Bertrand Ligouis

Influence of Coal-Tar Sealcoat and Other Carbonaceous Materials on Polycyclic Aromatic Hydrocarbon Loading in an Urban Watershed

Carbonaceous material (CM) particles are the principal vectors transporting polycyclic aromatic hydrocarbons (PAHs) into urban waters via runoff; however, characteristics of CM particles in urban watersheds and their relative contributions to PAH contamination remain unclear. Our objectives were to identify the sources and distribution of CM particles in an urban watershed and to determine the types of CMs that were the dominant sources of PAHs in the lake and stream sediments. Samples of soils, parking lot and street dust, and streambed and lake sediment were collected from the Lake Como watershed in Fort Worth, Texas. Characteristics of CM particles determined by organic petrography and a significant correlation between PAH concentrations and organic carbon in coal tar, asphalt, and soot indicate that these three CM particle types are the major sources and carriers of PAHs in the watershed. Estimates of the distribution of PAHs in CM particles indicate that coal-tar pitch, used in some pavement sealcoats, is a dominant source of PAHs in the watershed, and contributes as much as 99% of the PAHs in sealed parking lot dust, 92% in unsealed parking lot dust, 88% in commercial area soil, 71% in streambed sediment, and 84% in surficial lake sediment.

Identification of carbonaceous geosorbents for PAHs by organic petrography in river floodplain soils

Organic petrographic analysis was applied to provide direct information on carbonaceous geosorbents for PAHs in river floodplain soils. The anthropogenic OM group (primarily coal and coal-derived particles) displayed large volume amounts for all the soil samples. Distinct PAH concentrations with similar PAH distribution patterns were determined in grain size and density fractions for each sample. Two-ring PAHs had stronger correlation to organic carbon (OC) than black carbon (BC) contents, while heavier PAHs showed correlation to BC, rather than OC. In this study, we combined grain size and density separation, PAH determinations, TOC and BC measurements, and organic petrographic identification, and concluded that two-ring PAHs in soils were associated to coal particles. Other heavier PAHs could be more controlled by black carbon (BC), which were mostly coal-derived particles from former coal mining and coal industrial activity.

On the evidence for human use and control of fire at Schöningen

When and how humans began to control fire has been a central debate in Paleolithic archaeology for decades. Fire plays an important role in technology, social organization, subsistence, and manipulation of the environment and is widely seen as a necessary adaptation for the colonization of northern latitudes. Many researchers view purported hearths, burnt wooden implements, and heated flints from Schöningen as providing the best evidence for the control of fire in the Lower Paleolithic of Northern Europe. Here we present results of a multianalytical study of the purported hearths along with a critical examination of other possible evidence of human use or control of fire at Schöningen. We conclude that the analyzed features and artifacts present no convincing evidence for human use or control of fire. Our study also shows that a multianalytical, micro-contextual approach is the best methodology for evaluating claims of early evidence of human-controlled fire. We advise caution with macroscopic, qualitative identification of combustion features, burnt flint, and burnt wood without the application of such techniques as micromorphology, Fourier transform infrared (FTIR) spectroscopy, organic petrology, luminescence, and analysis of mineral magnetic parameters. The lack of evidence for the human control of fire at Schöningen raises the possibility that fire control was not a necessary adaptation for the human settlement of northern latitudes in the Lower Paleolithic.

Accumulation of polycyclic aromatic hydrocarbons in rural soils based on mass balances at the catchment scale.

Polycyclic aromatic hydrocarbons (PAHs) are hydrophobic organic pollutants that are ubiquitously distributed in the environment at relatively high concentrations. In our study we investigated the long-term fate of atmospheric PAHs in soils of rural areas, resulting from diffuse pollution based on mass balances at the catchment scale. By determining PAHs in several environmental compartments, estimates of soil storages and water fluxes were made and compared with atmospheric deposition. The results indicate that more than 90% of the incoming PAHs remain in the catchments and accumulate in the topsoils. Furthermore, revolatilization of PAHs from soils and degradation in the soils is very limited, resulting in ongoing accumulation in topsoils, in particular for low-volatile PAHs. Combustion-derived carbonaceous particles were detected in atmospheric deposition as well as in the soil samples. Since these particles are very strong adsorbents, they are suspected to play a key role in the environmental fate of the diffuse distributed PAHs.

The depositional environments of Schöningen 13 II-4 and their archaeological implications

Geoarchaeological research at the Middle Pleistocene site of Schöningen 13 II-4, often referred to as the Speerhorizont, has focused on describing and evaluating the depositional contexts of the well-known wooden spears, butchered horses, and stone tools. These finds were recovered from the transitional contact between a lacustrine marl and an overlying organic mud, originally thought to be a peat that accumulated in place under variable moisture conditions. The original excavators proposed that hominin activity, including hunting and butchery, occurred on a dry lake shore and was followed by a rapid sedimentation of organic deposits that embedded and preserved the artifacts. Our geoarchaeological analysis challenges this model. Here, we present evidence that the sediments of Schöningen 13 II-4 were deposited in a constantly submerged area of a paleolake. Although we cannot exclude the possibility that the artifacts were deposited during a short, extreme drying event, there are no sedimentary features indicative of surface exposure in the sediments. Accordingly, this paper explores three main alternative models of site formation: anthropogenic disposal of materials into the lake, a geological relocation of the artifacts, and hunting or caching on lake-ice. These models have different behavioral ramifications concerning hominin knowledge and exploitation of the landscape and their subsistence strategies.

Phenanthrene sorption with heterogeneous organic matter in a landfill aquifer material

Abstract Phenanthrene was used as a model chemical to study the sorption properties of Canadian River Alluvium aquifer material. Both equilibrium and kinetic sorption processes were evaluated through batch studies. The bulk sample was divided into subsamples with varying properties such as particle size, organic content, equilibration time, etc. in order to determine the effect of these properties on resulting sorption parameters. The data have been interpreted and the effect of experimental variables was quantified using the Freundlich isotherm model and a numerical solution of Ficks 2nd law in porous media. Microscopic organic matter characterization proved to be a valuable tool for explaining the results. Different organic matter properties and sorption mechanisms were observed for each soil subsample. Samples containing coal particles presented high Koc values. Samples with organic matter dominated by organic coatings on quartz grains presented low Koc values and contained a high percentage of fast sorption sites. The numerical solution of Ficks 2nd law requires the addition of two terms (fast and slow) in order to fit the kinetics of these heterogeneous samples properly. These results thus demonstrate the need for soil organic matter characterization in order to predict and explain the sorption properties of a soil sample containing heterogeneous organic matter and also the difficulty and complexity of modeling sorption in such samples.

Airborne contaminants in the refractory organic carbon fraction of arable soils in highly industrialized areas

Airborne carbonaceous particles produced by industrial activity have been recorded in soils in proximity to contamination sources that produce coal dust, coke and other residues from fossil fuel combustion. The present study assesses the contribution of airborne contaminants to the refractory organic carbon pool of three soils (a sandy Albic Luvisol, sandy Orthic Luvisol and a loamy Haplic Chernozem) in C-depleted and conventionally managed plots from European long-term experiments located in industrialized regions. The C-depleted plots (unmanured plots and bare fallow) are depleted in labile C and thus relatively enriched in refractory C as compared with the conventionally managed plots. Bulk soils and particle-size fraction were analyzed for soil organic carbon (SOC) structure by cross-polarization magic-angle spinning (CPMAS) 13C nuclear magnetic resonance (NMR) spectroscopy. Coarse-intermediate separates were subjected to a morphological characterization of organic matter (OM) composition by coal petrography. The C-depleted plots show unusually high proportions of aromatic C in nearly all separates, most pronounced in coarse-intermediate fractions. Coal petrographic analysis indicates that high aromaticity in separates 2000–20 μm can be explained by the presence of air-borne contaminants that are identified as coal, coke and combustion residues from fossil fuels. For the two sandy sites, aromatic C in the fine separates (<6 μm) is dominated by protonated aryl C as revealed by dipolar dephasing (DD) NMR experiments. For the loamy soil, aromatic C was comparatively high and about half of the aryl signal was attributable to non-protonated/C-substituted carbons. These results indicate a contribution of airborne contaminants to the refractory C pool for all investigated sites. For the two sandy soils, this contribution appears to be limited to coarse-intermediate separates; in the loamy soil, a contamination is also present in fine separates. From the OC balance of the C-depleted plots, it was estimated that the contribution from contaminants to the refractory C pool is still smaller than that from native OM, which is found mainly within fine particle-size separates. The presence of refractory contaminants will strongly affect the estimation of the long-term turnover of OC at such long-term experiments. A careful examination of the SOM composition and the SOM fractions at such sites is necessary to avoid biased results on SOM turnover.

Organic Petrology: A New Tool to Study Contaminants in Soils and Sediments

The contamination of soils and sediments by carbonaceous particles has been investigated by organic-petrological methods. Results from the study of soils from industrialised areas show that airborne contaminants like brown coal, hard coal, charcoal, and char have accumulated. The observed soil contamination is due to dust emission by open-cast brown coal mines, to the burning of brown coal and hard coal, and coking plants. It was found that soil contamination can occur over a distance of several dozen km from the contamination sources. The investigation of soils and sediments demonstrates the heterogeneous character of organic matter and proves the presence of coal and charcoal particles of fossil origin in the majority of the samples. The heterogeneity of the organic matter is found responsible for variations in the sorption behaviour of organic pollutants like polycyclic aromatic hydrocarbons in soils and sediments.

Enhanced sorption of PAHs in natural-fire-impacted sediments from Oriole Lake, California.

Surface sediment cores from Oriole Lake (CA) were analyzed for organic carbon (OC), black carbon (BC), and their δ(13)C isotope ratios. Sediments displayed high OC (20-25%) and increasing BC concentrations from ∼0.40% (in 1800 C.E.) to ∼0.60% dry weight (in 2000 C.E.). Petrographic analysis confirmed the presence of fire-derived carbonaceous particles/BC at ∼2% of total OC. Natural fires were the most likely cause of both elevated polycyclic aromatic hydrocarbon (PAH) concentrations and enhanced sorption in Oriole Lake sediments prior to 1850, consistent with their tree-ring-based fire history. In contrast to other PAHs, retene and perylene displayed decreasing concentrations during periods with natural fires, questioning their use as fire tracers. The occurrence of natural fires, however, did not result in elevated concentrations of black carbon or chars in the sediments. Only the 1912-2007 sediment layer contained anthropogenic particles, such as soot BC. In this layer, combining OC absorption with adsorption to soot BC (using a Freundlich coefficient n = 0.7) explained the observed sorption well. In the older layers, n needed to be 0.3 and 0.5 to explain the enhanced sorption to the sediments, indicating the importance of natural chars/inertinites in sorbing PAHs. For phenanthrene, values of n differed significantly between sorption to natural chars (0.1-0.4) and sorption to anthropogenic black carbon (>0.5), suggesting it could serve as an in situ probe of sorbents.

Ivory or bone? A report on practical experience determining material from the Mesolithic site Klein Breese (Northern Germany)

As recent studies have provided the first proof of the secondary use of fossil ivory in Northern Germany during the Late Palaeolithic (Gramsch et al. J Archaeol Sci 40:2458–2463, 2013), a number of compact biological fragments excavated from a Mesolithic site were studied to identify the material and the species from which they derived, with a special focus on possibly identifying ivory. Detailed analysis of the sample surfaces by optical microscopy and SEM showed alteration due to weathering and thereby made detailed morphological studies without further preparation difficult. Subsequent chemical analyses were based on the most common method, Raman spectroscopy, and the measurement of the δ13C value; they did not contradict the hypothesis of ivory as the raw material. However, the results were not able to provide a positive identification of the material; hence, histological studies were performed using thin sections and micro-X-ray tomography. The result clearly provided evidence that the fragments were derived from cortical bone and not from ivory. By presenting our experiences and difficulties in the interpretation of the results, we hope to provide help for archaeological researchers in choosing the most suitable methods in comparable future studies.