RESUMO
The total energy dissipation rate on the ocean surface, ϵt (W m-2), provides a first-order estimation of the kinetic energy input rate at the ocean-atmosphere interface. Studies on the spatial and temporal distribution of the energy dissipation rate are important for the improvement of climate and wave models. Traditional oceanographic research normally uses remote measurements (airborne and platforms sensors) and in situ data acquisition to estimate ϵt; however, those methods cover small areas over time and are difficult to reproduce especially in the open oceans. Satellite remote sensing has proven the potential to estimate some parameters related to breaking waves on a synoptic scale, including the energy dissipation rate. In this paper, we use polarimetric Synthetic Aperture Radar (SAR) data to estimate ϵt under different wind and sea conditions. The used methodology consisted of decomposing the backscatter SAR return in terms of two contributions: a polarized contribution, associated with the fast response of the local wind (Bragg backscattering), and a non-polarized (NP) contribution, associated with wave breaking (Non-Bragg backscattering). Wind and wave parameters were estimated from the NP contribution and used to calculate ϵt from a parametric model dependent of these parameters. The results were analyzed using wave model outputs (WAVEWATCH III) and previous measurements documented in the literature. For the prevailing wind seas conditions, the ϵt estimated from pol-SAR data showed good agreement with dissipation associated with breaking waves when compared to numerical simulations. Under prevailing swell conditions, the total energy dissipation rate was higher than expected. The methodology adopted proved to be satisfactory to estimate the total energy dissipation rate for light to moderate wind conditions (winds below 10 m s-1), an environmental condition for which the current SAR polarimetric methods do not estimate ϵt properly.
RESUMO
Pentolite is a mixture (1:1) of 2,4,6-trinitrotoluene (TNT) and pentaerythritol tetranitrate (PETN), and little is known about its fate in the environment. This study was aimed to determine the dissipation of pentolite in soils under laboratory conditions. Microcosm experiments conducted with two soils demonstrated that dissipation rate of PETN was significantly slower than that of TNT. Interestingly, the dissipation of PETN was enhanced by the presence of TNT, while PETN did not enhanced the dissipation of TNT. Pentolite dissipation rate was significantly faster under biostimulation treatment (addition of carbon source) in soil from the artificial wetland, while no such stimulation was observed in soil from detonation field. In addition, the dissipation rate of TNT and PETN in soil from artificial wetland under biostimulation was significantly faster than the equivalent abiotic control, although it seems that non-biological processes might also be important for the dissipation of TNT and PETN. Transformation of PETN was also slower during establishment of enrichment culture using pentolite as the sole nitrogen source. In addition, transformation of these explosives was gradually reduced and practically stopped after the forth cultures transfer (80 days). DGGE analysis of bacterial communities from these cultures indicates that all consortia were dominated by bacteria from the order Burkholderiales and Rhodanobacter. In conclusion, our results suggest that PETN might be more persistent than TNT.