Pr. Teasdale et al., In situ collection of diagenetic and induced oxyhydroxide precipitates from riverine and estuarine sediments, ENV TECHNOL, 19(12), 1998, pp. 1191-1201
The use of plastic sheets as collectors of diagenetically-formed oxyhydroxi
des from riverine and estuarine sediments was evaluated. In a range of mate
rials tested in the laboratory, Teflon and polycarbonate were found to be t
he most efficient collector materials. Laboratory optimisation experiments
indicated that the deposition of oxyhydroxides on both materials occurred q
uickly (<2 weeks). In the field, oxyhydroxides were collected on Teflon she
ets as depositional bands just below the sediment-water interface. These ba
nds were much wider and more variable (1-5 cm) than those observed in labor
atory experiments (typically 0.5 an). This was attributed to the frequently
changing redox conditions at the field sites caused by a combination of se
diment movement and tidal processes. The deposits collected were predominan
tly iron with lesser amounts of manganese. At several sites strong correlat
ions were observed between the concentrations of manganese and zinc deposit
ed on the Teflon collector surfaces. In both the laboratory and field exper
iments, biologically-mediated iron oxyhydroxide deposition in anoxic sedime
nts was frequently observed (mainly caused by the activities of burrowing o
rganisms). The mechanism of iron deposition on polycarbonate was investigat
ed in detail. This plastic contains high concentrations of oxygen which is
released over sustained periods, thereby inducing the deposition of iron ox
yhydroxide even in anode sediments. It is proposed that polycarbonate may b
e used for investigating the impacts of oxygen introduction to anoxic sedim
ents by processes such as bioturbation and oxygen release from aquatic plan
t roots.