石英尾砂对旱地表土磁性的影响及其环境意义

对安徽省凤阳县石英尾砂、受尾砂影响的表土、旱地表土和城镇表土进行了磁学测量，结果表明这4类样品的磁性特征明显不同。尽管这4类样品的磁化率均由磁铁矿主导，但旱地表土中可能含少量磁赤铁矿，石英尾砂、受尾砂影响的表土和城镇表土中可能含少量铁的氢氧化物（如纤铁矿），受尾砂影响的表土中还含少量赤铁矿。城镇表土中磁铁矿的含量明显高于其他3类样品，受尾砂影响的表土中的磁铁矿含量介于石英尾砂和旱地表土之间。城镇表土中磁铁矿的粒径范围较宽，小于1 μm，石英尾砂中磁铁矿的粒径大于0.1 μm，旱地表土中磁铁矿的粒径小于0.1 μm，受尾砂影响的表土中磁铁矿的粒径介于旱地表土与石英尾砂的粒径之间。城镇表土的磁化率与频率磁化率呈负相关，旱地表土的磁化率与频率磁化率呈正相关，而受石英尾砂影响的表土的磁化率与频率磁化率没有明显的相关关系。在城市工业和交通等人类活动的影响下，城镇表土的磁性较旱地表土增强。而在石英砂生产这一人类活动的影响下，受尾砂影响的表土的磁性较旱地表土减弱，这是由石英尾砂中磁性矿物的含量较旱地表土4的少所致。

Magnetic Influence of Quartz Tail-sands on the Dry Top Soil and Its Environmental Implications

Magnetic measurements have been undertaken on quartz tail-sands,dry top soil,tail-sands-influenced top soil and town top soil of Fengyang,Anhui.Results show that magnetic properties of the four kinds of samples are evidently different.Although magnetite dominates the susceptibility of the four kinds of samples,there are some maghemites in dry top soil,some iron hydroxides(e.g.lepidocrocite) in quartz tail-sands and town top soil and some iron hydroxides(e.g.lepidocrocite),maghemite in tail-sands-influenced top soil.The content of magnetite in the town top soil is apparently more than that in the other three kinds of samples.The content of magnetite in the tail-sands-influencedtop soil is between that in the quartz tail-sands and dry top soil.Magnetite grains of town top soil is finer than 1μm;those of quartz tail-sands are larger than 0.1μm,and those of dry top soil are smaller than 0.1μm,while those of tail-sands-influenced top soil are between those in the quartz tail-sands and in the dry top soil.Negative correlation lies between the susceptibility and the frequency dependence susceptibility of town top soil,positive correlation lies between those of dry top soil,while no evident correlation lies between those in the tail-sands-influenced top soil.Under the effect of industry processes and traffic,town top soil shows magnetic enhancement.However,the producing of quartz sands results in magnetic reduction of top soil.This is due to less magnetic minerals in quartz sands than that in the dry soil.