Nitrogen exchange across the sediment-water interface after dredging: The influence of contaminated riverine suspended particulate matter. (October 2017)

• Record Type: Journal Article
• Authors: Liu, Cheng; Chen, Kaining; Wang, Zhaode; Fan, Chengxin; Gu, Xiaozhi; Huang, Wei
• Is Part Of: Environmental pollution. Volume 229(2017)
• Page Start: 879
• Page End: 886
• Publication Date: 2017-10
• Subjects: Environmental dredging -- Nitrogen exchange -- Suspended particulate matter -- Sediment-water interface -- River mouth area; 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.2017.07.054
• Languages: English
• ISSNs: 0269-7491

Abstract

Abstract: Dredging has been widely implemented in shallow lakes to reduce internal nitrogen (N) loading. The suspended particulate matter (SPM) coming from polluted rivers usually contains high levels of N and ultimately deposits on the dredged sediment surfaces near the river mouth. To study the influence of the riverine SPM on N exchange across the sediment-water interface (SWI) after dredging, a 360-day experiment was carried out comparing un-dredged and dredged sediments from Lake Chaohu, China. Dredged treatments showed a significant increase ( p < 0.01) in total N concentrations in the sediments, while the deposition of SPM had little influence on labile NH4 + -N concentrations. In addition, NH4 + -N concentrations in pore-water and NH4 + -N fluxes were significantly lower in dredged than in un-dredged sediments, despite the deposition of SPM. The oxygen production rates and the oxygen penetration depth in the dredged sediments were both higher than those in the un-dredged sediments. The increase of Nitrospira in dredged sediments was consistent with their decreased NH4 + -N concentrations and fluxes across the SWI. Therefore, the oxidizing condition, increased oxygen production/consumption rates and Nitrospira relative abundance across the SWI were believed to be correlated with the low N exchange rates in dredged sediments. Dredging for reducing internal N loading in a river mouth area is therefore feasible, although the influence of the riverine SPM should be taken into account when aiming to achieve a long-term internal N loading reduction. Graphical abstract: Highlights: SPM accumulation increased TN concentration in the dredged sediment. SPM had little influence on the labile NH4 + -N concentration in the sediment. SPM had little impact on pore-water NH4 + -N concentration and flux from sediment. The oxic condition was significantly correlated with the N exchange across the SWI. Long-term reduction of internal N loading should take the SPM into account. Abstract : The deposition of riverine SPM significantly increased the nitrogen concentration in the dredged sediment, while had little influence on the ammonium flux from the sediment.