| Research Abstract |
Discovery of tree trunk bark inclusion as pollution time capsule
The sequence of element concentration (13 elements : Na, Mg, Al, P, K, Ca, Sr, Ti, Mn, Fe, Cu, Zn and Pb) in the bark-cambium-xylem of a coniferous tree, C. japonica was studied in relation to nutritional status and pollution. A high concentration of Pb and Al on the outside of the bark decreased exponentially toward the inside of the bark, and showed high correlations with the other eleven elements, the values reaching a minimum at the boundary between the outer and inner bark. The concentrations of essential bioelements (Mg, K, P, Cu, Zn) increased in the inner bark, and attained maximum values in the cambium layer (e.g. Mg: 2160 ppm, K: 20300 ppm, P: 1800 ppm).
The concentrations of Pb contained in the outer bark were about 40-150 ppm for samples collected from Nikko, 1-2 ppm at Yakushima Island. It was about 0.2 ppm in the bark which was incorporated into a tree trunk (226 y) about 180 years ago. In addition to these data, the concentrations of Pb in the moss (epiphyte) Brotherella henonii discovered in the bark inclusion time capsule about 180 years ago in was about 0.3 ppm. That of B. henonii now living on the surface of C.japonica trunks was about 25 ppm.
These data indicate how clean the environment was about 180 years ago, before the industrial era of East Asia.
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