益田市の匹見川流域の山崎遺跡の土壌の重金属の地球化学的分析による古代人の活動の復元

島根県の匹見川流域の山崎遺跡において縄文時代早期から後期の土器片が発見された.出土品による年代の推定に基づき遺跡発掘調査の3トレンチにおいて土壌を採取して重金属濃度の測定と人間活動の影響を推定した。68試料の分析値は土壌の起源,堆積物の粒度や人間活動に関連して組成が変化する.しかし,UCC(上部大陸地殻)組成に比較してこれらの試料はCr,Ni,VとScは低い濃度を持ち,珪長質の岩石に由来すると言える.As,Pb,Zn,Cu,Fe2O3とP2O5はUCC組成よりも高く,古代人の生活の場に関連する.北部のトレンチ(NST-1)はこの地域で最も古い定住地であるが重金属濃度は低い.最も重金属濃度が高いのは東部と西部のトレンチの試料であり,ほとんどの出土品を産出した場所である.グロ-1と呼ぶ層においてリンと亜鉛の最高値が得られた.このような地球化学的データと遺跡の証拠から山崎遺跡においては古代人が3500-3000年前に生活して土器を製造していたと考えられ,ここでは調理や加熱そして土器焼成がなされその結果が土壌の元素分布として記録されている.

Recent archaeological excavations at the Yamasaki site, Hikimi River, in Shimane prefecture of SW Japan discovered Earliest to Late Jomon pottery fragments. Based on the ages of the unearthed artifacts, sediment samples were collected from three trenches to examine their geochemical composition in relation to source composition, and to interpret past human activity and heavy metal accumulation. X-ray fluorescence analyses of 68 samples showed different concentrations of elements due to source rock type, sediment grain size fractionation, and past human activity. However, all trenches had low abundances of Cr, Ni, V and Sc relative to UCC, indicating that the sediments at the Yamasaki site were derived from highly felsic source rocks. Contents of As, Pb, Zn, Cu, Fe2O3 and P2O5 were considerably greater than UCC, and are likely to be associated with past human habitation. The northern trench (NST-1) which contained the oldest past human settlement exhibited the lowest abundances of heavy metals. Highest abundances of heavy metals occur in the eastern and western trenches, which also contained the most artifacts. Peak concentrations of phosphate and zinc were detected in the Guro-1 black layer. The geochemical and archaeological evidence indicates that people were living and producing pottery at the Yamasaki site at about 3500-3000 BP. Past human life style, activities such as cooking, heating, and firing pottery, and human wastes were probably significant contributors to the distributions of elements in the soils.