Semi Permeable Membrane Device Reveals indoor and outdoor contamination of Polychlorinated Biphenyls (PCBs)

Semi Permeable Membrane Device (SPMD) was deployed on an experimental basis for five days inside an Environmental Chemistry Laboratory and two sites outside the building in Kiel, Germany to understand the time-averaged contaminant profiles and concentrations of PCBs. Multi Dimensional High Resolution Gas Chromatography-Electron Capture Detection technique and high resolution clean up techniques were employed to SPMD derived triolein samples. Air concentrations were derived from well established mass transfer coefficients or rate constants for PCBs in SPMD. PCBs profiles in indoor and outdoor samples were distinctly different, exemplified by a particle free clean-up laboratory facility where particle associated higher chlorinated congeners were absent. SPMDs revealed the ‘occupational hazard’ to workers inside the building from chemical contamination derived from both building materials and chemicals used in the laboratory. Finger printing technique using principle component analysis (PCA) revealed that PCB contamination was derived from German commercial PCB mixtures. SPMD derived air concentrations in outdoor samples resembled levels recorded by similar devices in Europe. Ultimately, a simple sampling technique in combination with high resolution analytical techniques demonstrated the uptake of more than 60 PCB congeners within a short period of time

Combination of RISM and cheminformatics for efficient predictions of hydration free energy of polyfragment molecules : application to a set of organic pollutants

Here, we discuss a new method for predicting the hydration free energy (HFE) of organic pollutants and illustrate the efficiency of the method on a set of 220 chlorinated aromatic hydrocarbons. The new model is computationally inexpensive, with one HFE calculation taking less than a minute on a PC. The method is based on a combination of a molecular integral equations theory, one-dimensional reference interaction site model (1D RISM), with the cheminformatics approach. We correct HFEs obtained by the ID RISM with a set of empirical corrections. The corrections are associated with the partial molar volume and structural descriptors of the molecules. We show that the introduced corrections can significantly improve the quality of the ID RISM FIFE predictions obtained by the partial wave free energy expression [Ten-no, S. J. Chem. Phys. 2001, 115, 3724] and the Kovalenko-Hirata closure [Kovalenko, A.; Hirata, F. J. Chem. Phys. 1999, 110, 10095]. We also show that the quality of the model can be further improved by the reparametrization using QM-derived partial charges instead of the originally used OPLS-AA partial charges. The final model gives good results for polychlorinated benzenes (the mean and standard deviation of the error are 0.02 and 0.36 kcal/mol, correspondingly). At the same time, the model gives somewhat worse results for polychlorobiphenyls (PCBs) with a systematic bias of -0.72 kcal/mol but a small standard deviation equal to 0.55 kcal/mol. We note that the error remains the same for the whole set of PCBs, whereas errors of HFEs predicted with continuum solvation models (data were taken from Phillips, K L. et al. Environ. Sci. Technol. 2008, 42, 8412) increase significantly for higher chlorinated PCB congeners. In conclusion, we discuss potential future applications of the model and several avenues for its further improvement

Application of nitrogen fertilizer to a boreal pine forest has a negative impact on the respiration of ectomycorrhizal hyphae

Aims: There is evidence that increased N inputs to boreal forests, via atmospheric deposition or intentional fertilization, may impact negatively on ectomycorrhizal (ECM) fungi leading to a reduced flux of plant- derived carbon (C) back to the atmosphere via ECM. Our aim was to investigate the impact of N fertilization of a Pinus sylvestris (L.) forest stand on the return of recently photoassimilated C via the ECM component of soil respiration. Methods: We used an in situ, large-scale, 13C-CO2 isotopic pulse labelling approach and monitored the 13C label return using soil gas efflux chambersplaced over three different types of soil collar to distinguish between heterotrophic (RH), autotrophic (RA; partitioned further into contributions from ECM hyphae and total RA) and total (RS) soil respiration. Results: The impact of N fertilization was to significantly reduce RA, particularly respiration via extramatrical ECM hyphae. ECM hyphal flux in control plots showed substantial spatial variability, resulting in mean flux estimates exceeding estimates of total RA, while ECM contributions to RA in N treated plots were estimated at around 30%. Conclusion: Significant impacts on soil C cycling may be caused by reduced plant C allocation to ECM fungi in response to increased N inputs to boreal forests; ecosystem models so far lack this detail