Challenges in constraining anthropogenic aerosol effects on cloud radiative forcing using present-day spatiotemporal variability
A large number of processes are involved in the chain from emissions of aerosol precursor gases and primary particles to impacts on cloud radiative forcing. Those processes are manifest in a number of relationships that can be expressed as factors dlnX/dlnY driving aerosol effects on cloud radiative forcing. These factors include the relationships between cloud condensation nuclei (CCN) concentration and emissions, droplet number and CCN concentration, cloud fraction and droplet number, cloud optical depth and droplet number, and cloud radiative forcing and cloud optical depth. The relationship between cloud optical depth and droplet number can be further decomposed into the sum of two terms involving the relationship of droplet effective radius and cloud liquid water path with droplet number. These relationships can be constrained using observations of recent spatial and temporal variability of these quantities. However, we are most interested in the radiative forcing since the preindustrial era. Because few relevant measurements are available from that era, relationships from recent variability have been assumed to be applicable to the preindustrial to present-day change. Our analysis of Aerosol Comparisons between Observations and Models (AeroCom) model simulations suggests that estimates of relationships from recent variability are poor constraints on relationships from anthropogenic change for some terms, with even the sign of some relationships differing in many regions. Proxies connecting recent spatial/temporal variability to anthropogenic change, or sustained measurements in regions where emissions have changed, are needed to constrain estimates of anthropogenic aerosol impacts on cloud radiative forcing.
Madrid Statement on Poly- and Perfluoroalkyl Substances (PFASs)
14th congress of combustion by-products and their health effects—origin, fate, and health effects of combustion-related air pollutants in the coming era of bio-based energy sources
The 14th International Congress on Combustion By-Products and Their Health Effects was held in Umeå, Sweden from June 14th to 17th, 2015. The Congress, mainly sponsored by the National Institute of Environmental Health Sciences Superfund Research Program and the Swedish Research Council for Environment, Agricultural Sciences and Spatial Planning, focused on the “Origin, fate and health effects of combustion-related air pollutants in the coming era of bio-based energy sources”. The international delegates included academic and government researchers, engineers, scientists, policymakers and representatives of industrial partners. The Congress provided a unique forum for the discussion of scientific advances in this research area since it addressed in combination the health-related issues and the environmental implications of combustion by-products. The scientific outcomes of the Congress included the consensus opinions that: (a) there is a correlation between human exposure to particulate matter and increased cardiac and respiratory morbidity and mortality; (b) because currently available data does not support the assessment of differences in health outcomes between biomass smoke and other particulates in outdoor air, the potential human health and environmental impacts of emerging air-pollution sources must be addressed. Assessment will require the development of new approaches to characterize combustion emissions through advanced sampling and analytical methods. The Congress also concluded the need for better and more sustainable e-waste management and improved policies, usage and disposal methods for materials containing flame retardants.
Identifying chemicals that are planetary boundary threats-
A Review of More than 20 Years of Aerosol Observation at the High Altitude Research Station Jungfraujoch, Switzerland (3580 m asl)
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 to perfluoroalkyl substances (PFASs)
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.