全球地球化学填图——历史发展与今后工作之建议

Global geochemical mapping-Historical development and suggestions of future work

区域性与国家性的地球化学填图已取得进展,如何在可期待的未来以极低密度采样获得周期表内大多数元素在全球的分布,有赖于对填图理念的更新及采样介质、采样部署与采样方法研究的进展。英国Webb等发现在数平方千米至数十平方千米汇水盆地之河口采集水系沉积物样品,其分析结果可大致逼近其上游汇水盆地内土壤中元素之平均值。挪威及中国的研究工作表明在更大河流(其汇水盆地达数百、数千以至数万平方千米)的河口采样,这一规律依旧适用。看来,这种分形规律还可进一步延展至世界上一些汇水盆地达数十万至百万以上平方千米的主要入海河口,但这方面尚需作更多的研究。在这种新的填图理念指导下,提出了为实现全球地球化学填图的短期研究与试点计划和长期全面实现之规划。

Great progress has been made in regional and national geochemical mapping. How to use extremely low-density sampling to obtain a global picture of the distribution of most elements in the periodic table in the expectable future is an important issue for applied geochemists. This will depend on the innovation of the mapping concept and developments of new sample media, sampling layout and sampling methodology. English geochemists found that the analytic results of stream sediment samples taken from estuaries of catchments covering an area of several to several dozen square kilometers approximate the average values of elements in soils in catchments in the upper reaches of the rivers. This finding has been extended by Norwegian and Chinese geochemists who analyzed samples taken from overbank and floodplain sediments at the estuaries of still larger rivers （whose catchments are several hundred, thousand and even a few dozen thousand square kilometers）. Such a new finding is in accordance with the fractal concept, which may be further extended to main estuaries of some catchments with an area up to hundreds of thousands of or over a million square kilometers in the world. However, more research should be carried out. Based on this new mapping concept, a proposal of the project ＂Global Geochemical Mapping and Sediment-Associated Flux of Major World Rivers＂ was advanced.