Abstract
The emission of toxic compounds by increasing anthropogenic activities affects human health and the environment. Heavy road traffic and mining activities are the major anthropogenic activities contributing to the presence of metals in the environment. The release of palladium (Pd), platinum (Pt), and rhodium (Rh) into the environment increases the levels of contamination in soils, road sediments, airborne particles, and plants. These Pd, Pt, and Rh in road dusts can be soluble and enter aquatic environment posing a risk to environment and human health. The aim of this study is to determine the levels of Pd, Pt, and Rh with spectroscopy and voltammetric methods. Potential interferences by other metal ions (Na(I), Fe(III), Ni(II), Co(II)) in voltammetric methods have also been investigated in this study. At all the sampling sites very low concentrations of Pd, Pt, and Rh were found at levels that range from 0.48 ± 0.05 to 5.44 ± 0.11 ng/g (dry weight (d.wt)) for Pd(II), with 17.28 ± 3.12 to 81.44 ± 3.07 pg/g (d.wt) for Pt(II), and 14.34 ± 3.08 to 53.35 ± 4.07 pg/g (d.wt) for Rh(III). The instrumental limit of detection for Pd, Pt, and Rh for Inductively Coupled Plasma Quadrupole-based Mass Spectrometry (ICP-QMS) analysis was found to be 3 × 10−6 µg/g, 3 × 10−6 µg/g and 1 × 10−6 µg/g, respectively. In the case of voltammetric analysis the instrumental limit of detection for Pd(II), Pt(II), and Rh(III) for differential pulse adsorptive stripping voltammetry was found to be 7 × 10−8 µg/g, 6 × 10−8 µg/g, and 2 × 10−7 µg/g, respectively. For the sensor application, good precision was obtained due to consistently reproduced the measurements with a reproducibility of 6.31% for Pt(II), 7.58% for Pd(II), and 5.37% for Rh(III) (n = 10). The reproducibility for ICP-QMS analysis were 1.58% for Pd(II), 1.12% for Pt(II), and 1.37% for Rh(III) (n = 5). In the case of repeatability for differential pulse adsorptive stripping voltammetry (DPAdSV) and ICP-QMS, good standard deviations of 0.01 for Pd(II); 0.02 for Pt(II), 0.009 for Rh(III) and 0.011 for Pd, 0.019 for Pt and 0.013 for Rh, respectively.
Highlights
Platinum (Pt), palladium (Pd), and rhodium (Rh) ( referred to as platinum group metals (PGMs)) are released into the environment by anthropogenic activities such as road traffic, hospitals, and mining industries [1]
Roadside dust and soil samples were collected in the Western Cape Province at the Bottelary Road (BOT) close to Stellenbosch and at the Old Paarl Road (OP) close to Klapmuts, outside Stellenbosch (Figure 1)
It should be noted that the total concentrations of Pt, Pd, and Rh in the soil and dust samples were determined with Inductively coupled plasma quadrupole mass spectrometry (ICP-QMS) analysis, since the technique was not set-up to determine the different oxidation states of Pt, Pd, and Rh during this analysis
Summary
Platinum (Pt), palladium (Pd), and rhodium (Rh) ( referred to as platinum group metals (PGMs)) are released into the environment by anthropogenic activities such as road traffic, hospitals, and mining industries [1]. The most serious problems of road traffic are the emissions of toxic substances such as oxides of sulfur, carbon monoxide, nitrogen oxides, aldehydes (formaldehydes, acetaldehyde and benzaldehyde), hydrocarbons (alkanes, alkenes and alkynes), and heavy metals into the environment. The emission of air pollutants associated with road. Environments 2018, 5, 120 traffic (e.g., carbon monoxide (CO), nitrogen oxides (NOx), and hydrocarbons (HCs)) have decreased significantly from 35% to 24% depending on the type of pollutant, which is due to the introduction of exhaust catalysts [2,3]. The disadvantage of using exhaust catalysts containing Pt, Pd, and Rh, is the release into the environment. Pd, and Rh are mainly emitted as fine suspended particulate matter from vehicle exhaust emissions
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