Cd, Cr, Cu, Ni and Pb in the water column and sediments of the Ob-Irtysh Rivers, Russia

Manta, Pollution Bulletin, Vol. 35, Nos 7 12, pp. 270-279, 1997

Pergamon PII: S0025-326X(97)00087-8

~ 1997 Elsevier Science Ltd. All rights reserved Printed in Great Britain 0025-326X/97 $17J~)+ 0.00

Cd, Cr, Cu, Ni and Pb in the Water Column and Sediments of the Ob-Irtysh Rivers, Russia S. BRADLEY MORAN* and WENDY L. WOODS Graduate School of Oceanography, University of Rhode Island, Narragansett, Rhode Island 02882-1197, USA

Concentrations of Cd, Cr, Cu, Ni and Pb were determined in filtered water, suspended particulate matter, and bottom sediments from a .-.2000 km section of the Ob and Irtysh Rivers. Dissolved Cd, Cr, Cu and Ni concentrations are similar to, or higher than, results from other Russian Arctic and large world river-estuaries. Concentrations of Cd, Cr, Cu, Ni and Pb in suspended particulate matter are generally comparable to results from other Russian Arctic and large world rivers and estuaries. Comparison of trace metal ratios in crustal material and suspended particulate matter and bottom sediment suggests that the source of Cr, Cu and Ni is continental weathering. Particulate Cd and Pb are elevated relative to their crustal abundance, suggesting a source of these metals to the Ob-Irtysh in addition to continental weathering. © 1997 Elsevier Science Ltd. All rights reserved

Kara Sea. Results from Martin et al. (1993) and Dai and Martin (1995) indicate that the concentration of heavy metal contaminants in the Lena, Ob and Yenisey River-estuaries are generally low and comparable to other unpolluted world rivers. This study provides an assessment of the concentrations of several heavy metal contaminants (Cd, Cr, Cu, Ni, Pb) in the water column and bottom sediments of the interior Ob-Irtysh Rivers. Sampling was conducted in 1994 and 1995 and extended from the Ob Gulf, upstream from the estuary, to the Irtysh and Tobal Rivers (Fig. 1). Results reported here provide an improved understanding of the geochemistry of heavy metals in the Ob and Irtysh Rivers and extend the limited riverine data on trace metals in the Russian Arctic.

Keywords: trace metals; particles; contaminants; rivers; Russia.

M e t h o d s and M a t e r i a l s

Several recent studies of large rivers and estuaries in Russia have been conducted to investigate their natural geochemistry and to assess contaminant concentrations in these aquatic systems. For example, studies conducted by Russian investigators (Brekhovskikh et al., 1990; Gordeev and Sidorov, 1993; Gurvich et al., 1994; Lisitzin et al., 1994) have provided data on major element, trace metal, nutrient and suspended particle concentrations from several Russian rivers and the Kara and Laptev Seas. With respect to trace metals, reliable data obtained using established clean techniques have only recently been reported for Russian Arctic rivers. In particular, Martin et al. (1993) reported high quality data for a suite of trace metals (As, Cd, Cu, Fe, Ni, Pb and Zn) in the Lena River Estuary and adjacent Laptev Sea. Dai and Martin (1995) reported concentrations of trace metals (Cd, Cu, Fe, Ni, Pb) in the northern section of the Ob-Yenisey River-estuaries and

¶ C o r r e s p o n d i n g a u t h o r : Tel: (401) 8 7 4 - 6 5 3 0 ; fax: (401) 8 7 4 - 6 8 1 1 ; email: m o r a n @ g s o s u n l . g s o . u r i . e d u

270

Study site The Ob-Irtysh River is the longest of the Russian rivers (5410 km) and has the largest drainage basin, estimated at 3x106 km 2 (Telang et al., 1991), which includes regions of western Siberia, the Central and North Kazakhstan Plains, and the Ural and Altay mountains. The Ob is the third largest Russian river with respect to flow rate (after the Yenisey and Lena Rivers) and has a mean discharge into the Kara Sea of 1.4x104 m 3 s -L (Dai and Martin, 1995). The permanent freshwater regime extends to 69°N, even during periods of low discharge. The annual discharge cycle is typical of northern rivers, with peak discharge in June, decreasing into the fall, and low discharge occurring during the winter (Ivanov, 1980). Sample collection The Russian Fisheries Protection vessel RS300#168 based in Salekhard was used to collect water column and bottom sediment samples from the Ob River at 12 stations in July-August 1994, and at 8 stations in June 1995, which included the Irtysh and Tobal Rivers (Fig. 1). Sampling was conducted in collaboration with WHOI sediment coring, and station numbers reported

Volume 35/Numbers 7-12/July-December 1997

Ob Estuary

Sample sites Nuclear facilities ,

,•r1994 X

/

Circle

1995 Sample sites

6 10

Fig. 1 Map showing stations occupiedin 1994and 1995in the Ob and Irtysh Rivers. Station 13 is located at the northern end of the Taz River.

here correspond to W H O I station numbers. All stations were located in freshwater. Station 14 is the approximate location of the most southern station (4418) occupied by Dai and Martin (1995). All other stations reported by Dai and Martin (1995) were north of this location, in the Ob Estuary and the Kara Sea. For the 1994 expedition, filtered water samples for trace metal determination were collected using a shipboard electric Flotec diaphragm pump to pump surface water through acid-cleaned Bev-a-line tubing connected to an acid-cleaned 0.2 ~tm Gelman minicapsule filter. Materials in contact with the samples included PVC, silicon, teflon and polyethylene. A new filter was used at each station and thoroughly rinsed with several litres of sample prior to collection of the filtrate. Filtered water samples (,,~100 ml) were collected in pre-cleaned 125 ml polyethylene bottles and acidified to p H 2 using concentrated Seastar HC1 within a few

hours of collection. Sample bottles were stored in ziplok bags. Sample manipulations in the field were conducted in a laminar flow clean bench using clean techniques to minimize sources of contamination. For the 1995 expedition, unfiltered river water was collected by hand in a clean 1-1 polyethylene bottle from the front of a rubber raft while slowly moving forward. The sample was returned to the shipboard lab for further processing. The sample was filtered under mild vacuum (5-10 psi) through an acid-cleaned 0.2 ~tm, 47 mm, Nuclepore filter held in an acid-cleaned polysulphone filter holder. The filtered sample (,-,100 ml) was stored acidified in a 250-ml clean bottle using the same clean procedures described above. Samples for determination of suspended particulate trace metals were collected in 1994 by filtering 125 ml of river water through pre-cleaned, preweighed, 0.2 lam, 47 mm, Nuclepore filters held in a Teflon in-line filter 271

Marine Pollution Bulletin

holder connected to Bev-a-line tubing. After each sample was collected, the in-line Teflon filter holder was rinsed with 0.1 M Seastar HCI and Milli-Q water and stored in a zip-lok bag. Particulate trace metal samples were held in plastic petri dishes and stored in zip-lok bags. For the 1995 expedition, particulate matter filtered from ~I00 ml of river water using the polysulphone filter holder was stored as described above. Bottom sediments were collected only in 1994 at 11 stations using a small box corer. Approximately 10 g of the upper 1-2 cm of bottom sediment was subsampled from the box core into plastic vials and stored in zip-lok bags. Samples for determination of suspended particulate matter (SPM) concentration were collected by filtering 100 ml of river water through preweighed 0.4 lam, 47 mm, Nuclepore filters held in a glass filter holder. Particulate organic carbon (POC) samples were collected by filtering ~100 ml through precombusted 25 mm GF/F (0.7 gm) filters held in a plastic filter holder. SPM and POC samples were held in plastic petri dishes and stored in zip-lok bags. POC samples were stored in a refrigerator. All samples were hand-carried back to the US for subsequent analysis.

Dissolved and particulate trace metal analyses Determination of dissolved Cd, Cu, Ni and Pb concentrations in filtered water samples (~50-100 ml) was conducted in a HEPA filtered clean room using the Co-APDC preconcentration method (Boyle and Edmond, 1975) modified by Bender and Gagner (1976). Preconcentrated trace metals of interest were

quantified using a Perkin Elmer 4100ZL GFAAS equipped with Zeeman background correction. Dissolved Cr concentrations in filtered river water were determined by direct injection-GFAAS. Recoveries were determined to be 95-100% based on analysis of NRC CASS-2 and NASS-4 standard reference seawater. The precision of replicate analysis of filtered water samples averaged 5%. Dissolved metal blanks were processed by filtering Milli-Q water through the sampling system while on board ship. Dissolved metal blanks were 0.027 lag 1- l for Cr, 0.015 lag 1-1 for Cu, and 0.075 lag 1-t for Ni, which represents ~5-10% of the average Ob-Irtysh river water concentration of these metals. The dissolved Cd blank was 0.0008 lag 1~18% of the average dissolved Cd concentration. The dissolved Pb blank was unacceptably high, ~0.01 lag 1-1. We suspect our filtered samples were contaminated for Pb and these results are not reported. Suspended particulate samples collected using Nuclepore filters and containing ~2-20 mg of dry material were leached in acid-cleaned polyethylene vials in 5 ml of 2 M Seastar HNO3 for six weeks. Samples of bottom sediment (~10 g) were dried and mixed to ensure a homogeneous sample. Approximately 100 mg of dry sediment were added to acid-cleaned polyethylene sample vials. Sediment samples were acidified with 5 ml of 2 M Seastar HNO3 and allowed to leach for six weeks prior to analysis. Samples were then filtered through precleaned 0.4 lam Nuclepore filters to remove suspended solids. Concentrations of Cd, Cr, Cu, Ni and Pb in leachates of the suspended particulate and bottom sediment samples were quantified using a Perkin Elmer A4000 GFAAS. Recoveries using this protocol were 80-

TABLE 1 Ob and Irtysh River station locations and ancillary data.

Station

Date (M/D/Y)

Latitude, longitude

Water depth (m)

Sampling depth (m)

SPM (mg 1--1)

POC (p.mol 1-1)

1994 Expedition Ob94-1 Ob94-2 Ob94-3 Ob94-4 Ob94-5 Ob94-6 Ob94-8 Ob94-10 Ob94-11 Ob94-13 Ob94-14 Ob94-16

7/19/94 7/20/94 7/21/94 7/22/94 7/23/94 7/24/94 7/26/94 7/28/94 7/29/94 7/31/94 8/1/94 8/2/94

64 °56.62'N, 65 ° 15.64'N 65°28.86'N 65°47.38'N 66 ° 17.38'N 66°38.35'N 66°48.50'N 66°47.3 I'N 67°40.92'N 69°05.63'N 68°25.54'N 66 °51.54'N

65°40.24'E 65°40.59'E 65°40.66'E 65°52.05'E 66 ° 12.05'E 67 ° 18.47'E 69°26.27'E 70°49.50'E 72°56.87'E 76°43.12'E 73°49.88'E 73°11.90'E

7 6 6 6 6 4 7 5 7 10 10 6

3 3 3 3 3 2 2 2 3 3 3 3

32.2 52.9 38.7 76.5 64.7 58.7 35.4 174 31.7 33.1 13.6 65.1

119 153 95 127 141 139 82 234 124 77 79 173

6/11/95 6/13•95 6/13/95 6/14/95 6/16/95 6/18/95 6/19/95 6/21/95

62°26.70'N, 61 oI 1.27'N, 61°11.49'N, 60 ° 56.63'N, 59°34.17'N, 58°30.62'N, 58°05.74'N, 57°59.63'N,

66°01.86'E 68°55.49'E 69°04.4YE 69°12.76'E 69°19.03'E 68°27.51'E 69°09.21'E 68°48.28'E

5 5 7 10 10 5 9 8

2 2 2 2 2 2 2 2

43.2 50.9 36.0 61.9 64.3 47.2 52.1 59.1

269 105 84 134 77 99 139 83

1995 Expedition Ob95-2 Ob95-4 Ob95-5 Ob96-6 Ob95-7 Ob95-9 Ob95-10 Ob95-12

272

Volume 35/Numbers 7-12/July-December

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Marine Pollution Bulletin

90% for the trace metals of interest based on analysis of N R C MESS-2 standard reference sediment. Replicate analysis of particulate samples indicated an average precision of 5%. Nuclepore filter blanks for Cd, Cr, Cu, Ni and Pb were not detectable.

filtered (<0.2 tam) river water are referred to as dissolved, although this operational definition includes metals associated with submicron colloids. One general observation to note is the remarkably similar dissolved metal concentrations determined in separate years. In particular, station 1 occupied in 1994 and station 2 occupied in 1995 (~300km apart) have similar dissolved Cd, Cu and Ni concentrations; only dissolved Cr concentrations are markedly different between these stations (Fig. 2). Dissolved Cd concentrations range from 0.1015.10 ng 1-I and average 3.7 ng 1-1 (Fig. 2). Dissolved Cd concentrations are essentially invariant throughout the river, with the lowest value (0.10 ng 1-l) determined at station 16 in the Ob Gulf. The highest concentration of dissolved Cd (15.10ng1-1) was determined at station 9, which is located ~50 km downstream from the industrialized city of Tobolsk. Dai and Martin (1995) reported very low dissolved Cd concentrations (0.61~).84 ng 1- t ) in the freshwater end-member and Estuary of the Ob, similar to values determined in the Anadyr Estuary (Alexander and Windom, unpublished data) (Table 3). Concentrations of dissolved Cd determined in 1994 at station 11 (0.7ng1-1) and station 16 (0.10 ng 1-1) are similar to values reported

Ancillary measurements

Suspended particulate matter concentrations were determined gravimetrically. Samples for POC determination were exposed to fuming HCI to remove inorganic carbon and the remaining organic carbon was quantified using a C H N analyser.

Results and Discussion Station locations, sampling depths, and SPM and POC concentrations are listed in Tables 1 and 2. The concentration of suspended particulate matter ranged from 14-174 mg 1-1 and averaged 55 mg 1-1. Concentrations of POC ranged from 77-269 pmol 1-1, with an average concentration of 127 pmol 1-1. Trace metals in filtered river water

Dissolved concentrations of Cd, Cr, Cu and Ni are presented in Fig. 2. Note that metal concentrations in

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Fig. 3 Concentrations of suspended particulate matter (SPM), particulate organic carbon (POC), and Ni, Cu, Cr, Pb and Cd in suspended particulate matter (filled bars) and bottom sediments (open bars). Stations are plotted from the most southern (1995 station 12) to northern (1994 station 13) stations occupied.

by Dai and Martin (1995) for this region of the Ob, however, results from stations 13 and 14 (2.5 ng l - l ) are considerably higher. Dissolved Cd concentrations in the interior Ob-Irtysh Rivers are comparable to the Yenisey and Lena Rivers and estuaries and to several other world rivers (Table 3), such as the Mississippi (Shiller and Boyle, 1987), Yangtze (Edmond et al., 1985), Amazon (Boyle et al., 1982), Orinoco (Edmond et al., 1985), Yellow (Zhang et al., 1994) and several US East Coast rivers (Windom, 1990). 276

Dissolved Cu concentrations exhibit remarkably little variation throughout the Ob-Irtysh, with values ranging from 1.83-4.81 I-tg 1-1 and averaging 2.82 p.g 1-1. The highest dissolved Cu concentration (4.81 ~tg l - t ) is in the Irtysh River at station 12. Overall, dissolved Cu concentrations in the Ob-Irtysh are comparable to concentrations in the Ob and Yenisey River and Estuary (Dai and Martin, 1995) and higher than values in the Anadyr (Alexander and Windom, unpublished data) and Lena Rivers (Martin et al.,

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1993). In addition, dissolved Cu concentrations in the Ob-Irtysh are slightly higher than values listed in Table 3 for several major world rivers. Dissolved Cr concentrations increase slightly from south to north in the Ob-Irtysh, with values ranging from 0.06-0.34 lag1-1 and averaging 0.23 lag1-1. Dissolved Cr data have not been reported for Arctic rivers. With respect to other large world rivers (Table 3), dissolved Cr concentrations in the Ob-Irtysh are slightly higher than in the Mississippi (Shiller and Boyle, 1987), Amazon (Boyle et al., 1982), Orinoco and Yangtze (Edmond et al., 1985), and slightly lower than in the St Lawrence River (Campbell and Yeats, 1984). Concentrations of dissolved Ni range from 0.802.80 lag 1- l and average 1.94 lag 1- l . Dissolved Ni concentrations in the Ob-Irtysh bracket the range of values reported for the Ob River-estuary (Dai and Martin, 1995) and are higher on average than results presented in Table 3 for the Yenisey (Dai and Martin, 1995), Lena (Martin et al., 1993) and Anadyr River-

estuaries (Alexander and Windom, unpublished data). Dissolved Ni concentrations are higher than other major world rivers (Table 3), with the exception of the Mississippi River (Shiller and Boyle, 1987) which has comparable dissolved Ni concentrations. Trace metals & suspended particulate matter and bottom sediments Figure 3 presents concentrations of SPM, POC, and Cd, Cr, Cu, Ni and Pb in suspended particulate matter and bottom sediments. No obvious trends in suspended particulate metal concentrations are evident in the ObIrtysh. Concentrations of metals in suspended particulate matter range from 0.17-1. 26 lag g -1 for Cd (average = 0.58 lag g - 1), 9.5-89.2 lag g - l for Cr (average=49.8 lag g - l ) , 3.7-50.5 lag g-1 for Cu (average =25.8 lag g - l ) , 7.7-52.5 lag g - l for Ni (average= 28.8 lag g - l ) and 1.1-27.5 lag g - l for Pb (average = 14.9 lag g - [). Concentrations of suspended particulate trace metals are generally similar to, or lower than,

277

Marine Pollution Bulletin the range o f concentrations listed in Table 3 for other Russian Arctic and large world rivers and estuaries. As observed for the suspended particulate trace metal results, no systematic variations are apparent in the concentration o f trace metals in b o t t o m sediments along the Ob (Fig. 3). Metal concentrations in the sediments range f r o m 0.047-0.16 gg g - l for Cd (average =0.11 gg g - l ) , 2.8-23.4 gg g-X for Cr (average = 14.3 ~tg g - l ) , 1.1-15.3 gg g - 1 for Cu (average=8. 8 ggg-l), 3.2-24.4 lxgg -1 for Ni (average = 14.8 gg g - l ) and 1.4-10.2 gg g - i for Pb (averag e = 6 . 0 g g g - 1 ) . C o n c e n t r a t i o n s o f metals in the b o t t o m sediments are generally similar to, or lower than, concentrations in the suspended particles (Fig. 3). Ratios o f Cd, Cr, C u and Pb to Ni in suspended particulate matter a n d b o t t o m sediments are presented in Fig. 4. Also plotted are the crustal ratios for these trace metals. In particular, the Cr/Ni and C u / N i results f r o m 1994 exhibit a linear relationship that is close to their respective crustal ratios, whereas the majority o f the C r / N i and C u f N i d a t a f r o m 1995 lie above their respective crustal ratios. These results suggest that the source o f particulate Cr, Cu and Ni is continental weathering and that there m a y be an additional source o f Cr and C u in the interior O b - I r t y s h . With respect to Cd and Pb, d a t a f r o m 1994 and 1995 indicate elevated C d / N i and P b f N i ratios relative to their respective crustal ratios t h r o u g h o u t the O b - I r t y s h River (Fig. 4). Interestingly, the P b / N i ratio o f b o t h the suspended particles and b o t t o m sediments exhibits an approximately linear relationship a b o v e the crustal ratio. The elevated C d / N i and P b / N i ratios are consistent with a source o f Cd and Pb to the O b - I r t y s h in addition to continental weathering, a l t h o u g h the nature o f the source (e.g. industrial effluent, atmospheric deposition) c a n n o t be determined f r o m these data.

Summary Results f r o m this study and other recent work (Dai and Martin, 1995) indicate that concentrations o f dissolved Cd, C u a n d Ni in the O b - I r t y s h Rivers are similar to, or higher than, results f r o m other Russian Arctic rivers, n o t a b l y the Yenisey (Dai and Martin, 1995), Lena (Martin et al., 1993) and A n a d y r Rivers (Alexander and W i n d o m , unpublished data). Furthermore, concentrations o f dissolved Cd, Cr, Cu and Hi are also generally similar to, or slightly higher than, other large world river-estuaries. Concentrations o f Cd, Cr, Cu, Ni and Pb in suspended particulate matter from the O b - I r t y s h Rivers are similar to, or lower than, results f r o m other Russian Arctic and large world rivers and estuaries. C o m p a r i s o n o f trace metal ratios in crustal material a n d in suspended particulate matter and b o t t o m sediment f r o m the O b - I r t y s h Rivers suggests that the source o f Cr, C u and Hi is f r o m continental weathering. A n additional source o f Cd and 278

Pb to the O b - I r t y s h is suggested f r o m the particulate metal ratios and m a y reflect a n t h r o p o g e n i c input.

We thank Nikolai Laverov, vice-president of the Russian Academy of Sciences, for promoting these expeditions; Valeriy Shishmarev of the Environment Protection Committee in Salekhard for providing a research vessel; the Captain and crew of the Russian Fisheries Protection vessel RS300#168; Russian scientists Olga Medkova, Alexei Miroshnikov, Nikolai Tarasov and Alexander Shmelerv for logistics; Chris Reddy for cruise preparation; Steve Pike for POC analyses; Doug Cullen for trace metal analyses, and, Hugh Livingston, Fred Sayles and the late George Panteleyev for organizing the expeditions. This work was supported by the Office of Naval Research Arctic Nuclear Waste Assessment Program (Contract No. N000149410939).

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