Air quality biomonitoring: application of environmental magnetism to provide air pollution cartographies in a road requalification context

At the moment, air quality is a major concern for human and environmental health. The challenge is to produce a robust air pollution mapping for different metrological contexts. In optical physics, the development of particulate matters counters is in full expansion, but the calibration is time-consuming and is difficult to achieve. To answer this problem, many alternatives have been developed as environmental magnetism applied to dust deposition on accumulative surfaces (plant leaves, barks, paper filters,…). In this context, our study focuses on the characterization of the influence of road traffic on air quality along the western bypass of the city of Montpellier (south of France). This work was requested by the Vinci ASF company, in charge of the requalification. 

We chose to work with a mixed approach to be able to free ourselves from the influence of environmental variables. We used local vegetation by selecting species with a good spatial distribution and a capacity of capture of particulates matter (PM) recognized in the literature. Our choice was Pinus pinea, Pinus halepensis, and Arundo donax. In order to support the measurements obtained from these plants, we also used passive cellulose filters (Cao et al. method, 2015). The idea was to plot the relative concentrations of the pollutants (Letaïef et al. 2020) measured for each type of sensor on a map, and to compare them to each other. These concentrations were obtained with saturation isothermal magnetization (sIRM, 1000 mT). Finally, to complete this field analysis we plan to use low-cost PM counters (Alphasens model, prototyped by Thierry Poidras). The results show that the highest concentrations are most often associated with partitioned areas and heterogeneous traffic (acceleration and braking). Another interesting result shows that vehicles emit more PM at the exit of a roundabout than at the entrance of it. To characterize the source of the pollutants, we are currently doing a series of complementary analyses. These series include mineralogy analyses on SEM images, hysteresis cycles, and KT curves. Finally, as plant leaf characteristics (macro and micromorphology) influence PM sorption, we also plan to compare the uptake efficiency of our selected species through an experiment within our wind tunnel, the ZephyrLAB (Saint-Aunès, south of France).

References

Cao, Liwan, Erwin Appel, Shouyun Hu, et Mingming Ma. 2015. « An Economic Passive Sampling Method to Detect Particulate Pollutants Using Magnetic Measurements ». Environmental Pollution 205 (octobre): 97‑102. https://doi.org/10.1016/j.envpol.2015.05.019.

Letaïef, Sarah, Pierre Camps, Thierry Poidras, Patrick Nicol, Delphine Bosch, et Romane Pradeau. 2020. « Biomagnetic Monitoring vs. CFD Modeling: A Real Case Study of Near-Source Depositions of Traffic-Related Particulate Matter along a Motorway ». Atmosphere 11 (12): 1285. https://doi.org/10.3390/atmos11121285.