土壤剖面中粉煤灰垂向迁移的磁响应

Magnetic responses to vertical migration of fly ash in a soil profile

对浙江省安吉县梅溪发电厂粉煤灰贮灰场附近的土壤短剖面进行环境磁学、元素含量及粒度研究.借助模糊聚类分析,分辨出粉煤灰原位堆积、富集、迁移深度及未受污染土壤特征.剖面上部0～14cm为粉煤灰的原位反映,多畴磁铁矿主导了该段样品磁性.其中11～14cm处磁性矿物和金属元素有所富集.14～21cm为粉煤灰在土壤中的迁移深度.迁移段土壤中亚铁磁性矿物及Pb、Zn等金属含量介于底部未污染土壤与上部粉煤灰原位堆积层之间.单畴斜交反铁磁性矿物及来源于上部粉煤灰的多畴磁铁矿共同主导了该段土壤的磁性特征.21cm以下土壤基本未受粉煤灰污染,单畴斜交反铁磁性矿物是其主要磁性矿物.指标聚类分析表明,亚铁磁性矿物主要赋存在粗粉砂中,单畴磁晶粒主要存在于细粉砂中.x、ARM、SIRM与Cu、Mn、Pb、Zn呈显著相关.结合多元统计分析,磁参数可用于追踪、识别粉煤灰在土壤剖面中的垂向迁移.

Five short profiles were investigated nearby a store site for fly ash of the Meixi power plant in Anji, Zhejiang province, China. All the profiles were measured, and almost the same results were got. Profile T361 of 26cm length is presented in this paper as an example. Magnetic measurements and thermomagnetic κ-T curves show that multidomain magnetite from fly ash is a dominant magnetic mineral above 14cm, and antiferromagnetic mineral increases gradually with depth below 12 cm. Geochemical and grain size analyses also show the difference. Fuzzy C-means clustering shows that fly ash sedimentates on the soil surface with depth of 14cm, and accumulates at 11 - 14cm, then migrates into soil from 14 to 21cm. Below 21cm, soil is not polluted. In the migrating part, multidomain magnetite and fine anti-ferromagnetic mineral coexist, and the content of Pb and Zn is lower than the top and higher than the bottom of the profile. Factor clustering reveals a positive correlation between X, ARM, SIRM and concentration ferrimagnetic components are contained in this range of grain of grain from 32 to 63 μm, that is, most of the Strong correlation between X, ARM, SIRM and Cu, Mn, Pb, and Zn also were found. Magnetic measurements can reveal the polluting process of fly ash in soil profiles with help of clustering analysis.