Particle Size Distribution and Hydrodynamic Characteristics of Solid Matter Carried by Runoff from Motorways

Abstract

This paper studies solid matter from a section of the A9 motorway, Kerault Region, France, used in a study of the effects of pollution. This study analyzed both settled sediments from collecting basin and characteristics of sediments in the water column during and after eight storm events between October 12, 1993, and February 6, 1994. Settled sediments were used to measure particle sizes, mineral content, and related characteristics, whereas water samples were used to document total suspended solids, mineral content, and heavy metals. Solid particles larger than 100 IJ-m in diameter are easily separated by simple settling, unlike particles smaller than 100 IJ-m in diameter, which remain in suspension in nmoff. To treat runoff, particles smaller than 50 IJ-m in diameter, which represent approximately three-quarters of the weight of the solids, must be studied. On average, 50% v/v of particles have a diameter less than 15.2 IJ-m, whereas the geometric mean is 12.6 IJ-m. Regarding sedimentation speed, from the eight rainfalls studied, 50% w/w of particles smaller than 50 IJ-m in diameter fall at a speed less than 2.98 m/h on average (results for the eight rainfalls vary from 2.5 to 3.3 m/h), and 50% of particles between 50 and 100 IJ-m in diameter fall at a speed less than 9.8 m!h on average (results of the eight rainfalls vary from 5.7 to 13.1 mIh). Thus, treatment of runoff entails separating or eliminating solid waste. Furthermore, measuring sedimentation speed of particles with diameters smaller than 100 IJ-m seems to be an essential stage in the design of treatment plants (Vignoles, 1991). Water Environ. Res .. 71, 398 (1999).

Understanding the role of land use in urban stormwater quality management

“…Contrary to these findings, other studies have reported a larger fraction of fine particulates (Andral, 1999;Pechacek, 1994). The particle size of sediments is a function of the catchment characteristics.…”

“…However at the same time it is important that the facilities provided are capable of removing the critical size range of sediments which would be carrying a significant pollutant load. Research has shown that due to their physicochemical characteristics, the finer particulates are more efficient in the adsorption of pollutants and hence will carry a relatively higher pollutant concentration (Andral, 1999;Hoffman et al, 1982;Roger et al, 1998;Sartor and Boyd, 1972). However, outcomes from some studies have noted that the fraction of fine particulates in runoff can be small, and as such the total pollutant load would be smaller when compared to the load carried by the coarser particulates (Marsalek et al, 1997).…”

Analysis of heavy metals in road-deposited sediments

“…Similarly, Hamilton et al [18] showed that the organic fraction plays a major role in partitioning metals into different particle sizes. Several other researchers have reported that fine particulates contain higher organic carbon content than the coarse sediment [10,19]. Therefore, the crucial role played by finer particulates in urban stormwater is further exacerbated by the high content of organic carbon present.…”

“…On the other hand, when finer materials are incorporated into urban stormwater runoff, they have the ability to stay in suspension longer and are therefore transported a greater distance by urban runoff [9]. Furthermore, particles smaller than 50 m can be a significant component in runoff, contributing to as much as three quarters of the weight of total solids [10]. Bender and Terstriep [11] found that conventional street sweepers are only able to efficiently remove particles larger than 250 m. Though efficiencies have greatly improved over the last two decades, the removal of fine fractions is still an issue [12].…”

Grain size distribution of road-deposited sediment and its contribution to heavy metal pollution in urban runoff in Beijing, China

“…The behavior of RDS in runoff depends on its grain size distribution [11,12]. Furthermore, smaller particles have lower densities [1], greater surface area per volume unit and higher organic matter contents [13,14]. For most pollutants, higher concentrations are found on smaller RDS [15][16][17].…”