Road side effect on lead content in sandy soil

The effect of traffic load on the spatial distribution of lead concentrations in the soil at roadsides and on traffic islands was investigated along a road in Rishon LeZion, Israel. The road comprised two segments that were used during different periods: old, which was in use since 1980; and new, which was opened to traffic in 2004. Soil samples were collected from the upper 0–2 cm soil layer from the roadsides at various distances from the road, and from beneath and between shrubs on the traffic islands. The soil sampling was conducted in 2007 — a few years after the implementation of lead-free fuel — and in 2012. For each soil sample, lead concentration and soil properties associated with lead adsorption (soil organic matter and soil texture) were determined. The amounts of lead around the old road segment were higher than those around the new one. In both sampling years, the lead concentrations at the sides of both road segments were far below the maximum permissible levels for urban and agricultural areas. However, some of the sampling points on the traffic islands of the old road showed lead contamination. Small, non-significant differences in soil lead levels were found at differing distances from the road. Lead-concentration depletion rates of about 1–7 mg kg−1 yr−1 were indicated. Within the traffic islands, the samples collected beneath shrubs contained higher lead concentrations than those collected between shrubs. Soil organic matter levels of <1.5% did not affect the lead concentrations, whereas those above 1.5% showed a strong positive correlation.