Spatial and seasonal variations of elemental composition in Mt. Everest (Qomolangma) snow/firn

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Atmospheric Environment 41 (2007) 7208–7218

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Spatial and seasonal variations of elemental composition inMt. Everest (Qomolangma) snow/firn

Shichang Kanga,b,�, Qianggong Zhanga, Susan Kasparic, Dahe Qinb,Zhiyuan Conga, Jiawen Renb, Paul A. Mayewskic

aInstitute of Tibetan Plateau Research, Chinese Academy of Sciences (CAS), Beijing 100085, ChinabState Key Laboratory of Cryospheric Science, CAS, Lanzhou 730000, China

cClimate Change Institute and Department of Earth Sciences, University of Maine, Orono, ME 04469, USA

Received 13 February 2007; received in revised form 13 May 2007; accepted 15 May 2007

Abstract

In May 2005, a total of 14 surface snow (0–10 cm) samples were collected along the climbing route from the advanced

base camp to the summit (6500–8844m a.s.l.) on the northern slope of Mt. Everest (Qomolangma). A 108m firn/ice core

was retrieved from the col of the East Rongbuk Glacier (28.031N, 86.961E, 6518m a.s.l.) on the north eastern saddle of

Mt. Everest in September 2002. Surface snow and the upper 3.5m firn samples from the core were analyzed for major and

trace elements by inductively coupled plasma mass spectroscopy (ICP-MS). Measurements show that crustal elements

dominated both surface snow and the firn core, suggesting that Everest snow chemistry is mainly influenced by crustal

aerosols from local rock or prevalent spring dust storms over southern/central Asia.

There are no clear trends for element variations with elevation due to local crustal aerosol inputs or redistribution of

surface snow by strong winds during the spring. Seasonal variability in snow/firn elements show that high elemental

concentrations occur during the non-monsoon season and low values during the monsoon season. Ca, Cr, Cs, and Sr

display the most distinct seasonal variations. Elemental concentrations (especially for heavy metals) at Mt. Everest are

comparable with polar sites, generally lower than in suburban areas, and far lower than in large cities. This indicates that

anthropogenic activities and heavy metal pollution have little effect on the Mt. Everest atmospheric environment. Everest

firn core REE concentrations are the first reported in the region and seem to be comparable with those measured in

modern and Last Glacial Maximum snow/ice samples from Greenland and Antarctica, and with precipitation samples

from Japan and the East China Sea. This suggests that REE concentrations measured at Everest are representative of the

background atmospheric environment.

r 2007 Elsevier Ltd. All rights reserved.

Keywords: Snow/firn; Elements; Spatial and seasonal variations; Mt. Everest (Qomolangma)

e front matter r 2007 Elsevier Ltd. All rights reserved

mosenv.2007.05.024

ing author. Institute of Tibetan Plateau Research,

y of Sciences (CAS), Beijing 100085, China.

0 6284 9681.

ess: [email protected] (S. Kang).

1. Introduction

Glaciochemical records from the Himalayas canbe used to document the atmospheric impurityloading of the region and reconstruct the pastregional atmospheric environment (Ikegawa et al.,

.

ARTICLE IN PRESSS. Kang et al. / Atmospheric Environment 41 (2007) 7208–7218 7209

1999; Kang et al., 2002a, b; Mayewski et al., 1983,1993; Shrestha et al., 1997; Valsecchi et al., 1999;Wake et al., 1994). The location of Mt. Everest(Qomolangma) (271590N, 861550E, 8844.43m a.s.l.)(Fig. 1) at the boundary of the South AsianMonsoon (Indian Monsoon) and the continentalclimate of central Asia, combined with the highelevation of the site (well above the influence of theboundary layer), offers a unique opportunity todescribe and understand changes in the climate andchemistry of the atmosphere over Asia. Due to theunique location, studies on snow chemistry havefocused on Mt. Everest and its vicinity during thelast decade. Chemical data from snowfall events areavailable from monsoon and pre-monsoon seasonsfrom both the northern and southern slopes ofMt. Everest (Jenkins et al., 1987; Marinoni et al.,2001; Shrestha et al., 2002; Valsecchi et al., 1999;Kang et al., 2004) and its vicinity, includingMt. Xixabangma (�100 km from Everest) (Kanget al., 2002c; Mayewski et al., 1986), Mt. Cho Oyu(�40 km from Everest) (Balerna et al., 2003), andHidden Valley (Shrestha et al., 1997). Short-termfresh snow and aerosol sampling during monsoonand non-monsoon seasons has shown low pollutantconcentrations in the Himalayan atmosphere, sug-gesting high elevation regions of the Himalayas arerepresentative of the remote troposphere (Kanget al., 2002c; Marinoni et al., 2001; Shrestha et al.,1997; Wake et al., 1994). Spatial and temporalvariations in fresh snow chemistry over the centralHimalayas indicate that snow chemistry is stronglyinfluenced by the seasonal variations of atmosphericimpurity loading other than geographical locations(Balerna et al., 2003; Kang et al., 2002c; Marinoniet al., 2001). Major ions (e.g. Ca2+, SO2�

4 ) in snowhave a clear seasonal difference: non-monsoonion concentrations are much higher than monsoonion concentrations (Balerna et al., 2003; Kang et al.,2000, 2004; Marinoni et al., 2001; Shresthaet al., 1997, 2002; Valsecchi et al., 1999; Wakeet al., 1993, 1994).

Previous glaciochemical research in the Everestregion focused on the major ion and stable isotopiccomposition of snow. Recent analytical advancesnow make it possible to analyze for additional traceelements, providing further information on theatmospheric composition in this region. Here wepresent the results from major and trace elementanalysis of 14 surface snow samples and the upper3.5m firn samples from a 2002 Everest ice core onthe northern slope of Mt. Everest. The main

purpose of this work is to expand the snowchemistry database for the high mountain regionsof the Himalayas, to expand our knowledge of thespatial and seasonal variations of elemental compo-sition in snow at Mt. Everest, and to evaluate ifanthropogenic heavy metal pollution is contaminat-ing the Everest atmospheric environment.

2. Methods

In May 2005, a comprehensive scientific expedi-tion to Mt. Everest was organized by the ChineseAcademy of Sciences (CAS). During the expedition,an automatic weather station (AWS) was set up atthe col of the East Rongbuk Glacier (ER; 28.031N,86.961E, 6518m a.s.l.) on the northern slope ofMt. Everest. Table 1 provides basic meteorologicalinformation during May 2005. Low temperature(monthly average of �10.7 1C) and strong wind(monthly average of 7.5m s�1) were characterized inMay (Xie et al., 2006). A total of 14 surface snow(0–10 cm) samples were collected along the climbingroute from the advanced base camp to the summit(6500–8844m a.s.l.) on the northern slope ofMt. Everest (Fig. 1) between May 15 and 20 (therewas no snowfall during the sampling week).Sampling methods for snow are the same as thoseused by Wake et al. (1993, 1994) and Kang et al.(2004). Extreme care was taken at all times duringsample collection and handling to assure sampleswere not contaminated. For example, non-particu-lating suits, polyethylene gloves and masks wereworn at all times during sampling. Acid cleanedhigh-density polyethylene HDPE containers(Nalgene) were used to sample the snow directly.Field blanks filled with ultrapure water in thelaboratory were opened during sample collectionin the field and handled as samples. Samples werekept frozen in the field, during transportation, andin the laboratory until analysis.

A 108m firn/ice core was retrieved from the col ofthe ER Glacier in September 2002 (Fig. 1) (Kaspariet al., in review). The core was kept frozen duringtransport to the Climate Change Institute atUniversity of Maine, USA. The core was sampledat an interval of 4–5 cm using a Continuous Ice CoreMelter System with an aluminum melthead devel-oped by the University of Maine. This system usesfraction collectors to collect discrete, high-resolution,continuous, co-registered meltwater samples foranalysis of eight major ions, trace elements andisotope composition (Osterberg et al., 2006). The new

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Fig. 1. Site location of surface snow sampling and the firn core drilling on the northern slope of Mt. Everest.

S. Kang et al. / Atmospheric Environment 41 (2007) 7208–72187210

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Table 1

Meteorological status during May 2005

Parameters Units Mean Range

Air pressure hPa 456.2 452.9–459.9

Temperature 1C �10.7 �15.4 to �6.0

Relative

humidity

% 41.6 18.4–75.0

Wind speed m s�1 7.5 0–18.8

Table 2

Detection limits and blank concentrations for Everest surface

snow sample measurements

Elements Detection limit

(ng g�1)

Blank

Concentration

(ng g�1)

RSD

(%)

B 0.9780 0.07473 6.45

Na 0.0054 o0.000 17.95

Mg 0.0160 o0.000 0.95

Al 0.0430 o0.000 9.06

K 0.0120 2.151 56.07

Ca 0.0688 o0.000 117.59

V 0.0232 0.07581 7.78

Cr 0.0282 o0.000 79.18

Mn 0.0134 o0.000 71.35

Fe 0.0167 7.175 2.53

Co 0.0048 o0.000 0.88

Cu 0.0168 o0.000 6.21

Zn 0.0168 o0.000 0.85

As 0.1390 0.009955 452.54

Se 0.0531 0.07668 26.37

Mo 0.0460 0.08497 1.28

Cd 0.0125 0.002559 169.91

Sb 0.0222 o0.000 0.33

Cs 0.0460 0.004481 9.74

Pb 0.0031 o0.000 0.9

o Indicates the concentration was below the detection limit.

S. Kang et al. / Atmospheric Environment 41 (2007) 7208–7218 7211

continuous melter system with discrete samplingpreserves an archive of each sample, reduces theproblem of incomplete particle dissolution in induc-tively coupled plasma mass spectroscopy (ICP-MS)samples, and provides more precise trace elementdata than previous ice melter models by using longerICP-MS scan time and washing the instrumentbetween samples. The detailed methods for thesystem are provided by Osterberg et al. (2006).

Surface snow samples were acidified with 1% nitricacid and analyzed for a total of 20 elements includingB, Na, Mg, Al, K, Ca, V, Cr, Mn, Fe, Co, Cu, Zn,As, Se, Mo, Cd, Sb, Cs, and Pb by ICP-MS (Agilent7500a) at the Institute of Atmospheric Physics, CAS.Elemental concentrations of blank samples werebelow the detection limit, indicating minimal con-tamination during sampling and analysis (Table 2).Firn core samples from the upper 3.5m of theEverest core were analyzed for 32 elements (Na, Mg,Al, S, Ca, Ti, Fe, Mn, V, Cr, Co, As, Sr, Cs, Ba, Tl,Bi, U and 14 rare earth elements (REEs)) via aThermo Electron Element 2 double focusing mag-netic sector ICP-MS, in which samples were acidifiedwith 1% nitric acid and allowed to react for 1 week,and frozen until prior to analysis (Osterberg et al.,2006). Soluble ions (Na+, K+, Mg2+, Ca2+, SO2�

4 ,NO�3 , and Cl�) were analyzed via suppressed ionchromatography using a Dionexs DX-500 ionchromatograph. Samples were also analyzed for dD

via Cr reduction with a Eurovector elementalanalyzer coupled to a Micromass Isoprime massspectrometer (70.5% precision). All analysis of thefirn core had been carried out at the Climate ChangeInstitute, University of Maine.

3. Results and discussion

3.1. Elemental concentrations in surface snow and

their spatial variations

Surface snow samples (0–10 cm) collected alongthe climbing route in May, 2005 are representative

of the spring atmospheric environment. Averageelemental concentrations of the 14 surface snowsamples presented in Table 3 show that Ca, Na, K,Mg, and Fe have the highest concentrations. Crustalelements dominating the spring snow indicates thatEverest snow chemistry is mainly influenced bycrustal aerosols from prevalent spring dust stormsover the Tibetan Plateau (Fang et al., 2004; Kanget al., 2004; Song et al., 2004) or southern/central Asia(Kang et al., 2002a; Wake et al., 1994). In order todetermine if anthropogenic activities are impactingthe Everest atmospheric environment, a comparisonwith pre-industrial concentrations would need to bemade, but the lack of pre-industrial data precludesthis comparison. However, the low concentrationsof elements which may come from anthropogenicsources (e.g. Cd, Pb) suggest that anthropogeniccontributions of these elements, if present, areminimal.

Fig. 2 presents the variations of elementalconcentrations in surface snow versus elevation onthe northern slope of Mt. Everest. There are noclear trends for element variations with elevation.Most elements have high concentrations at thesummit of Everest, which may be due to pollutants

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Table 3

Mean elemental concentrations in surface snow/firn core and comparison with data in snow/ice/precipitation from other regions

Mt. Everest Arctic,

AtqasukaAntarctica,

AsukabAfrica,

LamtocJapan Europe,

AthensfChina, Hong

Kongg

Surface

snow

(S.D.)

Firn core

(S.D.)

Suburbd Higashi-

Hiroshimae

B 0.997

(1.460)

Na 324.8

(538.0)

22.4 (15.9) 1720 0.2–80 151 154

Mg 68.4 (86.5) 51.3 (34.3) 360 o200 29.7 25.8 90

Al 4.5 (4.1) 37.7 (53.6) 158 0.05–6 7.1 34 6.1 5.9 12.2

K 129.7

(225.3)

140 o180 28.1

S 36.6 (64.2)

Ca 1852 (2582) 208 (292) 270 179 94.5

Ti 3.01 (3.95) 0.1

Fe 11.5 (4.3) 50.5 (68.6) 93 3.2 7.5 4.4 15.1

Mn 2.0 (2.1) 2.0 (2.4) 3.32 o0.5 2.81 11 1.64 3.61 1.32

V 139 (73) 74.7 (92.1) 350 77 230 122.4

Cr 34 (68) 101.4

(147.3)

o310 o120 121 1290

Co oD. L. 36.8 (42.8) 420

Cu 343 (367) o700 2500 620 154100 2368

Zn 2032 (2390) 1400 1–500 9580 18000 4700 33460 23400

As 183 (295) 31.7 (35.1) 110 840

Se 49 (30)

Sr 440 (638) 7270 o160 950 130 1584

Mo 284 (320)

Cd oD. L.

Sb 2947 (2822) 400 1061

Cs 46 (45) 69 (104)

Ba 312 (330) 2968 1070 369 6713

Tl 1.6 (1.9)

Pb 5 (9) 507 o1000 62 880 144900

Bi 4.0 (7.3) 6

U 17.9 (20.6) 10.3 3

Source This study This study Douglas

and Sturm

(2004)

Ikegawa

et al. (1999)

Freydier

et al. (1998)

Hou et al.

(2005)

Takeda,

et al. (2000)

Kanellopoulou

(2001)

Zheng et al.

(2005)

Unit: ng g�1 for B, Na, Mg, Al, K, S, Ca, Ti, Fe, and Mn, and pg g�1 for others. oD.L. indicates the concentration was below the

detection limit.aSurface snow collected in mid-March.bSurface snow.cPrecipitation collected during 1994.dJapan (precipitation).ePrecipitation during 1995–1997.fPrecipitation during 1/10/97–31/3/98.gPrecipitation during June–December 1998.

S. Kang et al. / Atmospheric Environment 41 (2007) 7208–72187212

caused by climbers who gather at the site when theyarrive at the summit. High concentrations of majorelements (e.g. Ca, Mg, and Fe) at 7500m could beinfluenced by very local inputs of crustal dust sincethis site is close to bare rock.

Variations of crustal ion concentrations (e.g. Ca2+

and Mg2+) in summer snow from 5800–7000m onMt. Xixabangma showed a decreasing trend with

elevation ascent, reflecting the vertical distribution ofdust aerosols in the atmosphere (Kang et al., 2002c).However, strong winds (the average daily maximumwind speed is 18.8m s�1 at 6518m in May) occurduring spring over the high elevation regions ofMt. Everest (Xie et al., 2006), which could redis-tribute the surface snow and/or move crustal aerosolsshort distances from nearby rock areas (bare rock

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Fig. 2. Variations of elements in surface snow with elevation in the northern slope of Mt. Everest.

S. Kang et al. / Atmospheric Environment 41 (2007) 7208–7218 7213

areas can be seen in Fig. 1) onto the snow. Thus,surface snow redistribution and local crustal aerosolinputs may change the vertical profile of chemicalspecies in the free atmosphere (Warneck, 1988),causing a random altitudinal trend for crustalelements (or other trace elements) in snow onMt. Everest.

3.2. Seasonal variations of element concentrations

The firn core was seasonally dated (Fig. 3)according to the seasonality of dD and selectedions (Na+ and Ca2+) (Kang et al., 2000, 2004).Seasonal dating in Fig. 3 indicates that the firn core

spans three years of snow accumulation. Averageelemental concentrations of all the samples from thefirn core presented in Table 3 show that Ca, Mg, Fe,Na, Al, and S have the highest concentrationsranging from 36.6 to 208.0 ng g�1, which is similarto the surface snow samples. This indicates thatcrustal elements dominate the snow chemistry atMt. Everest (Kang et al., 2002a, 2004).

In order to further differentiate the seasonalvariations of element composition in the firn core,average concentrations of all elements in monsoon(a total of 41 samples) and non-monsoon (a total of29 samples) periods are presented in Fig. 4. Allelements exhibit much higher concentrations in

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Fig. 3. Selected ion and element concentrations versus depth in the firn core from the col of the East Rongbuk glacier. Vertical dashed

lines represent the seasonal boundaries.

S. Kang et al. / Atmospheric Environment 41 (2007) 7208–72187214

non-monsoon periods than during monsoon periods.Assessment of differences between two seasons usingt-test shows that all elements, except for S and Lu,

present seasonal differences with significant level at0.05. Ratios of monsoon/non-monsoon elementalconcentrations are calculated to reveal those elements

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Fig. 4. Comparison of element concentrations between monsoon and non-monsoon seasons in the firn core.

S. Kang et al. / Atmospheric Environment 41 (2007) 7208–7218 7215

with the most striking seasonal difference. Ca hasthe highest ratio (4.9), followed by Cr (4.7), Cs (4.7),and Sr (4.3). Ratios of other major and traceelements range from 2.1 (Na) to 3.9 (Ba), and REEsratios range from 2.6 (Lu) to 3.8 (Nd). In summary,the seasonal difference of elemental compositions inEverest firn is similar to soluble ions presented byKang et al. (2004), indicating that snow chemistry isstrongly influenced by crustal aerosols from local orarid (semi-arid) regions, especially during dust storm

periods in the non-monsoon seasons (e.g. winter andspring) (Gao et al., 1992; Qian et al., 1997; Songet al., 2004).

3.3. Comparisons of elemental concentrations among

different regions

Average concentrations of elements (exceptREEs) in precipitation from remote polar regions,urban areas, and from the Mt. Everest surface snow

ARTICLE IN PRESSS. Kang et al. / Atmospheric Environment 41 (2007) 7208–72187216

and firn core are presented in Table 3. AtMt. Everest, concentrations of major elements(e.g. Na, Mg, and Ca) are higher in surface snowthan that in the firn core, possibly resulting fromheavy crustal aerosol deposition in snow from localrock sources during spring as discussed above.Concentrations of V and As in surface snow arehigher than those in the firn core too, reflecting theirseasonality (i.e. higher values in spring).

Differences in source strength and transport ofmajor elements (e.g. Ca, Na, K, and Mg) causedifferences in concentrations at different sites. Forexample, Ca concentrations in surface snow aremuch higher at Mt. Everest than at Atqasuk(Arctic) (Douglas and Sturm, 2004), Lamto (Africa)(Freydier et al., 1998) or Higashi-Hiroshima (Japan)(Takeda et al., 2000) due to larger dust contribu-tions at Mt. Everest. Na and Mg concentrations arehigher in the Arctic than at Mt. Everest due tolarger sea salt deposition in the Arctic (Douglas andSturm, 2004).

Trace metals (i.e. Zn, Mn, Cu, As, V, and Cr) inEverest surface snow have low concentrations

Table 4

Rare earth element (REE) concentrations in the firn core and compari

La Ce Pr Nd Sm Eu Gd Tb

Mt. Everest

Firn core 13.44 29.65 3.53 13.79 3.90 0.92 2.54 0.6

(S.D.) (22.21) (47.77) (5.58) (21.36) (5.79) (1.35) (3.78) (0

East Antarctica

ISCa 11 22 2.5 7.7 1.6 0.24 1.9 0.2

Asukab 210 450 51 180 24 3.3 26 2.3

Dome Cc 73.4 167.5 51.9 7.2 2.1 1.2

Greenland

Summit

LGMd

45.1 99.6 7.5 26.0 4.7 1.0 4.6 0.6

Asia

Inilchek

Glaciere1024.8 2583.1 275.5 916.0 166.1 40.7 137.8 19

Japan and

East China

Seaf

21.47 54.02 3.56 10.59 1.69 0.31 1.34 0.1

Unit: pg g�1.aSurface snow.bSurface snow.cIce core samples during LGM.dIce core samples during LGM.eFirn core samples during 1992–1998.fPrecipitation sample.

similar to remote sites (Table 3), such as Atqasuk(Douglas and Sturm, 2004) and Asuka (Ikegawaet al., 1999), suggesting negligible heavy metalpollution at Mt. Everest. This is further supportedby Cd with concentrations below the detection limit,and low Pb concentration—the lowest concentra-tion of these sites. Heavy metal (especially Cu, Zn,and Pb) concentrations are much lower at Mt.Everest than in large cities, such as Hong Kong(Zheng et al., 2005), Athens (Kanellopoulou, 2001),and Higashi-Hiroshima (Takeda et al., 2000),indicating a strong contrast of the atmosphericenvironment in urban areas with intensive anthro-pogenic activities and in natural remote regions. Asa whole, elemental concentrations (especially forheavy metals) at Mt. Everest are comparable withpolar sites, generally lower than in suburban areas,and far lower than large cities. This indicates thatanthropogenic activities and heavy metal pollutionhave little effect on the Mt. Everest atmosphericenvironment.

Due to the low REE concentrations and limitedvolume of samples, few measurements of REE

son with snow/ice core/precipitation data from other regions

Dy Ho Er Tm Yb Lu Source

6 4.33 0.72 1.88 0.26 1.73 0.24 This study

.94) (6.66) (1.17) (3.11) (0.44) (3.02) (0.43) This study

1.2 0.18 1.3 0.086 0.65 0.075 Ikegawa et al.

(1999)

9.6 1.5 3.8 0.54 3.8 0.43 Ikegawa et al.

(1999)

4.2 0.6 Grousset et al.

(1992)

3.2 0.7 1.8 0.2 1.8 0.2 Svensson et al.

(2000)

.9 113.5 20.0 52.9 48.4 6.8 Kreutz et al.

(2000)

5 0.73 0.14 0.44 0.06 0.44 0.07 Zhang and Liu

(2004)

ARTICLE IN PRESSS. Kang et al. / Atmospheric Environment 41 (2007) 7208–7218 7217

concentrations have previously been made on icecores (Grousset et al., 1992) or snow samples fromremote areas. REE concentrations reported in polarsnow/ice and precipitation and fromMt. Everest aresummarized in Table 4. REE concentrations in theEverest firn core are comparable with modern andLast Glacial Maximum (LGM) snow/ice samplesfrom Greenland (Svensson et al., 2000) andAntarctica (Grousset et al., 1992; Ikegawa et al.,1999), but are far lower than REE concentrationsfrom the Inilchek Glacier in central Asia (Kreutzand Sholkovitz, 2000) due to the significant influx ofdust derived from the arid regions in close proxi-mity to the Inilchek Glacier. Additionally, theMt. Everest REE concentrations are similar toprecipitation samples collected in Japan and theEast China Sea (Zheng et al., 2005), providingfurther support that Mt. Everest is representative ofthe background atmospheric environment.

4. Summary

We present the first comprehensive elementalconcentrations in snow/firn from Mt. Everest.Crustal elements dominate both surface snow andthe firn core, indicating that Mt. Everest snowchemistry is mainly influenced by crustal aerosolsfrom local rock sources or prevalent spring duststorms over southern/central Asian.

There are no clear trends for variations in elementconcentrations with elevation, possibly due to localcrustal aerosol inputs or redistribution of surfacesnow by strong winds during the spring. Highelemental concentrations occur during the non-monsoon season, and low concentrations during themonsoon season. Ca, Cr, Cs, and Sr display themost distinct seasonal variations.

Elemental concentrations (especially for heavymetals) at Mt. Everest are comparable with polarsites, generally lower than in suburban areas, andfar lower than large cities. This indicates thatanthropogenic activities and heavy metal pollutionhave little effect on the Mt. Everest atmosphericenvironment. REE concentrations in Everest firnare the first reported in the region and arecomparable with those measured in modern andLast Glacial Maximum snow/ice samples fromGreenland and Antarctica, and with precipitationsamples from Japan and the East China Sea. Thissuggests that REE concentrations measured atEverest are representative of the background atmo-spheric environment.

Acknowledgments

This study was supported by the ‘‘Talent Project’’and Innovation Project (KZCX3-SW-334/339) ofChinese Academy of Sciences, the National NaturalScience Foundation of China (40401054), theNational Basic Research Program of China (2005CB422004), Social Commonweal Research Projectof Ministry of Science and Technology of China(2005DIA3J106), and US National Science Foun-dation (NSF-ATM-0139481). Thanks are owed toteam of the Fourth Comprehensive ScientificExpedition to Mt. Everest and team of the 2002Everest Ice Core Project. The authors acknowledgeD. Introne, S. Sneed, and M. Handley at Universityof Maine for analyzing dD, soluble ion and elementsamples.

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