Soil intake in ruminants grazing on heavy-metal contaminated shooting ranges

Abstract

Shooting ranges contain copper and lead from spent ammunition, this contamination can represent a risk for ruminants grazing there. The present study investigated the intake of copper and lead by sheep and cattle grazing on shooting ranges. Three factors are important for the ingested dose of metals: soil ingestion rate, accumulation of the metals in plants and grazing behavior. Up to 3700 mg Pb/kg dry weight (dw) and 1654 mg Cu/kg (dw) was found in soil and up to 52 mg Pb/kg (dw) and 35 mg Cu/kg (dw) was found in grass. The limit for sensitive land use set by the Norwegian Environment Agency is 60 mg Pb/kg and 100 mg Cu/kg, and the EU limit in fodder is 33.6 mg Pb/kg (dw). Soil ingestion was found by using titanium as a tracer, as titanium is abundant in soil, but not taken up in plants or animals. Low soil ingestion rates (<2%) were found in all investigated areas, including three shooting ranges and one cultivated pasture. There was no correlation between the copper concentration in soil and grass, such a correlation was found for lead. The risk of copper and lead poisoning by ruminants on shooting ranges was assessed based on the copper and lead concentration in the soil and grass, the soil ingestion rate and the grazing behavior. The risk assessment concluded that the calculated dose of copper (chronic sheep: 0.07, cattle: 0.08, acute sheep: 0.7, cattle: 0.8, mg/kg, body weight (bw), day) and lead (chronic sheep: 0.12, cattle: 0.12, acute sheep: 1.2, cattle: 1.2, mg/kg, bw, day) ingested by ruminants was much lower than both the assumed chronic (Cu sheep: 0.26–0.35 cattle: 8, Pb sheep and cattle:6, mg/kg, bw, day) and acute toxic doses (Cu sheep: 20–100, Pb sheep and cattle: 600–800, mg/kg bw) for sheep and cattle.