Sediment characteristics affecting bioavailability of heavy metals in flooding areas and intertidal zones along the river Scheldt

Mobility and bio-availability of heavy metals in intertidal zones and floodplains is currently studied at the Laboratory of Analytical Chemistry and Applied Ecochemistry (Ghent University). The relation between sediment properties and metal uptake by reed plants (Phragmites australis (Cav.) Steudel) was investigated based on field observations at selected locations along the estuary of the river Scheldt (Flanders, Belgium). The sites represented a varying degree of metal contamination and salinity. At each site, reed plants were sampled and analysed for heavy metals. Sediments were also sampled and characterised for metal contents and various physico-chemical properties. Cd contents of Phragmites australis (Cav.) Steudel were higher on sites with lower total Cd contents in the upper 20 cm of the sediments. Contents of leaves, stems and rhizomes were however positively and significantly correlated with the chloride content of the sediments. Zn contents were also higher on sites with lower total Zn contents in the sediments, but, in contrast to Cd, were negatively correlated with chloride contents. When the sites with the lowest salinity were considered separately, the Zn content of leaves and stems on the one hand and the ratio of exchangeable Zn to the total cation exchange capacity on the other hand were significantly and positively correlated. This can suggest that reed plants do not take up Zn selectively, and that the uptake and/or transfer mechanism is adapted at the highest salinity. Cu contents of the plants were negatively correlated with chloride contents in the sediments. However, Cu contents in leaves and stems were significantly and positively correlated with Cu contents in the reducible fraction of the sediments, according to the BCR sequential extraction procedure. At the sites with the largest reducible Cu fractions, the mean water level was also higher and the upper sediment layer was reduced at sampling time

Metal Concentrations in Soil Paste Extracts as Affected by Extraction Ratio

Saturated paste extracts are sometimes used to estimate metal levels in the soil solution. To assess the significance of heavy-metal concentrations measured in saturation extracts, soil paste extracts were prepared with distilled water in amounts ranging from 60–200% of the moisture content at saturation. Trace metals behaved as if a small pool consistently was dissolved independent of the extraction ratio applied. Metal concentrations in the solution hence were not buffered by the solid phase, but the observed behaviour would allow the estimation of metal concentrations in the soil solution as a function of moisture content. The behaviour of iron and manganese suggested that some microbial reduction occurred. The intensity increased with increasing extraction ratio but not to the extent of affecting dissolution of trace elements

A STUDY ON GAIT PATTERN BETWEEN OLD AND YOUNG ADULTS TO EVALUATE ELDERLY SHOE: PRELIMINARY STUDY

INTRODUCTION: There are differences between gait performance of old and that of young adults (Paroczai, 2006). It is believed that these differences might have effects on the developmental procedure of shoes for the elderly. However the standard of elderly shoe for development and evaluation is not enough. Traditional gait analysis methods (kinematics and kinetics) and gait variability were used. Gait variability can offer a complementary way of quantifying locomotion and its changes with aging and disease as well as a means of monitoring the effects of therapeutic interventions and rehabilitation (Hausdorff, 2007). Especially, according to recent studies, variability was closely related to gait stability (Hausdorff, 2007). The goal of this study was to find elderly gait pattern for evaluating elderly shoe based on stability point of view

DIFFERENCES IN GAIT DYNAMICS AMONG VARIOUS TYPES OF SHOE

INTRODUCTION: The foot provides an important source of feedback for locomotion (Nurse et al., 2005). The healthy locomotor system integrates input from the neuronal system as well as feedback from visual, vestibular and proprioceptive sensors (Hausdorff, 2007). Shoe constructions can support altering gait mechanics and/or stability training (Nigg et al., 2006). Particularly, feedback from the feet may be influenced by changing the types of shoe. According to recent studies, gait variability, such as stride-to-stride fluctuation, may be a biomechanical marker for changes of gait mechanics (Hausdorff, 2007; Peng et al., 1995). The study of gait variability offers a complementary way of quantifying locomotion and its changes with aging and disease as well as a means of monitoring the effects of therapeutic interventions and rehabilitation (Hausdorff, 2007). Then, usually temporal (stride interval time, swing interval time, stance interval time, step interval time, double support time) and spatial (stride length, step length, step width) variables were used for variability analysis. Thus, analyses for gait variability were so-called “gait dynamics“. And types of shoe may cause changes of gait performance during walking. In present study we would like to identify differences of gait dynamics (from variability point of views) between shoe types during treadmill walking

A STUDY ON THE RELATIONSHIP BETWEEN EYE MOVEMENT AND GRIP FORCE DURING GOLF PUTTING

Golf is becoming a very popular sports game. In golf games, there are four kinds of strokes: driving, Iron, chip shots and putting stroke. Among the strokes, putting stroke accounts between 42% and 45% in a golf rounding(Pelz, 2000) and most golfers have difficulties on doing it. There are various parameters affecting the results of a putting stroke but effects of a few parameters were studied(Delay, 1997). However, there is a lack of studies for the simultaneous measurement and analysis of eye movement, grip force, and kinematic parameters with putting results. A purpose of this study was to quantify the parameters and identify the relationship between eye movement, grip force, and putting results

A geometric constraint over k-dimensional objects and shapes subject to business rules

This report presents a global constraint that enforces rules written in a language based on arithmetic and first-order logic to hold among a set of objects. In a first step, the rules are rewritten to Quantifier-Free Presburger Arithmetic (QFPA) formulas. Secondly, such formulas are compiled to generators of k-dimensional forbidden sets. Such generators are a generalization of the indexicals of cc(FD). Finally, the forbidden sets generated by such indexicals are aggregated by a sweep-based algorithm and used for filtering. The business rules allow to express a great variety of packing and placement constraints, while admitting efficient and effective filtering of the domain variables of the k-dimensional object, without the need to use spatial data structures. The constraint was used to directly encode the packing knowledge of a major car manufacturer and tested on a set of real packing problems under these rules, as well as on a packing-unpacking problem

Factors affecting metal mobilisation during oxidation of sulphidic, sandy wetland substrates

Most metals accumulate as sulphides under anoxic conditions in wetland substrates, reducing their bioavailability due to the solubility of metal sulphides. However, upon oxidation of these sulphides when the substrate is occasionally oxidised, metals can be released from the solid phase to the pore water or overlaying surface water. This release can be affected by the presence of carbonates, organic matter and clay. We compared changes of Cd, Cu and Zn mobility (CaCl2 extraction) during oxidation of a carbonate-rich and a carbonate-poor sulphidic, sandy wetland substrate. In addition, we studied how clay with low and high cation sorption capacity (bentonite and kaolinite, respectively) and organic matter (peat) can counteract Cd, Cu and Zn release during oxidation of both carbonate-rich and carbonate-poor sulphidic sediments. CaCl2-extractability of Cu, a measure for its availability, is low in both carbonate-poor and carbonate-rich substrates, whereas its variability is high. The availability of Cd and Zn is much higher and increases when peat is supplied to carbonate-poor substrates. A strong reduction of Cd and Zn extractability is observed when clay is added to carbonate-poor substrates. This reduction depends on the clay type. Most observations could be explained taking into account pH differences between treatments, with kaolinite resulting in a lower pH in comparison to bentonite. These pH differences affect the presence and characteristics of dissolved organic carbon and the metal speciation, which in turns affects the interaction of metals with the solid soil phase. In carbonate-rich substrates, Cd and Zn availability is lower and the effects of peat and clay amendment are less clear. The latter can also be attributed to the high pH and lack of pH differences between treatments