Hydrodynamic sorting controls the transport and hampers source identification of terrigenous organic matter: A case study in East China Sea inner shelf and its implication

Yinli Ji; Lijuan Feng; Dahai Zhang; Qianqian Wang; Gang Pan; Xianguo Li

doi:10.1016/j.scitotenv.2019.135699

Hydrodynamic sorting controls the transport and hampers source identification of terrigenous organic matter: A case study in East China Sea inner shelf and its implication

Sci Total Environ. 2020 Mar 1:706:135699. doi: 10.1016/j.scitotenv.2019.135699. Epub 2019 Nov 28.

Authors

Yinli Ji¹, Lijuan Feng¹, Dahai Zhang¹, Qianqian Wang¹, Gang Pan², Xianguo Li³

Affiliations

¹ Key Laboratory of Marine Chemistry Theory and Technology (Ocean University of China), Ministry of Education, Qingdao 266100, China.
² Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; School of Animal, Rural, and Environmental Sciences, Nottingham Trent University, Nottingham NG25 0QF, UK.
³ Key Laboratory of Marine Chemistry Theory and Technology (Ocean University of China), Ministry of Education, Qingdao 266100, China. Electronic address: lixg@ouc.edu.cn.

PMID: 31940724
DOI: 10.1016/j.scitotenv.2019.135699

Abstract

Transport of terrigenous organic matter (TerOM) in marginal seas plays an important role in marine carbon cycle which is closely related to global climate change. Suspended particulates in East China Sea (ECS) inner shelf are subject to strong influence of seasonally varied Zhe-Min Coastal Current (ZMCC) and Taiwan Warm Current (TWC). Transport of TerOM attached to the mineral particulates is therefore largely dependent on these hydrodynamic conditions. To address the transport pattern of TerOM in highly dynamic marginal seas and its implication, sediment samples were collected from ECS inner shelf and fractionated by water elutriation to simulate the hydrodynamic sorting process. Lignin phenols were determined for each fraction. The abundance of C phenols preferentially concentrated in the finer fractions, which is believed as a collective effect of hydrodynamic sorting, diagenetic reactivity and association preference of C phenols with finer sediments. In contrast to the expectation, sediments at the southernmost site did not have the highest mass percentage for the finest fraction, the lowest lignin abundance and the highest degradation status. Combining the results of lignin parameters with seawater temperature and salinity profiles, it is proposed that sediments are transported along the inner shelf southward in winter and northward in summer to some extent with the influence of seasonally varied ZMCC and TWC, induced by the seasonality of East Asia Monsoon (EAM). Finer grained sediments are more susceptible to this process. This transport pattern, which was only reported previously in ocean modeling, was firstly supported by the observation of lignin biomarkers. It is suggested that cross-shelf transport of sediments in ECS seems to be possible, but is complicated and is also affected by the seasonal variation of EAM. This study improved the understanding of hydrodynamic sorting on the transport of TerOM and carbon cycling in the marine system.

Keywords: East China Sea inner shelf; Hydrodynamic sorting; Lignin; Sediment transport; Water elutriation.