Chemical, microbiological, and spatial characteristics and impacts of contaminants from urban catchments: CABRRES project
These structures (basins) are ecosystems with an important biological diversity. They can represent a high risk of contamination of the connected surfaces, streams, or groundwater environments into which they are discharged. Investigations regarding their efficiency at retaining and transforming pollutants and killing undesirable microbes are thus required. When landscaped, these structures may lead to the development of urban public spaces. In this context, they are subjected to social practices generally associated with public gardens, practices which accidentally or regularly expose the public to their contaminants. In addition, these structures require maintenance and specific management, exposing workers to their contaminants. It is therefore essential that the chemical and microbiological contaminants present in these systems are accurately characterized and measured (i.e. which chemical forms and microbial species and genotypes, and how much?), and their health hazards and risks be inferred or estimated. In this context, several biofilters, detention basins, and stabilization ponds have been monitored and investigated around the world.
The first analyses conducted in the frame of the CABRRES project regarding the microbiological characterization of the sediments of the detention basin are presented in this special issue (see Sebastian et al. paper). These data highlighted a relationship between PAH distribution and microbiological indicators, i.e. Escherichia coli, intestinal Enterococci, and Nocardia, used to predict contamination by pathogenic microorganisms. The detention basin was considered to be contaminated by fecal contaminants, but their origin remains to be investigated. Metagenomic surveys of the bacterial diversity of the sediments have been done, and statistical tests are now being performed to define the dominating taxonomic groups and the incidence of the hydrodynamics and physicochemical forces on their repartition and survival.
The results deriving from CABRRES project will (a) increase knowledge on the interactions between chemical, physical, and microbiological components of detention basins; (b) improve the understanding of the socio-technical processes generating and disseminating contaminants among urban waters; (c) define key indicators for assessing the sanitary status and ecological hazards of these systems; and (d) propose protocols for monitoring these structures. CABRRES is also financially supported by “IMU” Labex (“Intelligence des Mondes Urbains” national excellence laboratory) and OTHU.
Other papers selected for this special issue are on topics related to the CABRRES project. These papers present original observations regarding dissolved or particulate urban contaminants (chemical or microbiological ones) and their dissemination through the water cycle across urban areas. They describe (a) chemical contaminants among the total atmospheric fallout (Gasperi et al.); (b) the sources of contaminants, their accumulation on and their mobilization from, urban surfaces (Shorshani et al.; Kaaniche et al.); (c) the transport and the variability of contaminants in sewer system (Hannouche et al.; Lucas et al.); as well as (d) their key characteristics (El-Mufleh et al.), their trapping, and their transformation in sewer or stormwater-specific structures such as biofilters (Chandrasena et al.; Mailler et al.), lagoons (Lavenir et al.), settling basins (Yan et al.; Sebastian et al.; Gonzalez-Merchan et al.), and infiltration basins (Gonzalez-Merchan et al.).
Authors and reviewers are greatly acknowledged for their contributions. Several contributions come from the French observatories for urban water monitoring and management (ONEVU-Nantes, OPUR-Paris, and OTHU - Lyon), which are gathered into the same inter-observatory structure called SOERE URBIS (http://www.graie.org/urbis-soere/spip/?lang=en) and give an overview of the French initiatives in this field. Dr. Philippe Garrigues, Editor-in-Chief of Environmental Science and Pollution Research, and his Editorial team are warmly thanked for their interest on this topic and handling of the review process.