Sorption of europium on a goethite surface: influence of background electrolyte

An experimental and theoretical study of Eu(III) sorption on goethite surface was performed in the presence of different background electrolytes (NaCl, NaNO3, KNO3). Results were described using a simple surface complexation, the double-layer model (DLM), and calculations were performed using either Fiteql3.2 or Jchess codes. The surface acidity constants and sites density were first determined by potentiometric titrations. The influence of electrolyte ions on the value of point of zero charge was studied by both potentiometric and electrokinetic measurements in order to assess their possible retention on goethite. The sorption of Eu(III) was then investigated by the batch method, in the three background electrolytes, as a function of pH. The presence of electrolyte ions was found to decrease the immobilization of Eu on goethite. Sorption results were modelled considering ternary surface complexes (goethite surface/europium/electrolyte ions).     

Experimental ecology of the temperate scleractinian coral Astrangia danae I. Partition of respiration,photosynthesis and calcification between host and symbionts

Calcification, photosynthesis and respiration of the scleractinian coral Astrangia danae were calculated from the changes in total alkalinity, pH, calculated total CO₂, and oxygen concentration produced by colonies incubated in glass jars. A correction for changes in ammonia, nitrate and nitrite was taken into account and the method evaluated. The fluxes of oxygen and CO₂ were highly correlated (r=0.99). The statistical error of alkalinity determinations was less than 10% of the changes observed in the slowest calcifying samples. Metabolism of polyparium alone was estimated by difference after removal of tissue and reincubation of bare corallum. Zooxanthellae concentration in the polyps was obtained from cell counts made on homogenates of polyp tissue. The calculated photosynthetic rate of the zooxanthellae in vivo was 25 mol O₂ (10⁸ cell)^-1 h^-1 at a light intensity of 120 Ein m^-2 s^-1. In corals having 0.5x10⁹ zooxanthellae/dm² of colony area up to 8% of the total photosynthesis was attributed to the corallum microcosm. Polyp respiration, photosynthesis, and CaCO₃ uptake rates were all much higher than rates previously reported from A. danae, apparently because in these experiments the organisms were better fed. This increased photosynthesis in turn enhanced calcification still further. The symbiosis therefore appears to provide a growth advantage even to fed corals, under the conditions of these experiments.     

An Analysis of the Daily Radial Activity of 7 Boreal Tree Species, Northwestern Quebec

In the `Des Vieux Arbres' ecological reserve situated within northwestern Québec, 40 band dendrometers were installedon 7 of the major boreal tree species. The late Spring–early Summer daily radial activity registered in 1997 was related todaily weather variables. For each tree species, the daily mean i) cumulative radial increment and ii) radial activity indexedseries obtained by first-difference standardization were analyzed. The results indicate the existence of strong similarities among the 7 species. All showed strong synchronousfluctuations in radius during late winter and early spring. Thisperiod ended with a short but sharp increase in radial increments that marked the passage of water into the stem. Thisinitial swelling, less obvious in Pinus species was followed by a prolonged period of little change in radial activity. Meteorological data indicated that air temperature waspositively related to stem swelling during the late winter–earlyspring period. Both air and soil temperatures became negatively related to radial expansion once the passage of water has occurred in the stem. Starting in early June, all species registered a sustained increase in radial increments possiblyassociated with active cell division. After this, radial expansion was negatively related to air temperature and positively to rainfall.     

Psychosocial risks in small enterprises: the mediating role of perceived working conditions in the relationship between enterprise size and workers’ anxious or depressive episodes

Purpose. The relationship between enterprise size and psychosocial working conditions has received little attention so far but some findings suggest that conditions are more favorable in small enterprises. This could have a positive impact on workers’ mental health. The objective of this study was to test the mediating effect of perceived working conditions in the relationship between enterprise size and anxious or depressive episodes. Methods. Data from the 2010 SUMER – Surveillance Médicale des Expositions aux Risques professionnels (French periodical cross-sectional survey) were analyzed; N?=?31,420 for the present study. Anxious or depressive episodes were measured with the hospital anxiety and depression scale and the perceived working conditions were psychological demand, decision latitude and social support as assessed with Karasek's job content questionnaire. The indirect effect was tested according to the method proposed by Preacher and Hayes. Results. In a multivariate logistic regression, the risk of anxious or depressive episodes was found to be lower in micro enterprises (2–9 employees). Formal tests pointed to a significant indirect effect of enterprise size on mental health through perceived working conditions, with a larger effect for psychological demand. Conclusion. This study highlights perceived working conditions as an explanation of the effects of enterprise size.     

Local policies for reducing the ecological impact of households: the case study of a suburban area in France

Since Rio, governments have increased measures to promote sustainable household consumption, but this has induced limited changes in consumers’ daily practices. This article argues that one of the reasons behind the poor efficiency of these policies is the low level of consideration granted to local decision-making. The article discusses the results of a study which aims at better ascertaining the practices and representations of local government leaders in promoting sustainable development in households. We shall analyse the motivations, obstacles, interaction of players, communication and action plans associated with promoting sustainable development, in which individual will and effort are the keywords. The results obtained show how important it is to introduce better management systems for information and resource exchange between the different institutions involved. The study was carried out in a suburban area of south-west France counting 71 small towns and villages, characteristic of the spatial dynamics triggered by the global phenomenon of urbanisation.     

Associations between urinary cadmium levels,blood pressure,and hypertension: the ESTEBAN survey

Environmental Science and Pollution Research - Cadmium is inconsistently associated with blood pressure (BP) and hypertension. Our study focuses to understand the association between urinary...     

Extraction of Co,Ni, Cu,Zn and Cd ions using 2-aminophenylaminopropylpolysiloxane

Insoluble porous solid functionalized ligand system bearing 2-aminophenylaminopropyl chelating ligand of the general formula P–(CH₂)₃NH–(C₆H₄)–NH₂ was prepared via the sol–gel process, where P represents [Si–O] _n polysiloxane network. First, the 2-aminophenylaminopropylsilane agent was prepared by substitution reaction between 3-chloropropyltrimethoxysilane and 1,2-phenylenediamine, followed by hydrolytic polycondensation between 2-aminophenylaminopropylsilane agent and tetraethylorthosilicate(TEOS). The immobilized 2-aminophenylaminopropylpolysiloxane P–(CH₂)₃NH–(C₆H₄)–NH₂(P–AphA) was characterized by ¹³C NMR, XPS, and FTIR. The results showed that 1,2-phenylenediamine groups were introduced onto polysiloxane network. The functionalized ligand system exhibits 90–100% metal uptake capacity for all metal ions except Cd²⁺. The elemental analysis data and the metal uptake capacities of the immobilized ligand system suggest that over than 90% ligand sites were involved in coordination with metal ions except that of cadmium forming 1:1 metal to ligand ratio complexes.     

Operator-splitting errors in coupled reactive transport codes for transient variably saturated flow and contaminant transport in layered soil profiles

One possible way of integrating subsurface flow and transport processes with (bio)geochemical reactions is to couple by means of an operator-splitting approach two completely separate codes, one for variably-saturated flow and solute transport and one for equilibrium and kinetic biogeochemical reactions. This paper evaluates the accuracy of the operator-splitting approach for multicomponent systems for typical soil environmental problems involving transient atmospheric boundary conditions (precipitation, evapotranspiration) and layered soil profiles. The recently developed HP1 code was used to solve the coupled transport and chemical equations. For steady-state flow conditions, the accuracy was found to be mainly a function of the adopted spatial discretization and to a lesser extent of the temporal discretization. For transient flow situations, the accuracy depended in a complex manner on grid discretization, time stepping and the main flow conditions (infiltration versus evaporation). Whereas a finer grid size reduced the numerical errors during steady-state flow or the main infiltration periods, the errors sometimes slightly increased (generally less than 50%) when a finer grid size was used during periods with a high evapotranspiration demand (leading to high pressure head gradients near the soil surface). This indicates that operator-splitting errors are most significant during periods with high evaporative boundary conditions. The operator-splitting errors could be decreased by constraining the time step using the performance index (the product of the grid Peclet and Courant numbers) during infiltration, or the maximum time step during evapotranspiration. Several test problems were used to provide guidance for optimal spatial and temporal discretization.