X-Ray Core Scanners as an Environmental Forensics Tool: A Case Study of Polluted Harbour Sediment (Augusta Bay, Sicily)

<p>Since the 1970s the highly industrialised and enclosed Augusta Bay (Sicily) has become internationally recognized as a polluted environment that could represent a hazard to human health. The pollutant of greatest concern, derived from a former chlor-alkali plant, is mercury that exists beyond Intervention Levels in parts of the harbour. The affected areas are also contaminated by other heavy metals and organic compounds (PAHs and PCBs) that were mainly discharged from co-located petrochemical industries. Several previous investigations established the magnitude of particular contaminants in sediments and evaluated the impact of the pollution on a range of biota. The current study, which represented part of a larger project managed by the Italian Environmental Research Institute ISPRA, was concerned with investigating a series of cores collected across the harbour area to establish reliable pollution chronologies based on elemental and radiochronological (¹³⁷Cs) profiles. The declared motivation for the main project was to acquire scientific evidence that could be used to support a legal investigation against the industries that caused the pollution and who could potentially be expected to contribute to remediation costs. Undisturbed cores were collected from the northern (mildly polluted), central (significantly polluted) and southern (strongly polluted) parts of the Bay using available bathymetric data to avoid areas affected by dredging. The study has demonstrated the value of using an automatic, X-ray sediment core scanner (Itrax) to acquire high-resolution geochemical data. The Itrax provided a non-destructive, sensitive and rapid capability to systematically analyse a broad range of major and trace elements. One of the collected cores of this study, taken from the most polluted site, provided more than 20 continuous elemental profiles with depth (e.g. Ti, S, Ca, K, Mn, Fe, Cr, V, Ba, Cu, Zn, Br, Rb, Sr, Zr, Hg, Se, Mo). The Itrax data quality were validated against a dataset acquired using a conventional WD-XRF instrument and both sets of profiles are demonstrated to be consistent. This ability of the Itrax to automatically scan cores over a significantly shorter time compared to conventional laboratory methods (days compared to weeks) confirms its potential in contributing to environmental forensic studies. Its additional ability to simultaneously record a radiographic image (and radiographic digital profile) provides a link between sediment layering (density variations linked to mineralogy) and elemental composition.</p>