[Magnetic properties of topsoils in typical industrial belt along the Yellow River in arid regions in northwest China and their environmental significance].

We have carried out environmental magnetic investigation on topsoil samples of two industrial cities Wuhai and Shizuishan along the Yellow River in the arid regions in northwest China. The concentration, type, magnetic grain sizes of the magnetic minerals and the environmental significance were discussed. The results showed that the main magnetic grain sizes were multi-domain (MD) and pseudo single domain (PSD). The concentration and grain sizes of magnetic minerals showed differences in different functional zones. In industrial zone, the concentration was higher and the grain size was coarser, while there were obviously fewer and finer magnetic minerals in agricultural zone and raw coal zone. Environmental magnetic measurements were efficient to monitor pollution caused by burned fossil fuel, but were not sensitive to unburned fuel. X,, SIRM and SOFT were effective indicators to reflect urban soil pollution. Environmental magnetism method was found to be an important way to monitor and evaluate soil pollution in a city.