Non-steady-state biological removal of atmospheric particles from Mediterranean surface waters

Differences in the sensitivity to Cu and ligand production of coastal vs offshore strains of Emiliania huxleyi

Copper is an essential trace metal for different physiological processes in phytoplankton, being either a limiting or toxic element depending on its bioavailability, which may induce local physiological adaptations. Atmospheric Cu deposition to the oceans can negatively impact phytoplankton growth, with the most Cu-sensitive phytoplankton exhibiting differences based on coastal vs oceanic origin. The goal of this work was to analyze sensitivity to Cu toxicity of the cosmopolitan marine calcifying phytoplankton, Emiliania huxleyi, exploring what factors determine intraspecific variability in sensitivity. We compared 17 strains isolated from coastal and open ocean waters of the Eastern South Pacific (ESP), the Mediterranean Sea, and the Tasman Sea. Offshore strains were as sensitive to Cu than coastal strains. Sensitivity to Cu was explained well by predicted depositional inputs of atmospheric Cu in the ESP both for coastal and offshore strains, but not when considered globally. The variability in Cu-sensitivity was also due to the production of organic Cu-ligands (CL), being the most productive strains the most tolerant to Cu at constitutive levels. When exposed to 100nM Cu, E. huxleyi produced significantly higher amounts of CL, especially coastal strains, but CL production did not correlate to observed EC50s.

PM10 composition during an intense Saharan dust transport event over Athens (Greece)

The influence of Saharan dust on the air quality of Southern European big cities became a priority during the last decade. The present study reports results on PM(10) monitored at an urban site at 14 m above ground level during an intense Saharan dust transport event. The elemental composition was determined by Energy Dispersive X-ray Fluorescence Spectrometry (EDXRF) for 12 elements: Si, Al, Fe, K, Ca, Mg, Ti, S, Ni, Cu, Zn and Mn. PM(10) concentrations exceeded the EU limit (50 μg/m(3)) several times during the sampling period. Simultaneous maxima have been observed for the elements of crustal origin. The concentrations of all the elements presented a common maximum, corresponding to the date where the atmosphere was heavily charged with particulate matter permanently for an interval of about 10h. Sulfur and heavy metal concentrations were also associated to local emissions. Mineral dust represented the largest fraction of PM(10) reaching 79%. Seven days back trajectories have shown that the air masses arriving over Athens, originated from Western Sahara. Scanning Electron Microscopy coupled with Energy Dispersive X-ray analysis (SEM-EDX) revealed that particle agglomerates were abundant, most of them having sizes <2 μm. Aluminosilicates were predominant in dust particles also rich in calcium which was distributed between calcite, dolomite, gypsum and Ca-Si particles. These results were consistent with the origin of the dust particles and the elemental composition results. Sulfur and heavy metals were associated to very fine particles <1 μm.

Recent accumulation of trace metals in sediments at the DYFAMED site (Northwestern Mediterranean Sea)

The DYFAMED site (Ligurian Sea, 43 degrees 25'N; 7 degrees 52'E) has been the subject of multidisciplinary research since 1987, including the study of atmospheric deposition of metals and their association with marine particles in the water column. On the other hand, the attention paid to the underlying sediments as the ultimate repository of elements, particularly pollutants, has been considerably lesser. Through the combined use of (210)Pb chronologies and elemental analysis, we studied the concentrations and fluxes of trace metals (Zn, Pb, Ni, Cu, Cr) in a sediment core collected from approximately 2300 m water depth at the seafloor beneath DYFAMED. Surface metal enrichment during the 20th century is apparent in the case of Pb, Zn and Cu (maximum enrichment factors 1.5, 1.2 and 1.4, respectively). A comparison with published data suggests that atmospheric deposition is the main entrance route of anthropogenic trace metals accumulated in the recent sediments, while lateral advection of sediments by currents and sediment gravity flows is proposed to account for the pre-industrial concentrations of metals. Recent atmospheric inputs of Pb and Cu are more efficiently stored in sediments with respect to Zn, most of which is apparently advected elsewhere.

Atmospheric deposition of metallic pollutants over the Ligurian Sea: labile and residual inputs

Atmospheric fluxes of six trace metals (Cd, Cr, Cu, Ni, Pb and Zn) with Al as a crustal reference were measured at Cap Ferrat (French Riviera) between February 1997 and July 1998. An original sampling protocol enabled the separation of labile (seawater at pH 2) and residual fractions in the total atmospheric input. Median acid-labile fractions were 91%, 69%, 83%, 84%, 97% and 98% of the total for Cd, Cr, Cu, Ni, Pb and Zn, respectively. Under the conditions used, lability of individual metals is related to the anthropogenic component of the samples. Enrichment factors and anthropogenic fraction are estimated for each metal. Some interannual changes are investigated (Pb, Zn). The observed increase of Zn inputs may be linked to local input from the Nice district waste plant (commissioned in 1988), 6.5 km away.