Platinum-Group Elements in Urban Fluvial Bed Sediments—Hawaii
Results from a detailed examination of the abundance, spatial variability and grain-size fractionation of platinum-group elements (PGEs; iridium, Ir; palladium, Pd; platinum, Pt; and
rhodium, Rh) in bed sediments of an urban stream in Honolulu (Hawaii, USA) indicate significant contamination of Pd, Pt, and Rh. PGE concentrations in sediments located in close
proximity to storm drains followed the sequence of Pt (10.3–24.5 ng/g) > Pd (5.9–12.6 ng/g) > Rh (0.82–2.85 ng/g) > Ir
(0.11–0.23 ng/g). From a contamination perspective, enrichment ratios followed
the sequence of Rh (25.3) ≫ Pd (6.9) = Pt (6.8) ≫ Ir (2.3). Iridium was primarily geogenic in origin, while the remaining PGEs indicated significant anthropogenic contamination.
Attrition of the PGE-loaded three-way catalytic converters and their release to the road environment is the most likely source of PGEs in the stream sediments examined. PGE enrichment
of bed sediments likely resulted from direct transport of sediment-associated road runoff via storm drains. Preliminary work on grain-size partitioning showed preferential enrichment
and mass loading of Pd, Pt, and Rh in grain-size fractions ranging from 63 to 1,000 μm. Data from this study have direct implications for contaminant transport, and sediment source
identification in urban catchments. Rhodium, in particular, emerged as an element potentially useful for sediment fingerprinting.
Sutherland, RA, DG Pearson, CJ Ottley, AD Ziegler. 2015. Platium-Group Elements in Urban Fluvial Bed Sediments--Hawaii. In F. Zereini and C.L.S. Wiseman (eds.),
Platinum Metals in the Environment, Springer-Verlag: Berlin, Heidelberg. DOI 10.1007/978-3-662-44559-4_12).
Accumulation of potentially toxic elements in road deposited sediments in Singapore
Road deposited sediments (RDS) are a valuable environmental medium for characterizing contaminant levels in urban areas; and their associated potentially toxic elements (PTEs) can directly impact both human and aquatic health. In this study, RDS were collected from 15 co-located industrial and residential roads throughout Singapore to determine the effect of land use on contaminant levels. A second pilot study was designed to quantify the efficiency of road sweeping in removing different RDS grain size fractions from industrial and residential roads. The fine fraction (<63 mm) of all RDSs was analyzed for over 40 elements. Eleven elements that reflect geogenic and anthropogenic sources were examined in detail (Al, Co, Cr, Cu, Fe, Ni, Pb, Sb, Sc, Si, and Zn). Industrial RDS had statistically higher concentrations of Co, Cr, Fe, and Ni than residential RDS. Potentially toxic elements Cu, Pb, Sb, and Zn were enriched >10-fold at all locations compared to upper continental crust values. Concentrations of Cu, Pb and Zn exceeded aquatic sediment probable effect concentration levels, suggesting they could generate a toxic response in bottom-dwelling aquatic organisms. Traffic was equally heavy at both industrial and residential sites, but large trucks and machinery comprised a larger proportion of the traffic in the industrial areas. Traffic was not significantly correlated with the PTE (i.e., Cu, Pb, Sb and Zn) concentrations. Plausible anthropogenic contaminant sources include vehicles (e.g., brake and tire wear, vehicle emissions) and several industrial activities including metal works, oil processing, and waste incineration. Street sweeping was effective in removal of large organic debris and inorganic RDS, but it was ineffective in removing the geochemically important fraction, i.e., <125 mm.
Yuen, JQ, P Olin, HS Lim, SG Benner, RA Sutherland, AD Ziegler. 2012. Accumulation of potentially toxic elements in road deposited sediments in residential and light industrial neighborhoods in Singapore. Journal of Environmental Management 101: 151-163
Road-deposited sediments in an urban environment
Sediments stored in urban drainage basins are important environmental archives for assessing contamination. Few studies have examined the geochemical fractionation of metals in individual grain size classes of solid environmental media. This is the first study of road sediments to quantify the mass loading of Al, Cu, Pb, and Zn in individual grain size classes (<63 m to 1000–2000 m) and partition contributions amongst four sequentially extracted fractions (acid extractable, reducible, oxidizable, and residual). The optimized BCR sequential extraction procedure was applied to road sediments from Palolo Valley, Oahu, Hawaii. Road sediments from this non-industrialized drainage basin exhibited significant enrichment in Cu, Pb, and Zn. Metal mass loading results indicate that the <63 m grain size class dominated almost all fraction loads for a given element. The residual fraction dominated the Al loading for this geogenic element. The reducible fraction, associated with Fe and Mn oxides, was the most important component for Cu, Pb, and Zn loading. These results have direct implications for environmental planners charged with reducing sediment-associated contaminant transport in urbanized drainage basins.
Sutherland RA, FMG Tack, AD Ziegler 2012. Road-deposited sediments in an urban environment: A first look at sequentially extracted element loads in grain size fractions.
Journal of Hazardous Materials 225–226:
Metal extraction from road-deposited sediments
Nine partial decomposition procedures and a total digestion treatment were applied to road-deposited sediments. The objective was to define a parsimonious, time-efficient decomposition procedure that (1) has limited impact on the alumnio-silicate matrix and/or refractory-associated fractions, (2) has metal recoveries independent of CaCO3 content, and (3) produces high anthropogenic signals for known contaminants (e.g., Cu, Pb and Zn). The 9 digestions varied from weak single reagents (0.11 M acetic acid) to strong multi-step procedures (BCR 3-step plus aqua regia). Eight metals were examined: Al, Co, Cu, Fe, Mn, Ni, Pb, and Zn. Cold (room temperature) 0.5 M HCl shaken over a 1-h period with a solid-to-solution ratio of 1 g:20 ml, was judged superior based on the defined criteria. This simple, rapid treatment had limited impact on the residual matrix (mean and 95% confidence interval for Al recovery was 61%); recoveries of all elements examined were independent of CaCO3 content; the treatment produced high mean extraction efficiencies for Cu (589%), Pb (845%), and Zn (737%), and produced high anthropogenic signals. Thus, dilute HCl can be widely recommended as an optimal partial decomposition procedure for assessing non-residual fractions of complex solid media.
Sutherland, RA, FMG Tack, AD Ziegler, JO Bussen. 2004. Metal Extraction from Road Sediments Using Nine Partial Decomposition Procedures. Applied Geochemistry 19:947-955. doi:10.1016/j.apgeochem.2003.11.002