MP7 Advances in Analysis and Measurements
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() Comparison of methods to determine suspended sediment associated metals in a mining impacted stream.
Bulter, B1, Ross, P1, Ranville, J1, 1 Colorado School of Mines, Golden, Colorado, USA
ABSTRACT- Acid-mine drainage (AMD) is an important source of metals to aquatic ecosystems. Once AMD is mixed with oxygenated stream water of neutral pH, there is a transformation of the AMD, which includes increased pH, oxidation of metal ions, precipitation of metal oxyhydroxides, and co-precipitation and/or sorption of metals. Understanding the fate and transport of these metals requires knowledge of the distribution of metals between the suspended solid and dissolved phases. Measurement of dissolved metals is straightforward: water is passed through a given pore-size filter (typically 0.45-
m) and the acidified filtrate is analyzed for metals. There are two commonly used methods for determination of suspended sediment-associated metals. A direct method is to completely digest a filter containing particles collected from a known sample volume; this is referred to in this paper as the TSS Digestion Method. An indirect method is to subtract the metals concentrations for a filtered acidified sample (pore size typically 0.45-m) from that of a non-filtered acidified sample, referred to in this paper as the Difference Method. The Difference Method is often used, as the TSS Digestion Method is more complex and time consuming. It has been debated, however, whether the Difference Method is acceptable. This paper compares temporal data collected from an AMD-impacted stream obtained by each of these methods. The applicability of each approach for the determination of suspended sediment associated metals will be discussed.
Key words: amd, suspended sediment