TY - JOUR

T1 - Investigation of metal speciation in crude oil contaminated marine environments using a novel DGT technique

AU - Alkasbi, M.

AU - Pouran, H.

AU - Zhang, H.

PY - 2025/1/1

Y1 - 2025/1/1

N2 - Crude oil spills and discharges from refineries, mining, and industrial activities can introduce trace metals into marine environments. Determining trace metal concentrations and speciation in seawater is challenging due to the complex matrix and high salinity. This study developed a novel approach using modified diffusive gradients in thin-films (DGT) to measure labile concentrations and speciation of Co, Ni, Cu, Cd, Pb, and Zn in crude oil-contaminated seawater. Five DGT devices (open pore, restricted pore, 1000 and 3500 MWCO dialysis membranes, and Nafion 112) were tested. Results showed that crude oil impacts the lability and mobility of metals, with Nafion 112 excluding negatively charged complexes. Diffusion coefficients were measured in diffusive hydrogels, dialysis membranes, and Nafion using a diffusion cell. Metal speciation was investigated in synthetic seawater with 1 % and 4 % crude oil/water ratios (OWR). For Co, Ni, Zn, and Pb, similar labile concentrations across DGT devices indicated low molecular weight complexes dominated. Labile Cu decreased significantly with increased oil content, while other metals showed varying degrees of lability. The findings suggest that crude oil influences metal speciation through complexation with organic ligands, affecting their bioavailability in marine environments. Compared to measurements by equilibrium microdialysis, similar concentrations for Pb and Zn suggested their weak complexes with oil-soluble organic chemicals. However, microdialysis measured higher concentrations of Co, Cu, Ni, and Cd, indicating partially non-labile, low molecular weight complexes existed. Nafion 112 diffusion coefficients were 16–38 times lower than those in diffusive gel. Only free metal ions and potentially some positively charged inorganic/small organic complexes are likely to be measured by Nafion-DGT. This work has demonstrated that crude oil level and metal characteristics greatly influence metal speciation, and that small, labile organic complexes play a crucial role in controlling the mobility and availability of metals in oil-contaminated seawater.

AB - Crude oil spills and discharges from refineries, mining, and industrial activities can introduce trace metals into marine environments. Determining trace metal concentrations and speciation in seawater is challenging due to the complex matrix and high salinity. This study developed a novel approach using modified diffusive gradients in thin-films (DGT) to measure labile concentrations and speciation of Co, Ni, Cu, Cd, Pb, and Zn in crude oil-contaminated seawater. Five DGT devices (open pore, restricted pore, 1000 and 3500 MWCO dialysis membranes, and Nafion 112) were tested. Results showed that crude oil impacts the lability and mobility of metals, with Nafion 112 excluding negatively charged complexes. Diffusion coefficients were measured in diffusive hydrogels, dialysis membranes, and Nafion using a diffusion cell. Metal speciation was investigated in synthetic seawater with 1 % and 4 % crude oil/water ratios (OWR). For Co, Ni, Zn, and Pb, similar labile concentrations across DGT devices indicated low molecular weight complexes dominated. Labile Cu decreased significantly with increased oil content, while other metals showed varying degrees of lability. The findings suggest that crude oil influences metal speciation through complexation with organic ligands, affecting their bioavailability in marine environments. Compared to measurements by equilibrium microdialysis, similar concentrations for Pb and Zn suggested their weak complexes with oil-soluble organic chemicals. However, microdialysis measured higher concentrations of Co, Cu, Ni, and Cd, indicating partially non-labile, low molecular weight complexes existed. Nafion 112 diffusion coefficients were 16–38 times lower than those in diffusive gel. Only free metal ions and potentially some positively charged inorganic/small organic complexes are likely to be measured by Nafion-DGT. This work has demonstrated that crude oil level and metal characteristics greatly influence metal speciation, and that small, labile organic complexes play a crucial role in controlling the mobility and availability of metals in oil-contaminated seawater.

KW - Crude oil contamination

KW - Dialysis membrane

KW - Diffusive gradients in thin-films (DGT)

KW - Marine environment

KW - Nafion membrane

KW - Air quality

KW - Bioremediation

KW - Cobalt

KW - Copper

KW - Doping (additives)

KW - Electrodialysis

KW - Marine pollution

KW - Metal analysis

KW - Nickel

KW - Oil spills

KW - Seawater

KW - Synthetic metals

KW - Trace analysis

KW - Zinc

KW - Contaminated seawater

KW - Crude oil contaminations

KW - Diffusive gradient in thin-film

KW - Diffusive gradients in thin films

KW - Low molecular weight

KW - Metal speciation

KW - Nafions

KW - Thin-film devices

KW - Crude oil

KW - cadmium

KW - copper

KW - hydrogel

KW - lead

KW - metal ion

KW - nickel

KW - organic carbon

KW - petroleum

KW - resin

KW - sea water

KW - zinc

KW - complexation

KW - concentration (composition)

KW - crude oil

KW - element mobility

KW - industrial waste

KW - ligand

KW - marine environment

KW - marine pollution

KW - membrane

KW - metal

KW - mining

KW - oil spill

KW - pollution incidence

KW - pollution monitoring

KW - refining industry

KW - seawater

KW - speciation (chemistry)

KW - trace metal

KW - Article

KW - artifact

KW - bioavailability

KW - diffusion

KW - diffusive gradients in thin films

KW - microdialysis

KW - molecular weight

KW - pH

KW - photosynthesis

KW - salinity

KW - species differentiation

U2 - 10.1016/j.scitotenv.2024.178081

DO - 10.1016/j.scitotenv.2024.178081

M3 - Journal article

VL - 958

JO - Science of the Total Environment

JF - Science of the Total Environment

SN - 0048-9697

M1 - 178081

ER -