scholarly journals Contrasted release of insoluble elements (Fe, Al, rare earth elements, Th, Pa) after dust deposition in seawater: a tank experiment approach

2021 ◽  
Vol 18 (8) ◽  
pp. 2663-2678
Author(s):  
Matthieu Roy-Barman ◽  
Lorna Foliot ◽  
Eric Douville ◽  
Nathalie Leblond ◽  
Fréderic Gazeau ◽  
...  
Keyword(s):  
Rare Earth ◽  
Rare Earth Elements ◽  
Saharan Dust ◽  
Tyrrhenian Sea ◽  
Ionian Sea ◽  
Dust Deposition ◽  
Climate Conditions ◽  
Ph Influence ◽  
Initial Release ◽  
Tank Experiment

Abstract. Lithogenic elements such as aluminum (Al), iron (Fe), rare earth elements (REEs), thorium (232Th and 230Th, given as Th) and protactinium (Pa) are often assumed to be insoluble. In this study, their dissolution from Saharan dust reaching Mediterranean seawater was studied through tank experiments over 3 to 4 d under controlled conditions including controls without dust addition as well as dust seeding under present and future climate conditions (+3 ∘C and −0.3 pH). Unfiltered surface seawater from three oligotrophic regions (Tyrrhenian Sea, Ionian Sea and Algerian Basin) were used. The maximum dissolution was low for all seeding experiments: less than 0.3 % for Fe, 1 % for 232Th and Al, about 2 %–5 % for REEs and less than 6 % for Pa. Different behaviors were observed: dissolved Al increased until the end of the experiments, Fe did not dissolve significantly, and Th and light REEs were scavenged back on particles after a fast initial release. The constant 230Th/232Th ratio during the scavenging phase suggests that there is little or no further dissolution after the initial Th release. Quite unexpectedly, comparison of present and future conditions indicates that changes in temperature and/or pH influence the release of Th and REEs in seawater, leading to lower Th release and a higher light REE release under increased greenhouse conditions.

scholarly journals Contrasted release of insoluble elements (Fe, Al, REE, Th, Pa) after dust deposition in seawater: a tank experiment approach

2020 ◽  
Author(s):  
Matthieu Roy-Barman ◽  
Lorna Folio ◽  
Eric Douville ◽  
Nathalie Leblond ◽  
Fréderic Gazeau ◽  
...  
Keyword(s):  
Rare Earth ◽  
Saharan Dust ◽  
Tyrrhenian Sea ◽  
Ionian Sea ◽  
Surface Seawater ◽  
Dust Deposition ◽  
Climate Conditions ◽  
Ph Influence ◽  
Initial Release ◽  
Tank Experiment

Abstract. The release of lithogenic elements (which are often assumed to be insoluble) such as Aluminum (Al), Iron (Fe), Rare Earth Elements (REE), Thorium (Th) and Protactinium (Pa) by Saharan dust reaching Mediterranean seawater was studied through tank experiments over 3 to 4 days under controlled conditions including control without dust addition and dust seeding under present and future climate conditions (+3 °C and −0.3 pH unit). Unfiltered surface seawater from 3 oligotrophic regions (Tyrrhenian Sea, Ionian Sea and Algerian Basin) were used. The maximum dissolution fractions were low for all seeding experiments: less than 0.3 % for Fe, 1 % for 232Th and Al, about 2–5 % for REE and less than 6 % for Pa. Different behaviors were observed: dissolved Al increased until the end of the experiments, Fe did not dissolve significantly and Th and light REE were scavenged back on the particles after a fast initial release. The constant 230Th/232Th ratio during the scavenging phase suggests that there is little or no further dissolution after the initial Th release. Quite unexpectedly, comparison of present and future conditions indicates that changes in temperature and/or pH influence the release of thorium and REE in seawater, leading to a lower Th release and a higher light REE release under increased greenhouse conditions.

scholarly journals Impact of dust addition on Mediterranean plankton communities under present and future conditions of pH and temperature: an experimental overview

2021 ◽  
Vol 18 (17) ◽  
pp. 5011-5034
Author(s):  
Frédéric Gazeau ◽  
Céline Ridame ◽  
France Van Wambeke ◽  
Samir Alliouane ◽  
Christian Stolpe ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
Surface Waters ◽  
External Source ◽  
Saharan Dust ◽  
Tyrrhenian Sea ◽  
Dust Deposition ◽  
Climate Conditions ◽  
Autotrophic Biomass ◽  
Biogeochemical Parameters ◽  
Plankton Communities

Abstract. In low-nutrient low-chlorophyll areas, such as the Mediterranean Sea, atmospheric fluxes represent a considerable external source of nutrients likely supporting primary production, especially during periods of stratification. These areas are expected to expand in the future due to lower nutrient supply from sub-surface waters caused by climate-driven enhanced stratification, likely further increasing the role of atmospheric deposition as a source of new nutrients to surface waters. Whether plankton communities will react differently to dust deposition in a warmer and acidified environment remains; however, an open question. The potential impact of dust deposition both in present and future climate conditions was investigated in three perturbation experiments in the open Mediterranean Sea. Climate reactors (300 L) were filled with surface water collected in the Tyrrhenian Sea, Ionian Sea and in the Algerian basin during a cruise conducted in the frame of the PEACETIME project in May–June 2017. The experiments comprised two unmodified control tanks, two tanks enriched with a Saharan dust analogue and two tanks enriched with the dust analogue and maintained under warmer (+3 ∘C) and acidified (−0.3 pH unit) conditions. Samples for the analysis of an extensive number of biogeochemical parameters and processes were taken over the duration (3–4 d) of the experiments. Dust addition led to a rapid release of nitrate and phosphate, however, nitrate inputs were much higher than phosphate. Our results showed that the impacts of Saharan dust deposition in three different basins of the open northwestern Mediterranean Sea are at least as strong as those observed previously, all performed in coastal waters. The effects of dust deposition on biological stocks were different for the three investigated stations and could not be attributed to differences in their degree of oligotrophy but rather to the initial metabolic state of the community. Ocean acidification and warming did not drastically modify the composition of the autotrophic assemblage, with all groups positively impacted by warming and acidification. Although autotrophic biomass was more positively impacted than heterotrophic biomass under future environmental conditions, a stronger impact of warming and acidification on mineralization processes suggests a decreased capacity of Mediterranean surface plankton communities to sequester atmospheric CO2 following the deposition of atmospheric particles.

scholarly journals Impact of dust enrichment on Mediterranean plankton communities under present and future conditions of pH and temperature: an experimental overview

2020 ◽  
Author(s):  
Frédéric Gazeau ◽  
Céline Ridame ◽  
France Van Wambeke ◽  
Samir Alliouane ◽  
Christian Stolpe ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
Surface Waters ◽  
Future Climate ◽  
Saharan Dust ◽  
Future Climate Change ◽  
Tyrrhenian Sea ◽  
Dust Deposition ◽  
The Future ◽  
The Impact ◽  
Plankton Communities

Abstract. In Low Nutrient Low Chlorophyll areas, such as the Mediterranean Sea, atmospheric fluxes represent a considerable external source of nutrients likely supporting primary production especially during stratification periods. These areas are expected to expand in the future due to lower nutrient supply from sub-surface waters caused by enhanced stratification, likely further increasing the role of atmospheric deposition as a source of new nutrients to surface waters. Yet, whether plankton communities will react differently to dust deposition in a warmer and acidified environment remains an open question. The impact of dust deposition both in present and future climate conditions was assessed through three perturbation experiments in the open Mediterranean Sea. Climate reactors (300 L) were filled with surface water collected in the Tyrrhenian Sea, Ionian Sea and in the Algerian basin during a cruise conducted in May/June 2017 in the frame of the PEACETIME project. The experimental protocol comprised two unmodified control tanks, two tanks enriched with a Saharan dust analog and two tanks enriched with the dust analog and maintained under warmer (+3 °C) and acidified (−0.3 pH unit) conditions. Samples for the analysis of an extensive number of biogeochemical parameters and processes were taken over the duration of the experiments (3–4 d). Here, we present the general setup of the experiments and the impacts of dust seeding and/or future climate change scenario on nutrients and biological stocks. Dust addition led to a rapid and maximum input of nitrate whereas phosphate release from the dust analog was much smaller. Our results showed that the impacts of Saharan dust deposition in three different basins of the open Northwestern Mediterranean Sea are at least as strong as those observed previously in coastal waters. However, interestingly, the effects of dust deposition on biological stocks were highly different between the three investigated stations and could not be attributed to differences in their degree of oligotrophy but rather to the initial metabolic state of the community. Finally, ocean acidification and warming did not drastically modify the composition of the autotrophic assemblage with all groups positively impacted by warming and acidification, suggesting an exacerbation of effects from atmospheric dust deposition in the future.

scholarly journals Impact of dust addition on the microbial food web under present and future conditions of pH and temperature

2021 ◽  
Author(s):  
Julie Dinasquet ◽  
Estelle Bigeard ◽  
Frédéric Gazeau ◽  
Farooq Azam ◽  
Cécile Guieu ◽  
...  
Keyword(s):  
Food Web ◽  
Mediterranean Sea ◽  
Environmental Conditions ◽  
Western Mediterranean ◽  
Microbial Loop ◽  
Saharan Dust ◽  
Tyrrhenian Sea ◽  
Dust Deposition ◽  
Top Down ◽  
The Impact

Abstract. In the oligotrophic waters of the Mediterranean Sea, during the stratification period, the microbial loop relies on pulsed inputs of nutrients through atmospheric deposition of aerosols from both natural (Saharan dust) and anthropogenic origins. While the influence of dust deposition on microbial processes and community composition is still not fully constrained, the extent to which future environmental conditions will affect dust inputs and the microbial response is not known. The impact of atmospheric wet dust deposition was studied both under present and future (warming and acidification) environmental conditions through experiments in 300 L climate reactors. Three dust addition experiments were performed with surface seawater collected from the Tyrrhenian Sea, Ionian Sea and Algerian basin in the Western Mediterranean Sea during the PEACETIME cruise in May–June 2017. Top-down controls on bacteria, viral processes and community, as well as microbial community structure (16S and 18S rDNA amplicon sequencing) were followed over the 3–4 days experiments. Different microbial and viral responses to dust were observed rapidly after addition and were most of the time higher when combined to future environmental conditions. The input of nutrients and trace metals changed the microbial ecosystem from bottom-up limited to a top-down controlled bacterial community, likely from grazing and induced lysogeny. The composition of mixotrophic microeukaryotes and phototrophic prokaryotes was also altered. Overall, these results suggest that the effect of dust deposition on the microbial loop is dependent on the initial microbial assemblage and metabolic state of the tested water, and that predicted warming, and acidification will intensify these responses, affecting food web processes and biogeochemical cycles.

Flame spectra of the rare-earth elements*

1962 ◽  
Vol 18 (4) ◽  
pp. 1127-1153
Author(s):  
V FASSEL ◽  
R CURRY ◽  
R KNISELEY
Keyword(s):  
Rare Earth ◽  
Rare Earth Elements ◽  
The Rare Earth
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