silt or fine organic matter in suspension from a soil horizon. The iron and aluminium oxides collect in the 'B' horizon where the iron oxides can accumulate to form a thin layer of hardpan ...

This is because the soil's pH affects the plants' ability to absorb aluminum ions — a key factor in the color shift. As such, ...

Soil organisms, like earthworms, mix the materials together, merging the boundaries between the horizons. These soils are leached, but not heavily, so the aluminium and iron oxides are dispersed ...

Contaminated soil at a shuttered aluminum plant just north of Columbia Falls will be consolidated and capped under a plan ...