Suspended particulate oxides and organic matter interactions in trace metal sorption reactions in a small urban river

Abstract

Abstract. The relative scavenging abilities of suspended particulate oxides (SPOX), and organic matter (SPOM) for Cd, Zn and Cu were evaluated in a small, anthropogenically influenced river. In addition, the factor most important in influencing the sorption density (A,: metal concentration associated with a given phase divided by the concentration of that geochemical phase in the suspended particulate pool) of each metal to SPOX and SPOM were identified through multiple linear regression analyses from the suite of: pH, temperature, dissolved metal concentration, and the concentration of the other particulate fraction. Results indicate that SPOX-SPOM interactions do occur in trace metal complexation reactions; and interactions are both phase and cation specific. Fe oxides are able to outcompete discrete organic binding sites for Cu and Zn as a relative decrease in the amount of these two cations sorbed to organic matter was observed with increasing particulate Fe oxides. SPOM concentration was identified as being most important in influencing Cu sorption densities associated with the SPOX fraction. Organic matter -oxide complexes are postulated to occur that enhance oxide sorption of Cu such that relatively more Cu is sorbed to particulate oxides with increasing particulate organic matter concentrations. Dissolved concentrations of Cd and Zn were found to be most important in influencing the sorption densities for these two metals associated with the oxides fraction. The sorption behaviour appears to follow Freundlich isotherm behaviour where the amount sorbed is a function of the dissolved concentration.

Ferrihydrite precipitation in groundwater-fed river systems (Nete and Demer river basins, Belgium): Insights from a combined Fe-Zn-Sr-Nd-Pb-isotope study

“…precipitate (the water is undersaturated), they are likely adsorbed onto the Fe-oxyhydroxides (ferrihydrite), which are known to have a high sorption capacity. Previous studies (Sholkovitz and Copland, 1981;Warren and Zimmerman, 1994) demonstrated that the adsorption of dissolved trace elements onto riverine suspended matter is a function of a number of variables, including the concentration of organic substances, suspended matter residence time, particle size and surface area, pH, Eh, T and source composition. The pH-Eh-T-conditions at which the red suspended matter and red sediments exist and the source composition are broadly similar (Table 1).…”

Lignite-Derived Humic Substances for Treatment of Acid Mine Drainage

“…Overall DOM had a greater Cu adsorption density than FeOx, however trials adding particulate FeOx to DOM-complexed Cu showed FeOx was an effective scavenger, decreasing the proportion of Cu complexed to DOM. Alternate trials adding DOM to FeOx-sorbed Cu resulted in an increase in Cu sorption, suggesting FeOx-DOM complexation increased the system sorption capacity for Cu (Warren and Zimmerman 1994). Thus, HS incorporation in AMD treatment may result in an increased sorption capacity of precipitated hydroxides for some metals due to additional DOM complexation.…”

“…Interactions between HS macromolecules via cationic bridges, polar interactions, hydrogen bonding or van der Waals forces may cause HS insolubility (Swift 1996), resulting in removal of HS complexed metals by sedimentation. Similar HS binding mechanisms may occur with precipitated metal hydroxide surfaces (Warren and Zimmerman 1994), resulting in adsorption of HS complexed metals to precipitates, and subsequent enhanced settling.…”

“…Warren et al (1994) investigated the competition between suspended particulate iron oxides (FeOx) and organic matter for adsorption/complexation of Cd, Zn and Cu. They showed the adsorption densities of FeOx for Cd and Zn were 1-2 orders of magnitude greater than DOM at circum-neutral pH.…”

Metal removal via particulate material in a lowland river system

“…Minerals, diatoms and other components of suspended particulate material (SPM) in the water columns of rivers, lakes and estuaries have the ability to bind dissolved trace metals, thereby reducing metal toxicity and influencing environmental fate. There are two principal agencies of dissolved metal removal by SPM; adsorption onto mineral or organic surfaces and biological uptake, particularly by diatoms and algae (e.g., Dzombak & Morel 1990;Warren & Zimmerman 1994;Tessier et al 1996). These removal processes need to be understood and quantified before reliable predictions can be made concerning the extent to which metal toxicity will be reduced, and/or metals will accumulate in the sediments, in a natural aquatic system.…”