Effect of water-sediment regulation of the Xiaolangdi reservoir on the concentrations, characteristics, and fluxes of suspended sediment and organic carbon in the Yellow River

Abstract

Water-sediment regulation (WSR) of the Xiaolangdi Reservoir in the Yellow River is different from other water conservancy projects, with sediment resuspending along the river downstream of the reservoir during water regulation while some suspended sediment depositing during sediment regulation. In this study, samples were collected before, during, and after WSR to investigate the effect of WSR on the suspended sediment and organic carbon downstream of the reservoir. The suspended sediment concentration ([SPS]) increased with the river flow velocity (V) as a power function ([SPS]=1.348V(2.519)) during the three periods. The suspended sediment grain size decreased along the river during water and sediment regulations and after WSR; they were generally below 200μm with the fine particles (<50μm) of 68.0%-93.7% and positively correlated with the flow velocity. The black carbon content in suspended sediment elevated along the river during both water and sediment regulations, and it increased with 2-50μm fraction during water regulation and with <2μm fraction during sediment regulation, suggesting that black carbon mainly exists in fine particles and is influenced by both suspended sediment source and characteristics. There was no significant difference in dissolved organic carbon (DOC) concentration during water regulation, sediment regulation, and after WSR, inferring that the effect of sediment resuspension/deposition on DOC concentration was insignificant. The contribution of DOC flux (27.3%) during WSR period to the annual flux was comparable to that (22.6%) of water, but lower than the sediment (32.5%) and particulate organic carbon (POC) (49.5%). This study suggests that WSR will exert significant influence on the concentrations, characteristics and fluxes of POC (p<0.05) and sediment (p<0.05) but have no significant influence on DOC (p>0.1) of the Yellow River.

Pollutants’ Release, Redistribution and Remediation of Black Smelly River Sediment Based on Re-Suspension and Deep Aeration of Sediment

“…The disturbance effect of the aeration influenced the peak release of the organic matter within 40 min. This is because part of the volatile organic compounds volatilized out of the water during the disturbance process, and a portion of the organic matter was oxidatively degraded [25]. …”

“…The ammonia nitrogen will be converted to nitrite nitrogen under aerobic conditions and further converted to nitrate nitrogen with sufficient oxygen, while the nitrite nitrogen will degrade to molecular nitrogen in anaerobic or anoxic conditions [25]. Figure 9 shows the change of DO during the intermittent and continuous aeration process.…”

How bacterioplankton community can go with cascade damming in the highly regulated Lancang–Mekong River Basin

“…Previous studies reported that the construction of large‐scale water conservancy projects can alter natural hydrological conditions and sediment transport processes downstream (Ruiz‐González et al., ; Xia et al., ). In consequence, upstream and downstream sites of the dam may differ remarkably in their physicochemical properties, which may further influence their bacterioplankton communities.…”

Enhanced nitrogen loss from rivers through coupled nitrification-denitrification caused by suspended sediment

“…Because agitation, simulating the river flow and causing the presence of SPS, would pose effects on the diffusion of nitrate from water to bed-sediment, the increased nitrate supply in bed-sediment was also caused by the agitation conditions in addition to the presence of SPS itself which accelerated the production of nitrate. Since SPS concentration also depends on hydrodynamic conditions including river flow velocity in natural rivers (Xia et al, 2016), the results obtained under different agitation rates in this study can reflect the effect of SPS concentration on N-loss from natural rivers.…”

“…In addition, according to the above results, the increased proportion of N loss caused by SPS reached 100% when SPS concentration increased to 1 g L -1 in the Yangtze River (TOC ≈ 0.64%). Approximately 46% of the rivers around the world has SPS concentration higher than 1 g L -1 (Xia et al, 2016), and the TOC content in most of these rivers are higher than that in the Yangtze River (Table S4), thus the nitrogen loss in these rivers might increase at least by one time due to the presence of SPS.…”