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Monitoring of dust emission on gravel roads: Development of a mobile methodology and examination of horizontal diffusion
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Highway and Railway Engineering.
Dalarna Högskolan.
2009 (English)In: Atmospheric Environment, ISSN 1352-2310, Vol. 43, no 4, 889-896 p.Article in journal (Refereed) Published
Abstract [en]

Traffic-generated fugitive dust on gravel roads impairs visibility and deposits on the adjacent environment. Particulate matter smaller than 10 mu m in diameter (PM10) is also associated with human health problems. Dust emission strength depends on the composition of granular material, road moisture, relative humidity, local Climate (precipitation, wind velocity, etc.), and vehicle characteristics.

The objectives of this study Were to develop a reliable and rapid mobile methodology to measure dust concentrations on gravel roads, evaluate the precision and repeatability of the methodology and correspondence with the currently used Visual assessment technique. Downwind horizontal diffusion was studied to evaluate the risk of exceeding the maximum allowed particulate matter concentration in ambient air near gravel roads according to European Council Directive [European Council Directive 1999/30/EC of 22 April 1999 relating to limit values for sulphur dioxide, nitrogen dioxide and oxides of nitrogen, particulate matter and lead in ambient air. Official Journal of the European Communities. L163/41.].

A TSI DustTrak Aerosol Monitor was mounted on an estate car travelling along test sections treated with various dust suppressants. Measured PM10 concentrations were compared to Visual assessments performed at the same time. Airborne particles were collected in filters Mounted behind the vehicle to compare the whole dust fraction with the PM10 concentration. For measuring the horizontal diffusion, DustTraks were placed at Various distances downwind of a dusty road section.

The mobile methodology was vehicle and speed dependent but not driver dependent with pre-specified driving behaviours. A high linear correlation between PM10 of different vehicles makes relative measurements of dust concentrations possible. The methodology gives continuous data series, mobility, and easy handling and provides fast, reliable and inexpensive measurements for estimating road conditions to make road maintenance more efficient.

Good correlations between measured PM10-values, visually assessed dust generation and dust collected in filters were obtained. PM10 seems to be correlated to the whole dust fraction that impairs visibility on gravel roads.

A decay in PM10 concentration as a function of distance from the road was observed. Measured particles principally did not travel further than 45 m from the road. The risk of exceeding the PM10 concentration stated in the EC-directive seems small.

Place, publisher, year, edition, pages
2009. Vol. 43, no 4, 889-896 p.
Keyword [en]
Gravel roads, Dust emission, PM10, Methodology evaluation, European Council Directive, UNPAVED ROADS
URN: urn:nbn:se:kth:diva-12355DOI: 10.1016/j.atmosenv.2008.10.052ISI: 000263188100016ScopusID: 2-s2.0-57949105114OAI: diva2:309913
QC20100615Available from: 2010-04-09 Created: 2010-04-09 Last updated: 2010-06-15Bibliographically approved
In thesis
1. Evaluation of Dust Suppressants for Gravel Roads: Methods Development and Efficiency Studies
Open this publication in new window or tab >>Evaluation of Dust Suppressants for Gravel Roads: Methods Development and Efficiency Studies
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Approximately 75 percent (300 000 km) of the total Swedish road network and 20 percent(20 000 km) of the national road network consists of gravel roads. One of the most significantproblems associated with gravel roads is traffic-generated dust emission, which contributes tothe deterioration of the road surface and acts as a major source of particulate matter releasedinto the atmosphere, thereby involving public economics, road safety, human health, andenvironmental quality. In order to bind the fine granular material, which is prone to rise into theair, dust suppressants are applied on roads on a yearly basis.

Methods for evaluating the efficiency of dust suppressants will facilitate in the selection of themost appropriate product and its optimal application rate. For example, methods forsupervision of residual dust suppressant concentration are valuable tools for estimatinglongevity and optimal application rates, and, consequently, effectiveness of different products.

Application of the proper dust suppressant to a gravel road ensures road safety and ridingcomfort as well as creating a cleaner and healthier environment for residents in buildingsadjacent to the road. It also reduces the need and cost for vehicle repair, road maintenanceactivities, and aggregate supplementation.

Both field-based and laboratory research were performed to evaluate the efficiency of varioussuppressants and the influence such factors as product concentration, leaching, and fine materialcontent have on the efficiency of different products. Within the field-based research, a newlydeveloped mobile methodology was used to measure dust emission on numerous test sectionstreated with various dust suppressants. In general, all dust suppressants tested, except apolysaccharide (sugar) and products, which form a brittle surface crust, i.e. lignosulphonate andbitumen emulsion, showed acceptable dust reduction.

Test sections treated with a magnesium- or calcium chloride solution were the most effectivelydust suppressed. The application of solutions instead of a solid salts achieves a more uniformproduct distribution and, therefore, probably a more efficient performance. By applying acalcium- or magnesium chloride solution instead of traditionally used solids, the cost for annualdust control, as well as the environmental impact from the release of these chemicals in theenvironment, can be reduced by 50 percent.

A significant problem when using dust suppressants is their tendency to leach during rainfalldue to their soluble properties. Residual chloride could be detected in the gravel wearing courseover a longer period of time than lignosulphonate and, therefore, showed more effective longtermperformance. Optimal percentages of fine material for minimal lignosulphonate andchloride leaching were found to be 15 percent by weight and 10-16 percent by weight,respectively. Ions of calcium chloride seemed to initiate flocculation of clay particles, therebypreventing them from leaching. Still, the fine material in gravel wearing courses has to be replenished regularly as indicated by studies of the longevity of fine material. Loss up to80 percent was found after two years.

Toxicity tests show that dust suppressant application for dust control purposes, at traditionallyused application rates, does not constitute a threat to sensitive aquatic life. Tests on subsoilwater samples indicated elevated chloride levels, which possibly could cause corrosion to pipes,but not high enough to flavour drinking water.

Place, publisher, year, edition, pages
Stockholm: KTH, 2010. 64, vi p.
Trita-VT. FR, ISSN 1650-867X ; 10:05
Gravel road, dust, particulate matter, PM10, horizontal dust diffusion, deteriorations, maintenance, dust control, dust suppressants, efficiency, application rate, leaching, residual concentration, seasonal variations, salt solution, solid salt, calcium chloride, magnesium chloride, lignosulphonate, polysaccharide (sugar), bitumen emulsion, rape oil, starch, surfactant, mesa, clay, fine material content
urn:nbn:se:kth:diva-12359 (URN)978-92-7415-612-6 (ISBN)
Public defence
2010-04-21, F3, Lindstedtsvägen 26, KT, Stockholm, 10:00 (English)
QC20100616Available from: 2010-04-09 Created: 2010-04-09 Last updated: 2010-06-16

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