Comparison of metal homogeneity in grab, quartered, and crushed — sieved portions of stream sediments and metal content change resulting from crushing — sieving activity

Abstract

Restricted grain size sediment samples were collected along two streams. Metal content in some samples may have been influenced by landfill emissions. Each sample was divided into a grab portion, a quartered portion, and a portion crushed and sieved to a smaller size and then quartered. A duplicate sample from each of these portions was extracted. The Cu, Pb, Zn, Co, Ba, Fe, Mn, and Ca quantities were determined for each duplicate sample. Relative standard deviation was used to reflect homogeneity of metal content. Metal occurrence represented speciated metals or major components of chemical phases. Results indicated that variation of metal content among portions was uniform and did not vary as a function of absolute metal quantity. Homogeneity was similar in the same size grab and quartered samples. A more homogeneous metal state was displayed by the crushed and sieved sediments. However, this activity enriched softer chemical phases and associated speciated metals. It was concluded that sediments need not be quartered to obtain a better homogeneity of metal distribution and that field samples should not be crushed and sieved prior to chemical analyses. Assessment of sediments affected by metal emission sources must include a knowledge of metal homogeneity in individual samples.