兰州某钢厂周边土壤中磁化率积累速率研究

为了寻找一种简便快捷的积累速率的研究方法,通过对兰州某钢厂近地表土壤进行高密度分层采样和磁化率测量,发现各土层磁化率值随着采样深度的逐渐增加而迅速减小,并且这种关系可以用可靠度很高的方程式来定量描述.在此基础上,通过对该方程式积分处理,计算了土层中磁化率的新增积累量,然后结合钢厂的排污年限计算了磁化率在各土层中的积累速率.结果表明磁化率值在1cm以上的土层中富集程度较高,约占整个土层新增磁化率总积累量的70.24%~97.56%;1cm深度以下土层中磁化率值的变化幅度较小;各采样点新增磁化率总积累速率分别为6.5472×10-8m3/(kg·a),40.4178×10-8m3/(kg·a),49.7683×10-8m3/(kg·a),31.8679×10-8m3/(kg·a),且地表1cm以上土层的积累速率最大,向下直至5cm迅速变小.同时发现下风向的积累速率约为上风向的4.87~7.60倍.因此,利用土层磁化率值纵向变化规律来计算积累速率的方法是可行、可信的,可以反映土壤中重金属的动态积累过程.

Magnetic susceptibility accumulation rates in soils near a steel smelter in Lanzhou

In order to establish an easy and fast method to investigate the accumulation rate of heavy metals in soil, samples were collected from the soils on 4sections adjacent a steel smelter near Lanzhou city and their magnetic susceptibility were measured. The data show that the magnetic susceptibilities fast decrease on the section downward. This variation trend can be formulated by a high reliability equation. Using the equation after integrating processing, the newly increased accumulation mass of magnetic susceptibility of soils for each section were calculated. Then the accumulation rate of magnetic susceptibility for each soil layer of the section was calculated according to the running time of the steel smelter. The result shows that the magnetic mineral mainly concentrated in the topmost 1cm soil layer, which accounts for about 70.24%~97.56% of the newly increased accumulation mass of magnetic susceptibility in soil. The magnetic susceptibilities of the soils below 1cm on the section are slightly various. The newly increased accumulation rate of magnetic susceptibility for 4sections are respectively 6.5472×10-8m3/(kg·a), 40.4178×10-8m3/(kg·a), 49.7683× 10-8m3/(kg·a) and 31.8679×10-8m3/(kg·a). The value is maximum in the topsoil above 1cm depth, and it decreases fast down to the 5cm depth on each section. In horizontal, the accumulation rate of magnetic susceptibility of soils in the downwind area is as 4.87 to 7.60 times as that in the upwind area. Therefore, it is feasible and reliable to obtain the newly increased accumulation rate of soil using the variation trend of magnetic susceptibility on the section. This method can reflect the continuous accumulation process of the heavy metals in the soils.