Geochemical processes controlling dissolved selenium in the Changjiang (Yangtze) Estuary and its adjacent waters
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Geochemical processes controlling dissolved selenium in the Changjiang (Yangtze) Estuary and its adjacent waters WU Xiaodan1, SONG Jinming1*, WU Bin1,2, LI Tiegang1, LI Xuegang1 1 2
Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China University of Chinese Academy of Sciences, Beijing 100049, China
Received 18 April 2013; accepted 13 September 2013 ©The Chinese Society of Oceanography and Springer-Verlag Berlin Heidelberg 2014
Abstract Dissolved selenium in the Changjiang (Yangtze) Estuary and its adjacent waters was determined by hydride generation atomic fluorescence spectrometry to elucidate the source, behavior in estuary, adsorption-desorption process and biological role. In surface water, Se(IV) concentration ranged 0.05–1.14 nmol/L and Se(VI) concentration varied 0.01–1.20 nmol/L, with the means of 0.76 and 0.49 nmol/L, respectively. In bottom water, Se(IV) content varied 0.03–0.27 nmol/L and Se(VI) content ranged 0.04–0.85 nmol/L, with the averages of 0.10 and 0.40 nmol/L, respectively. High level of Se(IV) was observed near the shore with a significant decrease towards the open sea, suggesting the continental input from the adjacent rivers. Large value of Se(VI) was found in bottom water, reflecting the release from suspended sediment. Besides, high value appeared in the same latitude of the Changjiang Estuary and Hangzhou Bay illustrated the effect of lateral mixing and the long-distance transport of selenium. Se(VI), more soluble, occupied higher percentage in aqueous environment. The presence of Se(IV) resulted from the degradation of residue and the reduction of Se(VI) under anaerobic condition. The positive relationship to suspended particulate material (SPM) and negative correlation to depth indicated that Se(IV) tended to be released from the high density particulate matter. Instead, Se(VI) content did not significantly relate to SPM since it generally formed inner-sphere complex to iron hydroxide. Se(IV) content negatively varied to salinity and largely depended on the freshwater dilution and physical mixing. While, Se(VI) level deviated from the dilution line due to the in situ biogeochemical process such as removal via phytoplankton uptake and inputs via organic matter regeneration. As the essential element, Se(IV) was confirmed more bioavailable to phytoplankton growth than Se(VI), and moreover, seemed to be more related to phosphorus than to nitrogen. Key words: dissolved selenium, distribution, geochemical behavior, Changjiang (Yangtze) Estuary Citation: Wu Xiaodan, Song Jinming, Wu Bin, Li Tiegang, Li Xuegang. 2014. Geochemical processes controlling dissolved selenium in the Changjiang (Yangtze) Estuary and its adjacent waters. Acta Oceanologica Sinica, 33(10): 19–29, doi: 10.1007/s13131-0140537-z
1 Introduction As the representative of metalloid and redox-sensitive element, selenium has attracted worldwide attention over the past decades. Selenium was discovered by Swedish Chemist Jons Jakob Berzelius in 1818, with the name derived from Greek word “selene” meaning “
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