Coastal wetlands are hotspots for nitrogen(N)cycling,and crab burrowing is known to transform N in intertidal marsh soils.However,the underlying mechanisms remain unclear.This study conducted field experiments and use...Coastal wetlands are hotspots for nitrogen(N)cycling,and crab burrowing is known to transform N in intertidal marsh soils.However,the underlying mechanisms remain unclear.This study conducted field experiments and used indoor control test devices to investigate the seasonal response of nitrogen to crab disturbance at the sediment-water interface in coastal tidal flat wetlands.The results showed that crab disturbance exhibited significant seasonality with large seasonal differences in cave density and depth.Due to crab disturbance,nitrogen fuxes at the sediment-water interface were much greater in the box with crabs than in the box without crabs.In summer,NH-N showed a positive flux from the sediment to the overlying water,but NO2-N and NOg-N showed positive fluxes from the sediment to the overlying water only in early stages.In winter,NH-N showed a positive flux from the sediment to the overlying water,but NO-N and NO,-N both exhibited positive and negative fluxes.These results indicated that the presence of crab burrows can cause the aerobic layer to move downward by approximately 8-15 cm in summer and directly promote nitrification at the sediment surface.展开更多
The Lyapunov exponent spectrum is firstly applied in the analysis of pressure fluctuation of draft tube and calculated based on the time series of vibration in experiments for different situations. Results shows that ...The Lyapunov exponent spectrum is firstly applied in the analysis of pressure fluctuation of draft tube and calculated based on the time series of vibration in experiments for different situations. Results shows that the Lyapunov exponent spectrum varies with the setting of guide vane, So the Lyapunov exponent spectrum can be used to judge the pressure fluctuation of draft tube so as to timely adjust the setting of the guide vanes to reduce the damage caused by the vibration.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.52271273)the Open Foundation of the Key Laboratory of Ministry of Education for Coastal Disaster and Protection(Grant No.Z202201)。
文摘Coastal wetlands are hotspots for nitrogen(N)cycling,and crab burrowing is known to transform N in intertidal marsh soils.However,the underlying mechanisms remain unclear.This study conducted field experiments and used indoor control test devices to investigate the seasonal response of nitrogen to crab disturbance at the sediment-water interface in coastal tidal flat wetlands.The results showed that crab disturbance exhibited significant seasonality with large seasonal differences in cave density and depth.Due to crab disturbance,nitrogen fuxes at the sediment-water interface were much greater in the box with crabs than in the box without crabs.In summer,NH-N showed a positive flux from the sediment to the overlying water,but NO2-N and NOg-N showed positive fluxes from the sediment to the overlying water only in early stages.In winter,NH-N showed a positive flux from the sediment to the overlying water,but NO-N and NO,-N both exhibited positive and negative fluxes.These results indicated that the presence of crab burrows can cause the aerobic layer to move downward by approximately 8-15 cm in summer and directly promote nitrification at the sediment surface.
基金supported by the Natural Science Foundation of Hebei Education Department (Grant No.2009422)
文摘The Lyapunov exponent spectrum is firstly applied in the analysis of pressure fluctuation of draft tube and calculated based on the time series of vibration in experiments for different situations. Results shows that the Lyapunov exponent spectrum varies with the setting of guide vane, So the Lyapunov exponent spectrum can be used to judge the pressure fluctuation of draft tube so as to timely adjust the setting of the guide vanes to reduce the damage caused by the vibration.
