Mobilization and geochemistry of nutrients in sediment evaluated by diffusive gradients in thin films: Significance for lake management. (15th August 2021)

• Record Type: Journal Article
• Authors: Zhihao, Wu; Xia, Jiang; Shuhang, Wang; Li, Zhao; Lixin, Jiao; Junyi, Chen; Qing, Cai; Kun, Wang; Cheng, Yao
• Is Part Of: Journal of environmental management. Volume 292(2021)
• Publication Date: 2021-08-15
• Subjects: In-situ -- Denitrification -- Desorption -- Diffusion -- Phytoremediation; Environmental policy -- Periodicals; Environmental management -- Periodicals; Environment -- Periodicals; Ecology -- Periodicals; 363.705
• DOI: 10.1016/j.jenvman.2021.112770
• Languages: English
• ISSNs: 0301-4797

Abstract

Abstract: Investigation of in-situ mobilization of both nitrogen (N) and phosphate (PO4 3− ) in sediment is important for lake management strategy. In this paper, diffusion gradients in thin films (DGT) and DGT induced flux in sediments (DIFS) model are newly designed for in-situ measurement of iron (Fe), PO4 3−, nitrate (NO3 –N) and ammonium (NH4 –N), and nutrients' mobility in sediment in Lake Nanhu (China). According to DGT profiles together with physicochemical properties in sediment, (I) PO4 3− is released from (i) Fe-bound P plus loosely sorbed P in anoxic sediment and (ii) the loosely sorbed P in oxic sediment; (II) anoxic sediment inhibits nitrification and NO3 –N release, but it favors denitrification and dissimilatory nitrate reduction to ammonium (DNRA), leading to NH4 –N release; (III) Eh and organic matter are two key influence factors on mobility of PO4 3−, NO3 –N and NH4 –N. According to DIFS calculation, the dynamics of desorption and diffusion at two sites belong to (i) slow rate of resupply and (ii) fast resupply cases, respectively. Internal loadings are estimated to be 92.74 (PO4 3− ), 268.1 (NH4 –N) and −2466 kg a −1 (NO3 –N), which reflects sediment mainly acts as a source for PO4 3− and NH4 –N, and a sink for NO3 –N in water. Based on sediment P release risk index (SPRRI), P release risks in lake sediments are estimated, ranging from light to relative high level. DGT and SPRRI aid choice of restoration methods for sediment, including sediment dredging, phytoremediation and in-situ inactivation. Graphical abstract: Image 1 Highlights: DGT is firstly used for in-situ mobilization (PO4 3−, NH4 –N and NO3 –N) in sediment. The reductive dissolution of Fe (oxyhydr)oxides leads to sediment P release. Denitrification and DNRA account for NH4 –N release and sediment is a sink for NO3 –N. Eh and organic matter are key influence factors on NH4 –N and P release in sediment. Restoration methods for internal loading are proposed based on SPRRI index.