Surface water methane (CH4) and nitrous oxide (N2O) concentrations and fluxes were investigated in two subtropical coastal embayments (Bramble Bay and Deception Bay, which are part of the greater Moreton Bay, Australia). Measurements were done at 23 stations in seven campaigns covering different seasons during 2010-2012. Water-air fluxes were estimated using the Thin Boundary Layer approach with a combination of wind and currents-based models for the estimation of the gas transfer velocities. The two bays were strong sources of both CH4 and N2O with no significant differences in the degree of saturation of both gases between them during all measurement campaigns. Both CH4 and N2O concentrations had strong temporal but minimal spatial variability in both bays. During the seven seasons, CH4 varied between 500% and 4000% saturation while N2O varied between 128 and 255% in the two bays. Average seasonal CH4 fluxes for the two bays varied between 0.5 ± 0.2 and 6.0 ± 1.5 mg CH4/(m2·day) while N2O varied between 0.4 ± 0.1 and 1.6 ± 0.6 mg N2O/(m2·day). Weighted emissions (t CO2-e) were 63%-90% N2O dominated implying that a reduction in N2O inputs and/or nitrogen availability in the bays may significantly reduce the bays' greenhouse gas (GHG) budget. Emissions data for tropical and subtropical systems is still scarce. This work found subtropical bays to be significant aquatic sources of both CH4 and N2O and puts the estimated fluxes into the global context with measurements done from other climatic regions. 相似文献
The possible mechanisms of colloid generation at the near field/far field interface of a radioactive repository have been investigated by means of novel column experiments simulating the granite/bentonite boundary, both in dynamic and in quasi-static water flow conditions. It has been shown that solid particles and colloids can be detached from the bulk and mobilised by the water flow. The higher the flow rate, the higher the concentration of particles found in the water, according to an erosion process. However, the gel formation and the intrinsic tactoid structure of the clay play an important role in the submicron particle generation even in the compacted clay and in a confined system. In fact, once a bentonite gel is formed, in the regions where the clay is contacted with water, clay colloids can be formed even in quasi-static flow conditions. The potential relevance of these colloids in radionuclide transport has been studied by evaluating their stability in different chemical environments. The coagulation kinetics of natural bentonite colloids was experimentally studied as a function of the ionic strength and pH, by means of time-resolved light scattering techniques. It has been shown that these colloids are very stable in low saline (approximately 1 x 10(-3) M) and alkaline (pH > or = 8) waters. 相似文献
In July 2012, a ship-board double-platform line-transect survey was conducted to assess harbour porpoise (Phocoena phocoena) abundance in the Kattegat, Belt Seas and the Western Baltic. A total of 826 km of track lines were surveyed between the 2nd and 21st of July 2012, and 169 observations were made by the primary observers, comprising a total of 230 porpoises. Fifty-seven observations were identified as duplicate sightings observed by both tracker and primary observers and were used to correct for availability and perception bias of the primary detections. Using Mark–Recapture Distance Sampling analysis, we produced a model using the half-normal key function, including sightability as the only covariate to estimate the density and abundance of harbour porpoise within the 51,511 km2 survey area. Estimated detection probability on the transect line, known as g(0), was at 0.571 (±0.074; CV = 0.130). Using a point independence model of the detection function, the abundance of harbour porpoises within the survey area was estimated at 40,475 animals (95 % CI 25,614–65,041, CV = 0.235) with an associated density of 0.786 animals km?2 (95 % CI 0.498–1.242, CV = 0.235) and an average group size of 1.488 animals. These results reflect densities obtained during the SCANS surveys in 1994 and 2005, indicating no significant population trend in the area. However, it should be noted that the survey area covers more than one population and that results are therefore not necessarily reflecting local population trends. Until proper population borders are obtained, the abundance estimate provides baseline data for future monitoring and is an important input to the assessment of the conservation status of harbour porpoises in the area. 相似文献
Literature data concerning the genotoxicity of cobalt salts have been conflicting. To establish appropriate incubation conditions, we conducted a series of uptake studies, before genotoxicity was determined by DNA strand break induction in HeLa cells and mutagenicity in V79 Chinese hamster cells. Co(II) is taken up by HeLa cells in a concentration‐dependent manner and is accumulated inside the cell. The uptake is preceded by a fast association step to the outer membrane, with no saturation up to 24 h. DNA strand breaks as determined by nucleoid sedimentation are induced at concentrations as low as 50μMCoCl2. The induction is time‐dependent, showing the highest number of breaks after 4h incubation with no further increase up to 24h. CoCl2 is mutagenic at the HPRT‐locus, enhancing the spontaneous mutation frequency 4.2‐fold at 100μ?. Besides direct interactions with DNA, the mutagenicity of CoCl2 could also be due to a decrease in the Fidelity of DNA polymerisation. 相似文献
Heterogeneous photocatalysis is highlighted to treat volatile organic compound (VOC) emission. Then, this work analysed the influence of palladium (Pd) content loaded in TiO2 on n-octane and iso-octane photodegradation. For this, TiO2 was loaded with Pd in different contents: 0.4%, 0.7%, and 1.0%. The samples were characterized, and the photodegradation experiments were conducted by Pd/TiO2/UV process. The characterization analyses showed that the metal presence did not change the catalyst structure or its surface area; however, it reduced the bandgap energy. The photocatalytic results proved that palladium improved n-octane degradation from 62% (pure TiO2) to 92.6% (0.4%Pd/TiO2) and, iso-octane degradation enhanced from 59% (pure TiO2) to 90.6% (0.7%Pd/TiO2); all results were obtained in the space time of 39 s. Therefore, 0.4%Pd/TiO2 and 0.7%Pd/TiO2 showed better oxidation results to degradation n-octane and iso-octane, respectively. The kinetic model of pseudo-first order showed a good fit for the data of both VOCs. Heterogeneous photocatalysis with Pd/TiO2 showed to be an adequate technique to reduce VOCs emission.