Wageningen UR BSc and MSc Project Database

Project properties
Title	Exploring the toxicity of the truly dissolved fraction
Group	Soil Chemistry and Chemical Soil Quality
Project type	thesis
Credits	36-39
Supervisor(s)	Frank van Raffe
Examiner(s)	Rob Comans
Contact info	frank.vanraffe@wur.nl
Begin date	2021/03/01
End date
Description	Contaminant leaching from contaminated sites poses significant risks to the human health & environment. A proper understanding of the toxicity and mobility of these contaminants is needed to introduce suitable measures. One way in which this is assessed is through the determination of size distributions of these contaminants. The particle size is known to have a large impact on contaminant transport, with particularly colloidal compounds (size range of 1 ï¿½ 1,000 nm) facilitating transport. Yet studies on size distributions do not directly give information on the chemical species in which the contaminant is present, which is an important attribute for a contaminantsï¿½ toxicity. Potentially, an overlap is present between the smallest size fractions (known as ï¿½truly dissolvedï¿½) and the most chemically reactive species (known as ï¿½free ionicï¿½). While the term ï¿½truly dissolvedï¿½ suggests the presence of only ions, a relatively large fraction of organic matter has been found in this fraction by previous studies. As contaminants can potentially bind to this organic matter, the presence of chemical species other than the ï¿½free ionicï¿½ species is possible. Understanding the prevalence of the ï¿½free ionicï¿½ species in the ï¿½truly dissolvedï¿½ fractions helps interpret the toxicity of this size fraction and also signifies whether there is need of complementary analysis. The aim of this thesis topic is to investigate to what extent the ï¿½free ionicï¿½ and ï¿½truly dissolvedï¿½ contaminant fractions compare in total concentrations. This will be done by comparing a chemical speciation technique, e.g. the donnan membrane technique, with a physical fractionation technique, e.g. ultrafiltration. Several samples will be investigated which vary in potentially relevant environmental parameters, e.g. pH and organic matter. Potentially, geochemical modelling will be performed to fully explore the relevant chemical forms in the ï¿½truly dissolvedï¿½ fraction.
Used skills	- Literature review - Laboratory work: extractions, size fractionation, donnan membrane technique - Geochemical modelling - Data processing
Requirements	See: https://ssc.wur.nl/Handbook/Course/SOC-81336