Interactions of Cd and Cu in anaerobic estuarine sediments. I. Partitioning in geochemical fractions of sediments

Abstract

Abstract-Partitioning of Cd and Cu between geochemical fractions of an anaerobic estuarine sediment was determined after equilibrating fine-sandy sediment with different combinations of added Cd (0, 2.5, 5 mg/kg) and Cu (0, 12.5, 25 mg/kg). Sediments were placed in aquaria with 20 ppt seawater where bioassay test organisms were exposed for 14 d. At the start and conclusion of the experimental period, sediments were sequentially extracted to determine the elemental content of the exchangeable (EP), easily reducible (ERP), organic-sulfide (OSP), moderately reducible (MRP), and acid extractable (AEP) phases. Partitioning of the metals in both the native and treated sediments was, for Cd: OSP k ERP Ͼ AEP Ͼ EP (MRP was below detection) and for Cu: OSP k AEP Ͼ ERP Ͼ MRP Ͼ EP. Cadmium extracted in all phases and Cu in the EP, ERP, and OSP were proportional to the respective treatments. The EP-Cd, ERP-Cd, and OSP-Cd were affected by the Cu treatment and significant interactions occurred between Cd and Cu for the EPCd, ERP-Cd, OSP-Cd, EP-Cu, and ERP-Cu. Increasing levels of applied Cd and Cu resulted in greater amounts of EP-Cd and ERPCd, fractions that are the most bioavailable and the most readily available for desorption into the water column. A significant conclusion is that the input of nontoxic metals may affect the geochemical phase distribution, potential bioavailability, and toxicity of native sediment metals.

Interactions of Cd and Cu in anaerobic estuarine sediments. II. Bioavailability, body burdens and respiration effects as related to geochemical partitioning

“…Grass shrimp have normally high Cu levels due to a Cu-based respiratory pigment and so the treatmentinduced increase is very modest. Our previous investigation [14] found an average body burden of 121.75 Ϯ 7.15 g Cu/g in the shrimp from three sediment types of low native Cu. The blue mussel contains a Cu-based respiratory pigment as well as other metal-binding proteins, which may account for the more notable increases of both Cd and Cu as a function of treatment.…”

“…Sediment collection, treatment and bioassay information were given in the preceding paper [14] and in Rule and Alden [13]. Briefly, a fine-sandy textured estuarine sediment was spiked with appropriate amounts of stock solutions of Cd and Cu to provide six replicates of all combinations in the following concentrations (dry weight basis) of added Cd: 0 mg/kg, 2.5 mg/kg, and 5 mg/kg and Cu: 0 mg/kg, 12.5 mg/kg, and 25 mg/ kg.…”

Effect of metal mixture (Cu, Zn, Pb, and Ni) on cadmium partitioning in littoral sediments and its accumulation by the freshwater macrophyte Eriocaùlon septangulàre

“…The literature on Cd binding to sediment reports that the affinity of Cd for natural substrates follows the order Mn > Fe (amorphous) > chlorite > Fe (crystalline) = illite = > humics > kaolinite > silica [42], and there are examples of spiked Cd rapidly partitioning onto manganese oxides. For example, Cd applied to estuarine sediments quickly partitioned onto an ER (manganese oxide) fraction and repartitioned onto an organic and sulfide fraction with time [7,43]. The repartitioning of Cd onto the iron oxides over time might be expected through diagenetic processes.…”

“…Attempts have been made to take these factors into account when water‐and sediment‐quality guidelines for Cd have been developed [5,6]. Nevertheless, trace metals may also affect the distribution and toxicity of Cd [7–9], and their influence is not generally considered in guidelines. This influence may be of critical importance because Cd is released into the environment primarily in mixtures with other trace metals through nonferrous metal mining, smelting and refining processes, industrial effluents, and domestic sewage [10–12].…”

“…Chemical extraction techniques that selectively partition metals into geochemical fractions have been useful in improving our understanding of metal bioavailability [4,18,19]. The distribution of metals among geochemical fractions in sediment depends on the relative affinity of metals for each fraction, the solubility product ( K sp ) of mineral phases containing metals in each fraction, and the concentrations of all metals present [7]. The latter effect was examined in this study.…”