Distribution of Persistent Organic Pollutants in Soil and Grasses AroundMt. Qomolangma, China

X.-P. Wang,1 T.-D. Yao,1 Z.-Y. Cong,1 X.-L. Yan,1,2 S.-C. Kang,1 Y. Zhang2

1 Institute of Tibetan Plateau Research, Chinese Academy of Sciences, P. O. Box 2871, Beijing 100085, China2 School of Chemistry and Engineerings, Shanxi University, 36 Wucheng Road, Taiyuan 030006, China

Received: 31 May 2006 /Accepted: 4 September 2006

Abstract. Previous literature has reported the fate of persistentorganic pollutants (POPs) in mountainous regions, but theHimalayas have received little attention, and few results fromthis region have been published. The present study collectedsoil and grass samples from the Mt. Qomolangma (Everest)area, central Himalayas, China, from the elevation range 4700to 5620 m. We analyzed all samples for organochlorine pes-ticides (OCPs) to determine the level of OCP contamination inthe Qomolangma region. The soil samples contained 0.385 to6.06 ng g–1 of DDT only, and these concentrations were lowerthan those from Europe and mountains close to industrialemissions. Our study detected a number of OCPs in the grasssamples, such as hexachlorocyclohexane (HCH) (0.354 to 7.82ng g–1), hexachlorobenzene (HCB) (0.0156 to 1.25 ng g–1),endosulfan (0.105 to 3.14 ng g–1), and DDT components (1.08to 6.99 ng g–1). Their concentrations were higher than those inpine needles from Alberta, Canada. Our measurements ofHCH and DDT in grass samples showed the same or slightlyhigher concentration levels than reported in moss from Mt.Qomolangma 15 years ago. This result and the analysis ofisomer ratios (a/c-HCH and p-p�-DDE/p-p�-DDT) indicaterecent releases of OCPs from a nearby region, possibly fromdicofol use in India. We also investigated the elevation dis-tribution of OCPs and found that HCH and HCB were pro-gressively concentrated in colder, higher elevation sites. Abioconcentration factor (BCF) of grass was calculated, and theBCF values increased with the increasing elevation, indicatingthat the cold condensation of POPs at high-elevation sites mayincrease the potential threat to vegetation and the food chain inthe mountain ecosystem.

In past decades, the ‘‘grasshopper-effect’’ model has success-fully explained how persistent organic pollutants (POPs) canmigrate to polar regions through repeated evaporation, atmo-spheric transport, and deposition (Wania and Mackay 1995,1996). Recently, interest has increased in quantifying organiccontaminant levels in mountain ecosystems to study how these

contaminants may impact humans through either aquatic orterrestrial pathways (Daly and Wania 2005). Organic con-tamination in high mountains may pose a threat to mountainecosystems themselves. However, mountain regions also serveas the primary water supply for lowlands. Contamination ofsnow and lake water in high mountain regions has the potentialto impact drinking and agriculture water supplies. High-alti-tude vegetation may be at risk, and livestock and top predatorsin the mountain regions may bioaccumulate organic com-pounds through food chains. Chemicals enter the mountainsystem from atmospheric sources, either by dry deposition,resulting in air–snow, air–water, air–soil, and air–vegetationgaseous partitioning, or by wet deposition, which leads to POPscavenging and capture by snow. In mountain regions, chem-ical uptake by grasses can be affected by the air–grass equi-librium partitioning, water–grass exchange during exposure tomelt water, and the uptake and transfer of pollutants from soilto grass. Investigations of the levels of POPs in snow, soil, andgrasses in these regions provide critical information forassessing human and animal health risks.

Although many researchers have studied the role ofmountains in POP distribution and transportation, some majormountain regions, such as the Himalayas, have receivedminimal attention. Little work on contaminants in the centralHimalayas has been reported. The Himalayan Mountainswedge between India and China. Mt. Qomolangma (8844 m)reaches the highest elevation in the Himalayas and in theworld (Loewen et al. 2005). The huge Himalayan mountainchain lies adjacent to the world�s most densely populatedcountries, including India, Pakistan, Bangladesh, and China.In the past, the Indian subcontinent and China have heavilyused organochlorine pesticides (OCPs), such as hexachloro-cyclohexanes (HCHs) and DDT (Loewen et al. 2005). Thecurrent findings of increased POP levels in these highmountain regions point to the importance of a cold-conden-sation effect on the enhanced POP concentrations at highelevations. Because of the usage history and behavior ofPOPs, investigations regarding ecologic and ecotoxicologiceffects of POPs in the Himalayan region provide an impor-tant and valuable assessment of potential risks. The grassesJidou (O. glacialis Benth.ex Bge) and Rouzi (T. rupifragumSchrenk) dominate the ground cover of the Himalayan regionbelow 5800 m. They are long living, high in lipids, andCorrespondence to: X.-P. Wang; email: wangxp@itpcas.ac.cn

Arch. Environ. Contam. Toxicol. 52, 153–162 (2007)DOI: 10.1007/s00244-006-0111-6

provide the main food for yaks and sheep. Because Tibetanpeople depend heavily on yak meat and yak and sheep dairyproducts, the terrestrial food chain near Mt. Qomolangmaconsists of grasses, yaks and sheep, and humans. Theobjective of this study was to investigate the levels anddistribution patterns of OCPs in snow, soil, and grasses from4700 to 5600 m elevation around the northern slope of Mt.Qomolangma. Our study investigated trends of these pollu-tants with elevation and the accumulation of pollutants ingrasses.

Materials and Methods

Sample Collection

A fresh snow sample was collected in April 8, 2005, and grass and soilsamples were collected in April 2005, from the north slope of Mt.Qomolangma (Fig. 1; Rongbuk Valley [N 28.30�, E 87.04� toapproximately N 28.29�, E 87.03�). With the increase of elevation(from 4700 to 5600 m), 13 Jidou, 11 Rouzi, and 24 soil samples werecollected. Grass samples were wrapped in clean aluminum foil, storedin sealable plastic bags, and stored at –18�C until extraction. The soilsamples were obtained by shaking the loosely adhering soil from theroots of the Jidou and Rouzi grass samples. The soil samples wereseparated before freezing and subsequent analysis for OCP contami-nants.

Extraction and Cleanup

Soil. A 10-g freeze-dried soil sample was Soxhlet extracted with200 ml mixed solvent (n-hexane/acetone 1:1 v:v) for 24 hours. Eachsample was spiked with a-HCH-D6 and p-p�-DDE-D8 as recoverysurrogates. The extract was concentrated and cleaned with a column(30 cm in length and 1 cm i.d.) of 5 g Florisil (Pesticide pure grade,60/100 mesh, Supelco, activated at 130�C for 24 hours and stored ina sealed desiccator before use) and 2-cm-thick anhydrous sodiumsulfate. The OCPs were then eluted with 20 ml n-hexane and di-chloromethane (19:1 v:v) and n-hexane and dichloromethane (2:1v:v), respectively. The elution was concentrated to 1 ml with astream of purified nitrogen. Mirex was spiked as an internal standardbefore analysis. N-hexane, dichloromethane, and acetone (Pesticide

Pure, Fluka) were glass-to-glass distilled twice, and the solventchecks showed that there were no interferences with the targetcompounds. Standards of HCHs, HCB, DDT components, a-HCH-D6, and p-p�-DDE-D8 were purchased from Dr. Ehrenstorfer GmbH,Germany. The term �DDT components� in the text refers to DDT-related compounds, including p-p�-DDT and o-p�-DDT and theirmetabolites, DDE, and DDD.

Plants. A 5-g sample of grass was placed in a clean 50-ml amberglass vial, spiked with recovery surrogate, and sonicated for 30minutes in a 8:2 mixture of n-hexane and acetone covering the veg-etation in an ultrasonic cleaner. The solvent was decanted, and grasssamples were sonicated once more with a fresh portion of the mixture(8:2 n-hexane and acetone). Sulfuric acid was used for cleanup. AFlorisil column was used after decreasing the volume with a rotaryevaporator. The n-hexane and dichloromethane (19:1) and n-hexaneand dichloromethane (2:1) were used to elute the column, and thecombined elution was concentrated to 1 ml and the internal standards(Mirex, 10 pg) spiked before analysis.

Snow. A snow sample was melted in a clean room in its closed-fieldcontainer (= 2 L water equivalent). To minimize re-equilibrium ofpesticides with the atmosphere, the sample was extracted as soon asthe last bit of snow melted. Then the melted water sample was ex-tracted with pesticide-grade dichloromethane (DCM) in a Gouldenliquid–liquid extractor. The DCM extract was evaporated under vac-uum, exchanged into hexane, and analyzed by gas chromatography–mass spectrometry–mass (MS) detection.

Analysis. OCPs in all samples and field blanks were analyzed usinga gas chromatograph with an ion-trap mass spectrometer (FinniganTrace GC/PolarisQ). A 30 m x 250 lm i.d. HP-5MS capillary columnwas used for separation. High-purity helium was used as a carrier gasat a constant flow rate of 1.0 ml min–1. Each sample (1 L) was injectedunder splitless injection mode. The mass spectrometer was operated in70-eV electron impact mode. When the mass spectrometer is using anion-trap as the mass separator, the MS-MS mode can be used toachieve high sensitivity. The analytic conditions for MS-MS deter-mination and limits of detection of target compounds are listed inTable 1. The oven temperature for OCP detection was 100�C held for2 minutes, ramped up at 25�C/min to 170 �C, at 8�C/min to 225�C, at0.7�C/min to 235�C, and then at 25�C/min to 260�C and held for2 minutes. The temperature of the injector was 250�C, and the tem-perature of transfer line was 280�C. Total organic matter of thesoil sample was determined using a total organic carbon analyzer(Shimadzu 5000-A).

Quality control. One ml surrogate (a-HCH-D6, p-p�-DDE-D8 10 pg/ll) was added to each sample (snow, soil, and vegetation) beforeextraction. The recovery of OCP laboratory surrogates for soil andgrass samples were 104% € 18.3% for a-HCH-D6 and 95% € 4.6%for p-p�-DDE-D8. The recovery of surrogates for snow sample were97.2% € 8.1% for a-HCH-D6 and 96% € 3.7% for p-p�-DDE-D8.The accuracy of the method was assessed by analysis of the NationalInstitute of Standards and Technology standard reference material1944 New York/ New Jersey Waterway Sediment, and values within60% to 115% of the certified values were obtained. Table 2 lists thecertified values of this reference material and the detected values inthis study. Aluminum foil used for storage of grass samples was rinsedwith acetone and hexane before heating for 12 hours at 200�C. Allglassware was washed with detergent, rinsed in triplicate with tapwater followed by deionized water, rinsed with redistilled acetone and

Fig. 1. Location of research area (Fang et al. 2004)

154 X.-P. Wang et al.

hexane, and heated for 12 hours at 200�C. Glass Pasteur pipettes usedfor transfer of solvents and sample extractant were also heated for 12hours at 200�C. To monitor potential laboratory contamination, pro-cedure blanks were processed after every 10 sample extractions. Mostof the OCPs (the exception being HCB) in procedural blanks werelower than the method detection limit, and all samples were extractedand analyzed in triplicate; all data were blank corrected before anal-ysis by subtracting the mean blank concentration from extract con-centration (for HCB only).

Results and Discussion

Levels of HCHs and DDT Components in Soil and GrassSamples

Table 3 lists the number of samples and the concentrations oftotal organic carbon (mgC/g) for soil samples. Table 4 lists theconcentrations of OCPs in soil detected in this study and the

Table 1. Analytic conditions for MS-MS determination

Target compound

Ion selection (m/e)

Detection limit (pg) Values of procedure blank (pg)Parent (width) Daughter

a-HCH 181(4) 145–148 0.41 LODc-HCH 181(4) 145–148 0.33 LODHCB 284(4) 247–249 0.75 5.4p,p�-DDE 318(4) 246–248 0.88 LODp,p�-DDD 235(4) 165–167 0.14 LODo,p�-DDT 235(4) 199–203 0.18 LOD

165–167p,p�-DDT 235(4) 199–203 0.5 LOD

165–167o,p�-DDE 318(4) 198–203 0.47 LOD

246–250o,p�-DDD 235(4) 165–167 0.11 LOD

199–203a-Endosulfan 195(4) 158–162 1.15 LODb-Endosulfan 195(4) 158–162 1.03 LOD

LOD = Limit of defection.

Table 2. Certified values of NIST standard reference material 1944 New York/ New Jersey Waterway Sediment and the detected values in thisstudya

Compound Concentration (ng g)1)

NIST value This study

Minimal Maximal Value range (%) SD

p-p�-DDT 0.119 0.102 0.124 85–104 0.0083o-p�-DDD 0.038 0.041 0.045 107–118 0.0025o-p�-DDE 0.019 0.017 0.021 89–110 0.0037p-p�-DDD 0.108 0.087 0.114 80–105 0.0092p-p�-DDE 0.086 0.073 0.099 84–115 0.0056a-HCH 0.002 0.0023 0.0028 80–90 0.00033Naphthalene 1.65 2.24 2.33 135–141 0.053Phenanthrene 5.27 5.45 5.62 103–106 0.047Acenaphthene 0.57 0.57 0.59 100–104 0.016Anthracene 1.77 1.75 1.82 98–102 0.024Perylene 1.17 0.98 1.22 83–107 0.078Chrysene 4.86 4.53 4.87 93–105 0.35Fluoranthene 8.92 9.04 9.23 101–103 0.29Fluorene 0.85 0.835 0.879 98–103 0.077Benzo[a]fluoranthene 0.78 0.65 0.79 83–101 0.046Benzo[a]pyrene 4.3 4.19 4.8 97–111 1.02Benzo[b]fluoranthene 3.87 3.43 3.69 88–95 0.55Benzo[ghi]perylene 2.84 1.98 2.67 69–94 0.89Benzo[k]fluoranthene 2.3 2.55 2.69 110–116 0.38Indeno[1,2,3-cd]pyrene 2.78 2.57 2.94 92–106 0.64

a The internal standard used for OCP detection is Mirex, and 10 pg Mirex was added to each extractant before analysis. One microliter surrogate(a-HCH-D6, p-p�-DDE-D8, 10 pg/ll) was added to each sample before extraction. The absolute amount of recovery surrogates is 10 pg, which isthe same as that of internal standard. The recovery of OCP laboratory surrogates was 104% € 18.3% for a-HCH-D6 and 95% € 4.6% for p-p�-DDE-D8.

POPs Around Mt. Qomolangma, China 155

values reported from other mountain regions. The mostubiquitous compounds found in the soil were DDT compo-nents, occurring in almost all samples. Total concentrations ofDDT in soil from this study ranged from 0.385 to 6.06 ng g–1

dry weight, roughly similar to values from the Pyreneesmountains, Europe (Grimalt et al. 2004a), and slightly lowerthan those reported from Austria (Weiss et al. 1998) andPoland (Migaszewske 1999). However, the DDT concentra-tions in mountain soils located near to industrial sites (GiantMountains, Czech-Polish border) were hundreds of timeshigher than the values of this study (Picer et al. 2004). TheTeide mountain soils (Tenerife Island, in the Atlantic) alsoshowed high concentrations of both HCHs and DDTs (Grimaltet al. 2004a). As can be seen from Table 4, the OCP levels atMt. Qomolangma are relatively low and what one might ex-pect in such a remote region of the world. These low valuesmay represent a soil background for midlatitude NorthernHemisphere soils outside the direct influence of an immediatesource.

Unlike the soil samples, grass samples showed the presenceof other OCPs, including HCHs, HCB, and endosulfans (Ta-ble 5). Total HCHs, HCB, and DDT component concentrationsin grasses from Mt. Qomolangma were in the range of 0.354 to7.82 ng g–1, 0.0156 to 1.25 ng g–1, and 1.53 to 9.46 ng g–1,respectively, which are higher than concentrations reported inconifer needles from mountain areas in Alberta (Davidson

et al. 2003). However, endosulfan concentrations found by thisstudy were in the range of 0.29 to 3.14 ng g–1 for a-endosulfanand 0.105 to 1.54 ng g–1 for b-endosulfan, which are similar toresults obtained by Davidson et al. (2003).

Calamari et al. (1991) investigated the role of plant biomassin the global environmental partitioning of chlorinatedhydrocarbons. Their study collected pine needle, lichen,mango, and moss samples before 1991. The sample sites inthat research included 26 areas of the world, from N78�, E15�

to S74�, E168�, and elevations ranging from sea level to 5600m. Table 5 lists the OCP values from New Delhi, Nepal, andMt. Qomolangma obtained by Calamari along with those fromthis study. OCP concentrations detected in this study weregenerally lower than those reported by Calamari et al. (1991)for New Delhi and Nepal, but a-HCH and p-p�-DDT were atthe same level or slightly higher than the values reported forMt. Qomolangma. This could possibly indicate the continueduse of DDT and HCH in adjacent regions. Li et al. (1996)investigated global HCH use with a 1� x 1� longitude/latituderesolution and noted that the use of technical HCH on crops inIndia was still 20,000 tons/y, even after the Indian governmentbanned its use (Li et al. 1996). Subsequently, Li et al. (2006)observed relatively high HCH concentrations in air at Mt.Qomolangma and back-traced the movement of air massesduring the monsoon season, which suggests that the HCHsoriginated mainly from the Indian subcontinent. Although the

Table 3. Number of samples and TOC of soils

Increase (m) Rouzi Jidou Soil TOC (mgC/g)

4600 3 2 5 10.44800 3 2 5 2.865210 2 2 4 2.875440 3 3 6 2.945620 2 2 4 2.88

TOC = Total organic carbon.

Table 4. Concentrations of main OCPs in soils (ng g)1) from Mt. Qomolangma and other mountain areas

Target compound This studyPyrenees Mountains,Europea

Woodland regionsof Austriab

Holy Crossmountain, Polandc

Giant Mountains,Czech-Polish borderd

Teide,Atlantice

a-HCH ND 0.13–0.80 – 0.5–0.65 – 59c-HCH ND – – <0.5 – 49HCB ND 0.06–0.40 <1.9 0.47–48 310p,p�-DDE 0.111–2.03 – – 1.50–2.29 – 3400p,p�-DDD 0.0132–0.153 – – <0.5 – 2000o,p�-DDT 0.0289–0.315 – – – –p,p�-DDT 0.0822–2.91 – – 8–138 – –o,p�-DDE 0.0504–0.428 – – – –o,p�-DDD 0.00991–0.223 – – – –Sum of DDT components 0.385–6.06 0.42–10 <22.0 9.00–142 20–5100 –a-Endosulfan ND – – 4.93–65.1 – –b-Endosulfan ND – – <0.5 – –

For soil samples, the POP concentrations used was normalized by soil TOC content.a Grimalt et al. (2004a).b Weiss et al. (1998).c Migaszewske (1999).d Picer et al. (2004).eGrimalt et al. (2004b).ND = Not determined.

156 X.-P. Wang et al.

use of technical HCH has been forbidden, lindane (c-HCH) isstill used in Canada (Bidleman 1999), China (Qiu et al. 2004),and other sites around the world. Weiss et al. (2000) reportedhigh values of c-HCH, and these high values appear to beassociated with the proximity of the sampling sites to agri-culture to which lindane had been applied. Concentrations ofc-HCH found in this study are lower than those of Calamari�sresult for Mt. Qomolangma, suggesting decreased use of lin-dane in the Mt. Qomolangma region since 1991. High DDTconcentrations in air at Mt. Qomolangma, compared with theArctic, also indicate that this mountain region is close to DDTsources and that DDT may currently be in use (Li et al. 2006).

Snow events scavenge pollutants from air, and pollutantscan accumulate and condense in snowpacks. When the snowmelts, those pollutants may be carried by the melt water andtransfer to soil, being adsorbed by soil organic matter or clayconstituents. Subsequently, grasses may take up the pollutantsfrom the melt-water and soil system. During our sampling, wecollected one fresh snow sample in which only DDT compo-nents were detected. The more volatile HCH and HCB(Davidson et al. 2003) were not detected, implying the rapidevaporation of these pollutants during snow melt. Total DDTconcentrations in this snow sample reached a maximum of0.09 ng L–1, which is one order of magnitude lower than aseries of 1970s snow measurements from Doumer Island, offthe Antarctic Peninsula (Risebrough et al. 1976). This result isalso lower than values from Colle del Lys (Finizio et al. 2006)and Punta indrena (Herbert et al. 2004). Although DDT con-centrations observed were low, the uptake of pollutants tograsses and the sequestration of pollutants in soil still exhibit apotential threat to the weak mountain ecosystem.

Distribution of OCPs Along the Elevation Gradient

In our examination of the distribution of POPs at Mt. Qo-molangma, we correlated the analyte concentrations in soiland grass with elevation. The concentrations of individualDDT components detected in soil samples did not correlatesignificantly with elevation. However, for grass samples, themore volatile OCPs (Pl >0.1 Pa, 25�C), such as a-HCHand HCB, correlated positively with elevation, whereas less

volatile OCPs (e.g., p-p�-DDT and aldrin) correlated inverselyor appeared uncorrelated with elevation (Figs. 2 and 3).Table 6 lists the coefficient of determination (r2 values) of thecorrelation between concentrations of OCPs and elevation.The good linearity of these profiles suggests that high ele-vation is sensitive and may be the condenser of global POPs.Volatile OCPs are likely to evaporate and can be significantlydeposited by dry absorption onto vegetation and/or soil or bysnow scavenging in the mountains. Volatile OCPs are proneto ‘‘hop’’ to more distant regions, undergoing >1 jump cycle,and accumulate at high latitude or high elevation. The rela-tively low evaporation of less volatile POPs characteristicallyresults in short-distance transport. Similar trends have beenobserved by other investigators and in other environmentalmedia. Vives et al. (2004) analyzed OCPs in fish from highmountain lakes and noted increases in HCH concentrationsand decreases in DDT concentrations with increasing eleva-tion. Moss samples from the Andean mountains also dem-onstrated temperature-dependent distribution patterns of OCPs(Grimalt et al. 2004b). For total concentrations of OCPs,positive correlations were observed between the sum of HCHand elevation. However, the sum of the DDT componentconcentrations, for either soil or grass samples, decreased withincreasing elevation (Figs. 4 and 5).

Possible OCP Sources in the Mt. Qomolangma Region

Calamari et al. (1991) showed how ratios of a-HCH to c-HCHand of DDT to DDE can be used as indicators of contaminantsource age. Generally, technical HCH contains isomers in thefollowing percentages (Metcalf 1955): a 55% to 80%; b 5% to14%; c 8% to 15%; d 2% to 16%; and � 3% to 5%. The averagea/c-HCH ratio in technical HCH product should be between 3:1and 7:1 (Iwata et al. 1993), whereas in this study this ratioreached as high as 41:1 in samples from 5620 m, the highestsampling site. A high a/c-HCH ratio suggests older or moredistant sources because a-HCH is no longer used in mostcountries, and c-HCH degrades to a-HCH (Oehme 1991). In-creased ultraviolet radiation at extreme elevations increasesthe rate of transformation of c- to a-HCH isomers. Further-more, c-HCH is more water-soluble than a-HCH, making it

Table 5. Concentrations of the main OCPs in vegetation (ng g)1) from Mt. Qomolangma and other mountain areas

Target compoundGrasses from Mt.Qomolangma (this study)

Pine needles fromAlberta, Canadaa

Mango fromNew Delhi (mean)b

Lichens fromNepal (mean)b

Mosses fromMt. Qomolangma (mean)b

a-HCH 0.354–7.82 0.2–0.35 106.9 21.5 9.50c-HCH 0.0324–0.212 – 13.55 3.46 1.15HCB 0.0156–1.25 0.18–0.24 <0.1 0.1 0.48p,p�-DDE 0.215–1.12 0.0214–0.0832 21.0 1.9 0.3p,p�-DDD 0.134–0.432 – – – –o,p�-DDT 0.172–0.553 – 10.8 2.4 1.80p,p�-DDT 0.143–5.66 – 77.8 13.7 2.10o,p�-DDE 0.292–0.729 – – – –o,p�-DDD 0.124–0.617 – – – –Sum of DDT components 1.08–6.99 – – – –a-Endosulfan 0.29–3.14 – – – –b-Endosulfan 0.105–1.54 0.5–1.25 – – –

a Davidson et al. (2003).b Calamari et al. (1991).

POPs Around Mt. Qomolangma, China 157

more readily removed from air by precipitation or depositionwith water (Law et al. 2001). Our results show the ratios of a/c-HCH increasing significantly with elevation (Fig. 4), suggest-ing that higher sites receive HCH from more distant sources.

Both soil and grass samples in this study showed detection ofp-p�-DDE, o,p�-DDE, o,p�-DDD, and p,p�-DDD. TechnicalDDT contains less o,p�-DDT (15%) than p-p�-DDT (85%).Considering that degradation half-lives of o-p�-DDT and p-p�-

Fig. 2. Elevation profiles of HCHs, HCB, andaldrin in Rouzi

Fig. 3. Elevation profiles of DDT components inRouzi

Table 6. R2 values obtained for the correlation between concentrations of target compounds and elevation

Grass a-HCH c-HCH HCB Aldrin p,p�-DDE p,p�-DDD o,p�-DDT p,p�-DDT o,p�-DDE o,p�-DDD

Rouzi 0.712 0.931 0.774 0.804 0.952 0.925 0.471 0.0533 0.948 0.471Jidou 0.629 0.887 0.834 0.693 0.889 0.943 0.277 0.0064 0.876 0.561

158 X.-P. Wang et al.

DDT are similar (Bidleman et al. 1987), the o-p�-DDT/p-p�-DDT ratios should be close to 0.175. However, the average ofthe ratios observed in this study of o-p�-DDT/p-p�-DDT in soilsamples was 0.226, and the average of the grass sample ratiosof o-p�-DDT/p-p�-DDT was 0.533. We conclude that the o-p�-DDT in samples from Mt. Qomolangma did not come fromresidue but from a ‘‘new’’ source. This source exhibits higherproportions of o-p�-DDT and therefore could not be derivedfrom technical DDT. Based on similarly high o-p�-DDT con-centrations in the air in Arctic regions (Hung et al. 2002) and atTaihu Lake, China (Qiu et al. 2004), investigators deduced thatother new pesticides with prohibited DDT components maystill be used and produced. According to our results, high o-p�-DDT concentrations on Mt. Qomolangma, a remote region inthe world, support this deduction, and the sources of newpesticides with DDT components may be close to this region.

DDE is not used as an insecticide by itself and in theenvironment but results mainly from the degradation of DDT.It follows that the ratio of p-p�-DDE/p-p�-DDT in soil and grasscan be used as an indicator of the ‘‘age’’ of the source DDT(Raport et al. 1986). Higher DDE/DDT ratios indicate oldersources because DDT degrades primarily to DDE (De Marchet al. 1998). Our study detected both DDT and DDE in sam-ples, and the average ratio of p-p�-DDE/p-p�-DDT was 0.862for soil samples and 1.539 for grass samples, suggesting recentsources of DDT in this region. If the technical DDT in theenvironment had already been degrading for a long time, onewould not expect to find such high concentrations of both DDTand DDE in this region. More likely, a new source existed thatcontained p-p�-DDT. Figure 5 shows how our observed ratiosof p-p�-DDE to p-p�-DDT increase with elevation, suggestingthat although little p-p�-DDT was deposited at higher

Fig. 4. Elevation profiles of total HCHs andratios of a/c-HCH

Fig. 5. Elevation profiles of total DDTcomponents and the ratio of p-p�-DDE to p-p�-DDT

POPs Around Mt. Qomolangma, China 159

elevations (from Fig. 3), the corresponding DDE productsproduced by the degradation of DDT were maximal.

The high ratios of o-p�-DDT/p-p�-DDT and relatively lowratios of p-p�-DDE/p-p�-DDT lead to the suspicion that anew source of o-p�-DDT and/or p-p�-DDT exists. This newsource is likely the pesticide dicofol, which is widely usedin India. Dicofol is an organochlorine acaricide with littleinsecticidal activity. In India, it is mainly used to controlmites on tea and kitchen gardens and is produced by Hin-dustan Insecticide Ltd., New Delhi, India (UNEP report).Saha et al. (2004) examined the persistence of dicofol anddicofol residues in ecologic systems. The concentration ofDDT components in technical dicofol is high; the content ofDDT was up to 575 g/kg dicofol product, and o-p�-DDT andaccounted for approximately 77% of these DDT impurities(Rasenberg and Van de Plassche 2003). This source mayhave caused the high o-p�-DDT and p-p�-DDT concentrationsamong the samples of this study. We found no previousreports of detailed research into the effects of dicofol pro-duced by Indian factories on the ecosystem of Himalayanregions and only limited data about the content of DDTs indicofol. Apparently, further research is required to answerthese questions.

Biological Concentration Factor Values for Grass Samples

Biological Concentration Factor (BCF) values describe theaccumulation of chemicals in organisms, relating pollutantresidues in organisms to those in the environment. A BCFvalue can be calculated from the ratio of OCP concentrationsin grass to those in soil. The BCF values calculated in thisstudy show that DDT pollutants have been accumulating inthe sampled grasses. Concentrations of DDT components ingrass samples exhibited a 5- to 20-fold increase comparedwith the values in soil. Figure 6 displays the trends of BCF

values for two species of grass with increasing elevation.From Figure 6 we can see that the higher the elevation, thehigher the BCF value, which means higher concentrations ofDDT accumulate at the higher elevation sites. BCF valuessharply increase at the highest elevations, suggesting thehighest DDT accumulation per unit mass of grass in high-elevation mountain regions.

Kelly and Gobas (2001) investigated the bioaccumulation ofPOPs in lichen–caribou–wolf food chains in the Canadiancentral and western Arctic. They defined bioaccumulativesubstances as those compounds with octanol–water partitioncoefficients (Kow) >105. They demonstrated that chemicalswith Kow values <105 may bioconcentrate in organisms but notsignificantly biomagnify in food chains. Based on the Kow

values reported by Villa et al. (2003), DDD, DDT, and DDEexhibit Kow logarithms of 6.21, 6.91, and 6.95, respectively,which indicate that DDT and its metabolites are bioaccumu-lative substances and can be biomagnified along the foodchain. We found that the highest BCF values for DDT andDDD were >50, indicating a high potential of these pollutantsto accumulate in grasses, where they could be harmful to yakor sheep. The food web structure at Mt. Qomolangma appearsfairly linear (i.e., grass–yak/sheep–human beings). Thus, highaccumulations of OCPs in grasses could expose humans topollutants. Given the global distribution of OCPs and thecurrent, or at least recent, use of OCPs in developing regions,the fate of POPs in high-elevation mountain regions and theirimpact on ecosystems take on critical importance.

The study of OCPs in grass species may be important forinvestigating the bioaccumulation of these pollutants. In thisstudy, Rouzi (T. rupifragum Schrenk) always showed greateraccumulation than Jidou (Oxytropis glacialis Benth.ex Bge), asindicated by the high BCF values shown in Figure 6. Theaverage lipid concentration of Rouzi on a dry-weight basis was2.45%, and the value for Jidou was 5.25%. Generally, highlipid content might be expected to yield high accumulation

Fig. 6. BCF values from grass samples

160 X.-P. Wang et al.

ability (Calamari et al. 1991). However, Rouzi, with its lowlipid content, shows the higher accumulation capacity, imply-ing that other characteristics of the grasses, such as surface areaand degradation ability, might also be involved. Many re-searchers have used pollutant concentrations in vegetation toqualitatively indicate atmospheric contamination levels. Veg-etation samples are much easier to collect than air or animalsamples and thus are frequently employed, especially in remotemountain locations. Vegetation has been reported to be a goodindicator for investigating point sources of organic pollutants,spatial distribution patterns of pollutants, and the impact ofpollutants on ecosystems (Daly and Wania 2005). Althoughthere are some advantages in monitoring pollution levels byvegetation, there remain many undetermined factors regardingvariations between vegetation species, lipid concentrations,and uptake and degradation rates for different pollutants; thus,collecting many types of samples is advisable.

Conclusion

This study provides a first set of concentration data for orga-nochlorine pesticides in snow, soil, and grasses on Mt. Qomo-langma. This study detected only DDT components in the snowand soil samples, whereas other OCPs (HCH, HCB, and endo-sulfan, in addition to DDT components) were detected in grasssamples. The fate of OCPs in this mountain region appearsstrongly affected by both a ‘‘cold-condensation effect’’ andvolatility of the chemicals. Our data suggest the likelihood ofcontinuing sources of OCPs in the surrounding regions. Wefound the more volatile pollutants prone to concentrate at thehigher and colder sites and vice versa. We measured high bio-accumulation in the grass samples from the higher elevationsites, suggesting possible further bioaccumulation of OCPs inthe food chain. Further work on the associated risks to the eco-systems ofMt.Qomolangma region and human health is needed.

Acknowledgments. This study was supported by the InnovationProgram of Chinese Academy of Sciences (KZCX3-SW-339), theNational Basic Research Program of China (2005CB422004), and theNational Natural Science Foundation of China (40121101, 40401054,and 40501018).

References

Bidleman T E, Wideqvist U, Jansson B, Soderlund R (1987) Orga-nochlorine pesticides and polychlorinated biphenyls in theatmosphere of southern Sweden. Atmos Environ 21:641–654

Bidleman TF (1999) Atmospheric transport and air-surface exchangeof pesticides. Water Air Soil Pollut 115:115–166

Calamari D, Bacci E, Focardi S, Gaggi C, Morosini M, Vighi M(1991) Role of plant biomass in the global environmental parti-tioning of chlorinated hydrocarbons. Environ Sci Technol25:1489–1495

Daly GL, Wania F (2005) Organic contaminants in mountains.Environ Sci Technol 39:385–398

Davidson DA, Wilkinson AC, Blais JM, Kimpe LE, McDonald KM,Schindler DW (2003) Orographic cold-trapping of persistent or-ganic pollutants by vegetation in mountains of western Canada.Environ Sci Technol 37:209–215

Fang JY, Kanzaki M, Wang XP, Yoda K, Sun S, Shimota K (2004)Community structure of alpine sparse vegetation and effects ofmicrotopography in Pushila, Everest-Choyu region, Tibet, China.Biodiversity Sci 12:190–199

Finizio A, Villa S, Raffaele F, Vighi M (2006) Variation of POPconcentrations in fresh-fallen snow and air on an Alpine glacier(Monte Rosa). Ecotoxicol Environ Safe 63:25–32

Grimalt JO, van Drooge BL, Ribes A, Vilanova RM, Fernandez P,Appleby P (2004a) Persistent organochlorine compounds in soilsand sediments of European high altitude mountain lakes. Che-mosphere 54:1549–1561

Grimalt JO, Borghini F, Sanchez-Hernandez JC, Barra R, Garcia CJT,Focardi S (2004b) Temperature dependence of the distribution oforganochlorine compounds in the mosses of the Andean moun-tains. Environ Sci Technol 38:5386–5392

Herbert BMJ, Halsall CJ, Fitzpatrick L, Villa S, Jones KC, ThomasGO (2004) Use and validation of novel snow samplers forhydrophobic, semi-volatile organic compounds (SVOCs). Che-mosphere 56:227–235

Hung H, Halsall CJ, Blanchard P, Li HH, Fellin P, Stern G, et al.(2002) Temporal trends of organochlorine pesticides in theCanadian Arctic atmosphere. Environ Sci Technol 36:862–868

Iwata H, Tanabe S, Tatsukawa NSR (1993) A new view on thedivergence of HCH isomer compositions in oceanic air. MarPollut Bull 26:302–305

Kelly BC, Gobas FAPC (2001) Bioaccumulation of persistent organicpollutants in lichen-caribou-wolf food chains of Canada�s centraland western Arctic. Environ Sci Technol 35:325–334

Law SA, Diamond ML, Helm PA, Jantunen LM, Alaee M (2001)Factors affecting the occurrence and enantiomeric degradation ofhexachlorocyclohexane isomers in northern and temperate aqua-tic systems. Environ Toxicol Chem 20:2690–2698

Li J, Zhu T, Wang F, Qiu XH, Lin WL (2006) Observation of orga-nochlorine pesticides in the air of the Mt. Everest region. Eco-toxicol Environ Safe 63:33–41

Li YF, McMillan A, Scholtz MT (1996) Global HCH use with 1�·1�longitude/latitude resolution. Environ Sci Technol 30:3523–3533

Loewen MD, Sharma S, Tomy G, Wang F, Bullock P, Wania F (2005)Persistent organic pollutants and mercury in the Himalaya. AquatEcosyst Health Manage 8:223–233

Metcalf RL (1955) Organic insecticides, their chemistry and mode ofaction. Interscience, New York

Migaszewske ZM (1999) Determining organic compound ratios insoils and vegetation of the Holy Cross Mts, Poland. Water AirSoil Pollut 111:123–138

Oehme M (1991) Further evidence for long-range air transport ofpolychlorinated aromates and pesticides-North America andEurasia to the Arctic. Ambio 20:293–297

Picer M, Picer N, Holoubek I, Klanova J, Kobasic VH (2004) Chlo-rinated hydrocarbons in the atmosphere and surface soil in theareas of the city of Zadar and Mt. Velebit Croatia. FreseniusEnviron Bull 13:712–718

Qiu XH, Zhu T, Jing L, Pan HS, Li QL, Miao GF, Gong JC (2004)Organochlorine pesticides in the air around the Taihu Lake,China. Environ Sci Technol 38:1368–1374

Rasenberg MHC, van de Plassche DJ (2003) Dicofol dossier preparedfor the meeting March 17-19 in Norway of the UNECE. Ad-hocExpert Group on POPs, 4L0002.A1/R0011/EVDP, January

Rappot RA, Eisenreich SJ (1986) Atmospheric deposition of toxa-phene to eastern North America derived from peat accumulation.Atmos Res 20:2367–2379

Risebrough EW, Walker WI, Schmidt TT, Delappe BW, Connors CW(1976) Transfer of chlorinated biphenyls to Antarctica. Nature264:738–739

Saha K, Saha T, Banerjee H, Bhattacharyya A, Chowdhury A, Som-choudhury AK (2004) Persistence of dicofol residue on tea under

POPs Around Mt. Qomolangma, China 161

North-East Indian climatic conditions. Bull Environ ContamToxicol 73:347–350

Villa A, Finizio A, Diazdiaz R, Vighi M (2003) Distribution oforganochlorine pesticides in pine needles of an oceanic island:The case of Tenerife (Canary Islands, Spain). Water Air SoilPollut 146:335–349

Vives I, Grimalt JO, Lacorte S, Guillam�n M, Barcel� D, RosselandBO (2004) Polybrominodiphenyl ether flame retardants in fishfrom lakes in European high mountains and Greenland. EnvironSci Technol 38:2338–2344

Wania F, Mackay D (1995) A global distribution model for persistentorganic chemicals. Sci Total Environ 160/161:211–232

Wania F, Mackay D (1996) Tracking the distribution of persistentorganic pollutants. Environ Sci Technol 30:390A–396A

Weiss P, Lorbeer G, Scharf S (1998) Persistent organic pollutants inremote Austrian forests-Altitude-related results. Environ SciPollut Res Special Issue No. 1:46–52

Weiss P, Lorbeer G, Scharf S (2000) Regional aspects and statisticalcharacterization of the load with semivolatile organic compoundsat remote Austrian forest sites. Chemosphere 40:1159–1172

162 X.-P. Wang et al.