Abstract
Since the industrial revolution pollution has typically been classified according to whether it concerns air, water or noise, the issue of light-pollution now joining these. Pollution, direct or otherwise, causes damage to the living environment. In the present study of moderate to high atomic number media, analysis of major, minor and trace elemental concentrations is shown to be effective via x-ray fluorescence and mass spectroscopy (MS) based methods. Particular choice has been made of two media of highly differing constitution, both of toxicological consequence and each with its own challenges. Metals are prevalent in the widespread environmental emissions that result from the use of motorised vehicles, not least in road dust. Conversely, the metals manifest in Kohl have been analysed as an example of how an absence of regulatory control can allow the unimpeded marketing of personal products of clear human health impact. In conducting such a study, comparison has been made of several sensitive yet convenient sample analysis techniques (XRF, SEM/EDX, ICP-MS and ICP-OES), their relative efficacy being examined. The ICP-based methods provide for quantitative sample analysis while XRF/EDX can provide quantitative and qualitative analysis. The XRF study of Kohl has involved analysis of Pb, Fe and Zn concentrations in 135 samples, obtained from nine randomly selected market outlets (15 aliquots of each brand being represented). Among the published physiological effects of exposure to Pb is replacement of Ca in bones and teeth, making them weak and fragile, other impacts including nephrotoxicity, linked with increased Pb blood levels. While in this study the work on Kohl formed an introduction to elemental analysis, one particular challenge, also one that quickly became apparent but yet notable in terms of its absence from discussion in the literature, was investigation of high concentrations of highly attenuating media. Sample dilution and account of it has been required in arriving at reliable quantification. One desire has been to draw regulator attention to the potentiality of convenient, compact instrumentation and associated methodology, allowing for product screening. For road dust, obtained from a total of 60 locations, analysis has been conducted on particle sizes ranging from < 45 m up to 125 m. Arid climate samples were collected from the campuses of King Saud University, the Kuwait Research Institute and Qatar University, while maritime climate samples were collected from the Surrey University campus. Ttropical climate samples were collected from the campus of the University of Malaya as well as surrounding roads to the Malaysian radiation consultancy company, Asia Lab (now Alypz Sdn. Bhd.). Roadside dirt has been sampled along busy campus roads of universities/research centres in Guildford, Riyadh, Kuwait City, Doha and Kuala Lumpur, satisfying interest in climatic influences as well as vehicle engine size (in the Gulf countries non-commercial vehicle engine capacities tend to be greater than those in the UK or Malaysia, a product of relatively cheap fuel prices). A total of 200 street dust samples have been analyzed, elemental concentrations being reported for Mg, Al, Ti, Mn, Fe, Co, Zr, Mo, Ba, Tl, V, Rd, Pb, Cu, Zn, Ni, Cr, Cd, As, Hg and Au. For all five urban centres, Al, Fe, Mg, and Si values were found to be well above background although concentrations of Ti, Cr and Ba were lower than values reported by others. The concentrations of Pb were relatively low, likely attributable to restrictions on lead in fuel. Au and Ag were detected in low quantities in both Arid and Maritime climates, use being made of the SEM/EDX, appearing at levels unlikely to make economic sense in terms of recovery. Note that elemental loadings are provided in terms of concentrations per unit mass of sample. In general, the elements found in elevated concentrations can all be linked to the wear and tear of motor parts as debris. For the Guildford samples, obtained at three different times of the year, the main SEM/EDX findings were for Mg, Al, Cr, Ti, Mn, Fe, Co, Cu, Zr, Mo, Ba, Tl, V, Rh, Au and Ag, values ranging from non-detectable (below detection limits), through to from as low as 34.7 E-6 mg/m2 up to as high as 6 E-2 mg/m2. Note that the output provides estimates of elemental loadings per unit area at the sampling site. Using ICP-MS, Guildford concentrations in mg/kg (ppm) have been found for Al, V, Cr, Mn, Fe, Co, Cu, Zn, As, Se, Mo, Cd, Sb, Pb, and U, for samples of mean size < 45 micron. Respective values were 3081, 12.3, 40.2, 333, 14133, 3.5, 70.4, 288, 5.96, 0.400, 2.35, 0.567, 2.77, 78.0, 0.657, results showing particular elevations of Al, Fe, Cu, Zn and Pb. Other toxic metals found in the Guildford and Kuwait samples in different concentrations were V, Ti, Cr, and Ba. For Riyadh and Doha samples four elements have been observed to be particularly prominent: Al, Fe, Mg, and Si, notwithstanding that they all have natural abundance in desert sands. Elemental presence has been seen to be influenced by climatic conditions as well as vehicle engine size. In conclusion, the various techniques offer complementary information on vehicular emission elemental concentrations in urban environments.