Temporal and spatial variation and risk assessment of soil heavy metal concentrations for water-level-fluctuating zones of the Three Gorges Reservoir
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This study aimed to reveal the temporal and spatial variation of soil heavy metal concentrations in the Three Gorges Reservoir area (TGR) water-level-fluctuating zone (WLFZ) and evaluated its pollution status and potential ecological risks and provide scientific basis for ecological risk prevention and ecological restoration of the TGR.
Materials and methods
This study was based on long-term monitoring of soil heavy metals (Cu, Pb, Cd, and Cr) before water level fluctuation (2008) and after 1 (2009), 4 (2012), or 7 (2015) cycles of water level fluctuation at the altitude of 155–172 m in the Wushan (WS) and Zigui (ZG) sections of the TGR, and pollution status and potential ecological risks of each heavy metal element were evaluated by index of geoaccumulation and potential ecological risk index.
Results and discussion
The Cd concentration increased with the increase in the number of reservoir water level fluctuations, whereas the concentrations of Cu, Cr, and Pb varied with the monitoring site. The Cd showed clear horizontal transfer characteristics. Moreover, with the increase of the frequency of water level fluctuations the Cd concentration at ZG (near the dam) were higher than those at WS (away from the dam). After 7 cycles of water level fluctuation, the concentrations of most soil heavy metal were not obvious differences between soil layers (except Pb). Before and after the reservoir water level fluctuation, Cd contamination level changed from pollution-free to strong or extremely polluted, Cu contamination level changed from pollution-free to moderately polluted, and Cr and Pb were pollution-free. Before the fluctuation of the reservoir water level, the potential ecological risk of Cd in the WS reached a classification of strongly polluted, whereas pollution at ZG was considered to be low level. However, after 4 cycles of water level fluctuation the Cd pollution level increased to a very high level, whereas Cu, Cr, and Pb remained consistently low.
There is an obvious temporal and spatial variation of heavy metal concentrations for WLFZ of TGR. Cd concentration increased with the increase in the number of reservoir water level fluctuations. Heavy metal concentrations changed from WS > ZG to WS < ZG after the impact of water level fluctuations. After 7 cycles of water level fluctuation, the distribution of heavy metals in different soil layers tends to be uniform (except Pb). Cd pollution is more serious, and there is a strong potential ecological risk.
KeywordsRisk assessment Soil heavy metal concentrations Temporal and spatial variation Three Gorges reservoir Water-level-fluctuating zone
Thanks to the graduate students Yi Kang and Nini Zhu who participated in part of the annual field survey and soil sample testing.
This work was supported by grant from the “12th Five-Year” National Science and technology support program for rural areas (2015BAD07B040301).
- Ao L, Lei B, Wang Y, Zhou X, Zhang S (2014a) Heavy metal risk assessment and sources distinguishing in town polluted river sediment at the Three Gorges Reservoir. J Beijing Univ Technol 40:444–450Google Scholar
- Ao L, Lei B, Wang Y, Zhou X, Zhang S (2014b) Sediment risk assessment and heavy metal source analysis in typical country water level fluctuated zone (WLFZ) of the Three Gorges. Environ Sci 35:179–185Google Scholar
- Gao B, Zhou HD, Huang Y, Wang Y, Gao J, Liu X (2014) Characteristics of heavy metals and Pb isotopic composition in sediments collected from the tributaries in Three Gorges Reservoir, China. Sci World J 2014:685834–685834Google Scholar
- Li SY, Zhang QF (2010) Risk assessment and seasonal variations of dissolved trace elements and heavy metals in the Upper Han River, China. J Hazard Mater 181(1–3):1051–1058Google Scholar
- McCauley A, Jones C, Jacobsen J (2009) Soil pH and organic matter. Nutr Manag Module 8:1–11Google Scholar
- Muller G (1969) Index of geoaccumulation in sediments of the Rhine River. Geo J 2(3):108–118Google Scholar
- Rinklebe J, Du Laing G (2011) Factors controlling the dynamics of trace metals in frequently flooded soils. Dynamics and bioavailability of heavy metals in the root zone. In: Selim HM (ed) Dynamics and Bioavailability of Heavy Metals in the Rootzone, pp 245–270Google Scholar
- Sayadi MH, Shabani M, Ahmadpoor N (2015a) Pollution index and ecological risk of heavy metals in the surface soils of Amir-Abad Area in Birjand City, Iran. Health. Scope 4(1):e21137Google Scholar
- Su C, Jiang LQ, Zhang WJ (2014) A review on heavy metal contamination in the soil worldwide: situation, impact and remediation techniques. Environ Skept Crit 3(2):24–38Google Scholar
- Tang J, Wang SJ, Fu SH, Sun YD, Lei JL (2008a) Soil environmental quality evaluation of the Three-Gorges Reservoir Region. Acta Pedol Sin 45:601–607Google Scholar
- Tang Q, Bao Y, He XB, Wen AB (2015) Heavy metal enrichment in the riparian sediments and soils of the Three Gorges Reservoir, China. Proc Int Assoc Hydrol Sci 367:244–250Google Scholar
- Wakida F, Lara-Ruiz D, Temores-Pena J, Rodriguez-Ventura J, Diaz C, Garcia-Flores E (2008) Heavy metals in sediments of the Tecate River, Mexico. Environ Geol 546:37–42Google Scholar
- Wang TJ, Yang QW, Pan J, Liu XL (2013) Change of heavy metals content in soil of water-level-fluctuating zone in Three Gorges Reservoir area. J Chongqing Jiao Tong Univ (Nat Sci) 32(3):472–474 (in Chinese with English Summary)Google Scholar
- Wang YC, Ao L, Lei B, Zhang S (2015) Assessment of heavy metal contamination from sediment and soil in the Riparian Zone China’s Three Gorges Reservoir. Orig Res 24(5):2253–2259Google Scholar
- Yang Q, Zhang Z, Zhang Z, An R, Hu H, Hu L, Wang C (2011) Temporal and spatial distribution of soil heavy metals in water-level-fluctuation zone of Xiaojiang watershed in Three Gorges Reservoir. J Hydroecol 32(2):11–16 (in Chinese with English summary)Google Scholar
- Zhang WJ, Jiang FB, Ou JF (2011) Global pesticide consumption and pollution: with China as a focus. Proc Int Acad Ecol Environ Sci 1(2):125–144Google Scholar
- Zhu NN, Guo QS, Qin AL, Pei SX, Ma FQ, Zhu L, Jian ZJ (2015) Plant community dynamics in the Hydro-fluctuation Belt of the Three Gorges Reservoir at the Zigui and Wushan Section, East of Fengjie County, China. Acta Ecol Sin 23:7852–7867 (in Chinese with English summary)Google Scholar