The temporal variability of atmospheric deposition in Guadeloupe

Le dépôt atmosphérique apporte de nombreux nutriments aux forêts tropicales humides et participe ainsi à la préservation des sols. Son importance est particulière dans la zone caraïbe ou la pluviosité est forte. Ce travail a réalisé une étude temporelle continue de trois ans et demi sur le flux de dépôt en Guadeloupe de 45 éléments (Al, As, Ba, Be, Ca, Cd, Cr, Co, Cu, Fe, K, Li, Mg, Mn, Mo, Na, Ni, P, Pb, Rb, S, Sc, Sb, Se, Sr, Ti, Tl, U, V, Zn et les terres rares) et d'une année sur leur concentration dans l'air. Une analyse isotopique détaillée du strontium (87Sr/ 86Sr), du néodyme (143Nd/ 144Nd) et du plomb ( 206Pb, 207Pb, 208Pb) a été pratiquée sur tous les échantillons où cela a été possible. L'analyse compositionnelle suivant les méthodes développé par Aitchison et ses collaborateurs a été d'une grande aide dans l'interprétation des résultats. Nous avons pu montrer que les deux sources principales du dépôt atmosphérique en Guadeloupe sont les poussières sahariennes trans-atlantiques pour les éléments réputés crustaux comme le fer, l'aluminium, le manganèse, les terres rares, et les sels marins pour les autres éléments comme le magnésium, le sodium, le soufre une partie du molybdène, du potassium et du zinc. On note une très forte variabilité saisonnière pour les apports sahariens avec un pic de dépôt entre avril et septembre. Les analyses des terres rares et des isotopes indiquent une variabilité régionale des sources des poussières sahariennes sans qu'on puisse aujourd'hui les identifier précisément à cause du manque de données quantitatives dans les zones d'émission. On note un fractionnement compositionnel entre le dépôt et l'aérosol mesuré au niveau du sol avec un enrichissement anthropique de ce dernier.Atmospheric deposition provides many nutrients to tropical rain-forests and thus contributes to soil preservation. Its importance is particular in the Caribbean area with high rainfall rate. This work carrried out a continuous temporal study of three and a half years on the deposit flux in Guadeloupe of 45 elements (Al, As, Ba, Be, Ca, Cd, Cr, Co, Cu, Fe, K, Li, Mg, Mn, Mo, Na, Ni, P, Pb, Rb, S, Sc, Sb, Se, Sr, Ti, Tl, U, V, Zn and REEs) and one year on their concentration in air. Detailed isotopic analysis of strontium (87Sr/86Sr), neodymium (143Nd/144Nd) and lead (206Pb, 207Pb, 208Pb) was performed on all samples where possible. The compositional analysis using the methods developed by Aitchison and his collaborators was of great help in the interpretation of the results. We have been able to show that the two main sources of at- mospheric deposition in Guadeloupe are trans-Atlantic Saharan dust for elements considered to be crustal such as iron, aluminium, manganese, REEs, and sea salts for the other elements such as magnesium, sodium, sulfur, and part of molybdenum, potassium and zinc. We note a very strong seasonal variability for the Saharan inflows with a peak of deposition between April and September. Analyses of REEs and iso- topes indicate a regional variability of the sources of Saharan dust without being able today to identify them precisely because of the lack of quantitative data in the emission zones. There is a compositional split between the deposit and the aerosol measured at ground level with some anthropogenic enrichment for aerosol

Étude de la variabilité temporelle du dépôt atmosphérique en Guadeloupe

Atmospheric deposition provides many nutrients to tropical rain-forests and thus contributes to soil preservation. Its importance is particular in the Caribbean area with high rainfall rate. This work carrried out a continuous temporal study of three and a half years on the deposit flux in Guadeloupe of 45 elements (Al, As, Ba, Be, Ca, Cd, Cr, Co, Cu, Fe, K, Li, Mg, Mn, Mo, Na, Ni, P, Pb, Rb, S, Sc, Sb, Se, Sr, Ti, Tl, U, V, Zn and REEs) and one year on their concentration in air. Detailed isotopic analysis of strontium (87Sr/86Sr), neodymium (143Nd/144Nd) and lead (206Pb, 207Pb, 208Pb) was performed on all samples where possible. The compositional analysis using the methods developed by Aitchison and his collaborators was of great help in the interpretation of the results. We have been able to show that the two main sources of at- mospheric deposition in Guadeloupe are trans-Atlantic Saharan dust for elements considered to be crustal such as iron, aluminium, manganese, REEs, and sea salts for the other elements such as magnesium, sodium, sulfur, and part of molybdenum, potassium and zinc. We note a very strong seasonal variability for the Saharan inflows with a peak of deposition between April and September. Analyses of REEs and iso- topes indicate a regional variability of the sources of Saharan dust without being able today to identify them precisely because of the lack of quantitative data in the emission zones. There is a compositional split between the deposit and the aerosol measured at ground level with some anthropogenic enrichment for aerosol.Le dépôt atmosphérique apporte de nombreux nutriments aux forêts tropicales humides et participe ainsi à la préservation des sols. Son importance est particulière dans la zone caraïbe ou la pluviosité est forte. Ce travail a réalisé une étude temporelle continue de trois ans et demi sur le flux de dépôt en Guadeloupe de 45 éléments (Al, As, Ba, Be, Ca, Cd, Cr, Co, Cu, Fe, K, Li, Mg, Mn, Mo, Na, Ni, P, Pb, Rb, S, Sc, Sb, Se, Sr, Ti, Tl, U, V, Zn et les terres rares) et d'une année sur leur concentration dans l'air. Une analyse isotopique détaillée du strontium (87Sr/ 86Sr), du néodyme (143Nd/ 144Nd) et du plomb ( 206Pb, 207Pb, 208Pb) a été pratiquée sur tous les échantillons où cela a été possible. L'analyse compositionnelle suivant les méthodes développé par Aitchison et ses collaborateurs a été d'une grande aide dans l'interprétation des résultats. Nous avons pu montrer que les deux sources principales du dépôt atmosphérique en Guadeloupe sont les poussières sahariennes trans-atlantiques pour les éléments réputés crustaux comme le fer, l'aluminium, le manganèse, les terres rares, et les sels marins pour les autres éléments comme le magnésium, le sodium, le soufre une partie du molybdène, du potassium et du zinc. On note une très forte variabilité saisonnière pour les apports sahariens avec un pic de dépôt entre avril et septembre. Les analyses des terres rares et des isotopes indiquent une variabilité régionale des sources des poussières sahariennes sans qu'on puisse aujourd'hui les identifier précisément à cause du manque de données quantitatives dans les zones d'émission. On note un fractionnement compositionnel entre le dépôt et l'aérosol mesuré au niveau du sol avec un enrichissement anthropique de ce dernier

Atmospheric Deposition Over the Caribbean Region: Sea Salt and Saharan Dust Are Sources of Essential Elements on the Island of Guadeloupe

International audienceDust emitted from North Africa is transported over long distances and has a strong impact on large areas over the North Tropical Atlantic Ocean. Sea salt emitted by the sea surface is the second source of essential elements transported in the atmosphere and plays a major role in the cycles of alkaline-earth metals in the ecosystems of tropical North Atlantic Islands. The total atmospheric deposition fluxes were continuously sampled on a weekly basis in Guadeloupe, Lesser Antilles, from March 2015 to August 2018 (41 months). Elemental deposition fluxes, including Al, Ca, K, Mg, Fe, Na, P, S, and Zn, were measured for all samples to provide the first long time series of atmospheric elemental deposition fluxes over the Lesser Antilles region. It is shown that: (a) the three sources of atmospheric deposits in Guadeloupe for the presented elements are sea salt (for K, Ca, Mg, Na, and S), long-range transported Saharan dust (for Al, Ca, K, and Fe), and biogenic particles (for P and Zn); (b) the average deposition mass fluxes of sea salt and Saharan dust are 17.4 and 11.2 g.m−2.year−1, respectively, without noticeable inter-annual variations; (c) a pronounced seasonality is found for the Saharan dust deposition, for which maximum flux values are observed between June and July each year and 85% of the annual deposition flux occurs between April and September; (d) the deposition flux of sea salt is strongly correlated to local wind speed, without seasonality

Compositional data analysis (CoDA) as a tool to evaluate a new low-cost settling-based PM₁₀ sampling head in a desert dust source region

International audienc

Anthropogenic Perturbations to the Atmospheric Molybdenum Cycle

International audienceMolybdenum (Mo) is a key cofactor in enzymes used for nitrogen (N) fixation and nitrate reduction, and the low availability of Mo can constrain N inputs, affecting ecosystem productivity. Natural atmospheric Mo aerosolization and deposition from sources such as desert dust, sea salt spray, and volcanoes can affect ecosystem function across long timescales, but anthropogenic activities such as combustion, motor vehicles, and agricultural dust have accelerated the natural Mo cycle. Here we combined a synthesis of global atmospheric concentration observations and modeling to identify and estimate anthropogenic sources of atmospheric Mo. To project the impact of atmospheric Mo on terrestrial ecosystems, we synthesized soil Mo data and estimated the global distribution of soil Mo using two approaches to calculate turnover times. We estimated global emissions of atmospheric Mo in aerosols (-1, with 40%-75% from anthropogenic sources. We approximated that for the top meter of soil, Mo turnover times range between 1,000 and 1,000,000 years. In some industrialized regions, anthropogenic inputs have enhanced Mo deposition 100 fold, lowering the soil Mo turnover time considerably. Our synthesis of global observational data, modeling, and a mass balance comparison with riverine Mo exports suggest that anthropogenic activity has greatly accelerated the Mo cycle, with potential to influence N limited ecosystems

Data from: Anthropogenic Perturbations to the Atmospheric Molybdenum Cycle

Molybdenum (Mo) is an essential trace element that is, important for terrestrial and aquatic ecosystems, as it is required for biological nitrogen fixation and uptake. Mo is carried in particles to the atmosphere from sources such as desert dust, sea spray, and volcanoes resulting in losses and sources to different ecosystems. Atmospheric Mo deposition is essential on long time scales for soils which have lost Mo due to soil weathering, with consequences for nitrogen cycling. Anthropogenic changes to the Mo cycle from combustion, motor vehicles, and agricultural dust, are likely to be large, and have more than doubled sources of Mo to the atmosphere. Locally, anthropogenic changes to Mo in industrialized regions can represent a 100‐fold increase in deposition, and may affect nitrogen cycling in nitrogen‐limited ecosystems. This dataset supports these findings.We acknowledge the Atkinson Center for funding for this project, and NSF CCF-1522054