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No.49 (2002/12) >

Title :西表島相良川のマングローブ群落における表層堆積泥の化学性および鉱物性
Title alternative :Chemical and mineralogical properties of surface sediments in the Aira river mangrove swamp of Iriomote Island, Japan
Authors :渡嘉敷, 義浩
金城, 和俊
佐藤, 一紘
Authors alternative :Tokashiki, Yoshihiro
Kinjyo, Kazutoshi
Sato, Kazuhiro
Issue Date :1-Dec-2002
Abstract :マングローブ群落は沿岸部の陸地化にも大きな役割を果たすと考えられる。ここでは,西表島相良川のマングローブ群落を選定し,干潮時におけるマングローブ群落の縁および群落内部の表層堆積泥の化学性および鉱物性に関連する知見を得る目的で行った。表層堆積泥は最表層(0~0.5cm程度)と表層(0~10cm)のいずれも海側,陸地側および両中間地点におけるマングローブ群落の縁および内部付近から採取した。表層堆積泥のpH は約3~6で陸地側ほど低く,ECは海側で若干高く,中間地点で約10~13mS/cmでいずれも海水の影響が示唆された。有機態炭素含量は約1~5%で全炭素含量(約2~6%)の8割程度を占める中間地点で高かった。化学性はいずれも最表層堆積泥で高い傾向を示した。中間地点では粘土やシルトが多く,その傾向は最表層で高い特徴も示した。シルト画分の一次鉱物はいずれの地点も石英が主体を示した。二次鉱物はいずれの地点でもカオリナイトが主体でイライト,バーミキュライトが随伴した。以上のことから,地形要因や潮の干満による影響も加わり,海側に近い中間地点の最表層ほど粘土画分と有機物が堆積して陸地化が進行しやすく,正・負荷電に富む粘土のバーミキュライトや腐植の機能による寄与が示唆された。
It is known that mangrove swamp and forest play an important role in land formation of coastal area. The purposes of this investigation were to study on the chemical and mineralogical properties of materials sedimented on the mudflat area in mangrove swamp around Aira river at Iriomote island. Sediment samples were collected from inside and the edge of three different sites of land, middle and sea sides at 0-0.5cm and 0-10 cm depth levels in mangrove swamp. The results showed that the pH values of surface sediment changed from 3-6 and which were lower in the land side compared to other sides in mangrove swamp. The values of the EC were about 10-13mS/cm in middle side, however, those were higher in the sea side of mangrove swamp due to salt transmission form sea water. Total carbon content in mangrove swamp was about 2-6% and 1-5% of organic carbon occupied in 80% of the total carbon content and it was higher in the middle side. The values of chemical properties were higher in the most surface sedement in mangrove swamp. Both clay and silt content were higher in the most surface sediment in the middle side of mangrove swamp. The primary mineral of the silt fraction was mainly quartz in the surface sediment on either side. The secondary mineral of clay fraction was mainly kaolinite and accompanied by both illite and vermiculite even in either side of the surface sediment. From the above results, both materials of clay fraction and organic matter were highly accumulated in the most surface sediment in the middle side of which was affected by movement of tides and physiographic factor. It was suggested that the land formation highly progress in the middle side, contributing by the function of negatively charge humus and negatively and positively charge vermiculite.
Type Local :紀要論文
ISSN :0370-4246
Publisher :琉球大学農学部
URI :http://hdl.handle.net/20.500.12000/3629
Citation :琉球大学農学部学術報告 = The Science Bulletin of the Faculty of Agriculture. University of the Ryukyus no.49 p.175 -181
Appears in Collections:No.49 (2002/12)

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