The impact of vegetation on fractionation of rare earth elements(REE) during water–rock interaction

Previous studies on waters of a streamlet in the Vosges mountains (eastern France) have shown that Sr and rare earth elements (REE) principally originate from apatite dissolution during weathering. However, stream water REE patterns normalized to apatite are still depleted in light REE (LREE, La–Sm) pointing to the presence of an additional LREE depleting process. Speciation calculations indicate that complexation cannot explain this additional LREE depletion. In contrast, vegetation samples are strongly enriched in LREE compared to water and their Sr and Nd isotopic compositions are comparable with those of apatite and waters. Thus, the preferential LREE uptake by the plants at the root–water–soil (apatite) interface might lead to an additional LREE depletion of the waters in the forested catchment. Mass balance calculations indicate that the yearly LREE uptake by vegetation is comparable with the LREE export by the streamlet and, therefore, might be an important factor controlling the LREE depletion in river waters

Twenty-five year record of chemicals in open field precipitation and throughfall from a medium-altitude forest catchment (Strengbach - NE France): an obvious response to atmospheric pollution trends.

This study concerned a 25 yr continuous record of bulk precipitation and throughfall composition in a medium-altitude forested environment. The 1986-2012 survey from the more intense acid rain period in the mid-eighties until the present allowed the quantification of the interaction between atmospheric deposition and vegetation and the long-term evolution following pollutant emission trends. The long-term monitoring evidenced some significant temporal trends (pH, conductivity, SO42-, Cl-, NO3-, Ca2+, Mg2+, and K+). Significant decreases in the concentrations and fluxes of several ions were observed (H+ and SO42-, Cl-, and Ca2+) in open field precipitation and throughfalls. The regular and strong decrease in protons and sulfate followed the decreases in anthropogenic SO2 and NOx (proton precursors) since the 1980s. The decrease in Cl- concentrations was weaker and could have been related to the regional reduction in HCl emissions and/or to changes in the precipitation regime. The annual calcium fluxes were reduced from approximately 15 to 9 and 6 to 2 kg.ha-1 under spruces and beeches, respectively, as a consequence of reductions in anthropogenic industrial dust. In such calcium-limited resource soils, the atmospheric Ca flux exceeded the Ca flux from mineral weathering and was highly bioavailable for vegetation growth. This decrease in nutrient input had strong consequences for soil nutrients and may thus have participated in forest decline. The two tree plantations had contrasting effects on the physico-chemical parameters of the incoming precipitation with higher water interception and chemical concentrations under spruces than under beeches, which underlined the role of tree species in atmospheric inputs to soils. The structure and persistence of spruce needles enhanced the capture of particles and water, accentuating the acidity of the deposition and leading to the intensification of acidification processes, nutrient leaching in soils and forest decline. In contrast, beech leaves were able to neutralize a portion of the atmospheric protons, which minimized and reduced the negative effects of acid rain. In addition, the throughfalls represented an important part of the biological cycle of trees for some elements such as K or N, as indicated by the contrasting patterns at year and long-term scales regarding the vegetation type. However, our study indicated that the influence of tree species might change over time with changes in atmospheric pollution, in precipitation regime, or in stand structure. This study outlined the importance of the long-term record of open field precipitation and throughfalls under various tree types to better evaluate the real inputs of elements to forest ecosystems and among them, essential mineral nutrients

Twenty-five year record of chemicals in open field precipitation and throughfall from a medium-altitude forest catchment (Strengbach - NE France): an obvious response to atmospheric pollution trends.

This study concerned a 25 yr continuous record of bulk precipitation and throughfall composition in a medium-altitude forested environment. The 1986-2012 survey from the more intense acid rain period in the mid-eighties until the present allowed the quantification of the interaction between atmospheric deposition and vegetation and the long-term evolution following pollutant emission trends. The long-term monitoring evidenced some significant temporal trends (pH, conductivity, SO42-, Cl-, NO3-, Ca2+, Mg2+, and K+). Significant decreases in the concentrations and fluxes of several ions were observed (H+ and SO42-, Cl-, and Ca2+) in open field precipitation and throughfalls. The regular and strong decrease in protons and sulfate followed the decreases in anthropogenic SO2 and NOx (proton precursors) since the 1980s. The decrease in Cl- concentrations was weaker and could have been related to the regional reduction in HCl emissions and/or to changes in the precipitation regime. The annual calcium fluxes were reduced from approximately 15 to 9 and 6 to 2 kg.ha-1 under spruces and beeches, respectively, as a consequence of reductions in anthropogenic industrial dust. In such calcium-limited resource soils, the atmospheric Ca flux exceeded the Ca flux from mineral weathering and was highly bioavailable for vegetation growth. This decrease in nutrient input had strong consequences for soil nutrients and may thus have participated in forest decline. The two tree plantations had contrasting effects on the physico-chemical parameters of the incoming precipitation with higher water interception and chemical concentrations under spruces than under beeches, which underlined the role of tree species in atmospheric inputs to soils. The structure and persistence of spruce needles enhanced the capture of particles and water, accentuating the acidity of the deposition and leading to the intensification of acidification processes, nutrient leaching in soils and forest decline. In contrast, beech leaves were able to neutralize a portion of the atmospheric protons, which minimized and reduced the negative effects of acid rain. In addition, the throughfalls represented an important part of the biological cycle of trees for some elements such as K or N, as indicated by the contrasting patterns at year and long-term scales regarding the vegetation type. However, our study indicated that the influence of tree species might change over time with changes in atmospheric pollution, in precipitation regime, or in stand structure. This study outlined the importance of the long-term record of open field precipitation and throughfalls under various tree types to better evaluate the real inputs of elements to forest ecosystems and among them, essential mineral nutrients

Dépôt d'échantillon sur filament métallique

Dépôt d'échantillon sur filament métallique en vue d'analyse isotopique par TIM

Parcelle expérimentale d'épicéas

Stations épicéas -- Parcelle expérimentale d'épicéas où sont étudiés les pluviolessivats, les solutions de sol, des profils pédologiques, la litière et la végétation

Vue du bassin-versant du Strengbach

Vue du bassin-versant du Strengbach (Vosges

Influence hydrothermale dans les sédiments de fosses de la mer Rouge par l'étude de quelques éléments traces

The Cu, Ni, Fe, Cr and Zr concentrations were evaluated to study the influence of hydrothermal activity on the sediments of six Red-Sea deeps. Comparison between the Ni/Fe and Cu/Fe ratios supports distinction between hydrothermal and non-hydrothermal sediments, whereas anti-correlation between Zr and Cr concentrations results from hydrothermal influence. The results allow us to envisage that the sediments of the Suakin Deep did not undergo a hydrothermal activity and that this hydrothermal influence was weak in the Valdivia Deep. The sediments of Port-Soudan Deep recorded a hydrothermal activity, whereas this activity was the strongest in the Thetis and Atlantis II deeps.Les teneurs en Cu, Ni, Fe, Cr et Zr servent ici à évaluer l'influence d'une activité hydrothermale sur les sédiments de six fosses de la mer Rouge. Ainsi, l'enrichissement en fer (Fe) et en cuivre (Cu) des fluides hydrothermaux provenant du lessivage de la croûte océanique se retrouve dans les sédiments hydrothermaux alors que le nickel (Ni) est essentiellement apporté par l'eau de mer. La comparaison des rapports Ni/Fe et Cu/Fe représente donc un bon paramètre de discrimination entre les sédiments biodétritiques et ceux d'origine hydrothermale. Le chrome (Cr) et le zirconium (Zr) proviennent essentiellement du matériel détritique dans les sédiments marins normaux et sont corrélés, alors que l'absence de corrélation entre ces deux métaux est un indice d'une activité hydrothermale. Les résultats cumulés montrent que les sédiments de la fosse Suakin n'ont pas subi d'influence hydrothermale, et que celle-ci est très faible dans la fosse Valdivia. Les sédiments de la fosse Port-Soudan ont aussi enregistré les effets d'arrivées hydrothermales, mais l'activité hydrothermale est la plus importante et la plus nette dans la fosse Thétis et, surtout, dans celle d'Atlantis II

Sr, Pb isotopes and REE analyses of five cores of the Red Sea: An insight into hydrothermal input

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