Metal/metalloid and phosphorus characteristics in porewater associated with manganese geochemistry: A case study in the Jiulong River Estuary, China. (December 2019)

• Record Type: Journal Article
• Authors: Pan, Feng; Liu, Huatai; Guo, Zhanrong; Cai, Yu; Fu, Yuyao; Wu, Jinye; Wang, Bo; Gao, Aiguo
• Is Part Of: Environmental pollution. Volume 255(2019)Part 1
• Publication Date: 2019-12
• Subjects: Peeper -- Heavy metal -- Metalloids -- Phosphorus -- Mn cycling -- Exchange flux; Pollution -- Periodicals; Pollution -- Environmental aspects -- Periodicals; Environmental Pollution -- Periodicals; Pollution -- Périodiques; Pollution -- Aspect de l'environnement -- Périodiques; Pollution -- Effets physiologiques -- Périodiques; Pollution; Pollution -- Environmental aspects; Periodicals; Electronic journals; 363.73
• DOI: 10.1016/j.envpol.2019.113134
• Languages: English
• ISSNs: 0269-7491

Abstract

Abstract: Sediment porewater can be an important source of contaminants in the overlying water, but the mechanisms of metal(loid) and phosphorus (P) remobilization remain to be investigated. In this study, high-resolution dialysis (HR-Peeper) and diffusive gradients in thin films (DGT) samplers were used to determine the porewater dissolved iron (Fe), manganese (Mn), cobalt (Co), chromium (Cr), vanadium (V), selenium (Se), arsenic (As), P and DGT-Labile S in coastal sediments in the Jiulong River Estuary (JRE), China. The results showed that high concentrations of dissolved Mn, Se and P were present in the overlying water, indicating potential water pollution with excessive amounts of Mn, Se and P. The dissolved Mn concentrations in the porewater were higher than the dissolved Fe concentrations, especially at submerged sites, demonstrating that Mn(III/IV) reduction is the dominant diagenetic pathway for organic carbon (OC) degradation, which directly affects Fe cycling by the competitive inhibition of Fe(III) reduction and Fe(II) reoxidation. Dissolved Co, Cr, V, Se, As and P show significant positive correlations with Mn but nearly no correlations with Fe, suggesting that the mobility of these metal(loid)s and P is associated with Mn but not Fe cycling in this region. In addition, the coelevated concentrations of the metal(loid)s, P and Mn at the submerged sites are attributed to the strengthened Mn reduction coupled with OC degradation fueled by hypoxia. The higher positive diffusion fluxes of Mn, Se and P were consistent with the excess Mn, Se and P concentrations in the overlying water, together with the approximately positive fluxes of the other metal(loid)s, indicating that sediment Mn(III/IV) reduction and concomitant metal(loid) and P remobilization might be vital pathways for metal(loid) and P migration to the overlying water. Graphical abstract: Image 1 Highlights: High-resolution dialysis is used to determine the metal(loid)s and P in porewater in situ. Mn reduction is the dominant diagenetic process rather than Fe reduction. The retention and remobilization of metal(loid)s are controlled by Mn cycling. Hypoxia is facilitated to the liberation of metal(loid)s and P via enhanced Mn reduction. The internal metal(loid) and P loading might be major sources for the overlying water. Abstract : The retention and remobilization of metal(loid)s and P are controlled by Mn cycling and the liberation of metal(loid)s and P fueled by hypoxia is a major source for the overlying water.