Stable elements of radioecological importance in certain echinoderm species

Echinoderms may present variations in their elementary composition according to the surrounding medium and to their food sources. The accumulation of certain trace elements by these organisms is of radioecological interest, besides the biological one. The elements cobalt, zinc, chromium, caesium, silver, tin, iron, rubidium, selenium and scandium were determined in seven echinoderm species by neutron activation analysis and γ-ray spectroscopy. In this work the calculated values of the concentration factors of the determined elements are reported and discussed from the radioecological point of view.     

Artificial neural networks as an alternative approach to groundwater numerical modelling and environmental design

Classical optimization methodologies based on mathematical theories have been developed for the solution of various constrained environmental design problems. Numerical models have been widely used to represent an environmental system accurately. The use of methodologies such as artificial neural networks (ANNs), which approximate the complicated behaviour and response of physical systems, allows the optimization of a large number of case scenarios with different set of constraints within a short period of time, whereas the corresponding simulation time using a numerical model would be prohibitive. In this paper, a combination of an ANN with a differential evolution algorithm is proposed to replace the classical finite‐element numerical model in water resources management problems. The objective of the optimization problem is to determine the optimal operational strategy for the productive pumping wells located in the northern part of Rhodes Island in Greece, to cover the water demand and maintain the water table at certain levels. The conclusions of this study show that the use of ANN as an approximation model could (a) significantly reduce the computational burden associated with the accurate simulation of complex physical systems and (b) provide solutions very close to the optimal ones for various constrained environmental design problems. Copyright © 2008 John Wiley & Sons, Ltd.