Mercury in tree rings close to emission sources in Austria

Mercury in wood is an important pool of this heavy metal in forest ecosystems because of its relatively high proportion in the biomass compared to other pools. This paper describes the successful application of a modified methodology for stem disk sampling based on wood particles from stem disks from Donawitz (Styria, Austria; pig iron production), from Brixlegg (Tyrol; former copper and silver mining, copper ore processing and copper recycling), and from Gmunden (Upper Austria; cement production). The maximum mercury concentration in the stem disks from Donawitz (Hinterberg: 20.5 ppb, St. Peter: 9.3 ppb) was recorded in the early 1970s. Several maxima were obtained from the stem disks from Brixlegg: the first was in 1813 (149.9 ppb), potentially even earlier, a second (37.6 ppb) in the late nineteenth century until the late 1920s, and a third local maximum in the 1970s (9.1 ppb), followed by a tendency to decline until the present. A stem disk from Gmunden in Upper Austria showed values of mercury concentrations indicating no increases compared to literature about background sites (≤ 3.2 ppb). This method revealed trends in mercury concentrations in tree rings originating from several different mercury emission sources in Austria coinciding with information about industrial history (where available) together with a justifiable effort. We therefore recommend it for further investigations on mercury concentrations in tree rings and their changes over time.