呼和浩特市大气降尘磁学特征及其环境意义

应用环境磁学方法研究了呼和浩特市及其对照点大气降尘样品的环境磁学特征,同时与西北地区两大典型污染城市—乌鲁木齐、兰州进行对比,探讨了环境磁学在大气污染监测和来源解析方面的应用.结果表明,两地样品磁学特征均受磁铁矿控制,磁性矿物为假单畴和多畴颗粒;与对照点相比,呼和浩特样品磁性矿物的含量较高,颗粒较细.通过降尘污染的季节变化对比可知,呼和浩特大气污染受到自然因素和人类活动的共同影响.相对于磁化率(χlf)而言,饱和等温剩磁(SIRM)能更好地反映呼和浩特大气污染状况,可作为大气降尘磁性特征的有效指示器.与乌鲁木齐和兰州相比,呼和浩特逆温强度较大,但大气污染程度相对较低,暗示人类活动对大气污染起到主导作用.

Magnetic properties of dustfall in Hohhot and their environmental implications

Environmental magnetic properties of dustfall samples collected monthly or bimonthly during 2010.10-2011.10 in Hohhot were measured and compared to samples from a background site-Helingeer. The use of environmental magnetism as a tool for atmosphere pollution monitoring and pollution source identification were discussed by comparing the magnetic properties of dustfall samples in Hohhot to two typical polluted cities in Northwestern China, i.e. Urumqi and Lanzhou. The main magnetic mineral in samples from Hohhot and its background was magnetite, and the main magnetic grain sizes were multi-domain (MD) and pseudo single domain (PSD). The concentration of magnetic mineral was higher and the grain size was finer in dustfall samples from Hohhot than that from Helingeer. The seasonal changes of magnetic properties in dustfall samples from Hohhot indicated that the atmosphere pollution was affected by both natural factors and human activities. Compared to χlf , SIRM could better reflect atmosphere pollution in Hohhot. Compared to Urumqi and Lanzhou, the intensity of inversion was higher in Hohhot, but the atmosphere pollution was less serious, suggesting human activities played a primary role in atmosphere pollution.