To what extent does the environmental magnetism technique acts as a way of assessing the uptake of atmospheric particles by plants?
Authors: Letaïef Sarah , Camps Pierre , Poidras Thierry , Nicol Patrick , Bosch Delphine , Bruguier Olivier 
Published: March 2021

&lt;p&gt;Numerous studies have already shown the possibility of tracing the sources, the&lt;br&gt;compositions, and the concentration of atmospheric pollutants deposited on plant&lt;br&gt;leaves. In environmental geochemistry, inter-element and isotope ratios from&lt;br&gt;chemical element assays have been used for these purposes. Alternatively,&lt;br&gt;environmental magnetism represents a quick and inexpensive asset that is&lt;br&gt;increasingly used as a relative indicator for concentrations of air pollutant on bio&lt;br&gt;accumulator surfaces such as plants. However, a fundamental issue is still pending:&lt;br&gt;Do plants in urban areas represent a sink for fine particles that is sufficiently effective&lt;br&gt;to improve air quality? This is a very topical issue because some studies have shown&lt;br&gt;that the foliage can trap fine particles by different dry deposition processes, while&lt;br&gt;other studies based on CFD models indicate that plant hedges in cities can hinder&lt;br&gt;the atmospheric dispersion of pollutants and therefore increase pollution at the level of&lt;br&gt;emission sources such as traffic. To date, no consensus was made because several&lt;br&gt;factors not necessary well known must be taken into account, such as, PM&lt;br&gt;concentration and size, prevailing wind, surface structures, epicuticular wax, to&lt;br&gt;mention just a few examples. A first step toward the understanding of the impact of&lt;br&gt;urban greens on air quality is the precise determination of the deposition velocity (Vd)&lt;br&gt;parameter. This latter is specific for each species and it is most of the time&lt;br&gt;underestimated in modeling-based studies by taking standard values.&lt;br&gt;In that perspective, we built a wind tunnel (6 m long, 86 cm wide and 86 cm high) to&lt;br&gt;perform analogical experiments on different endemic species. All parameters are&lt;br&gt;controlled, i.e, the wind speed, the nature and the injection time of pollutants (Gasoline&lt;br&gt;or Diesel exhausts, brakes or tires dust, etc&amp;#8230;). We can provide the PM concentrations&lt;br&gt;upwind and downwind of natural reconstituted hedges by two dustmeters (LOACs -&lt;br&gt;M&amp;#233;t&amp;#233;oModem). Beforehand, parameters such as the hedge resistance (%) or the leaf&lt;br&gt;area index (LAI) have been estimated for each studied specie to allow comparability&lt;br&gt;between plants removal potential. The interest would ultimately combine PM&lt;br&gt;concentration measured by size bins from the LOACs with magnetic measurements&lt;br&gt;(ARM, IRM100mT, IRM300mT and SIRM) of plant leaves. The idea is to check whether it&lt;br&gt;would be possible to precisely determine in situ the dust removal rate by urban greens&lt;br&gt;with environmental magnetism measurements. Up to now, we have carried out on&lt;br&gt;different endemic species such as Elaeagnus x ebbingei leaves and Mediterranean&lt;br&gt;pine needles, the results of which will be presented.&lt;/p&gt;