Metal Release from Contaminated Estuarine Sediment Under pH Changes in the Marine Environment

Abstract

The contaminant release from estuarine sediment due to pH changes was investigated using a modified CEN/TS 14429 pH-dependence leaching test. The test is performed in the range of pH values of 0-14 using deionised water and seawater as leaching solutions. The experimental conditions mimic different circumstances of the marine environment due to the global acidification, carbon dioxide (CO2) leakages from carbon capture and sequestration technologies, and accidental chemical spills in seawater. Leaching test results using seawater as leaching solution show a better neutralisation capacity giving slightly lower metal leaching concentrations than when using deionised water. The contaminated sediment shows a low base-neutralisation capacity (BNCpH 12 = -0.44 eq/kg for deionised water and BNCpH 12 = -1.38 eq/kg for seawater) but a high acid-neutralisation capacity when using deionised water (ANCpH 4 = 3.58 eq/kg) and seawater (ANCpH 4 = 3.97 eq/kg). Experimental results are modelled with the Visual MINTEQ geochemical software to predict metal release from sediment using both leaching liquids. Surface adsorption to iron- and aluminium-(hydr)oxides was applied for all studied elements. The consideration of the metal-organic matter binding through the NICA-Donnan model and Stockholm Humic Model for lead and copper, respectively, improves the former metal release prediction. Modelled curves can be useful for the environmental impact assessment of seawater acidification due to its match with the experimental values.

Leaching behavior of major and trace elements from sludge deposits of a French vertical flow constructed wetland

“…The low alkaline and acidic neutralization capacity observed for the sludge deposits sample studied here was attributed to their high organic content (62.0 %, Table 1). Similar observations were reported by other authors for organic sediments or soil (Fang et al, 2016;Martin-Torre et al, 2015).…”

Distribution of Metals in the Waters and Sediments of Rivers in Central Amazon Region, Brazil

“…Increased TOC concentrations during flood periods was also observed in studies conducted for other rivers located in tropical forests, as well as in temperate regions and more northerly latitudes. [23][24][25] In these studies, alongside increased dissolved organic carbon (DOC) concentrations, higher concentrations were observed for lignin (Σ8), indicating that a direct relationship exists with the hydrological cycle. Indeed, during periods of flood, organic material leached from the surface layers of the soil due to the decomposition of leaf litter is incorporated.…”

“…More than 80% of the Pb concentration identified was in particulate form, which may be related to pH because Pb ions tend to form precipitates at pH 5-9. 25 In the rainy season, the concentrations were all lower than the quantification limit of the method employed (< 5.66 μg L -1 ) due to the high volume of the water. This finding reinforces the fact that the source of this element is punctual pertinent to the localities in question.…”

Tracing the Atmospheric Input of Seawater-Dissolvable Pb Based on the Budget of 210Pb in the East Sea (Japan Sea)

“…Diluted nitric or hydrochloric acid has been widely used to desorb Pb from the particles in precipitation. We believe that the leaching method could overestimate the atmospheric depositional flux of seawaterdissolvable Pb since the much lower pH in this process than the actual pH of seawater can affect the solubility of Pb (Chester et al, 2000;Martín-Torre et al, 2015). Our results suggest that the application of 210 Pb provides a useful tool to estimate the flux of actual seawater-dissolvable Pb in the ocean.…”