In the early days of gasoline production lead was added to gas because it was found to improve automobile performance, but as technology improved and the health hazards of lead were discovered the use of lead as an additive was phased out. Unfortunately, 50 years of car emissions containing lead has remained in the environment. Northeastern forest soils are being studied by researchers at Dartmouth University for lead pollution and the effects thereof. Dartmouth researchers published a paper on this topic in the Journal of Environmental Quality, discussing areas affected by lead deposits, patterns in deposition and why the patterns may differ throughout the region. It seems that lead easily binds with organic matter, which is obviously abundant on the forest floor and so acts like a sponge, providing plenty of surface area for this large molecule to bind.
The question this research seeks to answer is whether the lead remains in surficial soil or does it migrate to underlying mineral soils, currently 16 forest sites in the northeast are being sampled every 10 years for the past three decades in order to monitor any migration or change. Findings illustrate that 60% of the lead originally found on western sites in Pennsylvania and New York has been lost from the forest floor since 1980, while northern study sites in New Hampshire and Vermont have retained more lead in the organic matter. One explanation for this difference posits the difference in thickness of organic layers between the sites; the forest floor stays warmer in western sites throughout the year which allows for continuous decomposition leading to thinner organic layers remaining in place. Cooler, northern sites have slower decomp rates leaving thicker organic layers in which lead can be retained.
Chemicals and pollutants all have differing half lives, migration and binding mechanisms and effects on the environment. In 1920 when lead began being added to gasoline, the health and environmental hazards were unknown and although 50 years is a relatively short time, the effects are lasting well beyond its usage period. What are we using today that may affect the planet in the future? This can be a controversial topic to address and all we can do is our best with the information at hand. Be and stay informed, do your research, get involved and consult the experts. Your arborist will recommend the best treatment and management methods for your landscape’s needs with your health and the environment in mind, if you have any concerns or questions do not hesitate to ask!