广西近岸海域水下平原表层沉积物中有机质分布及其积累

【目的】研究广西近岸水下平原表层沉积物有机质的分布和积累,了解有机质的扩散和现状。【方法】以钦州湾口水下斜坡为界,东至铁山港口外古滨海平原的20m以浅的广西近岸水下平原为研究区,依据2007~2010年广西近岸海洋环境地质调查资料,分析该区海底表层沉积物和钻孔有机质的分布、关系和积累特征。【结果】表层沉积物有机质含量频率f分布不均;研究区可划分出3大类沉积环境和5种亚环境,在其间的有机质分布含量差异较大,对沉积环境的选择性较强;有机质分布与沉积物粒度参数也有较大关系,随着粒径(φ)和分选系数增大而升高,沉积物粒度正偏有利于有机质积聚;有机质随沉积动力减弱而聚集,以平均粒径衡量的话,呈现指数增长规律;在不同的沉积环境有机质序列有指数、线性、对数递增关系,表明不同的积累阶段;随着沉积物粒级变细,在3~6φ粒级段出现有机质吸附积累拐点,而且有机质与粘土有共聚性;在研究区西北部监测站位的有机质具有明显的年际变化,观测期间总体增幅0。【结论】虽然根据沉积物质量评价标准表层有机质尚未超标,但结合本底值计算得出的积累系数显示水下平原西北部、西南部、南部位置均出现富集,对应着不同的来源和影响程度,是陆源输入在水动力分配下聚集的结果。

The Distribution and Accumulation of Organic Matters in Surficial Sediment in Submarine Plain of Guangxi Nearshore Waters

Objective]The distribution and accumulation of organic matters in surficial sedi ment in submarine plain along Guangxi coast was analyzed in order to understand transport and current state of organic matter. Methods]Based on surficial sediments, boreholes sampies and laboratory data in study area of submarine plain in Guangxi coastal ocean, the distribution, relation and accumulation of organic matter were analyzed. Results]The results showed that organic matter was from 0.02 % to 1.51 %. Three types of dynamic sedimentary environments in study area with significant difference in the concentration of organic matter showed the high selectivity of organic matters to environment. There were relation between organic matters and sediment grain parameters. Organic matters showed exponential growth when sedimentary dynamics weakens. Fitness to organic matters concentration alignment demonstrated there were exponential, linear and logarithm trends in different dynamic sedimentary environments. The accumulation or adsorbed/desorbed transition points in grain size series is 3φ-6φ and also showed linear relationship with clay grain sizes. The monitoring stations in northwestern part of study area showed significant annual variation and positive growth.Conclusion] Although the sediment quality of organic matters is the range of national marine sediment standards. The accumulation is relatively significant in some parts of study area compared with the background value.