Multi-element analysis of road-deposited sediment in an urban drainage basin, Honolulu, Hawaii

Road-deposited sediment (RDS) and its associated contaminant load play a cr itical role in degrading receiving water bodies. Few quantitative multi-ele ment RDS studies exist, and there are none From Hawaii. This lack of baseli ne data combined with concerns with high concentrations of Pb and Cu in fis h and enrichment of Cu, Pb and Zn in bed sediments from Manoa Stream, Hawai i, lead to a detailed characterization of RDSs in Manoa basin. Data for a t otal analysis of 23 elements using inductively coupled plasma atomic-emissi on spectrometry and instrumental neutron activation analysis and 16 element s using a 0.5 M HCl partial leach are presented For RDSs and background soi ls. Concentration data, comparisons with environmental guidelines, and conc entration enrichment ratios (CERs) all indicate that RDS in Manoa has a sig nificant degree of anthropogenic pollution. The most environmentally import ant elements were Pb, Sb and Zn. Concentrations of these elements, primaril y vehicle contributed, compare favorably with those from other studies of R DS. The high mean concentration of Pb (151 mg/kg) compared to background so ils (13 mg/kg) indicates remobilization of Pb previously stored in soils an d transported to road surfaces by water erosion processes. The higher Pb CE RTotal in RDSs compared to bed sediments from Manoa Stream suggests a poten tial link via ubiquitous storm drains and subsequent dilution with less con taminated fluvial sediments. Data from the HCl leach also support Pb and Zn as having significant anthropogenic signals, and Cu having a moderate sign al. These data indicate that RDSs in Manoa basin are generally contaminated with certain potentially toxic elements and the legacy of past use of lead ed gasoline is still a concern in this urban drainage system. (C) 2000 Else vier Science Ltd. All rights reserved.