Carbon and nitrogen stable isotopes are useful tracers for distinguishing marine and terrestrial plant sources of sedimentary organic matter(OM),and for identifying OM from different types of plants.By analyzing the c...Carbon and nitrogen stable isotopes are useful tracers for distinguishing marine and terrestrial plant sources of sedimentary organic matter(OM),and for identifying OM from different types of plants.By analyzing the carbon and nitrogen stable isotopes of marine and riverine sediments from Bohai Bay and its catchment,we were able to identify the source of OM in these sediments.The stable carbon isotope values of Bohai Bay sediments were between-22.94‰ and-23.90‰,while those of riverine sediments were from-24.45‰ to-32.50‰.Marine algae were the main source of OM in Bohai Bay sediments.However,lacustrine algae were the main source of riverine sediments,not terrestrial OM.The nitrogen isotopes in Bohai Bay sediments decreased in eastward direction,with increasing distance from the coastline,which suggested a higher degree of impact from human activities along the coast.展开更多
Sediment cores （-40-100 cm） were collected at 12 locations in the western Bohai Bay, the Haihe River estuary, the Yongding River estuary and the Tianjin Harbor, China, during 24-26 July 2007, and analyzed for ^7Be a...Sediment cores （-40-100 cm） were collected at 12 locations in the western Bohai Bay, the Haihe River estuary, the Yongding River estuary and the Tianjin Harbor, China, during 24-26 July 2007, and analyzed for ^7Be and ^210pb activities. Due to localized hydrodynamic patterns and frequent disturbance from dredging activities, steady-state sedimentation features were not observed in this study. As demonstrated in the VBe and ^210pb profiles, the temporal and spatial variations of these radionuclides support a non-steady state depositional environment in the study area. By comparing ^7Be and ^210pb inventories in the sediments with those of the atmospheric source, we found that： 1） sediments dredged from the Tianjin Harbor or eroded from nearby estuarine and coastal areas are retained in the western Bohai Bay for relatively short intervals （several months）, as reflected in the relatively high ^7Be inventories in the western Bohai Bay; 2） over the long-term （years to decades）, ^210Pb inventories in the sediments imply that there is a net on-shore transport of sediments, and the sediments are mass-balanced in the entire study area. Overall, our results suggest that the sediments are retained in the estuaries and the western Bohai Bay despite local variability in sediment dynamics and disturbance due to human activities.展开更多
基金Supported by the National Natural Science Foundation of China(No.41273068)the Tianjin Research Program of Applied Science and Advanced Technology(No.11JCZDJC24100)
文摘Carbon and nitrogen stable isotopes are useful tracers for distinguishing marine and terrestrial plant sources of sedimentary organic matter(OM),and for identifying OM from different types of plants.By analyzing the carbon and nitrogen stable isotopes of marine and riverine sediments from Bohai Bay and its catchment,we were able to identify the source of OM in these sediments.The stable carbon isotope values of Bohai Bay sediments were between-22.94‰ and-23.90‰,while those of riverine sediments were from-24.45‰ to-32.50‰.Marine algae were the main source of OM in Bohai Bay sediments.However,lacustrine algae were the main source of riverine sediments,not terrestrial OM.The nitrogen isotopes in Bohai Bay sediments decreased in eastward direction,with increasing distance from the coastline,which suggested a higher degree of impact from human activities along the coast.
基金Supported by the New Jersey Sea Grant (No. 6560-0000, H. Feng)the Tianjin Science and Technology Committee (No. 06YFGHHZ01500)
文摘Sediment cores （-40-100 cm） were collected at 12 locations in the western Bohai Bay, the Haihe River estuary, the Yongding River estuary and the Tianjin Harbor, China, during 24-26 July 2007, and analyzed for ^7Be and ^210pb activities. Due to localized hydrodynamic patterns and frequent disturbance from dredging activities, steady-state sedimentation features were not observed in this study. As demonstrated in the VBe and ^210pb profiles, the temporal and spatial variations of these radionuclides support a non-steady state depositional environment in the study area. By comparing ^7Be and ^210pb inventories in the sediments with those of the atmospheric source, we found that： 1） sediments dredged from the Tianjin Harbor or eroded from nearby estuarine and coastal areas are retained in the western Bohai Bay for relatively short intervals （several months）, as reflected in the relatively high ^7Be inventories in the western Bohai Bay; 2） over the long-term （years to decades）, ^210Pb inventories in the sediments imply that there is a net on-shore transport of sediments, and the sediments are mass-balanced in the entire study area. Overall, our results suggest that the sediments are retained in the estuaries and the western Bohai Bay despite local variability in sediment dynamics and disturbance due to human activities.
