Abstract
<jats:p>The paper presents the results of a physicochemical study of mixed fuel thermal decomposition products using an integrated approach that combines X-ray fluorescence (XRF) analysis and gas chromatography-mass spectrometry (GC-MS). The relevance of the research is determined by the need to develop reliable criteria for identifying the composition of fuel raw materials for environmental monitoring and fire-technical forensics. The aim of the work was to identify specific mineral and organic markers in soot and ash to establish the nature of the combusted materials. State-of-the-art instrumentation was employed for the analysis, ensuring high precision in quantifying the elemental composition and identifying volatile organic compounds. The study established that the mineral phase of combustion products reflects the presence of anthropogenic contaminants in the fuel. Specifically, in samples containing municipal solid waste and polymers, significant concentrations of zinc and lead were detected in conjunction with sulphur, resulting from the degradation of inorganic pigments and stabilisers. GC-MS analysis enabled the identification of biomass decomposition markers, such as levoglucosan and methoxyphenols, and the detection of dibutyl phthalate and heavy polycyclic aromatic hydrocarbons (PAHs), indicating deep chemical transformations of synthetic chains in the high-temperature zone. The investigation of interfacial interactions confirmed the complex nature of organic compound stabilisation by the mineral matrix. It was found that ash components act as adsorption centres for heavy aliphatic hydrocarbons and siloxanes, preventing their complete thermal decomposition. The intensity ratios of PAH peaks with varying degrees of condensation indicate the catalytic role of metal oxides in secondary aromatisation processes. The obtained results confirm that the proposed physicochemical approach is an effective tool for diagnosing the composition of combusted raw materials, enabling the detection of illicit use of harmful additives and establishing the sources of anthropogenic impact on the environment.</jats:p>