Assessment of Calcium Nitrate Addition on the AVS Removal, Phosphorus Locking, and Pb Release in Sediment
2021
Li, Lanmiao | Wu, Linjun | Huang, Yanchun | Li, Yintian | Liu, Chao | Li, Jun | Li, Naiwen
Recently, calcium nitrate (CN) has been widely used in contaminated sediments remediation. However, the release of NO₃⁻–N, NO₂⁻–N, and Pb into the overlying water accompanying with the addition of CN may cause a toxic threat to the water ecosystem. Herein, this study investigated the effect of CN addition dosages on the sediment remediation, including oxidation-reduction potential (ORP), acid-volatile sulfide (AVS), phosphorus, nitrogen, and Pb. Results showed that, with the increase of CN addition ratio from 0.5× to 2.0× (from 0.5 to 2.0 times the theoretical CN dosage, based on autotrophic sulfide-driven denitrification), the ORP, AVS, and Fe (II) removal rates had a significant improvement. Moreover, due to the abundant Ca²⁺ and the oxidization of Fe (II), it would make O–P transformed to Ca–P and Fe/Al–P, which lead to the locking of phosphorus in sediments. However, this study indicated that the more CN added, the more NO₃⁻–N, NO₂⁻–N, and Pb²⁺ released in the overlying water. In addition, the increase of exchangeable Pb and oxidizable fraction Pb in sediments were characterized, which had a positive correlation with CN dosages (p < 0.01). Thus, secondary pollution needs to be considered for sediment remediation, and adding nitrate directly into sediments may not be suitable for natural water bodies.
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