Episodic discharge of lead, copper and antimony from a Norwegian small arm shooting range

Small arm shooting ranges are major deposits of lead (Pb), copper (Cu), antimony (Sb), and zinc (Zn) from use of ammunition. Metals and metalloids from the ammunition residues may leach into the soil and surrounding watercourses and may pose a threat to exposed wildlife and humans. Discharge of elements is dependent on several factors such as soil properties, hydrological conditions, precipitation and time. In order to identify strategies to limit spread of ammunition residues from shooting ranges it is of importance to gain knowledge of the mobility of the elements from the spent bullets. Here we have monitored the levels of Pb, Cu and Sb in a small drainage stream from a Norwegian military small arm shooting range in 2001 and 2006. The first campaign in 2001 was initiated ahead of the snow-melting period in the spring and continued two months in order to quantify discharge and discharge patterns of the selected elements in the drainage stream. Two shorter campaigns were performed in autumn 2001 during an excavation, and in summer 2006. Mean levels of Pb, Cu and Sb in the stream during the first monitoring period in 2001 were 14 microg/l, 39 microg/l and 9 microg/l respectively. High flow, following precipitation, led to an approximately fourfold increase in the concentration of Pb and threefold increase in the level of Cu and Sb compared to low discharge concentrations. An estimation of discharge of the metals showed that the snow melting period and precipitation events constituted to a large proportion of the total release. A sudden increase in the levels can induce more stress and reduce survival of exposed aquatic animals due to the short time available for adaptation.