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AIMS: A laboratory assay for comparative characterization of various faecal matrices with respect to faecal indicator organism (FIO) release using, artificial rain water. METHODS AND RESULTS: Fresh sheep and beef-cattle faeces, dairy cattle slurry and beef cattle farm yard manure (FYM) were collected from commercial units in south-west England and applied to 20 randomized 1 m(2) plots established on permanent grassland. Representative samples from each faecal matrix (n = 5) were collected on four occasions over 16 days. One gram of each sample was transferred to a sterile vial to which 9 ml of standard local rain was carefully pipetted. The vial was then rotated through 360 degrees, 20 times in 60 s to 'simulate' a standardized interaction of the faecal material with rainfall, providing an assay of comparative release potential. Appropriate decimal dilutions were prepared from the eluent. Following agitation, with a sterile spatula, the remaining faecal material and eluent in the vials were vortex mixed for 60 s before decimal dilutions were prepared from the resulting mixture, providing a quantitative assessment of the total FIO in the sample from which percentage release could be determined. Bacterial concentrations were enumerated in duplicate by membrane filtration following standard methods for FIO. Significant differences in release kinetics of Escherichia coli and enterococci from each of the faecal matrices were determined. CONCLUSIONS: Differences in release from each faecal substrate and between FIO type (E. coli and intestinal enterococci) were observed in this laboratory study. The order of release of E. coli from the faecal matrices (greatest to least, expressed as a percentage of the total present) was dairy cattle slurry > beef cattle FYM > beef-cattle faeces > sheep faeces. For intestinal enterococci the order of percentage release was dairy cattle slurry > beef-cattle faeces > beef cattle FYM > sheep faeces. SIGNIFICANCE AND IMPACT OF THE STUDY: This laboratory-based method provides the first data on the relative release kinetics of FIO from different faecal matrices in rain water. This is fundamental information needed to parameterize laboratory-based microbial models and inform approaches to field and catchment risk assessment.

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Effluent retention in a constructed wetland was determined using both microbial and chemical tracers. Seasonal variation in effluent retention was the main focus of the study. The biotracers used in the study were the coliphage MS2, a bacteriophage of Enterobacter cloacae and antibiotic resistant endospores of Bacillus globigii. Two separate tracer runs were conducted, Winter high flow (January 2002) and Summer low flow (June 2002). The three biotracers were evaluated simultaneously on both occasions, with the commonly used chemical tracer, rhodamine WT, a bright red fluorescent dye, being evaluated during the final experiment. The Winter tracer run was conducted during a typical Winter storm, with a mean effluent discharge of 4.1 ls(-1). Tracer recovery was 98% MS2, 91% Ent. cloacae phage and 2% endospore. Effluent retention was estimated at between 2 and 4 h at 90% phage tracer recovery. The Summer tracer run was conducted at a typical site operating discharge rate of 0.8 ls(-1). Tracer recovery was 23% MS2, 36% Ent. cloacae phage, 8% rhodamine and 14% for the endospores. Effluent retention was estimated at between 11 and 18 h at 90% of phage tracer recovery. Initial results are encouraging and indicate bacteriophage to have further potential as tracing agents in wetlands.

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AIMS: With concern surrounding the environmental impact of chemical tracers on the aquatic environment, this paper presents the initial evaluation of biotracers used to determine the effluent retention time, an important performance indicator, in a Free Water Surface Constructed Wetland. METHODS AND RESULTS: Production of the biotracers, coliphage MS2, and the bacteriophage of Enterobacter cloacae and antibiotic resistant endospores of Bacillus globigii is described in detail. Their subsequent use in three separate tracer experiments - January, March and June (2000) - revealed the variability of retention time with respect to effluent flow. The biotracer MS2 showed the constructed wetland had a retention time of 8-9 h at a mean discharge of 0.9 l s-1, increasing to 10-12 h at a mean discharge 0.3 l s-1. A similar retention of 9-10 h at a mean discharge of 0.3 l s-1 was calculated for the Ent. cloacae phage. In contrast, use of endospores revealed considerably longer retention times at these mean discharge rates; 12-24 h and 36-48 h, respectively. CONCLUSION: Biotracers could provide a useful and environmentally friendly technique to monitor effluent retention in constructed wetlands. At this stage the phage tracers appear particularly promising due to ease of isolation and recovery. SIGNIFICANCE AND IMPACT OF THE STUDY: Initial results are encouraging and have highlighted the potential of biotracers as alternatives to chemical tracers, even in microbially-rich waters.

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Solubilities of sphalerite (ZnS) and galena (PbS) were determined at 300 degrees to 500 degrees C and 1000 bars total pressure in a chemical environment buffered by silicate mineral equilibria. Chloride solutions and muscovite-bearing assemblages characteristic of hydrothermal wall-rock alteration were used; weak acidities at temperature were therefore involved. The metal concentrations encountered tended to be higher than those observed in high bisulfide-H(2)S systems at neutral to weakly basic pH used in most previous experimentation; the chemical conditions of the work, although not completely satisfactory, are geologically more realistic than previous experimentation done in the basic-pH region.