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

Abstract

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 ( 137 Cs) 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,

New coring study in Augusta Bay expands understanding of offshore tsunami deposits (Eastern Sicily, Italy)

“…The elemental distribution in the MG cores (Figs 5, S5, S6, S7 and S8), except for units L1 and L2 (Fig. ), is in line with that reported for the uncontaminated sediments of inner Augusta Bay, which consist primarily of carbonates (Ca and Sr) and clays (Si, K and Rb; Croudace et al ., ) as well as the outcropping geology, dominated by carbonates and volcanoclastics/volcanics within muddy sediments and calcarenites (Grasso & Lentini, ). While the Ca and Sr signatures dominate the marine sediment, due to the occurrence of carbonates (Chagué‐Goff et al ., ), Ti/Ca and Ti/Sr are most likely to reflect the terrigenous input, with Ti sourced from volcanics, gneiss and schists and thus often used as an indicator of terrestrial material in onshore or offshore tsunami deposits (Chagué‐Goff et al ., ).…”

“…As a consequence, a wide range of contaminants (Hg, Pb, Cu, heavy hydrocarbons, etc.) have been introduced into the harbour since the early 1960s, and have been partially retained in the sediments (Romano et al ., ; Sprovieri et al ., ; Bellucci et al ., ; Croudace et al ., ) due to the contemporary construction of outer breakwaters. The high pollution levels in Augusta Bay (especially for Hg), have presumably caused stressful conditions to Posidonia oceanica , leading to its complete disappearance, as detailed in several studies (Di Leonardo et al ., , , ; Sprovieri et al ., ).…”

Future Developments and Innovations in High-Resolution Core Scanning

“…Many researchers continue to use either count or count-rate data as supplied by the instrument's software or they may adopt a semi-empirical approach by analyzing a small number of sub-samples using WD-XRF, ED-XRF or ICP-OES to calibrate their data (e.g. Boyle et al 2015;Croudace et al 2015). A more advanced approach based on the use of multi-variate statistics is described by Weltje et al (2015) and represents a significant advance that could become increasingly used.…”

“…With their ability to simultaneously and non-destructively measure thirty or more elements (and other co-registered properties such as magnetic susceptibility and a radiographic image), X-ray core scanners have made a significant contribution to the study of marine, estuarine and lacustrine sedimentary sections as well as rocks, coal, speleothems and tree rings (e.g. Croudace et al 2006;Rothwell et al 2006; Thomson et al 2006;Croudace and Rothwell 2010;Rothwell and Croudace 2015;Croudace et al 2015;Kelloway et al 2015). Many of the existing XRF core scanners originated as concepts or prototypes in marine science establishments (universities and research institutions in Holland, UK and Japan) from the 1990s through to the early 2000s.…”

An Empirical Assessment of Variable Water Content and Grain-Size on X-Ray Fluorescence Core-Scanning Measurements of Deep Sea Sediments

“…The counts are not normally matrix corrected and several previous studies have shown that there is a good first approximation to concentration (e.g. Croudace et al 2006Croudace et al , 2015. Users also commonly take small subsamples and analyse using a quantitative destructive method (ICP-OES or WD-XRF) to validate/calibrate Itrax data.…”