Three bridge sites in central florida (i-4 and padgett creek, us-17-92 and shingle creek, and us-192 and shingle creek) were selected to study (a) the feasibility of treating highway runoff by using floodplains beneath these bridges and (b) the impact of bridging on biological diversity and productivity. soil and plant samples were collected from bridge areas affected by highway runoff as well as control areas upstream and downstream of the bridge areas. these sampleswere analyzed for extractable heavy metals (lead, zinc, iron, copper, nickel, chromium, and cadmium) to study the capacity of floodplain areas to retain these metals. soil samples collected from the bridge areas contained significantly higher concentrations of metals, particularly lead, than the control areas. metals were fixed in the soil and could be released to the surrounding body of water by highly acidic environments, organic chelating agents, and erosion processes. plants were also surveyed to determine dominant species, changes in diversity, and productivity at the bridge and control areas. in addition, bioassay experiments were designed to examine the potential impact on algal production of mixing highway bridge runoff and waterfrom adjacent streams. at all sites surveyed there were more individuals of common plant species in bridge areas than in control areas.bridge areas, however, appeared to be dominated by fewer species than control areas.(a) this paper was published in transportation research record no. 948, wetlands, floodplains, erosion, and storm waterpumping. see also irrd abstract no 281512
Abstract