BACKGROUND VALUES OF HEAVY-METALS IN ARAB LE SOILS AS DERIVED FROM ANALYSES IN CONNECTION WITH THE SEWAGE-SLUDGE LEGISLATION

In connection with the Sewage Sludge Ordinance between 1994 and 1996 2 7 000 samples from arable soil of 24 counties in Lower Saxony were ana lysed for aqua regia soluble Cd, Cr, Cu, Hg, Ni, Pb, and Zn. From thes e data the 90. percentiles for each county and soil texture class and from this background values were derived. Distinctly higher 90. percen til values for single elements from particular districts are seperatel y discussed with regard to pollution. In no case the proposed backgrou nd values reach the precaution values of the proposed soil protection legislation from June 1997.