Fig. 1. Differences in Hg concentration of conifer needles with needle age. Data from Norway spruce [Picea abies (L.) H. Karst.] in Germany (Bombosch, 1983); Calabrian black pine (Pinus nigra J.F. Arnold subsp. laricio Maire) in Italy (Barghigiani et al., 1991); red pine (Pinus resinosa Aiton) in Minnesota (Fleck et al., 1999); and balsam fir [Abies balsamea (L.) Mill.] and white spruce [Picea glauca (Moench) Voss] in northern Ontario, Canada (Rasmussen, 1995).