First step towards understanding the behavior of oxygenated polycyclic aromatic compounds (O-PACs) in soils and groundwater

National audienceObjectives: the aim of this study is to assess O-PAC migration in groundwater in order to know if they could form large contamination plumes in groundwater and therefore trigger a risk for sensitive targets such as drinking water wells. Innovative nature of the proposed topic: O-PAC migration in groundwater and parameters controlling their behavior in soils have never been assessed whereas it is well established in literature that these compounds are toxic, persistent and always present in soils of PAH contaminated sites. Abstract Oxygenated Polycyclic Aromatic Compounds (O-PACs) are toxic, persistent, highly leachable and often abundant at PAH contaminated sites. Furthermore, many studies have proven that O-PACs could be formed during and after the application of some remediation techniques on PAH contaminated sites1,2. However, in contrast to the 16 US EPA PAHs classified as priority pollutants and due to the lack of regulations and data regarding their behavior in soils, O-PACs are not included in health risk assessment studies and monitoring programs of PAH contaminated sites. However, these aromatic compounds could as well have an impact and contribute to the risk for human beings and the Environment. This study constitutes an important step in the process of understanding the transfer of these compounds within the soil system and in determining the related parameters that could affect their behavior. Two PAH/O-PAC couples were chosen for this study: fluorene/fluorenone (FLU/FLUone) and acenaphthene/dibenzofuran (ACE/DBFUR). These compounds were primarily selected regarding their available data, the possibility of their laboratory manipulation as well as the similarity in their molecular structures. Sorption isotherms onto a non-contaminated soil were individually determined using controlled batch experiments for all four compounds. Effects of ionic strength and liquid to solid ratio (L/S) on the sorption of FLU and FLUone were furthermore investigated through controlled batch experiments. For both O-PACs and PAHs, experimental data showed that the sorption kinetics were designated by the occurrence of two distinct phases. A fast-initial phase followed by a second much slower sorption process. Sorption equilibrium was achieved within less than 24 hours of mixing while no degradation of the studied compounds was observed. For all studied compounds and in all experimental conditions, linear sorption models best fit the isotherm data. Results revealed that ACE and DBFUR were similarly adsorbed onto the soil where the values of organic carbon-water partition coefficient (Koc) were 1184 and 1153 L/kg, respectively. In the same experimental conditions, Koc of FLU (1931 L/kg) was higher than that of FLUone (1355 L/kg), showing a smaller affinity of FLUone towards the solid phase. Furthermore, decreasing the L/S ratio from 100 L/kg to 50 and 30 L/kg, increased the sorption of FLUone onto the soil by 64 and 77% respectively, while the sorption of FLU was slightly increased by 13 and 31% respectively. Moreover, increasing the ionic strength of the aqueous phase by a factor of 6 favored 2 the sorption of FLUone by 62% while the sorption of FLU slightly decreased by 13%. These results provided meaningful first information regarding O-PAC behavior in soils: highly soluble O-PACs such as FLUone could easily migrate in groundwater, form larger contamination plumes than PAHs and reach drinking water wells. In addition, the difference in PAH and O-PAC behavior when decreasing the L/S ratio and increasing the ionic strength is a first hint that mechanisms responsible for O-PAC fate and transport in soils could be different than the ones responsible for PAH retention in soils. Further studies are in progress at different scales (lab and field scales) in order to better understand the migration potential of O-PACs

The Multi-Analytical Characterization of Calcium Oxalate Phytolith Crystals from Grapevine after Treatment with Calcination

Calcium oxalate phytoliths are one of the most prominent types of Ca speciation in the plant kingdom, and they store extensive amounts of carbon in crystalline form. Ca phytoliths were investigated in the root, trunk, and bark of Vitis vinifera Chasselas from a vineyard in Alsace, France. A multi-analytical approach was used, which included SEM coupled with EDX spectroscopy, XRD, XRF, TGA, and 13C-NMR spectroscopy. These techniques revealed that phytoliths are composed of crystalline calcium oxalate monohydrate (whewellite). The whewellite crystals exhibited mostly equant or short-prismatic habits in all of the three studied grapevine parts, but bipyramidal crystals also occurred. Raphide crystals were only observed in the root, where they were abundant. Instead of using wet chemical procedures to extract the mineral components from the organic parts of the biomass, a thermal treatment via calcination was chosen. The suitable temperature of calcination was determined through TGA experiments. The calcination of the biomass samples at 250 °C enhanced the amounts of Ca phytoliths in the residual chars. The thermal treatment, however, affected the appearance of the Ca oxalate crystals by producing surfaces that displayed macroporosity and by creating fractures. For calcination at both 300 °C and 350 °C, Ca oxalate lost a molecule of carbon monoxide to form Ca carbonate, and the modifications of the original crystal surfaces were more pronounced than those observed after thermal treatment at 250 °C

Wood washing: influence on gaseous and particulate emissions during wood combustion in a domestic pellet stove

International audienceNowadays, the use of biomass increasingly replaces the fossil fuels for the domestic heating production. In order to reduce pollutant emissions from biomass combustion, wood was washed at room temperature in order to represent natural rain leaching before burning in a recent pellet stove (2010s) of nominal output of 6.3 kW. Raw and washed woods were combusted for three different types of wood (oak, beech and fir) and the study focused on their particulate and gaseous emissions (Total Suspended Particles (TSP), Particulate Matter with diameter below 2.5 μm (PM2.5), carbon monoxide (CO), nitrogen oxides (NOx) and Total Volatile Organic Compounds (TVOC)). Polycyclic Aromatic Hydrocarbons (PAH), aldehydes and wood tracers as phenols compounds were also measured. In addition, considering the toxic equivalent factor, the human health impact of adsorbed and gaseous PAH is considerably reduced (96%) in the case of washed fir combustion. Emission factors of CO and TSP for washed wood combustion also show a decrease up to 50% depending on the type of wood used. Furthermore, phenolic compounds, Benzene, Toluene, Ethylbenzene, Xylenes and Trimethylbenzene (BTEXT) emissions can also be reduced by the washing of biomass. Washed oak combustion leads to a clear decrease by 60% of the total of BTEXT. In the case of phenols emissions, phenol shows a significant decrease by 91% during the combustion of washed fir wood

Fluorescence Microscopy Analysis of Particulate Matter from Biomass Burning: Polyaromatic Hydrocarbons as Main Contributors

<div><p>New efficient approaches to the characterization of fly ash and particulate matter (PM) have to be developed in order to better understand their impacts on environment and health. Polycyclic aromatic hydrocarbons (PAH) contained in PM from biomass burning have been identified as genotoxic and cytotoxic, and some tools already exist to quantify their contribution to PM. Optical fluorescence microscopy is proposed as a rapid and relatively economical method to allow the quantification of PAH in different particles emitted from biomass combustion. In this study samples were collected in the flue gas of biomass-combustion facilities with nominal output ranging from 40 kW to 17.3 MW. The fly ash samples were collected with various flue gas treatment devices (multicyclone, baghouse filter, electrostatic precipitator); PM samples were fractionated from the flue gas with a DEKATI® DGI impactor. A method using fluorescence observations (at 470 nm), white-light observations and image processing has been developed with the aim of quantifying fluorescence per sample. Organic components of PM and fly ash, such as PAH, humic-like substances (HULIS) and water-soluble organic carbon (WSOC) were also quantified. Fluorescence microscopy analysis method assessment was first realized with fly ash that was artificially coated with PAH and HULIS. Total amounts of PAH in the three size fractions of actual PM from biomass burning strongly correlated with the intensities of fluorescence. These encouraging results contribute to the development of a faster and cheaper method of quantifying particle-bound PAH.</p><p>Copyright 2015 American Association for Aerosol Research</p></div