 μg·l-1, and the medians of the MTBE detected were 0.04 μg·l-1 (shallow wells) and 0.03 μg·l-1 (deep wells). We then periodically monitored samples from two wells where high levels of MTBE were detected. The MTBE concentrations of these groundwaters decreased to less than 1μg·l-1 after 6-12 months. This suggests that groundwater pollution by MTBE disappears rapidly.
