We report the solid-liquid partitioning of Cd, Cu, Ni, Pb, and Zn in 60 organic horizon samples of forest soils from the Hermine Watershed (St-Hippolyte, PQ, Canada). The mean Kd values are respectively 1132, 966, 802, 3337 and 561. Comparison of those Kd coefficients to published compilation values show that the Kd values are lower in acidic organic soil horizons relative to the overall mean Kd values compiled for mineral soils. But, once normalized to a mean pH of 4.4, the Kd values in organic soil horizons demonstrate the high sorption affinity of organic matter, which is either as good as or up to 30 times higher than mineral soil materials for sorbing trace metals. Regression analysis shows that, within our data set, pH and total metal contents are not consistent predictors of metal partitioning. Indeed, metal sorption by the solid phase must be studied in relation to complexation by dissolved organic ligands, and both processes may sometime counteract one another.

We examined the consistency of diel patterns observed in fish and aquatic invertebrates over three 24-h cycles within a 10-day period in summer (28-29 July, 4-5 and 7-8 August 1997) in the River Lee, Hertfordshire, England. We tested for temporal variations in epibenthos density and population size structure, age-specific fish density, microhabitat use and contagion as well as for correlations between fish length and prey number (in the gut) per millimetre fish standard length, a surrogate of foraging success, and fish density in point samples (an estimator of shoal size). Consistent patterns were observed in invertebrates and fish, though variability was greater in the former. Epibenthic invertebrates (except Chironomidae) demonstrated few or no diel differences in density, but some differences in size (based on head widths) were found in larvae of Chironomidae and Ephemeroptera (mainly Baetis rhodani (Pictet) and Ephemerella ignita Poda) between times of day. Fish density varied consistently and diel variations were observed in fish shoaling behaviour, habitat use, prey size and prey composition. Prey numbers in the gut generally decreased with increasing shoal size, but this was significant in Gobio gobio L. only. In some fish species/size classes, prey numbers correlated either positively or negatively with habitat variables, in particular with the distance fish were captured from the bank. Despite relatively low epibenthic densities, Chironomidae larvae were a prominent and preferred food item in the diet of all fish species, followed by Ephemeroptera in some (0þ Barbus barbus (L.), 0þ and 1þ Barbatula barbatula (L.), 1þ and !2þ Cottus gobio (L.)) and Simuliidae in others (0þ and !1 þ G. gobio, 0þ Leuciscus cephalus (L.), 0þ and 1þ Phoxinus phoxinus (L.)), with Trichoptera larvae, Asellus sp., Ostracoda and Annelida as tertiary prey taxa. The relatively consistent diel patterns observed suggest that data from single 24-h cycles in late summer can be representative of daily patterns. Day-time only surveys of European riverine fishes may give unreliable estimates of mean fish population size and abundance.

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Abstract:This study examined hydropedological patterns and storage-discharge relationships towards catchment process understanding at a small forested site, the Hermine (Laurentians, Quebec, Canada). The catchment is characterized by a steep surface topography and a shallow, irregular, low-permeability soil layer (LPSL), thus offering two possible main hydrologic drivers for runoff generation and routing. Using spatially detailed topographic data of the soil surface and the LPSL, water table levels measured at 94 locations on 50 occasions were expressed as 5 perched groundwater (PGW) storage variables: (i) a binary index illustrating the presence/absence of surface water, (ii) a soil saturation deficit, (iii) a water table elevation above the LPSL, (iv) a classification of sites as being in a dry, filling or spilling subsurface depression, and (v) a water table elevation above an underlying filled subsurface depression. The most common proxies for PGW storage, namely the saturation deficit and the location of surface saturated areas, were least appropriate to portray the Hermine catchment dynamics. Patterns of PGW storage were initially important during a rainstorm to trigger a response at the outlet but then remained unchanged even though streamflows continued to increase up to a higher order of magnitude. Hydraulically limited water tables were shown to exist in some areas, thus hinting towards the coexistence of rapid lateral preferential flow and slower subsurface flow. Most importantly, discontinuous storage-discharge relationships at the point-scale combined into continuous relationships at the catchment-scale, a result which can be seen as an emergent property of the Hermine catchment.

The phytoextraction of the trace elements (TEs) As, Cd, Cu, Ni, Pb, and Zn by willow cultivars (Fish Creek, SV1 and SX67) was measured during a 3-year field trial in a mildly contaminated soil. Biomass ranged from 2.8 to 4.4 Mg/ha/year at 30,000 plants/ha. Shoots (62%) were the main component followed by leaves (23%) and roots (15%). Biomass was positively linked to soluble soil dissolved organic carbon, K, and Mg, while TEs, not Cd and Zn, had a negative effect. The TE concentration ranking was: Zn > Cu > Cd > Ni, Pb > As, and distribution patterns were: (i) minima in shoots (As, Ni), (ii) maxima in leaves (Cd, Zn), or (iii) maxima in roots (Cu, Pb). Correlations between soil and plant TE were significant for the six TEs in roots. The amounts extracted were at a maximum for Zn, whereas Fish Creek and SV1 extracted more TE than SX67. More than 60% (91-94% for Cd and Zn) of the total TE was in the aboveground parts. Uptake increased with time because of higher biomass. Fertilization, the selection of cultivars, and the use of complementary plants are required to improve productivity and Cd and Zn uptake.