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The aim of this study is to assess the synergetic effect of combined ultrasound and ozone treatment on the biological disinfection of water on a large-scale application using viable plate counts and flow cytometry. Escherichia coli B bacteria in saline suspension was treated using a commercially available combined ultrasound and ozone system (USO3 (Ultrasonic Systems Gmbh)) for 16 min. Two analytical methods were used to assess the results in terms of live and dead cells in the bulk liquid: standard viable plate counting recorded in terms of colony forming units per milliliter and flow cytometry. In the latter case 1 mL of bacterial suspension was stained simultaneously with the fluorescent stains SYTO9 and propidium iodide (PI). Transmission electron microscopy was used to generate images identifying the biological effects of different treatments using ultrasound and ozone on bacterial cell walls. Results demonstrated that treatment with ozone alone (1 mg/L) resulted in a significant reduction (93%) in the number of live cells after 16 min treatment whereas ultrasound alone showed only a small reduction (24%). However, a combination of ozone and ultrasound showed a synergistic effect and enhanced the inactivation to 99% after 4 min. A combined ultrasound and ozone treatment of bacterial suspensions using a commercial system affords a promising method for water disinfection that is better than treatment using either method alone. Standard viable plate count analysis is normally used to assess the effectiveness of disinfection treatments; however flow cytometry proved to be a more sensitive method to determine the actual effects in terms of not only live and dead cells but also damaged cells. This type of analysis (cell damage) is difficult if not impossible to achieve using traditional plate counting methodology.

Global atmospheric concentrations of nitrous oxide (N2O), a powerful greenhouse gas, continue to increase. While many sources and sinks have been identified, there is little known about how existing and newly constructed reservoirs, such as those created for hydroelectric production, impact current atmospheric N2O concentrations. We hypothesized that N2O fluxes to the atmosphere would increase because enhanced nutrient availability and increased soil respiration following the flooding of soils during reservoir creation would favor denitrification. Furthermore, we hypothesized that emissions would be linked to the amount of organic carbon contained in the flooded landscape. These hypotheses were tested by creating three experimental reservoirs over boreal upland subcatchments that ranged in the amount of organic carbon stored in soils and vegetation. Diffusive surface N2O fluxes within each reservoir were estimated using surface water concentrations of N2O and the thin boundary layer method. Surface fluxes ranged from -1.0 to -3.5 microg N2O m(-2) d(-1), and water column N2O concentrations indicated that contrary to expectations, the reservoirs were acting as slight sinks for atmospheric N2O. This net consumption of N2O was likely related to an excess of labile carbon and low concentrations of oxygen (O2) and nitrate (NO3-) in the flooded soils. Therefore, it is postulated that reservoir creation by flooding boreal soils will likely have little or no net effect of adding additional N2O to the current greenhouse gas (GHG) atmospheric burden, at least over the short term.

Polybrominated diphenyl ethers (PBDEs) have become widely distributed as environmental contaminants due to their use as flame retardants. Their structural similarity to other halogenated aromatic pollutants has led to speculation that they might share toxicological properties such as hepatic enzyme induction. In this work we synthesized a number of PBDE congeners, studied their affinity for rat hepatic Ah receptor through competitive binding assays, and determined their ability to induce hepatic cytochrome P-450 enzymes by means of EROD (ethoxyresorufin-O-deethylase) assays in human, rat, chick, and rainbow trout cells. Both pure PBDE congeners and commercial PBDE mixtures had Ah receptor binding affinities 10(-2)-10(-5) times that of 2,3,7,8-tetrachlorodibenzo-p-dioxin. In contrast with polychlorinated biphenyls, Ah receptor binding affinities of PBDEs could not be related to the planarity of the molecule, possibly because the large size of the bromine atoms expands the Ah receptor's binding site. EROD activities of the PBDE congeners followed a similar rank order in all cells. Some congeners, notably PBDE 85, did not follow the usual trend in which strength of Ah receptor binding affinity paralleled P-450 induction potency. Use of the gel retardation assay with a synthetic oligonucleotide indicated that in these cases the liganded Ah receptor failed to bind to the DNA recognition sequence.