Between 1920 and 1967, approximatively 8200 tons of ammunition waste were dumped into some Swiss lakes. This study is part of the extensive historical and technical investigations performed since 1995 by Swiss authorities to provide a risk assessment. It aims to assess whether explosive monitoring by passive sampling is feasible in lake-bottom waters. Polar organic chemical integrative sampler (POCIS) and Chemcatcher were first calibrated in a channel system supplied with continuously refreshed lake water spiked with two nitroamines (HMX and RDX), one nitrate ester (PETN), and six nitroaromatics (including TNT). Exposure parameters were kept as close as possible to the ones expected at the bottom of two affected lakes. Sixteen POCIS and Chemcatcher were simultaneously deployed in the channel system and removed in duplicates at 8 different intervals over 21 days. Sorbents and polyethersulfone (PES) membranes were separately extracted and analyzed by UPLC-MS/MS. When possible, a three-compartment model was used to describe the uptake of compounds from water, over the PES membrane into the sorbent. Uptake of target compounds by sorbents was shown not to approach equilibrium during 21 days. However, nitroaromatics strongly accumulated in PES, thus delaying the transfer of these compounds to sorbents (lag-phase up to 9 days). Whereas sampling rate (R-S) of nitroamines were in the range of 0.06-0.14 L day(-1), R-S of nitroaromatics were up to 10 times lower. As nitroaromatic accumulation in PES was integrative over 21 days, PES was used as receiving phase for these compounds. The samplers were then deployed at lake bottoms. To ensure that exposure conditions were similar between calibration and field experiments, low-density polyethylene strips spiked with performance reference compounds were co-deployed in both experiments and dissipation data were compared. Integrative concentrations of explosives measured in the lakes confirmed results obtained by previous studies based on grab sampling. (C) 2019 Elsevier Ltd. All rights reserved.

Between 1920 and 1967, approximatively 8000 tons of ammunition waste was dumped into some Swiss lakes. Previous studies based on grab sampling revealed small traces of cyclotetramethylenetetranitramine (HMX), cyclotrimethylenetrinitramine (RDX) and pentaerythritoltetranitrate (PETN) in the water column of two studied lakes; however these researches showed that the ammunition waste at the lake bottom was likely not involved in that contamination. On the contrary, external sources (tributaries contaminated by hot spots such as ammunition destruction locations or ammunition factories) might be the main cause. The ultimate goal of this study is to assess whether explosive monitoring by passive sampling is technically feasible in the affected lakes and rivers, and whether integrative sampling confirm former results obtained by grab sampling. As a first step, POCIS (HLB powder sandwiched by two PES membranes) and Chemcatcher (SDB-RPS disk covered by a PES membrane) were calibrated in a channel system supplied with continuously refreshed lake water spiked with two nitramines (HMX, RDX), one nitrate ester (PETN) and seven nitroaromatics (2,4,6-trinitrotoluene (TNT) and three of its degradation products, 1,3-dinitrobenzene, 2,4- and 2,6-dinitrotoluene). Exposure parameters in the system were kept as close as possible to the ones expected in the first meters above sediments of the studied lakes. Sixteen POCIS and Chemcatcher were simultaneously deployed and removed in duplicates at 8 different intervals over 21 days whereas water analysis (SPE extraction) was carried out daily. PES membranes (pore size of 0.1μm) and sorbent phases were separately extracted and analyzed by UPLC-MS/MS. LDPE strips spiked with PRCs were also deployed in the channel system to obtain dissipation data in the calibration conditions. Results of the calibration showed that the accumulation of HMX and RDX (log Kow <1) in sorbent materials was higher or similar to the accumulation in PES membranes. The transfer of these two compounds from water to sorbents was quick (lag-phase < 1day). For PETN (log Kow about 2), the accumulation was slightly higher in PES membranes than in sorbent materials, leading to lag-phase of about 3 (POCIS) to 5 (Chemcatcher) days. The affinity of nitro aromatic compounds for PES membranes was shown to be very high, strongly delaying the transfer of these compounds to sorbents (lag-phase up to 9 days). Sampling rate (Rs) of HMX and RDX were in the range of 0.1 L/d with POCIS and 0.05 L/d with Chemcatcher. Because of the long lag-phases, Rs of nitroaromatics were up to 10 times lower, which can potentially be an issue in terms of sensitivity (expected concentrations in the lakes in the sub-ng/L range). As a second step, the samplers were deployed on lake-bottom sediments (200m depth) using a Remotely Operated Vehicle (ROV) to unhook and re-hook the rope that was used to descend and retrieve the sampler holders. The holders were equipped with a temperature probe. In addition of estimating water current velocity by measuring particle velocity with the ROV camera, LDPE strips spiked with PRCs were co-deployed to compare the dissipation data with the ones from the calibration experiment. Extraction and analysis are currently being carried out and will be discussed along with the first tests done in rivers.

Non-military explosives are used mainly for mining and tunnel construction, for building demolition and for various special uses such as setting off avalanches and for seismic investigations. Common to all explosives is their heterogeneous structure, the great work capacity (blast effect) and the advantage that the detonation releases only small amounts of poisonous explosion gases. Modern explosives for tunnel construction can be pumped and are capable of exploding only on site, by the addition or chemical generation of microbubbles. With the introduction of electronic detonators, explosive technology entered a new era. These detonators are very safe and precise, and it is possible to program up to 1600 detonators in one blasting operation.

Military high explosives are safe to handle, have a long shelf life, their energy density is high and the propagation of the explosion (detonation reaction) is very fast. The energetic compounds are combined with polymersand other substances to match the properties as required. To initiate a detonation, a shock wave is needed. This is accomplished with a small quantity of a primary explosive. Modern, extremely insensitive formulations have been developed in most countries to eliminate accidents with ammunition. Apart from insensitive energetic compounds, new inert or energetic binder systems will be introduced to improve the vulnerability. The search for new energetic materials with highest performance characteristics is a never-ending task.

The critical temperature-time regime of the self-ignition of energetic ammunition systems is usually investigated by elaborated experimental setups, e.g. in the EIDS slow cook-off the sample is heated with a rate of 3.3°C/h in a steel container. The results collected in such experimental setups can be successfully simulated by applying kinetic parameters obtained from non-isothermal isochoric experiments (closed crucibles) performed on any commercial Differential Scanning Calorimetry (DSC) system. During modeling two important factors have to be considered: (i) the application of advanced kinetics, which properly describes the complicated, multistage course of the decomposition process and (ii) the effect of heat balance in the energetic ammunition system, as the sample mass is increased by a few order of magnitude compared to the thermoanalytical DSC experiments. The correct accumulation of heat for large sample masses can be calculated by applying Finite Element Analysis (FEA) methods as described by us in (1-2). The results of modeling have been verified by the comparison with the experimentally determined values of the time to ignition for single base propellant being used in 5.56 mm small caliber system and a new 155 mm artillery charge for the Swiss army under isothermal conditions. For the artillery charge the simulations have been done for the sample being in the form of cylinder containing three layers of the materials possessing significantly different thermal properties, namely single- base propellant, combustible cartridge case and steel container. The very good prediction of the experimental results indicates the high accuracy of the applied method. Evaluation of kinetics The evaluation of the kinetics of the decomposition of energetic materials is one of the main prerequisites necessary for the correct modelling of their properties. Generally, the kinetic parameters are calculated from the experimental data obtained either from thermogravimetry (change of the mass, TG) or differential thermal analysis (monitoring thermal effects, DSC or DTA). Independent of the experimental technique applied, the kinetic calculations require the dependence of the reaction extent α on the time or temperature. Calculations of the reaction progress are much easier from TG data and require only the correction of the signal due to the buoyancy phenomena. More complicated is the determination of the relationship α-T from DSC (DTA) traces because it requires the integration of the signals influenced by the construction of the baseline.