城市降尘磁性特征对比及其环境意义

Magnetic properties of urban dustfall and its environmental implications

城市降尘中亚铁磁性矿物的浓度较高,且以MD颗粒的磁铁矿为主,反铁磁性矿物和顺磁性矿物浓度低.花岗岩中亚铁磁性矿物(MD颗粒的磁铁矿)和反铁磁性矿物的浓度高,顺磁性颗粒浓度低.黄土中磁性矿物包括磁铁矿、磁赤铁矿和赤铁矿,且浓度低,顺磁性矿物浓度相对较高.古土壤中磁性矿物浓度稍高于黄土样品,晶体粒径细,SP颗粒含量高.研究表明城市降尘具有独特的磁学特征,环境磁学可以通过磁性矿物浓度、种类以及磁晶粒度定性和半定量地指示城市降尘污染.

Dustfall contains high concentrations of ferrimagnetic fraction,most of which are of MD-grained magnetite,and low concentrations of antiferromagnetic and paramagnetic fraction.Granite also contains a high concentration of ferrimagnetic（MD-grained magnetite） and antiferromagnetic（hematite） fraction,and a low concentration of paramagnetic fraction.Loess contains a low concentration of magnetic fraction which includes magnetite,maghemite and hematite,and a higher concentration of paramagnetic fraction.Paleosol contains the same magnetic mineral component with loess and a higher concentration of magnetic fraction than it.The grain size of paleosol is obviously finer than other kinds of samples.What is more,our study indicates that dustfall in urban areas possesses unique magnetic properties and that environmental magnetic technology could be one of the effective instruments in monitoring its pollution degree.