# Peter Santschi

Peter H. Santschi is a marine scientist and an academic. He is the director of the Laboratory for Oceanographic and Environmental Research, adjunct senior research scientist at the Lamont-Doherty Geological Observatory as well as a professor of oceanography and marine sciences at Texas A&M University.
Santschi is most known for his works on marine and environmental chemistry, including environmental radiochemistry. His works have been cited in academic journals, including Environmental Science & Technology, Marine Chemistry, Science of the Total Environment, and Journal of Marine Research. He was elected as a Fellow of the American Geophysical Union in 2014, and Fellow of the Geochemical Society and the European Association of Geochemistry in 2017.

## Education

Santschi earned his B.S. in Chemistry from Gymnasium Bern in 1963. He subsequently completed his M.S. in chemistry from the University of Bern in 1971, followed by a Ph.D. in chemistry on chemical processes in Lake Biel from the same institution in 1975.

## Career

Santschi began his academic career in 1968 as a lecturer in chemistry at Humboltianum Gymnasium, serving until 1970. From 1970 to 1975, he was a teaching and research assistant at the University of Bern. He then moved to Columbia University, where he was a research associate at the Lamont-Doherty Geological Observatory from 1977 to 1981, followed by a position as a senior research scientist from 1981 to 1982. From 1982 to 1988, he was a research scientist at the Swiss Federal Institute of Aquatic Science and Technology (EAWAG) and lecturer (privat docent) at ETH, while also an adjunct senior research scientist at the Lamont-Doherty Geological Observatory. Since 1988, he is a professor of oceanography and marine sciences at Texas A&M University. He was appointed a Regents Professor at Texas A&M University in 2009 and a Distinguished Professor at Texas A&M University in 2021.
From 1982 to 1988, Santschi served as the head of the Isotope Geochemistry and Radiology Section at the Swiss Federal Institute of Aquatic Science and Technology (EAWAG). Additionally, he acted as the focal area coordinator for the Center for Shelf and Coastal Oceanography at the Texas Institute of Oceanography from 1992 to 2000.

## Research

Santschi's research interests span Environmental Chemistry, Biogeochemistry, and Radiochemistry, with emphasis on the role of colloidally sized macromolecular organic matter, especially microbially derived Exopolymeric Substances (EPS). In his early research, he investigated the distribution and removal dynamics of U-Th series radionuclides in Narragansett Bay, revealing that particulate matter and seasonal changes significantly influence their removal rates and concentrations. While examining the partitioning of radioactive trace elements between seawater and particulate matter, his 1984 collaborative study found that Group I elements (group A and B type metals, except those in group II) reach a stable equilibrium quickly, while Group II (elements strongly sorbing to Mn and Fe oxide phases) elements show increasing incorporation into particulate matter over 108 days, indicating complex interactions. In 1989, he, together with B. Honeyman, introduced the Brownian pumping model, which explained the sorption of thorium isotopes and metals in aquatic systems through colloidal coagulation with larger particles, successfully reconciling observed sorption characteristics with both field and laboratory data. Furthermore, his 1990 study investigated the complex interactions of physical, chemical, and biological processes at the sediment-water interface. The study found that early diagenetic transformations driven by organic carbon and electron acceptors significantly influence elemental cycling and fluxes, with physical transport mechanisms and three-dimensional interactions playing crucial roles.
Santschi's 1995 paper examined the distribution and fluxes of dissolved organic carbon (DOC) and colloidal organic carbon (COC) in the Gulf of Mexico and the Middle Atlantic Bight, revealing their vertical gradients, conservative mixing behavior, and size-dependent partitioning. In his exploration of cross-flow ultrafiltration in marine systems, his 2000 joint research with L Guo and others found that low molecular weight (LMW) molecules were significantly retained while high molecular weight (HMW) molecules showed minimal permeation, and recommended high concentration factors (>40) for effective isolation of marine colloids despite challenges in low molecular weight (LMW) molecules' retention. Furthermore, his collaborative 1998 and 2004 studies revealed that polymer gel particles, showed recent radiocarbon ages for carbohydrate enriched fractions, were abundant and crucial in marine ecosystems, significantly impacting carbon cycling sedimentation, and microbial habitats, and highlighted the need for further interdisciplinary research to understand their roles and dynamics. Moreover, through his 2008 research, in collaboration with W.C. Chin, he examined the environmental impact of engineered nanoparticles (ENPs), finding that their surface properties, interactions with organic matter, and effects on biological cell walls significantly influence their behavior, bioavailability, uptake, and toxicity in algae, plants, and fungi.
In related research, Santschi and collaborators analyzed the impact of engineered nanoparticles on aquatic ecosystems, highlighting the role of algae-produced exopolymeric substances in mitigating toxicity and emphasizing the need for further research on ENPs' environmental fate and transport. Additionally, in his 2016 collaborative work with A Quigg and others, he reviewed the role of microbially produced EPS in influencing the fate of oil and dispersants in the ocean and identified key knowledge gaps in understanding EPS production under different environmental conditions. More recently, he documented the widespread observation that when algae and bacteria are exposed to pollutants, in particular nanoparticles such as nano- and microplastics, they respond with secreting more hydrophobic and protein-rich EPS. This lead him to propose in 2020 the protein to carbohydrate (P/C) ratio in EPS as a predictor for aggregation propensity of EPS.
Santschi and his collaborators have continued to investigate radioactive elements relevant to environmental radiochemistry and geochronology. He made major contributions on the use of diverse radioisotopes, including Th-234/organic carbon ratios of sinking particles as predictors of new production, i.e., the removal of carbon from the surface ocean, the movement of long-lived Iodine-229 through aquatic systems as an organic species, and to the organic matter association of plutonium. Lately, in 2024, as part of a collaborative study, he investigated uranium distribution in a contaminated wetland at the Savannah River Site. The study found significantly higher uranium concentrations in the rhizosphere, attributed to enhanced binding with reactive iron (III) oxides formed by plant roots.

## Selected articles

* Nyffeler, Urs P; Li, Yuan-Hui; Santschi, Peter H (July 1984). "A kinetic approach to describe trace-element distribution between particles and solution in natural aquatic systems". Geochimica et Cosmochimica Acta. 48 (7): 1513–1522. Bibcode:1984GeCoA..48.1513N. doi:10.1016/0016-7037(84)90407-1.
* Honeyman, Bruce D.; Santschi, Peter H. (August 1988). "Metals in aquatic systems". Environmental Science & Technology. 22 (8): 862–871. Bibcode:1988EnST...22..862H. doi:10.1021/es00173a002. PMID 22195704.
* Santschi, Peter; Höhener, Patrick; Benoit, Gaboury; Buchholtz-ten Brink, Marilyn (January 1990). "Chemical processes at the sediment-water interface". Marine Chemistry. 30: 269–315. Bibcode:1990MarCh..30..269S. doi:10.1016/0304-4203(90)90076-O.
* Verdugo, Pedro; Alldredge, Alice L.; Azam, Farooq; Kirchman, David L.; Passow, Uta; Santschi, Peter H. (December 2004). "The oceanic gel phase: a bridge in the DOM–POM continuum". Marine Chemistry. 92 (1–4): 67–85. Bibcode:2004MarCh..92...67V. doi:10.1016/j.marchem.2004.06.017.
* Navarro, Enrique; Baun, Anders; Behra, Renata; Hartmann, Nanna B.; Filser, Juliane; Miao, Ai-Jun; Quigg, Antonietta; Santschi, Peter H.; Sigg, Laura (July 2008). "Environmental behavior and ecotoxicity of engineered nanoparticles to algae, plants, and fungi". Ecotoxicology. 17 (5): 372–386. Bibcode:2008Ecotx..17..372N. doi:10.1007/s10646-008-0214-0. hdl:20.500.11850/81653. PMID 18461442.