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Modeling lead input and output in soils using lead isotopic geochemistry
R M Semlali1, J B Dessogne, F Monna
1INRA, Unité de Science du Sol, RD10, F-78026 Versailles Cedex, France.
Environmental Science & Technology
|March 30, 2004
Summary
Lead pollution in soil migrates downward very slowly. Less than 0.1% of mobile lead moves out of the top 25 cm annually, meaning pollution persists for centuries.
Area of Science:
- Environmental Science
- Soil Science
- Geochemistry
Background:
- Long-term monitoring of soil pollution is crucial for understanding environmental persistence.
- Anthropogenic lead deposition has historically impacted topsoil quality.
Purpose of the Study:
- To model the downward migration rate of lead from the topsoil (plow layer).
- To assess lead and scandium content and isotopic composition in soil samples.
- To evaluate atmospheric deposition fluxes of lead.
Main Methods:
- Annual soil sampling from experimental plots in Versailles since 1928.
- Analysis of lead and scandium concentrations and lead isotopic compositions.
- Modeling of lead migration using a first-order differential function.
Main Results:
- Lead migration from the plow layer is negligible on a human timescale (<0.1% annually).
- Estimated time to halve accumulated lead pollution is over 700 years under zero input.
- Results align with existing sparse data on lead post-depositional migration.
Conclusions:
- Post-depositional migration of lead in soil is extremely slow.
- Historical pollution levels significantly influence current soil lead concentrations.
- Understanding pollution history is vital for managing persistent soil contaminants.