| Abstract
| - A critical gap in the understanding of the global cyclingof mercury is the limited data describing the naturalbackground atmospheric deposition rate of mercury beforethe advent of pollution. Existing estimates of the naturaldeposition rate are typically about 2−5 μg of Hg m-2 year-1(see, for example, Swain et al. Science1992, 257, 784−787), based on studies that generally rely on short, 210Pb-dated lake sediment and peat cores that span the past150 years. Analyses of mercury in long peat cores insouthcentral Sweden indicate that natural mercury depositionrates in the period 4000−500 BP were lower, about0.5−1 μg of Hg m-2 year-1. This suggests that recentmercury accumulation rates in the peat (15−25 μg of Hgm-2 year-1) and measured atmospheric deposition rates ofmercury in Sweden over the past 3 decades (5−30 μgof Hg m-2 year-1) (Munthe et al. Water, Air, Soil Pollut.:Focus2001, 1, 299−310) are at least an order of magnitudegreater than the prepollution deposition rate, rather thanrepresenting only a 3−5-fold increase, as has generally beenestimated.
|
