新疆天山天池景区表土磁性特征的时空变化

Temporal and Spatial Variation of Magnetic Properties of Topsoils in Heaven Lake Scenic Spot at Tianshan Mountain of Xinjiang,China

以天山天池5A级景区表土为研究对象,分别于2015年和2017年两次采集表土样品,采用磁测、统计和GIS方法对其磁学特征、时空变异性进行研究。结果表明:表土样品载磁矿物以低矫顽力亚铁磁性矿物(磁铁矿和磁赤铁矿)为主,同时含有一定不完全反铁磁性矿物(赤铁矿和针铁矿),磁性矿物含量适中,磁性矿物粒度主要由假单畴粗颗粒和含量相对较低的超顺磁性细颗粒混合而成;表土样品中磁性矿物特征随时间变化显著,2017年磁性矿物含量、粗颗粒比例高于2015年;从景区表土样品磁性参数空间分布看,两期分布图变化趋势相似,2015年的高值区位于旅游核心景点区域及湖泊南部区域,2017年的高值区由2015年的高值区扩大到环湖区域且在核心景点区域含量增高;除自然因素外,由于研究区远离工业区、城市等污染源,两期磁性矿物含量和粒度产生的时空差异主要是两年的旅游交通活动输入的磁性污染物不断累积引起的。研究发现,监测景区表土磁性参数的时空变化有助于圈定可能污染范围的变化和判别污染物来源。

The topsoil samples were collected in 2015 and 2017 from Heaven Lake 5A Scenic Spot at Tianshan Mountain of Xinjiang,and their magnetic properties,temporal and spatial variation were investigated by the methods of magnetic measurement,statistics and GIS.The results showed that low coercive ferrimagnetic minerals(magnetite and maghemite)were predominated the magnetic materials and included some amount of anti-ferrimagnetic minerals(hematite and goethite),the content of magnetic minerals was moderate and the magnetic mineral size of the two samples was mainly composed of pseudo-domain coarse particles and SP particles with relatively low content.The properties of magnetic minerals in the topsoil samples changed significantly with time,and the content of magnetic materials and the proportion of coarse particles in 2017 samples were higher than those in 2015 ones.As for the spatial distribution of magnetic mineral content in topsoil samples,the changing trends of the distribution maps were similar in the two phases.In 2015,the high value area was located in the core scenic spot area and in the southern part of the Lake,while in 2017,the high value area expanded from the high value area in 2015 to the area around the Lake.Moreover,the content in the core scenic spot area was increased.In addition to natural factors,being far away from pollution sources such as industrial areas and cities,the spatial and temporal differences of magnetic mineral contents and grain sizes between the two phrases were mainly caused by the accumulation of magnetic pollutant particles input by tourism traffic activities in these two years.It was found that monitoring the temporal and spatial changes of the magnetic parameters of the topsoils in the scenic spot is helpful to delineate the possible changes of pollution scope and identify the sources of pollutants.