title: Composition and variability in the export of biogenic silica in the Changjiang River and the effect of Three Gorges Reservoir.
abstract: Silicon (Si) plays an essential role in biogeochemical processes, but is still poorly characterized in the river system. This study addressed the biogenic silica (BSi) composition, origin and variation in the Changjiang River, and estimated the impacts of natural processes and human activities on the river Si cycling. Our results indicate that phytoliths comprised 14%-64% of BSi, while diatoms accounted for 34%-85% of BSi. The Changjiang River transported 620Ggyr(-1) of BSi and 2100Ggyr(-1) of dissolved silicate (DSi) loadings, respectively; 55% of the BSi and 51% of the DSi fluxes are transported during the high discharge period from June to September. The Changjiang River carried phytolith BSi mostly comes from the middle and lower reaches area. The ratio of BSi/(BSi+DSi) has decreased from 0.47 before 1980 to 0.19 in 2013-2014 due to the direct retention of BSi. The BSi sedimentation in the Three Gorges Reservoir would cause a decrease of total reactive silica, but contribute to approximately 4%-16% of the DSi loading at the Jiangyin station due to its dissolution. This study demonstrates that phytoliths represent a significant contribution to the biogeochemical cycle of silica in coastal waters, and in-stream process exerts a great influence on the river Si loading and cycling.
authors.affiliation: Research Center for Marine Ecology, First Institute of Oceanography, State Oceanic Administration, Qingdao 266061, China; Department of Earth Sciences-Geochemistry, Faculty of Geosciences, Utrecht University, Utrecht, 3508, TA, The Netherlands. Electronic address: rxb@fio.org.cn.
authors.forename: Xiangbin
authors.initials: X
authors.lastname: Ran
authors.affiliation: Research Center for Marine Ecology, First Institute of Oceanography, State Oceanic Administration, Qingdao 266061, China; Tianjin Marine Environmental Monitoring Central Station, State Oceanic Administration, Tianjin 300450, China.
authors.forename: Sen
authors.initials: S
authors.lastname: Liu
authors.affiliation: Research Center for Marine Ecology, First Institute of Oceanography, State Oceanic Administration, Qingdao 266061, China; Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, Ocean University of China, Qingdao 266100, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Liu
authors.affiliation: Research Center for Marine Ecology, First Institute of Oceanography, State Oceanic Administration, Qingdao 266061, China.
authors.forename: Jiaye
authors.initials: J
authors.lastname: Zang
authors.affiliation: Research Center for Marine Ecology, First Institute of Oceanography, State Oceanic Administration, Qingdao 266061, China; Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, Ocean University of China, Qingdao 266100, China.
authors.forename: Hong
authors.initials: H
authors.lastname: Che
authors.affiliation: Research Center for Marine Ecology, First Institute of Oceanography, State Oceanic Administration, Qingdao 266061, China.
authors.forename: Yongxing
authors.initials: Y
authors.lastname: Ma
authors.affiliation: Research Center for Marine Ecology, First Institute of Oceanography, State Oceanic Administration, Qingdao 266061, China.
authors.forename: Yibin
authors.initials: Y
authors.lastname: Wang
mesh_terms: D002681:China; D017377:Diatoms / Q000378:metabolism; D004784:Environmental Monitoring; D019015:Geologic Sediments / Q000737:chemistry*; D045483:Rivers / Q000737:chemistry*; D012822:Silicon Dioxide / Q000032:analysis*
chemical_list: D012822:Silicon Dioxide
keywords: Biogenic silica; Changjiang River; Composition; Dissolution; Export