Unexpected Heavy Metal Pollution in Wetland Soils Along the Yarlung Tsangbo River in Tibet, China: Assessment and Source
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Unexpected Heavy Metal Pollution in Wetland Soils Along the Yarlung Tsangbo River in Tibet, China: Assessment and Source Apportionment Zhongsheng Zhang
&
Qianjin Che & Zhenshan Xue
Received: 22 May 2020 / Accepted: 27 August 2020 # Springer Nature Switzerland AG 2020
Abstract The Qinghai-Tibetan Plateau (QTP), as the third pole, has recently experienced unexpected heavy metal pollution. However, few were available on heavy metal pollution and source apportionment in regions near South Asia, where the economy is currently experiencing rapid development. This paper evaluated heavy metal pollution in wetland soils along the Yarlung Tsangbo River (YTR), the largest river in the QTP. Results indicated minor contamination levels of Cu, Pb, Zn, Hg, As, Mn, and Cr. However, Cd pollution was serious and was the main pollutant. Nemero synthesis index values (PN) were relatively high and ranged from 4.54 to 10.47 caused by high loading from Cd and Zn. Roughly 92% Pb, 89% Cr, and 89% Mn were from natural sources while 86% Cd and 61% Zn were from anthropogenic sources in wetland soils along the YTR. Differences in heavy metal contents and sedimentation rates were accentuated by the metal accumulation rates of each site. Cd, Zn, and Hg accumulation rates were estimated to 0.966 mg m−2 year−1, 0.187 g m−2 year−1, and 0.061 mg m−2 year−1 in the 1800s and increased to 5.351 mg m −2 year −1 , 1.144 g m −2 year −1 , and 0.263 mg m−2 year−1 in the 2000s, respectively. This Z. Zhang (*) : Z. Xue Institute of Northeast Geography and Agroecology, Chinese Academy of Science, Changchun 130102, China e-mail: [email protected] Q. Che City and Plan College, Yancheng Normal University, Yancheng 224002, China
implied unexpected heavy metal pollution in wetland soils along the YTR basin and more attention should be paid to avoid the risk of heavy metal pollution here. Keywords Heavy metal . The Yarlung Tsangbo River . Tibet . Risk assessment . Source apportionment
1 Introduction The introduction of heavy metals into the environment originates from natural and anthropogenic sources. Natural sources, such as volcanism, bedrock weathering, and soil erosion, shape background values of heavy metals (Hamon et al. 2004; Li et al. 2014). Anthropogenic sources include metal emissions from agriculture fertilization (Xu et al. 2018), fuel consumption (Clark et al. 2002), mining (Smolders et al. 2003), and metal smelting and refining (Zhang et al. 2012). Heavy metal pollution has pervaded globally since the industrial revolution because metals were widely emitted into the environment via effluents, waste residue, and exhaust gas (Li et al. 2014). Recently, more and more research has reported unexpected heavy metal contaminations in biota of remote regions previously regarded as pure lands. For example, high heavy metal concentrations were observed in birds from the Sanjiang Plain (Wang et al. 2013), vascular plants from south Poland (Wojtun et al. 2017), crocodiles from South Africa (Du-Preez et al. 2016), and mammals from Greenland (Szefer et al. 200
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