Characterization of a pollution source with isotopic and physicochemical measurements using a forensic metrology approach

Abstract

Carbon and nitrogen composition and isotopic ratios (δ15N, δ13C, and δ13C-DIC) as well as physicochemical parameters were measured in hazardous waste leachate connected to an environmental pollution crime. A forensic metrology approach was employed by estimating the measurement uncertainty, including that from the sampling process, using range statistics. The physicochemical parameters demonstrated differences in the leachate from some of the different ponds and this was supported by carbon and nitrogen elemental and isotopic analyses. The isotopic signature of δ15N and δ13C-DIC was highly enriched in the heavy isotope demonstrating that those analyses are a substantial tool for leachate pollution tracking. The uncertainty of the measurements was below or slightly above 20% for most parameters which can be considered fit-for-purpose for a great deal of environmental surveys and was remarkably lower in the isotopic analyses. The uncertainty of measurement including the primary sampling is a relevant information in environmental investigations, especially forensic ones. This knowledge is crucial for a consistent interpretation of environmental samples analyses results, specially from polluted sites and pollution source characterization and tracking, where there is often substantial heterogeneity in environmental samples.