Binding and Mobilization of Heavy Metals in Contaminated Sediments Affected by pH and Redox Potential

Abstract

In a contaminated sediment from Hamburg harbour, acid production, mobilization of Cu, Zn, Pb, and Cd at different redox- and pH-conditions, and the transfer and change of those particle bound metals are studied. During oxidation the pH value in the sediment suspension decreases from about 7 to 3.4 because of the low acid neutralization capacity (ANC). This leads to a mobilization of heavy metals whereby Cd and Zn as distinguished from Cu and Pb are strongly released. Also a change in particulate phase specific heavy metal binding forms is found. Generally the easily and moderately reducible fractions increase during oxidation while the sulfidic fraction decreases. Also great changes were found for the dissolved Zn-and Cd-concentrations which increased continuously. The results show that at identical pH values obviously more metals are mobilized in the oxidized sediment than in the reduced state. But although the pH value is the key factor - in particular if it sinks below 4.5 - the redox conditions may also control the mobilization of certain metals. Consequently, also in well buffered sediments a mobilization of metals during oxidation cannot be excluded.

Assessment of sediment quality based on acid-volatile sulfide and simultaneously extracted metals in heavily industrialized area of Asaluyeh, Persian Gulf: concentrations, spatial distributions, and sediment bioavailability/toxicity

“…In the industrial area, the values of pH changed from 6.98 to 7.41 with an average value of 7.13 in autumn, and the corresponding data were 7.22-7.91 and 7.6 in autumn, respectively. pH is the dominating mobilizing factor for metals in sediments (Calmano et al 1993). It is reported that decomposition of organic matter may lead to decrease the value of pH due to the formation of humic acid (Nobi et al 2010) and consequently increase the metal release.…”

Oxidation of Dyeing Sludge in Supercritical Water

“…The leached amount of Cu, Pb, and Zn, which were 10.4mg/L, 1.6mg/L and 9.85mg/L respectively, greatly below the permitted limits of Chinese EPA standard [16]. It has been reported that heavy metals locked with silica matrix could be hardly leached out under natural environment [17]. Therefore, the SCWO treatment could remain heavy metals in stable tailings which greatly reduce the leachability of heavy metals.…”

Temporal variations and bioaccumulation of heavy metals in different Suaeda salsa marshes of the Yellow River estuary, China

“…However, Cu concentration did not increase with increasing salinity, which was probably due to the complex interactions of salinity and other environmental factors (such as sediment moisture and pH). A drop in pH prevents the transfer of most trace metals from the water phase to the sediment and/or causes desorption from the sediments (Calmano et al 1993). Samecka-Cymerman and Kenpers (2001) also found that the concentrations of heavy metals in water and soil were usually negatively correlated with pH.…”