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[A research on the quality of soil and groundwater along motorways in forest regions.]

Verkennend onderzoek naar de kwaliteit van bodem en grondwater langs snelwegen in bosgebieden


A research program has been designed to determine the environmental quality of soil and groundwater along motorways. Samples of forest litter, soil and shallow groundwater were taken at five motorway roadside sites during the period October-November 1991. The samples were taken at two distances from the motorway ; nearby (approximately 8 meters) and far away (approximately 80 meters). Finding higher soil and groundwater concenstrations of traffic-derived compounds at the shorter distance was anticipated. The samples were analyzed for heavy metals (cadmium, lead, nickel, copper and zinc). PAHs and VAHs (benzene, toluene, xylene and ethylbenzene), Additionally, the chloride concentration in groundwater was analyzed. In the forest litter the soil concentrations of lead, copper, zinc and most PAHs were significantly higher near the motorway ; in the underlying sandy soil this was found only for lead and some PAHs. In particular, the lead and PAH soil concentrations in the forest litter frequently exceeded the background levels. Only the chloride groundwater concentrations were found to be significantly higher at the shorter distance as the Dutch climate requires using de-icing salt during wintertime. Traffic therefore has a certain influence on the soil and groundwater quality along motorways. To find a significant distance-related effect on a national scale more sites have to be sampled.

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