Biodegradation of oil spill dispersant surfactants in cold seawater

While biodegradation of chemically dispersed oil has been well documented, only a few studies have focused on the degradation of the dispersant compounds themselves. The objective of this study was to determine the biodegradation of dispersant surfactants in cold seawater, relevant for deep sea or Arctic conditions. Biotransformation of the surfactants dioctyl-sodium sulfosuccinate (DOSS), Tween 80, Tween 85, and α/β-ethylhexylsulfosuccinate (EHSS, expected DOSS hydrolysis product) in the commercial dispersants Corexit 9500, Dasic Slickgone NS and Finasol OSR52 were determined. The biotransformation studies of the surfactants were performed in natural seawater at 5 °C over a period of 54 days without oil present. The surfactants were tested at concentrations of 1, 5, and 50 mg/L, the lower concentration being as close as possible to expected field concentrations. Experiments with dispersants concentrations of 1 mg/L resulted in rapid biotransformation of Tween 80 and Tween 85, with depletion after 8 days, while DOSS showed rapid biotransformation after a lag period of 16 days. The degradation half-life of DOSS increased from 4.1 days to >500 days as Corexit 9500 concentrations went from 1 mg/L to 50 mg/L, emphasizing the importance of performing experiments at dispersant concentrations as close as possible to environmentally relevant concentrations. EHSS showed limited degradation compared to other surfactants. This study shows that the surfactants DOSS, Tween 80 and Tween 85 in the three chemical dispersants studied are biodegradable in cold seawater, particularly in environmentally relevant concentrationsacceptedVersio

Tuulessa - I vinden

Ønsket om å formidle forskning av kvensk kulturarv på en ny måte har resultert i vandreutstillinga Tuulessa – I vinden

Do we need the users voice : An empirical research example comparing views of service providers and ex-prisoners : Implications for practice

User involvement in service development is seen as important to the credibility of these interventions but involving prisoners or ex-prisoners in this process can be problematic because of the vulnerability of this group as well as security issues. Questions arise as whether front line workers can instead reflect the perspectives of their clients accurately during service development events. Further, we query whether an alignment of perspectives is important for effective professional-prisoner relationships and offender self-efficacy when engaging in rehabilitation and reintegration programmes. To explore these questions, this chapter, in a case study third sector mentorship organisation, compares and contrasts the views of ex-prisoners and their mentors. Q methodology is employed to make this comparison. We find that mentors perspectives are most in tune with the most pessimistic perspectives of their clients: the most lonely, indigent and ill group of the exoffenders they work with. They do not share the optimistic views that characterise other groups of offenders in receipt of their service. The chapter explores the implications of these different views for exoffenders, their mentors and the participation of the offender in service innovation

Stratégies de développement régional. Une approche spatiale de l'économie rurale de la zone de concentration. Rapport de mission du 3 au 14 novembre 1992

Cette mission avait pour objectif la définition de stratégies de développement à partir des données accumulées par la Cellule Recherche-Développement. Le rapport présent un zonage en 7 unités. Ce zonage est basé sur des critères liés aux ressources naturelles, à la localisation par rapport à N'Djamena et aux systèmes de production existants. Les 7 unités sont regroupées autour de 3 logiques économiques : - une logique d'accumulation traditionnelle, - une logique d'accumulation par injection de capital, - une logique de surexploitation des ressources naturelles. Après avoir analysé pour chaque système technique, ses marges de progrès et les contraintes principales, le rapport propose une régionalisation des action