Filter properties of seam material from paved urban soils

Abstract

Abstract.Depositions of all kinds of urban dirt and dust including anthropogenic organic substances like soot change the filter properties of the seam filling material of pervious pavements and lead to the formation of a new soil substrate called seam material.In this study, the impact of the particular urban form of organic matter (OM) on the seam materials CEC pot , the specific surface area (A s ), the surface charge density (SCD), the adsorption energies (E a ) and the adsorption of Cd and P b were assessed. The Cd and P b displacement through the pavement system has been simulated in order to assess the risk of soil and groundwater contamination from infiltration of rainwater in paved urban soils.A s , E a and SCD derived from water vapor adsorption isotherms, CEC pot , P b and Cd adsorption isotherms where analyzed from adsorption experiments. The seam material is characterized by a darker munsell-color and a higher C org (12 to 48 g kg −1 ) compared to the original seam filling. Although, the increased C org leads to higher A s (16 m 2 g −1 ) and higher CEC pot (0.7 to 4.8 cmol c kg −1 ), with 78 cmol c kg −1 C its specific CEC pot is low compared to OM of non-urban soils. This can be explained by a low SCD of 1.2×10 −6 mol c m −2 and a low fraction of high adsorption energy sites which is likely caused by the non-polar character of the accumulated urban OM in the seam material.The seam material shows stronger sorption of P b and Cd compared to the original construction sand. The retardation capacity of seam material for P b is similar, for Cd it is much smaller compared to natural sandy soils with similar C org concentrations. The simulated long term displacement scenarios for a street in Berlin do not indicate an acute contamination risk for P b. For Cd the infiltration from puddles can lead to a breakthrough of Cd through the pavement sysCorrespondence to: T. Nehls (thomas.nehls@tu-berlin.de) tem during only one decade. Although they contain contaminations itself, the accumulated forms of urban OM lead to improved filter properties of the seam material and may retard contaminations more effectively than the originally used construction sand.

Water infiltration in urban soils and its effects on the quantity and quality of runoff

“…The amount of macropores is very important for hydraulic conductivity as shown by the significant correlation between infiltration rates and macropore volume (see Table 4). Therefore, one of the most effective measures is to amend compacted soils by mechanically loosening before tree-planting, adding flyash (Yunusa et al 2009) and organic materials (Nehls et al 2008), and introducing earthworms and other beneficial burrowing soil organisms. Moreover, heavy foot traffic on the grass in the park areas or other greenbelt soils must be avoided.…”

Water dynamics at the urban soil-atmosphere interface—rainwater storage in paved surfaces and its dependence on rain event characteristics

“…This can cause severe damage to buildings and infrastructures (Goebel et al 2007) as well as increased leaching from vadose zone contaminations. An increased infiltration would also bear the risk of groundwater contamination due to recent emissions (Nehls et al 2008). Furthermore, the water is needed at the surface rather than in the ground for other uses such as evaporative cooling.…”

Black Carbon in Soils: Relevance, Analysis, Distribution

“…They found that BC (CTO 375) can be cost-effectively estimated from existing data on labile carbon from loss-on-ignition analysis (450°C) and total organic carbon (1050°C). Nehls et al (2008) found BC in partly paved urban roadside soils to contribute up to 28% of OC (Fig. 2) and that BC correlates with magnetic susceptibility.…”