Trace elemental analysis of water and sediment samples from preselected sites along the Mahoning River via neutron activation, atomic absorption, and wet chemical techniques

Abstract

A neutron activation analysis (NAA) study, using an approximate 10 milligram252 Cf source, was originally carried out on specific portions of the Mahoning River between Lake Milton Reservoir and the city of Niles, Ohio. Water samples were collected at fourteen sites, while sediment samples were obtained at ten locations, many of which bracketed sources of industrial and municipal effluents. A 125 ml quantity of each water sample was irradiated for a period of one hour, while 7 gm samples of the sediments were irradiated for 15 minutes, each in a flux of 1 x 10 8 neutrons (cm2-sec.) After a decay interval of 30 seconds, all samples were counted for 20 minutes via an 8.5% efficient Ge(Li) detector having a peak-to-Compton ratio of 16:1. Due to the success of the preliminary examinations, additional methods for determining the concentrations of specific trace elements in the same water samples were undertaken. Comparative results were obtained for three elements, calcium, magnesium, and copper, by atomic absorption analyses (via a Perkin-Elmer Model #107 Atomic Absorption Spectrophotometer). This method provided values for two other elements, zinc and lead. In addition, wet chemical -methods produced comparative results for three elements (calcium, magnesium, and chlorine) , while another species (iron) and water hardness were also detected. The results of the determinations showed that additional techniques could be used (under specified conditions) to obtain concentration data for elements which do not readily respond to neutron activation analysis. Although significantly more susceptible to interferences than NAA, atomic absorption spectrophotometry and wet chemical methods yeild fairly reproducible results for certain elements.