Comparative study on PCDD/F pollution in soil from the Antarctic, Arctic and Tibetan Plateau

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  • Science of the Total Environment 497498 (2014) 353359

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    Science of the Total Environment

    j ourna l homepage: www.e lsev ie r .com/ locate /sc i totenvComparative study on PCDD/F pollution in soil from the Antarctic, Arcticand Tibetan PlateauShenglan Jia a, Qiang Wang b, Li Li a, Xuekun Fang a,c, Yehong Shi d, Weiguang Xu a, Jianxin Hu a,a State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Collaborative Innovation Center for Regional Envi-ronmental Quality, Peking University, Beijing 100871, PR Chinab School of Chemistry and Chemical Engineering, Central South University, Changsha 410083, PR Chinac Norwegian Institute for Air Research, P.O. Box 100, 2027 Kjeller, Norwayd Beijing General Research Institute of Mining & Metallurgy, Beijing 100160, PR China

    H I G H L I G H T S

    The level of PCDD/Fs in soil at the Three Poles was reported. PCDD/F congener profiles in soil from the Three Poles were compared. Potential local and regional PCDD/F sources were conducted by FLEXPART simulation. Corresponding author. Tel.: +86 10 62756593.E-mail address: jianxin@pku.edu.cn (J. Hu).

    http://dx.doi.org/10.1016/j.scitotenv.2014.07.1090048-9697/ 2014 Elsevier B.V. All rights reserved.a b s t r a c ta r t i c l e i n f oArticle history:Received 24 April 2014Received in revised form 21 July 2014Accepted 28 July 2014Available online xxxx

    Editor: Adrian Covaci

    Keywords:PCDD/FsSoilThree PolesFLEXPART modelThe concentrations of polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) in 35 soil samplescollected from Fildes Peninsula in the Antarctic, Ny-lesund in the Arctic, and Zhangmu-Nyalam in the TibetanPlateau were reported in this study. A comparison of the total concentration and TEQ of PCDD/Fs at the ThreePoles was conducted. Both the total concentration and TEQ of PCDD/Fs demonstrates a decreasing trend inthe order of Zhangmu-Nyalam (mean: 26.22 pg/g, 0.37 pg I-TEQ/g) N Ny-lesund (mean: 9.97 pg/g,0.33 pg I-TEQ/g) N Fildes Peninsula (mean: 2.18 pg/g, 0.015 pg I-TEQ/g) (p b 0.05). In all samples, the congenerand homologue profiles dominated with higher (seven and eight) chlorinated PCDD/Fs (more than 85% of thetotal mass percentage of PCDD/Fs) at the Three Poles. Finally, a FLEXPART backward simulation was used topreliminarily identify the potential local and regional anthropogenic sources of PCDD/Fs. The results implythat the air masses passing over surrounding regions with significant PCDD/F emissions might contribute tothe occurrence of PCDD/Fs in both the Arctic and Tibetan Plateau.

    2014 Elsevier B.V. All rights reserved.1. Introduction

    Polychlorinated dibenzo-p-dioxins and polychlorinated dibenzo-furans (PCDD/Fs) are persistent organic pollutants (POPs) regulatedby the Stockholm Convention (http://chm.pops.int/TheConvention/ThePOPs/ListingofPOPs/tabid/2509/Default.aspx). They are uninten-tional byproducts of combustion and chlorinating processes duringboth natural and human activities, such as wildfire and waste incin-eration (USEPA, 2000). Among all 210 congeners, 17 PCDD/Fs withchlorines at the 2, 3, 7, and 8 positions are dioxin-toxic, and pose ahigh risk to ecological systems and human health due to severe ab-normality inductive, mutagenic, and carcinogenic effects (Wikoffet al., 2012). The Antarctic, the Arctic, and the Tibetan Plateau arecollectively referred to as Three Poles of the earth. They share thecommon characteristics of extremely harsh climate and fragile eco-systems. With few anthropogenic activities, the Three Poles wereonce thought to be free from man-made chemical contamination.There have been few reports of PCDD/Fs at the Three Poles, due tothe extreme environment and the expense of sampling. However,the available data suggest that PCDD/Fs occur at the Three Poles:PCDD/Fs in soil (2.484.30 pg/g dry weight) from the eastern TibetanPlateau were reported by Pan et al. (2013); PCDD/Fs were detectedin the blubber of ringed seals from the Arctic (0.6108.2 pg/g lipidweight) (Savinov et al., 2011); and PCDD/Fs in Antarctic penguinswere measured (772 pg/g wet weight) (Corsolini et al., 2007). Aslisted above, most available reports of PCDD/F levels were based onthe monitoring of biota and conducted to assess the ecological risk.However, because abiotic media are the transfer media and main re-ceptors of POPs, they can be used to investigate the potential sourcesand transportation pathways of POPs (Hale et al., 2006). Among thevarious abiotic environmental media, soil is one of the first points

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  • 354 S. Jia et al. / Science of the Total Environment 497498 (2014) 353359of entry of PCDD/Fs into terrestrial ecological systems (Carballeiraet al., 2006). We therefore selected soil to monitor PCDD/Fs in theThree Poles in this study. And the investigation of PCDD/F levels in soilfrom these regions could provide fundamental data for a range of aca-demic applications, such as assessing the local ecological risk of PCDD/Fs, as well as the effects of human disturbances on the environment.

    The identification of the potential PCDD/F sources of the Three Polesis essential for understanding the transport of PCDD/Fs. Previously,many studies have highlighted the importance of global long-rangetransport as the main source of POPs at the Three Poles (AMAP, 1998;Pienitz et al., 2004). For instance, Wania and his colleagues proposedthe theory of global fractionation, which posited that remote regionstended to accumulate POPs through long-range transfer (Wania andMackay, 1993;Wania, 2003). However, due to the increasing human ac-tivities at the Three Poles and the surrounding regions, the contribu-tions of those local and regional sources to the PCDD/F occurrencecan't be overlooked; thus, identifying the localized anthropogenicsources of PCDD/Fs at the Three Poles is needed. Simple backward tra-jectory models were often used to describe the neighboring sources ofPOPs at a simplified way (e.g., detailed atmospheric transport andchemical processes were ignored). The FLEXible PARTicle dispersionmodel (FLEXPART) considered not only atmospheric turbulence andconvection, but also chemical removal of POPs by hydroxyl (OH) radi-cals during the backward simulation. In the previous study, it has beensuccessfully applied in investigating the transport behavior ofpolychlorinated biphenyl (PCB) (Eckhardt et al., 2009).

    The soil samples from Fildes Peninsula in the Antarctic, Ny-lesundin the Arctic and Zhangmu-Nyalam in the Tibetan Plateau were collect-ed in this study. The concentrations of PCDD/Fs and the congener profileat the Three Poles were compared to maximize spatial variation over aglobal geographic range. The potential local and regional anthropogenicsources of PCDD/Fs in the sampling sites were then investigated using aFLEXPART simulation.2. Materials and methods

    2.1. Sample collection

    The sampling locations were Fildes Peninsula in the Antarctic, Ny-lesund in the Arctic, and Zhangmu-Nyalam in the Tibetan Plateau(Fig. 1).Fig. 1. Locations of sampling sites in (a) Ny-lesund,Fildes Peninsula is located onKingGeorge Island-the largest island ofthe South Shetland Islands and hosts nine scientific stations within theAntarctic Treaty System. The local temperature ranges from 20.3 to8.5 C with an average of 1.5 C. From December 2007 to January2008, fifteen topsoil (upper 5 cm) samples (62 S, 58 W) werecollected.

    Ny-lesund is the northernmost permanent settlement, and isinhabited by ca. 30 scientists and technicians. The region is influencedby polar cyclones and the North Atlantic Ocean circulation. The aver-age annual temperature is 5.1 C. From July to August in 2008, wecollected topsoil samples from 20 sampling sites (78 N, 12 E).

    There are approximately 6000 residents of the Zhangmu-Nyalamregion (28 N, 86 E), which includes both a warm and wet subtropicaltemperate zone, and a cold frigid zone. In September 2011, ninesampling sites were established from Zhangmu (located 2636 mabove sea level, on the south side of the Himalayas, with an annual av-erage temperature of 18 C) to Nyalam (located 5129m above sea level,on the north side of theHimalayas, with an average annual temperatureof 2.1 C, and a range of 19.1 to 22.1 C).2.2. Sample extraction/cleanup

    The soil samples were kept in aluminum foil and stored at 20 Cbefore extraction. Twenty-gram samples were freeze-dried, ground,passed through 80-mesh filters, and spiked with labeled standards asa recovery standard (13C-PCDD/Fs, Wellington Laboratories, Canada).They were then extracted five times by pressurized liquid extractionusing toluene at 150 C and 1500 psi (ASE-300, Dionex, USA). Thecrude extracts were concentrated by rotary evaporation, and thencleaned up with multi-step procedures, which included acid washing(98% H2SO4), multi-layer silica gel (from top to bottom in turn: 6 gNa2SO4, 0.9 g silica gel, 3 g basic silica gel with 3% KOH, 4.5 g acid silicagel with 44% H2SO4, 6 g acid silica gel with 22% H2SO4, 0.9 g silica geland 3 g silica gel with 10% AgNO3), gel permeation chromatography(Bio-Beads SX3, Bio-Rad, USA), and an activated carbondiatomitecolumn. The final volume of the samples was adjusted to 20 L byadding the internal standards (13C-1,2,3,4-TeCDD, Wellington Labo-ratories, Canada) before instrumental analysis.

    The reagents used in this study were pesticide-grade toluene,acetone, methylene chloride, decane, and hexane. Decane was ob-tained from Wako Pure Chemical Industries, Ltd. (Osaka, Japan),(b) Fildes Peninsula, and