U.S. Geological Survey - Environmental Health

Bio-Uptake Research Laboratory — Menlo Park, California

About the Laboratory

The Bio-Uptake Research Laboratory uses novel stable isotope tracing techniques to assess the bioavailability of inorganic contaminants and characterize the underlying processes governing their bioavailability.

The Freshwater Snail - Lymnaea stagnalis
Picture of the freshwater snail (Lymnaea stagnalis) used in the laboratory exposure tests to understand metal uptake and bioavailability. Photo Credit: Javier Garcia-Alonso, USGS.
Mayfly - Cinygmula
The mayfly (Cinygmula) is one of the insects scientists use to study the bioaccumulation of dissolved and dietary metals. Photo Credit: Marie-Noële Croteau, USGS.

Example

Zn bioavailability graph
Graph showing the difference in the bioavailability of zinc (Zn) from particles collected in two mine drainage impacted rivers—the Snake River and the Animas River. Data from Croteau and others, 2017.

The assessment of zinc bioavailability from different particles suggests that Zn from zinc oxide nanoparticles (often the main ingredient in sunscreens) is extremely high because Zn readily dissolves from the particles and is taken up from the dissolved phase. In contrast, the bioavailability of Zn from particles naturally formed in acid mine drainage wastes is low because Zn sorption to the natural particles is strong.

Diatom mat experiment set up
Diatom mat used during a feeding experiment to study the dietary uptake of uranium by mayflies. Photo Credit: Marie-Noële Croteau, USGS.

Why Does "Bioavailability" Matter?

Contaminant bioavailability matters because bioavailability is a key driver of bioaccumulation, which often precedes the onset of biological effects. An understanding of the biogeochemical processes governing bioavailability can help differentiating perceived versus actual environmental health effects.

Key Laboratory and Analytical Capabilities

  • Inductively coupled plasma-mass spectroscopy
  • Controlled temperature rooms
  • Incubators
  • Ultra-centrifuge
  • Dynamic light scattering
  • Uv-vis spectrophotometer
  • Freeze dryer
  • Micro balance

How to Assess Metal Bioavailability?

In controlled laboratory experiments, model species such as snails or insect larvae are exposed to metal(s) either via the aqueous or the dietary phase, or both. Enriched stable metal isotopes are used to trace the uptake and elimination of the metal(s) in each exposed individual.

Collaboration is Key

This laboratory thrives on collaborations notably wit:

  • Chemists and geologists because geochemical processes control the attributes and forms of contaminants;
  • Biologists because species-specific physiological processes govern the uptake, loss, internal sequestration and cellular fate of metals;
  • Microbiologists because metal uptake occurs primarily in the gut where trillions of microorganisms reside fulfilling essential physiological functions; and
  • Ecologists because of the importance of food web and contaminants transfer across ecosystems.

Contaminants Studied

We study dissolved metals such as copper (Cu), silver (Ag), uranium (U), and zinc (Zn); and synthesized and natural forms of particulate metals as well as engineered nanomaterials.

Confluence of Cement Creek and the Animas River, Colorado
Although the visual picture of mixing zones at stream confluences appears straightforward, such as this one at the confluence of Cement Creek and the Animas River in Colorado, the chemical reactions that occur make them extremely complex from a water-quality perspective. Photo Credit: Marie-Noƫle Croteau, USGS.
Canning Electron Microscopy (Sem) Image of Diatoms with Zinc Oxide (Zno) Nanoparticles
Scanning electron microscopy (SEM) image of diatoms with zinc oxide (ZnO) nanoparticles. U.S. Geological Survey (USGS) scientists are studying the linkages between contaminant bioavailability and toxicity, especially in aquatic organisms exposed to metals and metallo-nanomaterials through solution and diet. Photo Credit: Agnieszka Dybowska, USGS.

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Page Last Modified: 17-Apr-2018 @ 12:13:30 PM EDT