In the last thirty years, portable X-ray fluorescence (pXRF) has grown from prototypes to being a key technique for field geochemical analyses, especially for mining and environmental applications. This technology provides real-time or near real-time decision support for operational field decisions (exploration, mining, site remediation or waste management), provides a cost-saving alternative to classical laboratory analysis programs, and deals efficiently with remote or harsh field conditions. The ability to rapidly collect a large number of samples and replicate analyses facilitates acquisition of higher data density compatible with geostatistics.pXRF can be used profitably for sample screening and selection tasks, dynamic sampling plans based on field observations and measurements, grid mapping of a site and determining relative element abundance. In waste management and remediation, pXRF is used to identify unknown waste composition, and verify waste loads before disposal or treatment.In all applications, having robust QA/QC plans and systematic laboratory controls on selected samples are essential for ensuring reliable measurements. The best overall results are usually achieved through a clever combination of field (pXRF) and lab data, with pXRF providing the bulk of the data at low cost, on larger data sets and potentially with better reliability than lab-based campaigns based on a limited number of samples.
ABSTRACT:The sustainable management of dredged waterway sediments requires on-site determination 8 of the main pollutants to facilitate their safe reuse or treatment. Portable X-ray fluorescence (pXRF) is 9 commonly used for similar applications with contaminated soil, but the high water content of dredged 10 sediments precludes any application of standard methods. Measurements for Pb, Zn, Cu and As were 11 performed on-site on raw wet sediments with 50 to 70% water contents during dredging or mapping 12 operations. These results, although two or three times lower than laboratory analyses on the same samples, 13were found to be related to absolute concentrations closely enough to rank samples. In order to investigate 14 further the feasibility of field analyses on wet sediments, partial dehydration methods were tested. The most 15 efficient technique is based on a hand press. It is simple and quick enough to be used on dredging boats 16 during operations and produces sample pellets with 30 to 50% water contents. The relationship between 17 pXRF measurements on these pellets and laboratory analyses was found to be sufficiently linear to calculate 18 estimated concentrations. Potential differences were found to be less than 20% for Pb and Zn. Higher 19 differences for Cu were due to very low concentrations, within twice the limit of detection (LOD). Some 20 limitations were observed. The water content in pellets is variable depending on the sediment type or matrix. 21The correction factors vary between the measured elements and they may also vary with matrix chemistry. 22However, Pb-Zn-Cu-As concentrations were ranked and evaluated accurately and the geochemical 23 signatures of the samples were preserved. 24We demonstrated that, with a simple partial dehydration procedure, pXRF measurements can be reliably 25 related closely enough to absolute concentrations to make field decisions for sediment management. Since 26 the approximately linear relationships between measurements on semi-wet samples and laboratory analyses 27 are matrix-and site-dependent, they must be recognised before using pXRF on wet samples for decision 28 making. 29
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 chemical and isotopic compositions of river and groundwater reflect the different natural processes that provide chemical elements to the dissolved load, i.e. mainly the weathering of rocks and soils, atmospheric inputs and anthropogenic disturbances.This study reports on the geochemistry of surface-and groundwater along a part of the Subarnarekha River system (north-eastern India) collected during monsoon and dry season, during a monitoring program aimed at evaluating impacts of mining and metallurgy on the river system.The aquifer is of fracture type and the seasonal behaviour, groundwater flow conditions and pollutant transfer were observed through a network of 69 wells with typical depths of 50 meters.Geochemical observations, including major cations and anions, trace element concentrations and isotopic tracing (stable isotopes of the water molecule, strontium isotopes) come to conclusions on the origin and the relationships between the surface-and groundwater in the studied catchment.A large range of salinities is observed in surface-and groundwater, both for dry or wet periods.Surface water samples plot within the field HCO 3 -Ca during both water stages. Most groundwater samples plot within the field of Ca-SO 4 water type and HCO 3 -Ca water type. This reflects the high Ca input in groundwater, other than weathering. Such inputs could be related to (i) carbonate amendments used in agricultural practices and (ii) residues from ore processing.
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