With the continuing shift of industrial activities in developing and transition economies, which often have poor regulation (and weak self-regulation of industries), additional global challenges regarding POPs and other contaminated sites may be expected. In this respect, a comprehensive application of the "polluter pays principle" in these countries will also be a key to facilitate the clean-up of contaminated areas and the prevention of future contaminated sites. The threats and challenges of contaminated sites and the high costs of securing/remediating the problems highlight the need for a comprehensive approach based upon integrated pollution prevention and control. If applied to all polluting (and potentially polluting) industrial sectors around the globe, such an approach will prove to be both the cheapest and most sustainable way to underpin the development of industries in developing and transition economies.

We observed significant increases in the runoff output of total mercury (TotHg) and methyl mercury (MeHg) from a small spruce forest catchment (0.071 km2) after clear-cutting and soil treatment. Here we show that forest regeneration practices may act as an important additional source of TotHg and MeHg to forest lakes. TotHg and MeHg in runoff from two small forested catchments were monitored during the period 1994 to 2001. In the autumn of 1997, one of the catchments was clear-cut Soil preparation (mounding) was carried out in the autumn of 1998 and replanting in the summer of 1999. During the 3 years after the silvicultural treatment, medians of monthly flow-weighted TotHg and MeHg concentrations (12.02 ng L(-1) and 0.35 ng L(-1), respectively) and output loads (0.80-0.97 g km(-2) a(-1) and 0.011-0.036 g km(-2) a(-1), respectively) increased significantly compared to the 3 years calibration period (8.13 ng L(-1) and 0.15 ng 1(-1); 2.0-5.3 g km(-2) a(-1) and 0.11-0.16 g km(-2) a(-1), respectively). These results indicate that clear-cutting and/or soil treatment significantly increases the mobility of TotHg and MeHg accumulated in forest soil and may thus be an important factor for the total input of Hg to boreal freshwater ecosystems.

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Potential rates of methylmercury formation and demethylation were studied in runoff waters, sediment trap material, and aerobic water layers of five small forest lakes by radioisotope methods. In addition, the roles of microbes and particulate matter in methylation and demethylation processes were examined. Methylation rates were low (≤0.12%∙d−1) in all sites studied. Water pH (4.9–6.9) had no clear effect on methylmercury formation. Methylation took place in filtered water (nominal pore size 0.2 μm) and in formaldehyde-treated or autoclaved samples, but was strongly suppressed by both dissolved organic matter (color) and particulate matter. Demethylation rates in surface waters (≤13.2%∙d−1) were decreased by low temperatures and the process was blocked by sterile filtration, formaldehyde treatment, and autoclaving. The results indicate that mercury methylation in aerobic humic waters is an accidental process caused by bacterial exoenzymes or other dissolved compounds. Methylmercury demethylation was clearly microbial in nature.