Vegetation in urban areas: water and carbon cycles, impact on air quality and micro-scale refreshment. The case of Dijon metropolis

Started in november 2022

Funding: French National Research Institute for Sustainable Development (IRD), Paris

Supervisors: Nadège Martiny (Dijon) & Christian Hartmann (Paris)

Abstract

In the context of climate variability and change, tomorrow’s city needs to answer to issues of durability, resilience and citizen comfort. Vegetation is a key element for the environment quality in urban areas, as acknowledged by scientists’ community and population (Van Eeckout L., 2016; Conservancy, 2016). The plant foliage provides a natural barrier, a protective mask, but also a trap where particles settle (Y. Brunet, 2017), which directly improves air quality. It has also been shown some vegetation species as well as foliage nature are parameters which can contribute to the efficiency of the particles capture (Nowak, D.J., 2019). Shading effects and evapotranspiration are the main factors for refreshment in a city. However, the evaporation process is only observed when the plant is able to mobilize sufficient water volumes. In the city the water supply of the vegetation root zone is strongly influenced by the rate of soil sealing. Consequently, the level of impermeability of an urban surface trigger the water supply of the plants, thus the importance of their involvement in the water and carbon cycles as well as the degree of service they provide. The PhD work will enable a better understanding of the vegetation role on the green water cycle and carbon cycles on the one hand, and on air quality and urban climate on the other hand. The objective is to gain a better knowledge of water and carbon flows mobilized by the vegetation in relation to soil sealing, at a micro-scale, and in diversified urban environments. To achieve this, a reliable quantification of these flows will be essential, particularly through a multi-site field approach. The study sites, located in Dijon metropolis, will be very contrasted in terms of vegetative activity, and will be selected to represent a variability of situations (connection to the stormwater network, exposure of the vegetated area to the sun and wind, type of soil, nature of the plants, site frequentation). The Pleiades satellite imagery can be used for the selection of these sites, in particular thanks to the multispectral bands of the sensors which will provide a reliable quantification of the photosynthetic activity of the vegetation. Soil, Vegetation and Atmosphere micro-stations will be installed on these sites. At the soil level, temperature and humidity measurements will be carried out. At the vegetation level, evaporation activity and leaf area index will be measured by micro-dendrometry and LIDAR technology respectively. Finally in the atmosphere, the concentration of fines particles (PM10, PM2.5 and PM1) will be measured by air quality micro-sensors, previously calibrated and validated. This field approach would make it possible to collect data in order to better understand water and carbon cycles in urban areas, while allowing for the development of relevant and affordable vegetation functionality indices that can be communicated in order to discriminate, in terms of environmental quality, different configurations of vegetated spaces.

Keywords

vegetation – air quality – urban refreshment – water resource – carbon flow – urban area – micro-scale measurements

extrait:

lien_externe:

titre:

Végétation en zone urbaine : rôle sur les cycles de l’eau et du carbone, impact sur la qualité de l’air et le rafraîchissement à micro-échelles. Le cas de Dijon Métropole

date_de_debut_these:

novembre 2022

nom:

Canovas

date_de_debut_these_numerique:

202211

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kc_raw_content:

Vegetation in urban areas: water and carbon cycles, impact on air quality and micro-scale refreshment. The case of Dijon metropolis

Started in november 2022

Funding: French National Research Institute for Sustainable Development (IRD), Paris

Supervisors: Nadège Martiny (Dijon) & Christian Hartmann (Paris)

 

Abstract

In the context of climate variability and change, tomorrow’s city needs to answer to issues of durability, resilience and citizen comfort. Vegetation is a key element for the environment quality in urban areas, as acknowledged by scientists’ community and population (Van Eeckout L., 2016; Conservancy, 2016). The plant foliage provides a natural barrier, a protective mask, but also a trap where particles settle (Y. Brunet, 2017), which directly improves air quality. It has also been shown some vegetation species as well as foliage nature are parameters which can contribute to the efficiency of the particles capture (Nowak, D.J., 2019). Shading effects and evapotranspiration are the main factors for refreshment in a city. However, the evaporation process is only observed when the plant is able to mobilize sufficient water volumes. In the city the water supply of the vegetation root zone is strongly influenced by the rate of soil sealing. Consequently, the level of impermeability of an urban surface trigger the water supply of the plants, thus the importance of their involvement in the water and carbon cycles as well as the degree of service they provide. The PhD work will enable a better understanding of the vegetation role on the green water cycle and carbon cycles on the one hand, and on air quality and urban climate on the other hand. The objective is to gain a better knowledge of water and carbon flows mobilized by the vegetation in relation to soil sealing, at a micro-scale, and in diversified urban environments. To achieve this, a reliable quantification of these flows will be essential, particularly through a multi-site field approach. The study sites, located in Dijon metropolis, will be very contrasted in terms of vegetative activity, and will be selected to represent a variability of situations (connection to the stormwater network, exposure of the vegetated area to the sun and wind, type of soil, nature of the plants, site frequentation). The Pleiades satellite imagery can be used for the selection of these sites, in particular thanks to the multispectral bands of the sensors which will provide a reliable quantification of the photosynthetic activity of the vegetation. Soil, Vegetation and Atmosphere micro-stations will be installed on these sites. At the soil level, temperature and humidity measurements will be carried out. At the vegetation level, evaporation activity and leaf area index will be measured by micro-dendrometry and LIDAR technology respectively. Finally in the atmosphere, the concentration of fines particles (PM10, PM2.5 and PM1) will be measured by air quality micro-sensors, previously calibrated and validated. This field approach would make it possible to collect data in order to better understand water and carbon cycles in urban areas, while allowing for the development of relevant and affordable vegetation functionality indices that can be communicated in order to discriminate, in terms of environmental quality, different configurations of vegetated spaces.

 

Keywords

vegetation – air quality – urban refreshment – water resource – carbon flow – urban area – micro-scale measurements