Human-induced changes in sediment properties and amplified endmember differences: Possible geological time markers in the future

Yang Yang; Jianjun Jia; Liang Zhou; Wenhua Gao; Benwei Shi; Zhanhai Li; Ya Ping Wang; Shu Gao

doi:10.1016/j.scitotenv.2019.01.115

Human-induced changes in sediment properties and amplified endmember differences: Possible geological time markers in the future

Sci Total Environ. 2019 Apr 15:661:63-74. doi: 10.1016/j.scitotenv.2019.01.115. Epub 2019 Jan 14.

Authors

Yang Yang¹, Jianjun Jia², Liang Zhou², Wenhua Gao³, Benwei Shi², Zhanhai Li², Ya Ping Wang², Shu Gao⁴

Affiliations

¹ State Key Laboratory for Estuarine and Coastal Research, East China Normal University, Shanghai 200062, China; Natural Resources Canada, Geological Survey of Canada, Bedford Institute of Oceanography, Dartmouth, NS, Canada.
² State Key Laboratory for Estuarine and Coastal Research, East China Normal University, Shanghai 200062, China.
³ Department of Environmental Science, Henan University, Kaifeng 475001, China.
⁴ State Key Laboratory for Estuarine and Coastal Research, East China Normal University, Shanghai 200062, China. Electronic address: sgao@sklec.ecnu.edu.cn.

PMID: 30665133
DOI: 10.1016/j.scitotenv.2019.01.115

Abstract

Many rivers are facing human-induced system regime shifts that have great environmental, ecological and social implications, necessitating an increasing need to quantify the human influence on sediment properties and their impacts on the source-to-sink system of marginal seas. The Huanghe and Changjiang Rivers have experienced a dramatic reduction in sediment flux in recent decades, typifying the human influence on sediment properties of global large rivers. Sediment samples from the two rivers were analyzed to obtain grain size, magnetic and geochemical data. The results show a large difference in sediment properties between pre- and post-dam periods. We applied a discrepancy factor to re-examine the magnetic and geochemical tracers that were previously used in the two rivers. The discrepancy factors of most magnetic and geochemical tracers in the mud-sized sediments of the two rivers increased by an average of about 109% after dam construction. This suggests that human-induced changes in sediment properties have greatly improved the discriminatory ability between the sediments from the two rivers. The results also raise the uncertainty of using previous tracers to distinguish between sediments from the two rivers after damming. Furthermore, significant changes in sediment properties that happened in a relatively short time may provide future geological time markers for sedimentary records with a temporal resolution of 10⁰-10¹ years. For marine environments, an approach for identifying sediment sources based on multiple independent optimum tracers is also proposed, with composite magnetic (SIRM vs. HIRM) and geochemical (Na₂O vs. Zn) tracers being considered. The results of this work can advance our knowledge of how human activities alter river systems, and identify a sustainable development model under system regime shifts for areas of high-intensity human activity.

Keywords: Geological time marker; Human activity; Sediment properties; System regime shifts; The Changjiang River; The Huanghe River.