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Pollution levels and toxicity risks of heavy metals in different reed wetland soils following channel diversion in the Yellow River Delta

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  • Qiutang Wu, Yantai University, Chinese Academy of Sciences (CAS)
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  • Fuhua Bian, Yantai University
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  • Franziska Eller
  • Mengdi Wu, Chinese Academy of Sciences (CAS), Yantai University
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  • Guangxuan Han, Chinese Academy of Sciences (CAS), Chinese Academy of Sciences
  • ,
  • Junbao Yu, Ludong University
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  • Bo Guan, Chinese Academy of Sciences (CAS), Ludong University

The spatial distribution characteristics of soil elements in estuarine wetlands, which are important indicators for the health of estuaries, are affected by the dynamic changes of river flow paths. To reveal the differences of the spatial distribution characteristics of soil elements following channel diversion, we selected three typical reed (Phragmites australis) communities in the Yellow River Delta: the abandoned Yellow River course (OC): the reed community in the riparian zone of the old course of the Yellow River, which was diverted in 1996; the new Yellow River course (NC): the reed community on the current river bank; the intertidal area (TC): reed communities on tidal flats not affected by the Yellow River but frequently by tides. The soil properties and spatial distribution characteristics of 17 soil elements were analyzed, and the Geoaccumulation Index (Igeo), Enrichment Factor (EF), Toxin Units (TUs) and New Toxicity Index (TRI) were used to evaluate the ecotoxicity of heavy metals. The mean pH value followed the order TC site (8.05) > NC site (7.97) > OC site (7.87). The electrical conductivity at the NC site (4.10 mS cm−1) was significantly lower than at the OC site (6.46 mS cm−1) and TC site (6.86 mS cm−1) (p < 0.05). The mean concentrations of P, Mo, Fe, Zn, Cu, Cr, Ni and As in the surface soil (0–20 cm) at the NC site were lower than those at the OC site and TC site (p < 0.05). The results of vertical distribution of elements showed that the concentrations of most heavy metals at the OC and TC site decreased along the depth of the soil layers and the highest values appeared in the upper soil layers. While the NC site was different, the highest heavy metal concentrations were found in the lower soil layers. The values of Igeo indicated that Ni, As and Mo at the OC and TC site, and As and Hg at the NC site showed high toxicity risks. The EF values for Cu, Ni, As, Mo and Hg of all three sites exceeded 1.5, implying that these elements might come mostly from anthropogenic sources. In addition, Ni, As and Cr exhibited higher contribution ratios based on TRI values and ΣTUs. Meantime, the ΣTUs and TRI values indicated that the TC site had the highest, and the NC site had the lowest toxicity risk. The channel diversion increased the risk of soil pollution at the OC site. It is necessary to carry out long-term monitoring and control measures to avoid potential ecological damage.

StatusUdgivet - apr. 2022

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