Impact of sedimentation history for As distribution in Late Pleistocene-Holocene sediments in the Hetao Basin, China
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SEDIMENTS, SEC 2 • PHYSICAL AND BIOGEOCHEMICAL PROCESSES • RESEARCH ARTICLE
Impact of sedimentation history for As distribution in Late Pleistocene-Holocene sediments in the Hetao Basin, China Hongyan Wang 1 & Elisabeth Eiche 1 & Huaming Guo 2,3 & Stefan Norra 1 Received: 19 February 2020 / Accepted: 23 June 2020 # The Author(s) 2020
Abstract Purpose To understand the impact of geochemical sedimentation history for arsenic (As) distribution in the sediment profiles of the Hetao Basin, we (1) evaluated sediments provenance and variations of weathering intensities, (2) attempted to reconstruct the depositional environments, and (3) explored the As and Fe speciation in the sediments. Combining the information above, different sedimentation facies were distinguished in the vertical profiles. Methods Two sediments cores were drilled up to 80 m depth. Major and trace element compositions, including rare earth elements (REE), were analyzed. Carbon isotope ratios (δ13Corg) of embedded organic matter in the sediments were analyzed by isotope ratio mass spectrometry (IR-MS). Arsenic and Fe speciation of the sediments were determined by sequential extractions. Results and discussion The similar REE geochemistry of rocks from the Lang Mountains and sediments in the Hetao Basin indicated that the sediments originated from the Lang Mountains. The C/N ratio (~ 4 to ~ 10) in combination with δ13Corg (− 27‰ to −2 4‰) suggested that sediments were mainly deposited in aquatic environments. The unconfined aquifer equaled the lacustrine deposit with less intensive weathering during last glacial maximum (LGM). Here, the As content (average, 5.4 mg kg−1) was higher than in the aquifer sediments below (average, 3.6 mg kg−1). Conclusion Higher content of releasable As in combination with paleolake-derived organic matter aquifer sediments probably contributes to higher groundwater As concentration in the unconfined aquifer. This study provides the first insight into the impact of sedimentation history on As distributions in sediment profiles in the Hetao Basin. Keywords Sediment basin . Sedimentation history . Arsenic provenance . Weathering intensities . Organic carbon isotopic signature . Arsenic speciation
1 Introduction Responsible editor: Tomas Matys Grygar Electronic supplementary material The online version of this article (https://doi.org/10.1007/s11368-020-02703-2) contains supplementary material, which is available to authorized users. * Hongyan Wang [email protected] 1
Institute of Applied Geosciences (AGW), Geochemistry & Economic Geology group, Karlsruhe Institute of Technology (KIT), Adenauerring 20 b, 76131 Karlsruhe, Germany
2
State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Beijing 100083, People’s Republic of China
3
School of Water Resources and Environment, China University of Geosciences, Beijing 100083, People’s Republic of China
Geogenic groundwater arsenic (As) contamination is of global concern. It is mainly reported from floodplains in South and Southeast As
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