Poussart Pascale F.

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Poussart
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Pascale F.
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  • Article
    Significance of perylene for source allocation of terrigenous organic matter in aquatic sediments.
    (American Chemical Society, 2019-06-19) Hanke, Ulrich ; Lima-Braun, Ana L. ; Eglinton, Timothy I. ; Donnelly, Jeffrey P. ; Galy, Valier ; Poussart, Pascale F. ; Hughen, Konrad A. ; McNichol, Ann P. ; Xu, Li ; Reddy, Christopher M.
    Perylene is a frequently abundant, and sometimes the only polycyclic aromatic hydrocarbon (PAH) in aquatic sediments, but its origin has been subject of a longstanding debate in geochemical research and pollutant forensics because its historical record differs markedly from typical anthropogenic PAHs. Here we investigate whether perylene serves as a source-specific molecular marker of fungal activity in forest soils. We use a well-characterized sedimentary record (1735 to 1999) from the anoxic-bottom waters of the Pettaquamscutt River basin, RI, USA to examine mass accumulation rates and isotope records of perylene, and compare them with total organic carbon and the anthropogenic PAH fluoranthene. We support our arguments with radiocarbon (14C) data of higher plant leaf-wax n-alkanoic acids. Isotope-mass balance calculations of perylene and n-alkanoic acids indicate that ~40 % of sedimentary organic matter is of terrestrial origin. Further, both terrestrial markers are pre-aged on millennial time-scales prior to burial in sediments and insensitive to elevated 14C concentrations following nuclear weapons testing in the mid-20th Century. Instead, changes coincide with enhanced erosional flux during urban sprawl. These findings suggest that perylene is definitely a product of soil derived fungi, and a powerful chemical tracer to study spatial and temporal connectivity between terrestrial and aquatic environments.
  • Preprint
    Seasonally resolved stable isotope chronologies from northern Thailand deciduous trees
    ( 2005-05-04) Poussart, Pascale F. ; Schrag, Daniel P.
    Despite the existence of a number of climate proxies, the terrestrial expression of tropical climate variability over the past few centuries remains poorly resolved. We explore the applicability of stable isotope dendroclimatology as a tool for chronology and paleo-hydrology reconstruction on deciduous trees from monsoonal northern Thailand. Analysis of 11 trees coming from 4 different regions of northern Thailand yielded 7 records with varying degrees of δ18O and δ13C seasonality. We develop age models for trees lacking visible rings based on the seasonality of the δ18O and find agreement to within ≤ 3 years with radiocarbon age estimates. We use the isotopic age models to reconstruct estimates of growth rates and find a significant positive correlation between growth and amplitude of the oxygen and carbon seasonal isotopic signals. A comparison of a reconstructed dendro-isotopic index from Pangmapa with regional rainfall records indicates significant correlations consistent with the locally derived patterns but with decreased representation of the variance. Individual isotopic chronologies stemming from different tree species share common trends, which are also consistent with patterns of rainfall variability. We see an increase in the amplitude of the seasonal δ18O cycle along with an increase in δ18Omax over the past few decades suggesting a tracking of the recent drying trend of Thailand's monsoon.