The impact of preload on the mobilisation of multivalent trace metals in pyrite-rich sediment

Abstract

Trace metals occur at various concentrations in all wetlands. Their proliferation, chemical speciation, mobility and bioavailability are dependent on the redox potential (Eh), pH and the presence of organic and inorganic adsorption surfaces and co-precipitating metals. Consequently, changes in these key parameters have the potential to alter the fate of the dominant trace metal species in the sediment. An imposition of preload surcharge is a technique use in geotechnical engineering to improve in the strength and load carrying capacity of waterlogged sediments. The soil strength improvement is effected through the expulsion of porewater from the sediment. The imposition of surcharge over wetland sediments has the potential to create oxygen-deficient condition within the sediment, and cause pH, temperature, redox, EC and salinity changes in the sediment, which would impact on the mobilisation, chemical speciation, mobility and bioavailability of dominant toxic trace metals and their toxicity in the sediment. In the present work, a case study of the impact of preload surcharge on the proliferation, chemical speciation, mobilisation, mobility and bioavailability of arsenic, chromium, cobalt, copper and zinc in a naturally occurring pyrite-rich sediment is presented. The imposition of preload surcharge over the pyrite-rich sediment was accompanied by changes in the redox dynamics of the sediment, with multi-facet impact on the concentration, mobilisation and bioavailability of toxic trace metals, their redox transformation between oxidation states and on the toxicity within and outside the sediment environment.

An Ex-Situ Immobilization Experiment with Zn, Pb, and Cu in Dredged Marine Sediments from Bohai Bay, China

“…The mobility and bioavailability of a trace metal are largely dependent on its distribution within geochemical fractions. Generally, it increases as follows: F1 > F2 > F3 > F4 [52]. Among all three groups, the residual fraction is dominant in Zn, with a proportion of nearly 60%, while F1, F2, and F3 account for only about 15%, 15%, and 10%, respectively.…”

“…The mobility and bioavailability of metals depend largely on pH, EC, organic adsorption, and the ionic coprecipitation process; therefore, these crucial parameters have the potential to change the dominant metal fractions in sediment [52]. The variation of these properties (pH, EC, salinity, and TOC) in the sediment samples, with different amendments over the incubation experiment time, is shown in Figure 1.…”

The ex-situ immobilization experiment of heavy metals in dredged marine sediments from Bohai Bay, China

“…The mobility and bioavailability of heavy metals depend largely on pH, Eh, organic adsorption and ionic coprecipitation process, and therefore, these crucial parameters have the potential to change the dominant metal fractions in the sediment [52]. The variation of these properties (pH, EC, salinity and TOC) of sediment samples with different amendments over incubation experiment time is shown in Figure 1.…”

Trace Element Mobility during Corg-Enhanced Denitrification in Two Different Aquifers

“…These trace elements can often be incorporated into the mineral lattice of sulfides such as pyrite (FeS 2 ) [21]. In several aquifers the mobilization of trace elements from pyrite-rich sediments has been observed (e.g., [22][23][24]). In redox transition zones, sulfides are often present in the reduced section and (hydr)oxides in the oxidized section, so trace elements may be hosted by reduced mineral phases but also sorbed to (hydr)oxide surfaces [25,26].…”