La. Warren et Ap. Zimmerman, THE IMPORTANCE OF SURFACE-AREA IN METAL SORPTION BY OXIDES AND ORGANIC-MATTER IN A HETEROGENEOUS NATURAL SEDIMENT, Applied geochemistry, 9(3), 1994, pp. 245-254
This study provides empirical validation of current trace metal sorpti
on theory in a small urban river. We demonstrate that trace metal comp
lexation reactions occur predominantly at the suspended particulate su
rface involving surface layers of Fe oxides and organic matter. Associ
ated surface areas of these geochemical fractions were calculated wher
e possible, using the total surface area (TSA) of the suspended partic
ulate matter pool (SPM) in conjunction with estimates of suspended par
ticulate Fe and Mn oxides (SPOX) and organic matter (SPOM) concentrati
ons. Iron and Mn oxides concentrations were estimated using an extract
ion scheme. For two samples where no SPOM or Mn oxides were present, e
stimates of Fe oxides associated surface area were determined which co
mpared favourably to literature estimates, providing further evidence
for acceptable selectivity of extraction schemes. The utility of liter
ature estimates of surface areas for single component sediments in het
erogeneous sediments was also assessed. In mixed sediment samples, exp
osed surface areas of discrete phases are probably reduced due to mixe
d layering effects of the coatings, and the use of constants to estima
te the surface areas of individual fractions does not work, since the
relationship between the concentration of a given sedimentary fraction
and its exposed surface area is no longer predictable.