Background

Environmental magnetism, focusing on ferrimagnetic iron oxides, provides useful additional information on pollution of different environments. Magnetic methods have been applied to studies of atmospheric dust, namely PM10 (particulate matter smaller than 10 µm) in, e.g., industrial or urban areas. Until now, positive correlation was reported between concentration of iron oxides (expressed in terms of either magnetic susceptibility, saturation remanent or saturation induced magnetization) and concentration of PM10 or smaller. Purpose of this study was to verify the relationship between iron oxides and PM at monitoring site close to source of emissions rich in iron oxides during period of smoggy conditions.

Results

We examined 24-h PM10 and PM1 samples, collected during 10 days of smoggy winter period at a site close to steel plant, which represents a significant source of atmospheric emissions in industrial region of Northern Moravia (Czech Republic), known for generally high degree of air pollution. Magnetic hysteresis loops were measured to obtain parameters reflecting the concentration and grain-size distribution of iron oxides. Our data show unexpected negative correlation between saturation magnetization (concentration of ferrimagnetic iron oxides) and both PM1 and PM10 concentrations, to the best of our knowledge the trend not being reported yet.

Conclusions

Our finding may seemingly disqualify magnetic methods as useful proxy in air pollution studies. However, we suggest that this is an exceptional case, specific to this region and monitoring site, as well as to synoptic conditions during the smoggy period. Although the significant dust emissions are presumably rich in iron oxides, the overall air quality at the monitoring site is determined by the general environment, controlled by many other sources of different character in the region, and by the specific climatic conditions. Thus, the steel plant, presumably emitting dust rich in ferrimagnetic iron oxides, dominates the deposited dust at the nearby monitoring site only during few days of suitable weather (namely wind speed and direction).

中文翻译：

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大气尘埃中铁氧化物浓度与颗粒物之间的负相关：以烟雾弥漫时期的工业现场为例

背景

着重于亚铁磁性氧化铁的环境磁性提供了有关不同环境污染的有用的附加信息。磁性方法已被用于研究大气粉尘，例如工业或城市地区的PM10（小于10 µm的颗粒物）。到目前为止，据报道，铁氧化物的浓度（以磁化率，饱和剩磁或饱和感应磁化强度表示）与PM10或更小的浓度之间呈正相关。这项研究的目的是在烟雾弥漫的时期内，在靠近富含氧化铁的排放源的监测地点，验证氧化铁与PM之间的关系。

结果

我们检查了在烟雾弥漫的冬季10天期间在靠近钢铁厂的地点采集的24小时PM10和PM1样品，这代表了北部摩拉维亚（捷克共和国）工业区的大气排放的重要来源，该地区通常以高度空气污染。测量磁滞回线以获得反映氧化铁的浓度和粒度分布的参数。我们的数据显示出饱和磁化强度（亚铁磁性氧化铁的浓度）与PM1和PM10浓度之间的出乎意料的负相关性，据我们所知，目前尚未报道这种趋势。

结论

我们的发现似乎使磁性方法失去了在空气污染研究中的有用代理的资格。但是，我们建议这是例外情况，特定于该区域和监视站点，以及烟雾期间的天气状况。尽管可能产生的大量粉尘排放中富含氧化铁，但监测地点的总体空气质量取决于总体环境，并受该地区许多其他不同特征的来源以及具体气候条件的控制。因此，仅在合适的天气（即风速和风向）的几天内，钢铁厂大概会散发富含亚铁磁性氧化铁的粉尘，才在附近的监测点控制沉积的粉尘。