Current and emerging strategies for organophosphate decontamination: special focus on hyperstable enzymes

Organophosphorus chemicals are highly toxic molecules mainly used as pesticides. Some of them are banned warfare nerve agents. These compounds are covalent inhibitors of acetylcholinesterase, a key enzyme in central and peripheral nervous systems. Numerous approaches, including chemical, physical, and biological decontamination, have been considered for developing decontamination methods against organophosphates (OPs). This work is an overview of both validated and emerging strategies for the protection against OP pollution with special attention to the use of decontaminating enzymes. Considerable efforts have been dedicated during the past decades to the development of efficient OP degrading biocatalysts. Among these, the promising biocatalyst SsoPox isolated from the archaeon Sulfolobus solfataricus is emphasized in the light of recently published results. This hyperthermostable enzyme appears to be particularly attractive for external decontamination purposes with regard to both its catalytic and stability properties.     

Effects of chronic exposure to radiofrequency electromagnetic fields on energy balance in developing rats

The effects of radiofrequency electromagnetic fields (RF-EMF) on the control of body energy balance in developing organisms have not been studied, despite the involvement of energy status in vital physiological functions. We examined the effects of chronic RF-EMF exposure (900 MHz, 1 V?m^?1) on the main functions involved in body energy homeostasis (feeding behaviour, sleep and thermoregulatory processes). Thirteen juvenile male Wistar rats were exposed to continuous RF-EMF for 5 weeks at 24 °C of air temperature (T _a) and compared with 11 non-exposed animals. Hence, at the beginning of the 6th week of exposure, the functions were recorded at T _a of 24 °C and then at 31 °C. We showed that the frequency of rapid eye movement sleep episodes was greater in the RF-EMF-exposed group, independently of T _a (+42.1 % at 24 °C and +31.6 % at 31 °C). The other effects of RF-EMF exposure on several sleep parameters were dependent on T _a. At 31 °C, RF-EMF-exposed animals had a significantly lower subcutaneous tail temperature (?1.21 °C) than controls at all sleep stages; this suggested peripheral vasoconstriction, which was confirmed in an experiment with the vasodilatator prazosin. Exposure to RF-EMF also increased daytime food intake (+0.22 g?h^?1). Most of the observed effects of RF-EMF exposure were dependent on T _a. Exposure to RF-EMF appears to modify the functioning of vasomotor tone by acting peripherally through α-adrenoceptors. The elicited vasoconstriction may restrict body cooling, whereas energy intake increases. Our results show that RF-EMF exposure can induce energy-saving processes without strongly disturbing the overall sleep pattern.     

Chronic toxicity of ZnO nanoparticles, non-nano ZnO and ZnCl2 to Folsomia candida (Collembola) in relation to bioavailability in soil

The chronic toxicity of zinc oxide nanoparticles (ZnO-NP) to Folsomia candida was determined in natural soil. To unravel the contribution of particle size and free zinc to NP toxicity, non-nano ZnO and ZnCl₂ were also tested. Zinc concentrations in pore water increased with increasing soil concentrations, with Freundlich sorption constants K_f of 61.7, 106 and 96.4 l/kg (n = 1.50, 1.34 and 0.42) for ZnO-NP, non-nano ZnO and ZnCl₂ respectively. Survival of F. candida was not affected by ZnO-NP and non-nano ZnO at concentrations up to 6400 mg Zn/kg d.w. Reproduction was dose-dependently reduced with 28-d EC50s of 1964, 1591 and 298 mg Zn/kg d.w. for ZnO-NP, non-nano ZnO and ZnCl₂, respectively. The difference in EC50s based on measured pore water concentrations was small (7.94-16.8 mg Zn/l). We conclude that zinc ions released from NP determine the observed toxic effects rather than ZnO particle size.     

Enhanced removal of heavy metals in primary treatment using coagulation and flocculation.

The goal of this study was to determine the removal efficiencies of chromium, copper, lead, nickel, and zinc from raw wastewater by chemically enhanced primary treatment (CEPT) and to attain a total suspended solids removal goal of 80%. Operating parameters and chemical doses were optimized by bench-scale tests. Locally obtained raw wastewater samples were spiked with heavy metal solutions to obtain representative concentrations of metals in wastewater. Jar tests were conducted to compare the metals removal efficiencies of the chemical treatment options using ferric chloride, alum, and anionic polymer. The results obtained were compared with those from other studies. It was concluded that CEPT using ferric chloride and anionic polymer is more effective than CEPT using alum for metals removal. The CEPT dosing of 40 mg/L ferric chloride and 0.5 mg/L polymer enhanced heavy metals removal efficiencies by over 200% for chromium, copper, zinc, and nickel and 475% for lead, compared with traditional primary treatment. Efficient metals capture during CEPT can result in increased allowable headworks loadings or lower metal levels in the outfall.     

Reaction capacity characterization of shallow sedimentary deposits in geologically different regions of the Netherlands

Quantitative insight into the reaction capacity of porous media is necessary to assess the buffering capacity of the subsurface against contaminant input via groundwater recharge. Here, reaction capacity is to be considered as a series of geochemical characteristics that control acid/base conditions, redox conditions and sorption intensity. Using existing geochemical analyses, a statistical regional assessment of the reaction capacity was performed for two geologically different areas in the Netherlands. The first area is dominated by Pleistocene aquifer sediments only, in the second area a heterogeneous Holocene confining layer is found on top of the Pleistocene aquifer sediments. Within both areas, two or more regions can be distinguished that have a distinctly different geological build-up of the shallow subsurface. The reactive compounds considered were pyrite, reactive Fe other than pyrite, sedimentary organic matter, carbonate and clay content. This characterization was complemented by the analysis of a dataset of samples newly collected, from two regions within the Pleistocene area, where the sedimentary facies of samples was additionally distinguished. The statistical assessment per area was executed at the levels of region, geological formation and lithology class. For both areas, significant differences in reaction capacities were observed between: 1. different lithology classes within a geological formation in a single region, 2. identical geological formations in different regions and 3. various geological formations within a single region. Here, the reaction capacity is not only controlled by lithostratigraphy, but also by post-depositional diagenesis and paleohydrology. Correlation coefficients among the reactive compounds were generally higher for sand than for clay, but insufficiently high to allow good estimation of reactive compounds from each other. For the sandy Pleistocene aquifer sediments, the content of reactive compounds was frequently observed to be below detection limits. From this, future characterization of sediment reaction capacity is best performed at the sublevel of lithology class, being the geochemically near-uniform unit identifiable for individual geological formations within geographic regions. Additional subdivision on facies provides particular insight in the spatial entity where relatively high reaction capacities may be encountered. To obtain quantitative insight into the reaction capacity of aquifer sediments, non-sandy minor subunits should be well characterised on their reaction capacity as well as their spatial occurrence in the geological formations. A straightforward approach is presented in which the regional statistics on geochemical reactivity become combined with a 3-dimensional geological voxel model. This results into 3-dimensional data fields on reactivity, which are suitable for, for example, groundwater transport modelling. The sedimentological architecture of the deposits becomes well maintained in the geochemical data field, which is an advantage in itself.     

Plasma vitellogenin in male teleost fish from 43 rivers worldwide is correlated with upstream human population size

It has been previously demonstrated that vitellogenin (VTG) - a precursor egg yolk protein - is produced in male fish exposed to estrogenic compounds in wastewater treatment plant (WWTP) effluent. However, little attention has been given to examine whether any patterns of male VTG production exists across fish species on a global scale. We hypothesized that a composite measure of human population size over river discharge would best explain variations of protein levels in male fish. We compiled VTG data in 13 fish species from 43 rivers receiving municipal WWTP effluent on 3 continents. We found that human population size explained 28% of the variation in male VTG concentrations, whereas population/flow rate failed to significantly correlate with VTG. We suggest this result may be explained by the low solubility of estrogenic compounds, resulting in localized contamination near WWTP outfalls, rather than dilution by river water.     

Geological factors controlling occurrence and distribution of arsenic in groundwaters from the southern margin of the Duero Basin,Spain

Groundwater from springs and boreholes on the southern edge of the Cenozoic Duero Basin (DB) of Spain has concentrations of arsenic (As) which are commonly above the EC drinking-water limit of 10 μg/L and reach observed values up to 241 μg/L. Groundwater compositions within the sedimentary aquifer vary from Ca–HCO₃ type, variably affected by evaporation and agricultural pollution at shallow levels, to Na–HCO₃ compositions in deeper boreholes of the basin. Groundwater conditions are mainly oxidising, but reducing groundwaters exist in sub-basins within the aquifer, localised flow paths likely being influenced by basement structure. Arsenic concentrations are spatially variable, reaching up to 38 μg/L in springs of the Spanish Central System (SCS) basement aquifer and up to 62 μg/L in springs from the DB. Highest As concentrations are associated with the Na–HCO₃ compositions in deep boreholes (200–450 m depth) within the DB. These have high pH values (up to 9.6) which can give rise to associated elevated concentrations of V and U (up to 64 and 30 μg/L, respectively). In the deep borehole waters of the DB, oxidising flows derived from the mineralised igneous–metamorphic basement and discharging via major faults, and are considered the origin of the higher concentrations. Compositions are consistent with desorption of As and other anionic species from metal oxyhydroxides in an oxic environment. Under locally reducing conditions prevalent in some low-flow parts of the DB, an absence of detectable dissolved As is coincident with low or undetectable SO₄ concentrations, and consistent with loss via formation of authigenic sulphide minerals. Mitigation measures are needed urgently in this semi-arid region where provision of alternative sources of safe drinking water is logistically difficult and expensive.     

A model for a species with two life history stages and added mortality

A differential equation model of a species with two life stages is constructed, and the behavior of the equilibria investigated when density-independent mortality is continuously imposed. With density dependence largely in recruitment, an increase in either life stage is possible even though mortality is being imposed on both life stages. The equilibrium of a given life stage can increase if density dependence is mainly in that stage.The most effective stage to attack is that which is numerically dominant. With species having a high reproductive potential the most effective way of reducing either stage is to attack the stage with the lesser natural density-independent mortality.Certain parameter values allow multiple positive steady states. Data from Lucilia cuprina appear to conform to some of the predictions of the model.     

Urban development grant — an early assessment of regional implications

An examination of the Urban Development Grant during its first round of operation reveals that certain regions, particularly the West Midlands and London, are winning considerably more funding than others. A change in this trend is likely to require a reassessment, by the Government, of the targetting criteria presently used to direct the grant to areas of need.