藏北可可西里地区土壤元素背景值研究

Study on Soil Element Background Values of the Hoh Xil Area in North Tibet

对藏北可可西里的25个表层土壤样品的全样和<20μm粒级样品中的32种元素含量进行了研究,并与藏南雅鲁藏布江沉积物元素含量、西藏土壤元素背景值和中国地壳丰度进行了对比.结果表明,同种元素在<20μm粒级的元素含量普遍高于全样的含量;研究区多种元素含量与西藏土壤背景值接近,而Ca、As的含量远大于全国均值,这主要与当地的高寒干旱气候和广泛分布富含As的母岩有关.对全样元素含量的EOF分析揭示了不同元素的来源及其化学性质的差异:大部分元素如Al、Fe、Ga等保存了该地区母岩的特性,同时易溶于水的化学性质较为活泼的元素(Mg和Sr)和主要存在于重矿物中的元素Zr对总元素的含量和变化也有一定贡献,而且B和Cs等元素显示了热泉对该地区土壤元素含量的影响.

Hoh Xil locates at northern part of the Tibetan Plateau. Twenty five surface soil samples were collected from this area in 2007 and 32 elements were analyzed and compared to the element contents of Yarlung Zangbo river sediment,background element value of the Tibetan surface soil and the Chinese Continental crust contents. The results showed that the element contents of the < 20 μm fraction were higher than those of bulk samples; Contents of many elements of this study were similar to those of the Tibetan soil. Meanwhile,contents of Ca and As of the studied area were higher than those of Chinese continental crust,resulting mainly from local alpine arid climate and widely distributed the rocks that enriched in As,respectively. The EOF analysis of the contents of bulk soil samples revealed the sources and chemical properties of studied elements: many elements such as Al,Fe,Ga inherit the characteristics of the parent rocks of this region. Meanwhile,elements with an active chemical property and the element Zr that specially existed in the heavy minerals also had a certain contribution to the contents. The contents of B and Cs revealed contribution of hot springs to the soil of studied area.