Characterization of dissolved organic matter from a restored urban marsh and its role in the mobilization of trace metals

Abstract

Dissolved organic matter (DOM), although highly variable and not very well characterized, plays a role in many important environmental reaction and transport processes, including trace metal mobilization. This study characterizes heterogeneous DOM from the pore-water of a restored urban tidal marsh, using chemical, optical, and electrochemical methods for dissolved organic carbon/nitrogen ratios (C:N: 1.8-6.4), spectroscopic characteristics (decreased aromaticity in amended sediments), element ratios (maximum sediment-associated trace metal concentrations measured<30 cm), and metal complexation properties (logKc: Cd: 10.7±0.7>Pb: 9.5±0.1>Cr: 7.3±0.1>Cu: 5.07±0.53), all as a function of sediment depth. Specific DOM properties from the restored marsh were then compared to pore-water samples from a natural marsh and a simulated wetland microcosm which resulted in similar values, while the reference humic acid significantly differed in properties from field DOM. The results revealed that reference humic acids do not accurately represent the complexity of natural heterogeneous DOM, whereas a simulated wetland microcosm may provide a reasonable representation of natural DOM. Clear differences between amended and original soil (transition below 30 cm) were observed in DOM and trace metal properties including: lower DOM content, higher logKc values, less DOM complexity, development of a iron-sulfide redox buffering pool, and greater affinity for metals in the solid phase occurring in the amended sediments.

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

“…This is a significant result, as the carboxyl and hydroxyl groups of humic substances are the most likely to react with cations. Therefore, FA should have a higher capacity for interactions with metals (Tang et al, 2014;Kulikowska et al, 2015;ElBishlawi and Jaffe, 2015); the corroborating results are shown in table 4.…”

Influence of Hydrological Perturbations and Riverbed Sediment Characteristics on Hyporheic Zone Respiration of CO2 and N2

“…Large dissolved CH 2 O (DOC) concentrations (0.6 and 1.6 mmol/L) were chosen for the top boundary condition of the model. Our two choices of top DOC boundary conditions are presented in Table 1 and represent previously published DOC values (0.6 mmol/L) (Trauth et al, 2014) and a maximum case representing highly labile autochthonous sources from benthic river systems (1.6 mmol/L) (Acuña et al, 2004;ElBishlawi & Jaffe, 2015;Flipo et al, 2004;Flipo, Rabouille, et al, 2007;Kaplan & Bott, 1982, 1989Mann & Wetzel, 1995;Wyatt et al, 2012). Bottom DOC concentrations were selected from Rivett et al (2008).…”

Trace metals, organic carbon and nutrients in the Beidagang Wetland Nature Reserve, northern China

“…There is a significant difference in theδ 15 N values between the sediment cores (ANOVA, P <0.05), while the TOC/TN ratios and δ 13 C values show no significant difference. Elemental ratios such as TOC/TN are commonly used to indicate the biodegradability of dissolved organic matter [ 22 , 23 ]. These results indicate that TOC is similarly degraded in each core, and TOC and TN did not originate from sewage discharge.…”

“…All these results suggest that sediment organic matter plays an important role in the sedimentary accumulation of Hg in wetland ecosystems. Although organic matter plays the most important role in the distribution of trace metals in sediments, its role is not well understood [ 23 ]. For example, Sanei and Goodarzi reported that the strong affinity between Hg and soluble organic matter is due not only to its chemical reactivity but also to the physical characteristics of these labile compounds [ 42 ].…”