Changes in water and soil metals in a Mediterranean restored marsh subject to different water management schemes

Abstract

Marsh restoration is an effective tool to remove water and soil metals via plant uptake and soil accumulation. However, few studies have attempted to quantify metal accumulation and removal in Mediterranean restored marshes. This study aimed to assess changes in water and soil metals in an oligohaline-restored marsh experiment that was set in an abandoned rice field for 3 years. Two freshwater-type treatments were tested: river irrigation water (IW) and rice field drainage water (DW), as well as three water level management schemes. Differences in water level schemes did not cause significant differences in metal removal and accumulation in soil marshes in either water type treatment. However, results showed that significantly higher Mn, Pb, and Zn input concentrations from DW allowed higher mean percentage of concentration reduction. Higher Cu concentration from IW also allowed higher Cu reduction (85%). Mean values of Co, Cr, Cu, Ni, Pb, V, and Zn in soil were higher in the IW treatment characterized by higher plant biomass, whereas mean accumulation rates of As, Ba, Cr, Cu, Ni, Pb, V, and Zn were higher in the DW treatment with higher accretion rates. Results suggest that wetland plants likely favored soil metal adsorption through soil oxygenation and highlight the utility of restored marshes as pollution filters in coastal wetlands with significant soil accretion and subject to relative sea level rise.