Retention Capacity and Environmental Mobility of Pb in Soils along Highway Corridor

Abstract

Although lead (Pb) emissions have dropped drastically with the phase-out of tetra-ethyl lead (TEL) as a fuel additive, Pb deposited along highway corridors continues to be of concern because of its toxicity. This paper provides comprehensive data on the extent and distribution of Pb in roadside soils, Pb interaction with soils as a function of soil composition, the retention capacity of soil based on batch adsorption tests, the retention mechanism of Pb using selective sequential extraction, the potential for mobility using batch desorption tests with simulated rain and winter road salt, and column leach tests. Highway soils on high-traffic sections near Burnaby, Canada were found to have Pb accumulations up to 1628 mg/kg soil. Contamination was mainly in the top 0.3 m, with concentrations rapidly decreasing to the background level at a depth of 0.6 m. The top layer contained more organic material and had a high adsorption capacity. Highway soils were found to have 3-10 times higher Pb adsorption capacities than the amount currently deposited. Selective sequential extraction indicated low exchangeable Pb in highway soils. Batch desorption tests with leaching solutions of H 2 O (pH 5.5), HNO 3 solution (pH 4.0) and aqueous NaCl solution (0.17 M) indicate low likelihood of significant leaching. Selective sequential extraction, leachate extraction and desorption tests show that Pb has limited mobility in highway soil.

Heavy metal pattern and solute concentration in soils along the oldest highway of the world – the AVUS Autobahn

“…It is well documented that the heavy metal contents in roadside soils decrease with the distance to the road and with soil depth (Motto et al 1970;Harrison et al 1985;Sansalone and Buchberger 1997;Turer and Maynard 2003;Li 2005). At the study site, this relation only applied to Pb at soil depth 0-10 cm, but even here, the median at 5 m was found to be smaller than at 10 m from the edge of the road (Fig.…”

“…Generally, the concentrations of pollutants decrease with distance from the road, with the soil depth and with decreasing traffic intensity (e.g. Dierkes and Geiger 1999;Turer and Maynard 2003;Li 2005). Heavy metals are the pollutants of greatest concern because of their longterm toxicity for microorganisms, plants, animals and human nature.…”

“…The improvement of existing roads and the construction of new ones could cause high leaching of heavy metals and low pH as well as a low sorption capacity and a small fraction of organic matter in the reassembled soils. There are only few measurements of pollution patterns in combination with leaching characteristics of highly polluted roadside soils (Norrström and Jacks 1998;Bäckström et al 2004b;Li 2005;Hjortenkrans et al 2008;Saeedi et al 2009). …”

Forest soils adjacent to urban interstates: Soil physical and chemical properties, heavy metals, disturbance legacies, and relationships with woody vegetation

“…4). Many studies have shown heavy metal concentrations to be highest in surface soils compared with sub-surface soils (Chow 1970;Lagerwerff and Specht 1970;Li 2006;Turer et al 2001;Ward et al 1975). Copper, lead, and zinc demonstrate low mobility in soils (Al-Shayeb 2003;Harrison et al 1985).…”

The effect of intensive traffic on soil and vegetation risk element contents as affected by the distance from a highway

“…The risk element accumulation in the soils proved elevated contents of these elements along the highways decreasing with the distance from the roadway. However, the knowledge of the element mobility in the soils is necessary for the estimation of potential risk of soil elements for their uptake by plants (Li 2006). Sequential extraction procedures estimated the element bioavailability in urban dust and in highway soils in decreasing order Cd > Zn > Pb > Cu (Li et al 2001).…”