International audience | This study addressed the relative importance of particle coating, sewage sludge amendment, and aging on aggregation and dissolution of manufactured Ag nanoparticles (Ag MNPs) in soil pore water. Ag MNPs with citrate (CIT) or polyvinylpyrrolidone (PVP) coatings were incubated with soil or municipal sewage sludge which was then amended to soil (1% or 3% sludge (w/w)). Pore waters were extracted after 1 week and 2 and 6 months and analyzed for chemical speciation, aggregation state and dissolution. Ag MNP coating had profound effects on aggregation state and partitioning to pore water in the absence of sewage sludge, but pre-incubation with sewage sludge negated these effects. This suggests that Ag MNP coating does not need to be taken into account to understand fate of AgMNPs applied to soil through biosolids amendment. Aging of soil also had profound effects that depended on Ag MNP coating and sludge amendment. (C) 2013 Elsevier Ltd. All rights reserved.

This study addressed the relative importance of particle coating, sewage sludge amendment, and aging on aggregation and dissolution of manufactured Ag nanoparticles (Ag MNPs) in soil pore water. Ag MNPs with citrate (CIT) or polyvinylpyrrolidone (PVP) coatings were incubated with soil or municipal sewage sludge which was then amended to soil (1% or 3% sludge (w/w)). Pore waters were extracted after 1 week and 2 and 6 months and analyzed for chemical speciation, aggregation state and dissolution. Ag MNP coating had profound effects on aggregation state and partitioning to pore water in the absence of sewage sludge, but pre-incubation with sewage sludge negated these effects. This suggests that Ag MNP coating does not need to be taken into account to understand fate of AgMNPs applied to soil through biosolids amendment. Aging of soil also had profound effects that depended on Ag MNP coating and sludge amendment.

A chronological sequence of urban soils 3–92 years old was studied to determine the effects of time on morphogenesis, artifact weathering, and the geochemical partitioning of Pb. Key chronofunctions determined are an increase in ˆA horizon Development Index (defined herein based on soil color) and water-soluble Pb, and a decrease in pH and C/N, with increasing soil age. Key artifact weathering reactions are: 1) portlandite in mortar altered to calcite, 2) ferrite in wrought-iron altered to ferrihydrite and goethite, and 3) carbonaceous materials altered to water-soluble organic substances. Mortar and wrought-iron were found to be Pb-bearing, but weather to produce immobilizing agents. Hence, they are both a source and a sink for Pb. The origin and mobilization of water-soluble Pb is complex and probably includes microbial extracellular polymeric substances, biodegraded soil organic matter, and solubilized organic substances derived from carbonaceous anthropogenic microparticles (soot, char and coal-related wastes).

This study compares the effectiveness of two different thickness of green roof substrate with respect to nutrient and heavy metal retention and release. To understand and evaluate the long term behaviour of green roofs, substrate columns with the same structure and composition as the green roofs, were exposed in laboratory to artificial rain. The roofs act as a sink for C, N, P, zinc and copper for small rain events if the previous period was principally dry. Otherwise the roofs may behave as a source of pollutants, principally for carbon and phosphorus. Both field and column studies showed an important retention for Zn and Cu. The column showed, however, lower SS, DOC and metal concentrations in the percolate than could be observed in the field even if corrected for run-off. This is most probably due to the difference in exposition history and weathering processes.

We compare the chromatographic signatures of petroleum biomarkers in Deepwater Horizon (DH) source oil, three other reference crude oils, DH emulsified mousse that arrived on Alabama’s shoreline in June 2010, and seven tar balls collected from Alabama beaches from 2011 to 2012. Characteristic hopane and sterane fingerprints show that all the tar ball samples originated from DH oil. In addition, the diagnostic ratios of various hopanes indicate an excellent match. Quantitation data for C30αβ-hopane concentration levels show that most of the weathering observed in DH-related tar balls found on Alabama’s beaches is likely the result of natural evaporation and dissolution that occurred during transport across the Gulf of Mexico prior to beach deposition. Based on the physical and biomarker characterization data presented in this study we conclude that virtually all fragile, sticky, brownish tar balls currently found on Alabama shoreline originated from the DH oil spill.

Troll B crude oil was weathered under Arctic conditions with different ice coverage: open water, 50% ice and 90% ice. Samples (100mL) were taken during the experiment and tested for ignitability in a burning cell. From each burning a residue sample was taken for analysis. The burning process removed the light compounds eluting before C13. No effect from the prior weathering time or the different ice coverage was seen in the burn residue composition. The content of selected Poly Aromatic Hydrocarbons (PAHs) was determined and it was noted that the concentration of PAHs with more than 4 rings were increased. The source origin of the PAHs was investigated by use of relative ratios of PAH isomers and indicated that some formation of PAHs was additionally taking place during burning.

In an attempt to analyze the chemical characterization of oil residues and examine the suitability of chemical fingerprinting methods in oil spill investigations, multiple parameters sensitive to both sources and degree of weathering were used to characterize oil residues from “7–16” Dalian oil spill, China. Oil residues collected 90days to 120days after the spill showed a weathering pattern where significant amounts of light to middle molecular weight normal alkanes were depleted with pristane and phytane as dominant peaks. Diagnostic ratios developed from n-alkane and selected isoprenoids (e.g. Pr/Ph, n-C17/Pr, n-C18/Ph, carbon preference index, LMW/HMW-alkanes ratio), all display obvious changes over weathering time, indicating that these ratios are not valid for oil source identification. Furthermore, the biomarker ratios of hopanes and steranes with relative standard deviations (RSDs) of 0.88–4.08% were useful for source identification even for severely weathered oil residues. In addition, RSD of δ13C values of individual n-alkanes in oil residue varied from 0.07% to 0.20%, which suggest that stable carbon isotope profile of n-alkanes can also be a useful tool for tracing the source of an oil spill.

The toxicity of the water associated fraction (WAF) of Alaska North Slope Crude oil (ANSC), Corexit 9500A and the dispersant enhanced WAF (DEWAF) of ANSC:Corexit 9500A mixtures were examined on the model ammonia oxidizing bacterium, Nitrosomonas europaea. Corexit 9500A was not toxic at environmentally relevant concentrations. Corexit 9500A greatly increased the toxicity of ANSC by increasing the chemical oxygen demand (COD) of the DEWAF. However, a majority of the DEWAF compounds were not toxic to N. europaea. Weathered WAF and DEWAF were not toxic to N. europaea even though their COD did not change compared to non-weathered controls, suggesting that toxicity was due to a small volatile fraction of the ANSC. The over-expression of the NE1545 gene, a marker for aromatic hydrocarbon exposure, in N. europaea cells exposed to WAF and DEWAF suggests that aromatic hydrocarbons are bioavailable to the cells and may play a role in the observed toxicity.

This paper reanalyzes data from an earlier study that used effluents from oiled-gravel columns to assess the toxicity of aqueous fractions of weathered crude oil to Pacific herring embryos and larvae. This reanalysis has implications for future similar investigations, including the observance of two distinct dose–response curves for lethal and sublethal endpoints for different exposures in the same experiment, and the need to consider both potency and slope of dose–response curves for components of a toxicant mixture that shows potentially different toxicity mechanisms/causation. Contrary to conclusions of the original study, the aqueous concentration data cannot support the hypothesis that polycyclic aromatic hydrocarbons (PAHs) were the sole cause of toxicity and that oil toxicity increased with weathering. Confounding issues associated with the oiled gravel columns include changes in the concentration and composition of chemicals in exposure water, which interfere with the production of reliable and reproducible results relevant to the field.

Following the release of crude oil from the Macondo well in 2010, a wide range of weathering processes acted on the spilled oil. A recent study revealed that samples from this spill were oxidized into oxygenated hydrocarbons (OxHC) comprising more than 50% of the extracted hydrocarbons. The precursors of these compounds were not identified despite using a wide range of analytical tools, including gas chromatography (GC). To search for these precursors, over 40 samples were analyzed by comprehensive two-dimensional gas chromatography (GC×GC), one of the largest studies of its kind to date. Partial least squares regression was employed to elucidate the GC×GC peaks that could be the precursors of OxHC in our samples. We found that the formation of OxHC correlated with the disappearance of saturated hydrocarbons, including alkylcyclopentanes, alkyl cyclohexanes, alkylated bicyclic saturated compounds, tricyclic terpanpoids, and alkylbenzenes. These results indicate a previously under-reported chemodynamic process in oil spill weathering.