Contaminants become “trapped” in soil over time because of various chemical and biological processes (e.g., aging, weathering, sequestration, adsorption, degradation, etc.). Trapped contaminants are not readily available for uptake into soil organisms and do not cause even if it is detectible by chemical methods. Therefore, contaminant concentration can exceed established safety standards but represent minimal risk to soil organisms if the contaminant is trapped.

Growing earthworms in contaminated soil is a common method to evaluate the toxic effects of contaminants in soil; however, this process is time consuming. Alternatively, contaminant concentration in soil can be determined by chemical extraction and analysis. This approach is fast, but harsh chemical extractions often over estimate the risk because contaminants trapped in soil may be extracted as well thereby suggesting danger when there is none. Arguably, it is better safe (i.e., over estimating potential danger) than sorry; however, cleaning up soils that pose no actual danger wastes resources that can be used to remediate real problem areas. We designed the Simulated Earthworm Gut (SEG) to mimic the earthworm’s gastrointestinal fluid composition under the theory that soil contaminants that are extractable by the SEG would be representative of the contaminant exposure that an earthworm would experience.

Wai Ma