An innovative coupling between column leaching and oxygen consumption tests to assess behavior of contaminated marine dredged sediments

Abstract

Contaminated dredged sediments are often considered hazardous wastes, so they have to be adequately managed to avoid leaching of pollutants. The mobility of inorganic contaminants is a major concern. Metal sulfides (mainly framboïdal pyrite, copper, and zinc sulfides) have been investigated in this study as an important reactive metal-bearing phase sensitive to atmospheric oxygen action. An oxygen consumption test (OC-Test) has been adapted to assess the reactivity of dredged sediments when exposed to atmospheric oxygen. An experimental column set-up has been developed allowing the coupling between leaching and oxygen consumption test to investigate the reactivity of the sediment. This reactivity, which consisted of sulfide oxidation, was found to occur for saturation degree between 60 and 90 % and until the 20th testing week, through significant sulfates releases. These latter were assumed to come from sulfide oxidation in the first step of the test, then probably from gypsum dissolution. Confrontation results of OC-Test and leachate quality shows that Cu was well correlated to sulfates releases, which in turn, leads to Ca and Mg dissolution (buffer effect). Cu, and mostly Zn, was associated to organic matter, phyllosilicates, and other minerals through organo-clay complexes. This research confirmed that the OC-Test, originally developed for mine tailings, could be a useful tool in the dredged sediment field which can allow for intrinsic characterization of reactivity of a material suspected to readily reacting with oxygen and for better understanding of geochemical processes that affect pollutants behavior, conversion, and transfer in the environment.

Feasibility of the reuse of total and processed contaminated marine sediments as fine aggregates in cemented mortars

“…Behavior of the total weathered sediment was previously assessed for reactivity. Oxidation still occurs despite the years of weathering, even if in circumneutral conditions the leaching of trace metals remains limited (Couvidat et al, 2015). However, previous studies on trace metal leachability have shown the high sensitivity of such dredged sediments to pH variations (Chatain et al, 2013b).…”

“…However, CSH phases covered with ettringite needles were observed in weathered mortar, and also in raw mortars despite the fact that those minerals were not detected by XRD. In this case, weathered aggregate contributes an extra content of gypsum (Table 2), and raw aggregate contains amorphous sulfides that are easily oxidizable to sulfates during curing (Couvidat et al, 2015). Hence, numerous sulfate phases were detected in raw mortars through XRD, but minerals were poorly identified (Table 4) (Matschei et al, 2007).…”

Stabilization/solidification of sediments: challenges and novelties

“…We will address specific issues and problematics of several classes of minerals, or particular minerals. Clays exhibit a specific affinity for trace metals and metalloids and interact with their mobility, as well as with organic matter to form clay-humic complex [32][33][34] . Carbonates regulate buffering power of sediments, influencing the local pH and ionic strength, as well as the mobility of trace metals and metalloids through various mechanisms (precipitation, co-precipitation, adsorption, absorption and substitution) [31,33,35].…”

Greening effect of concrete containing granulated blast-furnace slag composite cement: Is there an environmental impact?

“…It is more likely to be sporadically sprinkled with water by workers or rainfall. In this case, an innovative test could be developped, such as test that might account for column leaching but with a transient water regime, including dry phases, similar to those used in other fields as for marine sediments [24]. In the same way, the sprinkling leaching test was designed to fill a gap, since no surface dynamic test was found in literature.…”