E. Parlanti

Dissolved organic matter fluorescence spectroscopy as a tool to estimate biological activity in a coastal zone submitted to anthropogenic inputs

Abstract Here we report on an investigation of the three-dimensional excitation-emission-matrix (EEM) fluorescence spectra of unconcentrated water samples collected in 1996, 1998 and 1999 at a site particularly propitious for macro-algae development. The degradation of these macro-algae was studied to determine the influence of their exudates on natural water EEM fluorescence spectra. This work demonstrates that biological activity is one of the major factors involved in the formation of the blue-shifted fluorescence band observed in marine waters (β component Ex / Em =310–320 nm/380–410 nm); our study also shows that fluorescence can be used to evaluate the biological activity both quantitatively and to determine its different phases.

Combined 3D-spectrofluorometry, high performance liquid chromatography and capillary electrophoresis for the characterization of dissolved organic matter in natural waters

3D-spectrofluorometry, high performance liquid chromatography (HPLC) and capillary electrophoresis (CE) were used to differentiate between marine and fresh water samples. These three techniques were used to obtain different patterns for marine and fresh waters, thus confirming that the organic materials they contain are different. The HPLC fractionation allowed the separation of different classes of dissolved organic matter (DOM) components. Their further analyses using both 3D spectrofluorometry and CE demonstrated that the isolated fractions were specific of the water origin. Furthermore, capillary electrophoresis was shown to have a considerable potential for fingerprinting and for a better characterisation of DOM of different origins.

Alkylated phenanthrene distribution in artificially matured kerogens from Kimmeridge clay and the Brent Formation (North Sea)

Abstract Kerogen and extractible organic matter from immature Kimmeridge clay and Brent coal were heated at different temperatures (270–500°C) under conditions to mimic natural maturation. Aromatic fractions have been examined for their phenanthrene compound distribution. Phenanthrene indices based on methylphenanthrenes (MP) and dimethylphenanthrenes (DMP) exhibit very sensible changes in the applied temperature range. However, at high temperatures (about 450°C and more) possible thermal degradation of phenanthrene compounds produces a decrease in the values of the indices. Experimental data obtained in this study are compared and discussed with data obtained on thermal evolution performed on total rocks. Vitrinite reflectance values measured on artificially matured coals are also tentatively correlated with phenanthrene ratios. Theoretical thermodynamic calculations on MP compounds confirm also the relative thermal stability of the individual isomers.

3D-fluorescence spectroscopic analysis of HPLC fractionated estuarine fulvic and humic acids

Seis amostras de acidos fulvicos (AF) e humicos (AH) estuarinos foram fracionadas por meio de cromatografia liquida de alta performance em fase reversa, num gradiente de polaridade agua → acetonitrila, com deteccao por fluorescencia. Diferencas entre os cromatogramas mostraram que os AH contem mais componentes hidrofobicos que os AF. Os espectros de fluorescencia tridimensional das fracoes foram bastante similares entre si e tambem ao da amostra original, indicando que, apesar das polaridades distintas, a complexidade e as principais caracteristicas do material original se mantem. Um mesmo grupo de fluoroforos parece ser responsavel pelas caracteristicas de fluorescencia, dos dois tipos de substâncias humicas. Um deslocamento batocromico dos espectros de emissao das solucoes originais, com relacao aqueles das fracoes, foi atribuido a uma maior proximidade destes fluoroforos, possivelmente devido a formacao de agregados. Em geral, os resultados confirmam o conceito de que as “macromoleculas” humicas consistem de associacoes de estruturas menores com caracteristicas quimicas semelhantes. Six estuarine fulvic (FA) and humic acids (HA) were fractionated with reversed-phase high performance liquid chromatography in a water/acetonitrile gradient, with fluorescence detection. Differences between FA and HA chromatograms pointed to a higher incidence of hydrophobic components in the latter. Excitation-emission matrix fluorescence diagrams of most fractions were similar to those of the bulk samples indicating that, in spite of their distinct polarities, the complexity and main spectral characteristics of the materials persisted. A primary group of fluorophores, which are present in most of the fractions, seems to be at the origin of the fluorescence properties of both kinds of HS. A bathochromic shift of the bulk solutions spectra in relation to the fraction emissions was attributed to a greater proximity of these fluorophores, possibly due to the formation of aggregates. Generally, the results reinforced concepts that humic macromolecules consist of assemblages of structurally similar building blocks.

Copper addition by organic matter degradation in the freshwater reaches of a turbid estuary

This study reports on the relationship between copper (Cu) behavior and organic matter (OM) transformation along the turbidity gradient in the freshwater reaches of the Gironde Estuary. During a one-year survey, surface water and suspended particulate matter (SPM) were sampled at least monthly at three sites along the Garonne Branch, representing the main fluvial branch of the Gironde Estuary. Additionally, a longitudinal high resolution profile was sampled along the Garonne Branch, covering the turbidity gradient from the river water endmember to the maximum turbidity zone (MTZ). Seasonal variability and spatial distribution of Cu in both the dissolved phases (<0.2 μm, Cu(0.2) and <0.02 μm, Cu(0.02)) and particulate Cu (Cu(P)) clearly suggested Cu(0.2) addition during summer, that increased the Cu(0.2) concentrations by a factor ~2, mainly manifested by an increase in the Cu(0.02) fraction. At the annual timescale (2004), this internal Cu reactivity increased Cu(0.02) fluxes in the Garonne Branch by ~20% (3.6 t year(-1)), with the equivalent of ~2.9 t year(-1) derived from the Cu(P) fraction and ~0.7 t year(-1) from the colloidal (0.02-0.2 μm) fraction, without involving and/or affecting the Cu(C18) (hydrophobic metal-organic complexes) fraction. Combining data on Cu speciation with the results obtained by several independent techniques (DOC and POC measurements, 3D-fluorescence, and TEM) suggested close relationships between Cu behavior and OM transformation/restructuration along the turbidity gradient in the Garonne Branch. The observed Cu(0.02) addition was related to increasing humification (humification index HIX increased from 9 to 12, network formation) and labile OM degradation (Iγ/Iα ratio decreased from 0.70 to 0.44), going along with decreasing DOC and POC concentrations. Mass-balances suggest that in the studied system, degradation of OM may account for the release of ~25 μmol potentially bioaccessible Cu(0.02) per mole of particulate organic carbon mineralized.

Distribution of methylperylene isomers in selected sediments

Surface and deep sediment extracts, containing perylene compounds, have been examined by High Resolution Shpolskii Spectroscopy. The first identification of the three methylperylene isomers is reported and indicates the predominance of 2-methylperylene among the methylperylene isomer distributions at any maturation stage. Perylene itself was nevertheless always found to be the most abundant perylene compound.

Development of solid-phase microextraction to study dissolved organic matter—Polycyclic aromatic hydrocarbon interactions in aquatic environment

Solid-phase microextraction coupled with gas chromatography and mass spectrometry (SPME-GC-MS) was developed for the study of interactions between polycyclic aromatic hydrocarbons (PAHs) and dissolved organic matter (DOM). After the determination of the best conditions of extraction, the tool was applied to spiked water to calculate the dissolved organic carbon water distribution coefficient (K(DOC)) in presence of different mixtures of PAHs and Aldrich humic acid. The use of deuterated naphthalene as internal standard for freely dissolved PAH quantification was shown to provide more accuracy than regular external calibration. For the first time, K(DOC) values of 18 PAHs were calculated using data from SPME-GC-MS and fluorescence quenching; they were in agreement with the results of previous studies. Competition between PAHs, deuterated PAHs and DOM was demonstrated, pointing out the non-linearity of PAH-DOM interactions and the stronger interactions of light molecular weight PAHs (higher K(DOC) values) in absence of high molecular weight PAHs.

Relationship between rank and distribution of methylaromatic hydrocarbons for condensates of different origins

Abstract Aromatic hydrocarbon fractions from thirty gas condensates have been analysed by capillary GC and high resolution Shpolskii spectroscopy for the determination of the relative distribution in methylphenanthrene (MP), dimethylphenanthrene (DMP) and methylpyrene (MPy) series. The measured maturity indices, MPI, DMPI and MPyI which appeared previously suitable for rocks, coals and crude oils have been tested for the recognition of rank levels of condensates. MPI and DMPI exhibit a remarkedly similar evolution which allows the differentiation of the samples analysed in these works. Such studies extend the applicability of alkylaromatic hydrocarbon ratios to the characterization of maturity level of condensates which range from immature-marginally mature to overmature samples, partially biodegraded or not.

Asymmetrical flow field-flow fractionation of white wine chromophoric colloidal matter

AbstractTwo analytical separation methods—size-exclusion chromatography and asymmetrical flow field-flow fractionation—were implemented to evaluate the integrity of the colloidal composition of Chardonnay white wine and the impact of pressing and fermentations on the final macromolecular composition. Wine chromophoric colloidal matter, representing UV–visible-absorbing wine macromolecules, was evaluated by optical and structural measurements combined with the description of elution profiles obtained by both separative techniques. The objective of this study was to apply these two types of fractionation on a typical Chardonnay white wine produced in Burgundy and to evaluate how each of them impacted the determination of the macromolecular chromophoric content of wine. UV–visible and fluorescence measurements of collected fractions were successfully applied. An additional proteomic study revealed that grape and microorganism proteins largely impacted the composition of chromophoric colloidal matter of Chardonnay wines. Asymmetrical flow field-flow fractionation appeared to be more reliable and less invasive with respect to the native chemical environment of chromophoric wine macromolecules, and hence is recommended as a tool to fractionate chromophoric colloidal matter in white wines. Graphical AbstractAn innovative macromolecular separation method based on Asymmetrical Flow Field-Flow Fractionation was developed to better control colloidal dynamics across Chardonnay white winemaking.

Study of the Optical Properties of Dissolved Organic Matter in the Seine River Catchment (France)

In this study, the optical properties of dissolved organic matter (DOM) were investigated using UV/visible photometry and excitation emission matrix (EEM) fluorescence spectroscopy. Differences in quality and quantity of organic carbon were observed and highlighted discrimination of organic matter typologies between the four studied areas in the catchment of the Seine river.