| A total of 23 deposits samples were collected from 8 selected the river sediments in Lanzhou urban area as researching objects of magnetic property and organic matter measure. The results indicate that: ①the magnetic property controlled by magnetite which is ferrimagnetic mineral, and anti-ferromagnetic component such as hematite and goethite; ② the value of samples’ magnetic parameters (such as: χ, SIRM, magnetic hysteresis loops and M-T curves) increased from upstream to downstream in Paihong River, Shier River and Yuer River, Shuimo River; decreased in Qili River and Lanni River; and contrasting above-mentioned, the value of samples’ magnetic parameters were low in Luoguo River and Dasha River. Based on the variation of magnetic parameters, such as χFD , χARM, χFD /MS and χARM/MS, we divided the rivers into three groups according to the contribution originating from anthropogenic activities into spatial river sediments: first type, such as Paihong River, Shier River, Yuer River and Shuimo River, called downstream concentrate type; second type, such as Qili River and Lanni River, called upstream concentrate type; third type, such as Luoguo River and Dasha River, called less affected type. Bulk samples also demonstrate a strong linear positive correlation between magnetic parameters χFD , χ and the content of organic matter, which reflected the content of superparamagnetic and single domain grains were nice proxy parameters of the content of organic matter of river sediments. |
