Adaptation of the chlorophycean Dictyosphaerium chlorelloides to stressful acidic, mine metal-rich waters as result of pre-selective mutations

Several species of microalgae, closely related to mesophilic lineages, inhabit the extreme environment (pH 2.5, high levels of metals) of the Spain's Aguas Agrias Stream water (AASW). Consequently, AASW constitutes an interesting natural laboratory for analysis of adaptation by microalgae to extremely stressful conditions. To distinguish between the pre-selective or post-selective origin of adaptation processes allowing the existence of microalgae in AASW, a Luria-Delbrück fluctuation analysis was performed with the chlorophycean Dictyosphaerium chlorelloides isolated from non-acidic waters. In the analysis, AASW was used as selective factor. Preselective, resistant D. chlorelloides cells appeared with a frequency of 1.1 x 10(-6) per cell per generation. AASW-resistant mutants, with a diminished Malthusian fitness, are maintained in non-extreme waters as the result of a balance between new AASW-resistant cells arising by mutation and AASW-resistant mutants eliminated by natural selection (equilibrium at c. 12 AASW-resistants per 10(7) wild-type cells). We propose that the microalgae inhabiting this stressful environment could be the descendents of chance mutants that arrived in the past or are even arriving at the present.     

A model for supply chains environmental performance analysis and decision making

The need to include environmental criteria in the analysis of supply chains is increasingly recognized as a result both of limitations that are posed by legislation and regulations as well as of various motivations that a company may have. A decision model is proposed in this paper based on environmental performance indicators, which may support decision making in the case of supply chains in the presence of environmental considerations. The model uses a set of principles applicable to supply chains design and operation available from previous research work.     

Kinetics of soil ozonation: an experimental and numerical investigation

This study investigates the use of ozone for soil remediation. Batch experiments, in which ozone-containing gas was continuously recycled through a soil bed, were conducted to quantify the rate of ozone self-decomposition and the rates of ozone interaction with soil organic and inorganic matter. Column experiments were conducted to measure ozone breakthrough from a soil column. Parameters such as ozone flow rate, soil mass, and ozonation time were varied in these experiments. After ozone concentration had reached steady state, the total organic carbon concentration was measured for all soil samples. The ozonation efficiency, represented by the ratio of soil organic matter consumed to the total ozone input, was quantified for each experiment. Numerical simulations were conducted to simulate experimentally obtained column breakthrough curves. Experimentally obtained kinetic rate constants were used in these simulations, and the results were in good agreement with experimental data. In contrast to previous studies in which soil inorganic matter was completely ignored, our experiments indicate that soil inorganic matter may also promote depletion of ozone, thus reducing the overall ozonation efficiency. Three-dimensional numerical simulations were conducted to predict the efficacy of ozonation for soil remediation in the field. These simulations indicate that such ozonation can be very effective, provided that effective circulation of ozone is achieved through appropriately placed wells.     

On the plausible association between environmental conditions and human eye damage

The increase in solar ultraviolet radiation can have various direct and indirect effects on human health, like the incidence of ocular damage. Data of eye damage in residents of three suburban regions in Greece and in two groups of monks/nuns and fishermen are examined here. The statistics performed on these data provides new information about the plausible association between increased levels of solar ultraviolet radiation, air-pollution at ground level, and the development of ocular defects.