Pollution des fourrages et des sols par les éléments du groupe platine issus de la circulation routière

Abstract

The increase in deposition of platinum group elements (PGEs: Pt, Pd and Rh) from vehicles on grass and soil has raised concerns about the risk for the quality of food and, in turn, for human health. Here we report the PGEs spatial deposition on ryegrass and soil at the agricultural scale near a rural road with 7200 vehicles per day. While classical studies usually involve direct measurements of plants growing in the field, we used an alternative experimental approach to allow an unambiguous assessment of the pollution impact. Ryegrass (Lolium perenne) was first cultivated in pots in a closed greenhouse to isolate the plants from the outdoor atmosphere. Then, ryegrass pots were transferred to the agricultural field. The distribution of PGEs was assessed by placing ryegrass pots 0 m, 10 m, 25 m and 50 m from the road. This method thus allowed the measurement of PGE deposit from vehicle emissions during a known timeframe (one month). Moreover, the soil samples were collected at all locations where the ryegrass pots were placed in this sampling site. The PGE concentrations in ryegrass and in soil samples were analyzed by inductively coupled plasma mass spectrometry (ICP-MS). Our results clearly show the impact of traffic pollution on both ryegrass and soil. The maximum PGE concentrations are obtained close to the road. From 0 to 50 m away from the road, Pd concentrations decrease significantly up to 39% in ryegrass and up to 50% in soil. Pollution map should thus help to assess more precisely the impact of road traffic on food quality.