Iron oxide coatings on sand grains from the Atlantic coastal plain: High-resolution transmission electron microscopy characterization

Nanoscale characterization of so-called iron oxide coatings on aquifer sand s is vital for understanding the fate and transport of naturally occurring and anthropogenic chemical species. These coatings, which typically have a strong reddish color, are commonly assumed to consist primarily of iron oxi des and oxyhydroxides. This work shows that the yellowish red to strong bro wn coatings on sediments from an Atlantic coastal plain aquifer in Virginia are predominantly a mixture of Si- and Al-rich nanophases of variable crys tallinity with interspersed smectite and agglomerates of goethite nanoparti cles. Clusters of bacterial cells, diatom fossils, sponge spicules, and oth er trace minerals are also observed.