Approche spatiale des inégalités d'exposition environnementale et socioéconomiques Quelle influence sur les inégalités de cancer ? Projet Cancer inégalités régionales, cantonales et environnement (CIRCE)

National audienceINTRODUCTION. La progression de l'incidence du cancer en France et dans les pays développés suscite une interrogation sur l'origine de cette croissance et notamment sur l'importance de la composante environnementale de cette croissance. Les études de corrélations écologiques utilisant les Systèmes d'information géographique (SIG) peuvent apporter un éclairage nouveau sur la relation entre cancer et facteurs environnementaux et socio-économiques. Les objectifs sont de 1) Proposer une méthodologie utilisant des indicateurs permettant de mettre en évidence les inégalités spatiales d'exposition environnementale, de niveau socio-économique et de mortalité par cancer et 2) Comprendre les relations entre cancer et facteurs environnementaux et socioéconomiques en croisant ces données par une étude de corrélation écologique à l'échelle cantonale. MATERIEL/METHODES. A partir des bases de données descriptives de l'environnement, des indicateurs de l'exposition environnementale sont proposés : un indicateur de pollution de l'air à partir du registre européen d'émission des polluants (European pollutant emission register, EPER) pour une cinquantaine de polluants, un indicateur général de contamination des sols à partir de BASIAS, un indicateur de pollution agricole ou urbaine à partir de Corine Land Cover. A partir du recensement INSEE descriptif de la population, l'indice de défaveur sociale de Townsend peut être construit. A partir des données du Centre d'épidémiologie sur les causes médicales de décès (CépiDc) de l'Inserm, le risque relatif de mortalité par cancer a pu être défini. RESULTATS. La région Nord-Pas-de-Calais a été choisie pour illustrer les résultats. Chacun des indicateurs est cartographié à l'échelle des cantons mettant en évidence des disparités géographiques plus ou moins importantes. La carte de l'indice de Townsend fait ressortir la région Lilloise ainsi que le bassin minier comme les zones les plus défavorisées socialement. La cartographie des indices généraux d'exposition environnementale semble faire ressortir ces mêmes zones. Les indicateurs d'exposition à partir d'EPER mettent en évidence de fortes disparités spatiales de l'exposition, et des différences importantes suivant le polluant considéré. Concernant le cancer, les résultats sont variables selon la localisation cancéreuse analysée ; dans le Nord-Pas-de-Calais, les situations récurrentes de surmortalité sont localisées autour des grands pôles. Certains cantons semblent cumuler les inégalités sociales, environnementales et sanitaires. Le croisement de ces données spatialisées par canton permettra de définir les liens éventuels entre cancer, environnement et niveau socio-économique. DISCUSSION ET CONCLUSION. Bien que cette approche comporte quelques limites comme la non prise en compte de la mobilité à court et long terme des populations ou encore les temps de latence relativement long pour le cancer, l'utilisation des SIG dans le cadre d'études de corrélations écologiques apporte une vision nouvelle des disparités spatiales et permettent de mieux comprendre la complexité du lien environnement, social et sant

Transfer process of water and solute in the unsaturated zone of chalk.

International audienc

How spatial variations of chalk groundwater geochemistry are related to superficial formations and infiltration processes of unsaturated zone (quarry of Saint Martin le Noeud, France)

Chalk is complex because of its dual porosity and because of superficial layers more or less thick and more or less permeable. Furthermore there is few knowledge in understanding of groundwater infiltration and dissolution processes in the chalk unsaturated zone (UZ). The role of superficial formations has to be studied especially. The experimental site is an ancient underground quarry of chalk which extends over 1200 m long and 150 m wide (30 m depth) in Saint Martin le Noeud, south of Beauvais, France. This quarry is particularly interesting to study infiltration and dissolution processes indeed this site allows to access to the interface between the unsaturated zone and the saturated zone. Water percolates from the top of the quarry more or less depending on the season. Water table outcrops in the cave and makes about 20 underground lakes. Above the quarry chalk is covered clay-with-flints (CWF) and loess, in surface there are cultivated crops fields. On the first year of the study, physicochemical parameters: temperature, depth, pH, conductivity were recorded in seven lakes with high frequency (every hour). During the same period we sampled the 20 lakes water every month to measure major ions. During this sampling period, percolation was not sufficient to collect percolated water. Results of underground GPS, electric resistivity tomography and observations of three borehole showed that thickness unsaturated zone and that the thicknesses of the superficial formations vary a lot spatially. Three interesting points (separated by less than 1 km) are presented: the above the Pedro lake (25 m of UZ, a few cm of CWF), above the Stalactites lake (30 m of UZ, more than 2.40 m of CWF); above the Blue lake (35 m depth, 60 cm of CWF). First results of chemistry showed that the temporal variation is very low during the first year but there spatial variation is very important at quarry scale. The geochemistry of the lakes are very different: HCO3- varies from 100 to 250mg/l, NO3- from 25 to 100mg/l and Mg from 1.5 to 4 mg/l. . The results of the three previous lakes are: Pedro lake (100 mg/l of HCO3-, 100 mg/l of NO3-, 1.5 mg of Mg2+); Stalactites lake (200 mg/l of HCO3-, 25 mg/l of NO3-, 4 mg/l of Mg2); Blue lake (250 mg/l of HCO3-; 25 mg/l of NO3-, 1.5 mg/l of Mg2+). We may distinguish three different origins for the chalk groundwater quality: an autochtonous origin with ions as HCO3-, an allochtonous origin with agricultural ions as NO3- and another allochthonous origin with CWF markers as Mg2+

How spatial variations of chalk groundwater geochemistry are related to superficial formations and infiltration processes of unsaturated zone (quarry of Saint Martin le Noeud, France)

Chalk is complex because of its dual porosity and because of superficial layers more or less thick and more or less permeable. Furthermore there is few knowledge in understanding of groundwater infiltration and dissolution processes in the chalk unsaturated zone (UZ). The role of superficial formations has to be studied especially. The experimental site is an ancient underground quarry of chalk which extends over 1200 m long and 150 m wide (30 m depth) in Saint Martin le Noeud, south of Beauvais, France. This quarry is particularly interesting to study infiltration and dissolution processes indeed this site allows to access to the interface between the unsaturated zone and the saturated zone. Water percolates from the top of the quarry more or less depending on the season. Water table outcrops in the cave and makes about 20 underground lakes. Above the quarry chalk is covered clay-with-flints (CWF) and loess, in surface there are cultivated crops fields. On the first year of the study, physicochemical parameters: temperature, depth, pH, conductivity were recorded in seven lakes with high frequency (every hour). During the same period we sampled the 20 lakes water every month to measure major ions. During this sampling period, percolation was not sufficient to collect percolated water. Results of underground GPS, electric resistivity tomography and observations of three borehole showed that thickness unsaturated zone and that the thicknesses of the superficial formations vary a lot spatially. Three interesting points (separated by less than 1 km) are presented: the above the Pedro lake (25 m of UZ, a few cm of CWF), above the Stalactites lake (30 m of UZ, more than 2.40 m of CWF); above the Blue lake (35 m depth, 60 cm of CWF). First results of chemistry showed that the temporal variation is very low during the first year but there spatial variation is very important at quarry scale. The geochemistry of the lakes are very different: HCO3- varies from 100 to 250mg/l, NO3- from 25 to 100mg/l and Mg from 1.5 to 4 mg/l. . The results of the three previous lakes are: Pedro lake (100 mg/l of HCO3-, 100 mg/l of NO3-, 1.5 mg of Mg2+); Stalactites lake (200 mg/l of HCO3-, 25 mg/l of NO3-, 4 mg/l of Mg2); Blue lake (250 mg/l of HCO3-; 25 mg/l of NO3-, 1.5 mg/l of Mg2+). We may distinguish three different origins for the chalk groundwater quality: an autochtonous origin with ions as HCO3-, an allochtonous origin with agricultural ions as NO3- and another allochthonous origin with CWF markers as Mg2+

Climate Variability and Groundwater Response: A Case Study in Burkina Faso (West Africa)

West Africa experiences great climate variability, as shown by the long-lasting drought since the 1970s. The impacts of the drought on surface water resources are well documented but remain less studied regarding groundwater resources. The nexus between climate variability and groundwater level fluctuations is poorly documented in this area. The present study focuses on the large reserve of groundwater held by the Kou catchment, a tributary of Mouhoun river (formerly the Black Volta) in the southwest of Burkina Faso, in the Sudanian region. Analyses were undertaken using climatic time series (1961–2014), two rivers’ hydrometric data (1961–2014), and 21 piezometers’ time series (1995–2014) applying statistical trend (Mann–Kendall) and break (Pettitt) tests, correlation analysis, and principal component analysis. The analyses showed that rainfall in the area underwent a significant break in 1970 with an 11%–16% deficit between the period before the break and the period after the break that resulted in a deficit three times greater for both surface and base flows. This significant deficit in flow results from the combined effect of a decrease in rainfall and an increase in evapotranspiration. The response of the catchment to the slight increase in rainfall after 1990 was highly dependent on hydrological processes. At Samendéni, on the Mouhoun River, the flow increased with a slight delay as compared to rainfall, because of the slow response of the base flow. Whereas at Nasso on the Kou river, the flow steadily decreased. The analysis showed that the groundwater level responds to rainfall with a delay. Its response time to seasonal fluctuations ranges from 1 to 4 months and its response time to interannual variations exceeds the timescale of one year. This response is highly dependent on the local aquifer’s physical characteristics, which could explain the spatial heterogeneity of the groundwater response

La carrière souterraine de Saint-Martin-le-Nœud : observatoire des transferts dans la Zone Non Saturée de la Craie.

National audienc

Transferts de l'atrazine et la déséthylatrazine dans la zone non saturée en milieu crayeux.

National audienc

Geophysical characterization of the vadose zone above an abandoned underground quarry of Chalk

An abandoned underground quarry of Chalk located near Beauvais (France) is of particular interest to study infiltration and dissolution processes in the vadose zone. The presence of permanent underground lakes created by the outcroping water table allows to describe the spatial and temporal variability of groundwater geochemistry within the quarry. Geophysical measurements were carried out at the surface above the quarry to characterize the geometry and the physical properties of the vadose zone and study their influence on the groundwater quality variations. Electromagnetic induction (EMI) mapping performed at the surface provided a spatial description of the thicknesses of soil and clay-with-flints superficial formation covering the Chalk. Electrical resistivity tomography (ERT) emphasized deeper geological structures along a transect located directly above an underground lake. Finally, the combined use of pressure-wave traveltime tomography and surface-wave profiling along the same transect highlighted strong lateral variations of the Poisson's ratio corresponding to significant water content variations within the clay-with-flints and the Chalk formations