环境磁学及其在西北干旱区环境研究中的问题

环境磁学是一门新兴交叉学科,它介于磁学、地学和环境科学之间,主要利用矿物和岩石磁学技术,研究环境中磁性颗粒的风化、剥蚀、搬运、沉积和转化受环境变化影响的过程,为全球环境变化和气候过程研究提供代用指标,环境磁学技术在各种环境研究中得到了广泛应用。文中在简要介绍环境磁学原理和方法的基础上,就目前环境磁学在土壤、黄土、沉积物和大气尘埃等方面研究状况进行了阶段性总结。环境磁学参数在干旱和半干旱地区黄土气候和环境记录重建研究中取得了重大进展,但仍存在较大争议。黄土地层中经常使用的磁化率其粉尘贡献到底有多大?磁学参数在季风区和西风区表现迥异,原因何在?不同粉尘源区的环境磁学参数是否存在较大差异?哪些磁学参数适用于干旱区气候与环境重建?这些问题既是国际学术界亟待解决的重大科学问题,也是环境磁学应用在干旱半干旱区环境研究中所面临的主要问题。深入研究提供黄土物质的干旱半干旱地区现代环境磁学过程或许对解决上述问题具有重要的启示意义。

Environmental magnetism concepts and their applications to environmental studies in arid regions, Northwest China

Environmental magnetism is a relatively new field of geophysics and a versatile methodology applicable to a wide range of environmental studies and contexts.It is the use of magnetic measurements to identify the nature and concentration of Fe-containing minerals in environmental materials,which is an ideal tool for environmental studies in a variety of environments.This paper aims to provide a comprehensive review of previous studies and concepts concerning environmental magnetism.Significant progress has been made using environmental magnetism,in reconstructing climatic change and environmental records in Chinese loess studies.However,there are still some issues not well understood,e.g.,what is the contribution of dust to the magnetic susceptibility in loess? Why are there significant differences in magnetic parameters for loess from monsoon regions and from the western wind region? Does the dust from different origins have the same magnetic characteristics? Which magnetic parameters are most suitable for the reconstruction of the climatic and environmental history in arid regions? All of the above are important and urgent academic issues in the study of environmental and climatic changes in arid regions.To answer these questions,it is necessary to study the environmental magnetic processes occurred in the vast arid and semi-arid regions that are the origins of Chinese loess.Using magnetic techniques also might resolve these issues in characterizing dust and surface soil deposits from different geomorphologic settings(i.e.sand desert,oasis,Gobi and dry lake)in Northwest China.