Solubility of Heavy Metals/Metalloid on Multi-Metal Contaminated Soil Samples from a Gold Ore Processing Area: Effects of Humic Substances

Abstract

Bioavailability of heavy metals at contaminated sites is largely controlled by the physicochemical properties of the environmental media such as dissolved organic matter, hydroxides and clay colloids, pH, soil cation exchange capacity and oxidation-reduction potential. The aim of this study was to investigate soil pH and heavy metal solubility effect by levels of humic and fulvic acids applied in soil samples with different levels of contamination by heavy metals. The soil samples used in this study were collected in a known metal-contaminated site. Humic acid (HA) and fulvic acid (FA) were purchased as a commercially available liquid material extracted from Leonardite. The experiment was carried out in a factorial scheme of 4 × (4 + 1), with four contaminated soil samples and four treatments, comprised of two levels of HA, two levels of FA and a control. The HA treatments increased the solubility of Cu, Zn, Ni, Cr, Cd, Pb, As and Ba from soils, while FA treatments decreased, thus raising or not their availability and mobility in soil. Humic acid concentration did not influence soil pH and FA decreased soil pH until 0.7 units. The initial heavy metal concentration in soil affects the magnitude of the processes involving humic substances. The lower releases of heavy metals by FA verified the importance of the complexation properties of organic compounds. These results appear to encourage the use of HA for increased plant-availability of heavy metals in remediation projects and the use of FA for decreased plant-availability of heavy metals at contaminated sites with a risk of introducing metals into the food chain.

Reducing soluble lead and cadmium in contaminated soils using dairy cattle waste based vermicompost

“…Their results also showed that Pb and Cd immobilized in co-precipitation complexes were similar to their adsorption. The result of this study corresponds to that suggested by Boechat et al (2016), where humic and fulvic acids substantially declined in selected heavy metals, including Pb and Cd. The soil sample used in this study exhibits different retention of Pb and Cd where Inceptisols retains Pb and Cd higher than Entisols, as indicated by the amount of soluble form of both metals (Figures 2 and 3).…”

Study on Pedological Soil Properties in the “Haneș” Mine Area for Its Remediation

“…On this line, few studies have investigated chitosan and humic acids (that are natural constituents of the soil) to extract heavy metals from highly heavy metal polluted soil (Kulikowska et al, 2015a;Boechat et al, 2016;Jiang et al, 2011;Meng et al, 2017;Gusiatin et al, 2017). Nowadays cheaper sources of humic substances are under research.…”

Do soil amendments used to improve agricultural productivity have consequences for soils contaminated with heavy metals?

“…The effect of organic matter on contaminant or nutrient availability is highly influenced by the different forms or fractions of organic matter. The reactivity of DOC is influenced by the proportion of fulvic and humic acids contained within it (Boechat et al, 2016). Fulvic acids (FA) are soluble at all pH conditions while humic acids (HA) are only soluble at alkaline pH values.…”