lead ( pb ) in urban soils
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Lead (Pb) in Urban Soils
Laboratory 14: CRSS/FANR 3060Spring 2011
Urban soils often contaminated with metals (Pb)
Refining, smelting (aerial deposition)
Plumbing (Pb solder)
Before 1973 – additive in gasoline
Before 1977 – white pigment in paint -- PbCO3: bright white, anti-fungal
-- ends up in soil with scraping/repainting
Risk pathways for metals leaching to groundwater (NA: city water…)
Max. in groundwater – 0.015 ppm
Risk pathways of metals Plant uptake (maybe– “urban agriculture”…)
Risk pathways for metals Soil ingestion
--all kids eat some dirt; some eat a lot…--accumulates in brain: neurological effects(synapse damage, behavioral, learning
disabilities, etc.)
Georgia Childhood Lead Poisoning Prevention Program (GCLPPP)
10-20 ppm typical
Loading limits soil – 300 ppm
Risk- free – 75 ppm
Nutrients – Cu, Zn, Co
Toxic – (higher concentrations) Cd, Pb, Hg
Lead in paint – Lead Carbonate (PbCO3)
Soluble dilute acid (to make insoluble above 7 pH)
Nine sample: (3 distances x 3 depth)
Extract with acid to dissolve Pb-- 1.0 g soil + 30 mL 0.1 M HNO3 (centr. tube)--shake 5 min; filter--analyze Pb by flame AA
mg/L x 0.03 L/0.001kg = mg/kg
Transect
Distance (ft) 0 5 10
Depth (in)
0-11-33-6
Assessment:> sample around older houses
-- distance from house (source)-- depth (paint deposited during
scraping)
> define area/depth that exceeds regulatorylimits:400 mg/kg: “chronic” level1200 mg/kg: “acute” level
Remediation:
Bioremediation - Indian Mustard (Lead and chromium) What is the risk pathway?
What is the extent of contamination?
What are possible fixes for problem?
What are costs vs. benefits of alternatives?
Remediation strategy One-page paper: Introduction Materials and Methods Discussion ReferenceTo reduce exposure to childrenSpecify depths and distances
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