title: Oxygen microprofiles within the sediment-water interface studied by optode and its implication for aeration of polluted urban rivers.
abstract: To reveal the detailed vertical oxygen distribution at the sediment-water interface (SWI) and its relation with the oxygen consumption processes during and after aeration of polluted urban rivers, experimental systems constructed with collected sediment and in situ overlying water from a polluted urban river were aerated above or beneath the sediment-water interface 12 h a day for 15 days and left nonaerated for the following 10 days. The results showed that aeration of water or sediment both increased dissolved oxygen (DO) concentrations in the SWI, characterized by shifts in a "decrease-increase-decrease" manner during around 3 h for the aeration of water treatment (AW) and 6 h for the aeration of sediment treatment (AS). The oxygen penetration depth for AS experiments was between 0.66 and 4.16 mm with an average of 1.79 mm, significantly higher than that for AW experiments; however, the oxygen dissipation constant (mm-1) measuring the decay rate of DO near the SWI was greater for the AW experiments than the AS experiments. During the 10-day nonaeration period, the accumulation of nitrate in both the overlying water and sediment was greatly increased concomitantly with the higher oxygenation in AS experiments. From the nitrogen removal viewpoint, these results suggest that the SWI needs moderate oxygenation which enables nitrate and nitrite to be removed by denitrification rather than to be totally nitrified and accumulate as would result from the conventional practice by singly elevating DO concentrations.
authors.affiliation: School of Geography Science, Nantong University, Nantong, 226007, China.
authors.forename: Bo
authors.initials: B
authors.lastname: Liu
authors.affiliation: School of Environment, Nanjing Normal University, Nanjing, 210023, China. ruiming.han@njnu.edu.cn.
authors.forename: Rui-Ming
authors.initials: RM
authors.lastname: Han
authors.affiliation: Nanjing Institute of Environmental Sciences, Ministry of Environmental Protection, Nanjing, 210042, China. wangwenlin_jjl@126.com.
authors.forename: Wen-Lin
authors.initials: WL
authors.lastname: Wang
authors.affiliation: School of Geography Science, Nantong University, Nantong, 226007, China.
authors.forename: Hong
authors.initials: H
authors.lastname: Yao
authors.affiliation: School of Environment, Nanjing Normal University, Nanjing, 210023, China.
authors.forename: Feng
authors.initials: F
authors.lastname: Zhou
mesh_terms: D009584:Nitrogen; D010100:Oxygen; D045483:Rivers; D014867:Water; D014874:Water Pollutants, Chemical; D018508:Water Purification
chemical_list: D014874:Water Pollutants, Chemical; D014867:Water; D009584:Nitrogen; D010100:Oxygen
keywords: Aeration; Dissolved oxygen; Optode; Polluted urban river; Sediment-water interface