Biological carbon pumping(BCP)is a key process in which dissolved inorganic carbon in terrestrial aquatic ecosystems is utilized by aquatic autotrophs for photosynthesis and transformed into autochthonous organic matt...Biological carbon pumping(BCP)is a key process in which dissolved inorganic carbon in terrestrial aquatic ecosystems is utilized by aquatic autotrophs for photosynthesis and transformed into autochthonous organic matter(AOC).However,the mechanisms underlying BCP and the amount of generated AOC deposited effectively,are still poorly understood.Therefore,we conducted a systematic study combining modern hydrochemical monitoring and a sediment trap experiment in Fuxian Lake(Yunnan,SW China),the second-deepest plateau,oligotrophic freshwater lake in China.Temperature,pH,EC(electrical conductivity),DO(dissolved O2),[HCO3^-],[Ca^2+],SIc,partial CO2(pCO2)pressure,and carbon isotopic compositions of HCO3^-(δ^13CDIc)in water from Fuxian Lake all displayed distinct seasonal and vertical variations.This was especially apparent in an inverse correlation between pCO2 and DO,indicating that variations of hydrochemistry in the lake water were mainly controlled by the metabolism of the aquatic phototrophs.Furthermore,the lowest C/N ratios and highestδ^13Corg were recorded in the trap sediments.Analyses of the C/N ratio demonstrated that the proportions of AOC ranged from 30%to 100%of all OC,indicating that AOC was an important contributor to sedimentary organic matter(OC).It was calculated that the AOC flux in Fuxian Lake was 20.43 t C km^-2 in 2017.Therefore,AOC produced by carbonate weathering and aquatic photosynthesis could potentially be a significant carbon sink and may have an important contribution to solving the lack of carbon sinks in the global carbon cycle.展开更多
This paper studies the Stokes flow of micro-polar fluids by peristaltic pumping through the cylindrical tube under the effect of the slip boundary condition. The motion of the wall is governed by the sinusoidal wave e...This paper studies the Stokes flow of micro-polar fluids by peristaltic pumping through the cylindrical tube under the effect of the slip boundary condition. The motion of the wall is governed by the sinusoidal wave equation. The analytical and numerical solutions for the axial velocity, the micro-polar vector, the stream function, the pressure gradient, the friction force, and the mechanical efficiency are obtained by using the lu- brication theory under the low Reynolds number and long wavelength approximations. The impacts of the emerging parameters, such as the coupling number, the micro-polar parameter, the slip parameter on pumping characteristics, the friction force, the velocity profile, the mechanical efficiency, and the trapping phenomenon are depicted graphically. The numerical results infer that large pressure is required for peristaltic pumping when the coupling number is large, while opposite behaviors are found for the micro-polar parameter and the slip parameter. The size of the trapped bolus reduces with the increase in the coupling number and the micro-polar parameter, whereas it blows up with the increase in the slip parameter.展开更多
基金supported by the National Natural Science Foundation of China (Nos. 41430753, U1612441)
文摘Biological carbon pumping(BCP)is a key process in which dissolved inorganic carbon in terrestrial aquatic ecosystems is utilized by aquatic autotrophs for photosynthesis and transformed into autochthonous organic matter(AOC).However,the mechanisms underlying BCP and the amount of generated AOC deposited effectively,are still poorly understood.Therefore,we conducted a systematic study combining modern hydrochemical monitoring and a sediment trap experiment in Fuxian Lake(Yunnan,SW China),the second-deepest plateau,oligotrophic freshwater lake in China.Temperature,pH,EC(electrical conductivity),DO(dissolved O2),[HCO3^-],[Ca^2+],SIc,partial CO2(pCO2)pressure,and carbon isotopic compositions of HCO3^-(δ^13CDIc)in water from Fuxian Lake all displayed distinct seasonal and vertical variations.This was especially apparent in an inverse correlation between pCO2 and DO,indicating that variations of hydrochemistry in the lake water were mainly controlled by the metabolism of the aquatic phototrophs.Furthermore,the lowest C/N ratios and highestδ^13Corg were recorded in the trap sediments.Analyses of the C/N ratio demonstrated that the proportions of AOC ranged from 30%to 100%of all OC,indicating that AOC was an important contributor to sedimentary organic matter(OC).It was calculated that the AOC flux in Fuxian Lake was 20.43 t C km^-2 in 2017.Therefore,AOC produced by carbonate weathering and aquatic photosynthesis could potentially be a significant carbon sink and may have an important contribution to solving the lack of carbon sinks in the global carbon cycle.
文摘This paper studies the Stokes flow of micro-polar fluids by peristaltic pumping through the cylindrical tube under the effect of the slip boundary condition. The motion of the wall is governed by the sinusoidal wave equation. The analytical and numerical solutions for the axial velocity, the micro-polar vector, the stream function, the pressure gradient, the friction force, and the mechanical efficiency are obtained by using the lu- brication theory under the low Reynolds number and long wavelength approximations. The impacts of the emerging parameters, such as the coupling number, the micro-polar parameter, the slip parameter on pumping characteristics, the friction force, the velocity profile, the mechanical efficiency, and the trapping phenomenon are depicted graphically. The numerical results infer that large pressure is required for peristaltic pumping when the coupling number is large, while opposite behaviors are found for the micro-polar parameter and the slip parameter. The size of the trapped bolus reduces with the increase in the coupling number and the micro-polar parameter, whereas it blows up with the increase in the slip parameter.
