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Description
We selected 15 sites that included waterways leading to Biscayne Bay (freshwater canals), Biscayne Bay directly (marine brackish water), and ocean water (marine salt water). A total of 500 mL of surface water was collected (at approximately 30 cm depth) in clean polypropylene bottles from each site. Samples were first run through a Solid Phase Extraction process (SPE) using Strata XL-AW 100 μm polymeric weak anion cartridges (500 mg / 6 mL). For the SPE process, cartridges are first conditioned with 6 mL of 1% ammonium hydroxide in methanol, 6 mL of methanol and equilibrated with 6 mL of water. Then samples are loaded onto the cartridge for concentration of the compounds of interest. Lastly, PFAS were eluted from the cartridges with basic methanol (0.3% ammonium hydroxide in methanol), and then dried using a Nitrogen Evaporator. Dried samples were reconstituted to a final volume of 0.5 mL. Extracts were then analyzed by Liquid Chromatography-Triple quadrupole Mass Spectrometry (LC-MS/MS) to determine the quantity of each of the different PFAS (ng/L) present in the sample. LC-MS/MS data was processed by the Agilent Software Masshunter. The same sites were selected for Coliform and E. coli colony forming units’ detection, and samples were collected at the same time as the PFAS samples but using autoclaved 500 mL glass bottles. Samples were analyzed by pouring 100 mL of collected water into the wells on a ColiPlate. The 15 plates were incubated for 1 day at 37°C. If wells on the plates turned from yellowish to blue/green color after the incubation period, this represented a positive indication for Coliforms. If the blue/green well showed fluorescence also, that well was positive for E. coli. The most probable number (MPN) table of colony forming-units per 100 mL was used to determine the number of colonies present in each sample.