中文摘要：

建立基于土壤磁化率的重金属污染等级标准可为土壤重金属污染评价提供更为简便的磁学方法。采集开封市城市土壤表层样品99个，测定As、Cd、Cr、Cu、Ni、Pb和Zn含量以及低频磁化率（χLF）和高频磁化率（χHF）。采用普通Kriging插值法探讨χLF的空间分布，污染负荷指数（PLI）评价土壤重金属污染程度，并在PLI与χLF相关分析的基础上建立了基于χLF的土壤重金属污染等级标准。结果表明，开封市城市土壤各样点7种重金属的平均PLI为2.53，呈中度污染，Cd是最主要的污染因子。土壤χLF平均值为125.7×10-8m3 kg-1，总体上由东南向西北递减，高值区出现在东南部、老城区北部和陇海铁路沿线附近。各样点土壤重金属PLI与其χLF的回归方程为PLI = 0.011χLF ＋ 0.320（r = 0.663），呈极显著正相关（p 〈 0.01）。用土壤χLF可以评价开封市城市土壤重金属污染程度：当土壤χLF≤62×10-8m3 kg-1时，为无污染；当62×10-8＜χLF≤153×10-8m3 kg-1时，为轻度污染；当153×10-8＜χLF≤244×10-8m3 kg-1时，为中度污染；当χLF＞244×10-8m3 kg-1时，为强度污染。

英文摘要：

The traditional chemical methods, though still commonly used at present, for monitoring heavy metal pollution of soils are both time- and fund-consuming, while magnetic method is simple and inexpensive, and can be used to detect heavy metal pollution of soils nondestructively, with a soil-magnetic-susceptibility based soil heavy metal pollution grading system available. For use of that technology, a total of 99 topsoil （0～15 cm） samples were collected with the grid method in Kaifeng City （China） for analysis of Cr, Cu, Ni and Zn with atomic absorption spectrometry （F-AAS）, Cd and Pb with inductively coupled plasma/mass spectrometry （ICP-MS）, As with atomic fluorescence spectrophotometer （AFS）, and χLF and χHF （low and high frequency magnetic susceptibility） with a MS2 magnetic susceptibility meter made by Bartington Ltd., Britain. The ordinary Kriging interpolation method was used to work out spatial distribution of soil magnetic susceptibility（χLF）in the city. Soil heavy metals pollution was assessed by pollution load index （PLI）. Based on analysis of relationship between PLI and χLF, a soil heavy metal pollution grading system was established. Results show that the concentrations of As, Cd, Cr, Cu, Ni, Pb and Zn in the topsoil of Kaifeng are 6.31, 1.05, 53.11, 36.40, 23.87, 36.71 and 164.03 mg kg -1, respectively, and in line with their contamination factor values （CF）, the heavy metals follow an order of Cd （10.48） ＞ Zn （2.28） ＞ Pb （1.68） ＞ Cu （1.51） ＞ Ni （0.81） ＞ Cr （0.80） ＞ As （0.65）. The average PLI of the 7 heavy metals in the samples is 2.53, indicating that as a whole, the soil is moderately polluted with heavy metals, of which cadmium is the major pollutant. Soil χLF in Kaifeng varies in the range from 39.97×10-8m3 kg-1to 1123×10-8m3 kg-1with an average of 125.7×10-8, while χFD does in the range from 0.61% to 5.94% with an average of 2.82%. The spatial distribution of soil χLF in Kaifeng City has three major characte