Cycle du phosphore | EPFL Graph Search

Le cycle du phosphore est un cycle biogéochimique mettant en jeu le phosphore. Le phosphore est un constituant indispensable de la matière organique, même si son importance pondérale est relativement faible par rapport à l'azote ou au potassium. Son rôle est lié au stockage et transfert d'énergie (ATP), et à la formation de nombreux composés structurels (acides nucléiques, nucléotides, phospholipides, coenzymes,…). Le phosphate est un élément limitant de nombreux écosystèmes terrestres, faute de réservoir atmosphérique; car sa disponibilité est directement liée à l’altération superficielle des roches. Le cycle du phosphore est unique parmi les cycles biogéochimiques majeurs, car il ne possède pas de composante gazeuse ; il n’affecte pratiquement pas l'atmosphère. De plus, l’effet limitant du phosphore est perturbé par des apports anthropiques, ce qui peut causer des problèmes environnementaux d’eutrophisation. Les humains ont provoqué des changements majeurs au cycle mondial du phos

Towards an improved understanding of biogeochemical processes across surface-groundwater interactions in intermittent rivers and ephemeral streams

Luis Gómez Gener, Oleksandra Shumilova

Surface-groundwater interactions in intermittent rivers and ephemeral streams (IRES), waterways which do not flow year-round, are spatially and temporally dynamic because of alternations between flowing, non-flowing and dry hydrological states. Interactions between surface and groundwater often create mixing zones with distinct redox gradients, potentially driving high rates of carbon and nutrient cycling. Yet a complete understanding of how underlying biogeochemical processes across surface-groundwater flowpaths in IRES differ among various hydrological states remains elusive. Here, we present a conceptual framework relating spatial and temporal hydrological variability in surface water-groundwater interactions to biogeochemical processing hotspots in IRES. We combine a review of theIRES biogeochemistry literature with concepts of IRES hydrogeomorphology to: (i) outline common distinctions among hydrological states in IRES; (ii) use these distinctions, together with considerations of carbon, nitrogen, and phosphorus cycles within IRES, to predict the relative potential for biogeochemical processing across different reach-scale processing zones (flowing water, fragmented pools, hyporheic zones, groundwater, and emerged sediments); and (iii) explore the potential spatial and temporal variability of carbon and nutrient biogeochemical processing across entire IRES networks. Our approach estimates the greatest reach-scale potential for biogeochemical processing when IRES reaches are fragmented into isolated surface water pools, and highlights the potential of relatively understudied processing zones, such as emerged sediments. Furthermore, biogeochemical processing in fluvial networks dominated by IRES is likely more temporally than spatially variable. We conclude that biogeochemical research in IRES would benefit from focusing on interactions between different nutrient cycles, surface-groundwater interactions in non-flowing states, and consideration of fluvial network architecture. Our conceptual framework outlines opportunities to advance studies and expand understanding of biogeochemistry in IRES.

2021

Water soluble reactive phosphate (SRP) in atmospheric particles over East Mediterranean: The importance of dust and biomass burning events

Athanasios Nenes, Christos Panagiotopoulos, Kalliopi Violaki

The importance of dust and biomass burning episodes on the atmospheric concentration of water-soluble reactive phosphate (SRP) was determined in the eastern Mediterranean. SRP was measured with a new rapid real-time automated analytical system with a time resolution of a few minutes per sample and with an extremely low detection limit. The average atmospheric concentration of SRP during the sampling campaign was estimated at 0.35 & nbsp;+/- 0.25 (median 0.30) nmol P m(-3). The maximum concentration of SRP (3.08 nmol P m(-3)) was recorded during an intense dust episode, and was almost ten times higher than the campaign average, confirming that Saharan dust was an important primary source of bioavailable P to the eastern Mediterranean, especially during the spring period when 60% of the events occurred. Predicted increases in the frequency and intensity of dust storms in the area will enhance the role of the atmosphere as a source of bioavailable P for the Mediterranean marine ecosystem. During the warm period, when Northerly winds prevailed, biomass burning processes contributed significantly to soluble phosphorus delivered from atmospheric sources to the eastern Mediterranean. These inputs during warm periods are especially important for the Eastern Mediterranean, where biological productivity is strongly limited by nutrient availability.

ELSEVIER2022

The role of Organophosphate Esters Flame Retardants and plasticizers (OPEs) in Phosphorus Cycle in the atmosphere of the Mediterranean Sea

Athanasios Nenes, Christos Panagiotopoulos, Kalliopi Violaki

The atmosphere is considered as an important external nutrient source for the marine environment, especially in remote ocean waters or the oligotrophic Mediterranean Sea. Phosphorus (P) is a critical nutrient affecting primary productivity in large areas of oceanic ecosystems. Much has been placed on inorganic P, while the importance of organic P as potential pool of bioavailable P is not widely recognized. In this study we quantify and speciate the anthropogenic organic P in the West and East Mediterranean atmosphere. Several anthropogenic organophosphorus compounds are analyzed, including pesticides (Phosmet, Malathion, Ethoprophos, Diazinon, Chloropyrifos-Me, Chloropyrifos-e), organophosphorus flame retardants and plasticizers (OPEs) (Tris- (1-chloro-2-propyl) phosphate (TCPP), tris[2-chloro-1-(chloromethyl)ethyl]phosphate (TDCP), Tris-(2-chloroethyl)phosphate (TCEP), tri-n-butyl phosphate (TnBP), triphenyl phosphate (TPhP), 2-ethylhexyl diphenyl phosphate (EHDPP)). Our analysis applied to Total Suspended atmospheric Particles (TSP) collected in Eastern (Crete, n = 67) and Western (Marseille, n = 25) Mediterranean Sea by using high-volume air sampler. The analysis performed with the liquid chromatography coupled to mass spectrometry (Q–TOF–LC/MS) after optimization of the analytical protocol for the aerosol samples. Five pesticides were found during the sampling period in East Mediterranean in total of 27 samples. The most frequent were chlorpyrifos–e (n = 9) and phosmet (n = 10) with average concentration 0.24±0.38 pmol m–3 and 0.24±0.45 pmol m–3, respectively following by diazinon (n = 4) at 0.07±0.00 pmol m–3. Higher concentration was estimated in chlorpyrifos-me at 0.91±0.93 pmol m–3 (n = 3) while ethoprophos was detected only in one sample (0.002 pmol m m–3), malathion was below detection limit. In the West Mediterranean, the most abundant organophosphate pesticides were phosmet (n = 3) with an average concentration of 0.07±0.04 pmol m–3, followed by diazinon (0.05 pmol m–3, n = 1) and chloropyrifos-e (0.04 pmol m–3, n = 2). Malathion, chlorpyrifos-me and ethoprophos were not detected. The average contribution of organophosphate pesticides in atmospheric organic P detected during this study was 0.2% and 0.1% for East and West Mediterranean, respectively. OPEs analyses in the same samples revealed higher concentrations in the West than in East Mediterranean atmosphere especially for TCPP, TCEP and TDCP, which are considered as the most potentially hazardous. In the West Med. the most abundant detected OPEs were the EHDPP (3.04±4.17 pmol m-3) and the TCPP (1.71±1.28 pmol m-3). In East Mediterranean, the most abundant detected OPEs were the TCPP (0.36±0.29 pmol m-3) and the TCEP (0.24±0.20 pmol m-3) whereas the TDCP and the EHDPP were not detected. The percentage contribution of OPEs in atmospheric organic–P over the West Mediterranean was 9%, while over East was 0.4%. The total anthropogenic organic P deposited in East Mediterranean during stratification period (June-September) was calculated at 8 tons, which was 4 times lower comparing with West Mediterranean (29 tons of P) during the same period. Overall, the above anthropogenic compounds represented only 0.4% of the total anthropogenic P deposited during stratification period, however their toxicity and fate to the marine environment warrants further investigations.

2020

Towards an improved understanding of biogeochemical processes across surface-groundwater interactions in intermittent rivers and ephemeral streams

Luis Gómez Gener, Oleksandra Shumilova

2021

The role of Organophosphate Esters Flame Retardants and plasticizers (OPEs) in Phosphorus Cycle in the atmosphere of the Mediterranean Sea

Athanasios Nenes, Christos Panagiotopoulos, Kalliopi Violaki

2020