离心法在海洋碎屑沉积物粒度分级中的应用
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摘要
沉积物的粒度特征受控于沉积环境的变化,是沉积学研究中的重要物理指标之一。沉积物中不同粒级的颗粒物记载了详细的物源信息及水动力活动等特征,因此,有效并快速地分离不同粒级的沉积物对古环境演化研究十分重要。沉降法是沉积物粒度分级最基本的方法,然而用沉降法对细颗粒物质含量较多的海洋沉积物进行粒度分级时,耗时久,分离效率低。离心法可以加速细颗粒物质的沉降速度,提高分离效率。因此,选择离心法对东海内陆架泥质沉积区的27个表层沉积物进行粒度分级(<2μm,2～10μm,10～63μm,>63μm)。显微镜观察结果显示不同粒级的颗粒间基本没有混染,表明离心法的分离效果较好。样品回收率在94%左右,最高可达97%以上。样品的损失量与细颗粒含量呈正相关,即细颗粒含量越多,损失量越大。与激光粒度仪测试结果对比发现,激光粒度仪对<10μm颗粒物区分度较差,低估<2μm颗粒物含量,高估2～10μm颗粒物含量。本研究表明离心法可以高效地对海洋沉积物进行粒度分级。
The grain size of sediments,as a result of complex geological processes of weathering,transportation and deposition,is one of the most important physical indicators in sedimentological study.The size of sediment particles may document detailed information on both provenance and hydrodynamics.It is very important for paleoenvironmental study to separate sediments into different groups of grains size effectively and rapidly.Pipette method is one of the methods often used by sdedimentologists for this purpose,but for marine sediments,which are usually too fine,this method is not satisfactory enough due to its time-consuming process,much loss and low separation efficiency.Centrifugation can accelerate the settling velocity of fine particles and increase the separation efficiency.Therefore,27 surface sediments collected from the mud area along the inner continental shelf of the East China Sea is separated into four grades(<2μm,2-10μm,10-63μm,>63μm)using the centrifugal method.Microscopic observation of the samples after sizing shows that there is no mixture between different grades,indicating that the separation using the centrifugation was effective and feasible.The average recovery rate for all samples is about 94%,and the highest is over 97%.The loss of each sample is positively correlated with the content of fine particles(<10μm),that is,the more the fine particles contained,the greater the loss.Further comparison with the results from the laser diffraction particle size analyzer is also carried out.It shows that the laser analyzer has a poor discrimination of particles<10μm,underestimating of<2μm particles and overestimating of 2-10μm particles.This study shows that the centrifugation can effectively and rapidly separate fine marine sediments into grain size groups.
The grain size of sediments,as a result of complex geological processes of weathering,transportation and deposition,is one of the most important physical indicators in sedimentological study.The size of sediment particles may document detailed information on both provenance and hydrodynamics.It is very important for paleoenvironmental study to separate sediments into different groups of grains size effectively and rapidly.Pipette method is one of the methods often used by sdedimentologists for this purpose,but for marine sediments,which are usually too fine,this method is not satisfactory enough due to its time-consuming process,much loss and low separation efficiency.Centrifugation can accelerate the settling velocity of fine particles and increase the separation efficiency.Therefore,27 surface sediments collected from the mud area along the inner continental shelf of the East China Sea is separated into four grades(<2μm,2-10μm,10-63μm,>63μm)using the centrifugal method.Microscopic observation of the samples after sizing shows that there is no mixture between different grades,indicating that the separation using the centrifugation was effective and feasible.The average recovery rate for all samples is about 94%,and the highest is over 97%.The loss of each sample is positively correlated with the content of fine particles(<10μm),that is,the more the fine particles contained,the greater the loss.Further comparison with the results from the laser diffraction particle size analyzer is also carried out.It shows that the laser analyzer has a poor discrimination of particles<10μm,underestimating of<2μm particles and overestimating of 2-10μm particles.This study shows that the centrifugation can effectively and rapidly separate fine marine sediments into grain size groups.
引文
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[17]王娟,周晨亮,张跃进.离心法在土壤颗粒分级技术中的应用[J].上海环境科学,2009,28(6):246-249.
[18]武天云,Jeff J S,李凤民,等.利用离心法进行土壤颗粒分级[J].应用生态学报,2004,15(3):477-481.
[19]赵杏媛,张有瑜.黏土矿物与黏土矿物分析[M].北京:海洋出版社,1990.
[20]李维显,荣人德,冯诗齐.长江口海区表层沉积物及其有机质分布特征[J].上海地质,1987(3):40-55.
[21]范典高.黄河口区潮间带沉积物中的有机质[J].中国海洋大学学报:自然科学版,1990,20(1):133-135.
[22]程鹏,高抒,李徐生.激光粒度仪测试结果及其与沉降法、筛析法的比较[J].沉积学报,2001,19(3):449-455.
[23]刘涛,高晓飞.激光粒度仪与沉降—吸管法测定褐土颗粒组成的比较[J].水土保持研究,2012,19(1):16-22.
[2] Johnsson M J,Basu A.Processes controlling the composition of clastic sediment[J].Special Paper of the Geological Society of America,1996,284(3):1-19.
[3]赵一阳.中国海大陆架沉积物地球化学的若干模式[J].地质科学,1983(4):307-314.
[4] Rao W B,Mao C P,Wang Y G,et al.Geochemical constraints on the provenance of surface sediments of radial sand ridges off the Jiangsu coastal zone,East China[J].Marine Geology,2015,359(4):35-49.
[5]赵玉玲,冯秀丽,宋湦,等.现代黄河三角洲附近海域表层沉积物地球化学分区[J].海洋科学,2016,40(9):98-106.
[6]张忆,石学法,王昆山.长江口泥质区表层沉积物元素地球化学[J].海洋地质与第四纪地质,2010,30(3):61-70.
[7]石学法,刘升发,乔淑卿,等.中国东部近海沉积物地球化学:分布特征、控制因素与古气候记录[J].矿物岩石地球化学通报,2015,34(5):885-894.
[8]刘升发,石学法,刘焱光,等.东海内陆架泥质区表层沉积物常量元素地球化学及其地质意义[J].海洋科学进展,2010,28(1):80-86.
[9]杨守业,李从先.长江与黄河沉积物元素组成及地质背景[J].海洋地质与第四纪地质,1999,19(2):19-26.
[10]林宝治.东海陆架及沿岸河口表层沉积物地球化学记录:化学风化及其物源示踪[D].厦门:厦门大学,2015.
[11]韦桃源,陈中原,魏子新,等.长江河口区第四纪沉积物中的地球化学元素分布特征及其古环境意义[J].第四纪研究,2006,26(3):397-405.
[12] Wang Y H,Yu Z G,Li G X,et al.Discrimination in magnetic properties of different-sized sediments from the Changjiang and Huanghe Estuaries of China and its implication for provenance of sediment on the shelf[J].Marine Geology,2009,260(1-4):121-129.
[13] Liu S M,Zhang W G,He Q,et al.Magnetic properties of East China Sea shelf sediments off the Yangtze Estuary:influence of provenance and particle size[J].Geomorphology,2010,119(3):212-220.
[14] Zhang W G,Xing Y,Yu L Z,et al.Distinguishing sediments from the Yangtze and Yellow Rivers,China:a mineral magnetic approach[J].Holocene,2008,18(7):1139-1145.
[15] Li W,Hu Z X,Zhang W G,et al.Influence of provenance and hydrodynamic sorting on the magnetic properties and geochemistry of sediments of the Oujiang River,China[J].Marine Geology,2017,387(2017):1-11.
[16]吕慧捷,何红波,张旭东.土壤颗粒分级过程中超声破碎和离心分离的条件选择[J].土壤通报,2012,43(5):1126-1130.
[17]王娟,周晨亮,张跃进.离心法在土壤颗粒分级技术中的应用[J].上海环境科学,2009,28(6):246-249.
[18]武天云,Jeff J S,李凤民,等.利用离心法进行土壤颗粒分级[J].应用生态学报,2004,15(3):477-481.
[19]赵杏媛,张有瑜.黏土矿物与黏土矿物分析[M].北京:海洋出版社,1990.
[20]李维显,荣人德,冯诗齐.长江口海区表层沉积物及其有机质分布特征[J].上海地质,1987(3):40-55.
[21]范典高.黄河口区潮间带沉积物中的有机质[J].中国海洋大学学报:自然科学版,1990,20(1):133-135.
[22]程鹏,高抒,李徐生.激光粒度仪测试结果及其与沉降法、筛析法的比较[J].沉积学报,2001,19(3):449-455.
[23]刘涛,高晓飞.激光粒度仪与沉降—吸管法测定褐土颗粒组成的比较[J].水土保持研究,2012,19(1):16-22.