Publications

In the present study a recently developed benthic flow‐through chamber was used to assess the sediment‐to‐water
flux of polycyclic aromatic hydrocarbons (PAHs) at 4 sites on the Swedish Baltic Sea coast. The flow‐through chamber allows for assessment of the potential effect of bioturbation on the sediment‐to‐water flux of hydrophobic organic contaminants. The sediments at the 4 investigated sites have both varying contamination degree and densities of bioturbating organisms. The flux of individual PAHs measured with the flow‐through chamber ranged between 21 and 510, 11 and 370, 3 and 9700, and 62 and 2300 ngm–2 d–1 for the 4 sites. To assess the potential effect of bioturbation on the sediment‐to‐water flux, 3
flow‐through and closed chambers were deployed in parallel at each site. The activity of benthic organisms is attenuated or halted because of depletion of oxygen in closed benthic chambers. Therefore, the discrepancy in flux measured with the 2 different chamber designs was used as an indication of a possible effect of bioturbation. A potential effect of bioturbation on the sediment‐to‐water flux by a factor of 3 to 55 was observed at sites with a high density of bioturbating organisms (e.g., Marenzelleria spp., Monoporeia affinis, and Macoma balthica of approximately 860–1200 individuals m–2) but not at the site with much lower organism density (<200 individuals m–2). One site had a high organism density and a low potential effect of bioturbation, which we hypothesize to be caused by the dominance of oligochaetes/polychaetes at this site because worms (Marenzelleria spp.) reach deeper into the sediment than native crustaceans and mollusks.

The traffic microenvironment has been shown to be a major contributor to the total personal exposure of black carbon (BC), and is key to local actions aiming at reducing health risks associated with such exposure. The main aim of the study was to get a better understanding of the determinants of traffic-related personal exposure to BC in an urban environment.

Personal exposure to ambient levels of BC was monitored while walking, cycling and traveling by bus or car along four streets and while cycling alternative routes simultaneously. Monitoring was performed during morning and afternoon peak hours and at midday, with a portable aethalometer recording one-minute mean values. In all, >4000 unique travel passages were performed. Stepwise Linear Regression was used to assess predictors to personal exposure levels of BC.

The personal BC concentration ranged 0.03–37 μg/m3. The average concentrations were lowest while walking (1.7 μg/m3) and highest traveling by bus (2.7 μg/m3). However, only 22% of the variability could be explained by travel mode, urban background BC and wind speed. BC concentrations measured inside a car were on average 33% lower than measured simultaneously outside the car. Choosing an alternative bicycle route with less traffic resulted in up to 1.4 μg/m3 lower personal exposure concentrations.

In conclusion, traveling by bus rendered the highest personal BC concentrations. But when taking travel time and inhalation rate into account, the travel-related exposure dose was predicted to be highest during walking and cycling. It is however probable that the benefits from physical activity outweigh health risks associated with this higher exposure dose.

It is clear that road traffic makes an important contribution to personal exposure to BC regardless of mode of intra-urban transport. Our data suggest that commuting along routes with lower BC levels would substantially decrease commuter's exposure.

In this study, the effects on daily mortality in Stockholm associated with short-term exposure to ultrafine particles (measured as number of particles with a diameter larger than 4 nm, PNC4), black carbon (BC) and coarse particles (PM2.5–10) have been compared with the effects from more common traffic-pollution indicators (PM10, PM2.5 and NO2) and O3 during the period 2000–2016. Air pollution exposure was estimated from measurements at a 20 m high building in central Stockholm. The associations between daily mortality lagged up to two days (lag 02) and the different air pollutants were modelled by using Poisson regression. The pollutants with the strongest indications of an independent effect on daily mortality were O3, PM2.5–10 and PM10. In the single-pollutant model, an interquartile range (IQR) increase in O3 was associated with an increase in daily mortality of 2.0% (95% CI: 1.1–3.0) for lag 01 and 1.9% (95% CI: 1.0–2.9) for lag 02. An IQR increase in PM2.5–10 was associated with an increase in daily mortality of 0.8% (95% CI: 0.1–1.5) for lag 01 and 1.1% (95% CI: 0.4–1.8) for lag 02. PM10 was associated with a significant increase only at lag 02, with 0.8% (95% CI: 0.08–1.4) increase in daily mortality associated with an IQR increase in the concentration. NO2 exhibits negative associations with mortality. The significant excess risk associated with O3 remained significant in two-pollutant models after adjustments for PM2.5–10, BC and NO2. The significant excess risk associated with PM2.5–10 remained significant in a two-pollutant model after adjustment for NO2. The significantly negative associations for NO2 remained significant in two-pollutant models after adjustments for PM2.5–10, O3 and BC. A potential reason for these findings, where statistically significant excess risks were found for O3, PM2.5–10 and PM10, but not for NO2, PM2.5, PNC4 and BC, is behavioral factors that lead to misclassification in the exposure. The concentrations of O3 and PM2.5–10 are in general highest during sunny and dry days during the spring, when exposure to outdoor air tend to increase, while the opposite applies to NO2, PNC4 and BC, with the highest concentrations during the short winter days with cold weather, when people are less exposed to outdoor air.

Perfluoroalkyl acids (PFAAs) are persistent organic pollutants found throughout the world's oceans. Previous
research suggests that long-range atmospheric transport of these substances may be substantial. However,
it remains unclear what the main sources of PFAAs to the atmosphere are. We have used a laboratory sea
spray chamber to study water-to-air transfer of 11 PFAAs via sea spray aerosol (SSA). We observed significant
enrichment of all PFAAs relative to sodium in the SSA generated. The highest enrichment was observed in
aerosols with aerodynamic diameter < 1.6 mm, which had aerosol PFAA concentrations up to 62 000 times
higher than the PFAA water concentrations in the chamber. In surface microlayer samples collected from
the sea spray chamber, the enrichment of the substances investigated was orders of magnitude smaller
than the enrichment observed in the aerosols. In experiments with mixtures of structural isomers,
a lower contribution of branched PFAA isomers was observed in the surface microlayer compared to the
bulk water. However, no clear trend was observed in the comparison of structural isomers in SSA and
bulk water. Using the measured enrichment factors of perfluorooctanoic acid and perfluorooctane
sulfonic acid versus sodium we have estimated global annual emissions of these substances to the
atmosphere via SSA as well as their global annual deposition to land areas. Our experiments suggest that
SSA may currently be an important source of these substances to the atmosphere and, over certain
areas, to terrestrial environments.