Effects of pH and salinity on the intensity of magnetization in redeposited sediments
Effects of pH and salinity on the intensity of magnetization in redeposited sediments
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DOI：
10.1016/s0012-821x(00)00226-0
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发表时间：
2000-09
影响因子：
5.3
通讯作者：
Kaushik Katari;L. Tauxe
中科院分区：
文献类型：
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作者：
Kaushik Katari;L. Tauxe
再沉积沉积物的磁化强度测量作为沉积物-水混合物的盐度和pH值的函数。在高盐度或低pH值下，絮凝强度相对较低。在这些条件下，颗粒间的键被增强，从而导致形成较大的絮体。铁磁性矿物（我们沉积物中的磁铁矿）被结合在主要由非磁性矿物组成的絮凝物中，并且沿着施加的场的取向受到与絮凝物直径的三次方成比例的阻力的抵抗。在较低的盐度和较高的pH值下，当颗粒间力较弱且絮体尺寸较小时，记录到较高的强度。磁化强度随pH值的增加在pH值约为5时停止，这是伊利石（沉积物中主要的非磁性矿物）边缘的PZC。在此pH值以上，伊利石颗粒的边缘和表面都是负的，并且存在净排斥，这阻碍了絮凝。因此，粘土颗粒之间的相互作用比磁铁矿和粘土之间的相互作用对磁化强度有更大的影响。这表明磁铁矿总是包含在粘土磁铁矿域中，并且该域是被磁场重新定向的最小单元。
The intensity of magnetization in redeposited sediments was measured as a function of salinity and pH of the sediment–water mixture. The intensity was relatively low at high salinity or low pH. Under these conditions, inter-particle bonds are enhanced, which lead to the formation of larger flocs. Ferromagnetic minerals (magnetite in our sediment) are incorporated in the flocs consisting mainly of non-magnetic minerals, and orientation along an applied field is resisted by the drag proportional to the third power of the diameter of the floc. Higher intensity is recorded at lower salinity and higher pH, when inter-particle forces are weaker, and floc sizes are smaller. The increase of magnetization as a function of pH stops at a pH of about 5, which is the PZC of the edge of illite (the dominant non-magnetic mineral in our sediment). Above this pH, both the edge and face of the illite grains are negative, and there is net repulsion, which retards flocculation. The interactions between clay particles therefore have a larger effect on the intensity of magnetization than interactions between magnetite and clay. This suggests that magnetite is always included in a clay-magnetite domain, and this domain is the smallest unit that is reoriented by a magnetic field.