Reference no: EM133662791
Assignment:
Environmental Science and Sustainability - With Access; 2nd Edition - Publisher: Norton
Background
Lead is a metal that is commonly found in urban soils in elevated concentrations. This is problematic because lead is a neurotoxin, and it is especially dangerous to small children who have growing bodies and growing brains, because of children's "hand to mouth" behavior. Lead from human activities is often associated with the smallest particle sizes and concentrations are often high in dust. Lead was a popular paint additive until the 1970s because the addition of lead made the paint more durable, although leaded paint use was most popular during the 1940s. Lead was also a fuel additive (anti-knock agent) that was phased out in the U.S. in the 1980s. Lead can also be emitted into the atmosphere during industrial processes, particularly smelter activities, and during the combustion of coal.
Lead is not mobile in the soil (it stays near the surface), except when soil has no vegetative cover and the ground dries out. When this happens, the lead may be mobilized as dust. In most natural settings that have not received any anthropogenic lead, lead concentrations in soils do not exceed 50 ppm. The EPA considers it safe to garden when lead concentrations are only 200-300 ppm. The EPA also recommends that lead concentrations are unsafe when there is no vegetative cover in a children's play area and concentrations are >400 ppm. Finally, the EPA recommends that values >1200 ppm should be considered unsafe regardless of the presence of vegetation or the use of the area.
Some important trends in soil lead concentrations to consider:
In undisturbed soils impacted by anthropogenic activities, lead concentrations are highest at the surface and decrease rapidly.
Soils impacted predominantly by roadway sources have high lead concentrations close to the road and exponentially decrease to background levels by ~50 m.
Theoretically, homes with lead-based paint should have higher lead concentrations near the house.
- Do some additional research. What are the sources of lead to urban areas?
- How is this different from more rural areas?
- What are the approaches to remediating lead in soils in residential areas?
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