Influence of ripening on pHstat leaching behaviour of heavy metals from dredged sediments

The influence of oxidation and ripening on the kinetics of heavy metal release from anoxic sediments was investigated by means of porewater analysis and pH(stat) leaching tests. During simulated land disposal of an anoxic river sediment, a considerable heavy metal (Cd, Zn and Ni) release into the porewater was observed after 25 days of exposure of the sediment to the air. The release kinetics of Cd and Zn during pH(stat) leaching indicated that their release was related to the oxidation of Cd- and Zn-sulfides. It was not completely clear whether the release of Ni was due to the oxidation of Ni-sulfides or to the introduction of H(+)(generated by the oxidation of sulfides or introduced by titration). The release of Cu seemed to be explained by the oxidation of both Fe-sulfides and Cu-sulfides. As such, pH(stat) experiments provided an indirect way to assess the mineralogy of the anoxic sediment. During ripening of the sediment, the release rate of Zn and Cd in pH(stat) leaching tests increased. For Ni, however, a similar release pattern was observed in the anoxic sediment and in the ripened sediments. Two weeks' drying at 100 degrees C resulted in an increase in the leachability of Cu. Nevertheless, at pH 4 and 6, the thermally treated sediment displayed a slower leaching of Cd and Zn than the ripened sediment. Although thermal treatment is often used to simulate ageing in soils, it cannot be used to simulate ripening of anoxic sediments.     

Assessment of sociocultural acceptability of biogas from faecal waste as an alternative energy source in selected areas of Benin City,Edo State,Nigeria

Environment, Development and Sustainability - The use of wastes for biogas production has been restricted to few feedstock like cattle manure and food waste. Increasing the feedstock base for...     

Sleeping with a broken promise: The moderating role of generativity concerns in the relationship between psychological contract breach and insomnia among older workers

This paper examines the relationship between psychological contract breach and insomnia among older workers (aged 40 years and up). Drawing upon the conservation of resources theory, we conceptualize breach as a stressful event characterized by a perceived threat, failure to gain, or actual loss of valued resources, which increases psychological distress and insomnia. Moreover, we hypothesized that older workers' generativity concerns would act as a personal resource that would buffer the negative impact of breach. We tested our proposed model in 2 studies (Study 1 = 123; Study 2 = 168) of employee–spouse dyads. Results revealed that psychological distress mediated the relationship between psychological contract breach and insomnia. These mediated relationships were significant for those with low, but not for those with high levels of generativity concerns. These effects remained significant even after controlling for perceived organizational support (i.e., a social exchange mechanism). Theoretical and practical implications are discussed.     

Decolorization does not always mean detoxification: case study of a newly isolated Pseudomonas peli for decolorization of textile wastewater

The textile industry is a favor to the Tunisian economy by offering several job positions. However, it’s not environmentally friendly. In fact, textile industries discharge high volumes of wastewater which contain several toxic pollutants such as dyes, fixator, and whiteness. In our study, Pseudomonas peli, isolated and characterized from Oued Hamdoun (center of Tunisia), was found able to decolorize textile effluent about 81 % after 24 h shaking incubation. On the other hand, the in vitro antiproliferative effects of the untreated and treated effluent was evaluated by their potential cytotoxic activity using the MTT colorimetric method against three human cancer cell lines (A549, lung cell carcinoma; HT29, colon adenocarcinoma; and MCF7, breast adenocarcinoma). Results showed that intact textile effluent and its content azo dyes didn’t inhibit the proliferation of all tested cell lines. However, the cytotoxic effect was remarkable when we tested effluent obtained after treatment by P. peli in a dose-dependent manner. This activity was attributed to the presence, in our treated effluent, of some azo products of dyes which are responsible for inhibition of human cell lines proliferation. Thus, the use of this strain for testing on the industrial scale seems impossible and disadvantageous.     

The environmental potential of reuse: an application to used books

Reuse is generally considered to have environmental benefits, but it has not yet been widely adopted in environmental policy or strategy. In this paper, a simple model of second-hand markets is explored with a case study of used books that illustrates the behavior of the model and shows that such a model is consistent with the data. Three questions of the dynamics of reuse are addressed: (1) If it becomes easier to buy and sell used goods (via Internet markets or other means), by how much will sales of used goods increase? (2) When sales of used goods increase, by how much will sales of new goods decrease? (3) When is reuse better than recycling? Expanding from the case study, the model is used to examine how reuse affects the consumption of new goods, and the relative merits of reuse versus recycling. When the used goods market is small, the ratio of the price of used and new goods, an observable quantity, is approximately equal to the fractional decrease in sales of new goods that will result from increased sales of used goods. A formulation of the environmental impact of reuse and recycling is developed that includes the market impact of reuse. Illustrating this formulation for books with a simplified analysis, reuse of books through sales in a second-hand market is estimated to save more than twice as much energy, with considerable uncertainty, than making books from recycled paper. The formulation provides a basis for identifying products and markets for which reuse can be an effective environmental strategy.     

Spatial assessment of fin whale hotspots and their association with krill within an important Antarctic feeding and fishing ground

Fin whale (Balaenoptera physalus quoyi) habitat use and its relationship to environmental conditions are generally unknown in the Southern Ocean, presenting challenges for predicting their seasonal occurrence and potential effects of fishing pressure and climate change on this endangered species. Using biological data collected during 14 shipboard surveys off the northern Antarctic Peninsula and oceanographic data from satellite remote sensing, we mapped the distribution of fin whale hotspots, Antarctic krill abundance (biomass from acoustics, concentrations from nets) and ocean conditions during mid- and late-summer to investigate the environmental determinants of whale hotspots. Generalized additive models (GAM) were used to test the hypothesis that intra-seasonal changes in fin whale hotspot distribution relate to sea surface temperature (SST), krill abundance and eddy kinetic energy (EKE). More whale hotspots (sightings and individuals) are observed during late- than mid-summer surveys. During mid-summer, hotspots occurred near Elephant Island while in late-summer they were distributed throughout the slope region in proximity to the mean location of the southern Antarctic Circumpolar Current Front. The spatial mean of EKE did not differ between mid- and late-summer surveys, but the spatial mean of SST was significantly warmer during late-summer. The GAM for mid-summer indicates that fin whale hotspots were positively related to SST, EKE and acoustically determined krill biomass. The GAM for late-summer indicates the hotspots were negatively related to net-based krill abundance and positively related to acoustic krill biomass and EKE. This study is important because environmental determinants of fin whale hotspots may be used as reference points for implementing future conservation plans for their recovering populations.     

Can chemical oxidation improve the permeability of infiltration basins?

The Rapid Infiltration and Extraction (RIX) facility, a soil aquifer treatment system, began taking secondary effluent from the City of San Bernardino, California, in 1996. The gradual decrease in the hydraulic conductivity of the infiltration basins at RIX has been attributed to the accumulation of organic matter in the surface sand. Periodic tillage of the surface sand to restore the permeability has mixed this organic matter to a depth of nearly 50 cm. We hypothesized that in situ chemical oxidation of the surface sand might improve the infiltration rate and increase the time between filling and drying cycles. The effect of organic matter oxidation on sand permeability was tested in laboratory sand columns treated with sodium hypochlorite, calcium hypochorite, and ozone gas. All oxidants significantly decreased the hydraulic conductivity of the surface sand. The loss in permeability was attributed to an increase in dispersed clay plus silt-sized particles that were released as a result of oxidation. This study suggests that ex situ sand-washing operations, currently being used to clean the sand, could be improved by the addition of oxidants to the wash water.     

Environmentally stratified sampling design for the development of Great Lakes environmental indicators

Understanding the relationship between human disturbance and ecological response is essential to the process of indicator development. For large-scale observational studies, sites should be selected across gradients of anthropogenic stress, but such gradients are often unknown for a population of sites prior to site selection. Stress data available from public sources can be used in a geographic information system (GIS) to partially characterize environmental conditions for large geographic areas without visiting the sites. We divided the U.S. Great Lakes coastal region into 762 units consisting of a shoreline reach and drainage-shed and then summarized over 200 environmental variables in seven categories for the units using a GIS. Redundancy within the categories of environmental variables was reduced using principal components analysis. Environmental strata were generated from cluster analysis using principal component scores as input. To protect against site selection bias, sites were selected in random order from clusters. The site selection process allowed us to exclude sites that were inaccessible and was shown to successfully distribute sites across the range of environmental variation in our GIS data. This design has broad applicability when the goal is to develop ecological indicators using observational data from large-scale surveys.