Found: 6484 publications , showing page 541 of 541
A Review of More than 20 Years of Aerosol Observation at the High Altitude Research Station Jungfraujoch, Switzerland (3580 m asl)
| Aerosol Air Qual. Res.
Aerosol chemical properties
Aerosol physical properties
Among the worldwide existing long-term aerosol monitoring sites, the Jungfraujoch (JFJ) belongs to the category where both free tropospheric (FT) conditions and influence from planetary boundary layer (PBL) injections can be observed. Thus, it is possible to characterize free tropospheric aerosol as well as the effects of vertical transport of more polluted air from the PBL. This paper summarizes the current knowledge of the key properties for the JFJ aerosol, gained from the large number of in-situ studies from more than 20 years of aerosol measurements at the site. This includes physical, chemical and optical aerosol properties as well as aerosol-cloud interactions and cloud characteristics. It is illustrated that the aerosol size distribution and the aerosol chemical composition are fairly constant in time due to the long distance from aerosol sources, and that many climate relevant aerosol properties can be derived due to this behavior.
XRF measurements of tin, copper and zinc in antifouling paints coated on leisure boats
Tributyltin (TBT) and other organotin compounds have been restricted for use on leisure boats since 1989 in the EU. Nonetheless, release of TBT is observed from leisure boats during hull maintenance work, such as pressure hosing. In this work, we used a handheld X-ray Fluorescence analyser (XRF) calibrated for antifouling paint matrixes to measure tin, copper and zinc in antifouling paints coated on leisure boats in Sweden. Our results show that over 10% of the leisure boats (n = 686) contain >400 μg/cm2 of tin in their antifouling coatings. For comparison, one layer (40 μm dry film) of a TBT-paint equals ≈ 800 μg Sn/cm2. To our knowledge, tin has never been used in other forms than organotin (OT) in antifouling paints. Thus, even though the XRF analysis does not provide any information on the speciation of tin, the high concentrations indicate that these leisure boats still have OT coatings present on their hull. On several leisure boats we performed additional XRF measurements by progressively scraping off the top coatings and analysing each underlying layer. The XRF data show that when tin is detected, it is most likely present in coatings close to the hull with several layers of other coatings on top. Thus, leaching of OT compounds from the hull into the water is presumed to be negligible. The risk for environmental impacts arises during maintenance work such as scraping, blasting and high pressure hosing activities. The data also show that many boat owners apply excessive paint layers when following paint manufacturers recommendations. Moreover, high loads of copper were detected even on boats sailing in freshwater, despite the more than 20 year old ban, which poses an environmental risk that has not been addressed until now.
Human exposure, hazard and risk of alternative plasticizers to phthalate esters
| Sci. Total Environ.
Human exposure to perfluoroalkyl substances (PFASs)
| ACES, SU
Since the 1950’s, the production of industrial chemicals has steadily increased in order to fulfil the demands of modern society. At the same time, the increasing awareness that some chemicals can be harmful to humans underscores the need for accurately assessing the risks of potentially harmful substances and controlling their use and production. Since 2000, per- and polyfluorinated substances (PFASs) have gained attention as emerging Persistent Organic Pollutants (POPs). Despite the numerous scientific studies on PFASs, there are still considerable knowledge gaps which prevent a comprehensive risk assessment of this substance class. Indeed, even though phaseout actions have been carried out for two PFASs of high concern (i.e. perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA)), exposure to both substances is still occurring and the sources are not fully understood. The phase-out actions have also led to numerous fluorinated alternatives entering the market, for which very little information on hazard properties is available. The present licentiate thesis aims to partly fulfill these knowledge gaps in two different studies:
assesses the indirect exposure (i.e. uptake of precursors, here 8:2 fluorotelomer alcohol (8:2 FTOH), further metabolized into PFOA) as a potential ongoing exposure source to PFOA. In this respect, the metabolism yield, defined as the fraction of total 8:2 FTOH in the organism converted into PFOA, was estimated using a one box pharmacokinetic model and biomonitoring data of six ski wax technicians occupationally exposed to high PFOA and 8:2 FTOH concentration. An average metabolism yield of 0.19% was estimated.
focus on the prediction of the physico-chemical properties and environmental fate of fluorinated alternatives as a first step in the exposure assessment. The model simulations demonstrate that fluorinated alternatives are not significantly different from their predecessors when it comes to the octanol-water (KOW), the air-water (KAW) partition coefficients, the persistence and long-range transport in the environment.
The wide range of substances coupled with different physico-chemical properties make the risk assessment of the PFASs family particularly complicated. Nevertheless, this thesis contributes to improve the understanding of human exposure to PFASs when it comes to its kinetics and its sources. Furthermore, it highlights the urgent need of experimental work on potentially problematic fluorinated alternatives.