Carcinogenic effects of hexavalent chromium in waters are of concern in many countries worldwide. We explored Cr isotope systematics at 11 sites in the Czech Republic and Poland. Geogenic Cr pollution was associated with serpentinite bodies at former convergent plate margins, while anthropogenic Cr pollution resulted from electroplating, tanning, and the chemical industry. Cr(VI) concentration in geogenic waters was less than 40 ppb. Anthropogenic waters contained up to 127,000 ppb Cr(VI). At both geogenic and anthropogenic sites, where known, the source of pollution had a low δ53Cr (<1‰). δ53Cr of geogenic and anthropogenic waters was up to 3.9 and 5.8‰, respectively. At both serpentinite-dominated and industrial sites, δ53Cr(VI)aq was shifted toward higher values, compared to the pollution source. At the industrial sites, this positive δ53Cr shift was related to Cr(VI) reduction, a process known to fractionate Cr isotopes. At geogenic sites, the origin of high δ53Cr(VI)aq is tentatively ascribed to preferential release of 53Cr during oxidation of soil Cr(III) and its mobilization to water. δ53Cr(VI) of industrially contaminated waters was significantly higher (p<0.001) compared to δ53Cr of waters carrying geogenic Cr(VI), implying that either the effective fractionation factor or process extent was greater for Cr(VI) reduction than for Cr(III) oxidation.

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For old soil and groundwater pollution from the past, a 'polluter-pays' principle is not so simple to apply. Generally, a large-scale involvement of public financial sources is inevitable. Experience has proved that an appropriate information base and prioritisation are important conditions for effective allocation of effort and money for these purposes.Presently, a new national priority setting system is being tested in the Czech Republic. It sorts all polluted sites into several basic categories according to the statement specifying a character of the actual or potential pollution impact to public health, environment and/or to other interests. For each category, a corresponding principle of necessary or desirable action for mitigation of the risk issuing from the site pollution is explicitly defined. A basic qualitative statement characterizing a site pollution impact is preferentially based on results of its risk analysis. A simple scoring system is used to assess urgency for investigation of sites with lacking or insufficient data.