A vegetable garden in the middle of the city (illustration). – Richard B. Levine / Newscom / SIPA
- Urban agriculture is developing more and more in cities. With this underlying trend, the question arises in particular of soil pollution, sometimes at former industrial sites.
- The Toulouse association “Partageons les jardins” is organizing a videoconference on Tuesday on this theme with Camille Dumat, researcher specializing in these questions and founder of the Agriville network.
Vegetable gardens are now growing in the middle of the building bars. After having been confined for a long time to the rural world, agriculture is becoming more and more urban. A groundswell that affects all the major cities of France, but not without raising certain questions: what is the quality of the soil in which the tomatoes of the neo-gardeners grow or the impact of ambient pollution on their plantations?
“How to grow organic vegetables in a polluted environment? What pollution are we exposed to by consuming this production? “. So many questions to which Camille Dumat, professor at the National Agronomic School of Toulouse (INP-ENSAT) will provide answers during the online conference organized this Tuesday by
the Toulouse association “Sharing the gardens”.
“There are sites that are more polluted than others in Occitania, we can have agriculture and gardens in the ground in most places, with exceptions such as in Aude, in Salsigne, it is better to avoid”, poses the one that founded the Agriville network, a platform for exchanges on resources, innovations and participatory research in urban agriculture. It makes it possible to pool information from associations of gardeners, as well as communities or officials such as Ademe.
Until twenty years ago, it was unclear whether the factory that was previously installed on a site used chemicals that could pollute the soil. “Today, there are tools, including inventories like Basol and Basiaswhich allow, for example, to know if there was use of heavy metals ”, continues Camille Dumat.
Pollution of cities and fields
It sometimes happens that this pollution is detected, as was the case a few years ago in Castanet, south of Toulouse, where, after analyzes, we realized that there was a concentration of arsenic in the wells of the collective gardens. “We contacted the Regional Health Agency which took samples and the wells were closed. They were able to continue to use the gardens because the soil was not the problem, ”says the professor from Ensat.
For her, before getting started, you have to do a little preliminary investigation of the site’s environment and do some analyzes to detect, for example, the presence of metals. This will then avoid having to clean up, which is very expensive, as was the case in Montreuil a few years ago, when the market gardening and fruit production of the “Murs à Peaches” site turned out to contain cadmium or even zinc, well above the regulatory thresholds.
The fact remains that soil pollution is not the only one to be present in the city. With automobile traffic, the ambient air can also be loaded with heavy metals such as lead. “The city center is no longer necessarily the most polluted, because there are fewer and fewer cars and more phytosanitary products used by communities in green spaces, which is not the case in countryside or near bypass roads where vehicle emissions are found, ”argues Camille Dumat. Before concluding that, rather than treating or seeking to contain pollution in order to cultivate, “everything must be done upstream to avoid the sources of pollution”.