北海道湖沼堆積物の化学成分  [in Japanese] Chemical composition of lake sediments in Hokkaido  [in Japanese]

北海道の40湖沼の現湖成堆積物を柱状及びエックマンバージで採取し, 主要な元素の水平及び垂直分布を示した。水平分布をみると, 炭素及び窒素は富栄養湖や腐植栄養湖に高い濃度を示し, 逆に, カルデラ湖等の貧栄養湖は低い濃度を示す。富栄養化問題に重要な元素であるリンは浅い富栄養湖と深い貧栄養湖のいづれにも高い濃度を示す。その他の特徴的な元素は, マンガンが深い湖沼で高い濃度を示し, Zn, Cr, Ni, VはBowenの土壌平均値に比較して高い値ではない。柱状試料による各元素の鉛直分布をみると, 湖沼の形態や水理的・化学的・生物的条件の違いに依存し, 堆積パターンが複雑に違う。そのうち, 柱状堆積物中の上層が下層の濃度より高いパターンを示す元素は炭素, 窒素, リン, 鉄及びマンガンに多く, これらの元素は蓄積と化学変化や微生物分解等による続成過程で堆積パターンが決定されたと考えられる。その他の堆積パターンは様々であり, 堆積量が多いことやサンプリング深度が浅いこともあり各元素のバックグランド値まで達していないことが分かった。

Forty sediment cores and Ekman dredge sediments were collected from lakes in Hokkaido. The concentrations of 14 elements (C, N, P, Si, Al, Ti, Ca, Fe, Mn, Zn, Cr, Ni, V and Sr.) in the samples were determined by CHN-corder and X-ray fluorescence analyser. Based on the horizontal and vertical distributions of the concentrations of the elements and the calculation of enrichment factors, the sedimental origin and its diagenesis of the lakes in Hokkaido were evaluated. The main results are summarized as follows: Higher concentrations of elements such as carbon, nitrogen, and total iron of the surface sediments were founded in the shallow lakes located at the coastal area, which are dystrophic states. But the concentrations of carbon and nitogenon the deep lakes were law. In the deep lakes, for example, Lake Panke and Chimikeppu are dominated chemical behavior of which phosphate, iron, and manganese are diffused from the lawer layer sediment to the surficial layer under the reduction state; the enriched iron and manganese in the pore fluids result from diagenetic reactions (largely oxidation of organic matter) which release the ions from the sediment particulate matter. One of the most important authigenic processes in lake sediments involves phosphorus. The mineralization and release processes of organic phosphorus and sorbed phosphorus under oxidation-reduction state can provide regenerated solute phosphate through diffuse from pore fluids. From the mineralogic reactions, this phenomena suggest that regeneration of solute phosphorus from sediment is an important control on the rate which means that sedimentation and mineralization remove phosphorus from the lake water. There were law concentrations of zinc, nichel, chromium and vanadium in the recent sediments as source of these elements is attributed to human activities.