Assessment of Calcium Nitrate Addition on the AVS Removal, Phosphorus Locking, and Pb Release in Sediment

Li, Lanmiao; Wu, Linjun; Huang, Yanchun; Li, Yintian; Liu, Chao; Li, Jun; Li, Naiwen

Assessment of Calcium Nitrate Addition on the AVS Removal, Phosphorus Locking, and Pb Release in Sediment

2021

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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