FUTURE-TRENDS, DETECTABLE BY SOIL MONITORING NETWORKS

Recently some networks for monitoring the soil quality have enriched t he world of environmental quality assessment. Formerly such networks w ere considered not worthwhile because the spatial variability of the s oil compartment was regarded too large to detect trends in soil qualit y. However, research suggested that with a statistically sound network design it should be possible to detect relevant trends. As a result, national and provincial. authorities in the Netherlands began to set u p soil monitoring networks in the early 1990s. These networks cover th e rural areas and mainly focus on three environmental aspects of the s oil, namely: spread of contaminants (heavy metals, pesticides, PCB, et c.), and eutrophication and acidification. The goals are the assessmen t of the current soil quality of rural areas and the development of th is quality. An evaluation of the first 5 years of monitoring yields mu ch useful information. Naturally, after the evaluation of the first re sults, optimization of the organization and design of these networks m ust be considered. Topics discussed in this paper include sampling tec hnique, sampling design and the maintenance oi sample archives. Topics of a different category are the concept of homogeneous subregions, th e idea of fixed monitoring locations versus a flexible network, season al variation and its influence on monitoring, and finally the choice o f measured parameters. (C) 1998 Elsevier Science B.V. All rights reser ved.