Source apportionment of industrial fugitive dusts: Developments in passive dust monitoring

Datson, Hugh; Fowler, Mike; Williams, Ben

Abstract

DustScan is a passive (i.e. unpowered) dust sampling method. It uses a transparent adhesive ‘sticky pad’ to sample dust in flux and in deposition for subsequent image-based quantification and, as appropriate, geochemical analysis. Samples are obtained over typically 7 – 14 day intervals in the vicinity of industrial sites such as quarries, surface coal mines, landfill sites and construction and demolition sites. DustScan was developed at the University of Leeds (Farnfield and Birch, 1997) and refined at DustScan Ltd and the University of Leeds (Datson and Birch, 2006). Dedicated geochemical analysis methods of DustScan samples using ICP-AES and ICP-MS have been developed (Datson and Fowler, 2007) and their use in environmental forensics has been demonstrated by quantifying dust propagation at a hazardous waste landfill site (Fowler et al. 2010). However, wider environmental forensic applications of the method have been constrained largely by the impracticality of detaching the sampled dust from the collection media. Until recently, the sticky pads have been die-cut from sheets of a proprietory transparent PVC film with a permanent, cross-linked polymer-acrylic adhesive. Whilst this type of adhesive has excellent environmental dust sampling characteristics, its formulation renders it essentially insoluble (except in solvents that also dissolve much of the dust, e.g. HF). Furthermore, on retrieval after field sampling the sticky pads are sealed with a transparent film to facilitate handling and minimise contamination, thus making physical removal of dust at a later date difficult. Since the most effective means of dust ‘extraction’ from the sticky pads has been in solution and the image-based quantification method does not assess dust mass, geochemical data have been reported in terms of concentration in the extraction (e.g. ppm in solution) rather than in the dust (e.g. mg g-1). Confidence in adequately low detection limits has also been compromised by variable concentrations of some metals (e.g. Zn, Ba) in the sampling media. Funding was obtained from the Finance South East Ltd (FSE) proof of concept (PoCKeT) fund to investigate alternative dust sampling media and, initially, to improve the elemental coverage and method detection limits. The project was carried out in conjunction between DustScan Ltd and the School of Earth and Environmental Sciences (SEES) at the University of Portsmouth. The new adhesive has similar transparency, tack and UV-resistance to the original but can be dissolved in an appropriate solvent. The new design has been tested in the field at a range of UK industrial sites as well as in a comprehensive bench testing programme. In the field trials, the new sampling media performed well in relation to the original sticky pads. Dust capture and retention were apparently similar and sample handling and processing for image analysis were satisfactory, although transparency was marginally less uniform. In the bench tests, both types of sticky pad were exposed to a known dust at different concentrations and wind speeds in an environmental wind tunnel. Correspondence between the sample media types was good to excellent in relation to the different image quantification methods applied. In addition, an array of elemental analysis tests was performed. NIST standard reference materials were applied to the new sticky pads, then extracted by dissolution of the adhesive and filtration onto 25 mm PTFE filter circles for ICP-MS analysis. Bulk dusts from a number of industrial sources were similarly applied, and analysed before and after application. An unanticipated benefit of the investigation has been the development of a practicable method to determine sampled dust mass in passive directional and deposited environmental dust samples, which has enabled reporting of mass/mass element concentrations in the dust samples after ICP-MS analysis.

• Publication Date: May 14, 2012
• Journal: Environmental forensics: proceedings of the 2011 INEF Conference
• Peer Reviewed: Peer Reviewed
• Pages: 319-331
• Book Title: Environmental Forensics : Proceedings of the 2011 INEF Conference
• ISBN: 9781849733724
• DOI: https://doi.org/10.1039/9781849734967-00319
• Keywords: environmental forensics, source apportionment, dust, ICP-MS, passive sampling, directionality
• Public URL: https://uwe-repository.worktribe.com/output/947232
• Publisher URL: http://dx.doi.org/10.1039/9781849734967-00319
• Contract Date: Jan 1, 2012