Liu Cheng, Chen Kaining, Wang Zhaode, Fan Chengxin, Gu Xiaozhi, Huang Wei
State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, PR China; University of Chinese Academy of Sciences, Beijing 100049, PR China.
State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, PR China.
Environ Pollut. 2017 Oct;229:879-886. doi: 10.1016/j.envpol.2017.07.054. Epub 2017 Aug 1.
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 NH-N concentrations. In addition, NH-N concentrations in pore-water and NH-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 NH-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.
清淤已在浅水湖泊中广泛实施，以减少内部氮（N）负荷。来自污染河流的悬浮颗粒物（SPM）通常含有高浓度的氮，并最终沉积在河口附近的清淤沉积物表面。为了研究河流SPM对清淤后沉积物-水界面（SWI）氮交换的影响，在中国巢湖进行了一项为期360天的实验，比较了未清淤和清淤后的沉积物。清淤处理使沉积物中的总氮浓度显著增加（p < 0.01），而SPM的沉积对不稳定的NH-N浓度影响不大。此外，尽管有SPM的沉积，但清淤沉积物中孔隙水的NH-N浓度和NH-N通量显著低于未清淤的沉积物。清淤沉积物中的氧气产生速率和氧气穿透深度均高于未清淤的沉积物。清淤沉积物中硝化螺菌的增加与其SWI处NH-N浓度和通量的降低一致。因此，氧化条件、增加的氧气产生/消耗速率以及SWI处硝化螺菌的相对丰度被认为与清淤沉积物中低氮交换率相关。因此，在河口地区进行清淤以减少内部氮负荷是可行的，尽管在旨在实现长期内部氮负荷减少时应考虑河流SPM的影响。
