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Cryptosporidium and Giardia (oo)cyst concentrations are frequently used for assessing drinking water safety. The widely used USEPA Method 1623 provides total counts of (oo)cysts, but may not be accurate for human health risk characterization, since it does not provide infectivity information. The total counts and infectious fraction of Cryptosporidium oocysts and the total counts of Giardia cysts were assessed in major fecal pollution sources. Fresh calf and cow feces, their manure, and the discharge point were sampled in a small rural sub-watershed (n ¼ 20, 21, 10, 10). Median concentrations for total (oo)cysts were higher in calves (333 oocysts g À1 ; 111 cysts g À1 ) than in cows (52 oocysts g À1 ; 7 cysts g À1 ). Infectious oocysts were found in 17 (7%) of the samples and none were found in manure or at the discharge point. Urban sources were sampled in the influent and effluent (n ¼ 19, 18) of two wastewater treatment plants. Peak concentrations were 533 oocysts L À1 and 9,010 cysts L À1 for influents and 89 oocysts L À1 and 472 cysts L À1 for effluents. Infectious oocyst fractions varied from below the detection limit to 7-22% in the effluent and influent respectively.These infectious fractions are significantly lower than those currently used for quantitative microbial risk assessment estimates.

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Michaud, A. R. and Laverdière, M. R. 2004. Cropping, soil type and manure application effects on phosphorus export and bioavailability. Can. J. Soil Sci. 84: 295-305. A simulated rainfall study was conducted on an array of 36 runoff plots (6 m 2 each) deployed on three benchmark soil series of the Missisquoi region in southwestern Québec. The split-plot experimental design tested the effects and interactions of pig slurry treatment as main plots (check vs. 59 kg P ha -1 ) and cropping (tilled vs. hay) as subplots, on runoff volume and concentrations in total suspended sediment (TSS), total phosphorus (TP), dissolved reactive soluble P (DRP), particulate P (PP) and bioavailable P (BioP). TP concentration in runoff ranged from a low of 1.17 mg L -1 average on non-amended Bedford hay, to a peak concentration average of 9.55 mg L -1 on manured and tilled Saint-Sébastien plots. Variance analysis indicated significant contributions of treatments in explaining TP concentration in runoff as follows: Soil type effect > Cropping effect > Soil × Cropping interaction > Manure effect. Erosion and sediment transport processes were identified as prime vectors of TP export. Manure effect alone accounted for 35% of overall DRP variability, while soil type alone accounted for 70% of variability in particulate P bioavaibility (BioP/PP). Among practical implications of this study is the importance of assessing PP bioavaibility to adequately predict the adverse impact of runoff on aquatic ecosystems. The high level of interaction among cropping and manure treatment and the site-specific influence of soil physical and chemical properties also calls for a holistic approach to nonpoint P risk assessment and management, that focusses on timely manure P management, control of soil P build-up and agricultural practices minimizing surface runoff.Key words: Phosphorus, P-index, rainfall simulation, runoff, erosion, bioavailability, sediment Michaud, A. R. et Laverdière, M. R. 2004. Effets de la couverture végétale, de l'apport de lisier et du type de sol sur l'exportation de phosphore et sa biodisponibilité. Can. J. Soil Sci. 84: 295-305. Une étude faisant intervenir une simulation de pluie fut conduite sur un réseau de 36 parcelles expérimentales de 6 m 2 distribuées sur trois séries de sol caractéristiques de la région de Missisquoi, au Québec. Le dispositif expérimental en tiroirs a mis en relief les effets et les interactions des traitements d'apport de lisier de porc en parcelle principale (témoin vs. 59 kg P ha -1 ) et de couverture du sol en parcelle secondaire (sol nu vs. prairie) sur le volume de ruissellement et ses concentrations en matières en suspension (MES), phosphore total (PT), P réactif dissout (PRD), P particulaire (PP) et P biodisponible (Pbio). Les concentrations observées en PT ont varié d'un minimum de 1.17 mg L -1 sur le loam argileux Bedford en prairie, non amendé, à un maximum de 9.55 mg L -1 sur le loam Saint-Sébastien en condition de sol nu et amendé à partir de lisier de porc. L'analyse de variance indiqua que l...