Fig. 1From: The synergistic effect of calcium on organic carbon sequestration to ferrihydriteSorption behavior of organic carbon to 2-line ferrihydrite: DOM (a) and citric acid (b) were reacted with ferrihydrite at pH 6.25 ± 0.10 in duplicate. Samples were treated with and without Ca addition. Sample receiving Ca had a total Ca concentration of 4 mM Ca (152 mg Ca L−1)Back to article page