Effects of experimental CO₂ leakage on solubility and transport of seven trace metals in seawater and sediment

• Published in: The Science of the total environment Vol. 407; no. 24; pp. 6255 - 6266
• Main Authors: Ardelan, Murat V, Steinnes, Eiliv, Lierhagen, Syverin, Linde, Sven Ove
• Format: Journal Article
• Language: English
• Published: Netherlands [Amsterdam; New York]: Elsevier Science 01.12.2009
• Subjects: Aluminum - analysis; Cadmium - analysis; Carbon Dioxide - analysis; Chromium - analysis; Copper - analysis; Geologic Sediments - chemistry; Hydrogen-Ion Concentration; Lead - analysis; Metals, Heavy - analysis; Nickel - analysis; Partial Pressure; Seawater - chemistry; Water Pollutants, Chemical - analysis; Zinc - analysis
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2009.09.004

The impact of CO₂ leakage on solubility and distribution of trace metals in seawater and sediment has been studied in lab scale chambers. Seven metals (Al, Cr, Ni, Pb, Cd, Cu, and Zn) were investigated in membrane-filtered seawater samples, and DGT samplers were deployed in water and sediment during the experiment. During the first phase (16days), “dissolved” (<0.2µm) concentrations of all elements increased substantially in the water. The increase in dissolved fractions of Al, Cr, Ni, Cu, Zn, Cd and Pb in the CO₂ seepage chamber was respectively 5.1, 3.8, 4.5, 3.2, 1.4, 2.3 and 1.3 times higher than the dissolved concentrations of these metals in the control. During the second phase of the experiment (10days) with the same sediment but replenished seawater, the dissolved fractions of Al, Cr, Cd, and Zn were partly removed from the water column in the CO₂ chamber. DNi and DCu still increased but at reduced rates, while DPb increased faster than that was observed during the first phase. DGT-labile fractions (MeDGT) of all metals increased substantially during the first phase of CO₂ seepage. DGT-labile fractions of Al, Cr, Ni, Cu, Zn, Cd and Pb were respectively 7.9, 2.0, 3.6, 1.7, 2.1, 1.9 and 2.3 times higher in the CO₂ chamber than that of in the control chamber. AlDGT, CrDGT, NiDGT, and PbDGT continued to increase during the second phase of the experiment. There was no change in CdDGT during the second phase, while CuDGT and ZnDGT decreased by 30% and 25%, respectively in the CO₂ chamber. In the sediment pore water, DGT labile fractions of all the seven elements increased substantially in the CO₂ chamber. Our results show that CO₂ leakage affected the solubility, particle reactivity and transformation rates of the studied metals in sediment and at the sediment-water interface. The metal species released due to CO₂ acidification may have sufficiently long residence time in the seawater to affect bioavailability and toxicity of the metals to biota.