Differential use of conspecific-derived information by sexual and asexual parasitic wasps exploiting partially depleted host patches

When foraging partially depleted patches (i.e., a fraction of hosts are already parasitized), female parasitoids must decide: 1—whether to superparasitize, and 2—whether to stay in their current patch (thus missing the opportunity of finding a better patch elsewhere). To make these decisions, parasitoids may rely on different cues, produced both by the environment and by conspecifics. Animals thriving in different environments may differ in cues they use. In the solitary parasitoid Venturia canescens, thelytokous (asexual) and arrhenotokous (sexual) individuals are found in two contrasting environments. Thelytokous females, from anthropogenic conditions, are known to cope with superparasitism in an adaptive way. On the other hand, little is known about superparasitism by arrhenotokous females. We compared the host exploitation strategies of thelytokous and arrhenotokous females in partially depleted patches. Hosts parasitized by thelytokous females were more frequently avoided than those parasitized by arrhenotokous females, suggesting a stronger chemical marking of the former. Only thelytokous females used information from conspecifics for patch-leaving decisions. The conformity of the differences in the behavior of thelytokous and arrhenotokous females with the environmental conditions they experience in their habitat is discussed.     

Source-term development for a contaminant plume for use by multimedia risk assessment models

Multimedia modelers from the US Environmental Protection Agency (EPA) and US Department of Energy (DOE) are collaborating to conduct a comprehensive and quantitative benchmarking analysis of four intermedia models: MEPAS, MMSOILS, PRESTO, and RESRAD. These models represent typical analytically based tools that are used in human-risk and endangerment assessments at installations containing radioactive and hazardous contaminants. The objective is to demonstrate an approach for developing an adequate source term by simplifying an existing, real-world, ⁹⁰Sr plume at DOE's Hanford installation in Richland, WA, for use in a multimedia benchmarking exercise between MEPAS, MMSOILS, PRESTO, and RESRAD. Source characteristics and a release mechanism are developed and described; also described is a typical process and procedure that an analyst would follow in developing a source term for using this class of analytical tool in a preliminary assessment.     

Geochemical provenance and spatial distribution of fluoride in groundwater of Mayo Tsanaga River Basin, Far North Region, Cameroon: implications for incidence of fluorosis and optimal consumption dose

The 500,000 inhabitants of Mayo Tsanaga River Basin are vulnerable to a “silent” fluorosis from groundwater consumption. For the first time, the groundwater is investigated for the purpose of identifying the provenance of fluoride and estimating an optimal dose of fluoride in the study area. Based on the fluoride content of groundwater, fluorine and major oxides abundances in rocks from the study area, mean annual atmospheric temperature, and on-site diagnosis of fluorosis in children, the following results and conclusions are obtained: Fluoride concentration in groundwater ranges from 0.19 to 15.2 mg/l. Samples with fluoride content of <1.5 mg/l show Ca–HCO₃ signatures, while those with fluoride >1.5 mg/l show a tendency towards Na-HCO₃ type. Fluor-apatite and micas in the granites were identified as the main provenance of fluoride in the groundwater through water-rock interactions in an alkaline medium. The optimal fluoride dose in drinking water of the study area should be 0.7 mg/l, and could be adjusted downward to a level of 0.6 mg/l due to the high consumption rate of groundwater, especially during drier periods.     

Incorporating soil structure and root distribution into plant uptake models for radionuclides: toward a more physically based transfer model

Most biosphere and contamination assessment models are based on uniform soil conditions, since single coefficients are used to describe the transfer of contaminants to the plant. Indeed, physical and chemical characteristics and root distribution are highly variable in the soil profile. These parameters have to be considered in the formulation of a more realistic soil-plant transfer model for naturally structured soils. The impact of monolith soil structure (repacked and structured) on Zn and Mn uptake by wheat was studied in a controlled tracer application (dye and radioactive) experiment. We used Brilliant Blue and Sulforhodamine B to dye flow lines and 65Zn and 54Mn to trace soil distribution and plant uptake of surface-applied particle-reactive contaminants. Spatial variation of the soil water content during irrigation and plant growth informs indirectly about tracer and root location in the soil profile. In the structured monolith, a till pan at a depth of 30 cm limited vertical water flow and root penetration into deeper soil layers and restricted tracers to the upper third of the monolith. In the repacked monolith, roots were observed at all depths and fingering flow allowed for the fast appearance of all tracers in the outflow. These differences between the two monoliths are reflected by significantly higher 54Mn and 65Zn uptake in wheat grown on the structured monolith. The higher uptake of Mn can be modelled on the basis of radionuclide and root distribution as a function of depth and using a combination of preferential flow and rooting. The considerably higher uptake of Zn requires transfer factors which account for variable biochemical uptake as a function of location.     

An analysis of the environmental health impact of the Barekese Dam in Kumasi, Ghana

Although dams have beneficial effects, they are also acknowledged as having serious environmental repercussions if they are not properly managed. The objective of this work was to examine the impact of the Barekese Dam in Ghana on the health status of three riparian communities downstream against a control. The environmental health status of the communities was analysed with reference to traditional endemic communicable water-related diseases in the catchment area, which were identified as malaria, urinary schistosomiasis, infectious hepatitis, diarrhoeal diseases and scabies. Case-control study was then conducted in the three phases of the dam (pre-construction, at the end of the construction and in the late operational phases) to analyse the health status of the communities as a function of the phases of the dam. The results showed that the control community consistently had a much better health status than two of the riparian communities, which were closer to the dam in all the three phases. However, it had a better health status than the third riparian community, which was farthest downstream, only in the first two phases. This community maintained a fairly constant health status retrospectively and did not appear to have been affected by the presence of the dam. On contrary, the health status of the two communities in close proximity to the dam deteriorated in the late operational phase. The study therefore showed that there was a strong association between the presence of the dam and poorer health status of the downstream communities in close proximity to it.     

Toxicological effects of disinfections using sodium hypochlorite on aquatic organisms and its contribution to AOX formation in hospital wastewater

Sodium hypochlorite (NaOCl) is often used for disinfecting hospital wastewater in order to prevent the spread of pathogenic microorganisms, causal agents of nosocomial infectious diseases. Chlorine disinfectants in wastewater react with organic matters, giving rise to organic chlorine compounds such as AOX (halogenated organic compounds adsorbable on activated carbon), which are toxic for aquatic organisms and are persistent environmental contaminants. The aim of this study was to evaluate the toxicity on aquatic organisms of hospital wastewater from services using NaOCl in pre-chlorination. Wastewater samples from the infectious and tropical diseases department of a hospital of a large city in southeast of France were collected. Three samples per day were collected in the connecting well department at 9 a.m., 1 p.m. and 5 p.m. during 8 days from 13 March to 22 March 2001, and a mixture was made at 6 p.m. with the three samples in order to obtain a representative sample for the day. The toxicity test comprised the 24-h EC50 on Daphnia magna and a bioluminescence assay using Vibrio fischeri photobacteria. Fecal coliforms and physicochemical analyses such as total organic carbon (TOC), chloride, AOX, total suspended solids (TSS) and chemical oxygen demand (COD) were carried out. Wastewater samples highlighted considerable acute toxicity on D. magna and V. fischeri photobacteria. However, low most probable numbers (MPN), ranging from <3 to 2400 for 100 ml, were detected for fecal coliforms. Statistical analysis, with a confidence interval of 95%, gave a strong linear regression assessed with r=0.98 between AOX concentrations and EC50 (TU) on daphnia. The identification of an ideal concentration of NaOCl in disinfecting hospital wastewater, i.e. its non-observed effect concentration (NOEC) on algae and D. magna, seems to be a research issue that could facilitate the control of AOX toxicity effects on aquatic organisms. Therefore, it would be necessary to monitor the biocide properties of NaOCl on fecal coliforms at various doses and its toxicity effects on aquatic organisms.     

Fate of glutaraldehyde in hospital wastewater and combined effects of glutaraldehyde and surfactants on aquatic organisms

Glutaraldehyde (GA), an aliphatic dialdehyde disinfectant, and surfactants, one of the major components of detergents, are widely used in hospitals in order to eliminate pathogenic organisms causing nosocomial infectious diseases. After their use, disinfectants and surfactants reach the wastewater network together. The discharge of chemical compounds from hospital activities into wastewater is also a well-known problem, causing pollution of water resources and constituting an ecological risk for aquatic organisms. In this study, the chemistry and toxicology of GA and surfactant mixtures were reviewed in order to estimate their fate in aquatic ecosystems. Furthermore, their joint effects on aquatic organisms were experimentally assessed in the laboratory. A simple model of the additive joint action of toxicants was used to determine combined acute toxicity effects on the bacteria luminescence and Daphnia mobility of three mixtures containing GA at 1.5 x EC50 24 h [in mg/L] on Daphnia and anionic, cationic and nonionic surfactants at twice their critical micellar concentration (CMC). The mixture of GA and a cationic surfactant gave an EC50 30 min on Vibrio fischeri of 0.158%, with a concentration of 0.04 mg GA/L and 1.04 mg CTAB/L, which provided an additive action. The interaction between GA and an anionic surfactant on V. fischeri produced an antagonistic joint action with an EC50 30 min of 3.95%, containing 1.06 mg GA/L and 33.2 mg SDS/L. A synergistic action with an EC50 30 min of 8.4% on V. fischeri was observed for the mixture containing GA and a nonionic surfactant. Antagonistic interactions were observed for the joint action between GA and the surfactants studied on Daphnia. The mixture of GA and CTAB was more toxic (EC50 24 h=0.02%) than the two other mixtures (EC50 24 h GA+SDS=6%; EC50 24 h GA+TX 100=10%). This study provides new data on the toxicity of certain hospital pollutants entering the aquatic environment and detected in surface and groundwaters. It is necessary to study the joint effects of GA and surfactant mixtures following chronic and sublethal standard bioassays in order to estimate the contribution of the additive joint action models in assessing the environmental risk of hospital wastewater (HW).     

Prospects of utilization of sugar beet carbohydrates for biological hydrogen production in the EU

Hydrogen can be produced through dark anaerobic fermentation using carbohydrate-rich biomass, and through photofermentation using the organic acids produced from dark fermentation. Sugar beet is an ideal energy crop for fermentative production of hydrogen in the EU due to its environmental profile and its potential availability in the area. In this work, various aspects of cultivating sugar beet in the EU for biohydrogen were highlighted, with special focus on The Netherlands and Greece. Moreover, fermentation of sugar beet juice with Caldicellulosiruptor saccharolyticus at sucrose concentration 10 g/l was performed, and was found comparable to the fermentation on pure sucrose except that the hydrogen production was 10% higher on sugar beet juice. A conservative estimate of the annual hydrogen potential in the EU was made (300 × 10⁶ kg hydrogen), considering the utilization of sugar beet pulp in hydrogen production.     

Surface functionalization of natural hydroxyapatite by polymerization of β-cyclodextrin: application as electrode material for the electrochemical detection of Pb(II)

Environmental Science and Pollution Research - A composite material prepared by polymerization of β-cyclodextrin (β-CD) on the surface of natural hydroxyapatite using citric acid as cross...     

Women farmers’ perceived indices of occurrence and severity of observed climate extremes in rural Savannah,Ghana

Environment, Development and Sustainability - Climate extremes over the years have been a major concern for the globalized world. The hardest hit from these climate extremes are women farmers with...