Roadside Coniferous Windbreaks as Sinks For Vehicular Lead Emissions

Abstract

The role of a roadside windbreak of white pine trees in modifying the dispersion of vehicular lead emissions was evaluated. The lead content of foliage and twigs of various ages adjacent to and far from the road was analyzed by atomic absorption spectrophotometry. The lead burden of older needles and twigs was consistently greater than that of younger organs, and was greater in samples taken adjacent to than far from the road. The pattern of lead accumulation on mature needles, but not twigs, varied with precipitation prior to sampling. Twigs retained particles more effectively than needles throughout the season; twigs retained about 115% more lead as µg g^-1 and about 2050% more lead as µg cm^-2 than similarly located needles. The lead content of soil beneath the windbreak was compared with that of an adjacent, undisturbed field to assess whether the presence Of the windbreak resulted in lead enrichment of the underlying soil. The soil between the curb and the windbreak contained about 50% more lead than that of the field at a similar distance from the road. Within the windbreak, the soil contained about twice the lead content of the soil in the open field at a similar distance from the curb. Windbreaks function as sinks for vehicular lead emissions and thus decrease their dispersion from roads.