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

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## Science in theNews

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

• Fertilizer usage and cadmium in soils, crops and food 2018-06-23

### Abstract

Phosphate fertilizers were first implicated by Schroeder and Balassa (Science 140(3568):819–820, 1963) for increasing the Cd concentration in cultivated soils and crops. This suggestion has become a part of the accepted paradigm on soil toxicity. Consequently, stringent fertilizer control programs to monitor Cd have been launched. Attempts to link Cd toxicity and fertilizers to chronic diseases, sometimes with good evidence, but mostly on less certain data are frequent. A re-assessment of this “accepted” paradigm is timely, given the larger body of data available today. The data show that both the input and output of Cd per hectare from fertilizers are negligibly small compared to the total amount of Cd/hectare usually present in the soil itself. Calculations based on current agricultural practices are used to show that it will take centuries to double the ambient soil Cd level, even after neglecting leaching and other removal effects. The concern of long-term agriculture should be the depletion of available phosphate fertilizers, rather than the negligible contamination of the soil by trace metals from fertilizer inputs. This conclusion is confirmed by showing that the claimed correlations between fertilizer input and Cd accumulation in crops are not robust. Alternative scenarios that explain the data are presented. Thus, soil acidulation on fertilizer loading and the effect of Mg, Zn and F ions contained in fertilizers are considered using recent $$\hbox {Cd}^{2+}$$ , $$\hbox {Mg}^{2+}$$ and $$\hbox {F}^-$$ ion-association theories. The protective role of ions like Zn, Se, Fe is emphasized, and the question of Cd toxicity in the presence of other ions is considered. These help to clarify difficulties in the standard point of view. This analysis does not modify the accepted views on Cd contamination by airborne delivery, smoking, and industrial activity, or algal blooms caused by phosphates.

• Effects of conversion of mangroves into gei wai ponds on accumulation, speciation and risk of heavy metals in intertidal sediments 2018-06-23

### Abstract

Mangroves are often converted into gei wai ponds for aquaculture, but how such conversion affects the accumulation and behavior of heavy metals in sediments is not clear. The present study aims to quantify the concentration and speciation of heavy metals in sediments in different habitats, including gei wai pond, mangrove marsh dominated by Avicennia marina and bare mudflat, in a mangrove nature reserve in South China. The results showed that gei wai pond acidified the sediment and reduced its electronic conductivity and total organic carbon (TOC) when compared to A. marina marsh and mudflat. The concentrations of Cd, Cu, Zn and Pb at all sediment depths in gei wai pond were lower than the other habitats, indicating gei wai pond reduced the fertility and the ability to retain heavy metals in sediment. Gei wai pond sediment also had a lower heavy metal pollution problem according to multiple evaluation methods, including potential ecological risk coefficient, potential ecological risk index, geo-accumulation index, mean PEL quotients, pollution load index, mean ERM quotients and total toxic unit. Heavy metal speciation analysis showed that gei wai pond increased the transfer of the immobilized fraction of Cd and Cr to the mobilized one. According to the acid-volatile sulfide (AVS) and simultaneously extracted metals (SEM) analysis, the conversion of mangroves into gei wai pond reduced values of ([SEM] − [AVS])/f oc , and the role of TOC in alleviating heavy metal toxicity in sediment. This study demonstrated the conversion of mangrove marsh into gei wai pond not only reduced the ecological purification capacity on heavy metal contamination, but also enhanced the transfer of heavy metals from gei wai pond sediment to nearby habitats.

• Cytotoxicity induced by the mixture components of nickel and poly aromatic hydrocarbons 2018-06-22

### Abstract

Although particulate matter (PM) is composed of various chemicals, investigations regarding the toxicity that results from mixing the substances in PM are insufficient. In this study, the effects of low levels of three PAHs (benz[a]anthracene, benzo[a]pyrene, and dibenz[a,h]anthracene) on Ni toxicity were investigated to assess the combined effect of Ni–PAHs on the environment. We compared the difference in cell mortality and total glutathione (tGSH) reduction between single Ni and Ni–PAHs co-exposure using A549 (human alveolar carcinoma). In addition, we measured the change in Ni solubility in chloroform that was triggered by PAHs to confirm the existence of cation–π interactions between Ni and PAHs. In the single Ni exposure, the dose–response curve of cell mortality and tGSH reduction were very similar, indicating that cell death was mediated by the oxidative stress. However, 10 μM PAHs induced a depleted tGSH reduction compared to single Ni without a change in cell mortality. The solubility of Ni in chloroform was greatly enhanced by the addition of benz[a]anthracene, which demonstrates the cation–π interactions between Ni and PAHs. Ni–PAH complexes can change the toxicity mechanisms of Ni from oxidative stress to others due to the reduction of Ni2+ bioavailability and the accumulation of Ni–PAH complexes on cell membranes. The abundant PAHs contained in PM have strong potential to interact with metals, which can affect the toxicity of the metal. Therefore, the mixture toxicity and interactions between diverse metals and PAHs in PM should be investigated in the future.