Potential Impact of Seawater Uranium Extraction on Marine Life

A variety of adsorbent materials have been developed to extract uranium from seawater as an alternative traditional terrestrial mining. A large-scale deployment of these adsorbents would be necessary to recover useful quantities of uranium, and this raises a number of concerns regarding potential impacts on the surrounding marine environment. Two concerns are whether or not the adsorbent materials are toxic and any potentially harmful effects that may result from depleting uranium or vanadium (also highly concentrated by the adsorbents) from the local environment. To test the potential toxicity of the adsorbent with or without bound metals, Microtox assays were used to test both direct contact toxicity and the toxicity of any leachate in the seawater. The Microtox assay was chosen because it detected nonspecific mechanisms of toxicity. Toxicity was not observed with leachates from any of the 68 adsorbent materials that were tested, but direct contact with some adsorbents at very high adsorbent concentrations exhibited toxicity. These concentrations are, however, very unlikely to be seen in the actual marine deployment. Adsorbents that accumulated uranium and trace metals were also tested for toxicity, and no toxic effect was observed. Biofouling on the adsorbents and in columns or flumes containing the adsorbents also indicates that the adsorbents are not toxic and that there may not be an obvious deleterious effect resulting from removing uranium and vanadium from seawater. An extensive literature search was also performed to examine the potential impact of uranium and vanadium extraction from seawater on marine life using the Pacific Northwest National Laboratory's (PNNL's) document analysis tool, IN-SPIRE. Although other potential environmental effects must also be considered, results from both the Microtox assay and the literature search provide preliminary evidence that uranium extraction from seawater could be performed with minimal impact on marine fauna.