Dr. Nouri M. Hassan


1. Metal speciation

a. Biogeochemistry of trace metals in the natural environment

b. Trace metal speciation and bioavailability in natural waters

In natural waters, trace metals exist in many different physical and chemical forms (such as free metal ions, metals complexed with naturally occurring ligands such as humic substances or inorganic ions such as NTA, EDTA, and metals bound to solids) which determine their mobility, bioavailability, and toxicity to aquatic organisms. Therefore, the determination of relevant species of trace metals, in addition to their total metal concentrations, will be of utmost importance in improving our understanding of the processes and the biogeochemical pathways that govern their fate and ultimate impact on the environment.



2. Characterization and analysis of airborne particulate matter

Particulate Matter (PM) is an air pollutant consisting of a mixture of solid and liquid particles suspended in the air. Different names are being used for types or fractions of particulate matter, defined either by particle size or by sampling method. The most commonly used names include: TSP (total suspended particulates), PM10, PM2.5, coarse particles, fine particles, ultrafine particles, BS (black smoke) and BC (black carbon). In general, smaller particles (PM10 and smaller) are more important for health effects than larger particles since they penetrate deeper into the lungs.

Micro-Orifice Uniform Deposition Impactors (MOUDI) for precision, high accuracy aerosol sampling and collecting size-fractionated particle samples for gravimetric and/or chemical analysis.

Micro-Orifice Uniform Deposition Impactors (MOUDI).

3. Isotope fractionations

The general idea is indeed that all processes which involve chemical or physical reactions result in a fractionation of isotopes. So natural variations could be observed in environment samples after physical processes like evaporation or after biogeochemical processes such as methylation for example. So isotopic ratios could be used to trace in environmental samples, the source of metal and elucidate his biogeochemical behavior. Isotope fractionation is the physical phenomenon which causes changes in the relative abundance of isotopes due to their differences in mass. There are two categories of isotope effects: equilibrium and kinetic.

An equilibrium isotope effect will cause one isotope to concentrate in one component of a reversible system that is in equilibrium. If it is theta heavier isotope that concentrates in the component of interest, then that component is commonly referred to as enriched or heavy. If it is the light isotope that concentrates then the component is referred to as depleted or light. In most circumstances the heavy isotope concentrates in the component in which the element is bound more strongly and thus equilibrium isotope effects usually reflect relative differences in the bond strengths of the isotopes in the various components of the system.

A kinetic isotope effect occurs when one isotope reacts more rapidly than the other in an irreversible system or a system in which the products are swept away from the reactants before they have an opportunity to come to equilibrium. Normally, the lighter isotope will react more rapidly than the heavy isotope and thus the product will be lighter than the reactant.

4. Analytical chemistry

Development of analytical techniques for chemical speciation of trace metals in the natural environment.

a-  Inductively-Coupled Plasma - Mass Spectrometry (ICP-MS)

b-  Electrochemical techniques (ASV-RDE and AdCSV)