Baits for tabanids (Diptera: Tabanidae) were tested in the Northwest Territories (60 °N) and Ontario (45 °N) using Nzi traps. Tests targeted ammonia, phenols/cow urine and octenol. About 200 000 tabanids were captured in 15 experiments with a maximum capture of 4182 in one trap in 1 day. In the Northwest Territories, phenols, urine and octenol were effective single baits for only some species. At both locations, adding ammonia to an unbaited or an octenol-baited trap had no effect on catches. By contrast, catches were increased for several species when ammonia was combined with phenols or urine. In Ontario, including ammonia in various baits increased catches by 1.5- to 3.4-fold relative to octenol alone for three Hybomitra and one Tabanus species. Synergism between ammonia and phenols was clearly demonstrated for the dominant Hybomitra species in Ontario (Hybomitra lasiophthalma), but not for the dominant species in the Northwest Territories (Hybomitra epistates). In five other northern Hybomitra species, baits of ammonia and/or octenol in combination with phenols resulted in a 1.7- to 4.1-fold increase in catch relative to an unbaited trap. Further tests of ammonia as a synergist for biting flies may prove useful in, for example, tsetse, which respond strongly to phenols.

The potential for using geosynthetic clay liners (GCLs) to mitigate metal mobility is dependent, in part, on consideration of its effectiveness as a diffusive barrier. In this context, laboratory-measured diffusion coefficients and supporting sorption data for metals (Al, As, Cd, Cu, Fe, K, Mg, Mn, Ni, Sr, Zn) are reported for the following four cases where a GCL might serve as an effective barrier material to metals and metalloids: acidic rock drainage, gold mine tailings, lime-treated mine effluent, and municipal solid waste. The average diffusion coefficients for Cu, Cd, Zn, Fe and Ni covered a narrow range from 0.67 × 10−10 to 0.89 × 10−10 m2/s. The diffusion coefficients for As, Al, Mg, Mn and Sr were in the range D = 0.80 × 10−10 to D = 1.6 × 10−10. The diffusive movement of other more common inorganic ions such as Ca, Na, S (SO4) and Cl are also considered, as well as the impact of pH, Eh and speciation on metal mobility in GCLs.

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The largest environmental problem facing the mining industry today is the leaching of hazardous metals and metalloids from waste rock and mine tailings. Although in the past Geosynthetic Clay Liners (GCLs) have primarily been employed as leachate barriers in landfills, recent times have seen an increase in the variety of their applications, including the mining industry (e.g. Olsta and Friedman, 2002). This study conducted a bulk material analysis of the GCL material following permeation with different mining solutions in order to elucidate possible mechanisms of metal retention. A synthesized Acid Mine Drainage (AMD) leachate and a neutral-pH, arsenic-rich leachate typically associated with gold mines (GML) were used to permeate GCL samples. Samples permeated with GML and AMD (5 Pore Volumes) resulted in hydraulic conductivity (K) values of 2.0x10-11 m/s and 6.0x10-11 m/s respectively from an initial K of 1.6x10-11 m/s. Most metals were significantly attenuated for all permeated samples. Material analysis of the GCL bentonite revealed how the metals were distributed within the GCL, as well as between the porewater and the soil matrix. For example, AMD samples showed an accumulation of metals in the upper layer of the GCL associated with iron and manganese oxy-hydroxide precipitation. X-ray diffraction (XRD) identified the formation of gypsum in all GML permeated samples. Such retention mechanisms are highlighted and consequences of environmental changes are discussed.

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