Methane Flux from Drained Northern Peatlands: Effect of a Persistent Water Table Lowering on Flux

Measurements of CH4 flux from drained and undrained sites in three northern Ontario peatlands (a treed fen, a forested bog, and a treed bog) were made from the beginning of May to the end of October 1991. In the drained portions, the water table had been lowered between 0.1 and 0.5 m, compared to the water table of the undrained portion of the peatlands. The mean seasonal CH4 flux from the undrained portions of three peatlands was small, ranging from 0 to 8 mg m-2d-1, but similar to the CH4 flux from other treed and forested northern peatlands. The mean seasonal CH4 flux from the drained portion of the peatlands was either near zero or slightly negative (i.e., uptake): fluxes ranged from 0.1 to -0.4 mg m-2d-1. Profiles of CH4 in the air-filled pores in the unsaturated zone, and the water-filled pores of the saturated zone of the peat at the undrained sites, showed that all the CH4 produced at depth was consumed within 0.2 m of the water table and that atmospheric CH4 was consumed in the upper 0.15 m of the peatland. On the basis of laboratory incubations of peat slurries to determine CH4 production and consumption potentials, the lowering of the water table eliminated the near-surface zone of CH4 production that existed in the undrained peatland. However, drainage did not alter significantly the potential for CH4 oxidation between the water table and peatland surface but increased the thickness of the layer over which CH4 oxidation could take place. These changes occurred with a drop in the mean summer water table of only 0.1 m (from -0.2 to -0.3 m) suggesting that only a small negative change in soil moisture would be required to significantly reduce CH4 flux from northern peatlands

Antimicrobials and antimicrobial resistant bacteria in Australia

The prevalence of antimicrobial resistant bacteria (ARB) is a global health issue. ARB can be considered a contaminant of emerging concern through their regular discharge to the aquatic environment from wastewater treatment plants (WWTPs). This chapter focuses on the prevalence of antimicrobials and ARB through wastewater treatment and discharge to the environment in an Australian context. Despite the apparent dominance of WWTP effluent, the agricultural ionophore monensin was the frequently detected antimicrobial in surface waters. An analysis of antibiotic resistance genes in reclaimed water and environmental water samples used for irrigated agriculture found that the presence of these genes in environmental samples from an impacted river system was scarce, but their presence was quite prevalent in reclaimed water samples. The impact of the observations on public health and the potential for the emergence and spread of antibiotic resistance through the aquatic environment demands further investigation to maintain the vigilance against the spread of infectious disease