SEGH Articles

Trace Metal inputs in French Pyrenees: a spatial and temporal case study in the Upper valley of the Vicdessos

02 May 2013
A human-environment observatory aims to monitor the evolution of human-environment interactions within the Upper Vicdessos valley. The aim is to collect data and integrate them to conduct a transdisciplinary research in a changing environment.

 

The following article comes from the Ecolab – members of the organising team for this year’s International SEGH meeting in Europe. The venue in Toulouse, Southern France promises and exciting and informative series of oral and poster presentations in stunning surroundings in the centre of the city.”

Trace Metals (e.g. Pb, Hg, Cu) are metallic chemical elements in small amounts in natural rocks and soils. However human activities have impacted their biogeochemical cycles through local and global dispersions throughout the world since the beginning of the metallurgy more than 5000 years ago. As some of these trace metals are known to be harmful and can be accumulated in natural environments, it is important to understand the present trace metal inventories in soil.

Our study takes place in the upper valley of Vicdessos (Ariège). This is a mountain catchment situated in the French Pyrenees up to 2600 m above see level. As several places in the whole Pyrenees range, human pressure, variable in time and space, have impacted on the surrounding environment. To be more precise mining and smelting activities (Iron, Ag-Pb Galena), intensive agro-pastoral activities, deforestation are documented for this area at least since the early Middle Ages. These activities have been dispersed metals and contributed to the current contamination of soil, leaving here a chemical legacy. We focus our study on Bassiès valley (photo 1) which is a sub-catchment of the upper-Vicdessos Valley (Cf. map 1). The geomorphological shape of the valley results of glacial erosion of the Bassiès monzogranite basement during the last glacial era. Several lakes and mires are formed in this succession of glacial basins and tills. Since 2009, a human-environment observatory (http://w3.ohmpyr.univ-tlse2.fr/) aims to monitor the evolution of human - environment interactions within this geographic zone. Different projects, from botanical research to economic studies through biogeochemistry, are carried out in this context. The aim is to collect data and integrate them to conduct a transdisciplinary research in changing environment.

This PhD project is involved in such context. The idea is to decipher the different natural and anthropogenic factors influencing trace metals flows and accumulation in the catchment, main objectives are to:

  • Understand when and how trace metals inputs occurred in the past, and the relationship with contemporaneous environment (e.g. land use, mining, smelting, etc.)
  • Highlight temporal variability and origin of present atmospheric trace metals inputs
  • Estimate present inventories and the possible release in the case of environmental changes.

 

To answer these questions, we aim to set up a spatio-temporal approach using environmental archives and atmospheric deposition monitoring. Several cores of environmental archives (Peat, Lakes...) will be analysed to reconstruct past deposition of trace metals on Bassiès catchment (Photo 3). These results should be compared with other studies (palynology, charcoal) and historical data to discuss their possible relationships and influence of changes in environmental pressure on trace metals inputs. Multi-coring will be applied on the Bassiès site to see intra-variability and a Pyrenean coring transect to discuss spatial variability in the last 200 years. Temporal dynamic of actual trace metal deposition is assessed by means of atmospheric deposition clean collectors (Photo 4) along altitudinal transects and soil solution collectors. We will install passive fog collectors designed to ultra-trace metal occult deposition. Special insight will be the study of lead isotopic composition in deposition, cores and surface mosses transects for better understanding of lead sources.

This PhD project is led by Adrien CLAUSTRES in the EcoLab, a laboratory of functional ecology and environment at the University of Toulouse, France. This project is directed by Gaël LE ROUX and Anne PROBST, CNRS researchers also at EcoLab. (http://www.ecolab.omp.eu/).

Adrien Claustres, EcoLab, University of Toulouse, France

adrien.claustres@free.fr

Keep up to date

Submit Content

Members can keep in touch with their colleagues through short news and events articles of interest to the SEGH community.

Science in the News

Latest on-line papers from the SEGH journal: Environmental Geochemistry and Health

  • Agro-ecological suitability assessment of Chinese Medicinal Yam under future climate change 2019-10-15

    Abstract

    Chinese Medicinal Yam (CMY) has been prescribed as medicinal food for thousand years in China by Traditional Chinese Medicine (TCM) practitioners. Its medical benefits include nourishing the stomach and spleen to improve digestion, replenishing lung and kidney, etc., according to the TCM literature. As living standard rises and public health awareness improves in recent years, the potential medicinal benefits of CMY have attracted increasing attention in China. It has been found that the observed climate change in last several decades, together with the change in economic structure, has driven significant shift in the pattern of the traditional CMY planting areas. To identify suitable planting area for CMY in the near future is critical for ensuring the quality and supply quantity of CMY, guiding the layout of CMY industry, and safeguarding the sustainable development of CMY resources for public health. In this study, we first collect 30-year records of CMY varieties and their corresponding phenology and agro-meteorological observations. We then consolidate these data and use them to enrich and update the eco-physiological parameters of CMY in the agro-ecological zone (AEZ) model. The updated CMY varieties and AEZ model are validated using the historical planting area and production under observed climate conditions. After the successful validation, we use the updated AEZ model to simulate the potential yield of CMY and identify the suitable planting regions under future climate projections in China. This study shows that regions with high ecological similarity to the genuine and core producing areas of CMY mainly distribute in eastern Henan, southeastern Hebei, and western Shandong. The climate suitability of these areas will be improved due to global warming in the next 50 years, and therefore, they will continue to be the most suitable CMY planting regions.

  • Application of stable isotopes and dissolved ions for monitoring landfill leachate contamination 2019-10-15

    Abstract

    We evaluated groundwater contamination by landfill leachate at a municipal landfill and characterized isotopic and hydrogeochemical evidence of the degradation and natural attenuation of buried organic matter at the study site. Dissolved ion content was generally much higher in the leachate than in the surrounding groundwater. The leachate was characterized by highly elevated bicarbonate and ammonium levels and a lack of nitrate and sulfate, indicating generation under anoxic conditions. Leachate δD and δ13CDIC values were much higher than those of the surrounding groundwater; some groundwater samples near the landfill showed a significant contamination by the leachate plume. Hydrochemical characteristics of the groundwater suggest that aquifer geology in the study area plays a key role in controlling the natural attenuation of leachate plumes in this oxygen-limited environment.

  • Lead transfer into the vegetation layer growing naturally in a Pb-contaminated site 2019-10-10

    Abstract

    The lead was one of the main elements in the glazes used to colour ceramic tiles. Due to its presence, ceramic sludge has been a source of environmental pollution since this dangerous waste has been often spread into the soil without any measures of pollution control. These contaminated sites are often located close to industrial sites in the peri-urban areas, thus representing a considerable hazard to the human and ecosystem health. In this study, we investigated the lead transfer into the vegetation layer (Phragmites australis, Salix alba and Sambucus nigra) growing naturally along a Pb-contaminated ditch bank. The analysis showed a different lead accumulation among the species and their plant tissues. Salix trees were not affected by the Pb contamination, possibly because their roots mainly develop below the contaminated deposit. Differently, Sambucus accumulated high concentrations of lead in all plant tissues and fruits, representing a potential source of biomagnification. Phragmites accumulated large amounts of lead in the rhizomes and, considering its homogeneous distribution on the site, was used to map the contamination. Analysing the Pb concentration within plant tissues, we got at the same time information about the spread, the history of the contamination and the relative risks. Finally, we discussed the role of natural recolonizing plants for the soil pollution mitigation and their capacity on decreasing soil erosion and water run-off.