Holocene Records of Aerosols in Continental Environments (HoRACE)

G. Le Roux* (1), F. De Vleeschouwer (1,2), A. Cheburkin (3), M. Krachler (3),W. Shotyk (3), N. Mattielli (4), N. Fagel (1)

(1) Unité de Recherche Argiles et Paléoclimats (URAP), Géochimie sédimentaire : environnement marin et continentaux, Département de Géologie, B18, Sart-Tilman, Allée du 6 Août, B-4000 Liège Belgique,
(2) GADAM Centre of Excellence, Gliwice Absolute Dating Methods Centre,
Krzywoustego 2, 44-100 Gliwice, Poland
(3) Institute of Environmental Geochemistry, University of Heidelberg
(4) Isotope Petrology and Environment, Université Libre de Bruxelles

*gael.le.roux.pro@gmail.com

Present and future environmental changes, including climate change, will induce variations in atmospheric particle loading that have necessarily environmental feedbacks. It is widely accepted that comparing results of Global Climate Models (GCM) with palaeoenvironmental data is the best way to test their performance of prediction. Europe is especially influenced by Sahara: its source strength for dust transport to Europe was estimated at 80–120×106 t year−1. The changing
frequency of Saharan dust events over recent decades has been noted by several authors. Apart ice records, there is no Holocene perspective on these environmental changes in Europe. Records of dust loading summarized in the network DIRTMAP exist for different places in the world on a 102-103 ky. timescale. However, there are no precise investigations on dust loading on a shorter timescale and for the Holocene in Europe. Peat cores from ombrotrophic peatlands can offer high-resolution records of dust intensity and origin in Europe. During the last 20 years, cores from ombrotrophic Sphagnum peatlands have proved to be meaningful archives of atmospheric deposition of trace elements. Lead especially has been extensively studied and its immobility in the peat column is now well demonstrated. Whereas the potential of peat cores as archives of recent and ancient pollutions has been increasingly investigated, using peat cores as archives of atmospheric deposition of trace elements for the entire Holocene remains less investigated. This presentation will first focus on our progress in sampling, analyses and age dating peat profiles to offer a continuous record of atmospheric trace elements deposition and the possibility to compare them with other archives. The behaviour of useful elements like Sr, Rb or REE will also briefly be discussed in order to trace dust origin. Then first results on dust variability investigated in European peat cores will be presented. Local changes in atmospheric dust composition are recorded in peat bogs and could be compared to global records of polar ice cores. For example, this study shows that there is a sharp change in the dust geochemical composition around 3700 B.C. (around 5700 B.P.) recorded in peat cores from Europe. The reason of this change lasting not longer than ca. 100-200 y could be due to a variation in atmospheric sources of dust during the Middle-Holocene. At this time, major climatic changes occurred in Africa as recorded in tropical lakes sediments and Kilimanjaro ice core (+ ref?). A change in the regime of Sahara dust emission, which is the main contributor to natural dust in Europe, can therefore explain this abrupt shift in deposited dust composition for the European bogs. Finally, future work on isotope and mineralogical investigations of Holocene peat samples will be presented in order to trace dust origin.