| Sediment samples were collected from the Rio Negro, Amazonas, Brazil, in order to determine concentrations of six EPA criteria heavy metals and correlate heavy metal concentrations with sediment grain size. Grab samples of sediment were taken from 32 stations at 11 sites during January 1999, with emphasis placed on collecting near populated areas. Following separation into three grain size categories and focusing on the <63mum fraction, samples were analyzed for cadmium, chromium, copper, lead, nickel and zinc concentrations by inductively coupled plasma spectroscopy (ICP). Overall, heavy metal levels increased with proximity to human habitation (e.g., Manaus) and were inversely correlated with grain size. |
