广西近岸海域水下平原表层沉积物中重金属分布及其积累

摘要

[Objective]The distribution and accumulation of heavy metals in sediments of near-shore submarine plain along Guangxi coast was studied in order to understand heavy metal transport from estuaries and bays to shallow shelf.[Methods]Based on surficial sediment and core samples from nearshore submarine plain of Guangxi,laboratory test data analyzed main-ly with statistical method showed the distribution and accumulation of heavy metals Pb,As, Hg in sediment.[Results]The results showed that main sediment types are sand and clay sand.Pb is 8.0×10-6~44.7×10-6;As is 1.6×10-6~31.4×10-6;and Hg is 0.001×10-6~0.086× 10-6 .The concentration of heavy metal is affected by environments and types of sedimentary.The high concentration of As in the area with strong hydrodynamic force of submarine plain northern part might be due to the airslaking of mother rock.Pb,As and Hg often show co-occurrence,are correlation with Ni,Zn,Ga,Zr etc.and are poor or negative correlation with Sr.There are linear and cluster relationship between heavy metals and grain pa-rameters,and the transition grain sizes is from~0.125mm to ~0.063mm using LST method. Stations of poor organic matters showed low heavy metals and thus the heavy metals percent-age of organic matter accumulation station var-ied from 40% to 80%.[Conclusion]Although the sediment quality of Pb,As and Hg is still in the range of national marine sediment standards.However,the accumulation is still signifi-cant especially Pb compared with their background values.%【目的】研究广西近岸水下平原沉积物重金属分布和积累特征，促进对重金属自河口海湾向陆架扩散规律的对比与把握。【方法】从广西近岸水下平原采集表层沉积物和岩芯，通过实验测试的手段，分析表层沉积物重金属Pb、As、Hg的分布和积累特征。【结果】广西近岸水下平原表层沉积物中 Pb含量为8．0×10-6～44．7×10-6，As含量为1．6×10-6～31．4×10-6，Hg含量为0．001×10-6～0．086×10-6，变化较大；Pb、As、Hg的分布受沉积环境和沉积物类型影响，As含量在水下平原北部水动力作用强烈之处出现局部高值，与含As的母岩风化有关；Pb、As、Hg有一定的共聚性，并显示亲 Ni、Zn、Ga、Zr和疏 Sr的特征；Pb、As、Hg与粒度参数有线性和聚类关系，对粒级响应性即斜率k的拐点在～0．125mm至～0．063mm之间，视沉积环境和沉积物的不同而有所移动；贫有机质站位由于水动力作用强烈，以自然风化的物理过程为主，重金属含量很低，而有机质积累成因为主的站位重金属含量积累增幅区间的频率，Pb的以40％～60％最高，As和 Hg的均是60％～80％最高，增幅序列均遵循单增自然对数关系，曲线分段对应不同的沉积环境。【结论】广西近岸水下平原表层沉积物质量总体较好，但相对区域本底值来看，Pb积累性比较突出，As次之。