闽江下游及河口表层沉积物磁化率特征及其环境意义  

Characters of magnetic susceptibility of surface sediments and their significance in the lower reach and estuary of Minjiang River

作　　者：朱旭旭[1] 高爱国[1] 汪卫国[2] 倪冠韬 侯昱廷 龚松柏[1] 张延颇[1] 

机构地区：[1]厦门大学海洋与地球学院,福建厦门361102 [2]国家海洋局第三海洋研究所,福建厦门361005

出　　处：《应用海洋学学报》2016年第3期364-370,共7页Journal of Applied Oceanography

基　　金：国家自然科学基金资助项目(41076122;40976037;41376050)

摘　　要：闽江是中国东南沿海最大的河流,具有落差大、水动力强等典型的山溪型河流特征.本研究对采自闽江流域的43个表层沉积物样品进行了磁学参数分析,结果显示,低频磁化率(χ_(lf))、高频磁化率(χ_(hf))分别为0.79×10^(-8)~24.97×10^(-8)、0.74×10^(-8)~24.80×10^(-8)m^3/kg,与长江、黄河相比低一个数量级;频率磁化率(χ_(fd))为0.06%~7.20%,大多小于5.00%,沉积物中超顺磁颗粒含量较低.χ_(lf)和χ_(fd)总体呈现从下游到河口增长的趋势,并在北港、南港、闽侯、大樟溪等人口密集区域受到不同程度的人为影响,分析表明研究区磁化率受控于源岩特征、水动力条件、沉积作用和人为活动等因素.在p<0.01时,χ_(lf)与Al2O3、Fe2O3、Na2O、Mg O、Ti O_2、Ca O等氧化物显著正相关,与Si O_2显著负相关,说明其受控于源岩成分.此外,χ_(lf)与Si/Al值显著负相关,与化学风化指数(CIA)正相关,表明磁化率可以作为现代沉积物风化程度的替代指标.χ_(lf)与溶解态As含量、χ_(fd)与溶解态Cd含量均在p<0.05时相关,表明磁学参数可作为指示研究区水体的As和Cd污染的参考指标.Minjiang River is the largest river in South-east coastal area of China and it is,as a mountain river,characteristic of large elevation gradient and strong hydrodynamics.Low frequency magnetic susceptibility （χlf）,high frequency magnetic susceptibility （χhf）and frequency magnetic susceptibility （χfd ）of 5 1 surface sediment samples collected from the Minjiang River were measured with Bartington MS2.The results shows thatχlf ranges from 0.79 ×10^-8 to 24.97 ×10^-8 m^3 ·kg^-1 ,which is an order less than those of the Changjiang River and Huanghe River sediment.Most of the value ofχfd are lower than 5.0%,indicating that the content of superparamagetism particles in surface sediment samples are low.In general,the values ofχlf andχfd progressively increase from low reach to estuary,with significant influence of anthropogenic impact in densely populated areas of the North and the South port,Minhou Country and Dazhangxi Brook.It suggests that magnetic susceptibility is controlled by the source rock differences,hydrodynamics,sedimentation and anthropogenic impact.Magnetic susceptibility can be taken as indicators of source rock differences and weathering intensity,considering its remarkable correlation with major element abundance and ratios of Si/Al （p〈0.01）.χlf and χfd are also positively correlated with As and Cd abundance in water,which it means that χlf and χfd could be used as a simple proxy of As and Cd contamination in water.

关 键 词：海洋地质学 磁化率 重金属污染 环境指示 山溪型河流 闽江 

分 类 号：P736[天文地球—海洋地质]