南沙群岛海域表层沉积物中有机物、铁和锰的分布特征

DISTRIBUTIONAL CHARACTERISTICS OF ORGANIC MATTER, IRON AND MANGANESE IN SURFACE SEDIMENTS OF NANSHA ISLANDS SEA AREA, SOUTH CHINA SEA

通过1997年11月(冬季)和1999年7月(夏季)两个航次对南沙群岛海域的现场调查,实测了南沙深海盆表层沉积物中的有机物、Fe和Mn的含量,讨论了沉积物中Fe、Mn的平面和深度分布。在沉积物的上层几厘米处Fe和Mn都出现了峰值,这是上层Mn2+(Fe2+)氰化、再沉淀引起的,沉积物中Fe和Mn的深度分布是氧化锰(铁)和氢氧化锰(铁)的还原、扩散和再沉淀的结果。细菌在海洋环境的Fe、Mn循环中起着重要的作用。在大洋底的厌氧环境中细菌将Fe、Mn还原为低价离子或可溶性化合物向间隙水和上覆水移动,在沉积物表层的氧化条件下细菌又使环境中的Fe、Mn沉淀,使其再次富集。

Concentrations of organic matter (OM), iron, manganese in the deep sea surface sediments in the Nansha Islands sea area, South China Sea have been measured. Horizontal and vertical distributions of iron and manganese were discussed. The vertical distributions of iron and manganese in the sediments of the sea area are resulted from reduction, diffusion, and redeposition of manganese (or iron) oxides and hydroxides in sediments. There are maximums of iron and manganese in solid phase in the top sediments, which is caused by the penetration of O2 and the upward flux of Mn2+ (or Fe2+). Manganese bacteria play a very important role on the cycle of solid-phase iron and manganese in ocean environment. Manganese bacteria oxidize Mn2+ (or Fe2+ ) in dissolved state to Mn4+ (or Fe3- ) in indissolved state under aerobic condition, whereas they reduce iron and manganese in anaerobic conditions.