Science of the Total Environment 409 (2011) 4063–4071

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Trends of lead and zinc in resident and transplanted Flavocetraria nivalis lichens neara former lead–zinc mine in West Greenland

Jens Søndergaard ⁎, Poul Johansen, Gert Asmund, Frank RigétDepartment of Arctic Environment, National Environmental Research Institute, Aarhus University, Frederiksborgvej 399, DK-4000 Roskilde, Denmark

⁎ Corresponding author. Tel.: +45 46 30 19 66.E-mail address: jens@dmu.dk (J. Søndergaard).

0048-9697/$ – see front matter © 2011 Elsevier B.V. Aldoi:10.1016/j.scitotenv.2011.06.054

a b s t r a c t

a r t i c l e i n f o

Article history:Received 10 January 2011Received in revised form 23 June 2011Accepted 24 June 2011Available online 22 July 2011

Keywords:Metal pollutionDust depositionLichensFlavocetraria nivalisTransplantationArctic

This study investigated spatial and temporal trends of lead (Pb) and zinc (Zn) in resident and transplantedFlavocetraria nivalis lichens near the former Black Angel Mine in Maarmorilik, West Greenland. The objectivesof the study were to evaluate resident and transplanted lichens for monitoring dust contamination andinvestigate trends in mine-related dust contamination near the mine. The mine operated between 1973 and1990 and lichens were regularly sampled between 1986 and 2009. When the mine operated, elevatedconcentrations of Pb, Zn and other elements were observed in resident lichens up to 35 km fromMaarmorilik.In the period after mine closure, Pb and Zn concentrations in resident lichens decreased with 1–11% and 0–6%per year, respectively. From 1996 to 2009, lichens were transplanted into the study area from anuncontaminated site and collected the following year. After 1 year, transplanted lichens showed elevatedconcentrations of Pb and Zn but contained consistently less Pb and Zn compared to resident lichens (24±23%and 63±37%, respectively). During the most recent sampling in 2009, transplanted lichens still showedsignificantly elevated Pb concentrations (up to a factor 270) within a distance of 20 km from Maarmorilik.Zinc concentrations were only significantly elevated at sites within 5 km from the mine. Time-seriesregression analyses showed no significant decreases in Pb and Zn in transplanted lichens at any of the sitesduring the period 1996–2009. In conclusion, our study showed that resident F. nivalis lichens could not beused to evaluate the recent annual dust contamination in Maarmorilik. Lichen transplants, however, wereconsidered adequate for assessing spatial and temporal trends in Pb and Zn contamination from recentlydeposited dust. The continuous dispersal of contaminated dust in Maarmorilik almost 20 years after mineclosure reveals a slow recovery from mining contamination in this arctic area.

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1. Introduction

Lichens are abundant in the Arctic region and are known asadequate monitors of air pollutants including metal-contaminateddust from mining activities (Riget et al., 2000; Bari et al. 2001; Naethand Wilkinson, 2008). Lichen's lack of roots, large surface area, longlife span and high ion exchange capacity enable their effectiveaccumulation of air pollutants (Naeth and Wilkinson, 2008). In arcticGreenland, the foliose lichen Flavocetraria nivalis (L.) Kärnefelt andThell (previously named Cetraria nivalis) is abundant and has a greatpotential for monitoring air pollutants (Riget et al., 2000, 2004).Sampling of resident lichens growing naturally in themonitoring area,however, may not always be adequate for monitoring recent (annual)changes in dust deposition of some elements (see Section 4.4). As analternative to sampling resident lichens, transplantation of lichensfrom an uncontaminated area into a monitoring area followed by acollection some time after is a method widely used for monitoring air

pollutants near cities, smelters or other anthropogenic pollutionsources (Carreras and Pignata, 2002; Spiro et al., 2004; Pacheco et al.2008). The application of transplanted lichens has the advantage thatthe exposure time of the lichens to contamination is known andtherefore a change in the lichen's element composition relative to theoriginal composition can be related to that period. Transplantedlichens may also be used instead of resident lichens due to a lack ofresident lichens in the monitoring area or if measurements of airpollutants at a specific height are desired (Cloquet et al., 2009).

The former Black Angel lead (Pb)–zinc (Zn)Mine inMaarmorilik inWest Greenland (Fig. 1) operated between 1973 and 1990 and themining activity caused significant contamination mainly of Pb and Znin the surrounding environment (Asmund, 1992; Larsen et al., 2001;Elberling et al., 2002). During the mining period, contamination by Pband Zn in the marine environment was caused mainly by dissolutionand dispersal of metals frommine tailings that were discharged into asmall partly-enclosed fiord Affarlikassaa. Another important source ofcontamination was dispersal of dust due to ore-crushing, handling ofconcentrates and from the waste rock dumps left on the steepmountain slopes of Black Angel Mountain. These waste rock dumpsinitially contained several hundred thousand tons of rock with

T17A

T37

T36

T30

T25T22

0 2.5 5 10 km

AFFARLIKASSAA

Greenland

51o 44’W

70o 53’N

T38

T17B

T10

T12E

T6

PERLERFIUP KANGERLUA

QAAMARUJUK

Ukkussissat

LT5

T12SW

Fig. 1.Map of Maarmorilik and the fiords Affarlikassaa, Qaamarujuk and Perlerfiup with the location of the sampling sites and waste rock dumps. Water is marked with dashed lines.The mining symbol marks the location of the camp area and the former ore treatment plant in Maarmorilik, the filled dots show the locations of the sampling sites (named Sites T6 toT38 and Site L) and the stars the locations of the waste rock dumps. The waste rock dump situated near Site T12SWwas moved to the extent possible in 1990 and 1991 as part of themine closure plan. The open squaremarks the location of the settlement Ukkussissat. The Island of Saatut lies approximately 40 km southwest ofMaarmorilik and Shades Øer 100 kmnorthwest of Maarmorilik.

4064 J. Søndergaard et al. / Science of the Total Environment 409 (2011) 4063–4071

elevated concentrations of Pb and Zn (Asmund, 1992). After the mineclosure in 1990, Pb concentrations in the water in Affarlikassaadecreased abruptly to near-ambient levels suggesting that little Pbwas subsequently dissolved from the mine tailings. Pb concentrationsin marine biota and sediment around Maarmorilik, however,decreased slowly after 1990 and seaweed and blue mussels werestill in 2008 contaminated by Pb within a distance of 12 km from themine (Søndergaard et al., 2011). This indicated that other sourcesthan the mine tailings have dominated as Pb (and Zn) contaminationsources since mine closure. Possible sources include dust particlesfrom the waste rock dumps and the camp/port area, re-deposition ofpreviously generated dust and outwash of dissolved and particle-bound Pb from waste rock dumps left on the mountain sides. Thiscalled for a detailed study of dust deposition in Maarmorilik, whichmay also serve as an important case-study of long-term recovery of adry arctic fiord area to Pb–Zn mining and highlight precautions forfuture mining activities.

Consequently, this study sought to characterize the dispersal ofmetal-contaminated dust during and after the past mining activity inMaarmorilik. As one part of the study, resident and transplantedF. nivalis lichens were evaluated as tools for monitoring dustcontamination. A second part of the study included an evaluation ofthe dust contamination in Maarmorilik from 1986 to 2009 byassessing temporal and spatial variations of Pb and Zn in residentand transplanted lichens in the area.

2. Site description

The former Black Angel Mine in Maarmorilik is located next to twofiords, Affarlikassaa and Qaamarujuk, in the inner part of theUummannaq Fiord complex in West Greenland (71°07′ N; 51°15′W) (Fig. 1). The settlement Ukkussissat is the nearest community,situated 25 km to the west of the mine and Uummannaq, the mainsettlement in the area, is situated 80 km to the south. The climate inthe area is arctic with maximum summer temperatures around 10 °Cand minimum winter temperatures below −30 °C. Precipitation inthe area is sparse, ~100 mm a year, which classifies the area as an

Arctic desert (Møller and Pedersen, 1973). Winds are dominated bystrong easterly winds coming from the Greenland Ice Sheet in thebottom of Qaamarujuk.

The name ‘Maarmorilik’ refers to a geologic formation of calciticand dolomiticmarble, up to 1200 m thick, which is part of the ArcheanFoxe-Rinkian mobile belt complex of North-East Canada and CentralWest Greenland (Escher and Pulvartaft, 1976). The MaarmorilikFormation includes many carbonate-hosted Pb–Zn ores primarilylocated in Black Angel Mountain. The name ‘Black Angel’ refers to apelite outcrop forming a dark angel-like figure high on a 1100 mmarble cliff face above Affarlikassaa. The massive ores, up to 30 mthick, consist of galena (PbS), sphalerite (ZnS) and pyrite (FeS2) withaccessory ore minerals such as pyrrhotite, chalcopyrite, tennantiteand arsenopyrite. Prior to mining, the Black Angel deposit consisted often major ore bodies, a total of 13.6×106 t, containing 4.0% Pb, 12.3%Zn and 29 ppm silver (Ag). Out of these, 11.2×106 t was mined in theperiod 1973–1990 by the mining company Greenex A/S (Thomassen,2003).

As part of the mining process, ore material was transported fromthe mine entrances at 600 m elevation by means of cable cars acrossAffarlikassaa to a flotation plant in Maarmorilik. Here, concentrateswere produced, loaded onto ships and transported to smelters inEurope. The mean annual production of Pb and Zn concentratesduring the period 1973–1990 was 33×103 and 129×103 t, respec-tively (Thomassen, 2003) . For ore treatment, conventional rod/ballmilling was applied to liberate Pb and Zn. This was followed by frothflotation to produce separate Pb and Zn concentrates plus a wasteproduct, tailings (Poling and Ellis, 1995). Permission for submarinedisposal of tailings was given to the mining company in 1973 andtailings were subsequently discharged directly into Affarlikassaa ataround 30 m depth. During mining, several waste rock dumps werecreated below the mine entrances in the Black Angel Mountain(Fig. 1). One of the most polluting of these waste rock dumps wassituated just across Affarlikassaa from Maarmorilik (Fig. 1, closest toT12SW) and was in 1990 and 1991 partly removed. The waste rockdump was affected by permafrost, which made the excavation verydifficult and therefore not all material was removed. Later, part of the

4065J. Søndergaard et al. / Science of the Total Environment 409 (2011) 4063–4071

waste rock was dumped on top of the tailings deposit in Affarlikassaaand the rest buried on land below a cover of marble/dolomite.

3. Methods and instrumentation

3.1. Sampling

F. nivalis lichens were sampled at a total of 14 sites in theMaarmorilik area (named Sites T6 to T38 and Site L; Fig. 1). Residentlichens were sampled in 1986, 1987, 1991, 1992, 1993, 1994, 1995,1996, 1997, 1998, 2002, 2005 and 2007 and transplanted lichens weresampled in 1997, 1999, 2002, 2005, 2008 and 2009. In addition,resident F. nivalis lichens were collected regularly from the Island ofSaatut, located 40 km southwest from Maarmorilik and from SchadesØer situated 100 km northwest from Maarmorilik. These lichens areconsidered unaffected by mining contamination from Maarmorilikand provide a reference to lichens sampled near the mine.

Resident lichens were collected as bulk samples within an area of100×100 m at the sampling sites. Fresh living lichens growing ondead organic matter were collected while lichens growing directly onsoil or rocks were excluded. This was done to maximize theprobability that metals accumulating in the lichens originated fromdeposition of dust from the air and not from underlying soil or rocks.However, some uptake of particles in resident lichens from soil orrocks cannot be ruled out as F. nivalis is a vagrant lichen, which tosome extent blows around on the ground.

Lichens for transplantation were collected either at Saatut orSchades Øer and placed at the sampling sites near Maarmorilik. At thesampling sites, transplanted lichens were placed on the ground onorganic matter and covered with a 1×1 cm mesh nylon net held inplace by some flat pieces of rock. This was done to avoid the removalof the lichens by the wind. Usually, three 15×15 cm patches of lichenswere made at each site. The following year, transplanted lichenswere collected at the sites except for lichens transplanted in 2000that were collected 2 years after. The same spots were used forlichen transplants every year. When sampling, lichens were collectedin polyethylene or paper bags. Transplanted lichens from the threepatches were pooled together as a bulk sample. Later, in thelaboratory, lichen samples were sorted using stainless steel tweezersand only the green/yellow thalli were kept and subsequently dried at60 °C for 24 h. The weights of the bulk samples of both resident andtransplanted lichens after sorting and drying were usually 2–3 g. Thelichens were not washed in order to avoid the leaching of solublesubstances (Carreras and Pignata, 2002).

3.2. Chemical analyses

Sub-samples (300 mg) of the lichen bulk samples were taken anddigested using 4 mL Merck Suprapure HNO3 and 4 mL milliQ water inTeflon bombs under pressure in a microwave oven (Anton PaarMultiwave 3000). The lichen bulk samples were lightly crushed byhand within the polyethylene bags before the sub-samples weretaken out. One sub-sample from each bulk sample was analyzed inlichens sampled from 1986 to 2008. In samples from 2009, three sub-samples of the bulk samples were analyzed. The analyses weregenerally performed the same year the sampling took place. Afterdigestion, solutions were transferred to polyethylene bottles withmilliQ water and element analyses were performed directly on thesesolutions. From 1986 to 2008, Pb and Zn concentrations weredetermined either using a flame AAS (Perkin-Elmer 3030) or agraphite furnace AAS (Perkin-Elmer Zeeman 3030) at the NationalEnvironmental Research Institute (NERI) in Denmark. In 2009,analyses of Pb, Zn, Cu, Ni, Cr, As, Ag, Cd, Hg, Ca, Mg, Fe and Al weredetermined using an Agilent 7500ce ICP-MS. The analytical methodshave been described in more detail in Asmund et al. (2004) and theanalytical quality was continuously checked by analyzing blanks and

duplicates as well as a number of biological certified referencematerials including TORT, DORM and DOLT from the NationalResearch Council Canada (www.nrc-cnrc.gc.ca). The laboratory atNERI is accredited for analyses of Pb, Zn, Cu, Ni, Cr, As, Cd and Hg inbiota with precisions (2 standard deviations (SD)) of 15–20% andparticipates biannually in the international laboratory intercalibrationprogram QUASIMEME organized by the European Union (www.quasimeme.org). In addition to the quantitative analyses, isotopicratios of Pb (207Pb/206Pb) were analyzed in a few selected samplesalso using the Agilent 7500ce ICP-MS. The method for Pb isotopemeasurements has previous been described in detail in Søndergaardet al. (2010) and the analytical precision (2 SD on 3 replicatemeasurements) is typically b1% on the 207Pb/206Pb ratio. Theanalytical results for all samples are provided in the Supplementarydata section.

3.3. Statistics

Differences in element concentrations in lichens before and aftertransplantation and in resident lichens collected near Maarmorilikversus in uncontaminated lichens from Saatut or Schades Øer weretested statistically using two-tailed two-sample t-tests and a signifi-cance level of 5%. Prior to the t-tests datawere tested for equal varianceswith an F-test.

Time trends of Pb and Zn in resident and transplanted lichens wereinvestigated statistically following the ICES (International Council forthe Exploration of the Sea) temporal trend assessment procedure(Nicholsen et al., 1995). At 4 of the 14 sites (Site T5, T10, T37 and T38),transplanted lichens were only sampled in 2009 and no temporal trendanalyses couldbemade. Toperform the temporal trend analysis, the log-mean concentration was used as the annual index value and the totalvariation over time was partitioned into a linear and non-linearcomponent. Linear regression analysis was applied to describe thelinear component and a LOESS smoother (locally weighted quadraticleast-squares regression smoothing) with a window width of 7 yearswas applied to describe the non-linear component. The linear and non-linear components were tested by an analysis of variance. The theorybehind the use of smoothers in temporal trend analyses is described indetail by Fryer and Nicholson (1999). A significance level of 5% wasapplied.

4. Results and discussion

4.1. Element contamination in lichens in Maarmorilik

The past mining activity in Maarmorilik had a profound impact onthe composition of elements found in F. nivalis lichens in thesurrounding area and remains from the mining period still affectlichens almost 20 years after mine closure. This is illustrated inTable 1, which shows the elemental composition in lichens before andafter 1 year of transplantation at the sampling sites in Maarmorilikduring 2008–2009. Sites are sorted with decreasing distances to themine.

After 1 year of transplantation, Pb and Zn concentrations werestatistically significantly elevated (two-tailed two-sample t-tests;pb0.05) and up to 270 and 16 times higher, respectively, close to themine. Also concentrations of cadmium (Cd), copper (Cu), calcium (Ca)and magnesium (Mg) were significantly elevated at sites adjacent tothe mine. Elements such as nickel (Ni), chromium (Cr), arsenic (As),silver (Ag), mercury (Hg), iron (Fe) and aluminum (Al) were notsignificantly changed in the lichens after transplantation. The highestconcentrations of Pb, Zn, Cd, Cu, Ca and Mg were measured atSites T12SW and T10 situated closest to the former waste rock dumparea. Although no studies were conducted on the natural elementconcentrations in lichens at the sampling sites prior to mining,the elevated Pb, Zn, Cd, and Cu concentrations in lichens after

Table 1Chemical composition of uncontaminated lichens collected at the Island of Saatut in 2008 and in similar lichens after 12 months of transplantation to sampling sites in Maarmorilik collected in 2009 (n=3). The sampling sites in Maarmorilik(Fig. 1) are sorted with decreasing distance to the mine. An * symbol indicates that the element was statistically significantly elevated at the 5% level after transplantation (two-tailed two-sample t-test).

Element Pb Zn Cu Ni Cr As Ag Cd Hg Ca Mg Fe Al Zn/Pb 207Pb/206Pb

Unit (kg−1

dry wt.)mg mg mg mg mg mg mg mg mg g g g g – –

Detectionlimit (d.l.)a

0.04 0.2 0.08 0.1 0.06 0.2 0.036 0.03 0.13 0.03 0.0002 0.02 0.004 – –

Site kmb Mean SD Mean SD Mean SD Mean SD Mean SD Mean SD Mean SD Mean SD Mean SD Mean SD Mean SD Mean SD Mean SD Mean SD Mean SD

Before transplantationSaatut 40 0.4 0.1 14 3 1.2 0.4 1.2 0.4 1.4 0.7 bd.l. – bd.l. – 0.06 0.04 bd.l. – 6.1 0.5 1.5 0.2 0.34 0.17 0.46 0.23 32.5 4.3 0.793 0.009

After 12 months of transplantationL 35 0.4 0.1 16 1 1.2 0.1 2.0 0.3 2.0 0.3 bd.l. – bd.l. – 0.07 0.01 bd.l – 4.9 0.4 1.7 0.1 0.37 0.05 0.50 0.07 37.4 5.7 0.828 0.034T38 23 0.5 0.1 15 1 1.2 0.2 1.3 0.1 1.4 0.3 bd.l. – bd.l. – 0.10 0.01 bd.l. – 5.8 0.9 1.6 0.2 0.36 0.09 0.35 0.08 27.5 5.7 0.828 0.021T37 20 1.8* 0.1 14 1 1.5 0.0 1.7 0.2 1.9 0.4 bd.l. – bd.l. – 0.14 0.02 bd.l. – 10.6* 1.0 1.6 0.1 0.53 0.06 0.45 0.07 8.0 0.6 0.880 0.023T36 12 1.0* 0.1 18 2 1.1 0.1 1.3 0.2 1.2 0.1 bd.l. – bd.l. – 0.12 0.02 bd.l. – 11.8* 1.0 1.6 0.1 0.35 0.04 0.37 0.05 17.4 1.8 0.896 0.016T30 5 1.7* 0.0 20* 1 1.2 0.2 1.5 0.3 1.2 0.3 bd.l. – bd.l. – 0.16 0.03 bd.l. – 8.3* 0.7 1.5 0.1 0.38 0.08 0.42 0.08 11.6 1.1 0.908 0.006T25 5 2.1* 0.3 20* 2 1.3 0.3 1.5 0.3 1.7 0.6 bd.l. – bd.l. – 0.14 0.02 bd.l. – 16.4* 0.2 1.8* 0.1 0.37 0.09 0.38 0.08 9.5 1.8 0.915 0.001T6 3 1.7* 0.6 28* 3 1.5 0.4 2.0 0.6 1.9 1.0 bd.l. – bd.l. – 0.11 0.00 bd.l. – 9.9* 1.2 2.0* 0.3 0.48 0.19 0.49 0.15 16.1 3.7 0.920 0.012T5 3 2.8* 0.2 27* 1 1.3 0.4 1.8 0.5 2.0 1.0 bd.l. – bd.l. – 0.11 0.03 bd.l. – 8.8* 0.5 2.3* 0.1 0.58 0.20 0.54 0.10 9.7 0.3 0.917 0.011T17B 2 6.9* 0.1 29* 3 1.5 0.3 1.2 0.5 1.2 0.6 bd.l. – bd.l. – 0.16 0.00 bd.l. – 7.4* 0.5 1.6 0.1 0.39 0.13 0.49 0.17 4.2 0.4 0.937 0.004T17A 2 2.9* 0.7 20* 1 1.5 0.5 1.6 0.7 1.6 0.8 bd.l. – bd.l. – 0.17 0.02 bd.l. – 6.8* 0.8 1.9 0.4 0.45 0.25 0.52 0.22 7.0 2.0 0.925 0.015T22 b1 21* 3 32* 5 1.2 0.3 1.1 0.6 1.2 0.8 bd.l. – bd.l. – 0.20* 0.01 bd.l. – 8.0* 0.4 1.7 0.4 0.38 0.22 0.48 0.29 1.5 0.0 0.884 0.019T12E b1 30* 4 89* 19 1.7 0.5 2.1 0.9 2.6 1.4 bd.l. – bd.l. – 0.60* 0.09 bd.l. – 14.5* 1.6 2.6* 0.5 0.61 0.26 0.67 0.32 3.0 0.4 0.952 0.001T10 b1 119* 6 183* 24 2.3* 0.5 1.2 0.3 1.1 0.4 bd.l. 0.054 0.007 1.41* 0.06 bd.l. – 29.0* 1.4 2.5* 0.2 0.59 0.19 0.51 0.19 1.5 0.2 0.953 0.002T12SW b1 73* 2 225* 21 1.6 0.3 1.4 0.2 1.1 0.1 bd.l. – bd.l. – 1.37* 0.08 bd.l. – 13.2* 0.8 2.4* 0.1 0.37 0.03 0.40 0.02 3.1 0.2 0.958 0.002

a Detection limit is defined as 3 standard deviations (SD) on blind samples.b Distance from mine.

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transplantation are considered due to mine-related dust contamina-tion as these elements were highly enriched in the ore material(Johansen et al., 2001). Similarly, elevated Ca and Mg concentrationsin transplanted lichens are considered the result of extensive miningand excavation of calcitic and dolomitic marble in the area.

Aside from element concentrations, contamination from mining isalso reflected in the Zn/Pb ratio that changed from 30 to 38 inuncontaminated lichens to down to 1–3 in lichens after transplantation(Table 1). A Zn/Pb ratio in the range of 1 to 3 resembles the compositionof material found in the waste rock dumps in Maarmorilik (Asmund,1992). Furthermore, mine-related Pb in Maarmorilik had an isotopicsignature (207Pb/206Pb: 0.950–0.960)different fromnatural backgroundPb in the area (207Pb/206Pb: 0.704–0.767), which enabled tracing of themine-related Pb fraction in contaminated samples (Søndergaard et al.,2010). Uncontaminated lichens from Saatat had a 207Pb/206Pb ratiobetween that of ore-Pb and natural background Pb in Maarmorilik(207Pb/206Pb: 0.783–0.800) (Table 1).

Despite the contamination observed in lichens at sampling sites inMaarmorilik, no impact on the abundance and composition of residentlichen communities was found at those sites (Hansen, 1991). Anexceptionwas Site T12SWnear the formerwaste rock dumpwhere fewresident lichens were present, likely due to mechanical disturbance ofthe landscape.

4.2. Trends of Pb and Zn in resident lichens

During the period 1986–1990 when the mine still operatedelevated concentrations of Pb were observed in resident lichens asfar away as 35 km from the mine (Site L) relative to uncontaminatedlichens collected at Saatut or Schades Øer. Elevated concentrations ofZn were observed within a distance of 20 km from the mine (SiteT37). Pb and Zn concentrations in resident lichens were measured upto 630 and 300 mg kg−1 dry. wt. close to the mine. In contrast, Pb and

Table 2Results of the temporal trend analyses of Pb and Zn in resident and transplanted lichens at theis shown by “sig” and non-significance by “–“ for both the log-linear trend and the non-linear tlog-linear and non-linear trend not significant = no temporal trend; 2) log-linear trend signlog-linear trend and non-linear trend significant = non-linear trend; 4) log-linear trend noannual change in percentage during the period is given using the best-fitting exponential tr

Site Period Number ofsamples

Element Log-lineartrend

Non-lineartrend

ResidentT12SW 1987–2007 12 Pb sig –

T10 1986–2007 11 Pb – –

T12E 1986–2007 13 Pb sig –

T22 1986–2007 13 Pb sig sigT17A 1986–2007 13 Pb sig –

T17B 1986–2007 13 Pb – –

T5 1986–2007 11 Pb sig –

T6 1991–2007 10 Pb – –

T25 1986–2007 13 Pb sig –

T30 1986–2007 13 Pb sig –

T36 1986–2007 13 Pb sig –

T37 1986–2007 10 Pb sig –

T38 1986–2007 11 Pb – –

L 1986–2007 13 Pb sig –

TransplantedT12SW 1997–2009 7 Pb – –

T12E 1997–2009 7 Pb – –

T22 1997–2009 6 Pb – –

T17A 1997–2009 6 Pb – –

T17B 1997–2009 6 Pb – –

T6 1997–2009 6 Pb – –

T25 1997–2009 6 Pb – –

T30 1997–2009 6 Pb – –

T36 1997–2009 6 Pb – –

L 1997–2009 6 Pb – –

Zn concentrations in lichens at Saatut or Schades Øer were 0.4±0.1and 14±3 mg kg−1 dry wt. (mean±1SD), respectively. During themost recent sampling of resident lichens in 2007, both Pb and Znconcentrations were still elevated in resident lichens at sites within20 km from the mine. For resident lichens, only one sample wasanalyzed from each site and therefore it was not possible to performstatistical t-tests. The term ‘elevated’ used above refers to Pb and Znconcentrations above the mean concentration plus three standarddeviations of all lichen samples analyzed from Saatat or Schades Øer.

Results of the temporal trend analyses of Pb and Zn in residentlichens are seen in Table 2. During the period from 1986 to 2007, Pband Zn concentrations in resident lichens decreased at all 14 samplingsites in Maarmorilik. The trends were statistically significant at the 5%level for 10 of the sites for Pb and for 3 of the sites for Zn. Thedecreases in Pb and Zn concentrations in resident lichens mostlyfollowing a log-linear trend (exponential decrease) with an annualdecrease in Pb of 1–11% and Zn of 0–6%. The lower percentualdecrease in Zn relative to Pb in resident lichens reflects the highernatural background concentration of Zn in lichens and lower fractionof Zn related to mining contamination relative to Pb.

Pb and Zn concentrations in resident lichens at three sites (T22,T30 and T36) located with different distances to the mine are shownin Fig. 2. The highest Pb and Zn concentrations were observed nearestto the mine in the beginning of the sampling period when the minestill operated. After mine closure in 1990, Pb and Zn concentrationsdecreased in resident lichens. This is considered the result of adecrease in mine-related dust contamination after mining as mostdust generation were related to ore-crushing, handling of concen-trates and dumping of waste rock during the mine period. Thedecrease of mine-related Pb in resident lichens during the samplingperiod is evident from the change in the isotopic composition. This isillustrated in Fig. 3, which shows the 207Pb/206Pb ratios in Pb inresident lichens at the sites T22, T30, T36 and L during the period

sampling sites inMaarmorilik during the period 1986–2009. Significance at the 5% levelrend components. The results of the trend analyses can be interpreted as follows: 1) bothificant, non-linear trend not significant = log-linear trend (exponential trend); 3) botht significant, non-linear trend significant = non-linear trend. Furthermore, the overallend line.

Annual change(%)

Element Log-lineartrend

Non-lineartrend

Annual change(%)

−5.2 Zn – – −2.4−0.7 Zn – – −0.3−7.7 Zn – – −5.0−8.7 Zn – – −1.8−6.7 Zn – – −1.9−2.7 Zn – – −0.6−6.3 Zn – – −0.9−5.8 Zn – – −2.8

−10.8 Zn – – −5.4−6.4 Zn sig – −6.1−5.1 Zn sig – −5.1−6.9 Zn sig – −3.4−1.8 Zn – – −0.1−6.9 Zn – – −1.3

+7.5 Zn – – +6.1+5.2 Zn – – +5.9+7.7 Zn – – +1.1−3.4 Zn – – −1.5−1.3 Zn – – −2.5+6.3 Zn – – +3.7+2.5 Zn – – −1.5−2.9 Zn – – +1.2−2.1 Zn – – 0.0+0.6 Zn sig – +4.4

400

500 Site T22

Pb

Zn

0

100

200

300

0

40

80

120 Pb

Zn

Site T30 m

g kg

-1dr

y w

t.m

g kg

-1dr

y w

t.

20

30

40

Pb

Zn

Site T36

0

10

1985 1990 1995 2000 2005 2010

1985 1990 1995 2000 2005 2010

1985 1990 1995 2000 2005 2010Year

mg

kg-1

dry

wt.

Fig. 2. Pb and Zn in resident Flavocetraria nivalis lichens sampled at three sites with increasing distance to the mine: T22 (b1 km); T30 (5 km); and T36 (12 km) in the period 1986–2007. Each point represents the concentration in one 0.3 g sub-sample taken from a 2–3 g bulk sample.

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1987–2007 and their comparison with the 207Pb/206Pb ratios in mine-related Pb and natural background Pb from the area. As illustrated, themine-related Pb fraction is decreasing in resident lichens during theperiod after mining, most visible in lichens at sites most distant to themine (Site T36 and L) as the relative change in the fraction of mine-

Mine-related Pb

T12SW

L

T36207 P

b/20

6 Pb

Natural background Pb

1985 1990 1995 2000 2005 2010

Year

0.95

1.00

0.70

0.75

0.85

0.85

0.90

Fig. 3. Ratios of 207Pb/206Pb in resident Flavocetraria nivalis lichens sampled at the sitesT12SW, T36 and L in the period 1987–2007. The marked areas indicate the 207Pb/206Pbratios in mine-related Pb (207Pb/206Pb: 0.950–0.960) and in natural background Pb(207Pb/206Pb: 0.706–0.767) inMaarmorilik (from Søndergaard et al., 2010). Themean±1SD range on three replicate measurements is about the size of the symbols.

related Pb is highest there. However, the decrease is slow. Only at SiteL, located 35 km away from Maarmorilik, did resident lichens in 2007show an isotopic signature close to that of natural background Pb.

4.3. Trends of Pb and Zn in transplanted lichens and comparison withresident lichens

During the period 1996–2009 when transplantation of lichens wasconducted, significantly elevated concentrations of Pb were measuredat 12 of the 14 sampling sites, all located within a distance of 20 kmfromMaarmorilik after 1 year of transplantation (2 years in 2002). Znconcentrations were only significantly elevated at 10 of the 14 sites,which were situated within 5 km from the mine. Pb and Znconcentrations up to 170 and 270 mg kg−1 dry. wt., respectively,were measured in transplanted lichens close to the mine.

For transplanted lichens, the statistical time trend analysesshowed no significant decreases in Pb and Zn concentrations intransplanted lichens at any of the sites from 1996 to 2009 (Table 2). Asignificant increase in Zn concentrationswas observed in transplantedlichens at Site L, which was not considered contaminated by Zn fromMaarmorilik. Pb and Zn concentrations measured in transplantedlichens at three sites (T22, T30 and T36) with different distances tothe mine are shown in Fig. 4 together with concentrations measuredin resident lichens during the same period. At these three sites,transplanted lichens contained consistently less Pb compared toresident lichens after 1 or 2 years of transplantation during the entire

Resident ResidentPb Zn

Site T22 Site T22

Transplanted Transplantedm

g kg

.-1 d

ry w

tm

g kg

.-1 d

ry w

tm

g kg

.-1 d

ry w

t

mg

kg.-1

dry

wt

mg

kg.-1

dry

wt

mg

kg.-1

dry

wt

0

20

40

60

80

0

20

40

60

80

Transplanted

Resident

Transplanted

Resident

Pb ZnSite T30Site T30

1996 1998 2000 2002 2004 2006 2008 2010

1996 1998 2000 2002 2004 2006 2008 2010

1996 1998 2000 2002 2004 2006 2008 20101996 1998 2000 2002 2004 2006 2008 2010

1996 1998 2000 2002 2004 2006 2008 2010

1996 1998 2000 2002 2004 2006 2008 2010

10

20

30

10

20

30

Transplanted

Resident

Transplanted

Resident

ZnPbSite T36Site T36

0 0

YearYear

100

120

0

20

40

60

80

100

120

0

20

40

60

80

Fig. 4. Pb and Zn in transplanted Flavocetraria nivalis lichens at three sites with increasing distance to the mine: T22 (b1 km); T30 (5 km); and T36 (12 km) during the period 1997–2009. Corresponding measurements on resident lichens are shown for comparison. Each point represents the concentration in one 0.3 g sub-sample taken from a 2–3 g bulk sample.The transplanted lichens were sampled at an uncontaminated site (Saatut or Schades Øer) and placed at the sampling sites for 1 year (except in 2002 for 2 years). Lichens from Saatutor Schades Øer contained 0.4±0.1 mg kg−1 dry wt. Pb and 14±3 mg kg−1 dry wt. Zn.

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sampling period. This trend applies to all sampling sites within adistance of 20 km from Maarmorilik. The Pb contents in transplantedlichens were 24±23% (mean±1SD) of the Pb content in residentlichens. Pb concentrations in resident lichens at the sites most distantto the mine approached the concentrations in transplanted lichenstowards the end of the monitoring period (Fig. 4). Similar to Pb,concentrations of Zn were consistently lower in transplanted lichenscompared to resident lichens at the Zn contaminated sites (63±37%).

4.4. Application of lichens as monitors of dust contamination inMaarmorilik

In this study, lichen thalli were not washed prior to analyses.Therefore, elements found in the lichens include elements containedwithin the cells of the lichen thalli, elements selectively bound to the cellwalls by ion exchange mechanisms and elements contained as dustparticles on the upper thalli surface (Bari et al., 2001). The consistentlylower concentrations of Pb and Zn in transplanted F. nivalis lichenscompared to resident F. nivalis lichens after the mining stopped (Fig. 4)indicate that there was a carryover of Pb and Zn from previous dustdeposition in resident lichens. This is considered the result of acombination of several factors: 1) a large amount of contaminateddust spread inMaarmorilik during theminingperiod (annual amount of2 t of Pb and 5 t of Zn in 1986) (Asmund, 1992); 2) a very limited

amount of precipitation in the area (~100 mm per year) (Møller andPedersen, 1973), which reduces the washout of dust particles from thelichens; and 3) the cold arctic climate leading to very slow growth ratesof lichens in the region (Peck et al., 2000),which reduces the generationof new fresh lichen thalli and possibly also the exudation rate of certainelements including Pb and Zn from the lichen thalli.

Theobserveddifferencesbetween residentand transplanted F. nivalislichens in Maarmorilik after the mining period illustrate that residentlichens could not be used to assess recent (annual) dust contaminationin the area. In contrast, transplantation of lichens from an uncontami-nated area to sites in Maarmorilik followed by a collection 1 year afterwas considered an adequate method to assess recent dust contamina-tion. A carryover of previously deposited dust particles originating fromthe uncontaminated area may remain in the lichen transplants after1 year of transplantation. However, concentrations of Pb and Zn in theuncontaminated lichens were low (Table 1) and after 1 year oftransplantation, Pb and Zn concentrations were significantly elevatedat many of the sites (Table 1; Fig. 5). The period of transplantation wasthe same for all years (except for year 2002) and the lichen transplantswere collected from the same spots at each site every year. Furthermore,transplanted lichens were placed under a net and could not be blownaround on the ground and so accumulated metals were thought tooriginate entirely from air deposition. Consequently, transplantedlichens were considered adequate as relative measures of dust

1000 1000Pb

Zn

1

10

100

10

100

Pb

conc

entr

atio

n (m

g kg

-1dr

y w

t.)

0.1 1

Sites

Zn

conc

entr

atio

n (m

g kg

-1dr

y w

t.)

Fig. 5. Pb and Zn concentrations in Flavocetraria nivalis lichens transplanted from theIsland of Saatut in 2008 and collected at the 14 sampling sites in Maarmorilik in 2009.The sites are sorted with increasing distances to the old waste rock dump, Site T12SWbeing the nearest. Each point shows the mean±1 SD of 3 sub-samples taken from a 2–3 g bulk sample.

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contamination and allowed an evaluation of the spatial and temporalvariation of dust contamination near Maarmorilik.

4.5. The current dust contamination state in Maarmorilik, possible dustsources and lessons learned

The most recent sampling of transplanted lichens was done in2009 and concentrations of Pb and Zn in these lichens after 1 year oftransplantation compared to the initial concentrations are shown inFig. 5. Significantly elevated concentrations of Pb (pb0.05) weremeasured in lichens as far away as 20 km fromMaarmorilik (Site T37)while Zn concentrations were significantly elevated at sites locatedwithin a distance of 5 km from the mine (Site T30). However, it isimportant to note that the smaller area apparently affected by Zncontamination compared to Pb as indicated by the statistical testsdoes not necessarily mean that contamination with Zn does not occurin a wider area similar to Pb. The natural background concentration ofZn in lichens is much higher than Pb (14±3 vs. 0.4±0.1 mg kg−1,respectively; Table 1) and given the Zn/Pb ratio of typically 1–3 in ore/waste rock, it is simply not possible to detect a similar change in Znconcentration. In terms of dust contamination, our results indicatedthat dust contamination with Pb (and possible also Zn) still occurswithin an area up to 20 km from the mine and that the contaminationhas not decreased since 1996 (transplanted lichens; Fig. 4). In thisstudy, concentrations of Pb and Zn in transplanted lichens were usedonly as relative measures of dust contamination. Further studies areneeded to convert concentrations in transplanted F. nivalis lichens todust deposition and to quantify the dust deposition rates in the area.

During the mining operation in Maarmorilik, the main sources ofdust were ore-crushing, handling of concentrates and dust generatedfrom dumping of waste rock down the steep mountain sides from themine at about 600 m elevation. These dust sources ceased when themine closed down. The wind regime in Maarmorilik is dominated bystrong easterly wind and at the time of mine closure it seemed likelythat the dust remaining in the area would be transported in a westerndirection and end up in the fiords within a few years. Consequently,the continuous spreading of metal-contaminated dust in the areaalmost 20 years after mine closure is rather surprising. Two possiblemain explanations are considered: 1) it may be that fine particles arecontinuously generated and dispersed from thewaste rocks left on thesteep mountain sides due to rock falls and physical and chemicalweathering processes breaking the rocks down. In addition, some dust

contamination is likely to come from dispersal of remaining fineparticles from the partly removed waste rock dump near Site T12SVand from within the camp area. If weathering of the waste rock is themain reason for the dust pollution in Maarmorilik, this will last formany decades because the remaining waste rock dumps containseveral hundred thousand tons of rock and the scarce vegetationin the area will not allow any adequate vegetation cover to develop;2) an alternative explanation for the continuous dispersal ofcontaminated dust at the sampling sites in Maarmorilik is that, oncespread, the dust particles are continuously re-deposited within agiven site before ending up in the fiord a long time (decades) after. Alow amount of precipitation in the area indicates that little Pb and Znis dissolved from the particles and/or washed out into the fiord.

The continuous and widespread dispersal of metal-contaminateddust indicates that a major part of the Pb and Zn contamination stillobserved in the marine environment near Maarmorilik (Søndergaardet al., 2011) may be attributed to dispersal of dust. Originally, therelease of metals from mine tailings was the main source of metal-contamination of the fiords at Maarmorilik, but tailings ceased to bean important source almost immediately after mine closure(Søndergaard et al., 2011).

Several lessons canbe learned fromthemininghistory inMaarmorilik.In terms of dust dispersal, transportation of all waste rock to confinedareas as part of the mining process and subsequently applying a coverof chemically inert rock material such as marble/dolomite wouldgreatly have reduced the dust generation potential. This would alsohave reduced the oxidation and outflow of dissolved heavy metals fromthewaste rock dumps that are reported to be one of themain sources forcontamination of the marine environment in Maarmorilik (Søndergaardet al., 2011).

5. Conclusions

This study used resident and transplanted lichens to assess trendsin dust contamination near a former Pb–Zn mine in West Greenland.Nineteen years after mine closure, elevated concentrations of Pb intransplanted lichens after 1 year of transplantation indicated thatdispersal of contaminated dust still occurred within a distance of20 km from the mine. No declines in annual dust contaminationrates were indicated during the period 1996–2009 (6–19 yearsafter mine closure) when the method of transplanted lichens wasapplied. After the mine closed down, dust is thought to come mainlyfrom a continuous re-deposition of dust and/or from dust generatedas a result of physical and chemical weathering of the waste rock lefton the steep mountain sides. Consequently, this study emphasizesthat dust generation in relation to mining should be considered apotentially serious contamination problem, especially in dry arcticareas, where dust dispersal may last for decades after mine closure.This highlights the importance, not only for adequately-coveredbuildings and equipment during ore-crushing and loading/transpor-tation of concentrates, but also for adequate ways of disposing wasterock in order to reduce the generation and subsequently spreading ofcontaminated dust.

Appendix A. Supplementary data

Supplementary data to this article can be found online at doi:10.1016/j.scitotenv.2011.06.054.

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