火场助燃剂检验鉴定的干扰研究进展

Research progress on interference in the identification of accelerants in a fire scene

火灾是影响公共安全最为常见的灾害之一,而放火更是严重威胁人民群众生命财产安全,属于典型的暴力犯罪。犯罪嫌疑人为了达到有效快速放火的目的,往往使用助燃剂实施放火,因而助燃剂的检验鉴定对于认定火灾性质起着至关重要的作用。然而火场情况复杂,容易对助燃剂物证检验鉴定产生较大干扰。在火灾发生发展的过程中,火场高温热环境会作用于已形成的助燃剂燃烧残留物,造成助燃剂的特征组分发生不同程度地挥发、热解等变化,从而影响其检出;同时火灾现场存在的大量石油化工产品,其燃烧/热解产物与常见的助燃剂存在相似甚至相同的特征组分,对判断现场是否存在助燃剂有着很大干扰;而在火灾扑灭之后,助燃剂燃烧残留物在火灾现场还会受到常温环境中光照、压力、通风等因素的共同作用发生物理挥发,其特征组分的质量分数会随之发生下降从而对助燃剂鉴定产生影响;特别地,土壤类物证因土壤中有着不计其数的微生物,它们会使存在于土壤中的助燃剂特征组分发生降解,导致助燃剂组分的减少或缺失,严重影响助燃剂鉴定的准确性。该文从火场热环境、基质干扰、风化效应以及微生物效应4个方面梳理了火场条件对助燃剂检验鉴定干扰的研究现状,重点介绍了火场热环境、橡胶及其制品作为典型基质对汽油检验鉴定影响的新成果,同时指出现阶段此领域研究的不足,并对研究方向进行了展望,旨在为火场助燃剂物证检验鉴定提供参考。

Fire is one of the most common disasters threatening public safety and social development;arson,a typical violent crime,is a serious threat to people’s lives and property.Suspects are likely to use accelerants to commit effective and rapid arson.Therefore,the identification of accelerants is of crucial importance in determining the nature of a fire.Fires are commonly complex and intricate,leading to remarkable interference in accelerant identification.During the development of a fire,thermal environment influences the preformed accelerant combustion residues,causing the characteristic components of the accelerant to volatilize/pyrolyze to different degrees,thus interfering with accelerant identification.There are numerous petrochemicals with characteristic components similar to those of accelerants in fire scenes,also contributing to the interference in the determination of the presence of accelerants.After the fire is extinguished,the combustion residues of the accelerant in the fire scene are influenced by the combined effects of heat,light,and pressure in the ambient environment,resulting in the loss of the mass fraction of characteristic components,mainly in the form of volatilization.In particular,with countless microorganisms in the soil,the characteristic components of the present accelerants are degraded,resulting in the reduction or absence of some components,which seriously influences the accuracy of accelerant identification.This study describes the progress of research on the interference in accelerant identification induced by various factors at fire scenes from four aspects:thermal environment,matrix interference,weathering effect,and microbial degradation,with emphasis on the interference from the first aspect.Based on the correlation between the matrix chemical composition/structure and interference degree,new results pertaining to the interference source in accelerant identification are also considered.The shortcomings of current research and the prospects for future research are put forward to provide a reference for accelerant identification at fire scenes.Many studies have been conducted on the above four types of interference in recent years,which provide important reference for accelerant identification regarding the arson caused by ignitable liquids.However,with the application of new materials and techniques,fire scenes have become increasingly complex,which demands higher requirements for accelerant identification in forensic science.Research on thermal environment interference is still in its infancy,and it is of great practical significance to conduct this research on other types of accelerants coupled with other interference factors.In addition,the principle of most of the current research on selecting objects is based on common appearance at fire scenes,rather than the functional group of the chemical structure of the matrix.Systematic and in-depth research on the interference law and mechanism is urgently required,and it is vital to further explore the interference law of the fire background from the perspective of the chemical composition and chemical structure of the substrate.Compared to foreign countries,there is less research on the interference of weathering and microbial effects on ignitable liquid identification in China.Most importantly,there is a lack of unified provisions,such as standard experimental methods to carry out such research,making it urgent to establish relevant standards and specifications.Additionally,while weathering is caused by multiple factors,the existing research on the interference of the weathering effect with ignitable liquid identification focuses merely on volatilization.Therefore,a more accurate experimental design is necessary.Improving the database of interferents under fire conditions,and combining the application of the chemometrics method for the artificial intelligence identification of the combustion residue spectrum,is an effective way to further improve the identification efficiency and accuracy.