Search

Road run-off water quality can be significantly impacted by many pollutants deposited on road surfaces through vehicular activities. Any control strategy for the improvement of water quality relating to organic and inorganic pollutants should be based on a detailed knowledge of pollutant built-up processes and the relationship of pollutants to one another. Total volatile suspended solids (VSS), polycyclic aromatic hydrocarbons (PAHs) and heavy metals were estimated in total suspended solids (TSS) collected in two catchments. This study found a good relationship between total VSS and TSS and between TSS and PAHs. This relationship information can be utilized for the development of effective Best Management Practices for TSS control. However, the relationship between TSS and heavy metals was identified as being strong in only some cases. [ABSTRACT FROM PUBLISHER]

Abstract: Soakaway sediment trapped in urban infiltration facilities exhibits high heavy metal content that makes it an important diffuse pollution source of groundwater contamination. In this study, heavy metal (Cu, Zn, Cd and Pb) content, speciation and stable isotopic variation of Pb in soakaway sediments were coupled and compared with soils (surface and underlying), and road dusts (residential and highway) to trace their contamination characteristics, mobility and source. Soakaway sediment and residential road dust were found to exhibit higher metallic content of anthropogenic origin with high mobility. Isotopic ratios in exchangeable fraction showed the least 206Pb/207Pb and 208Pb/207Pb ratios. Although there were significant differences in total metal content and speciation between two road dust samples, their isotopic signatures exhibited close resemblance and aligned with anthropogenic markers such as paint, petrol and aerosols. Heterogeneity of isotopic signature in different fractions of soakaway sediments seems to have originated from the mixing of multiple sources of heavy metals. Study concludes that mobility, source and contamination characteristics of metals in soakaway sediment were different from urban soil and road dust samples due to their complex environment and regular metal supply by road runoff. [Copyright &y& Elsevier]

Abstract: Artificial infiltration facilities (AIFs) that enhance groundwater recharge and regulate urban runoff are going to be an integral element of the urban infrastructure. However, AIFs provide a sink which trap pollutants that are likely to cause groundwater contamination. The current study aimed first to examine the mobility characteristics of Cu, Zn, and Pb through soil and soakaway sediment using an integrated analytical approach for column leaching with artificial road runoff (ARR) and then to differentiate the sorption patterns among different samples, (i.e., surface soil, underlying soil, and soakaway sediments) using mass balances. In addition, the study compares metal retention and release under continuous and intermittent flow conditions. Column leaching experiments were conducted using batches for 10 and 30d under continuous flow condition and for 20d of intermittent leaching. Heavy metal content and partitioning in soil and sediment used in columns were well characterized before and after leaching experiments. The results showed that a gradual increase in pH and decrease in dissolved organic carbon had pronounced effect on the mobilization of heavy metals. Pb showed the highest retention compared to Cu and Zn which implies that metal complexes play a pivotal role in metal transport. Labile fractions were found to be trapped by the solid materials for retention and their high concentration in ARR is a major concern from the pollution point of view through infiltration facilities. Results obtained in this study predict the risk associated with the release of retained heavy metal under changing environmental conditions in AIFs. [Copyright &y& Elsevier]

Selective sequential dissolution (SSD) and isotopic dilution are two most commonly applied techniques for the measurement of mobile fraction of heavy metal present in the urban environment. This work examined the compliance between SSD proposed by the Community Bureau of Reference (BCR) and isotopic dilution technique (IDT) for determination of mobile pool of heavy metal contained in soakaway sediment, road dust, and soil sample. Heavy metals (Cu, Zn, Cd and Pb) were fractionated using the three-stage BCR protocol, while isotopically exchangeable metal concentrations (E-value) were investigated through isotopic tracers (111Cd, 65Cu, 207Pb and 66Zn). In general, total contamination level, E-value and BCR exchangeable fractions of different samples followed the similar order of road dust . soakaway sediment . soil. Results revealed that the E-value exceeded the BCR exchangeable fraction in all samples. In addition, the first three fractions of BCR which have potential to become mobile under certain environmental conditions were collectively termed as "potential mobile pool" and compared with E-value. It was concluded that metal extracted by weak acid underestimates the exchangeable fraction while the potential mobile pool extracted by three reagents overestimates the real mobile forms of heavy metals. However, better mobility characteristics of heavy metals can be assessed by coupling information obtained through sequential extraction and isotopic exchange. [ABSTRACT FROM AUTHOR]

Abstract: Groundwater contamination by heavy metals from infiltration facilities receiving road runoff is of potential concern. In this study, sorption tests were conducted to evaluate the influence of the water quality of road runoff, especially dissolved organic matter (DOM), on the sorption of heavy metal species by soakaway sediment. Sequential batch tests were conducted to assess metal sorption by the soakaway sediment receiving road runoff from residential and heavily trafficked areas. Ni was adsorbed by the sediment, indicating that soakaway sediments function to prevent groundwater contamination by Ni. In contrast, Zn was released from the soakaway sediment in sorption tests using heavily trafficked road dust leachates. Ni, Cu, Zn, and dissolved organic carbon concentrations were higher in soakaway sediment leachates obtained by sorption tests using heavily trafficked road dust leachates than those using residential road dust leachates, suggesting traffic activities contaminate these pollutants. A large portion of Zn, released from the soakaway sediment, existed as stable complexes. DOM in road runoff possibly enhances the release of Zn from the sediments within infiltration facilities and might cause groundwater contamination. [Copyright &y& Elsevier]

Individual particles containing Cr and/or Pb and other major components were identified in road dust from a heavily used road (hereinafter ‘heavy traffic road dust’), road dust from a residential area and soakaway sediment by electron probe microanalyser to locate their sources and carrier particles. Individual particles containing high levels of Cr and/or Pb (⩾0. 2%) were identified using wavelength dispersive spectrometry (WDS) map analysis. Chromium, Pb and other major elements were then determined by means of a combination of WDS and energy-dispersive spectrometry in all identified particles, 50 particles containing neither Cr nor Pb from each type of road dust and soakaway sediment, and yellow road line markings. WDS map analysis revealed that many particles containing both Cr and Pb were present among the identified particles in heavy traffic road dust, whereas they were minor components in road dust from the residential area and soakaway sediment. The plots of X-ray intensities of Cr vs. Pb were linear for the identified particles containing both Cr and Pb in heavy traffic road dust, and the line closely fitted the plots for the three yellow road line marking samples. Individual particles were then classified using cluster analysis of element components. The results revealed that the adsorption of source materials or released metals onto soil minerals occurred in road dust and soakaway sediment, that the yellow road line markings were sources of Cr and Pb in heavy traffic road dust, and that materials containing Fe as a major component, such as stainless steel, were additional sources of Cr in both road dust and soakaway sediment. [Copyright &y& Elsevier]