An empirically derived inorganic sea spray source function incorporating sea surface temperature
We have developed an inorganic sea spray source function that is based upon state-of-the-art measurements of sea spray aerosol production using a temperature-controlled plunging jet sea spray aerosol chamber. The size-resolved particle production was measured between 0.01 and 10 μm dry diameter. Particle production decreased non-linearly with increasing seawater temperature (between −1 and 30 °C) similar to previous findings. In addition, we observed that the particle effective radius, as well as the particle surface, particle volume and particle mass, increased with increasing seawater temperature due to increased production of particles with dry diameters greater than 1 μm. By combining these measurements with the volume of air entrained by the plunging jet we have determined the size-resolved particle flux as a function of air entrainment. Through the use of existing parameterisations of air entrainment as a function of wind speed, we were subsequently able to scale our laboratory measurements of particle production to wind speed. By scaling in this way we avoid some of the difficulties associated with defining the "white area" of the laboratory whitecap – a contentious issue when relating laboratory measurements of particle production to oceanic whitecaps using the more frequently applied whitecap method.
The here-derived inorganic sea spray source function was implemented in a Lagrangian particle dispersion model (FLEXPART – FLEXible PARTicle dispersion model). An estimated annual global flux of inorganic sea spray aerosol of 5.9 ± 0.2 Pg yr−1 was derived that is close to the median of estimates from the same model using a wide range of existing sea spray source functions. When using the source function derived here, the model also showed good skill in predicting measurements of Na+ concentration at a number of field sites further underlining the validity of our source function.
In a final step, the sensitivity of a large-scale model (NorESM – the Norwegian Earth System Model) to our new source function was tested. Compared to the previously implemented parameterisation, a clear decrease of sea spray aerosol number flux and increase in aerosol residence time was observed, especially over the Southern Ocean. At the same time an increase in aerosol optical depth due to an increase in the number of particles with optically relevant sizes was found. That there were noticeable regional differences may have important implications for aerosol optical properties and number concentrations, subsequently also affecting the indirect radiative forcing by non-sea spray anthropogenic aerosols.
Application of graphitic sorbent for online microextraction of drugs in human plasma samples
Isotope-Based Source Apportionment of EC Aerosol Particles during Winter High-Pollution Events at the Zeppelin Observatory, Svalbard
Black carbon (BC) aerosol particles contribute
to climate warming of the Arctic, yet both the sources and the
source-related effects are currently poorly constrained.
Bottom-up emission inventory (EI) approaches are challenged
for BC in general and the Arctic in particular. For example,
estimates from three different EI models on the fractional
contribution to BC from biomass burning (north of 60° N)
vary between 11% and 68%, each acknowledging large
uncertainties. Here we present the first dual-carbon isotope-
based (Δ14C and δ13C) source apportionment of elemental
carbon (EC), the mass-based correspondent to optically
defined BC, in the Arctic atmosphere. It targeted 14 high-
loading and high-pollution events during January through
March of 2009 at the Zeppelin Observatory (79° N; Svalbard,
Norway), with these representing one-third of the total sampling period that was yet responsible for three-quarters of the total EC loading. The top-down source-diagnostic 14C fingerprint constrained that 52 ± 15% (n = 12) of the EC stemmed from biomass burning. Including also two samples with 95% and 98% biomass contribution yield 57 ± 21% of EC from biomass burning. Significant variability in the stable carbon isotope signature indicated temporally shifting emissions between different fossil sources, likely including liquid fossil and gas flaring. Improved source constraints of Arctic BC both aids better understanding of effects and guides policy actions to mitigate emissions.
CRED: Criteria for reporting and evaluating ecotoxicity data
Predicted-no-effect concentrations (PNECs) and environmental quality standards (EQSs) are derived in a large number of legal frameworks worldwide. When deriving these safe concentrations, it is necessary to evaluate the reliability and relevance of ecotoxicity studies. Such evaluation is often subject to expert judgment, which may introduce bias and decrease consistency when risk assessors evaluate the same study. The Criteria for Reporting and Evaluating Ecotoxicity Data (CRED) project attempts to address this problem. It aims to improve the reproducibility, transparency, and consistency of reliability and relevance evaluations of aquatic ecotoxicity studies among regulatory frameworks, countries, institutes, and individual assessors. In the present study, the CRED evaluation method is presented. It includes a set of 20 reliability and 13 relevance criteria, accompanied by extensive guidance. Risk assessors who participated in the CRED ring test evaluated the CRED evaluation method to be more accurate, applicable, consistent, and transparent than the often-used Klimisch method. The CRED evaluation method is accompanied by reporting recommendations for aquatic ecotoxicity studies, with 50 specific criteria divided into 6 categories: general information, test design, test substance, test organism, exposure conditions, and statistical design and biological response. An ecotoxicity study in which all important information is reported is more likely to be considered for regulatory use, and proper reporting may also help in the peer-review process.
Aerosol transport over the Andes from the Amazon Basin to the remote Pacific Ocean: A multiyear CALIOP assessment
Six years (200702012) of data from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) satellite instrument were used to investigate the vertical distribution and transport of aerosols over the tropical South American continent and the southeast Pacific Ocean. The multiyear aerosol extinction assessment indicates that aerosols, mainly biomass burning particles emitted during the dry season in the Amazon Basin, are lifted in significant amounts over the Andes. The aerosols are mainly transported in the planetary boundary layer between the surface and 2 km altitude with an aerosol extinction maximum near the surface. During the transport toward the Andes, the aerosol extinction decreases at a rate of 0.02 km(-1) per kilometer of altitude likely due to dilution and deposition processes. Aerosols reaching the top of the Andes, at altitudes typically between 4 and 5 km, are entrained into the free troposphere (FT) over the southeast Pacific Ocean. A comparison between CALIOP observations and ERA-Interim reanalysis data indicates that during their long-range transport over the tropical Pacific Ocean, these aerosols are slowly transported toward the marine boundary layer by the large-scale subsidence at a rate of 0.4 cm s(-1). The observed vertical/horizontal transport ratio is 0.700.8 m km(-1) Continental aerosols linked to transport over the Andes can be traced on average over 4000 km away from the continent indicating an aerosol residence time of 809 days in the FT over the Pacific Ocean. The FT aerosol optical depth (AOD) above the Pacific Ocean near South American coast accounts on average for 6% and 25% of the total AOD during the season of low and high biomass burning, respectively. This result shows that, during the biomass burning season, continental aerosols largely influence the AOD over the remote southeast Pacific Ocean. Overall, FT AOD decrease exponentially with the distance to continental sources at a rate of about 10% per degree of longitude over the Pacific Ocean.
An approach for manganese biomonitoring using a manganese carrier switch in serum from transferrin to citrate at slightly elevated manganese concentration
After high-dose-short-term exposure (usually from occupational exposure) and even more under low-dose long term exposure (mainly environmental) manganese (Mn) biomonitoring is still problematic since these exposure scenarios are not necessarily reflected by a significant increase of total Mn in bloodor serum. Usually, Mn concentrations of exposed and unexposed persons overlap and individual differen-tiation is often not possible. In this paper Mn speciation on a large sample size (n = 180) was used in orderto be able to differentiate between highly Mn-exposed or low or unexposed individuals at low total Mn concentration in serum (Mn(S)). The whole sample set consisted of three subsets from Munich, Emilia-Romagna region in Italy and from Sweden. It turned out that also at low total Mn(S) concentrations achange in major Mn carriers in serum takes place from Mn-transferrin (Mn-Tf(S)) towards Mn-citrate(Mn-Cit(S)) with high statistical significance (p < 0.000002). This carrier switch from Mn-Tf(S) to Mn-Cit(S)was observed between Mn(S) concentrations of 1.5 g/L to ca. 1.7 g/L. Parallel to this carrier change,for sample donors from Munich where serum and cerebrospinal fluid were available, the concentrationof Mn beyond neural barriers – analysed as Mn in cerebrospinal fluid (Mn(C)) – positively correlates toMn-Cit(S) when Mn(S) concentration was above 1.7 g/L. The correlation between Mn-Cit(S) and Mn(C)reflects the facilitated Mn transport through neural barrier by means of Mn-citrate. Regional differencesin switch points from Mn-Tf(S) to Mn-Cit(S) were observed for the three sample subsets. It is currentlyunknown whether these differences are due to differences in location, occupation, health status or other aspects. Based on our results, Mn-Cit(S) determination was considered as a potential means for estimat-ing the Mn load in brain and CSF, i.e., it could be used as a biomarker for Mn beyond neural barrier.For a simpler Mn-Cit(S) determination than size exclusion chromatography inductively coupled plasmamass spectrometry (SEC-ICP-MS), ultrafiltration (UF) of serum samples was tested for suitability, the latter possibly being a preferred choice for routine occupational medicine laboratories. Our results revealed that UF could be an alternative if methodical prerequisites and limitations are carefully considered. These prerequisites were determined to be a thorough cleaning procedure at a minimum Mn(S) concentration>1.5 g/L, as at lower concentrations a wide scattering of the measured concentrations in comparison tothe standardized SEC-ICP-MS results were observed.
Determination of porphyrins in oral bacteria by liquid chromatography electrospray ionization tandem mass spectrometryDownload
Biofilms in the oral cavity can be visualized by fluorescence and a common assumption is that the endogenously produced porphyrins in certain bacteria give rise to this fluorescence. Porphyrin content in oral bacteria has been sparingly investigated, and non-selective detection techniques such as utilizing the Soret fluorescence band of porphyrins are often used. In the present study, a quantitative and selective method for the determination of porphyrins in oral bacteria has been developed and validated using high performance liquid chromatography-tandem mass spectrometry. Lysis of bacteria using Tris-EDTA buffer together with ultrasonication showed high microbial killing efficiency ≥99.98 %, and sample clean-up using C18-solid phase extraction resulted in low matrix effects ≤14 % for all analytes. Using this method, the porphyrin content was determined in the two oral pathogens Aggregatibacter actinomycetemcomitans and Porphyromonas gingivalis, as well as for baker’s yeast, Saccharomyces cerevisiae. Uroporphyrin, 7-carboxylporphyrin, 6-carboxylporphyrin, coproporphyrin, and protoporphyrin IX were identified in the investigated microorganisms, and it was shown that the porphyrin profile differs between the two bacteria, as well as for S. cerevisiae. To our knowledge, this is the first time the porphyrin profile has been determined for the bacterium A. actinomycetemcomitans.