Chemical Speciation of Particulate Matter as a Tool in Air Pollution Forensics: A Case Study

Abstract

Signature pollutant identification is an important step in the forensic analysis of environmental pollution cases. This makes the process of source identification easier while making legal responsibility allocation less challenging. Massive firework displays (FWD) associated with festivals, though are short duration events, have the potential to severely deteriorate the air quality due to the quantity and toxicity of the pollutants involved. In this study, the emissions during a FWD associated with a festival were analysed to identify the signature pollutants that help in attributing the emissions to the FWD with a certainty demanded by legal institutions. The strategy involved speciation of the particulate matter sampled from the site for metals, investigating all possible sources of the metals observed through literature study and field investigations, and comparing their concentrations in samples collected before and after FWD. An elimination procedure was adopted, where those metals that do not show an increase after FWD and those that have other possible sources are excluded from the possible list of signature pollutants. The signature pollutants obtained for the case investigated were As, B, Ba, Cd, Cr, Cu, Li, Mg, Mn, Pb, Sr, V, and Zn. The study also revealed serious violations, where metals legally banned for use in fireworks were observed in the emissions from FWD. The study presents a robust procedure for identifying signature pollutants that helps in attributing emissions to FWDs.