The quality of water, sediment, and biota was determined at four sites in canals and drainage ditches at Miami International Airport (MIA) during high- and low-water periods and during summer and winter 1971–72. Concentrations of common ions, such as calcium, sodium, chloride, and magnesium, tended to be above average for fresh water because of periodic salt-water intrusion. Nitrogen, phosphorus, and pesticides were in higher concentrations than typical for undisturbed areas of south Florida, but not higher than usual for the urban coastal area, so it is not known to what extent these chemicals are attributable to surrounding urbanization. Heavy metals, oil and grease, and PCB's (polychlorinated biphenyls) were the best indicators of the effects of MIA on water quality. Concentations of the above were quite variable, high values for each were recorded and were probably associated with recent discharges from industrial sources. Arsenic, lead, iron, and chromium all exceeded, in one or more samples, the U.S. Public Health Service's recommended upper limits for metals in water. Only iron normally exceeds these standards in the natural waters of south Florida. PCB's were detected in most samples and were in concentrations up to 1,000 micrograms per kilogram in fish. In addition to pesticides and PCB's, another group of persistant chlorinated compounds, PCN's (polychlorinated naphthalenes) were detected in water, sediment, and fish. This is the first known detection of these compounds in the environment.
