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125.7×10-8m3kg-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≤62×10-8m3kg-1时,为无污染;当62×10-8<χLF≤153×10-8m3kg-1时,为轻度污染;当153×10-8<χLF≤244×10-8m3kg-1时,为中度污染;当χLF>244×10-8m3kg-1时,为强度污染。
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 characteristics, i.e. 1） Soil χLF displays a declining gradient from southeast to northwest; 2）, A fairly large tract of the northern part of the old city district （within the ancient city walls）; and 3） A few fairly high peaks of soil χLF appear alongside the Longhai Railway and are mainly distributed in the vicinity of the railway station and the east and west freight stations. Moreover, the contents of As, Cd, Cr, Cu, Ni, Pb and Zn in the soils and PLI are significantly and positively correlated with soil χLF, and the heavy metals display an order of Zn 〉 Cu 〉 Cd 〉 Pb 〉 As 〉 Cr 〉 Ni in terms of degree of the correlation, but contents of the heavy metals are negatively or poorly related with χFD, suggesting that the pollutants in the soils of Kaifeng City are closely related to all sorts of human activities. Dust from industrial production processes, exhaust from running vehicles, abrasion of aged pavement and stacks of solid waste, all are sources of large volumes of magnetic particular pollutants, which ultimately settle down into the soil with atmospheric precipitation or surface runoff, thus not only causing rise of heavy metals contents in the soil, but also enhancing magnetism of the soil. A significant positive relationship （R2 = 0.814, p＜0.01） is observed between PLI and χLF, which suggests that soil χLF can be used to grade or evaluation soil heavy metal pollution in the city, and a regression equation, PLI = 0.011χLF ＋ 0.320 （r = 0.663）, is developed between the two parameters. When soil χLF is ≤62×10-8m3 kg-1, it means that the soil is not polluted; when soil χLF is 62×10-8＜χLF≤153×10-8m3 kg-1, it means the soil is slightly polluted; and when soil χLF is 153×10-8＜χLF≤244×10-8m3 kg-1, it means the soil is moderately polluted; and when soil χLF is＞244×10-8m3 kg-1, it means the soil is highly polluted. It should be noted that the grading is tentative and further studies should be done on its universality.
出处
《土壤学报》
CAS
CSCD
北大核心
2014年第6期1242-1250,共9页
Acta Pedologica Sinica
基金
国家自然科学基金项目(41171409
41201211
41301336)
教育部人文社会科学重点研究基地重大项目(12JJD790023)
教育部和河南省共建河南大学项目(SBGJ090101)共同资助
关键词
城市土壤
磁化率
重金属
空间分布
污染程度分级
Urban soils
Magnetic susceptibility
Heavy metals
Spatial distribution
Pollution grading
