Final seminar of REDUST was held in Viikki on 30th September. The seminar summed up information about the current situation of street dust research and air quality with participation from Finland, Sweden, Norway and Estonia.
Results of REDUST demonstrations and VTI’s research program were presented and the message seemed to be that dust binding with both CaCl2 and CMA is proven to be effective for short term street dust reduction.The amount of dust reduction depends on many factors, such as amount and concentration of the solution, temperature, humidity and spreading techniques. REDUST reported somewhat higher dust reductions for CaCl2 than for CMA in VTI’s tests.
Results on efficiency of street cleaning methods were more diverse. In REDUST demonstrations the street scrubber system with pressure washers was showing moderate reduction of street dust on washed sections. A curve of street scrubber efficiency and street dust load level has been created by combining REDUST results with previous research programmes in the Helsinki region, and street scrubber seems to be effective especially on very dirty streets. In VTI’s research at Stockholm dust reductions for street cleaning were not clearly visible, although the applied systems were noticeably removing dust material from the street environments. Reasons behind the diverse results may relate to effects of different road textures, which should be researched more in the future.
Air quality in the Helsinki region was compared with the Norwegian cities based on background information from presentations of Helsinki region environment authority and Norwegian institute for air research. Both Oslo and Helsinki regions showed mainly favourable trends in street dust (PM10) situation, although the approaches to tackle air quality issues have been somewhat different. In Oslo one of the cornerstones for air quality policy has been the taxation of studded tyres. This policy combined with speed limit reductions and improved maintenance led to significant reductions in PM10 levels in Oslo in recent years. In Helsinki studded tyres are still the dominant winter tyre type, but development in PM10 street dust situation has nevertheless been favourable since 2006. In Helsinki the frequency of spring days with high (>50 ug/m3 PM10) dust concentrations has decreased, which may indicate improved maintenance actions such as more frequent dust bindings are playing a role.
With all the accumulated information it is still not possible to clearly separate the contributions of seasonal factors, air quality policies and winter maintenance strategies on air pollutant concentrations in the air we breathe. This may only lead to one conclusion: more research is needed!
The presentations of final REDUST seminar can be found on the seminars section of REDUST website.