Overview
Since 2011, intensified efforts are made to reduce levels of PM10 in Stockholm, where the problems are extensive.
The objective of the study was to measure the level of PM10 in Stockholm in the winter season 2013 - 2014.
Results
The lowest PM10 levels since records began in Stockholm, were measured during the season and the limit values for the environmental quality standard is managed by a wide margin, which at least partially can be attributed to the intensified measures.
The winter was unusually mild and snow-free and this has probably contributed to that, the typically large quantities of road dust that accumulates on the road surface in winter were able to leave the system through suspension, cleaning and drainage without high particulate levels resulting. During dry periods, frequent dust binding has helped to suppress high PM10 levels. The usually sharp PM10 peak in spring did not appear to the same extent as previous years.
The block-wise CMA treatment was shown to provide additional reducing effect on PM10 levels, while the CMA + KF treatment did not appear to have any impact. The measurements of the road dust load show the same seasonal fluctuations as in previous years, with large amounts during winter and early spring and lower in fall and late spring.
All streets, except Hornsgatan, show a gradual decrease of road dust load over the three seasons with available data. The proportion of particles smaller than 10 microns in the dust increases from autumn to winter and decreases again in the spring. The organic proportion varies between 10 and 20 per cent by weight of DL180 and also exhibit a seasonal variation, where the proportion is higher in autumn and lowest in early spring.