Abstract
We have studied the biogenic volatile organic compounds (BVOCs, namely isoprene, α-pinene, β-pinene, δ-3-caren, and limonene) in the ambient air in a small forest (Tokyo Univ. of Agriculture and Technology Field Museum TAMA Hills, Hachioji City), which is located 33 km from Shinjuku. Simultaneous sampling of the BVOCs was performed at three points, namely, at the top of the canopy of Konara (14 m), under the canopy (1 m at the ground), and in the forest clearing (1 m at the ground) on 20-25 June, 2011. Isoprene showed a clear diurnal variation and was high in the daytime and low in the nighttime at the three points. The maximum concentration of isoprene was 11.1 ppbv at the top of the canopy. Monoterpenes such as α-pinene, β-pinene, and limonene did not show any diurnal variation and their concentrations were higher under the canopy and in the forest clearing than those at the top of the canopy. δ-3-Caren was below its detection limit at the three points. A correlation analysis showed that the sources of isoprene were different from those of the monoterpenes, and among the monoterpenes, the sources of the pinenes were different from the sources of limonene. A positively high correlation coefficient between the concentration of α-pinene and β-pinene showed that they were emitted from identical species. The concentration of the BVOCs in the ambient air at FM TAMA was about 10 times higher than at Shinjuku, indicating that Satoyama (the border zone or area between the mountain foothills and arable flat land) is the important source of the BVOCs.
