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Quantification of soluble chromium(VI) in soils and evaluation of ecotoxicological effects

: Rüdel, H.; Wenzel, A.; Terytze, K.


Environmental geochemistry and health 23 (2001), pp.219-224
ISSN: 0142-7245
ISSN: 0269-4042
Journal Article
Fraunhofer IUCT ( IME) ()
bioassay; ecotoxicology; hexavalent chromium; photometric method; soil

In the German Federal Soil Protection and Contaminated Sites Ordinance (Bundes-Bodenschutz- und Altlastenverordnung, June 19, 1999) precautionary values are stated, which, if exceeded, give reason to suspect harmful effects in soils. Depending upon soil type (sandy, silty, and clayey), the respective precautionary values for total chromium as determined in the aqua regia extracts are 30, 60 and 100 mg kg (exp -1). It is assumed that a maximum of 10 per cent of the total chromium is chromium(VI). This assumption seems to apply to natural soils, where only low chromium(VI) concentrations were found, even with high total chromium levels (Rüdel and Terytze, 1999). However, in anthropogenically influenced soils higher chromium(VI) contents may occur. In these cases the chromium(VI) content may be high enough to damage soil organisms though the total chromium concentration is below the respective precautionary value. Therefore, direct determination of the chromium(VI) content seems to be advisable. For this purpose a photometric method was enacted as a German standard in 1999 (DIN 19734, 1999). The current study was performed in order to examine whether or not the soil threshold values for chromium(VI) given in the Federal Soil Protection Ordinance could protect the habitat function of the soil. The effects of chromium(VI) were investigated in ecotoxicological standard tests with plants, earthworms and micro-organisms in two soils spiked with chromium(VI). The actual chromium(VI) concentrations were determined following the standard method DIN 19734 in order to correlate these chromium(VI) concentrations to potential biological effects.