Task 2 – Design and supply of the eco-friendly high-tech nano-tracers

Responsible:  Nano-H, C. Louis
Participants:  Nano-H & ILM with the support of LEM & IFSTTAR


Development of nanoparticles as high-tech tracers by ILM team and Nano-H according to the following criteria: (i) capability to mimic emerging pollutants (anthropic nanoparticles) and pathogens by ensuring similar transfer properties; (ii) detectable at very low concentrations; (iii) acting as a contrasting agent for non-intrusive techniques (GPR and MRI); (iv) biodegradable and eco-friendly. Complete characterization of the engineered nano-tracers.

Description of work

The first subtask will consist in designing the nano-tracers to be used for INFILTRON-exp. This first step will rely on the characterization of stormwater and runoff water regarding emerging pollutants including nano-pollutants and bacteria. The nano-tracers will be designed to mimic the main families of pollutants and bacteria found in stormwater. Bacterial taxa (n=3) will be selected according to two DNA sequences (see task 3) and characterized for shape, size and surface charge. The nano-tracers will be made of silica particles. These will be synthesized using sol-gel process or seed particle growth [18, 41]. The use of silica nanoparticles, i.e. nanoparticles capable of dissolving entirely over time, reduces risks for the environment. Their size and electric charge will be adjusted to that of anthropic nanoparticles and round-shaped bacteria found in stormwater. Their size will at least be fixed at three different values (50 nm, 500 nm and 5 µm) and their charge will be modified by silanization to exhibit at least positive, negative and neutral values. Each type of particle will incorporate in its silica matrix a specific fluorescent signature by distinguishable fluorescent dyes such as fluorescein, rhodamine, Cy-5.5 and Cy7 to allow detection in soil interstitial water. The nano-tracers will also be designed to behave as contrasting agents on the field (GPR signal) and in the lab (MRI signal). For GPR, the development of this kind of contrasting agent will be one of the novelties of project. The first attempts will rely on the injection of salts and / or of silica nanoparticles with grafting of specific function to increase the contrast of GPR signal. A part of the task will be dedicated to upstream studies for the selection of the best graft for nano-tracers. For the lab, gadolinium will be fixed to nano-tracers to act as contrasting agent for MRI signal. The use of gadolinium such as AguIX nanoparticles as contrasting agent is routine [78]. All engineered nanoparticles will be characterized regarding their Zeta potential and size distribution using NDLS method. From an analytic point of view, the nano-tracers will be injected into the soil both separately and pooled to study the potential inter-species interactions. Magnetic and optical characterizations techniques such as relaxometry, UV-visible spectroscopy, steady-state and time-resolved fluorimetry will be preferentialy performed for the detection and quantification of nanoparticles and their speciation. Additional deconvolution methods will allow distinction between each pollutant in a mixture sample.

Role of participants

ILM will oversee the development of new ecological friendly nanoparticle tracers and analytical methods for water infiltration – nano-tracer injection experiments. Nano-H will be responsible for the development, characterization of nanoparticles, particle stabilization in colloidal solution and their detection in several medium. LEM will interact with Nano-H for bacterial features such as size and electrical charges of a set of selected genotypes relevant to the distribution trends observed in task 3. In a similar way, IFSTTAR will interact for emerging pollutants and anthropic nanoparticles in stormwater.

Risks and contingency plan

This task is crucial since it will provide the nano-tracers for the other tasks and will be active all along the project. The proposed nano-tracers will be tested against experimentations and field and optimized throughout the whole project and through a back and forth procedure between tasks. To avoid failure of the process, some robust and well known tracers and nanoparticles will be considered as spare tracers. Regarding persistence and toxicity, should the engineered particles turn out to be persistent in the models used (columns) – although very unlikely – other types of materials more prone to weathering and dissolution will be used. More specifically, zinc oxide ZnO and iron oxide Fe2O3 would be good alternatives since these materials are naturally occurring colloids and are known to dissolve over time when exposed to common environmental conditions [40, 65].

Deliverables / milestones

  • D2.1 Patent on the use of new eco-friendly nano-tracers as a contrasting agent for GPR.
  • D2.2 Patent on the use of new eco-friendly nano-tracers for mimicking nano-pollutants & bacteria.
  • M2.1 Design of nanoparticles for acting as contrasting agent
  • M2.2 Design of nanoparticles for mimicking bacteria & emerging pollutants
  • M2.3 Characterization of nanoparticles
  • M2.4 Optimization of nano-tracers for lab and field experiments