Suspended sediments were collected via filtration at multiple locations along the river for comparison to soil collected from potential sources throughout the watershed. The pellet method commonly used for soil requires approximately 0.5 g (Musil et al. Spectrochim Acta, Pt A: At Spectrosc 55:1747-1758, 2000; Bustamante et al. Spectrochim Acta, Pt A: At Spectrosc 57:303-309, 2002; Mikolas et al. Anal Bioanal Chem 374:244-250, 2002; Lee et al. Spectrochim Acta, Pt A: At Spectrosc 58:523-530Q1, 2003; Hassan et al. Spectrochim Acta, Pt A: At Spectrosc 63:1225-1229, 2008; Jantzi et al. Spectrochim Acta, Pt A: At Spectrosc 115:52-63, 2016); however, on average, less than 0.1 g of sediment was non-uniformly distributed and could not be separated from the filters on which they were collected; therefore, a novel "filter pellet" method was developed in order to homogenize and pelletize these filter-bound specimens, requiring only 50 mg of sediment on an 86-mg cellulose nitrate membrane filter. A quantitative multi-element LA-ICP-MS analysis method was optimized for the filter pellets. A mixing model was then utilized to apportion the primary sources of sediment composing the suspended sediment samples. The analytical performance of the filter pellets was similar to that achieved with the soil pellets. An element menu of 17 elements was obtained with recoveries between 75 and 125 percent, precision of 10 percent or less (relative standard deviation), repeatability of 10 percent or less for duplicate analyses, and limits of detection in the ppb to low ppm range. A significant source of sediments was determined to be coming from an area of particular concern within the Mgeta Catchment of the Ruvu River Basinthe meta-anorthosite complex, which comprises less than 3 percent of the basin yet contributes up to 10 percent of the suspended sediment load in the Ruvu River. A novel sample preparation strategy was developed in which sediments bound to filters were processed into pellets for analysis by LA-ICP-MS (and potentially LIBS). The quantitative multi-element LA-ICP-MS data generated were of sufficient quality for use in sediment fingerprinting applications without the need for acid digestions. This article describes the method development and LA-ICP-MS results of the filter pellet method and a brief exploration of the sediment fingerprinting results. (publisher abstract modified)
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