Experiences from 30 years of low density geochemical mapping at the subcontinental to continental scale in Europe

Experiences with 30 years of geochemical mapping at the (sub)continental scale in Europe using a wide range of different sample media are reviewed and discussed with a focus on the most recent GEMAS (GEochemical Mapping of Agricultural Soils) project. Comparing results from the different surveys it is possible to come to conclusions how geochemical surveys at the continental scale could best be designed. High analytical quality and as low detection limits as possible are key requirements. In Europe good experiences were achieved with the <2 mm fraction of soil samples and aqua regia extraction. Focus should rather be on high quality of sampling and analyses and more determined parameters than on more samples. The sample density of 1 site/2500 km 2 provides a good overview of the processes governing geochemistry at the continental scale. Results should be extensively published by the project team to get the dataset known and utilized by the wider scientific community. Thematic collection: This article is part of the Continental-scale geochemical mapping collection available at: https://www.lyellcollection.org/topic/collections/continental-scale-geochemical-mapping