The soils in many iconic Australian landscapes, like the outback and deserts, are colored red by an abundant mineral known as goethite. This mineral tends to lock away trace metals over time, according to research from Washington University in St. Louis Photo Credit: Nathan March |
Trace metals are nutrient elements, like zinc, that animals and plants need in small amounts to function properly. Animals generally get trace metals in their diets or through environmental exposures, while plants take their trace minerals up from soil. If we get too little, we may experience a deficiency, but the opposite can also be true: too much of a trace metal can be toxic.
Scientists believe that up to 50% of the trace metals in soils and urban environments may be bound to the surfaces of mineral grains — rendering the trace metals essentially unavailable for consumption or exposure. Researchers at Washington University in St. Louis wondered what holds them in place.
“When minerals bind trace metals, we often assume that they act like a sponge,” said Jeffrey G. Catalano, a professor of earth, environmental and planetary sciences and the director of environmental studies in Arts & Sciences. “But sometimes, they bind trace metals and won’t let them go. That is great when they are contaminants, but bad when they are serving as micronutrients.”
In a study published in the journal Environmental Science & Technology, Catalano and Greg Ledingham, a PhD candidate in his laboratory, discovered that a common mineral called goethite — an iron-rich mineral that is abundant in soils that cover the Earth — tends to incorporate trace metals into its structure over time, binding the metals in such a way that it locks them out of circulation.