increased concentrations of dissolved trace metals and organic carbon during snowmelt in rivers of...

doi:10.1016/S0016-7037(03)00458-7

Increased concentrations of dissolved trace metals and organic carbon during snowmelt inrivers of the Alaskan Arctic

ROBERT D. REMBER* and JOHN H. TREFRY

Department of Marine and Environmental Systems, Florida Institute of Technology, Melbourne, FL 32901, USA

(Received December 20, 2002;accepted in revised form July 1, 2003)

Abstract—Arctic rivers typically transport more than half of their annual amounts of water and suspendedsediments during spring floods. In this study, the Sagavanirktok, Kuparuk and Colville rivers in the AlaskanArctic were sampled during the spring floods of 2001 to determine levels of total suspended solids (TSS) anddissolved and particulate metals and organic carbon. Concentrations of dissolved organic carbon (DOC)increased from 167 to 742�mol/L during peak discharge in the Sagavanirktok River, at about the same timethat river flow increased to maximum levels. Concentrations of dissolved Cu, Pb, Zn and Fe in theSagavanirktok River followed trends observed for DOC with 3- to 25-fold higher levels at peak flow thanduring off-peak discharge. Similar patterns were found for the Kuparuk and Colville rivers, where averageconcentrations of dissolved trace metals and DOC were even higher. These observations are linked to a largepulse of DOC and dissolved metals incorporated into snowmelt from thawing ponds and upper soil layers. Incontrast with Cu, Fe, Pb and Zn, concentrations of dissolved Ba did not increase in response to increaseddischarge of water, TSS and DOC. Concentrations of particulate Cu, Fe, Pb and Zn were more uniform thanobserved for their respective dissolved species and correlated well with the Al content of the suspendedparticles. However, concentrations of particulate Al were poorly correlated with particulate organic carbon.Results from this study show that�80% of the suspended sediment and more than one-third of the annualinputs of dissolved Cu, Fe, Pb, Zn and DOC were carried to the coastal Beaufort Sea in 3 and 12 d,respectively, by the Kuparuk and Sagavanirktok rivers.Copyright © 2004 Elsevier Ltd

1. INTRODUCTION

Most rivers that drain into the Arctic Ocean carry 40 to 80%of their annual volume of water during the spring floods (Arn-borg et al., 1967; Gordeev et al., 1996). In addition to waterdischarge, Telang (1985) showed that�35% of the annualdischarge of dissolved organic carbon (DOC) into the CanadianBeaufort Sea from the Mackenzie River occurred during theJune snowmelt. Similar results have been reported for the LenaRiver where concentrations of DOC decreased from�1000�mol/L during spring floods in June to 600 to 700�mol/Lduring September (Cauwet and Sidorov, 1996). Studies in theAlaskan Arctic have shown that concentrations of total sus-pended solids (TSS) in the Colville River follow the same trendas water flow with�70% of the annual discharge of TSSoccurring during June (Arnborg et al., 1967). Large seasonaldischarges of water at high latitudes, linked with increasedconcentrations of TSS and DOC, emphasize the importance ofspring floods to the arctic hydrologic cycle.

Few studies in the Arctic have investigated trends in rivertransport of trace metals during the spring floods. Data fordissolved and particulate trace metals in the Arctic are availablefor some rivers in Russia; however, these investigations havefocused on the open water period from July to September ratherthan the spring floods when water discharge and concentrationsof TSS and DOC peak (Martin et al., 1993; Dai and Martin,1995; Guieu et al., 1996; Zhulidov et al., 1997; Moran andWoods, 1997). Reported concentrations of dissolved and par-ticulate trace metals in wetlands, rivers and estuaries of the

Russian Arctic are 1.5 to 3 times lower than concentrations inother major, non-arctic rivers (Martin et al., 1993). Such resultssuggest that rivers in the Russian Arctic are less influenced bychemical weathering or anthropogenic contamination.

In contrast to the Russian Arctic, very few studies of tracemetals have been carried out for rivers in the Alaskan Arctic.Instead, geochemical research in the Alaskan Arctic has con-centrated on TSS, major elements, nutrients and DOC in riversas well as streams, lakes and ponds (Brown et al., 1962; Locket al., 1989; Telang et al., 1991; Kling et al., 1992; Kriet et al.,1992). Similar to the studies in Russia, sampling in the AlaskanArctic has focused on the open water period from July toSeptember.

A large gap exists in our knowledge of riverine concentra-tions and transport of trace metals and organic carbon in theAlaskan Arctic, especially during peak discharge in the spring.In this investigation, concentrations of dissolved and particulateBa, Cu, Fe, Pb, Zn and organic carbon in the Sagavanirktok,Kuparuk and Colville rivers of arctic Alaska were determinedthroughout the spring thaw and again during the summer (Fig.1). The primary sites occupied during this investigation werenear river mouths to provide representative values for thecomposition of water flowing into the coastal Beaufort Sea.

2. STUDY AREA

The Sagavanirktok, Kuparuk and Colville rivers lie withinthe Arctic climatic zone where annual temperatures average–12°C and mean precipitation is�12 cm/yr�1 (Fig. 1) (Telanget al., 1991). The drainage basins of Arctic rivers in Alaskainclude the following three physiographic provinces: the ArcticMountain Province, the Arctic Foothills Province, and the

* Author to whom correspondence should be addressed([email protected]).

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Geochimica et Cosmochimica Acta, Vol. 68, No. 3, pp. 477–489, 2004Copyright © 2004 Elsevier Ltd

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477

Arctic Coastal Plain Province (Payne et al., 1951). Based on theclassification scheme proposed by Craig and McCart (1975),the Sagavanirktok and Colville rivers can be classified asmountain streams that drain snowfields and glaciers in theBrooks Range. In contrast, the yellow-colored water of theKuparuk River is more representative of a tundra stream (Locket al., 1989). All three rivers flow into the coastal Beaufort Sea.

The geology of the region was summarized by Payne et al.(1951). Marine and non-marine sediments including peat de-posits from the Quaternary underlie the coastal plain. Tertiarydeposits from the Sagavanirktok Formation (limestone, chert)are exposed on the coastal plain in the Kuparuk and Sagava-nirktok basins. Shales from the Triassic to Cretaceous areexposed in the Foothills Province and Brooks Range. TheLisburne limestone and dolomite group from the Mississippianand Pennsylvanian ages are concentrated in the eastern BrooksRange within the drainage basin of the Sagavanirktok River(Payne et al., 1951). Previous studies have shown that theSagavanirktok River drains primarily limestone deposits andhas concentrations of dissolved Ca that are �2 times higherthan in the Kuparuk and Colville rivers (Telang et al., 1991).Walker and Webber (1979) show that westward of the carbon-

ate-rich Sagavanirktok River, soil pH decreases from �7 to �6as the tundra shifts from wet alkaline to wet acidic becausesoils become rich in organic acids.

The Kuparuk River drains an area of 8140 km2 and istypically frozen for 7 to 9 months of the year (Hinzman et al.,1991). Water flow usually reaches the coast in late May or earlyJune, largely due to discharge of melted snow that has accu-mulated during the winter months (McNamara et al., 1998).During the initial surge of snowmelt, water discharge rangesfrom 500 to 3500 m3/s at peak flow and then decreases to �100m3/s within 1 to 2 weeks (U.S. Geological Survey [USGS],1971–2001). In 2001, the Kuparuk River transported 1.2 km3 ofwater with �75% of the discharge in June (USGS, 2001).During a 3-yr study of the upper drainage basin of the KuparukRiver, Kriet et al. (1992) determined that concentrations of TSSranged from 0.4 to 35 mg/L with sediment yields of 0.5 to3.5 t/km2/yr (average � 1.6 t/km2/yr). The entire drainagebasin is underlain by permafrost that ranges in thickness from250 m near the foothills to �600 m near the coast (Osterkampand Payne, 1981). The active soil layer tends to increase indepth throughout the summer months and typically thaws tomaximum depths of 25 to 40 cm (Hinzman et al., 1991).

The Sagavanirktok River is the second largest river on theNorth Slope with a drainage area of �15,000 km2 that extends287 km from the Brooks Range to the Beaufort Sea (Robinsonand Johnsson, 1997). Similar to the Kuparuk River, springdischarge of accumulated snowmelt occurs during late May toearly June with a peak discharge that ranges from �300 to1200 m3/s at the USGS gauge (USGS, 1971–2001, Table 1,Fig. 1). However, discharge does not decrease as rapidly duringJune in the Sagavanirktok River as in the Kuparuk River,presumably due to the larger drainage basin and additionalsources of water from snowfields and glaciers in the BrooksRange (McNamara et al., 1998). Water discharge at the Saga-vanirktok River gauge (#15908000) totaled 1.3 km3 in 2001(USGS, 2001). However, the gauge receives water flow fromonly �20% of the drainage basin and thus total water dischargeinto the coastal Beaufort Sea is conceivably �5 times greater(USGS, 1971–2001; Robinson and Johnsson, 1997). DuringJune 2001, water discharge at the Sagavanirktok gauge ac-counted for 35% of the total annual discharge. Data for con-centrations of TSS or sediment yield were not available.

The Colville River, the largest river in the Alaskan Arctic,extends for 600 km and encompasses �57,000 km2 in all three

Fig. 1. Map showing sampling locations for the Sagavanirktok,Kuparuk and Colville rivers in the Alaskan Arctic. The northernmoststations on the Sagavanirktok, Kuparuk and Colville rivers are theprimary sampling sites. The southernmost location marked on theSagavanirktok River is at the site of the U.S. Geologic Survey gaugingstation. Snow samples were collected from the station located �30 kmupstream from the primary sampling site on the Sagavanirktok River.Box in inset map identifies the study area in northeastern Alaska.

Table 1. Locations of sampling sites and U.S. Geological Survey(USGS) gauges.

SiteSample

typeLatitude

(N)Longitude

(W)

Sagavanirktok River(near Prudhoe Bay)

Water 70°15.033� 148°18.484�

Sagavanirktok River Snow 70°01.684� 148°37.781�Sagavanirktok River

(USGS gauge)Flow 69°00.527� 148°49.214�

Kuparuk River Water 70°19.812� 149°00.527�Kuparuk River

(USGS gauge)Flow 70°16.540� 148°57.350�

Colville River Water 70°09.519� 150°56.791�

478 R. D. Rember and J. H. Trefry

physiographic provinces. The USGS no longer maintains agauge on the Colville River; however, data from 1976 to 1977indicate that peak discharge approaches 8500 m3/s (USGS,1971–2001). Arnborg et al. (1967) calculated water dischargeand suspended sediment transport by the Colville River for1962 and found that �15 km3 of water and �6 � 106 tons ofsuspended sediment (116 t/km2/yr) are discharged annually.

3. SAMPLING AND ANALYSIS

3.1. Sampling

River sampling during the spring snowmelt was carried outduring June 2001. The Sagavanirktok River was sampled 20times between June 3 and June 23 from a location near PrudhoeBay (Table 1, Fig. 1). Sampling of the Kuparuk River wascarried out nine times between June 10 and June 22, and theColville River, not easily accessible, was sampled five times inJune when helicopter support was available (Table 1, Fig. 1).Water samples also were collected from the Sagavanirktok andKuparuk rivers during August 2001 and 2002 and the ColvilleRiver during August 2001. Four snow samples were collectedduring May 2002 adjacent to the Sagavanirktok River at alocation �30 km upstream of Prudhoe Bay (Table 1, Fig. 1).

Water samples were collected using 0.5- and 1-L low-densitypolyethylene (LDPE) bottles that were carefully washed withconcentrated HNO3 and rinsed twice (24 h per rinse) with18-megaohm distilled deionized water (DDW) before sam-pling. Samples from the Sagavanirktok and Kuparuk riverswere collected below the surface (�10–20 cm) by lowering apolyvinyl chloride (PVC) bottle holder from a bridge into therivers. The PVC sampler weighed �14 kg, thereby allowingthe sample bottle to remain vertical and relatively stationary inthe water column during sampling. Water from the ColvilleRiver was collected by hand using LDPE bottles while standingin the river and facing or walking slowly upstream. Snowsamples were collected along the riverbanks and above thefrozen river using wide mouth high-density polyethylene(HDPE) containers that were washed with concentrated HNO3

and rinsed twice (24 h per rinse) with DDW. The surface snow(�5 cm) was discarded and subsurface samples were collectedusing an HDPE scoop and the containers were sealed in plasticbags.

Water samples were collected and filtered in a laminar flowhood at a laboratory near Prudhoe Bay during the same day,usually within 1 to 4 h of collection. Snow samples were

thawed at the laboratory and filtered immediately. The filteringunit was acid washed (5 N HNO3), rinsed with distilled waterbefore each filtration and the first 20 to 50 mL of filtrate werediscarded as an additional rinse. Levels of TSS were deter-mined by filtering 0.025 to 1 L of water through preweighedand acid-washed (5 N HNO3) polycarbonate filters (0.40 �m,47 mm) in a laminar-flow hood to minimize contamination. Thefilters containing suspended solids were placed in acid-washedpetri dishes and stored in plastic bags. The filtrate was placedin acid-cleaned polyethylene bottles and acidified to pH 2 withUltrex II HNO3 and stored in plastic bags. A separate portionof river water to be analyzed for particulate organic carbon(POC) was filtered through precombusted (500°C) GelmanType A/E glass-fiber filters (47 mm). The filters were stored inpetri dishes and sealed in plastic bags. The filtrate was collectedfor DOC, transferred to glass vials with Teflon-lined caps andfrozen until analysis.

3.2. Analysis

3.2.1. Dissolved metals

Concentrations of dissolved Ba and Cu in the filtered andacidified water samples were determined by Inductively Cou-pled Plasma Mass Spectrometry (ICP-MS) using a Perkin-Elmer ELAN 5000 instrument. Dissolved Fe concentrationswere determined for the acidified samples by graphite furnaceatomic absorption spectroscopy (GFAAS) using a Perkin-Elmer Model 4000 instrument with an HGA-400 heated graph-ite atomizer and an AS-40 autosampler. Accuracy was assessedusing the certified reference material (CRM) SLRS-3, from theNational Research Council of Canada (NRC), or the standardreference material (SRM) NIST-1640, from the U.S. NationalInstitute of Standards and Technology (NIST), with all valueswithin the range of certified concentrations (Table 2). Acidblanks were prepared before analysis and were below detectionlimits of 0.7, 0.05, and 0.18 nmol/L, for Ba, Cu and Fe,respectively. Spiked samples were used to determine recoveriesfor dissolved Ba, Cu and Fe that averaged 94% (n � 4), 97%(n � 4) and 96% (n � 4), respectively. The precision ofreplicate analyses (n � 4) averaged 5% for Ba, 7% for Cu and9% for Fe.

Concentrations of dissolved Pb and Zn were determined in asubset of the samples from July and August (SagavanirktokRiver, n � 14; Kuparuk River, n � 7; Colville River, n � 5)by preconcentrating the metals from filtered water samples

Table 2. Results for river water reference materials.

SLRS-3 certifiedconcentrationsa

(nmol/L)

NIST-1640 certifiedconcentrationsa

(nmol/L)

This studyb

(preconcentration)(nmol/L)

This studyb

(direct analysis)(nmol/L)

Ba (n � 3) — 1078 16 — 1070 13Cu (n � 5) 21.3 1.1 — — 21.6 0.6Fe (n � 3) 1791 35.8 — — 1808 4Pb (n � 5) 0.42 0.03 — 0.41 0.03 —Zn (n � 5) 15.9 1.4 — 16.1 0.8 —

a 95 confidence limits.b 1 standard deviation.

479Trace metals and organic carbon in Alaskan Arctic rivers

(�400 mL) in a laminar flow hood using the technique de-scribed by Nakashima et al. (1988). In this procedure, highpurity Fe, Pd and NaBH4 are used to co-precipitate the dis-solved metals at pH 8.5. The precipitate is collected on acid-washed filters and then dissolved in Ultrex II HNO3 and UltrexII HCl and diluted to a final volume of �4 mL. The concen-tration factor is �100-fold using this method. Concentrationsof dissolved Pb and Zn were determined by ICP-MS withdetection limits of 10 pmol/L and 0.15 nmol/L, respectively.Recoveries of dissolved Pb and Zn from spiked samples aver-aged 98% (n � 4) and 92% (n � 4), respectively. The precisionof replicate analyses averaged 6% for Pb (n � 4) and 9% for Zn(n � 4). A dissolved metal blank was prepared with thefollowing reagents used in the preconcentration technique: 1mL Ultrex II NH4OH, 1 mL of each of the Fe and Pd carriersand 2.5 mL of the NaBH4. The precipitate from the blank wasfiltered and dissolved in Ultrex II HNO3 and Ultrex II HCl andwas equivalent to 0.30 0.03 nmol/L for Zn (n � 4) and 36 4 pmol/L for Pb (n � 4). Concentrations of dissolved Pb and Znin this paper are blank corrected. Concentrations of dissolvedPb and Zn determined for the CRM SLRS-3 during this studywere within the range of certified concentrations (Table 2).

3.2.2. Particulate metals

Filters containing 1 to 15 mg of suspended sediment weredried in a humidity-controlled (50% relative humidity) cleanroom for 24 h and weighed to 1 �g. The suspended sedimentwas dissolved using the method described by Trefry and Tro-cine (1991). Briefly, the filters with suspended sediment wereplaced in stoppered, 15-mL Teflon test tubes and the suspendedsediment was completely decomposed and dissolved usingUltrex II HNO3, HF and HCl. The test tubes were heated at�75°C in a water bath, cooled and reheated. The resultantsolutions were transferred to acid-washed LDPE bottles anddiluted to 6 mL using DDW rinses of the test tubes. Smallportions (�5–10 mg) of SRM 2704, a marine sediment fromNIST, and filter blanks also were prepared in duplicate witheach set of samples to assess accuracy and precision.

Concentrations of Al, Fe and Zn in suspended particles weredetermined by flame atomic absorption spectroscopy using aPerkin-Elmer 4000 instrument. Concentrations of Cu werequantified by GFAAS. Values for particulate Ba and Pb weredetermined by ICP-MS. Values for filter blanks were below themethod detection limits of 0.15%, 0.15%, 9 �g/g, 0.4 �g/g, 0.2�g/g and 2 �g/g for Al, Fe, Ba, Cu, Pb and Zn, respectively.Concentrations of metals determined for the SRM were withinthe range of certified concentrations (Table 3). The precision ofreplicate analyses averaged 3% for Al (n � 4), 4% for Fe (n �4), 4% for Ba (n � 4), 6% for Cu (n � 4), 4% for Pb (n � 4)and 7% for Zn (n � 4).

3.2.3. Organic carbon

Filters for POC were treated with 15% H3PO4 to removeinorganic carbon phases, rinsed with DDW and dried. Thefilters were placed in ceramic boats and combusted at 900°C ina Shimadzu TOC-5050A carbon system with an SSM-5000Asolid sampling module. The organic carbon content of thesamples was determined using a four-point calibration curve

with pure sucrose as the standard. The calibration curve waschecked every 10 samples by analyzing the CRM MESS-2, amarine sediment issued by the NRC. Values for the CRM werewithin 5% of certified concentrations (Table 3). The precisionof the POC analysis for replicate samples averaged 6.9% (n �4).

The DOC concentrations of river water were determined bycombustion using a Shimadzu TOC-5050A carbon system. TheDOC concentrations were calculated by subtracting inorganiccarbon (IC) from total carbon (TC). Four-point calibrationcurves were prepared using potassium hydrogen phthalate (TC)and sodium bicarbonate (IC). The calibration curve waschecked every 10 samples by repeating the analysis of amidrange standard. The precision of replicate analyses aver-aged 4.1% (n � 7) for the DOC analyses.

4. RESULTS AND DISCUSSION

4.1. Total Suspended Solids and Water

Concentrations of TSS increased from �40 to �600 mg/L inthe Sagavanirktok River during the first 8 d of water flow (June4–12, 2001) and decreased to �50 mg/L within 4 to 5 dfollowing maximum flow (Fig. 2a). Data for water flow at theUSGS gauge, located �150 km upstream, followed a similartrend. A 1- to 2-d offset between the peaks in TSS and waterflow is consistent with a lag time for flow between the USGSgauge and the primary sampling site located �150 km down-stream (Fig. 2a). Uncertainty in the water flow data, along withthe upstream location of the gauge, make it difficult to evaluatepossible differences in timing between maximum levels of TSSand water flow.

The flow gauge in the Sagavanirktok River was not installedby the USGS until the river was free of ice on June 10, 2001,�7 d after water flow began. Thus, during 2001 and most otheryears, the ascending limb of the hydrograph is calculated, notmeasured for the Sagavanirktok River. Furthermore, becausethe gauge is upstream in the western drainage basin of theSagavanirktok River, the gauge covers only �20% of thewatershed and may not represent characteristic flow patternsfor the entire basin. During 2001, the total volume of watermeasured at the USGS gauge in the Sagavanirktok River was�1.3 km3, yielding a total extrapolated flow of �6.5 km3/yr(USGS, 1971–2001).

Concentrations of TSS in the Kuparuk River peaked at 66

Table 3. Results for sediment reference materials.

NIST-2704 certifiedconcentrationsa This studyb

Al (%) (n � 6) 6.11 0.16 6.15 0.09Ba (�g/g) (n � 6) 414 12 408 9.0Cu (�g/g) (n � 6) 98.6 5.0 102 2.1Fe (%) (n � 6) 4.11 0.1 4.11 0.1Pb (�g/g) (n � 6) 161 17 165 16Zn (�g/g) (n � 6) 438 12 430 1.3POC (%) (n � 7) 2.14 0.03c 2.04 0.06

a 95 confidence limits.b 1 standard deviation.c MESS-2 (NRC).


mg/L on June 10 and decreased to �4 mg/L within 7 d (Fig.2b). These TSS values are low relative to the SagavanirktokRiver and are more typical of an arctic river that has nosignificant mountain source of suspended solids (Craig andMcCart, 1975). The gauge on the Kuparuk River is locatedwithin �10 km of the coastal Beaufort Sea and covers �90%of the drainage basin. In 2001, water discharge by the KuparukRiver totaled �1.2 km3 (USGS, 1971–2001). The same proce-dure for gauge installation used for the Sagavanirktok River isfollowed for the Kuparuk River. Therefore, the initial waterflow in the Kuparuk River is estimated and not measured (Fig.2b).

Similar to the Sagavanirktok River, concentrations of TSSincreased to �600 mg/L in the Colville River during peakdischarge. No water discharge data are available for theColville River because the USGS no longer maintains a gaugeon the river. Arnborg et al. (1967) estimated annual waterexport by the Colville River to be �15 km3.

For the purposes of discussion in this paper, peak dischargesin the Sagavanirktok and Kuparuk rivers are operationallydefined as the periods of June 5 to 16 and June 10 to 12,respectively. During those periods, the discharge of TSS is �50mg/L and water flow rises to a maximum and then decreases tomore uniform values during June and throughout the summer(Fig. 2). Similar trends between water flow and concentrationsof TSS in the Sagavanirktok and Kuparuk rivers suggest thatTSS data from the Colville River can be used to help estimatepeak discharge from about June 6 to 14.

4.2. Dissolved Organic Carbon and Trace Metals

During the first 5 d of discharge (June 3–7), concentrationsof DOC in the Sagavanirktok River increased sharply from 167to 742 �mol/L, levels that are up to 6 times greater than duringoff-peak discharge later in June (Fig. 3a, Table 4). Similartrends for concentrations of DOC also were observed in theKuparuk and Colville rivers, where peak concentrations were1320 and 1100 �mol/L, respectively (Table 4, Fig. 3b). Higherconcentrations of soluble organic matter in the Kuparuk andColville rivers, relative to the Sagavanirktok River, reflectdifferences in the nature of the drainage basins as describedlater in this paper.

During peak discharge in June 2001, maximum concentra-tions of DOC in the Sagavanirktok, Kuparuk and Colville riverswere 2 to 6 times higher than minimum concentrations mea-sured during off-peak discharge in June (Table 4). Increasedconcentrations of DOC during peak flow are amplified withrespect to total transport by large increases in water discharge.However, maximum concentrations of DOC in the Sagavanirk-tok River occurred before maximum water discharge and thelag effect only strengthens this observation. Then, levels ofDOC decreased as water flow continued to increase, possiblydue to dilution by snowmelt.

Concentrations of DOC also have been observed to increaseduring peak water discharge in many rivers of the world (Cau-wet and Meybeck, 1987; Depetris and Paolini, 1991; Cauwetand Sidorov, 1996; Boyer et al., 1997). This phenomenon iscaused when snowmelt or rising water percolates through lit-

Fig. 2. Concentrations of total suspended solids (●), measured waterflow (E) and calculated water flow (�) in the (a) Sagavanirktok and (b)Kuparuk rivers during June 2001 using water discharge data from U.S.Geological Survey gauges #15908000 and #1589600, respectively. Theshaded areas indicate the period defined as peak discharge for eachriver.

Fig. 3. Concentrations of dissolved organic carbon and water dis-charge (dashed line) in the (a) Sagavanirktok (●) and (b) Kuparukrivers (Œ) during June 2001. The shaded areas indicate the perioddefined as peak discharge for each river.


terfall and DOC-rich interstitial water in the upper soil horizonwhere concentrations of DOC can be �8000 �mol/L (Boyer etal., 1997; Michaelson et al., 1998). Depetris and Paolini (1991)found that concentrations of DOC increased from �400 to 900�mol/L during a flooding event in the Orinoco River. A pos-itive correlation between DOC and water flow also was re-ported to occur in the Lena River where concentrations of DOCwere at least 30 to 40% higher during the spring floods thanduring September (Cauwet and Sidorov, 1996).

Concentrations of dissolved Fe, Cu, Pb and Zn follow trendsshown for DOC (Fig. 4). In the Sagavanirktok River, concen-trations of dissolved Fe increased sharply from 57 to 1290nmol/L in �7 d. Then, as flow decreased, concentrations ofdissolved Fe returned to �50 nmol/L within 8 d of maximumlevels. Concentrations of dissolved Cu, Pb and Zn in theSagavanirktok River also increased to maximum levels of 15nmol/L, 225 pmol/L and 6.7 nmol/L, respectively, during peakflow (Fig. 4). These maximum values at peak discharge are �3,5.5 and 6 times greater, respectively, than minimum levelsduring off-peak discharge in June and occur during the periodwhen water flow is highest, indicating that net transport ofdissolved metals, like DOC, is greatly enhanced during peakdischarge.

Strong correlations (r � 0.82) were found for DOC vs.dissolved Cu, Fe, Pb and Zn (Table 5). The trends, correlationsand timing for peak levels of trace metals and DOC support theidea that concentrations of dissolved metals and DOC arestrongly influenced by the discharge of soil interstitial waterand shallow surface water that is diluted by snowmelt andflushed from surrounding soils into the Sagavanirktok River.During the short summers, the arctic coastal plain is coveredwith pools of standing water and lakes where DOC accumu-lates and trace metals are leached from soils. The permafrost,along with a topography that averages �2 m on the coastalplain, inhibit lateral water flow during the summer months,

thereby extending the residence time of the surface water in thesystem (McNamara et al., 1998). Then, after the long frozenwinter (8–9 months), increased surface runoff in the springprovides a direct pathway for the release of accumulated andfreshly leached DOC and dissolved metals into the rivers fromthe thawing ponds and soils.

On June 3, 2001, the first day of water flow in the Sagava-nirktok River, concentrations of dissolved Cu, Fe, Pb and DOCin the river water were �3 to 25 times lower than at peak flow.Much of this early runoff preceded complete thawing of soilsand ponds and may have contained a significant snow compo-nent. Results for filtered snow samples collected for this studyare as follows: Cu, 0.91 0.47 nmol/L; Fe, 17.8 7.1 nmol/L;Pb, 30 7 pmol/L, Ba, 5 0.8 nmol/L and DOC, 56 6�mol/L. These concentrations of Cu, Fe, Pb, Ba and DOC insnow are 2 to 25 times lower than during the first day ofdischarge in June for the Sagavanirktok River and 7.5 to 86times lower than maximum levels during peak discharge (Table4). Thus, in the period before peak flow, concentrations ofdissolved metals and DOC in river water are low, yet somewhatelevated above values for snow. As melting of snow and soilsprogresses, dissolved metals and organic carbon that are re-leased from interstitial water and ponds are carried to the riversin increasing amounts during the brief period of acceleratedrunoff from the land.

Average concentrations of dissolved Fe, Pb, Zn and organiccarbon in the Kuparuk River during peak and off-peak dis-charge in June were �2 to 5 times higher than in the Sagava-nirktok River (Table 4). Concentrations of dissolved Cu in theKuparuk River are not significantly different (t test, � � 0.05,p � 0.05) during peak vs. off-peak flow in June. During peakdischarge, average concentrations of DOC, Cu, Fe and Pb in theColville River were 1.5 to 2 times higher than during off-peakflow (Table 4). In general, concentrations of dissolved metalsand DOC in the Colville River were higher than those found in

Table 4. Concentrations of dissolved metals, dissolved organic carbon (DOC) and total suspended solids (TSS) in the Sagavanirktok, Kuparuk andColville rivers during peak and off-peak discharge, June 2001.

RiverBa

(nmol/L)Cu

(nmol/L)Fe

(nmol/L)Pb

(pmmol/L)Zn

(nmol/L)DOC

(�mol/L)TSS

(mg/L)

Peak dischargeSagavanirktok (n � 9) Mean 229 13.2 755 153 3.7 480 267

SD 16 3.3 410 55 1.8 222 171Range 200–256 9.0–15.1 201–1290 75–225 2.0–6.7 167–742 78–609

Kuparuk (n � 3) Mean 142 12.6 3800 256 5.8 1170 63SD 11 1.2 484 3.8 0.4 136 6

Range 131–153 11.3–13.5 3250–4170 253–260 5.5–6.3 1050–1320 55–66Colville (n � 2) Mean 369 38.9 1450 290 2.1 835 468

SD 26 3.1 536 45 0.3 160 272Range 340–392 34.3–42.3 1066–1825 258–321 1.7–2.6 667–1100 333–610

Off-peak discharge in JuneSagavanirktok (n � 8) Mean 239 6.5 110 59 1.8 196 31

SD 13 1.4 48 24 0.5 65 12Range 225–231 4.6–8.8 51–170 34–92 1.2–2.4 117–408 14–40

Kuparuk (n � 6) Mean 171 12.1 1150 196 4.4 728 4.0SD 16 0.7 382 64 0.2 39 2.4

Range 135–194 11.2–12.7 658–2080 105–288 4.1–4.8 692–788 1.7–7.4Colville (n � 3) Mean 376 24.5 900 196 4.0 454 89

SD 24 1.8 770 43 1.5 160 41Range 359–393 23.3–26.3 357–1440 133–244 2.9–5.0 342–608 42–113


the Sagavanirktok River, but less than in the Kuparuk River(Table 4).

Higher concentrations of DOC and dissolved metals in theKuparuk and Colville rivers, relative to the SagavanirktokRiver, are most likely related to differences in regional lithol-

ogy and soil pH (organic acids). Parkinson (1977) found aninverse relationship between calcium carbonate equivalents andorganic matter concentrations in the region. These data suggestthat soils within the Kuparuk and possibly Colville drainagebasins may undergo more intense chemical weathering due to

Fig. 4. Concentrations of dissolved (a) Fe, (b) Cu, (c) Pb, (d) Zn and (e) Ba in the Sagavanirktok River during June 2001.The shaded areas indicate the period defined as peak discharge. The solid line on the Ba graph is the mean value and dashedlines represent 2 standard deviations from the mean.


higher concentrations of organic acids and lower pH, whereasthe carbonate-rich Sagavanirktok River drainage basin may bewell buffered from pH changes (Walker and Webber, 1979).

In contrast with Cu, Fe, Pb and Zn, concentrations of dis-solved Ba in the Sagavanirktok River vary by only 7% (CV� SD/x̄ � 100) during peak discharge (Table 4, Fig. 4).Concentrations of dissolved Ba are even less variable (CV�5%) during pre and postpeak discharge in June (Table 4, Fig.4). Dissolved Ba concentrations were �25% lower duringmaximum water flow as a result of dilution by snowmelt. Theseresults indicate that concentrations of dissolved Ba are notenhanced by flushing of metals from soils during peak flow andare consistent with other studies that show weak complexationbetween Ba and organic ligands (Dupre et al., 1999; Pokrovskyand Schott, 2002). Partitioning of Ba between dissolved andparticulate phases also may help control concentrations ofdissolved Ba as described later in this paper.

Concentrations of dissolved Ba in the Sagavanirktok (234 14 nmol/L), Kuparuk (171 16 nmol/L) and Colville (376 24 nmol/L) rivers (Table 4) are within the range (138–574nmol/L) reported by Guay and Falkner (1998) for the Mack-enzie River. These data support the conclusion by Guay andFalkner (1998) that concentrations of dissolved Ba in Arcticrivers of North America are higher than those determined forany of the Eurasian Arctic rivers (24–120 nmol/L). Guay andFalkner (1998) suggest that differences in concentrations be-tween arctic rivers in North America and Eurasia are due to thechemical composition and weathering characteristics withintheir respective drainage basins.

Concentrations of dissolved Ba, Cu, Pb, Zn and DOC duringAugust 2001 and August 2002, when water flow was greatly

reduced (�50 m3s), are consistent with or lower than concen-trations found in other arctic rivers during the months ofAugust and September (Table 6). For example, concentrationsof dissolved Pb during August (2001, 2002) in the Sagavanirk-tok, Kuparuk and Colville rivers range from 19 to 56 pmol/L.These values are within the broad range of concentrationsfound in the Yenisey (25–29 pmol/L), the Ob (55–83 pmol/L)and the Lena (80 pmol/L) rivers during September. Overall,concentrations of dissolved metals in arctic rivers of Alaska are5 to 10 times lower in August than during peak flow in June.

4.3. Particulate Trace Metals and Organic Carbon

Concentrations of particulate Cu, Pb, Zn (�g/g dry weight),Fe and OC (percentage dry weight) in the Sagavanirktok Riverare more uniform than observed for the dissolved species (Fig.5). In general, concentrations of Cu (CV � 8.5%), Pb (CV �11%), and Zn (CV �5.7%) are less variable than concentra-tions of Fe (CV �16%) and POC (CV �31%) (Table 7). Insharp contrast with dissolved Cu, Fe, Pb and Zn, particulateconcentrations of these four metals were poorly correlated withorganic carbon, and relatively well correlated with particulateAl (Table 8). The poor correlations for POC vs. Cu, Fe, Pb andZn suggest that POC does not play a significant role in con-trolling concentrations of particulate trace metals in the Saga-vanirktok River, but that aluminosilicates (clays) are moreimportant.

The trends in concentrations of particulate Ba in the Saga-vanirktok River follow closely with those observed for Fe, Cu,Pb and Zn, suggesting that concentrations of particulate Ba alsoare controlled by the aluminosilicate content of the suspendedsolids (Fig. 6a). The correlation coefficient for particulate Alvs. Ba for the Sagavanirktok River (r � 0.88) indicates thatvariations in particulate Ba concentrations result from shifts inAl concentrations during peak and off-peak discharge in June.When concentrations of particulate Ba from the Kuparuk andColville rivers are added to data for the Sagavanirktok River(Fig. 6a), a strong relationship between Al and Ba is stillobserved (r � 0.90). The data in Figure 6a include values fromall three rivers with a range of �2 to �600 mg/L for TSS, andconcentrations of POC ranging from �1 to �7%. Therefore,variations in concentrations of particulate Ba in the Sagava-

Table 5. Pearson’s correlations between dissolved trace metals anddissolved organic carbon (DOC) in the Sagavanirktok River duringJune 2001. All correlations are significant at p � 0.01.

Cu Fe Pb Zn

Cu 1Fe 0.86 1Pb 0.89 0.93 1Zn 0.79 0.90 0.90 1DOC 0.82 0.90 0.91 0.87

Table 6. Ranges and average concentrations of dissolved metals in arctic rivers during August and September.

River

Date (thisstudy) orreference

TSS(mg/L)

Ba(nmol/L)

Cu(nmol/L)

Fe(nmol/L)

Pb(pmol/L)

Zn(nmol/L)

DOC(�mol/L)

Sagavanirktok 8/11/01 1.8 285 4.1 38 27 0.52 928/2/02 0.70 288 3.5 — 19 1.4 310

Kuparuk 8/11/01 0.64 295 12 185 25 0.52 4258/2/02 0.16 349 9.8 — 29 0.75 325

Colville 8/11/01 6.5 540 11 68 56 0.49 316Lena 1, 2, 3 10–20 130 12–15 434–850 — 1.2 495–661Lena 4 5–7 — 9.7 410 80 5.3 —Ob-Irtysh 2, 5 — 100 29–38 430–654 55–83 — 614–829Yenisey 2, 5 — 125 22–30 251–317 25–29 — 334World Average 6, 7 — — 24 716 150 9.2 480

(1) Guieu et al. (1996); (2) Guay and Falkner (1998); (3) Cauwet and Sidorov (1996); (4) Martin et al. (1993); (5) Dai and Martin (1995); (6) Martinand Windom (1991); (7) Meybeck (1982).


nirktok, Kuparuk and Colville rivers result from dilution offine-grained aluminosilicates by larger-grained sands and othernon-aluminosilicate minerals. Concentrations of dissolved Bavary by a factor of 2 to 3 among rivers; however, thesevariations are directly proportional to concentrations of partic-ulate Ba. The average ratio for particulate Ba/dissolved Ba is 23 5 L/g for all samples (n � 31). The relatively uniform ratiosupports a direct relationship between dissolved Ba and ex-changeable particulate Ba; however, these results cannot beconfirmed by this study (Tables 4 and 7). Similar trends werenot observed for Cu, Fe, Pb and Zn.

During peak discharge, as the banks of the Kuparuk Rivererode and the river transports higher concentrations of TSS(�50 mg/L), concentrations of particulate Fe, Pb and Zn cor-relate well (r � 0.98, 0.76, 0.93, respectively) with levels ofparticulate Al and the metal/Al ratios agree within 15% withthe results found for the Sagavanirktok River (Fig. 6). How-ever, when TSS concentrations decrease to an average of 4mg/L in the Kuparuk River during off-peak discharge in June,the average Fe/Al ratio increases by �35% relative to the

Sagavanirktok River (Fig. 6b). These data suggest that elevatedconcentrations of particulate Fe (6400 nmol/L or 3.7% dryweight) relative to Al (14,600 nmol/L or 3.5% dry weight)during off-peak discharge may be influenced by high concen-trations of dissolved Fe (1150 nmol/L) in the Kuparuk Riverthat potentially enhance the formation of Fe hydrous oxides andincrease concentrations of particulate Fe. Similarly, concentra-tions of particulate Pb and Zn increase with Fe and are elevatedabove levels that would be predicted from the Al concentrationand possibly result from scavenging by hydrous Fe-oxides.

Average concentrations of particulate Cu, Fe and Pb in theColville River averaged 25 to 40% higher than concentrationsfound in the Sagavanirktok and Kuparuk rivers (Table 7).However, particles from the Colville River also had 50% higherconcentrations of Al indicating that sources of suspended sed-iments in the western Brooks Range are richer in fine-grainedaluminosilicates or less diluted by non-aluminosilicate minerals(Table 7). When concentrations of particulate metals are plottedvs. Al, they agree with the trend found for metals in theSagavanirktok River (e.g., Fig. 6).

Fig. 5. Concentrations of particulate (a) Ba, (b) Cu, (c) Fe, (d) Pb, (e) Zn and (f) POC in the Sagavanirktok River duringJune 2001. The solid line shows mean concentrations in each plot and dashed lines represent 2 standard deviations fromthe mean.


4.4. Transport of Water, Sediment, Trace Metals andOrganic Carbon

Values for transport of metals and organic carbon by riversto the coastal Beaufort Sea are difficult to calculate due tolimitations in flow and chemical data as well as possible con-tributions from summer rainstorms. Nevertheless, by compar-ing transport during peak discharge in June with transportduring the remainder of the year, a sense of the relative impor-tance of spring floods to annual budgets is obtained. Calcula-tions for material transport are presented here for the Kuparukand Sagavanirktok rivers because data for water flow are avail-able (USGS, 1971–2001).

Water discharge in the Kuparuk River was divided into threeperiods: (1) 0.3 � 1012 L (25% of total) during 3 d of flooddischarge in June, (2) 0.4 � 1012 L (33% of total) during the 21off-peak days in June and (3) 0.5 � 1012 L (42% of total)during the remaining 90 d of the water year (USGS, 1971–2001). By combining water flow data with average concentra-tions of DOC for each time period (Tables 4 and 6), 42% of theannual load of DOC ([0.25][1170 �mol/L]/[(0.25)(1170�mol/L) � (0.33)(728�mol/L) � (0.42)(375 �mol/L)] �100%) of the Kuparuk River is delivered to the Beaufort Sea in3 d. Using the same approach shown above for DOC, thefollowing fractions of the annual loads of dissolved metals arecarried by the Kuparuk River in 3 d of peak flow: Ba (16%), Cu(36%), Fe (67%), Pb (47%) and Zn (46%).

Using the USGS data for the Sagavanirktok River and as-suming that it represents flow for 20% of the system, then theannual flow can be scaled up and grouped as follows: (1) 1.0 �1012 L (17% of total) of peak flow during 12 d in June, (2) 1.2� 1012 L (18% of total) of off-peak flow during 16 d in Juneand (3) 4.2 � 1012 L (65% of total) during the remaining 90 dof the water year (USGS, 1971–2001). Using DOC data (Ta-bles 4 and 6), 33% of the annual load of DOC ([0.17][480�mol/L]/[(0.17)(480 �mol/L) � (0.18)(196 �mol/L) � (0.65� 201 �mol/L)] � 100%) is transported to the coastal BeaufortSea in 12 d. Using the same approach, the fractions of theannual transport of dissolved metals carried by the Sagavanirk-tok River in 12 d were as follows: Ba (15%), Cu (38%), Fe(74%), Pb (50%) and Zn (40%).

Calculations for annual transport of elements with suspended

sediment are based on two time periods (1) peak flow and (2)off-peak flow in June plus the remainder of the summer, be-cause sediment transport is predominantly during peak flowand because differences in concentrations of elements in theparticulate form (on a dry weight basis) vary only slightlyamong time periods. During the 3 d of peak water flow in theKuparuk River in June 2001, TSS averaged 63 mg/L to yield asediment discharge of �19,000 t (90% of total). During theoff-peak period in June and the remainder of the summer, TSSvalues averaged 4 and �0.5 mg/L, respectively, resulting in anadditional total of 1900 t of sediment discharged (Tables 4 and6). Thus, �90% of the annual transport of particulate Pb occursduring peak flow in the Kuparuk River during 3 d ([0.90][15.7�g/g]/[(0.10)(14.4 �g/g) � (0.90)(15.7 �g/g)] � 100%). Usingthe same approach, �89% of the other particulate metals andPOC were transported to the coastal Beaufort Sea by theKuparuk River in 3 d.

For the Sagavanirktok River, TSS averaged 267 mg/L duringpeak discharge in June to yield 267,000 t of sediment (88% oftotal) during the 12-d peak period. Concentrations of TSSaverage 31 and 1.3 mg/L during the off-peak period in June andthe remainder of the summer, respectively, transporting anadditional 36,000 t of sediment to the coastal Beaufort Sea.Particulate metal concentrations in the Sagavanirktok River donot vary greatly during peak and off-peak periods (Table 7) andtherefore, �88% of particulate Pb, the other metals and POCwere transported during the 12 d of peak discharge ([0.88][18.3�g/g]/[(0.12)(18.3 �g/g) � (0.88)(18.3 �g/g] � 100%).

Results from this study also provide a direct comparison ofthe relative abundances of dissolved and particulate forms ofmetals and organic carbon in the arctic rivers of Alaska (Tables4 and 7). During the brief periods of peak flow, the dissolvedfraction accounts for 57% (480 �mol/L/[480 �mol/L �(16,000 �g/g/12 �g/�mol � 0.267 g/L) � 100%]) and 83% ofDOC transport in the Sagavanirktok and Kuparuk rivers, re-spectively (Table 9). When combined with the off-peak data,the results indicate that DOC is the dominant form of OCdischarged to the coastal Beaufort Sea from these Alaskanarctic rivers. Dissolved Ba accounts for �14% of total Batransport during peak flow and at least 59% of Ba transportduring off-peak flow in June (Table 9). In the Sagavanirktok

Table 7. Concentrations of particulate trace metals and particulate organic carbon (POC) in the Sagavanirktok, Kuparuk and Colville Rivers duringJune 2001. Peak and off-peak concentrations are presented for the Kuparuk River due to distinct differences in the concentrations of some trace metalsduring those periods.

RiverAl(%)

Ba(�g/g)

Cu(�g/g)

Fe(%)

Pb(�g/g)

Zn(�g/g)

POC(%)

Sagavanirktok (n � 17) Mean 5.8 729 32.9 3.4 18.3 124 1.60SD 0.8 105 2.9 0.3 2.1 8 0.49Range 4.0–7.7 542–1008 29.7–39.2 2.6–4.0 16.0–23.4 115–135 0.7–2.7

Kuparuk Peakdischarge (n � 3)

Mean 5.2 615 32.3 3.6 15.7 124 4.6SD 0.5 88 5.8 0.2 0.7 13 1.1Range 4.6–5.8 497–743 25.7–37.2 3.3–3.8 14.7–16.6 110–145 3.3–5.9

Kuparuk Off-peakdischarge (n � 6)

Mean 3.5 469 29.9 3.7 14.4 92.1 4.9SD 0.5 70 1.3 0.3 8.3 21 2.0Range 2.7–4.0 397–559 28.6–31.2 3.1–4.2 4.0–22.5 69–116 2.8–7.6

Colville (n � 5) Mean 8.3 989 40.8 5.0 24.0 130 2.24SD 0.3 125 2.3 0.3 6.8 11 0.56Range 8.0–8.9 890–1190 36.9–42.6 4.7–5.3 19.8–36.0 116–147 1.7–3.3


River, �3% of the total Fe, Pb and Zn are in the dissolvedphase during both peak and off-peak periods, whereas dis-solved Cu is �9% of the total Cu, most likely due to compl-exation by DOC (Cabaniss and Shuman, 1998).

5. CONCLUSIONS

The 3- and 12-d spring flooding events in the Kuparuk andSagavanirktok rivers during June 2001 account for �25 and

�17%, respectively, of the annual discharge of water (USGS,1971–2001). High-resolution sampling of the SagavanirktokRiver during peak flow revealed that concentrations of dis-solved Cu, Fe, Pb, Zn and organic carbon increased by three-fold to twenty-fivefold at maximum discharge. Strong positivecorrelations for concentrations of dissolved metals vs. DOCsuggest that soil interstitial water and surface water that areflushed from the drainage basins are primary sources of metalsand DOC. During off-peak discharge in August, when flow andlevels of TSS decrease, concentrations of dissolved metals inthe Sagavanirktok and Kuparuk rivers are among the lowestvalues reported for world rivers.

Trends for concentrations of dissolved trace metals andorganic carbon in the Kuparuk and Colville rivers are similar tothose observed in the Sagavanirktok River. However, concen-trations of dissolved metals and DOC are, on average, higherthan those observed in the Sagavanirktok River during June2001. These higher concentrations in the Kuparuk and Colvillerivers appear to be related to differences in lithology andvegetation in the drainage basins. Soils westward of the car-bonate rich Sagavanirktok River are more acidic. These lowerpH soils are likely to support enhanced chemical weatheringand increased concentrations of dissolved metals and DOC.

In contrast with Cu, Fe, Pb and Zn, concentrations of dis-solved Ba remained relatively constant in each river throughoutthe sampling period with the Sagavanirktok River at 234 14nmol/L, the Kuparuk River at 171 16 nmol/L and theColville River at 376 24 nmol/L. These results suggest thatconcentrations of dissolved Ba are not significantly influencedby increases in water discharge or concentrations of TSS andDOC. Concentrations of dissolved Ba vary in proportion toconcentrations of total particulate Ba on a dry weight basis forthe Sagavanirktok, Kuparuk and Colville rivers and suggestthat dissolved Ba concentrations may be controlled by concen-trations of particulate Ba. Separate analyses with additionalsamples are needed to determine what fraction of the particu-late Ba is exchangeable. If this fraction proves to be propor-tional to concentrations of total particulate Ba, then dissolvedBa levels may be controlled by ion exchange with suspendedclay minerals.

Concentrations of particulate Cu, Fe, Pb, Zn and OC do notfollow the trends observed for the dissolved fraction and main-tain relatively constant concentrations (on a dry weight basis)throughout the spring floods. In addition, concentrations ofparticulate metals correlate well with particulate Al but arepoorly correlated with POC showing that clays rather thanorganic matter control particulate metal concentrations.

Increases in water discharge during the spring flood events

Table 8. Correlations for particulate trace metals and particulateorganic carbon (POC) in the Sagavanirktok River during June 2001.

Al Ba Cu Fe Pb Zn

Al 1Ba 0.88** 1Cu 0.81** 0.83** 1Fe 0.97** 0.86** 0.85** 1Pb 0.82** 0.92** 0.87** 0.83** 1Zn 0.77** 0.63** 0.51* 0.64** 0.59 1POC –0.35 –0.18 –0.25 –0.25 –0.28 –0.29

** Correlation is significant at the 0.01 level.* Correlation is significant at the 0.05 level.

Fig. 6. Concentrations of particulate Al vs. (a) Ba and (b) Fe for theSagavanirktok River (●), Kuparuk River during peak discharge (Œ),Kuparuk River during off-peak discharge in June (‚) and ColvilleRiver (�) during June 2001. The solid lines are from least-squaresregressions of the data. Dashed lines show 95% prediction intervals.Data points for off-peak discharge in the Kuparuk River are notincluded in the linear regression calculations for the Al vs. Fe plot.

Table 9. Percentage of trace metals and organic carbon in thedissolved phase during peak and off-peak discharge in the Sagavanirk-tok and Kuparuk rivers.

Ba Cu Fe Pb Zn OC

Sagavanirktok RiverDissolved (%) Peak 14 9 0.5 0.6 0.7 57Dissolved (%) Off-peak 59 29 0.6 2 3 83Kuparuk RiverDissolved (%) Peak 33 28 9 5 4.6 83Dissolved (%) Off-peak 93 87 30 41 44 98


coincide with increased concentrations of TSS, dissolved met-als, and OC and account for a large fraction of the annualtransport. In the Kuparuk and Sagavanirktok rivers, �16% ofthe water flow and �80% of the annual sediment dischargeoccurs during 3- and 12-d periods, respectively. These largepulses of water carry more than one-third of the annual dis-solved load of Cu, Fe, Pb, Zn and OC and �80% of theparticulate metals to the coastal Beaufort Sea.

Acknowledgments—We thank Bob Trocine and Michelle McElvainefrom Florida Institute of Technology, Mark Savoie and Gary Lawley ofKinnetics Laboratories, Anchorage, and John Brown of Battelle fortheir efforts in logistical support, sample collection and preparation.Our thanks to BP/ARCO for providing lab space, lodging and logisticsthroughout the project. We also thank Phillips Petroleum for providinghelicopter support to sample the Colville River. We especially thankDick Prentki of MMS, Anchorage, for numerous discussions and inputto the research. This study was supported by Minerals ManagementService (Contract No. 143501-99-CT-30998). Finally, we thank twoanonymous reviewers and the associate editor for their helpful andthoughtful comments.

Associate editor: K. F. Falkner

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increased concentrations of dissolved trace metals and organic carbon during snowmelt in rivers of...

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