![]() ![]() We found that reducing annual water residence times shortened and weakened summer stratification. We used a systematic modelling approach to investigate the viability of changes to annual water residence time in affecting lake stratification and thermal dynamics in Elterwater, a small stratifying eutrophic lake in the northwest of England. However, residence time effects on stratification length in natural lakes are not well understood. A novel method to inhibit stratification by reducing residence times is proposed as a way of controlling the length of the hypolimnetic anoxic period, thus reducing the loading of nutrients from the sediments into the water column. In stratifying lakes, internal phosphorus loading is particularly problematic during the summer stratified period when anoxia persists in the hypolimnion, promoting phosphorus release from the sediment. Innovative methods to combat internal loading issues in eutrophic lakes are urgently needed to speed recovery and restore systems within legislative deadlines. Furthermore, the biological incubation experiments suggested that this variation of DOM property among tributaries would involve in the spatial dynamics of carbon dioxide (CO2) was emitted in TGR that more CO2 was emitted in the tributary of the front area than of the non-front area during the water-level declining period. Integrated with hydrological information, the results demonstrated that the density current exerts a significant influence on DOM dynamics. In particular, there was more terrestrial derived and biologically recalcitrant DOM in the river mouth than tributaries in the front area, while the opposite variation was observed in the non-front area. We found that the variation of DOM composition and property between tributary and river mouth sites show different patterns between front and non-front areas of TGR. Optical techniques and ultrahigh-resolution mass spectrometry were used to comprehensively explore the variation of DOM chemistry across TGR in the water-level declining period, and biological incubation experiments were conducted to trace its biogeochemical influences. Here, we investigated four tributaries across different segments (e.g., the front and non-front areas) of the world’s largest Three Gorges Reservoir (TGR). Although dissolved organic matter (DOM) is noted to involve in biogeochemical processes, the variation mechanism of DOM chemistry across a large-scale reservoir is not well assessed. Large-scale reservoirs exhibit complex hydrological conditions and exert a significant alteration on river flowing. Our research emphasizes the necessity of incorporating the effects of EM into studies of reservoir DOC removal and CO2 emissions. ![]() The modified CO2 flux was 0.75 Tg C/year, and respired DOC accounted for about 45% of total emitted CO2 from the 15 larger reservoirs. The accumulated efficiencies were estimated to be 13% for the selected 15 reservoirs throughout the Changjiang River network, corresponding to about 0.34 Tg C/year of the respired DOC. ![]() The contribution of respired DOC to daily CO2 emissions ranged from 17 to 61%. The values for DOC turnover velocity ranged from 0.10 to 1.59 m/day, and the average DOC turnover rate was 0.13 day⁻¹, with the average removal efficiency of 12%. Our study showed the nocturnal CO2 emission rate was about twice as high as in daytime, and was strongly driven by EM. Here, in-situ diurnal and monthly observations were conducted to measure EM (including gross primary production (GPP), ecosystem respiration (ER) and heterotrophic respiration (HR)), DOC turnover and CO2 emissions in a headwater catchment reservoir in Southeastern China in 2020. However, the effects of ecosystem metabolism (EM) on DOC cycling are not well known. Dam reservoirs in headwater catchments, as critical zones for their proximity to terrestrial sources, play important roles in dissolved organic carbon (DOC) cycling. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |