Assessment of toxic heavy metals in urban lake sediments as related to urban stressor and bioavailability

A suite of heavy metals was monitored at sediments and overlying water in three urban lakes located in Seoul, Korea during spring season 2006. Metals measured were zinc, arsenic, chromium, copper, nickel, and cadmium. All metal concentrations in urban lake sediments were much higher than those in natural lake sediments. Elevated metal levels in urban lake sediments are associated with urban runoff, including street dust polluted by heavy metals. Metals in sediments from urban lakes were extracted with a weak electrolyte solution (0.1 M Ca(NO3)(2)) to predict the toxicity of metals. Among the six heavy metals studied, Cu was the most extractable, followed by Ni and Zn. Ca(NO3)(2)-extractable metal recoveries has a good relationship with metal toxicity based on Chironomus riparius bioassay. This study showed that urban stressors such as vehicle emissions could increase the concentration of heavy metals in urban lake sediments. In addition, there is a positive relationship between sediment toxicity by using C. riparius bioassay and Ca(NO3)(2)-extractability of heavy metals from sediments.