Portable X-ray fluorescence spectroscopy is now widely used in almost any field of geoscience. Handheld XRF analysers are easy to use, and results are available in almost real time anywhere. However, the results do not always match laboratory analyses, and this may deter users. Rather than analytical issues, the bias often results from sample preparation differences. Instrument setup and analysis conditions need to be fully understood to avoid reporting erroneous results. The technique’s limitations must be kept in mind. We describe a number of issues and potential pitfalls observed from our experience and described in the literature. This includes the analytical mode and parameters; protective films; sample geometry and density, especially for light elements; analytical interferences between elements; physical effects of the matrix and sample condition, and more. Nevertheless, portable X-ray fluorescence spectroscopy (pXRF) results gathered with sufficient care by experienced users are both precise and reliable, if not fully accurate, and they can constitute robust data sets. Rather than being a substitute for laboratory analyses, pXRF measurements are a valuable complement to those. pXRF improves the quality and relevance of laboratory data sets.

We examined the national mine waste registries from seven European countries, created to fulfil the requirements of the “Mine Waste Directive” (2006/21/EC), for their potential use as an initial source of information for the valorisation of specific mine waste deposits for their resource recovery. A set of parameters for mine waste valorisation was defined and divided into three groups: the “basic”, the “metal-centric” and the “material-centric” group. The “basic” group of 19 parameters considers properties of the mine waste deposit, including the location, history, homogeneity and quantity, among others, while the other two groups relate to the two desired material recovery types. The “metal-centric” group of parameters contains the six parameters needed to preliminarily assess the potential to valorise mine waste for metal extraction, while the “material-centric” group contains the nine parameters needed to consider the use of mine waste for the production of different construction materials. National mine waste registries from Slovenia, France, Spain, Italy, UK, Hungary and Portugal were reviewed to determine whether they contain information about each of the parameters. In line with the objectives of the Mine Waste Directive, the national mine waste registries were developed to reduce or prevent environmental damage, and not to enable resource recovery from mine waste. The registries contain most of the information for the parameters in the “basic” group, less information for the parameters in the “metal-centric” group and almost no information to define the parameters in the “material-centric” group. The conclusion is that national mine waste registries could serve only as an initial source of information, and more detailed information must be obtained from other sources. This misses an opportunity to see these sites as a resource, and not only as a potential source of pollution, given the urgent need to find alternative stocks of metals within the EU (European Union).

The sustainable management of dredged waterway sediments requires on-site determination of the main pollutants to facilitate their safe reuse or treatment. Portable X-ray fluorescence (pXRF) is commonly used for similar applications with contaminated soil, but the high water content of dredged sediments precludes any application of standard methods. Measurements for Pb, Zn, Cu and As were performed on-site on raw wet sediments with 50 to 70 % water contents during dredging or mapping operations. These results, although two or three times lower than laboratory analyses on the same samples, were found to be related to absolute concentrations closely enough to rank samples. In order to investigate further the feasibility of field analyses on wet sediments, partial dehydration methods were tested. The most efficient technique is based on a hand press. It is simple and quick enough to be used on dredging boats during operations and produces sample pellets with 30 to 50 % water contents. The relationship between pXRF measurements on these pellets and laboratory analyses was found to be sufficiently linear to calculate estimated concentrations. Potential differences were found to be less than 20 % for Pb and Zn. Higher differences for Cu were due to very low concentrations, within twice the limit of detection (LOD). Some limitations were observed. The water content in pellets is variable depending on the sediment type or matrix. The correction factors vary between the measured elements and they may also vary with matrix chemistry. However, Pb-Zn-Cu-As concentrations were ranked and evaluated accurately and the geochemical signatures of the samples were preserved. We demonstrated that, with a simple partial dehydration procedure, pXRF measurements can be reliably related closely enough to absolute concentrations to make field decisions for sediment management. Since the approximately linear relationships between measurements on semi-wet samples and laboratory analyses are matrix- and site-dependent, they must be recognised before using pXRF on wet samples for decision-making.

The Kirki project aimed to identify, among the mining waste abandoned at a mine and processing plant, the most critical potential pollution sources, the exposed milieus and the main pathways for contamination of a littoral area. This was accompanied by the definition of a monitoring network and remedial options. For this purpose, field analytical methods were extensively used to allow a more precise identification of the source, to draw relevant conceptual models and outline a monitoring network. Data interpretation was based on temporal series and on a geographical model. A classification method for mining waste was established, based on data on pollutant contents and emissions, and their long-term pollution potential. Mining waste present at the Kirki mine and plant sites comprises (A) extraction waste, mainly metal sulfide-rich rocks; (B) processing waste, mainly tailings, with iron and sulfides, sulfates or other species, plus residues of processing reagents; and (C) other waste, comprising leftover processing reagents and Pb—Zn concentrates. Critical toxic species include cadmium and cyanide. The stormy rainfall regime and hilly topography favour the flush release of large amounts of pollutants. The potential impacts and remedial options vary greatly. Type C waste may generate immediate and severe chemical hazards, and should be dealt with urgently by careful removal, as it is localised in a few spots. Type B waste has significant acid mine drainage potential and contains significant amounts of bioavailable heavy metals and metalloids, but they may also be released in solid form into the surface water through dam failure. The most urgent action is thus dams consolidation. Type A waste is by far the most bulky, and it cannot be economically removed. Unfortunately, it is also the most prone to acid mine drainage (seepage pH 1 to 2). This requires neutralisation to prevent acid water accelerating heavy metals and metalloids transfer. All waste management options require the implementation of a monitoring network for the design of a remediation plan, efficiency control, and later, community alert in case of accidental failure of mitigation/remediation measures. A network design strategy based on field measurements, laboratory validation and conceptual models is proposed.