Groundwater flow and contaminant transport modeling applications in urban area: scopes and limitations

Background

A three-dimensional groundwater flow model was used to evaluate the groundwater potential and assess the effects of groundwater withdrawal on the regional water level and flow direction in the central Beijing area. A program of groundwater modeling aimed at estimating current contaminant fluxes to the central area and site streams via groundwater was developed.

Results and discussion

The conceptual model developed for the site attempted to incorporate a complex stratigraphic profile in which groundwater flow and contaminant transport is strongly controlled by a shallow aquifer. Here, a conceptual model for groundwater flow and contaminant transport in central Beijing is presented.

Conclusion

Model simulations indicated that a sharp drop in the hydraulic head occurs at the center of the model area, which generates a cone of depression and a continuous decline of head with respect to time as a result of heavy groundwater abstraction.     

Genotoxicity of methyl parathion in short‐term bacterial test systems

Abstract

Genotoxicity of the insecticide methyl parathion was investigated in Salmonella typhimurium and Escherichia coli bacterial test systems for the detection of back mutations and DNA‐damage. Methyl parathion was mutagenic to S. typhimurium strain TA100 after activation with rat liver microsomal and cytosolic enzymes. In DNA repair tests, methyl parathion was effective in inducing damage to the S. typhimurium strain TA1538 which lack excision repair compared to the strain TA1978 which is proficient in excision repair mechanisms. Normal laboratory light conditions had no effect on the mutagenicity tests, however, exposure of methyl parathion in the petri dish containing the tester strain TA100 and rat liver microsomal and cytosolic enzymes reduced the mutagenic activity and increased the toxic effects of methyl parathion.     

Evaluation of Beta‐naphthoxyacetic Acid for Mutagenic Activity in the Salmonella/mammalian Microsome Assay

1,3‐β‐d‐Glucan derived from baker's yeast was chemically modified in two steps yielding crosslinked carboxymethyl glucan as the sodium salt (2). After cation exchange with hexadecyltrimethylammonium chloride, a hydrophobic adsorbent (3) was obtained which showed an excellent binding of the estrogenic mycotoxin zearalenone with a maximum adsorption of up to 183 mg/g. Compound 3 additionally showed a relatively high adsorption capacity for the trichothecene T‐2 toxin of at least 10 mg/g. Starting from 2, various derivatives were prepared by cation exchange using quaternary ammonium salts bearing substituents besides methyl from four to 18 carbon atoms. The adsorption of T‐2 toxin on these derivatives were compared with compound 3 leading to the conclusion that 3 is the best adsorbent of all investigated tetraalkylammonium‐modified derivatives of 2.     

Governance of water supply systems in the Palestinian Territories: A data envelopment analysis approach to the management of water resources

This study demonstrates that data envelopment analysis (DEA) can be a useful tool to assess the relative efficiencies of water supply systems and to establish benchmarks with which to measure progress in the management of water resources. Frontier efficiency models measure the efficiency of water use in the Palestinian Territories (West Bank and the Gaza Strip). At the municipality level, sufficient data for the years 1999-2002 were available to estimate efficiency and stability scores. The Gaza Strip efficiency scores were considerably lower than those of the West Bank. Water losses were the major source of the inefficiency as indicated by the large slacks of this input. The relative sizes of the municipalities affect efficiency scores little. Palestinian policy makers should focus on rebuilding the infrastructure of the water networks, beginning with the most DEA inefficient municipalities in order to minimize water losses.     

The relationship between multiple levels of learning practices and objective and subjective organizational financial performance

Multi‐level learning approaches suggest that individuals, groups and organizations act both independently and interact dynamically to contribute to organizational performance. We directly examined this proposition in an Australian sample using a longitudinal design that employed subjective and objective financial performance data. Respondents completed a survey that provided details on their individual, team and organizational learning practices (ILP, TLP and OLP, respectively), and self assessed performance compared to 3 years ago. Concurrently, we collected objective performance data (sales/employee numbers) at 3 yearly intervals and averaged these data to create an index. Using hierarchical and moderated regression, we found a positive main effect for OLP with both subjective and objective performance. Main effects for ILP and TLP were not found. Further, we found a significant interaction between ILP and TLP such that the effect of TLP on productivity was better in organizations with less ILP. Three‐way interactions were not found. Overall, these results provide some support for the model. We discuss some limitations of the study and make recommendations for future studies. Copyright © 2009 John Wiley & Sons, Ltd.     

People,pigs and pollution – Experiences with applying participatory learning and action (PLA) methodology to identify problems of pig-waste management at the village level in Fiji

Participatory learning and action (PLA) methodology was used at the village level in Fiji to identify and understand factors that influence two selected communities in implementing changes to current pig-waste management practices. The focus area was the Coral Coast in the south of Viti Levu island, where international tourism is expanding but stream and coastal waters are under threat of pollution from the largely uncontrolled release of pig waste into the local environment. The investigation found that participatory approaches are effective at the village level if correct tools are used and if the research process adapts to community needs. In particular, PLA methods in the two study villages (Komave and Votua) were able to assist different demographic groups to identify and then prioritise a range of pig-waste problems, including deteriorating water quality, public health and agricultural sustainability. Encouragement by PLA facilitators for communities to take ownership of these problems led eventually to one village installing a new pig-management system. This has become a showcase as a successful local-scale rural development project with long-term benefits for the local environment and the continuing growth of tourism in the area.     

Biosorption of lead and cadmium using marine algae

The use of algae (Ulva fasciata, green and Sargassum sp., brown) to reduce lead and cadmium levels from mono-metal solutions was investigated. The brown algae showed higher efficiency for the accumulation of lead (～1.5 times) and cadmium (～2 times) than green algae. The optimum pH value is found to be between 4 and 5.5. Regarding biomass concentration, an increase in metals percentage removal and a decrease in metal uptake capacity coincided with the increase in biomass concentration. All light metals (Ca, Mg and Na) showed a suppressive effect on biosorption capacity. The enhancement of biosorption in the case of NaOH was obvious. The biosorption process (65–90%) occurred within 3?min. Experimental data were in high agreement with the pseudo-second-order kinetic model and Freundlich model for lead and cadmium biosorption using different biosorbents. In the desorption study, 0.2?mol?L^?1 HCl recorded the best concentration for the elution of metals from the biomass. The biosorption capacity decreased over the four operational cycles for both lead and cadmium. Infrared analysis showed that amino, hydroxyl and carboxyl functional groups provide the major biosorption sites for metal binding. Use of the above-mentioned algae for cheap metal absorbance is considered as one water treatment criterion.     

Preparation and Thermo-Mechanical Characterization of Chitosan Loaded Methylcellulose-Based Biodegradable Films: Effects of Gamma Radiation

Chitosan (0.1–1%, w/w), dissolved in 2% acetic acid solution, was added into 1% methylcellulose (MC)-based formulation containing 0.5% vegetable oil, 0.25% glycerol and 0.025% Tween^?80. Films were prepared by casting. Puncture strength (PS), puncture deformation (PD), viscoelasticity coefficient and water vapour permeability (WVP) of the films were measured. The PS value of 312 N/mm was observed for MC-based films containing 0.25% chitosan. Values of PD, viscoelasticity coefficient and WVP of these films were 5.0 mm, 44.1%, and 6.0 g mm/m² day kPa, respectively. The MC-based films containing 0.25% chitosan were also exposed to gamma radiation (0.5–50 kGy). The PS of the treated films decreased significantly from 312 at 0 kGy to 201 N/mm when treated at a dose of 50 kGy. However, WVP values were not affected by increasing irradiation the dose used. The Fourier Transform Infrared spectroscopy supported the molecular interactions due to addition of chitosan in MC-based films. Thermo gravimetric analysis and differential scanning calorimetric experiments showed that thermal properties of the films were significantly improved by chitosan loading. Surface topography of the films was studied by scanning electron microscopy and found rougher due to chitosan addition.