CABE's interests lie in the study of environmental microstructures and microprocesses (nanometer to centimeter range), so as to better understand the macroscopic structures and behaviour of environmental systems, in particular surface waters, sediments and soils. For this purpose, research on dynamic processes related to physical and colloid chemistry, biochemistry and biophysics is performed both in laboratory and in situ. Because most trace compounds are associated with natural colloids, including inorganic solids (e.g. clay particles) and biopolymers (e.g. polysaccharides, humic compounds), specific studies are related to the characterisation of these colloids, their interactions, and the nature of environmental structures that they form. Furthermore new instrumental analytical methods are being developed to monitor the corresponding key environmental parameters. Such projects include in particular the development of bioanalogic (micro)sensors and analytical systems enabling the measurements of parameters directly related to ecotoxicity, as well as microgradients and fluxes in stratified or non homogeneous environmental systems (e.g. sediment-water interface, soil aggregate, biofilms).

The above figure depicts schematically as exemple, the role of colloids and biopolymers in lakes and ocean. For instance, they strongly influence the sedimentation rate of detrimental and vital trace compounds and ultimately have an impact on biological productivity and biodiversity at the macroscopic level. Aquatic micro-organisms may in turn affect coagulatioln/sedimentation processes by releasing biopolymers into the environment. Similar processes occur in water treatment plants. In soils and sediments, aggregation processes coupled to chemical reactivity of colloids and biopolymers, and microbial activity  will affect the transport of nutrients and trace compounds. All these processes are major focii of CABE's activity.

Based on these guidelines, the activity of CABE is divided into two subgroups :

1- Development of analytical (micro)sensors and environmental in situ probes. (Senior researchers : Dr N. Parthasarathy, M-L. Tercier-Waeber)

Mini or microsensors are being developed for the direct measurement of the active species of trace compounds in situ, with no or minimum sample handling. Emphasis is given to :
    i) the development of bioanalogic sensors, based on environmental and biochemical principles similar to those 
       controlling microbial biouptake, and thus enabling the determination of parameters directly related to ecotoxicity.
   ii) 1D or 2D microsensor arrays, enabling to determine microgradients and fluxes linked to environmental 
       microheterogeneity.
  iii) sensor arrays or microanalytical systems enabling the simultaneous determination of a large number of chemical 
       species in real time.
These sensors are useful not only for environmental purposes, but also for biomedical or industrial applications. Special attention is given to sensors based on voltammetry and permeation liquid membranes but others may also be used. Systems that minimise sample perturbation are of particular interest. Probes which are based on these sensors are also being developed for in situ measurements in surface waters, sediments and soils.

2- Numerical modelling of environmental supramolecular structures and processes. (Group leader : Dr S. Stoll)

Numerical modelling is performed, in conjunction with the above mentioned experimental studies in order to understand the factors controlling the aggregation and sedimentation of colloids and biopolymers. Relationships between structure and function are of particular interest. Dynamic modelling is used to understand the association of large biopolymers (formation of ternary and quaternary structures) as well as the evolution of aggregates (e.g. collapse) and their sedimentation rates. In all cases a major goal is to relate molecular and supramolecular processes to macroscopic ones by means of scaling laws.