Influence of External Factors on Recovery and Persistence Parameters of Chemical Weapons–Related Alcohols and Thiols in Concrete Samples

The contamination of materials in urban areas by chemical weapons is a critical issue, especially as these materials can serve as key evidence in forensic investigations. Concrete, commonly found in urban environments, is highly porous and can retain chemical residues. However, its alkaline nature accelerates the degradation of chemical warfare agents, complicating the recovery of usable evidence. This study explores the recovery and persistence of alcohols and thiols, final degradation products of nerve and blistering agents, from two types of concrete matrices: lightweight concrete formworks and dense, steel-reinforced concrete blocks. Using an optimized method, uncrushed concrete fragments (up to 85 g) were extracted with acetone, monitoring two critical parameters: apparent recovery and persistence. The influence of external conditions, such as water addition, temperatures between 5°C and 35°C, and varying airflow speeds (1.7-5.1 m·s^-1), was systematically evaluated. Reference conditions involved dried concrete at 22°C with no airflow. The findings revealed that alcohol recovery aligned with the volatility of the compounds, with denser concrete exhibiting lower recoveries but greater persistence. Thiols quickly converted to disulfides. Notably, temperature and moisture had the most profound effects on the recovery and persistence of the chemicals. These results highlight the importance of considering environmental factors when assessing chemical warfare agents and their degradation products in concrete, offering insights relevant to forensic science, environmental safety, and military defense. The study demonstrates how concrete's properties and external conditions can alter the forensic traceability of chemical contaminants.