Chemical pollution of aquatic and terrestrial environments with munition constituents (MCs) such as explosives from the legacy of military activities poses a potential risk to ecosystems and human health. The exposure assessment of the diffuse pollution originating from several hundred thousand tons of ammunition dumped worldwide into aquatic environments during the 20th century was, however, impeded by the sampling resolutions, instrumental sensitivities, and/or the scope of quantified MCs of past monitoring studies. Moreover, the ongoing deterioration of ammunition casings, which is closely tied to environmental conditions, might alter the likelihood of MC emissions and is understood only scarcely. This is especially the case for landlocked countries such as Switzerland, where freshwater lakes hold not less than 14 thousand tons of ammunition.

In our study, we are therefore designing sampling procedures and analytical methods to investigate the emission and fate processes of MCs from ammunition deposited in freshwater lakes. Specifically, we are developing methods for the quantification of 24 MCs and selected transformation products in water and sediments in the low to sub- ng/L and µg/kg concentration range with liquid chromatography-high resolution tandem mass-spectrometry (LC-HRMS/MS). Limits of quantification for water analysis using evaporation for enrichment (0.01 to 1 μg/L) were significantly improved by implementing online solid-phase extraction (SPE) instead (0.1 to 10 ng/L). Using a solid-liquid extraction method for sediment analysis, very good absolute recoveries of 80-120% are obtained for 75% of our analytes. To support the evaluation of MCs distribution and ammunition casings deterioration, we are performing complementary analyses including (1) Pb-210 dating, (2) X-ray fluorescence (XRF) scanning with a focus on heavy metals, and (3) clay and total organic carbon (TOC) content estimation as indicators for MC sorption to sediment constituents. These analytical procedures are being applied to samples collected over selected open-water ammunition deposition sites in Switzerland. To increase sampling resolution, we successfully tested the deployment of a multicorer which allowed to simultaneously retrieve 6 cores of 60-80 cm at fixed relative horizontal distances at 215 m underwater in 20 min. This study will provide valuable information for the potential needs and risks of recovering ammunition lying at the bottom of Swiss lakes.