Analysis and assessment of precipitation chemistry at Caribou,Maine

Over the last 30 yr, Caribou, Maine has been the only U.S. collection site which has been a part of all four national precipitation chemistry networks. Due to its remote but strategically important location, the data from this site are very useful in evaluating transboundary transport of the major ions present in precipitation. This paper assesses the reliability of the Caribou data base and looks at the more recent data with the aid of the GAMBIT (Gridded Atmospheric Multilevel Backward Isobaric Trajectory) model. An examination of the historical data base indicates serious contamination problems in pre-1980 samples, particularly with S0₄ measurements. The trajectory climatology shows that the largest number of precipitation events track along the U.S. coast. Preliminary chemistry measurements indicate highest concentrations of H+ and S0₄ occur from events associated with trajectories passing through southern Canada.     

Gonadal recrudescence and induced spawning in Barbus altianalis

Gonadal recrudescence in Barbus altianalis from River Nile, Jinja (33°05E; 0°45N) Uganda was studied prior to induced spawning. Oocytes in B. altianalis were found to develop in cohorts suggesting batch spawning throughout the year with pronounced spawning activities coinciding with rainfall peaks of April and September. There was a strong positive correlation between rainfall and gonadosomatic index (r_S = 0.75, P = 0.008). B. altianalis had low fecundity (6.0 ± 2.0 per gram) and large‐sized eggs (2.97 ± 0.1 mm). Induced spawning was successful with exogenous hormones and water current. Results from this study suggested that total striping may not be appropriate, but larger eggs would confer high survival of offsprings under optimal conditions. The success registered in induced spawning of B. altianalis provides a breakthrough in seed production for multiplication and culture of this economically important fish species.     

Spatial distribution of water status in irrigated olive orchards by thermal imaging

Information regarding tree water status in irrigated olive orchards is essential for managing growth to optimize yields and olive oil quality. One management practice option is to monitor or sample individual trees and use this information for orchard-scale management. This study assessed the ability of thermal imaging to provide the spatial distribution and variability of tree water status in a commercial irrigated olive orchard, and described strategies and a procedure for choosing which individual trees best represent the orchard. The study employed gradual upscaling from individual trees grown in lysimeters, through a controlled experimental field plot, to a commercial orchard. Thermal imaging of olive trees grown in lysimeters attested the sensitivity of the technique to identify mild-level water stress by correlating crown temperatures to stem water potential. Knowledgeable choice of five or ten representative trees in the experimental plot, based on the histogram distribution obtained for the entire experimental orchard, lead to successful reconstruction of the spatial distribution of canopy temperature, and thus of water status. Positively skewed distributions of crown temperatures found in both the field plot and commercial orchard suggested distinct patterns, where the canopy temperature of the majority of the trees was lower than the average, and a relatively small number of trees had significantly higher temperatures and suggest commercial practicality of the proposed methodology. Thermal imaging can therefore serve as a useful tool for determining representative trees that, if frequently monitored, or instrumented with continuous water status sensors, can provide important information for orchard water management.     

Fine-root rhizosphere and morphological adaptations to site conditions in interaction with tree mineral nutrition in young silver birch (<Emphasis Type="Italic">Betula pendula</Emphasis> Roth.) stands

Limited nutrient acquisition from soil is a key process limiting productivity in boreal forest. We investigated short-root morphological adaptations and rhizosphere effect in relation to site conditions in interaction with tree mineral nutrition. We studied seven young (8- to 14-year-old) silver birch (Betula pendula Roth.) stands on abandoned agricultural land in Estonia. Soil pH varied from 3.8 to 7.0, and soil N % from 0.07 to 0.26%. Tree nutrient (NPK) status was expressed by leaf nutrient concentrations. Leaf N correlated negatively with short-root specific length and area. Summed activity (SA) and metabolic diversity of bacteria (by BIOLOG Ecoplate™), bacterial community diversity (by DGGE) and pH_KCl were determined for rhizosphere (R) and bulk soil (S) to reveal the extent of the rhizosphere effect. Bacterial activity in rhizosphere was 1.4–4.7 times higher than in bulk soil. Ratio SA_R/SA_S indicating root support to the rhizosphere bacterial communities decreased with increasing bulk soil pH; however, when bulk soil pH was ≥5, the decrease in SA_R/SA_S was insignificant, i.e. the rhizosphere effect stayed at a stable level. Diversity of bacterial community was 6% higher in bulk soil than in rhizosphere. Rhizosphere acidification occurred in studied stands when bulk soil pH_KCl ≥ 5. Short-root N % correlated positively with SA_R/SA_S. We concluded that tree N-nutritional status was related to short-root morphological parameters but not to studied microbiological characteristics in the soil of young silver birch stands.     

Fluidity of bound hydration layers

We have measured the shear forces between solid surfaces sliding past each other across aqueous salt solutions, at pressures and concentrations typical of naturally occurring systems. In such systems the surface-attached hydration layers keep the compressed surfaces apart as a result of strongly repulsive hydration forces. We find, however, that the bound water molecules retain a shear fluidity characteristic of the bulk liquid, even when compressed down to films 1.0 +/- 0.3 nanometer thick. We attribute this to the ready exchange (as opposed to loss) of water molecules within the hydration layers as they rub past each other under strong compression.     

Stable Incorporation of Co2+ into Ferrite Structure at Ambient Temperature: Effect of Operational Parameters

Removal of heavy metals (HM) from industrial wastewater is of primary environmental importance. The seeded ambient temperature ferrite process, in which heavy metals are removed from solution by their incorporation into a magnetite structure, is an attractive alternative for both complete metals separation and generation of stable magnetic sludge. Despite its potential, the effects of various operational parameters on the composition and stability of the final product are not fully understood to-date. The current paper addresses the combined effect of selected operational parameters on Co²⁺ incorporation efficiency. Co²⁺, which is used in many industries (e.g., plating, alloys manufacturing, catalytic converters, and paint pigments) and hence may pose a significant environment risk, was shown previously to be incorporated successfully into ferrite structures. Co²⁺-bearing ferrites were synthesized from Fe(II) solutions at ambient temperature (20 and 30°C), applying slow oxidation, pH 10.5, 20 g (as Fe) l^?1 ferrite seed, and different Fe²⁺ to Co²⁺ influent ratios. Pure magnetite was used as an initial seed, which was gradually exchanged, as the reaction proceeded, by the Co²⁺-bearing ferrite generated within the reactor (until full exchange at steady state). Under all conditions investigated >99% of the Co²⁺ was removed from solution (yielding Co²⁺ levels below 20 μg/l in the effluent) while the generated precipitates were composed predominately of magnetite/ferrite (based on XRD analysis). Favorable results in terms of Co²⁺ incorporation efficiency and sludge stability were obtained when the following operational conditions were applied: 1:10 Co²⁺:Fe²⁺ molar influent ratio, 30°C, 1,500 mgFe²⁺ l^?1 metal intermediate concentration, and 16 h aging period (pH 10.5).