B.8 Applicability of selected measures from Northern to Southern Europe
The focus of the research has been to quantify the efficacy of the mitigation measures, where possible. The original aim was to review air quality action plans, but these rarely provide sufficiently detailed information on the effects of measures. More focus has therefore been on reviewing both academic and municipal studies that have attempted to identify the impacts of individual measures. Often the impacts are small compared to the changes in air quality due to the weather, making quantification difficult.
For each report a literature search using the University of Birmingham’s on-line library search facility, Google and Google Scholar has been undertaken using appropriate search terms. The reports have drawn on a variety of sources including academic, municipal and industry studies, other LIFE/LIFE+ projects, AIRUSE partners, and personal communication with key individuals.
Until now these are conclusions reached on dust suppressants:
• A number of North and Central European cities tested The evidence of the effectiveness of applying dust suppressants to road surfaces to reduce ambient PM10 concentrations. It is noteworthy that all studies were conducted in regions with relatively wet comes from a number of European cities with different climates (Sweden, Norway, Finland, Netherlands, UK, Germany, Austria and North Italy). Until March 2014, no studies are available at the Mediterranean region.
• In North and Central Europe, Where there are were high dust loads, the application of dust suppressants has been shown to be effective at reducing the daily average PM10 concentrations and the number of days when it exceeds 50 µg m-3. Therefore it has, having a role to play in achieving the EU limit value (which allows 35 days above 50 µg m-3per year).
• Based on the literature review it can be concluded that, in Northern and Central Europe, Dust suppressants are effective only where the road dust load is high and the road dust contributes a significant proportion of the daily average PM10 concentrations, such as in the Nordic countries where the use of studded types and de-icing agents give rise to high PM10 concentrations when the snow melts in the spring and in dusty Mediterranean countries where the low precipitation rates allow the road dust to build up, and there are unpaved areas such for parking industrial roads and school playgrounds. The use of dust suppressants on unpaved roads is more effective than on paved roads in terms of the PM10 emission reduction potential. For the best results dust suppressants application need to be applied over a wide area. No information is available for the Mediterranean region, where AIRUSE will produce the first evaluation both on paved and unpaved roads.
• The road dust load can also be high around certain industrial and construction sites. Application of a dust suppressant within these sites helps reduce the track-out of dust onto local roads.
• Application of dust suppressants at a rate of 10 g m-2 generally appears to be effective on Nordic and Central European paved roads; for unpaved roads, and industrial and construction sites a higher application rate is needed (100-200 g m-2).
• The effects of dust suppressants seem to last for several days after application, but are dependent on the traffic flows, weather conditions and road surface characteristics.
• There is conflicting evidence as to whether a mixture of CMA with potassium formate is more effective than the use of CMA on its own. CMA and potassium formate are considered preferable to the use of chlorides (CaCl2 and MaCl2) because they are less corrosive to metals and more biodegradable in ground water, which is important where it is the source of drinking water. However, they are more expensive. In general, the use of MgCl2, CaCl2, CMA and potassium formate appears to be equally effective in Nordic and Central Europe.
• No conclusions can be drawn today for the Mediterranean region. The high solar radiation may reduce strongly the efficiency of dust suppressants.
Results on street washing and sweeping reached until now are:
• There remains a relatively small number of studies of the impact of street sweeping and washing on ambient PM10 concentrations in Europe. Most studies have been limited spatially and temporally. The road sweeping studies have generally shown no effect when the uncertainties of the measurements are taken into account. The one widespread and long term (one year) study, undertaken in the United States, showed benefit of road sweeping in reducing road PM10 emissions but it required all roads to be swept after the application of abrasives following snow storms.
• The evidence on the effect of road washing, either alone or in combination with sweeping, is more positive with most studies showing a reduction in ambient PM10 concentrations. This may be due to the water reducing the release of PM¬10 into the air rather than removing dust from the road surface.
• Most of the evidence of a benefit of street cleaning (sweeping and/or washing) comes from areas where road dust loadings are particularly high due to the use of winter tyres/tracking sanding (e.g. Finland ) or near industrial sources (e.g. in Bootle, UK and Hamilton, Canada), and major construction sites (e.g. Finland).
• A preliminary trial of a prototype road sweeper suggests that new technologies are being developed that might have improved ability to remove PM10 from road surfaces and reduce ambient concentrations. A PM10 certification system for road sweepers is operated by a European trade organisation but does not appear to be able to differentiate the best sweepers from those that perform less well. A German test procedure appears to be better at differentiating between sweepers.
• There is some evidence that vacuum road sweepers can increase PM10 emissions. To overcome this some manufacturers are using filter bags to reduce the PM10 emissions from the air outlet of the sweepers.
• Further real world tests of a range of sweepers, as well as tests over a large area are required to increase understanding of the effects of street cleaning on PM10 emissions, ambient concentrations and whether it can play a role in reducing exceedances of the daily PM10 limit value.