Low-density geochemical mapping in Portugal

This paper reports the first results of a low-density geochemical survey co vering the whole continental area of Portugal, taking both topsoils and act ive stream sediments as the sampling media. The data were obtained in a con sistent way from 653 sites at a sampling density of 1 site/135 km(2). The s amples were analysed for 31 elements by ICP-AES and after quality control t he following 19 were selected: Al, As, Pa, Ca, Co, Cr, Cu, Fe, K, La, ME, M n, Ni. PI Pb, Sr, Th, V and Zn. The baseline levels for these elements are presented. The first geochemical maps of Portugal were prepared and the geo chemical patterns are generally well correlated to geological factors somet imes combined with anthropogenic influences. Some general trends can be obs erved between geochemical patterns and soils distribution. (C) 2001 Elsevie r Science Ltd. All rights reserved.