ANALYSIS OF TOXIC METALS IN STREAM SEDIMENTS IN THE BASS BROOK WATERSHED, NEW BRITAIN, CONNECTICUT

The Bass Brook watershed encompasses an area that is predominantly residential with some commercial properties in New Britain, CT. The stream drains into Piper Brook, which in turn flows into the South Branch of the Park River. Stream water quality data collected in mid to late summer 2011. Conductivity ranged from 86 to 424 µs/cm, with the highest values near a business park. Nitrate was generally less than 0.03 mg/L, while phosphate values were high (<20 to 50 mg/L), and pH was 6.5 to 8.0. In general, a wide range of stream biota was also observed in most stream segments. In order to assess the potential for toxic trace metal contamination, 41sediment samples (<64 micron fraction) were collected from 19 sites. Sites were sampled along each tributary in the watershed. A weak acid digestion was used to prepare samples for ICP-OES analysis to determine the concentration of major trace metal elements.

The results show a relatively low concentration of most metals. Arsenic is typically <0.5 ppm. The highest metal concentration are for barium, which ranges from 40 to 100 ppm with values up to 242 ppm; zinc, with values of 20 to 160 ppm; and copper, which typically ranges from 10 to 40 ppm, with one value of 127 ppm. Chromium ranges from 5 to10 ppm, and up to 81 ppm. Cobalt typically ranges from 3 to 10 ppm, with one site of 26 ppm. Lead ranges from <10 to >60 ppm with a peak value of 107 ppm, while cadmium values range form 0.2 to >1.0 ppm. Thallium values are < 0.6 ppm with several values from 1.1 to 2.2 ppm. Titanium is typically <6 ppm, but locally up to 37 ppm. Vanadium values are typically 10 to 30 ppm and locally up to 102 ppm;. Locally, levels of cadmium, chromium, copper, lead, and zinc exceed threshold effect concentrations, and lead locally exceeds the probable effects concentration. The highest metal concentrations were found in a streams draining into Batterson Pond, in a public park, and in a stream adjacent to a middle school.