Analysis of the elemental composition of marine litter by field-portable-XRF

Abstract

Marine litter represents a pervasive environmental problem that poses direct threats to wildlife and habitats. Indirectly, litter can also act as a vehicle for the exposure and bioaccumulation of chemicals that are associated with manufactured or processed solids. In this study, we describe the use of a Niton field-portable-x-ray fluorescence (FP-XRF) spectrometer to determine the content of 17 elements in beached plastics, foams, ropes and painted items. The instrument was used in a 'plastics' mode configured for complex, low density materials, and employed a thickness correction algorithm to account for varying sample depth. Accuracy was evaluated by analysing two reference polyethylene discs and was better than 15% for all elements that had been artificially impregnated into the polymer. Regarding the litter samples, limits of detection for a 120s counting time varied between the different material categories and among the elements but were generally lowest for plastics and painted items with median concentrations of less than 10μgg(-1) for As, Bi, Br, Cr, Hg, Ni, Pb, Se and Zn. Concentrations returned by the XRF were highly sensitive to the thickness correction applied for certain elements (Ba, Cl, Cr, Cu, Fe, Sb, Ti, Zn) in all matrices tested, indicating that accurate measurement and application of the correct thickness is critical for acquiring reliable results. An independent measure of the elemental content of selected samples by ICP spectrometry following acid digestion returned concentrations that were significantly correlated with those returned by the XRF, and with an overall slope of [XRF]/[ICP]=0.85. Within the FP-XRF operating conditions, Cl, Cr, Fe, Ti and Zn were detected in more than 50% and Hg and Se in less than 1% of the 376 litter samples analysed. Significant from an environmental perspective were concentrations of the hazardous elements, Cd, Br and Pb, that exceeded several thousand μgg(-1) in many cases.

Observational Study Unveils the Extensive Presence of Hazardous Elements in Beached Plastics from Lake Geneva

“…Selected samples of various size, color, and texture from each location were analyzed by energy-dispersive XRF using a batterypowered Niton analyser (model XL3t 950 He GOLDD+) for a suite of elements, of which As, Br, Cd, Cl, Cr, Hg, Pb, Sb, and Se are the focus of the present study, under operating conditions described and validated elsewhere (Turner and Solman, 2016). Briefly, the instrument was configured in a plastics mode that is capable of quantifying elemental concentrations in complex, low density materials through a fundamental parameters-based alpha coefficient correction model and a thickness correction algorithm down to 0.05 mm.…”

“…The majority of studies in this area have targeted persistent organic micropollutants, like polychlorinated biphenyls and polycyclic aromatic hydrocarbons, that are sorbed to the plastic surface (Frias et al, 2010;Rochman et al, 2013;Gauquie et al, 2015;Ziccardi et al, 2016;Hong et al, 2017). However, attention has recently been paid to the occurrence and impacts of chemical elements in litter, like metals, metalloids and halogens, that are either adsorbed to the plastic or incorporated into the polymer itself (Boucher et al, 2016;Brennecke et al, 2016;Nakashima et al, 2016;Turner, 2016;Turner and Solman, 2016). While recent empirical evidence and models suggest that the exposure and accumulation of adsorbed compounds or elements may have been overstated in the literature (Herzke et al, 2016), inorganic additives of the plastic matrix, including flame retardants, catalysts and heavy metal-based pigments, appear to represent a more significant source of contaminants to the foodchain (Rani et al, 2015;Massos and Turner, 2017).…”

“…Selected samples are analyzed by portable x-ray fluorescence (XRF) spectrometry using established and validated protocols (Turner and Solman, 2016) for the discrimination of PVC-and non-PVC-based materials and the presence and concentration of elements that are restricted in plastics according to EU Directive 2002/95/EC on the Restriction of Hazardous Substances (RoHS, 2006) and are potentially hazardous to wildlife; namely, the heavy metals, Cd, Hg, and Pb, and the halogen, Br, as a proxy for brominated flame retardants (BFRs). Other, ancillary metals and metalloids (As, Sb, Se, and total Cr) are also considered because of their restriction according to other European Directives (e.g., 2009/48/EC on toy safety; European Parliament and the Council of the European Union, 2009) or whose co-association with the principal elements provides evidence for the types of pigments or retardants present.…”

The evolution of environmental forensics: From laboratory to field analysis

“…Other applications of portable XRF include the analysis of elements in air in relation to occupational health and safety (Bartley et al, ; Lawryk, Feng, & Chen, ; Morley, Clark, Deddens, Ashley, & Roda, ), in oyster shells to determine heavy metals accumulation (Chou et al, ), the screening of hazardous wastes (Vanhoof, Holschbach‐Bussian, Bussian, Cleven, & Furtmann, ) and the screening of marine litter (Turner & Solman, ). Paint waste has also been investigated, mainly to determine the presence of heavy metals in old style paints used to prevent metal rust (Shu, Axe, Jahan, Ramanujachary, & Kochersberger, ) and antifouling paints (Lagerström, Norling, & Eklund, ; Lagerström, Yngsell, Eklund, & Ytreberg, ; Andrew Turner, Comber, Rees, Gkiokas, & Solman, ).…”

Metal analysis in polymers using tandem LA-ICP-MS/LIBS: eliminating matrix effects using multivariate calibration

“…Here, the number of available techniques is limited by the usual absence of the electrical conductivity of polymers, which aggravates the analysis using OES with an arc/spark excitation source 5 or glow discharge-optical emission spectroscopy/mass spectrometry (GD-OES/MS). 6,7 Most commonly applied techniques are therefore Xray based (XRF and EPMA); 8,9 furthermore laser-assisted techniques such as LIBS 10,11 or LA-ICP-MS 12,13 have been used. Due to their non-destructive nature, XRF and EPMA are limited to the analysis of the surface near sample regions, whereas LA-ICP-MS and LIBS also offer the possibility of depth proling.…”