The effects of urbanization on the chemical quality of three tidal bayous in the Gulf of Mexico

Water and sediment quality in three tidal bayous located near Pensacola, Fl orida, were assessed during 1993-1995. The primary objective was to determi ne the environmental condition of the relatively small urban bayous by comp aring the chemical quality of the sediments and surface water with publishe d guidelines and criteria developed to protect marine life. Surface water c oncentrations of most potential toxicants such as heavy metals, organochlor ide pesticides, PAHs and PCBs were usually below method detection limits. T he major exception to this trend was for copper which consistently exceeded Florida and National acute and chronic water quality criteria. Nickel, cad mium and chromium intermittently exceeded these criteria. Sediment contamin ation was site-specific and chemically diverse. The concentrations of as ma ny as 17 compounds exceeded proposed Florida sediment quality assessment gu idelines indicating the potential for adverse biological effects. Nutrient concentrations, with one exception, were below average levels found in othe r Florida estuaries. Seasonal variation in contaminant concentrations for s ediment collected from the same sampling station was less than an order of magnitude. The differences in the concentrations of the same analytes as me asured for the multiple sampling stations located within the same bayou var ied 1 to 2 orders of magnitude and over 2 orders of magnitude for the 20 sa mpling stations located in the three bayous. A within-bayou sediment contam inant gradient was evident; sediment quality generally improved seaward.