Field Portable X-ray Fluorescence Spectrometer Research Articles

Relevance of using portable X-ray fluorescence to identify gold hyperaccumulator plants

Field Portable X-Ray Fluorescence (FPXRF) was investigated as an alternative analysis tool for the detection and quantification of gold in hyperaccumulator plants in the field. First, synthetic gold standards were prepared with materials chosen to best simulate plant material, using microcrystalline cellulose (mcc) or ash by adding known amounts of gold. Powder samples were obtained containing gold in amounts ranging from 10 to 1000 ppm of gold. They were analysed, as well as blank samples of mcc and ash, using a NITON xl3t GOLDD+ FPXRF spectrometer in AllGeo and Soil modes with an analysis time of 60 s. Results were compared to Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) analysis of the synthetic gold standards after digestion in aqua regia. Gold was detected and accurately quantified in synthetic gold standards containing more than 25 ppm of gold in AllGeo mode. At lower concentration, results were much more inaccurate, with no gold being detected at 10 ppm. In Soil mode, similar results to AllGeo mode were obtained with mcc synthetic standards. However, with ash synthetic standard gold quantification was very poor over the whole concentration range and gold was detected in the blank ash sample, which was confirmed as a false positive by the subsequent ICP analysis. Samples of Phyllanthus stipulatus, suspected gold hyperaccumulators, collected on gold-bearing sites in French Guiana were then analysed following the same protocol. The same false positive phenomenon was observed in some of them, with gold being detected by FPXRF in Soil mode but not by ICP analysis. Furthermore, analysis of the FPXRF spectra revealed that none of the characteristic gold emission ray was present. This false positive was attributed to an interference caused by zinc, present in significant amount in the ash of the synthetic standard and the collected plants.

Laboratory comparison of field portable X-ray fluorescence spectrometer (FP-XRF) and inductively coupled plasma mass spectrometry (ICP-MS) for determination of airborne metals in stainless steel welding fume

Welding fume is a common exposure in occupational settings. Gravimetric analysis for total particulate matter is common; however, the cost of laboratory analyses limits the availability of quantitative exposure assessment for welding fume metal constituents in occupational settings. We investigated whether a field portable X-ray fluorescence spectrometer (FP-XRF) could provide accurate estimates of personal exposures to metals common in welding fume (chromium, copper, manganese, nickel, vanadium, and zinc). The FP-XRF requires less training and is easier to deploy in many settings than traditional wet laboratory analyses. Filters were analyzed both by FP-XRF and inductively coupled plasma mass spectrometry (ICP-MS). We estimated the FP-XRF limit of detection for each metal and developed a correction factor accounting for the non-uniform deposition pattern on filter samples collected with an Institute of Medicine (IOM) inhalable particulate matter sampler. Strong linear correlation was observed for all metals (0.72<r < 0.96). The median percent bias for chromium and nickel was less than 15%. The linear slope between the two methods for some metals (copper, manganese, and zinc) was greater than 1, indicating that the FP-XRF overestimated metal mass (median percent bias for vanadium was the largest at 94%), but the linearity of the response suggests that appropriate correction factors could be developed.

Distribution of heavy metals in soils from abandoned dump sites in Kumasi, Ghana

This study investigated the heavy metal content and the extent of pollution in soils from abandoned dump sites in Kumasi, Ghana. Concentrations of heavy metals in the 70 soil samples were determined using a Niton XL3t GOLD field portable X-ray fluorescence spectrometer and confirmed on an Agilent 7800 inductively coupled plasma-mass spectrometer. Mercury was determined with a Lumex mercury analyzer. Mean concentrations of metals in soils were in the order: Zn (166 mg/kg). Cr (67 mg/kg) > Cu (32 mg/kg), Ni (22 mg/kg) > Pb (11 mg/kg) Cd (8.9 mg/kg) > As (4.2 mg/kg) > Hg (0.04 mg/kg) for Kronum; and Zn (558 mg/kg), Cu (347 mg/kg), Pb (288 mg/kg) > Cr (77 mg/kg) > Ni (35 mg/kg) > As (11 mg/kg) > Cd (3.0 mg/kg) > Hg (0.19 mg/kg) for Amakom. Pollution indices (geo-accumulation, contamination factor, pollution load and potential ecological risk) indicated very high contamination for arsenic, cadmium and lead at Kronum and arsenic, cadmium, copper, lead and zinc at Amakom. Mercury recorded the least level of pollution for both dump sites. Regular monitoring of these abandoned dump sites is required. Remediation programs in these sites should also be instituted.

Accumulation and bioaccessibility of toxic metals in root tubers and soils from gold mining and farming communities in the Ashanti region of Ghana

ABSTRACT The presence of metal contaminants in agricultural soils and subsequent uptake by food crops can pose serious human health risk. In this study, we assessed the levels of toxic metals – arsenic, chromium, copper, iron, manganese, nickel, and zinc – in soils and some edible root tuber crops from two gold mining and two non-mining communities in Ghana to evaluate the potential human health risks associated with exposure to these metals. Concentrations of the metals in 154 soil and edible root tuber samples were analyzed using field portable x-ray fluorescence spectrometer prior to confirmation by inductively coupled plasma mass spectrometry. Bioaccessibility of the metals was determined using an in vitro physiologically based extraction technique. Concentrations of the metals were generally higher in the gold mining communities than in the non-mining communities. The contamination indices indicated low to moderate contamination of the soil and food crops. Bioaccessibility for the metals varied from 1.7% (Fe) to 62.3 (Mn). Overall, the risks posed by the metals upon consumption of the tubers were low.

Identification of commercial and recreational vessels coated with banned organotin paint through screening of tin by portable XRF.

The most effective biocide used historically in antifouling paints is tributyltin (TBT). However, due to its extreme toxicity to non-target organisms and its persistence in the environment, the use of TBT and other organotin compounds (OTCs) was restricted in EU on leisure boats and ships in 1989 and 2003, respectively. Nevertheless, studies worldwide still report TBT to be released from both ships and leisure boats. Here, we present a new application for a field portable X-ray fluorescence spectrometer (XRF) used for screening for organotin paint through measurements of tin (Sn) on leisure boats and ships. Measurements on ships built after the restrictions showed concentrations of up to 68 μg Sn/cm2, likely due to impurities of inorganic Sn, as shown through chemical analysis of 21 organotin-free paints. A threshold value of 100 μg Sn/cm2 is suggested, where exceedance indicates presence of OTCs. Screening with the XRF method showed 10% of the commercial vessels (n = 30) and 23-29% of leisure boats (n = 693, investigated in this and in a previous study) to hold concentrations exceeding 100 μg Sn/cm2. The XRF technique presented here provides a useful tool for quick screening and identification of vessels holding banned organotin paint.

Soil Contaminant Concentrations at Urban Agricultural Sites in New Orleans, Louisiana: A Comparison of Two Analytical Methods

Along with the many benefits of urban agriculture comes the possible exposure to contaminants not typically seen in rural soils. Through the use of standard laboratory analyses (ICP-AES and CVAAS) and a field-portable X-ray fluorescence spectrometer (XRF) calibrated for soil analysis, this study quantified contamination levels at urban agricultural sites throughout New Orleans, Louisiana. The results of the standard laboratory analyses were compared to the results from the XRF. We collected soil samples at 27 urban and suburban farm and garden sites from the Greater New Orleans area. We analyzed the soil samples for arsenic, cadmium, chromium, cobalt, copper, mercury, lead, nickel, and zinc using the XRF and standard methods. Most sites had median con­centrations significantly below Louisiana’s soil standards. Paired soil samples showed XRF results were significantly higher than laboratory results for all metals but copper. Only lead (ρ=0.82, p<0.0001) and zinc (ρ=0.78, p=0.0001) were highly correlated. Poor correlation of results between XRF and standard methods make the standard methods preferred. See the press release for this article.

Distribution and ecological risks of toxic metals in the topsoils in the Kumasi metropolis, Ghana

The distribution, and ecological risks due to toxic metals in topsoils of an urban commercial centre of Kumasi metropolis were determined. Concentrations of heavy metals in the samples were initially screened using field portable X-ray fluorescence spectrometer prior to confirmation on an inductively coupled plasma-mass spectrometer. The results from the two instruments correlated well with high linearity (R2 > 0.70). Concentrations of metals were in the order: Fe (45246.15 mg/kg) > Mn (347.86 mg/kg) > Zn (176.40 mg/kg) > V (173.10 mg/kg) > Cr (125.12 mg/kg) > Pb (53.47 mg/kg) > Ni (43.16 mg/kg) > Cu (39.85 mg/kg) > As (4.59 mg/kg) > Sn (3.69 mg/kg) > Cd (0.46 mg/kg) > Hg (0.28 mg/kg). Multivariate and geostatistical analyses exploring various hazard indices such as geo-accumulation, contamination, pollution load and ecological risks all suggest contamination of the topsoils with toxic metals and that the contamination due to Pb, Cu, Ni, Cr and Zn is mainly derived from anthropogenic origins whereas, As, Hg, Mn, V, Sn and Cd contaminations are attributable mainly to geological and atmospheric depositions. Contamination factor (CF) suggests that the topsoils were considerably contaminated (CF 3–6) with Zn, moderately contaminated (CF 1–3) with Ni, Hg, V, Sn and Cd and least contaminated (CF < 1) with As, Pb, Cu, Cr and Mn. In general, the soils were found to be moderately contaminated (average contamination factor (1 ≤ CF < 3) with toxic metals and may pose both human and ecological risks.

Legacy lead arsenate soil contamination at childcare centers in the Yakima Valley, Central Washington, USA

BackgroundFrom the early 1900s to the 1950s, Yakima Valley orchards were commonly treated with lead arsenate (LA) insecticides. Lead (Pb) and arsenic (As) soil contamination has been identified on former orchard lands throughout Central Washington and pose a threat to human health and the environment. ObjectivesThe levels of Pb and As in soil and interior dust at participating childcare centers in the Upper Yakima Valley (Yakima County), Washington were sampled to explore exposure potential for young children. MethodsChildcare center soils were collected from two soil depths, homogenized, and analyzed in bulk by a field-portable X-ray fluorescence spectrometer (XRF). Interior dust wipes samples were collected from at least two locations in each facility. All soil samples >250 mg/kg Pb and/or >20 As mg/kg were sieved to 250 μm, tested by XRF a second time, and analyzed via acid digestion and inductively coupled plasma mass spectrometry (ICP-MS) analysis. ResultsBulk and sieved XRF results, as well as ICP-MS to XRF results were strongly correlated. Maximum Pb and As XRF results indicated that 4 (21%) and 8 (42%) of the 19 childcare centers surveyed exceeded the regulatory standard for Pb and As, respectively. Historic land use was significantly associated with elevated Pb and As levels. Interior dust loadings were below United States Environmental Protection Agency (EPA) guidelines. ConclusionsChildcare centers are areas of intensive use for children and when coupled with potential residential exposure in their homes, the total daily exposure is a potential hazard to children.

Can field portable X-ray fluorescence (pXRF) produce high quality data for application in environmental contamination research?

This research evaluates the analytical capabilities of a field portable X-ray fluorescence spectrometer (pXRF) for the measurement of contaminated soil samples using a matrix-matched calibration. The calibrated pXRF generated exceptional data quality from the measurement of ten soil reference materials. Elemental recoveries improved for all 11 elements post-calibration with reduced measurement variation and detection limits in most cases. Measurement repeatability of reference values ranged between 0.2 and 10% relative standard deviation, while the majority (82%) of reference recoveries were between 90 and 110%. Definitive data quality, the highest of the US EPA's three level quality ranking, was achieved for 15 of 19 elemental datasets. Measurement comparability against inductively coupled plasma atomic emission spectrometry (ICP-AES) values was excellent for most elements (e.g, r2 0.999 for Mn and Pb, r2 > 0.995 for Cu, Zn and Cd). Parallel measurement of reference materials revealed ICP-AES and ICP-MS measured Ti and Cr poorly when compared to pXRF. Individual recoveries of soil reference materials by both ICP-AES and pXRF showed that pXRF was equivalent to or better than ICP-AES values for all but two elements (Ni, As). This study demonstrates pXRF as a suitable alternative to ICP-AES analysis in the measurement of Ti, Cr, Mn, Fe, Cu, Zn, Sr, Cd, and Pb in metal-contaminated soils. Where funds are limited, pXRF provides a low-cost, high quality solution to increasing sample density for a more complete geochemical investigation.

Metal contamination at recreational boatyards linked to the use of antifouling paints-investigation of soil and sediment with a field portable XRF.

The application of a field portable X-ray fluorescence spectrometer (FPXRF) to measure Cu, Zn, and Pb in soil and sediments at recreational boatyards by Lake Mälaren in Sweden was investigated. Confirmatory chemical analysis on freeze-dried samples shows that, ex situ, the FPXRF produces definitive level data for Cu and Zn and quantitative screening data for Pb, according to USEPA criteria for data quality. Good agreement was also found between the ex situ measurements and the in situ screening. At each of the two studied boatyards, >40 in situ soil measurements were carried out. Statistical differences in soil concentration based on land use were consequently found: the areas used for boat storage and maintenance were significantly higher in Cu and Zn than the areas used for car parking and transportation. The metal pollution in the boat storage areas is therefore shown to be directly linked to hull maintenance activities during which metal-containing antifouling paint particles are shed, end up on the ground, and consequently pollute the soil. In the boat storage areas, the Cu and Zn concentrations often exceeded the national guideline values for soil. In this study, they were also shown to increase with increasing age of the boatyard operation. Pb soil concentrations were only elevated at a few measurement points, reflecting the phasing out of Pb compounds from antifouling products over the past 2 decades. In the surface sediments, concentrations of Cu and Zn were 2–3 times higher compared to deeper levels. No decrease in metal concentration with time was found in the sediments, indicating that boat owners are not complying with the ban of biocide-containing paints in freshwater introduced over 20 years ago.

Application of field portable X-ray fluorescence to the analysis of desert varnish samples in areas affected by coal-fired power plants

Environmental context Rock surfaces are often covered with a dark coating called desert varnish that can capture and retain air pollutants. A field portable X-ray fluorescence spectrometer was used for direct non-destructive analysis of varnished rocks in the fallout zones of two coal-fired power plants. At one power plant where tracer studies had been carried out, the highest concentration of elements including Cr, As, Pb and Zn in the rock varnish samples, coincides with the peak tracer concentration locations. AbstractDesert varnish samples were collected near two coal-fired power plants to determine if the varnish contained a record of recent air pollution. Samples were collected: (1) in the fallout patterns of the shuttered Mohave Power Plant (MPP), located in Laughlin, NV; and (2) near the operating Reid-Gardner Power Plant (RGPP), just east of Las Vegas, NV. Small pieces of varnished rocks were analysed by field portable X-ray fluorescence spectroscopy (FPXRF). Results were obtained for 15 elements: Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Rb, Sr, Zr, Mo, Hg and Pb. The FPXRF data indicate that the elements commonly found in fly ash from coal-fired power plants (e.g. Cr, Zn, As and Pb) had significantly higher concentrations in the rock coatings in relation to the unvarnished substrate rock. For one of the power plants, where tracer plume studies had been carried out, the highest concentrations in the desert varnish coincided with the peak tracer concentration locations. Thus, these elements in desert varnish hold promise for identifying those geographical regions affected by nearby power plants. However, additional samples are required to demonstrate unequivocally that the power plants are indeed the sources of these elements. Overall, it is apparent that desert varnish can be utilised as a passive environmental monitor to investigate recent air pollution (past 20–30 years) and that FPXRF can be used as a surveying tool to obtain multi-element data from a large number of samples.

Evaluation and calibration of a Field Portable X-Ray Fluorescence spectrometer for quantitative analysis of siliciclastic soils and sediments

This paper documents the evaluation of a Field Portable X-Ray Fluorescence spectrometer (FP-XRF) as a bench top laboratory unit with regard to quantitative elemental analysis of siliciclastic soils and sediments. With the end-user in mind, we outline a calibration scheme that offers significant improvement in data quality over the manufacturer's calibration. Our calibration approach is based on Standard Reference Materials (SRMs) as calibration standards, the use of least-squares regression techniques that allow for uncertainty in both x and y data (i.e., type II linear regression), propagation of error with respect to predicted concentrations, and goodness of fit evaluation. Data presented include the repeated analysis of numerous standard reference sediments and soils, which are used to evaluate the instrument response to changes in concentration, signal stability over the course of ∼1 year, and calibration model suitability. We present Hudson River estuary sediment data along with independent confirmatory analyses as a demonstration. Our results for the estuarine sediments are in very good agreement with independent laboratory analyses, indicating that the FP-XRF is comparable to traditional laboratory instrument/analytical techniques, and capable of providing high quality data for numerous elements.

Strategies for the investigation of contaminated sites using field portable x‐ray fluorescence (FPXRF) techniques

The remediation of contaminated land is a potentially complex exercise and is one which requires a sound approach to achieve a degree of remediation which complies with existing legislative guidelines. Current guidelines for the assessment and management of contaminated sites include staged investigations (Qld DoE 1998), which relate to past uses of the site under investigation coupled with a detailed study of the total extent of chemical (and other) contamination. In performing these site investigations, it is important that a sound approach is developed to collect, for subsequent chemical analysis, a sufficient set of samples at suitable locations in order to provide relevant information on the degree and extent of the site contamination. In this study an FPXRF spectrometer (NITON, Bedford, USA) was evaluated to assess its value in the sampling, collection and geographic modeling on the extent of a range of contaminant elements including arsenic (As) arising from the operation of a now disused plunge dip. Contamination boundaries and spatial distributions of As were determined both in‐situ and ex‐situ using this portable technique over a number of locations in and around the disused plunge dip site. These values were compared with concentrations found for collected samples using standard USEPA protocols, including ICP‐OES (Inductively coupled plasma ‐ optical emission spectrometry. Spectro, Kleve, Germany) and ICP‐MS (Inductively coupled plasma ‐ mass spectrometry. VG PlasmaQuad, Winsford, UK). A comparative assessment of this approach is presented in terms of recommending an enhanced strategy for future investigations of contaminated sites using such field portable techniques.

Monitoring surface and airborne inorganic contamination in the workplace by a field portable X-ray fluorescence spectrometer

Assessment of a field-portable energy dispersive X-ray fluorescence spectrometer (PXRFS) was carried out to determine its performance characteristics for direct analysis of surface deposits and airborne inorganic contamination collected on millipore filters. Lower limits of detection (LLDs) determined for 18 elements were found to be below the required sensitivity of analysis, one-tenth of the occupational exposure limit, with the exception of Pb and Cd. Precision of determinations above the LLD indicated that the standard deviation in analysis was less than 10%. Results of PXRFS analyses of millipore filters used in sampling airborne contamination agree well with results obtained by a laboratory-based XRF method. Results of monitoring Pb, Cd, As, Hg, Fe, Mn and Ni contamination on workplace surfaces show good correlation between direct monitoring and surface wipe sampling. Levels of contaminants on workplace surfaces were found to vary between 0 and 1200 μg cm −2 on non-textile surfaces; in office areas up to 1458 μg Cd cm −2 , 862 μg Pb cm −2 and 46 μg Hg cm −2 were found on carpets. The findings indicate that the portable XRF monitor can provide rapid on-site analyses of surfaces, filters and powders and thus play a key role in a cost-effective sampling and analysis strategy.