Hydrocarbons in size-fractionated plankton of the Mediterranean Sea (MERITE-HIPPOCAMPE campaign)

International audienc

Seasonal variations of metals and metalloids in atmospheric particulate matter (PM2.5) in the urban megacity Hanoi

International audienceFine particulate matter (PM2.5) in the atmosphere is of particular concern due to its adverse effects on human health and its impact on global warming. southeast Asia is a hot spot for fossil fuel combustion with recurrent release of large plumes spreading over the ocean and neighbouring countries. Due to the complex mixture of PM2.5, the atmospheric sources contribution related to local and regional emissions in Hanoi (northern Vietnam) is still ill-constrained. Here, we present a year-round study (November 2019 to December 2020) with measurements of 18 metals and metalloids (MM) and lead isotopes in the PM2.5 fraction to quantify weather-related atmospheric inputs and to assess risk to human health. Anthropogenic inputs from fossil fuel combustion accounted for about 80% in PM2.5. We found high PM2.5-bound MM concentrations often exceeding national and global standards with a low risk of chronic inhalation and carcinogenicity, mainly attributable to Cr. During winter monsoon (northeastern winds), stable weather conditions led to the enrichment of long-range air mass transport of local particulate emissions. During the summer monsoon (southeastern winds), warm and moist winds reduced coal contribution in PM2.5. Our study highlights the need for a strict implementation of policies to control hazardous MM emissions by reducing fossil fuel combustion. On the one hand, reducing coal-related activities could reduce Cr emissions and therefore improve the risks to human health. On the other hand, public policies should encourage conversion to green transport in order to reduce petrol combustion and thus limit global warming

Optical characterization of black carbon-derived DOM: Implication for the fluorescence detection of fuel combustion products in marine waters

International audienceAmong pollutants released from shipping, black carbon (BC), also known as soot carbon, is of great interest dueto its impacts on climate, air quality, human health and ecosystems. BC emitted from ships may enter marinewaters and partially transfer to the seawater dissolved phase. In this study, we investigated the optical properties(absorbance and fluorescence) of dissolved organic matter (DOM) derived from BC particles (DOMBC) emitted byships, which were compared to those of DOMBC of other origins (diesel-powered industrial machine, biomassburning, urban dust), and to terrestrial and marine DOM (DOMTER, DOMMAR). Ship and diesel DOMBC displayedhigher ratios of fluorescence maximum intensity to dissolved organic carbon concentration (Fmax/DOC), higherspecific UV absorbance at 254 nm (SUVA254), and lower fluorescence emission wavelengths than the other testedmaterials. The parallel factor analysis (PARAFAC)-derived fluorophores of the ship and diesel DOMBC exhibitedsignificant correlations with the concentration of dissolved black carbon (DBC), determined using the benzenepolycarboxylic acid (BPCA) method. Based on these results, we propose the Combustion indeX (COX), to help detecting and tracking ship/fuel combustion pollutions in marine water

Assessing the bioavailability of black carbon-derived dissolved organic matter for marine heterotrophic prokaryotes

Here we investigated the bioavailability of black carbon (BC)-derived dissolved organic matter (DOM) for a natural mixed community of marine heterotrophic prokaryotes. We ran an in vitro biodegradation experiment that took place over 3 months and exposed a community of organisms collected in the northwestern Mediterranean Sea (Bay of Marseille, France) to three different soluble fractions of BC prepared in the laboratory from various fossil fuel combustion particulates: standard diesel (DREF), oxidized diesel (DREF-OX), and natural samples of ship soot (DSHIP). Over the course of the three months, we observed significant decreases in the concentrations of dissolved organic carbon (DOC; from 9 to 21 %), dissolved BC (DBC; from 22 to 38 %) and dissolved polycyclic aromatic hydrocarbons (d-PAH; from 24 to 64 %) along with variability in the growth dynamics and activity of the heterotrophic prokaryotic community. The heterotrophic prokaryotic community exposed to DREF-OX treatment showed the highest values of respiration and production and the highest cell abundance, associated with the highest decrease in DOC (21 %) and d-PAH (64 %) concentrations. In the DREF and DSHIP treatments, prokaryotic activity was oriented towards anabolism. DREF treatment led to the highest decrease in DBC concentration (38 %). DSHIP treatment, which presented a substantially different d-PAH and dissolved metals content to the other two treatments, showed the lowest decreases in DOC, DBC and d-PAH concentrations, as well as the lowest prokaryotic activity and biomasses. Our results indicate that BC-derived DOM, including the most condensed fraction of this material, is partly bioavailable and therefore likely to be assimilated by marine prokaryotes. The origin of BC/soot deposited at the ocean surface turns out to be a key parameter that dictates the efficiency of biodegradation of its dissolved fraction by heterotrophic prokaryotes