Thought Leadership

GEI’s Gensemer and Gondek Co-Author Journal Article in Environmental Toxicology & Chemistry Journal

October 13, 2017

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GEI’s Bob Gensemer and John Gondek co-authored a journal article titled “Evaluating the Effects of Ph, Hardness, and Dissolved Organic Carbon on the Toxicity of Aluminum to Freshwater Aquatic Organisms Under Circumneutral Conditions” that was published in the Environmental Toxicology and Chemistry Journal.

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While it is well known that increasing water hardness and dissolved organic carbon (DOC) concentrations mitigate the toxicity of aluminum (Al) to freshwater organisms in acidic water (i.e., pH < 6), these effects are less well characterized in natural waters at circumneutral pHs for which most aquatic life regulatory protection criteria apply (i.e., pH 6 to 8). The evaluation of Al toxicity under varying pH conditions also may be confounded by the presence of Al hydroxides and freshly precipitated Al in newly prepared test solutions. Aging and filtration of test solutions were found to greatly reduce toxicity suggesting that toxicity from transient forms of Al could be minimized and that precipitated Al hydroxides contribute significantly to Al toxicity under circumneutral conditions, rather than dissolved or monomeric forms. Increasing pH, hardness, and DOC were found to have a protective effect against Al toxicity for fish (Pimephales promelas) and invertebrates (Ceriodaphnia dubia, Daphnia magna). For algae (Pseudokirchneriella subcapitata), the protective effects of increased hardness were only apparent at pH 6, less so at pH 7, and at pH 8, increased hardness appeared to increase the sensitivity of algae to Al. The results support the need for water quality-based aquatic life protection criteria for Al, rather than fixed value criteria, as being a more accurate predictor of Al toxicity in natural waters.

About the Authors:

Dr. Robert (Bob) Gensemer has 30 years of academic and industrial experience in aquatic ecology and limnology, ecotoxicology, and ecological risk assessment. His project experience includes general aquatic toxicology, the conduct and oversight of ecological risk assessments for both aquatic and terrestrial habitats, sediment remedial investigations under EPA’s Superfund program, and the regulatory implementation of ambient water quality criteria for protection of aquatic life. Since joining GEI, Bob has established National leadership with respect to the regulatory implementation of new bioavailability-based models for development of aquatic life criteria, such as the Biotic Ligand Model for copper, aluminum, and other metals. He has also helped strengthen GEI’s technical and strategic leadership in the application of ecological risk assessment to the remediation of contaminated sediments, being a key member of utility client project teams at some of the largest and most complex Superfund remediation sites in the U.S.

John Gondek is an environmental toxicologist and natural resources scientist who specializes in the analysis of toxicity and chemistry data in relation to legacy and on-going sources of contamination in complex urban environments. He has supported the ecological risk assessment and technical analysis at multiple Superfund sites and former manufactured gas plants. He has also supported projects related to coastal resiliency, hurricane disaster relief, and coastal and wetlands permitting. Additionally, he is involved in the development and updating of aquatic life criteria for several metals using the Biotic Ligand Model. He has conducted extensive work in the field including natural resources and wildlife surveys, and the collection of sediment, surface water, stormwater, and biological samples in aquatic and urban ecosystems.