Suspended particulate grain size dynamics and their implications for trace metal sorption in the Don River

We examined particle size distributions of suspended particulate matter (SPM); physical and environmental influences on the observed distributions; and relationships between particle size and geochemical partitioning of metals, over the fall and winter period in a small urban river (Don River, Toronto, Ontario, Canada). For this dataset, the majority of particles (80%) in suspension were less than 10 µm in size. In addition, while total SPM concentrations showed a positive trend with increasing discharge (Q); the proportions of particles found within given size classes were independent of both SPM concentration and Q. Temperature was the only measured environmental variable related to the particle concentrations within size classes. As water temperature increased, the concentration of particles in the smallest size class (1–4 µm) decreased, while the concentration of silt and/or algae sized particles (10–50 µm) increased. Increasing water temperatures may promote bacterial attachment to particles and their subsequent flocculation into larger sized particles. Decreasing concentrations of leachable (most labile) Cd, Zn and Mn were associated with increasing concentrations of the largest particles (70–150 µm) in suspension. In contrast, higher reducible (oxides) associated concentrations of Cd, Zn and Mn occurred with increasing concentrations of smaller particles (1–10 µm) in suspension. Both of these trends are speculated to reflect the importance of particle surface area for metal sorption reactions.     

An integrated data-directed numerical method for estimating the undiscovered mineral endowment in a region

An integrated data-directed numerical method has been developed to estimate the undiscovered mineral endowment within a given area. The method has been used to estimate the undiscovered uranium endowment in the San Juan Basin, New Mexico, U.S.A. The favorability of uranium concentration was evaluated in each of 2,068 cells defined within the Basin. Favorability was based on the correlated similarity of the geologic characteristics of each cell to the geologic characteristics of five area-related deposit models. Estimates of the undiscovered endowment for each cell were categorized according to deposit type, depth, and cutoff grade. The method can be applied to any mineral or energy commodity provided that the data collected reflect discovered endowment.     

Nutrient conditions in the Euboikos Gulf (west Aegean)

The Euboikos Gulf is a restricted embayment on the eastern coast of Greece, having a significant, unusual tidal phenomenon, and receiving some industrial and domestic wates. The South Euboikos Gulf has only slightly greater concentrations of nutrients than background, while the North Euboikos Gulf tends to accumulate nutrients, in particular nitrate and silicate. Also a comparison is made with the nutrient concentrations in polluted coastal gulfs of the Aegean. The different nutrient levels are due to the different sources of nutrients, as well as the morphology of each area and the circulation of the waters.     

Characteristics of the sea breeze in Attica,Greece

The characteristics of the sea breeze in the Attica region of Greece, in which Athens is located, have been studied for occasions of weak synoptic-scale pressure gradient. The analysis is based on synoptic observations from six meteorological stations, three on the coast and three inland. The three inland stations and one of the coastal stations lie almost in a straight line at different distances from the coast. For each meteorological station, the basic characteristics of the sea breeze were determined, i.e.,

1. The mean number of sea-breeze days for each calendar month.
2. The monthly mean wind speed for each synoptic hour.
3. The times of onset and cessation of the sea breeze.
4. The monthly vector mean wind, and its constancy ‘Constancy’ is defined as 100{itV{inr}/V{ins}}, where {itV{inr}} is the magnitude of the vector mean wind, and {itV{ins}} is the scalar mean wind speed. See Brooks and Carruthers (1953). (In this paper, the factor 100 is not used.) for each synoptic hour.
5. For days on which there was a sea breeze at Helliniko (the coastal reference station), the percentage number of days on which there was also a sea breeze at the given station.

An attempt was also made to determine further characteristics, such as the inland penetration of the sea breeze, its depth, the spatial and temporal variation of wind speed and direction, and the existence of the return flow. Finally, the properties of the land breeze are briefly outlined.     

Delay coordinates: a sensitive indicator of nonlinear dynamics in single charged particle motion in magnetic reversals

The delay coordinate technique is examined as an indicator of the regime of particle dynamics for the system of single charged particle motion in magnetic reversals. Examples of numerically integrated trajectories in both static (zero electric field) and time dependent (corresponding nonzero induction electric field) simple models for magnetic reversals are considered. In the static case, the dynamics can in principle be directly classified by constructing Poincaré surfaces of section; here we demonstrate that whilst the Poincaré surface contains the relevant information to classify the dynamics, the corresponding delay coordinate plot can provide a far more sensitive indication of the onset of nonregular behaviour. In the case of nonperiodic time dependence considered here Poincaré plots cannot in general be constructed directly. Nevertheless, delay coordinate plots can still reveal details of the phase space portrait of the system, and here are shown to indicate whether segments of stochastic motion exist in a given trajectory. It is anticipated that the delay coordinate plot technique as realized here will be a valuable tool in characterizing the behaviour in large numbers of trajectories that are evolved in time-dependent systems, thereby giving us insight into the evolution of the distribution function as a whole, either in prescribed fields or in self-consistent numerical simulations.