Yale University, Ph.D.
Francois Fiessinger Scholar 2003
Irreversibility of Organic Compound Sorption to Natural Organic Matter
Where Are They Now? Michael currently holds the position of a research group leader in Environmental Organic Chemistry at the Swiss Federal Institute of Technology (ETH) in Zurich.
Project Description (while EREF Scholar):
Michael’s Ph.D. research aimed at identifying the mechanistic causes of sorption irreversibility of organic pollutants in natural organic matter (NOM) solids. NOM is considered the most important sorbent for organic pollutants in the environment. Sorption irreversibility results in higher affinities of the pollutants to NOM during desorption (when the concentrations of the pollutants is lowered in solution) as compared to the previous sorption step (when the solution concentration was increased). Applied to pollution abatement, irreversibility leads to a lower degree of desorption that predicted by models that assume reversibility and to the generation of a fraction of the pollutants that strongly resists desorption. Irreversibility is, on the one hand, advantageous as it may lead to lower bioavailability and hence lower acute toxicity to organisms as compared to reversible sorption. On the other hand, the disadvantages of irreversibility are contaminant plumes that require longer times to be flushed out, and contaminated soils and sediments more strongly resist biological, physical, or chemical treatment. In a series of different experiments, he established that irreversibility was the result of irreversible alterations in the conformation of NOM. These alterations, which were induced by the pollutant during the sorption step, increased the number and the affinities of sorption sites in NOM. An immediate benefit of his dissertation research is an enhanced understanding of the mechanistic causes of sorption irreversibility. As such, his work lays the foundation on which irreversibility can be incorporated into existing models that assess the fate and risks of organic pollutants in the environment. Also, the work has practical implications for establishing environmental risk and cleanup standards. His Ph.D. research promises to help establishing a link between sorption irreversibility and bioavailability of organic pollutants and may thus open up new approaches to the remediation of contaminated sites and to pollution abatement in general.
Michael grew up near the City of Hanover in Germany. Throughout his youth and especially during his high school years, he had become increasingly interested in the environmental sciences. This interest was awakened by environmental tragedies such as acid rain destroying the Black Forest, and the nuclear disaster at Chernobyl. He decided to study Geoecology (Environmental Sciences) at the University of Bayreuth, Germany. He was particularly interested in and fascinated by the complex processes that determine the fate of organic pollutants and organic macromolecules in soils and sediments. After receiving his master degree in 2000, he started his doctoral studies at Yale. In 2005, he moved back to the ‘old world’, where he currently holds the position of a research group leader in Environmental Organic Chemistry at the Swiss Federal Institute of Technology (ETH) in Zurich. Michael’s current research focuses on the fate of viruses, insecticidal proteins expressed by genetically modified crops, and complex ionic organic micropollutants in soils as well as the characterization of the redox properties of organic matter and minerals in soils and sediments.
Sander M., and J.J. Pignatello. 2005. An isotope exchange technique to assess mechanisms of sorption hysteresis applied to naphthalene in kerogenous organic matter. Environmental Science & Technology, 39, 7476-7484.
Sander M., and J.J. Pignatello. 2005. Characterization of charcoal sorption sites for aromatic compounds: Insights drawn from single-solute and bi-solute competitive experiments. Environmental Science & Technology, 39, 1606-1615.
Sander M., Y. Lu, and J.J. Pignatello. 2005. A thermodynamically based method to quantify true sorption hysteresis. Journal of Environmental Quality, 34, 1063-1072
Sander M., Y. Lu, and J.J. Pignatello. 2006. Conditioning-annealing studies of natural organic matter solids linking irreversible sorption to irreversible structural expansion. Environmental Science & Technology, 40, 170-178.
Sander M., and J.J. Pignatello. 2007. On the reversibility of sorption to black carbon: distinguishing true hysteresis from artificial hysteresis caused by dilution of a competing adsorbate. Environmental Science & Technology, 41, 843-849.
Sander M., and J.J. Pignatello. 2009. Sorption Irreversibility of 1,4-Dichlorobenzene in two Natural Organic Matter-Rich Geosorbents. Environmental Toxicology and Chemistry, 28, 447-457.
Newer publications resulting from work at current position at ETHZ:
Hartenbach, A.; Hofstetter, T. B.; Aeschbacher, M.; Sander, M.; Kim, D.; Strathmann, T. J.; Arnold, W. A.; Cramer, C. J.; Schwarzenbach, R. P. 2008. Variability of N isotope fractionation during the reduction of nitroaromatic compounds with dissolved reductants. Environmental Science & Technology, 22, 8352-8359.
Stein K., M. Ramil, G. Fink, M. Sander, T.A. Ternes. 2008. Analysis and Sorption of Psychoactive Drugs onto Sediment. Environmental Science & Technology, 42, 6415-6423.
Richter M., M. Sander, M. Krauss, I. Christl, M.D. Dahinden, M.K. Schneider, and R.P. Schwarzenbach. 2009. Cation Binding of Antimicrobial Sulfathiazole to Leonardite Humic Acid. Environmental Science & Technology, 43, 6632-6638.
Aeschbacher M., M. Sander, and R.P. Schwarzenbach. Novel electrochemical approach to assess the redox properties of humic substances. Environmental Science & Technology. accepted; manuscript es902627