Distribution of magnetic susceptibility of surface dust in Xining City and its indicative significance to heavy metal pollution

Abstract

The establishment of heavy metal pollution grade standards based on the magnetic susceptibility of surface dust can provide a simpler magnetic method for the evaluation of heavy metal pollution of surface dust. A total of 251 urban soil surface samples were collected in Xining City, and As, Cd, Cr, Cu, Ni, and Pb were determined V and Zn contents, as well as low-frequency magnetic susceptibility (χLF) and high-frequency magnetic susceptibility (χHF). The common Kriging interpolation method was used to explore the spatial distribution of χLF, and the pollution load index (PLI) was used to evaluate the degree of soil heavy metal pollution, and the correlation analysis between PLI and χLF was established。 The results showed that the average PLI of the seven heavy metals in the urban soil samples of Xining City was 2 34. Moderate pollution, Zn is the most important pollution factor. The average value of soil χLF was 125. 7 × 10-8m3 kg-1, which decreased from “northwest-southeast”, and the high-value area appeared in the northwest near Xining Special Steel along the line. The regression equation between soil heavy metal PLI and χLF was y=3.36E-06x2+0.01x+0.9092, showing a significant positive correlation (p<0.01). The χLF of surface dust can be used to evaluate the degree of heavy metal pollution of surface dust in Xining City: when the χLF of surface dust is ≤66.05 × 10-8m3 kg-1, it is pollution-free; When 66.05 × 10-8m3 kg-1<χLF≤437.332 × 10-8m3 kg-1, it is slightly polluted. When 437.332 × 10-8m3 kg-1<χLF≤652.02 × 10-8m3 kg-1, it is moderately polluted. When χLF > 652.02 × 10-8m3 kg-1, it is an intensity pollution.