Predicting fly ash resistivity—an evaluation

Recently a technique for predicting fly ash resistivity from an as-received, ultimate coal analysis and the chemical composition of the coal ash produced by simple laboratory ignition was published. This paper evaluates this technique by comparing predicted resistivity data with laboratory measured values, in situ resistivity data, and precipitator performance information acquired from 12 field test programs. Considering the precision of measurement generally encountered in precipitator technology and the limited amount of certain laboratory data available, the results are encouraging and the evaluation is favorable.     

Grasshopper spermatocyte chromosomal changes induced by pH alterations

The Science of Nature -     

Modeling pesticide volatilization from turf

Pesticide volatilization models are typically based on equilibrium partitioning of the chemical into solid, liquid, and gaseous phases in the soil environment. In turf systems direct vaporization from vegetation surfaces is a more likely source, and it is difficult to apply equilibrium methods to plant material due to the uncertainties of solid-liquid-gas partitioning. An alternative approach is to assume that pesticide volatilization is governed by the same processes that affect water evaporation. A model was developed in which evapotranspiration values, as determined by the Penman equation, were adjusted to chemical vaporization using ratios of water and chemical saturated vapor pressures and latent heats of vaporization. The model also assumes first-order degradation of pesticide on turf vegetation over time. The model was tested by comparisons of predictions with measurements of volatilization for eight pesticides measured during 3 to 7 d in 11 field experiments. Measured volatilization fluxes ranged from 0.1 to 22% of applied chemical. Pesticides were divided into two groups based on saturated vapor pressures and organic C partition coefficients. One pesticide was selected from each group to calibrate the model's volatilization constant for the group, and the remaining pesticides were used for model testing. Testing results indicated that the model provides relatively conservative estimates of pesticide volatilization. Predicted mean losses exceeded observations by 20%, and the model explained 67% of the observed variation in volatilization fluxes. The model was most accurate for those chemicals that exhibited the largest volatilization losses.     

River temperature sensitivity to hydraulic and meteorological parameters

A sensitivity analysis is performed to evaluate river temperature variations in response to changes in hydraulic and meteorological conditions. The effects of instream flow, river geometry, and weather factors on daily mean and daily maximum river temperatures are quantified by analytical solutions to a simplified model. The influence coefficient method is used to determine river temperature sensitivity. The sensitivity analysis presents quantitative evidence that river temperatures are more sensitive to instream flowrate, upstream inflow temperature, air temperature, humidity and solar radiation than to other parameters including wind speed and channel geometry and morphometry. It is found that the sensitivity of river temperatures to flow is as significant as that to weather. Daily maximum river temperature is more sensitive to flowrate than daily mean temperature. Adapting the concept of 'diminishing returns', a critical instream flowrate is identified, which divides high and low sensitivity of water temperatures to flowrate. The critical flowrate can be used to determine practically achievable and economically feasible flow requirements for summer river temperature control. The sensitivity results can assist in streamflow management and reservoir operation for protections of habitat and aquatic environment.     

Glutathione and cysteine biosynthesis in two varieties of Abelmoschus esculentus in response to mine spoil

The extent of accumulation of some heavy metals and glutathione and cysteine levels in the roots and aerial plant parts in two genotypically different varieties of A. esculentus (KS404 and BO2) exposed to mine spoil were investigated. Glutathione (GSH) level in both the varieties on control sites increased from basal level to 155.15 nmol g(-1) dry weight (d.wt.), almost 1.5 fold on 30 day and attained a plateau within 60 day Mine spoil exposure of both the varieties decreased glutathione 1.13 fold (89.2 nmol g(-1) dry weight) during 60 day from its basal level. GSH concentration in shoots of these varieties increased accompanying growth contrary to roots where it finally declined 2 fold. Cysteine content in control plants increased 2 fold (31.6 nmol g(-1) dry weight) on 30 day and finally declined 1.38 fold (22.35 nmol g(-1) dry weight, at 60 day). Both the varieties, when exposed to mine spoil, showed enhanced cysteine content almost 2 fold during 30 day (50.95 nmol g(-1) dry weight) but failed to increase further Forshoots in both the varieties challenged with mine spoil, cysteine maxima reached late (15.2 nmol g(-1) dry weight, at 40 day) relative to control but the levels declined subsequently (11.85 nmol g(-l) dry weight). Contrary to GSH, cysteine content in roots of both the varieties responded positively to mine spoil as apparent from the 2.23 fold increase during 30 d than basal level although it lowered to a level of 12.85 nmol g(-1) dry weight finally at 60 day. Both the varieties accumulated almost maximum level of selected cations (Fe > Mn> Zn> Cu > Ni) during 30 day, but BO2 variety was significantly superior in this regard. Invariably high accumulation of such cations in roots over shoots indicated accumulation, retention or restricted translocation from root to shoot. The metal share of the edible part was just 6% of the plant load. Thus, present work reflects a genotypic differences in metal accumulation and that affected the major non-enzymatic traits or synthesis of sulthydryl compounds as well. The present results also indicate that metal tolerance is in part associated with anti-oxidant system activity.     

Nutrient-limited toxin production and the dynamics of two phytoplankton in culture media: A mathematical model

In this paper we have proposed and analyzed a simple mathematical model consisting of four variables, viz., nutrient concentration, toxin producing phytoplankton (TPP), non-toxic phytoplankton (NTP), and toxin concentration. Limitation in the concentration of the extracellular nutrient has been incorporated as an environmental stress condition for the plankton population, and the liberation of toxic chemicals has been described by a monotonic function of extracellular nutrient. The model is analyzed and simulated to reproduce the experimental findings of Graneli and Johansson [Graneli, E., Johansson, N., 2003. Increase in the production of allelopathic Prymnesium parvum cells grown under N- or P-deficient conditions. Harmful Algae 2, 135–145]. The robustness of the numerical experiments are tested by a formal parameter sensitivity analysis. As the first theoretical model consistent with the experiment of Graneli and Johansson (2003), our results demonstrate that, when nutrient-deficient conditions are favorable for the TPP population to release toxic chemicals, the TPP species control the bloom of other phytoplankton species which are non-toxic. Consistent with the observations made by Graneli and Johansson (2003), our model overcomes the limitation of not incorporating the effect of nutrient-limited toxic production in several other models developed on plankton dynamics.     

Application of a value-based equivalency method to assess environmental damage compensation under the European Environmental Liability Directive

The Environmental Liability Directive (ELD) establishes a framework of liability based on the ‘polluter-pays’ principle to prevent and remedy environmental damage. The ELD requires the testing of appropriate equivalency methods to assess the scale of compensatory measures needed to offset damage. The aim of this paper is to contribute to fill the existing knowledge gap on the application of the value equivalency approach for damage compensation in this context. We analyze the toxic spill damaging the Doñana National Park (Spain) in 1998. The welfare losses associated with the resource damage are estimated using non-market valuation and compared to the value of the compensatory measures taken after the accident. Our results show that the in-kind compensation may have been insufficient to offset the welfare losses. We conclude that a more comprehensive knowledge of the human welfare effects caused by environmental damage is of substantial importance to determine compensatory remediation, as insufficient information in this respect can lead to erroneous decisions causing loss to society.