Leaching of Metals in Coastal Technosols Triggered by Saline Solutions and Labile Organic Matter Removal

Abstract

This study aims to understand the influence of salinity and labile organic matter removal on the fate and behavior of metals in coastal technosols. Two technosol cores were collected near the Lebanese shore. The cores were sectioned into layers; each layer was characterized for pH, salinity, electric conductivity, labile and total organic matter, grain size, and total and oxalate-extractable metals. Consequently, two saline solutions were used in desorption experiments to understand the role of ionic strength and labile organic matter on metal release. The results showed that the technosol layers were highly heterogeneous; most layers were enriched with Fe, Zn, Pb and Cu. The mineralogical investigations showed that the metals, notably Fe, were not present as crystalline minerals, rather big percentages of the metals were found in amorphous or poorly crystalline phases. Desorption experiment showed that Mg release was dependent on salinity and organic matter in both technosols, while Pb release was dependent on both factors only in one. Additionally, Zn and Cu were associated to organic matter, and their release was conditioned by the removal of labile organic matter; iron was primarily found as amorphous or poorly crystalline phases, and salinity had a major role in its release. The role of ionic strength and labile organic matter removal on the behavior of metals in technosols was demonstrated. Finally, understanding metal dynamics between the solid and liquid compartments in technosols, especially where salt deposition occurs, is important to reduce unwanted metal leaching to groundwater or seawater and transfer to biota.

Mineral and chemical changes of sediments after Cu sorption and then desorption induced by synthetic root exudate

“…The detectable and possibly exchangeable Cu bindings sites belong to organic matter, as reported by other studies (e.g. Kanbar et al, 2018;. Furthermore, the carbonyl moiety is considered as one of the critical sites for Cu mobility (Moon and Peacock, 2012).…”

A meta‐analysis of carbon content and stocks in Technosols and identification of the main governing factors

“…The third quartile (90.6 t C ha À1 ) is close to the mean. The maximum SOC* stock is 280 t C ha À1 ; it relates to an industrial soil (close to a steelmaking plant; Kanbar, Srouji, Zeidan, Chokr, & Matar, 2018). Eight data exceed 200 t C ha À1 over the 76 data (10.5%).…”