La. Warren et al., GEOCHEMICAL PARTITIONING AND BIOAVAILABILITY OF COPPER TO AQUATIC PLANTS IN AN ARTIFICIAL OXIDE-ORGANIC SEDIMENT, Hydrobiologia, 304(3), 1995, pp. 197-207
This study investigated the effects of competition between binding sub
strates (organic matter and iron oxide) and between metals (cadmium an
d copper), on the partitioning of sedimentary copper and its subsequen
t bioavailability to an aquatic plant. Organic matter and a synthesize
d iron oxide, ferrihydrite, were added singly and in combination to a
series of sand sediments, which were then dosed with environmentally r
ealistic concentrations of cadmuim and copper and planted with rice, O
ryza sativa. Organic matter controlled copper partitioning and bioavai
lability, whereas the synthetic ferrihydrite bound negligible amounts
of either metal, even in the absence of organic matter. As organic mat
ter concentrations increased, operationally-defined leachable copper d
ecreased, organic-associated copper increased and the survival of rice
plants improved in an approximately linear fashion. At a nominal star
ting copper concentration of 5.8 mu g g dry wt(-1), plant survival aft
er four weeks averaged 0-8% in sediments without organic matter, 25% i
n a sediment containing 0.18% organic matter and 58% in a sediment con
taining 0.36% organic matter. These results suggest that organic-assoc
iated forms of copper are unavailable to plants, and that the operatio
nal definition of 'leachable' copper (extracted with dilute ammonium a
cetate) adequately represents the species of copper that is (are) avai
lable to plants. Our study using a well-characterized artificial sedim
ent supports the copper fractionation patterns and correlations betwee
n copper partitioning and bioavailability reported from the heterogene
ous, poorly characterized sediments of natural lake and river sediment
s.