Centre for Earth, Ocean and Atmospheric Sciences, University of Hyderabad, Gachibowli, Hyderabad 500 046, India.
Centre for Earth, Ocean and Atmospheric Sciences, University of Hyderabad, Gachibowli, Hyderabad 500 046, India.
Mar Pollut Bull. 2021 Jun;167:112344. doi: 10.1016/j.marpolbul.2021.112344. Epub 2021 Apr 19.
Magnetic signature of the iron-bearing minerals archived in sediments is sensitive to change in environment and therefore, studied to reconstruct the signals linked with environmental processes. In the present work, we have analyzed 11 sediment cores from Vembanad lagoon, southwest coast of India, to estimate the magnetic fluctuations associated with environmental processes. Down-core variation in magnetic susceptibility and anhysteretic, isothermal and saturation isothermal remnant magnetization and S and H-ratios have been interpreted to map the degree and spatial distribution of anthropogenic pollution in and around the lagoon. Downcore variation of magnetic susceptibility of Vembanad lagoon sediments varies from 10 to 100 × 10 m/ kg. The top layers of sediment samples from river mouth regions (Periyar and Muvattupuzha rivers) show higher susceptibility values and incidentally these samples are of coarse sized. The subtle variations in SIRM/χ ratios suggest that there are magnetic grain size differences in the samples. The SIRM and χ relation suggests that dominant magnetic grain size in sediments. The low ARM/χ ratios suggest a relatively higher ferrimagnetic contribution and coarser magnetite grain size. Rock magnetism data reveal that the coarse magnetic grain size is affecting the pollution of Vembanad lagoon. We also analyzed downcore variability of metal concentrations such as Fe, Mn, Cu, Zn, Ni and Cr, and all these metals exhibit higher concentrations in the top layers of the cores. Our study suggests that higher values of magnetic parameters and metal concentrations are due to various anthropogenic sources.
铁矿物在沉积物中的磁性特征对环境变化敏感，因此，研究铁矿物的磁性特征可以重建与环境过程相关的信号。在本研究中，我们分析了来自印度西南海岸 Vembanad 泻湖的 11 个沉积物岩芯，以估计与环境过程相关的磁性波动。通过分析磁化率和非磁滞剩磁、等温剩磁和饱和等温剩磁以及 S 和 H 比的垂向变化，我们可以绘制泻湖及其周围人为污染的程度和空间分布。Vembanad 泻湖沉积物的磁化率变化范围为 10 到 100×10-3 m/kg。河口区（Periyar 和 Muvattupuzha 河）的沉积物样品顶部层具有较高的磁化率值，这些样品碰巧也是粗粒的。SIRM/χ 比值的细微变化表明样品中存在磁性晶粒尺寸差异。SIRM 和 χ 的关系表明，沉积物中主要的磁性晶粒尺寸。低 ARM/χ 比值表明存在相对较高的亚铁磁性贡献和较粗的磁铁矿晶粒尺寸。岩石磁学数据表明，粗粒磁性对 Vembanad 泻湖的污染有影响。我们还分析了铁、锰、铜、锌、镍和铬等金属浓度的垂向变化，所有这些金属在岩芯的顶部层都表现出较高的浓度。我们的研究表明，较高的磁性参数和金属浓度值是由于各种人为来源造成的。
