Contamination, sampling and runoff of metals on Steinsjøen firing range – testing of methods in the field and laboratory

The Norwegian Armed Forces’ shooting and training ranges (SØF) contain heavy metals from spent ammunition. These can be harmful to animals, plants, and biota in the area. The pollution can also leak into water. It is important to map pollution and runoff sufficiently when evaluating measures against the spread of pollution.

To test methods for mapping and monitoring metals and their runoffs on firing ranges, we designed experiments that we carried out on Steinsjøen SØF. The work described in this report highlights issues and questions such as: Which methods should be used for mapping contami-nation in soil, how does soil chemistry affect the leaching of metals, how well are metals adsorbed in clean soil and filter media, what is the runoff pattern through firing ranges, and which water sampling methodology and preparation should be used for the most representative result?

Using an excavator and soil auger, we compared core sampling and tested XRF analysis as a method for mapping metal contamination on a shooting range. We also compared our XRF analysis with ‘multi incremental sampling’ (MIS) and ICP-MS analysis on a smaller area (5x5 m). We measured the leaching pattern of metals through the shooting range and compared it to the metal contamination pattern found with the XRF. Our soil samples were analysed, looking for copper, lead, antimony, zinc, cation exchange capacity, grain size distribution, pH and total organic carbon. To investigate the leaching and sorption potential of metals in the soil compared with the soil’s physical and chemical attributes, we carried out leaching and sorption tests. We also tested sampling methodology and preparation of water samples and compared single samples, ISCO samples, Sorbicell, and DGT. We tested how the storage of water samples in the field affected the metal concentration and whether acid preservation had any effect. Filtration of samples (<0.45 μm) in the field were compared with filtration in a laboratory after a few days. Metal concentration was analysed and compared in total digested, filtered, and untreated water samples.

Soil auger turned out to be a simpler and more efficient way to collect core samples than exca-vations. XRF can be used to map contaminated areas, but to determine metal concentration in soil in an area, samples should still be sent to the laboratory. The soil’s physical and chemical attributes can give us information about its potential for leaching, but the best method is leaching tests. Uncontaminated soil from Steinsjøen adsorbed copper and lead well, which means that infiltration through clean soil can reduce leakage from firing ranges. Runoff of metals from Steinsjøen SØF varied a lot throughout the season, which means that multiple samples should be collected to monitor or map the leakage from shooting ranges. In ISCO samplers (automated sampler), some metals may precipitate. Therefore, Sorbicell together with DGT will be suitable for monitoring pollution over a period. There was little difference in metal concen-tration measured in samples filtered in the field compared to laboratory filtering a few days later. Therefore, filtration in the field does not seem to be necessary. The storage of samples influ-enced their metal concentration. In acid-preserved samples, the lead concentration remained stable, but in unpreserved samples, it decreased. For copper and zinc, the concentration remained stable in unpreserved samples, while it increased in preserved samples.