Geoffroy Séré

Lysimeter monitoring as assessment of the potential for revegetation to manage former iron industry settling ponds

To assess the impact of metal-rich brownfields on groundwater quality, the fluxes in a Technosol developed on a former iron industry settling pond were studied. Intact soil monoliths (1 m(2) × 2 m) were extracted and placed in lysimeters. Dynamics of fluxes of metals and solutes under varying vegetation cover were monitored over the course of four years. Soil hydraulic properties were also determined. Results showed that the Technosol has a high retention capacity for water and metals, in relation to its mineral components and resulting chemical and physical properties. As a consequence, metal fluxes were limited. However, soluble compounds, such as SO4(2-), were found at significant concentrations in the leachates. The presence of a dense and deeply-rooted vegetation cover limited water- and solute-fluxes by increasing evapotranspiration and water uptake, thereby reducing the risks of transfer of potentially toxic compounds to local groundwater sources. However, vegetation development may induce changes in soil chemical (e.g. pH, redox potential) and physical properties (e.g. structure), favoring metal mobilization and transport. Revegetation is a valuable management solution for former iron industry settling ponds, provided vegetation does not change soil physico-chemical conditions in the long term. Monitored natural attenuation is required.

Ecosystem services provided by heavy metal-contaminated soils in China

PurposeSoils provide a variety of ecosystem services (ESs) that are crucial to food security, water security, energy security, climate change abatement, and biodiversity, especially in densely populated countries such as China. At present, China is facing great challenges from serious soil heavy metal (HM) contamination which has damaged soil ESs and soil security. In this paper, we evaluate the ESs that contaminated soils can potentially provide before and after remediation, and we explore the connections between these ESs and the achievement of soil security in China.Materials and methodsAfter an introduction to the concepts of ESs and soil security and a review of the current status of soil HM contamination in China, the ESs that can potentially be provided by HM-contaminated soils are discussed. Finally, we discuss the current remediation status of HM-contaminated soils from the standpoint of optimizing the ability of these soils to provide ESs.Results and discussionThe status of the provision of ESs by HM-contaminated soils of croplands, brownfields, and mining wastelands is described in detail. Contaminated cropland soils fail to provide provisioning (e.g., food production), cultural, and regulating services, while the regulating and supporting services of brownfield soils are greatly reduced. The ESs of mining wasteland soils have been severely damaged, resulting in a high potential for contamination of surrounding ecosystems. Recent soil remediation projects have demonstrated that the damaged ESs of HM-contaminated soils can be restored, which would enhance Chinese soil security. However, it has often been the case that only visible ESs (e.g., food production and vegetation cover) are addressed, while other less noticeable but important services (e.g., water quality and biodiversity) are neglected. Therefore, we propose a framework for the evaluation of ESs provided by HM-contaminated soils.ConclusionsThe ESs that could potentially be provided by HM-contaminated soils would help to achieve soil security in China, not only by improving food security, water security, and energy security but also by helping to protect soil biodiversity and abate global climate change. The ESs provided by HM-contaminated soils should be taken into account in soil policy and management systems as well as by the remediation industry.

Consideration of soil in urban planning documents—a French case study

PurposeGiven their increasing importance, soils should be considered as valuable resources by those involved in urban planning. Indeed, soils are expected to be multifunctional in order both to ensure sustainable development of human societies and to resist major environmental issues. Through the study of planning documents, this article describes the way in which political intentions impact the preservation of soil as an urban resource.Materials and methodsA lexical analysis was conducted of more than 100 French planning documents. Each of them relates to a specific topic (e.g., soil cover, transport, biodiversity) and to a particular application scale. Tropes© software was used to count the number of times the word “soil” occurs in each document. A distinction was made between “soil” written as a surface area (land use, square meters) and a resource (ecosystem, cubic meters). A further statistical analysis was performed by crossing the results with demographic data and the main characteristics of the documents.Results and discussionThe results revealed that soil is a subject which is relatively infrequently addressed in French planning documents. Indeed, its index of occurrence reached 0.06% in comparison to “transport” (0.77%). Moreover, “soil” refers both to a surface area (0.035%) and a resource (0.031%). However, this consideration varies from document to another and depends on the given urban area. Finally, the publication date of the document was correlated with the frequency of the use of the word “soil.” These results suggest that the level of consideration of soil, as a complex ecosystem, is moderate and relies mainly on the people who drafted the document.ConclusionsThe frequency of the word “soil” is comparable to those of words as “biodiversity” and “air.” Moreover, “soil” is considered as a living resource in the planning documents. It also appears that the services provided by agricultural and forest soils are well known to policy makers and planning operators (e.g., food and non-food biomass provisioning). In contrast, urban soils are predominantly seen as surface areas to be converted or as a potential threat due to their level of contamination or geotechnical properties.