Microbial and chemical markers: runoff transfer in animal manure-amended soils

Fecal contamination of water resources is evaluated by the enumeration of the fecal coliforms and Enterococci. However, the enumeration of these indicators does not allow us to differentiate between the sources of fecal contamination. Therefore, it is important to use alternative indicators of fecal contamination to identify livestock contamination in surface waters. The concentration of fecal indicators (, enteroccoci, and F-specific bacteriophages), microbiological markers (Rum-2-bac, Pig-2-bac, and ), and chemical fingerprints (sterols and stanols and other chemical compounds analyzed by 3D-fluorescence excitation-matrix spectroscopy) were determined in runoff waters generated by an artificial rainfall simulator. Three replicate plot experiments were conducted with swine slurry and cattle manure at agronomic nitrogen application rates. Low amounts of bacterial indicators (1.9-4.7%) are released in runoff water from swine-slurry-amended soils, whereas greater amounts (1.1-28.3%) of these indicators are released in runoff water from cattle-manure-amended soils. Microbial and chemical markers from animal manure were transferred to runoff water, allowing discrimination between swine and cattle fecal contamination in the environment via runoff after manure spreading. Host-specific bacterial and chemical markers were quantified for the first time in runoff waters samples after the experimental spreading of swine slurry or cattle manure.     

Modelling of paralytic shellfish toxin biotransformations in the course of Crassostrea gigas detoxification kinetics

The aim of this study was to evaluate the importance of biotransformation of paralytic shellfish toxins during the detoxification process in contaminated oysters. Mathematical models based upon the detoxification patterns of digestive gland and other tissues were developed. It was demonstrated that biotransformations do not seem to play an important role in digestive gland or other tissue detoxification kinetics with our data set. Moreover, different toxin transfers from digestive gland toward other tissues were investigated. No significant transfer was highlighted in our data set. These first conclusions were drawn after comparing the results obtained from 13 biotransformations and identifiable transfer scenarios. Finally, to determine a more robust model, all 12 states corresponding to toxic compounds and tissues were aggregated into a single state model. The best adjustment was obtained with a simple one-compartment model based on total flesh toxicity with elimination rate expressed by a function depending on initial concentrations of GTX3 and GTX2 (i.e. the two major toxic compounds found in contaminated oysters).     

Degradation of the fungicide difenoconazole in a silt loam soil as affected by pretreatment and organic amendment

Degradation of the fungicide difenoconazole was examined in a silt loam soil under controlled conditions (60% WHC, 30 degrees C) in the laboratory. Difenoconazole was applied at 0.1 and 1.0 mg kg(-1) dry soil, respectively. The experiments were run with non-pretreated and pretreated field soil, respectively, partly mixed with easily decomposable organic matter (leaf powder). In all experiments, degradation curves showed a sigmoidal shape with clear acclimation phases. Pretreatment with difenoconazole in the field decreased the acclimation phases, DT(50)- and, in some cases, DT(90)-values. The incorporation of easily decomposable organic matter decreased both DT(50)- and DT(90)-values and increased the general microbial activity significantly. We conclude that difenoconazole is metabolized by an acclimated part of the soil microflora. However, the degradation seems to be stimulated in the presence of suitable co-substrates.     

A tunable diode laser absorption spectrometer for formaldehyde atmospheric measurements validated by simulation chamber instrumentation

A tunable diode laser absorption spectrometer (TDLAS) for formaldehyde atmospheric measurements has been set up and validated through comparison experiments with a Fourier transform infrared spectrometer (FT-IR) in a simulation chamber. Formaldehyde was generated in situ in the chamber from reaction of ethene with ozone. Three HCHO ro-vibrational line intensities (at 2909.71, 2912.09 and 2914.46 cm^-1) possibly used by TDLAS were calibrated by FT-IR spectra simultaneously recorded in the 1600-3200 cm^-1 domain during ethene ozonolysis, enabling the on-line deduction of the varying concentration for HCHO in formation. The experimental line intensities values inferred confirmed the calculated ones from the updated HITRAN database. In addition, the feasibility of stratospheric in situ HCHO measurements using the 2912.09 cm^-1 line was demonstrated. The TDLAS performances were also assessed, leading to a 2σ detection limit of 88 ppt in volume mixing ratio with a response time of 60 sec at 30 Torr and 294 K for 112 m optical path. As part of this work, the room-temperature rate constant of this reaction and the HCHO formation yield were found to be in excellent agreement with the compiled literature data.