I joined UvA-IBED at October 2016, after completing two 4 year post-doc positions in Leipzig and Utrecht, a PhD in Utrecht, 2 years technician position at VU Amsterdam, and MSc biology at UvA. Current projects involve studies on the uptake of surfactants (detergents) in organisms, using computational chemistry and in vitro assays. Projects are financed by Unilever, ERASM, Environment Canada, and CEFIC.
Since my MSc in Aquatic Ecotoxicology at the University of Amsterdam (2001), I have been active in various research projects on the environmental impact of chemical substances. My focus is to understand the chemical behavior of contaminants in a testing sytem or in the field, in order to better define the biological response to these contaminants. Key processes are bioavailability, bioaccessibility, bioaccumulation, and biotransformation. Much of my work is related to studies on surfactants and ionogenic chemicals, for which these processes are still not adequately understood.
Chemicals distribute between air, water, soil, and biota depending on chemical parameters, system parameters, and biological parameters. Bioavailability describes the chemical concentration that drives equilibration with internal tissue concentrations in organisms. The freely dissolved concentration of a chemical is a good measure of this chemical activity. Thee concentration sorbed to soil or dissolved/particulate matter particles does not increase the bioavailability of the chemical. For most organic contaminants, the freely dissolved concentration is closely related to the toxicity of the contaminants, because only this concentration equilibrates with the internal tissue concentration that initiates a toxic effect. Especially in soils and sediments, but also for water with suspended matter and dissolved particles, it is thus important to understand, measure, and/or predict the bioavailability of a contaminant.
Bioaccumulation, or more specific bioconcentration, is the concentration difference between the tissue of exposed organisms and freely dissolved concentration, for example a fish in a contaminated river. Chemicals with a high bioaccumulation factor may reach relatively high concentrations in sensitive tissue of organisms for a prolongued time, and thus increase the risk to organisms, particularly higher up the foodchain. Bioaccumulation considers many species-specific biological processes, such as gill ventilation rate and the capacity to metabolize contaminants (biotransformation).
Bioaccessibility relates to the ability of a contaminant to be readily released from a solid phase, such as soil organic matter or dissolved organic carbon. This is an important driver for the biodegradation process of contaminants in for example waste water systems, lab assays, and environmental systems.
Often, my research strategy is to improve models on chemical behavior by generating consistent high quality data on systematic sets of chemicals, and step-by-step variation of key parameters. A lot of work was devoted to optimizing passive samplers to measure the bioavailable concentration in toxicity tests, or to separate freely dissolved concentrations from sorbed concentrations in sorption studies.
During my PhD work at the Institute for Risk Assessment sciences at the Utrecht University, in the group of Joop Hermens, I studied the bioavailability of nonionic and anionic surfactants ('detergents') in marine sediments, in relation to toxic effects. My thesis received the Dutch best thesis award on Environmental Sciences for the period 2008-2009. During a 4 year Postdoc at the Helmholtz Research Institute in Leipzig, in the group of Kai-Uwe Goss, I studied the bioavailability (soil-water partitioning behavior) of cationic surfactants and other organic cations among which many drugs and biocides. As a 4 year Postdoc at IRAS I studied the affinity of organic cations for cell membranes, and supervised projects on the developement of passive sampling techniques for cationic drugs (with Hester Peltenburg), on in vitro biotransformation rates of various types of ionic compounds (with Yi Chen), and on biodegradability of cationic surfactants (with Niels Timmer). In 2016, I was selected for a special issue dedicated to "Emerging Investigators" in the journal Environmental Science: Processes & Impacts.
Which molecular features affect the intrinsic hepatic clearance rate of ionizable organic chemicals in fish? Environ. Sci. Technol. (2016, 50, 12722−12731).
Predicting the phospholipophilicity of monoprotic positively charged amines. Environ. Sci.: Proc. Impacts (2017, asap) DOI: 10.1039/C6EM00615A
Phospholipophilicity of CxHyN+ amines: Chromatographic descriptors and molecular simulations for understanding partitioning into membranes. Environ. Sci.: Proc. Impacts (2016, 18,1011-1123).
Dealing with confounding pH-dependent surface charges in immobilized artificial membrane HPLC columns. Anal. Chem. (2016, 88, 960-967)
Acute toxicity of the cationic surfactant C12-benzalkonium in different bioassays: How test design affects bioavailability and effect concentrations. Environ. Toxicol. Chem. (2014, 33 (3), 606−615)
Sediment toxicity of a rapidly biodegrading non-ionic surfactant: Comparing the equilibrium partitioning approach with measurements in pore water. Environ. Sci. Technol. (2008, 42, 4215–4221)
Chronic toxicity of polycyclic aromatic compounds to the springtail Folsomia candida and the enchytraeid Enchytraeus crypticus. Environ. Toxicol. Chem. (2006, 25, 2423-2431)
Development and evaluation of a new sorption model for organic cations in soil: contributions from organic matter and clay minerals. Environ. Sci.Technol. (2013, 47, 14233−14241)
Ion-exchange affinity of organic cations to natural organic matter: influence of amine type and nonionic interactions at two different pHs. Environ. Sci.Technol. (2013, 47, 798−806)
Sorption of organic cations to phyllosilicate clay minerals: CEC-normalization, salt dependency, and the role of electrostatic and hydrophobic effects. Environ. Sci.Technol. (2013, 47, 14224−14232)
Effect of sodium and calcium cations on the ion-exchange affinity of organic cations for soil organic matter. Environ. Sci.Technol. (2012, 46, 5894−5901)
Experimentally determined soil organic matter-water sorption coefficients for different classes of natural toxins and comparison with estimated numbers. Environ. Sci. Technol (2012, 46, 6118−6126)
Removal of charged micropollutants from water by ion-exchange polymers - Effects of competing electrolytes. Water Res. (2012, 46, 5009−5018)
Modeling nonlinear sorption of alcohol ethoxylates to sediment: the influence of molecular structure and sediment properties. Environmental Science & Technology (2009, 43, 5712–5718)
Nonlinear sorption of three alcohol ethoxylates to marine sediment: A combined Langmuir and linear sorption process? Environ. Sci. Technol. (2007, 41, 3192-3198)
Alcohol ethoxylate mixtures in marine sediment: competition for adsorption sites affects the sorption behaviour of individual homologues. Environ. Poll. (2010, 158, 3116-3122)
Influence of organic matter type and medium composition on the sorption affinity of C12-benzalkonium cation. Environ. Pollut. (2013, 179, 153−159)
Predicting sediment sorption coefficients for linear alkylbenzene sulfonate congeners from polyacrylate-water partition coefficients at different salinities. Environ. Sci. Technol. (2010, 44, 941-947)
Analyzing freely dissolved concentrations of cationic surfactant utilizing ion-exchange capability of polyacrylate coated solid-phase microextraction fibers. J. Chromatogr.A (2012, 1252, 15−22)
Analysis of freely dissolved alcohol ethoxylate homologues in various seawater matrixes using solid-phase microextraction, Anal. Chem. (2007, 79, 2885-2891)
Freely dissolved concentrations of anionic surfactants in seawater solutions: Optimization of the non-depletive solid-phase microextraction method and application to linear alkylbenzene sulfonates. J. Chrom. A (2009, 1216, 2996-3002)
Polyparameter linear free energy models for polyacrylate fiber-water partition coefficients to evaluate the efficiency of Solid-Phase Microextraction. Anal. Chem. (2011, 83,1394-1400)
Viewpoint: More of EPA’s SPARC online calculator - the need for high-quality predictions of chemical properties. Environ. Sc. Technol. (2010, 44, 4400-4401).
Direct tissue sampling of diazepam and amitriptyline using mixed-mode SPME fibers: A feasibility study. Forensic Chem. (2016, 1, 51-57)
Sorption of amitriptyline and amphetamine to mixed-mode solid-phase microextraction in different test conditions. J. Chromatogr A (2015, 1390, 28-38).
Sorption of structurally different ionized pharmaceutical and illicit drugs to a mixed-mode coated microsampler. J. Chromatogr A. (2016, 1447, 1-8)
Elucidating the sorption mechanism of "mixed-mode" SPME using the basic drug amphetamine as a model compound. Analytica. Chim. Acta (2013, 782, 21−27)
Evaluation of passive samplers with neutral or ion-exchange polymer coatings to determine freely dissolved concentrations of the basic surfactant lauryl diethanolamine: Measurements of acid dissociation constant and organic carbon-water sorption coefficient. J. Chromatogr.A (2013, 1315, 8−14)
2017-2020. "D-BASS" Developing a Bioaccumulation Assessment Strategy for Surfactants. (CEFIC LRI - ECO37)
2016-2017. Tissue-water partitioning coefficients for surfactants (ERASM)
2016-2017. Derivation and evaluation of partitioning properties for the bioaccumulation assessment of CMP priority ionogenic substances (ECCC)
2012-2016. Sorption affinity and permeation capacity of chemicals to phospholipid membranes: experimental data and new modelling approaches (Unilever)
2012-2016. Environmental fate and bioavailability of organic cationic compounds (Unilever)
2013-2016. Improving the performance and expanding the applicability of a mechanistic bioconcentration model for ionogenic organic compounds in fish (BIONIC) (CEFIC LRI - ECO21)
2008-2012. Towards a better understanding of the bioavailability and partition behaviour of cationics surfactants (APAG Fatty Nitriles)
2004-2008. A closer look at the sorption behavior of non-ionic surfactants in marine sediment (ERASM)