The seasonality of chemical persistence in a Swedish lake by benchmarking
Chemicals with high persistence (i.e. long degradation half-lives) could pose high risks to living organisms and humans and be subject to long-range transport. It is challenging to measure persistence directly in the field due to lack of appropriate methods. Chemical benchmarking as an alternative method was evaluated to have potential to assess the persistence in real aquatic environment . It has been further applied in a Swedish lake (Norra Bergundasjön) for measuring the persistence of a group of pharmaceuticals and compared (and validated) with traditional mass balance approach . The degradation of a chemical in a lake could be influenced by several factors including temperature, sunlight, pH and nature of the degrading microorganisms, which may vary in time and space. So in this study benchmarking was used to study the temporal variation of persistence of 7 pharmaceuticals in another Swedish lake (Boren) that receives the discharge from a WWTP and inflowing water from Vättern. The sampling campaigns were conducted in late spring, late autumn and winter of 2013. Acesulfame K (an artificial sweetener) was used as the benchmark chemical. The results show that the strongest seasonal variability was between spring and autumn. The half-lives of 5 chemicals in spring were shorter than in autumn, mainly because of lower temperature and weak irradiation in autumn. The half-lives of chemicals in Boren were also compared with that in Norra Bergundasjön. This could be explained by the difference in the nutrient status and pH in these two Swedish lakes. Benchmarking did open a new door to measure persistence in a broader range than before and more opportunities to study the spatial and temporal variability of persistence in the real environment.
Characterization of a hemoglobin adduct from ethyl vinyl ketone detected in human blood samples
Single-Particle Time-of-Flight Mass Spectrometry Utilizing a Femtosecond Desorption and Ionization Laser
Single-particle time-of-flight mass spectrometry has now been used since the 1990s to determine particle-to-particle variability and internal mixing state. Instruments commonly use 193 nm excimer or 266 nm frequency-quadrupled Nd:YAG lasers to ablate and ionize particles in a single step. We describe the use of a femtosecond laser system (800 nm wavelength, 100 fs pulse duration) in combination with an existing single-particle time-of-flight mass spectrometer. The goal of this project was to determine the suitability of a femtosecond laser for single-particle studies via direct comparison to the excimer laser (193 nm wavelength, similar to 10 ns pulse duration) usually used with the instrument. Laser power, frequency, and polarization were varied to determine the effect on mass spectra. Atmospherically relevant materials that are often used in laboratory studies, ammonium nitrate and sodium chloride, were used for the aerosol. Detection of trace amounts of a heavy metal, lead, in an ammonium nitrate matrix was also investigated. The femtosecond ionization had a large air background not present with the 193 nm excimer and produced more multiply charged ions. Overall, we find that femtosecond laser ablation and ionization of aerosol particles is not radically different than that provided by a 193 nm excimer.
Fluorinated alternatives to long-chain PFASs: What we know about them and proposals for how they should be managed and regulated
A strategic screening approach to identify transformation products of emerging organic micropollutants along rivers
The C-20 highly branched isoprenoid biomarker – A new diatom-sourced proxy for summer trophic conditions?
The exact biological source of the C-20 highly branched isoprenoid (HBI) present in sediments from aquatic systems is unclear. We therefore examined the relationship between the distribution of fossil diatoms and the concentration of the C-20 HBI in a Late Glacial sedimentary record from the Hasseldala Port paleolake in southern Sweden. Using Bayesian multiple linear regression analysis, we show that its concentration is linked primarily to the production of the diatom taxon Gomphonema acuminatum, which accounts for the largest proportion of the temporal variability in the biomarker. By analogy with modern observations, we argue that an increasing amount of Gomphonema acuminatum biomass in our sedimentary record reflects increasing oligotrophy in the paleolake during the summer growing season, especially at times defined by subdued hydrologic flow. Our conclusions are corroborated by the delta C-13 composition of the C-20 HBI biomarker, which points to a negative photosynthetic fractionation between atmospheric CO2 and the pool of dissolved inorganic carbon during diatom bloom, a distinct phenomenon at times of inhibited hydrological flow. Accordingly, we suggest that the C-20 HBI biomarker can be effectively used to reconstruct the trophic state of the paleolake at Hasseldala Port, while its stable isotope composition can provide physicochemical information about the lake conditions during the dry summer season.Moreover, we note that the major hydrological shifts recorded in the Gomphonema acuminatum-C-20 HBI stratigraphy do not coincide with the pollen zone boundaries. We thus infer that aquatic and terrestrial environmental responses to climate change are substantially decoupled through the hydrological system, which highlights the necessity for multi-proxy investigations to decipher past climate events. (C) 2015 Elsevier Ltd. All rights reserved.
Performance of the CalTOX fate and exposure model in a case study for a dioxin-contaminated site
Particulate matter, air quality and climate: lessons learned and future needs
The literature on atmospheric particulate matter (PM), or atmospheric aerosol, has increased enormously over the last 2 decades and amounts now to some 1500-2000 papers per year in the refereed literature. This is in part due to the enormous advances in measurement technologies, which have allowed for an increasingly accurate understanding of the chemical composition and of the physical properties of atmospheric particles and of their processes in the atmosphere. The growing scientific interest in atmospheric aerosol particles is due to their high importance for environmental policy. In fact, particulate matter constitutes one of the most challenging problems both for air quality and for climate change policies. In this context, this paper reviews the most recent results within the atmospheric aerosol sciences and the policy needs, which have driven much of the increase in monitoring and mechanistic research over the last 2 decades.The synthesis reveals many new processes and developments in the science underpinning climate-aerosol interactions and effects of PM on human health and the environment. However, while airborne particulate matter is responsible for globally important influences on premature human mortality, we still do not know the relative importance of the different chemical components of PM for these effects. Likewise, the magnitude of the overall effects of PM on climate remains highly uncertain. Despite the uncertainty there are many things that could be done to mitigate local and global problems of atmospheric PM. Recent analyses have shown that reducing black carbon (BC) emissions, using known control measures, would reduce global warming and delay the time when anthropogenic effects on global temperature would exceed 2 degrees C. Likewise, cost-effective control measures on ammonia, an important agricultural precursor gas for secondary inorganic aerosols (SIA), would reduce regional eutrophication and PM concentrations in large areas of Europe, China and the USA. Thus, there is much that could be done to reduce the effects of atmospheric PM on the climate and the health of the environment and the human population.A prioritized list of actions to mitigate the full range of effects of PM is currently undeliverable due to shortcomings in the knowledge of aerosol science; among the shortcomings, the roles of PM in global climate and the relative roles of different PM precursor sources and their response to climate and land use change over the remaining decades of this century are prominent. In any case, the evidence from this paper strongly advocates for an integrated approach to air quality and climate policies.
Top-down constraints on atmospheric mercury emissions and implications for global biogeochemical cycling
We perform global-scale inverse modeling to constrain present-day atmospheric mercury emissions and relevant physio-chemical parameters in the GEOS-Chem chemical transport model. We use Bayesian inversion methods combining simulations with
5 GEOS-Chem and ground-based Hg0 observations from regional monitoring networks and individual sites in recent years. Using optimized emissions/parameters, GEOS-Chem better reproduces these ground-based observations, and also matches regional over-water Hg0 and wet deposition measurements. The optimized global mercury emission to the atmosphere is 5.8 Gg/yr-1. The ocean accounts for 3.2 Gg/yr-1 (55% of 10 the total), and the terrestrial ecosystem is neither a net source nor a net sink of Hg0. The optimized Asian anthropogenic emission of Hg0 (gas elemental mercury) is 650– 1770 Mg/yr-1, higher than its bottom-up estimates (550–800 Mg/yr-1). The ocean parameter inversions suggest that dark oxidation of aqueous elemental mercury is faster, and less mercury is removed from the mixed layer through particle sinking, when compared with current simulations. Parameter changes affect the simulated global ocean mercury budget, particularly mass exchange between the mixed layer and subsurface waters. Based on our inversion results, we re-evaluate the long-term global biogeo- chemical cycle of mercury, and show that legacy mercury becomes more likely to reside in the terrestrial ecosystem than in the ocean. We estimate that primary anthropogenic 20 mercury contributes up to 23 % of present-day atmospheric deposition.