Humic acids extracted from compost as amendments for Fenton treatment of diesel-contaminated soil

In this study, we investigate the performance of a Fenton-like process carried out adding as amendments humic acids extracted from compost obtained from or     

Niche separation in two species of hare. Metabolic costs of plant phenolics

Summary The distributions of mountain hare (Lepus timidus) and European hare (L. europaeus) overlap in central Sweden, but they occupy separate food niches in winter. In Scandinavia, the European hare is mainly a grazer while mountain hare is a predominant browser. Browse contain high amounts of secondary metabolites, such as phenols, compared to grass. This raises the question if the two hare species differ in their metabolic tolerance of plant phenols and that these differences influence their food choice.Phenolic excretion in urine increased significantly with phenolic intake in both species. Excretion of glucuronic acid conjugates, one of the major pathways of elimination of phenols in both hare species, is positively correlated to phenolic intake and excretion. However, the extent of excretion of phenolics by this route was different in the two species of hare. European hares excreted substantially more glucuronic acid per amount of phenolics than mountain hare. The phenols were metabolized to a larger extent in the mountain hare, indicating a higher detoxification capacity. From these results it is likely that European hare have a higher cost for the detoxification of plant phenols compared to mountain hare. This cost and negative effect on sodium balance when feeding on browse may prevent exploitation of forest habitats by European hares, whereas mountain hare are better able to do so.     

Heavy metal accumulation and metallothionein concentration in the frog Rana ridibunda after exposure to chromium or a mixture of chromium and cadmium

The accumulation of two heavy metals (chromium (Cr) and cadmium (Cd)) in the liver, kidney and gut of Rana ridibunda exposed to Cr or to a mixture of Cr and Cd was investigated. The concentration of metallothioneins (MTs) in the same tissues was also studied. Both metals accumulated mainly in the kidney. Cr accumulation in the liver and gut was not affected by the presence of Cd. Furthermore, Cr concentration in the kidney was doubled when Cd was present. MT concentration did not increase after Cr treatment but it increased two- to six-fold over control values in mixture-exposed frogs, the highest value being observed in the gut. MTs in the gut could act as a barrier preventing ingested heavy metals from entering the blood stream. MT concentration correlated positively with Cd concentrations in both the liver and the gut of mixture-exposed animals.     

Modeling of vapor intrusion from hydrocarbon-contaminated sources accounting for aerobic and anaerobic biodegradation

A one-dimensional steady state vapor intrusion model including both anaerobic and oxygen-limited aerobic biodegradation was developed. The aerobic and anaerobic layer thickness are calculated by stoichiometrically coupling the reactive transport of vapors with oxygen transport and consumption. The model accounts for the different oxygen demand in the subsurface required to sustain the aerobic biodegradation of the compound(s) of concern and for the baseline soil oxygen respiration. In the case of anaerobic reaction under methanogenic conditions, the model accounts for the generation of methane which leads to a further oxygen demand, due to methane oxidation, in the aerobic zone. The model was solved analytically and applied, using representative parameter ranges and values, to identify under which site conditions the attenuation of hydrocarbons migrating into indoor environments is likely to be significant. Simulations were performed assuming a soil contaminated by toluene only, by a BTEX mixture, by Fresh Gasoline and by Weathered Gasoline. The obtained results have shown that for several site conditions oxygen concentration below the building is sufficient to sustain aerobic biodegradation. For these scenarios the aerobic biodegradation is the primary mechanism of attenuation, i.e. anaerobic contribution is negligible and a model accounting just for aerobic biodegradation can be used. On the contrary, in all cases where oxygen is not sufficient to sustain aerobic biodegradation alone (e.g. highly contaminated sources), anaerobic biodegradation can significantly contribute to the overall attenuation depending on the site specific conditions.