Geochemistry of thirteen Voronin Trough cores,Kara Sea,European Arctic: Hg and As contaminants at a 1965 timeline

The potentially toxic elements Hg and As are found at high concentrations in surface/near-surface sediments from Arctic ocean cores collected from the Voronin Trough, Kara Sea, during 1965. The levels reach 2045 ppb for Hg and 270 ppm for As. Manganese high values (up to 1.27%) are also found in the cores’ surface/near-surface sections. Other heavy metals tracked by the Arctic Monitoring and Assessment Program (e.g., Cu, Ni, Pb, Sb, Ti, Zn) have baseline concentrations in the cores. The cores average >57% clay-size and >35% silt-size in their textural composition. The elevated contents may result from anthropogenic input for Hg and As with diagenesis adding to the As concentration. Possible sources for these elements are emissions and effluents from industry such as mining and smelting operations, and burning of fossil fuels in Siberia and the Urals. When discharged into the Kara Sea from Siberian catchments, the As and Hg likely attach to charged particulate surfaces of Fe oxy/hydroxides (for As) and particulate organic matter or clay minerals (for Hg). These are transported, entrained in ocean currents or adhered to pack ice, to the Voronin Trough where they deposit according to size and specific gravity.     

Variability of fluvial sediment supply to the Laptev Sea continental margin during Late Weichselian to Holocene times: implications from clay–mineral records

Three sediment cores from the Laptev Sea continental margin were investigated for their clay mineralogy by X-ray diffraction to study the fluvial sediment supply since the late Weichselian. In the study area, the clay-mineral composition of surface sediments is characterized by distinct regional variations. The source area for smectite in the eastern Eurasian Basin is the Putoran Plateau drained by the Khatanga and Yenisei rivers. Currents caused by river discharge and the inflow of Atlantic water masses along the Eurasian continental margin are responsible for sediment distribution. In the sediment cores, smectite and illite contents show an opposite trend which mainly results from variable smectite supply. During MIS 2 the amount of smectite on the Laptev Sea continental margin never exceeds 10 rel.%. Probably, reduced river discharge and the lowered sea level during MIS 2 caused a decreased sediment supply to the Laptev Sea. Additionally, the Putoran Plateau was covered by an ice sheet during the Late Weichselian preventing the erosion of smectite-rich soils. In contrast, maximum smectite contents (up to 30 rel.%) in Holocene sediments result from increased sediment input by the Khatanga River and from the Kara Sea through the Vilkitsky Strait and via St. Anna Trough into the western Laptev Sea.     

The Svalbard western coast: site of baseline geochemistry and incipient contamination

 Potentially toxic metals tracked by the Arctic Monitoring and Assessment Program were analysed in sediments from the Svalbard western coastal zone. These include As and Hg found as contaminants in other Arctic seas as well as other elements (e.g. Pb, V, Cu, Zn, Cr, Ni). Svalbard shelf sediments contain average values of 12 ppm As, 12 ppm Pb, 56 ppb Hg and 114 ppm V. These values increase in Isfjorden sediments to 15 ppm As, 28 ppm Pb, 99 ppb Hg and 210 ppm V. Cluster analysis yields a major cluster that is likely related to clay minerals (Al, K, Ti, Mg) and sorption onto them of transition (Cu, V, Cr, Sc) and other elements (Pb, Rb). A second significant cluster includes Ca, Sr and plagioclase. The Svalbard western shelf is a natural geochemical environment. The possible incipient contamination of fjord sediments by As, Pb, Hg and V should be evaluated for possible links to anthropogenic sources. If links are found, remediation must be used to stop the input and preserve a pristine Svalbard fjord environment. Received: 21 December 1998 · Accepted: 15 March 1999     

The impact of glaciation, river-discharge and sea-level change on Late Quaternary environments in the southwestern Kara Sea

Sedimentary records from the southwestern Kara Sea were investigated to better understand the extent of the last glaciation on the Eurasian Arctic shelf, sea-level change, and history of the Ob' and Yenisey river discharge. Sediment-core and seismic-reflection data indicate that the Quaternary depositional sequence in the southwestern Kara Sea consists of glacial, glaciomarine, and marine sedimentary units. Glaciogenic sediments in the deep Novaya Zemlya Trough are presumably related to the Last Glacial Maximum (LGM), whereas further east they may represent an earlier glaciation. Thus, it is inferred that the southeastern margin of the LGM Barents-Kara ice sheet was contained in the southwestern Kara Sea east of the Novaya Zemlya Trough. Changes in mineralogical, foraminiferal, and stable-isotopic composition of sediment cores indicate that riverine discharge strongly influenced sedimentary and biotic environments in the study area during the Late Weichselian and early Holocene until ca. 9 ka, consistent with lowered sea levels. Subsequent proxy records reflect minor changes in the Holocene hydrographic regime, generally characterized by reduced riverine inputs.     

Light Fraction Mineralogy of Upper Quaternary Sediments from the Saint Anna Trough and Its Paleoceanographic Interpretation

Distribution patterns of light minerals, including quartz grains with variable roundness degree, is described in three reference cores from the Saint Anna Trough, Kara Sea. The light fraction mineralogy, coupled with our results on grain size distribution and published data on heavy fraction mineralogy, clay mineralogy, foraminiferal assemblages, oxygen isotopy, organic matter, and radiocarbon dating, allows us to reconstruct the Late Quaternary sedimentary history. Three (glacial, glaciomarine, and marine) development stages are distinguished.     

Native arsenic – realgar mineralization in marbles from Saualpe, Carinthia, Austria

Summary The “Geochemical Atlas of Austria” shows a notable positive geochemical arsenic anomaly in stream sediments of the Saualpe, eastern Carinthia, Austria. Detailed investigation has shown that it is caused by an unusual kind of mineralization in brecciated marbles. The mineralization consists predominantly of native arsenic (often in small, stellate aggregates) and realgar (± minor orpiment). The As content may reach as much as 1.4 wt-%. The samples investigated do not contain any sulfarsenides and arsenides, and do not show enrichments of other metals: e.g. gold contents are < 5 ppb, Hg contents ≤ 1.3 ppm, Sb contents ≤ 4 ppm. The atomic As/S ratio varies considerably, and surpasses in a number of samples a value of 2. The As mineralization seems to be associated with the formation of late, extremely fine-grained quartz ± carbonate, penetrating the breccia, and is evidently a very late event in the mineralization history of the region.

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Zusammenfassung Eine gediegen Arsen – Realgar Vererzung in Marmorender Saualpe, K?rnten, ?sterreich Der “Geochemische Atlas der Republik ?sterreich” zeigt in Bachsedimenten der Saualpe, ?stliches K?rnten, ?sterreich, eine bemerkenswerte positive geochemische Arsenanomlie. Die detaillierte Untersuchung zeigte, da? sie haupts?chlich durch eine ungew?hnliche Mineralisation in Marmorbrekzien verursacht ist. Diese besteht fast ausschlie?lich aus gediegen Arsen (oft in kleinen, sternf?rmigen Aggregaten) und Realgar (± wenig Auripigment). Der As-Gehalt kann 1.4 Gew.-% erreichen. Die untersuchten Proben sind frei von Sulfarseniden und Arseniden, und sie zeigen keine nennenswerten Anreicherungen an anderen Metallen: z. B. sind die Goldgehalte < 5 ppb, die Hg-Gehalte ≤ 1.3 ppm und die Sb-Gehalte ≤ 4 ppm. Das atomare As/S-Verh?ltnis schwankt betr?chtlich und überschreitet in einer Reihe von Proben den Wert 2. Diese As-Mineralisation scheint mit der Bildung von sp?tem, feinstk?rnigem Quarz ± Karbonaten verbunden zu sein und ist in der Mineralisationsgeschichte der Region offensichtlich ein sehr sp?tes Ereignis.

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Received April 21, 1999; revised version accepted December 30, 1999     

The Svalbard–Kara plates junction: structure and geodynamic history

The structure and geodynamic history of the northern Barents–Kara continental margin, which had formed mostly by the latest Paleozoic, have been investigated using offshore geological and geophysical data and geological evidence from adjacent landmasses. In the context of the suggested model, the Saint Anna trough is interpreted as a boundary tectonic element between the Svalbard and Kara plates. Thus, the study focuses on a complex tectonic node with its structure having implications for the trough origin, as well as for the history of geodynamic relations among Arctic cratons and microplates. Trough structures of different ages in the area, including the northeastern East Barents trough and the St. Anna trough, appear to be a zone of triple or T-shaped junction. The reported reconstruction of the trough system history since the Middle Paleozoic shows that the St. Anna trough joined the East-Barents system in the Late Permian–Triassic to become its new segment extending the system to the north.     

The influence of atmospheric circulation on the dynamics of the intermediate water layer in the eastern part of the St. Anna Trough

This paper discusses the results of unique direct observations over the current velocities in the eastern part of the St. Anna deep-water trough, made in the period from August 2009 until September 2010, and analyzes the physical ways how the temporal variability of currents is formed. The stable northward barotropic transport with an average annual velocity of about 20 cm/s was discovered. It was found that changes in velocity with a characteristic timescale of several weeks occurred synchronously in the entire water column and were determined by the deformation of the sea level field due to long-period disturbances of the large-scale field of ground wind above the northern parts of Barents and Kara seas. For the winds of the southwest and west directions, the sea level??s gradient is formed across the St. Anna Trough and the northward meridional water transport is intensified owing to the geostrophic adjustment. These are verified by the results of numerical simulation.     

Platinum-group elements in ores from the Kalmakyr porphyry Cu–Au–Mo deposit, Uzbekistan: bulk geochemical and laser ablation ICP-MS data

We studied primary ore samples from Kalmakyr, a giant Cu–Au–Mo porphyry deposit in eastern Uzbekistan. Disseminated and stockwork-type high-grade Cu–Au–Mo mineralization showed average concentrations of 55 ppb Pd, 5.5 ppb Pt, 0.95 ppb Rh, 0.49 ppb Ir, and 4.1 ppm Au (n = 8). This type of mineralization is characterized by the presence of pyrite, chalcopyrite, molybdenite, and gold. A peak Pd content of 292 ppb was determined in a base-metal-rich quartz vein in granodiorite porphyry, which contains galena, sphalerite, chalcopyrite, tetrahedrite, and gold. Palladium correlates with Cu, Ag, Se, and S. Mineralogical and laser ablation ICP-MS study confirmed that Pd is homogeneously distributed in chalcopyrite, which contains up to 110 ppm Pd, and tetrahedrite, containing up to 20 ppm Pd. An assessment of the Pd and Pt budget at Kalmakyr showed the potential of approximately 17 t of Pd and 1.7 t of Pt.     

A contemporary contamination record of stormdrain and harbour sediments, Wellington, New Zealand

 Sediments from stormdrain catchments and outlets in Wellington city and sediment traps from Wellington Harbour were sampled for trace metal content. Samples were analysed for total metal content using XRF and ICP-MS. High values of Pb and Zn were found in stormdrain catchments and outlets, decreasing to elevated background rock levels in the harbour. Maximum values were recorded in an inner city stormdrain catchment, with levels of Pb (4605 ppm), Cu (2981 ppm) and Zn (3572 ppm) all higher than the biological probable effects levels (PEL). Concentrations of As, Cr, Cu, Pb, Ni and Zn concentrations in all harbour sediment trap samples were below the PEL. The mean values for each harbour sediment trap sample can be used as an accurate historical baseline in future studies. Stormdrain samples with high trace metal levels were close to industrial and construction sites. The proximity of these outlets to recreational areas should be of concern to local authorities. Received: 28 August 1997 · Accepted: 15 December 1997     

Unconventional PGE occurrences and PGE mineralization in the Great Dyke: metallogenic and economic aspects

Platinum group elements (PGE) are strategic materials because 96–99% of the world production is derived from just five mining districts and because they cannot be replaced as catalysts in many chemical processes. In order to lessen the strategic character of PGE, both conventional deposits and unconventional PGE mineralizations were investigated in an attempt to locate viable deposits which would diversify the supplier base. In the Great Dyke, conventional PGE mineralization occurs in the form of pristine sulfide ores mined underground and oxidic surface ores. New observations such as bimodal distributions of the PGE in the Main Sulfide Zone (MSZ), elevated Pt/Pd ratios in the oxidized MSZ compared to the sulfidic part and distinct differences between the platinum group mineral (PGM) assemblages of the MSZ and stream sediments of adjacent rivers emphasize the fact that even though the Great Dyke seems to be the second or third largest PGE occurrence in the world, the complicated PGE distributions and supergene redistributions should be kept in mind during planning and mine operation. Investigations of unconventional PGE occurrences in ophiolites, Alaskan-type intrusions, porphyry copper deposits and in the Kupferschiefer show that economically exploitable PGE concentrations can be expected in a broader variety of host rocks than considered favourable in the past. In the Albanian Mirdita ophiolite average contents of 860 ppb Pt and 60 ppb Pd were detected. Flotation concentrates of porphyry copper deposits, for example from Mamut, Malaysia, Santo Tomas, Philippines, Elacite, Bulgaria, and Ok Tedi, Papua New Guinea, contain between 827 and 1860 ppb Pd + Pt. In selected profiles of the Polish Kupferschiefer average contents of 255 ppb Pt, 94 ppb Pd, 2.4 ppm Au and 13.0 ppm Ag were analysed. The distribution of the PGE resources in the world and the annual production rates, however, underline the fact that the chances for a significant change in the supplier base are relatively low. The Bushveld Complex will remain the largest producer, followed by Noril'sk-Talnakh, Sudbury and Stillwater. If the operations in the Great Dyke reach their planned capacities, the Great Dyke will rank in third place among the PGE-producing deposits in the world. Received: 12 September 1998 / Accepted: 7 December 1999     

Arsenic content and groundwater geochemistry of the San Antonio-El Triunfo, Carrizal and Los Planes aquifers in southernmost Baja California, Mexico

 The San Antonio-El Triunfo mining district, located at a mountainous region 45 km south-east of La Paz, Baja California, has been worked since the late 1700s. Mine waste material produced during 200 years of mineral extraction area poses a risk of local groundwater pollution and eventually, regional pollution to the Carrizal (west basin) and the Los Planes (east basin) aquifers. There are different types of deposits in the mining area. These are dominated by epithermal veins, in which arsenopyrite is an important component. Carrillo and Drever (1998a) concluded that, even though the amount of mine waste is relatively small in comparison to the large scale area, significant As in groundwater derived from the mine waste piles is found locally in the groundwater. This paper shows the results of geochemical analyses of groundwater samples from the San Antonio-El Triunfo area and the Carrizal and Los Planes aquifers during several years of monitoring (1993–1997). The highest values of total dissolved solids (TDS) and As are in the mineralized area where the mining operations occurred (∼1500 ppm TDS and 0.41 ppm As). The lowest concentrations of TDS and As are, in general, away from the mineralized area (∼500 ppm TDS and 0.01 ppm As). Sulfate and bicarbonate (alkalinity) are, in general, high near the mineralized area and low away from it. The arsenic concentrations vary seasonally, especially after the heavy summer thunderstorms. Geochemical modeling (MINTEQA2 and NETPATH) and analysis of the regional geochemical evolution of the groundwater from the mining area towards the aquifer of Los Planes shows that the most likely hydrochemical processes include: dilution, precipitation of calcite, and adsorption of As onto surfaces of iron oxyhydroxides (ferrihydrite). These processes act as natural controls to the extent and amount of As pollution in the Carrizal and Los Planes aquifers. Received: 4 May 1999 · Accepted: 22 February 2000     

Thermosteresis and Transportation of Atlantic Water Along Eurasian Basin of the Arctic Ocean

It is summarized based on previous studies that warm and salty Atlantic Water (AW) brings huge amount of heat into Arctic Ocean and influences oceanic heat distribution and climate. Both heat transportation and heat release of AW are key factors affecting the thermal process in Eurasian Basin. The Arctic circumpolar boundary current is the carrier of AW, whose flow velocity varies to influence the efficiency of the warm advection. Because the depth of AW in Eurasian Basin is much shallower than that in Canadian Basin, the upward heat release of AW is an important heat source to supply sea ice melting. Turbulent mixing, winter convention and double-diffusion convention constitute the main physical mechanism for AW upward heat release, which results in the decrease of the Atlantic water core temperature during its spreading along the boundary current. St. Anna Trough, a relatively narrow and long trough in northern continental shelf of Kara Sea, plays a key role in remodeling temperature and salinity characteristics of AW, in which the AW from Fram Strait enters the trough and mixes with the AW from Barents Sea. Since the 21^st Century, AW in the Arctic Ocean has experienced obvious warming and had the influence on the physical processes in downstream Canada Basin, which is attributed to the anomalous warming events of AW inflowing from the Fram Strait. It is inferred that the warming AW is dominated by a long-term warming trend superimposed on low frequency oscillation occurring in the Nordic Seas and North Atlantic Ocean. As the Arctic Ocean is experiencing sea ice decline and Arctic amplification, the role of AW heat release in response to the rapid change needs further investigation.     

Mercury Anomaly in the Okinawa Trough Sediments—An Indicator of Modern Seafloor Hydrothermal Activity

The Okinawa Trough is located between the shelf-sea area of the East China Sea and the deep-sea area of western Pacific Ocean. More than 60 chemical elements in the sediments from the shelf area of the East China Sea, the Okinawa Trough and western Pacific Ocean were determined by advanced techniques including neutron activation analysis, X-ray fluorescence spectrometry, atomic fluorescence spectrometry and atomic absorption spectrometry. Quantitative comparisons of the element abundances of the sediments were made in terms of the enrichment coefficients (K) of the elements.K > 1.5 indicates enrichment (K = 1.5–2, weak enrichment; K = 2–4, strong enrichment) andK > 4, anomalous enrichment. The results show that the Okinawa Trough sediments are characterized by Hg anomaly and the enrichment of such elements as Au, Ag, Se, Te, Sb, Cd, Mn, Mo, etc. Detailed studies show that the excess Hg comes from hydrothermal solutions rather than from the continent, sea water, marine organisms, cosmic dust or volcanic rocks. Attributed to modern hydrothermal activities on the sea floor, Hg anomaly can be used as a geochemical indicator of modern seafloor hydrothermal activity. This project was granted by the National Natural Science Foundation of China.     

The chemical and physical characteristics of heavy metals in humus and till in the vicinity of the base metal smelter at Flin Flon, Manitoba, Canada

 Trace element geochemistry of humus (<0.425 mm) and till (<0.002 mm) collected in the Flin Flon-Snow Lake area, northern Manitoba and Saskatchewan, provides a regional context for assessing smelter contamination in the environment. The area includes a Cu-Zn smelter known to discharge As, Cd, Cu, Fe, Hg, Pb, and Zn. In this study, sequential extraction analyses, scanning electron microscopy and x-ray diffraction analyses were used on a suite of samples to determine: (1) the chemical and physical characteristics of heavy metals in surficial sediments related to distance from the smelter, (2) criteria for assessing the relative contribution of these metals from natural and anthropogenic sources, and (3) the potential of these metals for remobilization in the environment. Humus geochemistry reflects the anthropogenic and natural component of heavy metal concentrations. Smelter-related elements show anomalously high values adjacent to the smelter, decreasing with distance until background values are reached at 70–104 km, depending on the element. In humus, Zn is associated primarily with labile phases; Hg with non-labile phases. Adjacent to the smelter, high proportions and concentrations of Zn and Hg in non-labile phases, indicative of smelter-derived particulates, are confirmed by SEM examination. The particles occur as spheres, irregular grains, and with organics. With increasing distance from the smelter, the geochemical response to bedrock composition is more obvious than the anthropogenic input. Till geochemistry reflects the natural variation imposed by bedrock composition. At highly contaminated sites (<3 km from the smelter), increased percentages of smelter-related elements in labile phases suggests heavy metals are leached from humus to the underlying sediment. Received: 5 November 1996 · Accepted: 31 March 1997     

Proton-induced X-ray emission measurements of trace elements in water samples collected from an Indiana coal mining locality

A new method of simultaneous multi-elemental analysis, Proton Induced X-ray Emission (PIXE), was used to detect trace elements in waters associated with a coal strip-mining operation in southern Indiana. Stream, pond, and ground water samples were collected and analyzed monthly from, or near, Sulphur Creek in Sullivan County. The concentrations of 26 major and trace elements were determined in samples from eleven locations: K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, As, Se, Br, Rb, Sr, Mo, Cd, Sn, Sb, I, Ba, Hg, Pb, and U. Elemental concentrations fluctuated considerably throughout the 13-month sampling period and also among sampling sites. Nickel, Zn, As, Cd, Mn, Fe, and Ca were highest in the upstream water which was most acidic (pH = 2.9–4.0) because of old unreclaimed mining operations. The highest values recorded were Ni = 1662 ppb, Zn = 4953 ppb, As = 26 ppb, Cd = 93 ppb, Mn = 5063 ppb, Fe = 63 ppm, and Ca = 325 ppm. The concentrations of these elements decreased downstream as the pH of Sulphur Creek increased which was likely due to the influence of the calcareous glacial till cover in the area and the recent mining activity which disturbed overburden containing a high percentage of calcareous materials. Lead, I, Br, and Ti values were highest (661 ppb, 86 ppb, 70 ppb, and 45 ppb, respectively) in the ground water from the coal seam (pH approximately 7). Other elements which were relatively high in the pH 7 waters closest to the current mining operations (pond, stream, and groundwater) included K (17 ppm), Sr (3408 ppb), Ba (173 ppb), As (14 ppb), Rb (16 ppb), Sn (14 ppb), and Cu (3840 ppb). The highest Cu concentration was recorded at the point where drainage water from the mine entered Sulphur Creek. Gallium, U, Hg, and Mo were found in low (< 13 ppb for Ga and Hg; < 205 ppb for Mo and U) concentrations and only in the ponds within the mine.     

Platinum-group element contents of chromites from mafic–ultramafic layered flows, Abitibi greenstone belt, Ontario: implications for geochemical fractionation and mineral exploration

Summary ?The PGE contents of chromite separated from peridotite layers of Archaean mafic–ultramafic flows, Abitibi belt (Canada), indicate enrichment in Os–Ir–Ru (600 ppb) relative to Pd–Au (<5 ppb). Evidently, chromite was a sink for Ir–Os–Ru during melt-chromite fractionation in each of the flows. However, an additional phase, probably olivine, is required to explain the bulk Ir content of the sulphide-poor peridotites. In contrast, the chromite Pt contents range from <10 ppb to 400 ppb, with large variation in Pt/Ru (0.02–2.76) and Pt/Pd (5–400) ratios. The Pt enrichment may be related to the presence of Pt spinel structure compounds in oxidised melt, reflecting Fe–Ti spinel-related mineralisation in higher pyroxenite-gabbro layers. Received December 5, 2002; revised version accepted January 7, 2003     

Mercury in lake sediments of the Precambrian Shield near Huntsville, Ontario, Canada

 Long sediment cores (>1 m) were collected from eight Precambrian Shield lakes in southern Ontario, Canada and analyzed for mercury (Hg), loss-on-ignition (LOI), and a suite of 36 other elements. Results indicated at least 100-fold variation in sediment Hg concentrations between lakes in close proximity (from 450 ppb), comparable to the variation reported for lakes across the whole of Canada. Strong areal correlations between Hg concentrations and LOI (r ² =0.77), between Hg and other trace element concentrations (Pb, Zn, Cd, Sb, As, Br), and similarities in the vertical concentration profiles of Hg and LOI, all point to the importance of organic matter in the release, transport and redistribution of metals in watershed systems. The spatial pattern of Hg concentrations in deep, precolonial sediments (>20 cm) was found to mirror the pattern of Hg concentrations in modern surface sediments, an observation that was confirmed in a follow-up survey (r ² =0.85;n=25 lakes), indicating that natural processes govern the unequal distribution of Hg among these lakes. Between-lake differences in surface sediment Hg concentrations normalized to organic carbon (Hg/C) were also reflected by Hg concentrations in smallmouth bass normalized to 35 cm length (R ² =0.63;n=15 lakes). The latter relationship suggests that smallmouth bass and lake sediment indicators provide mutually supportive information regarding Hg loading to the lacustrine environment from geological sources in the watershed system. Received: 31 October 1996 · Accepted: 27 May 1997     

Arsenic and other Trace Metals in Sediments from the Kara Sea and the Ob and Yenisey Estuaries, Russia

Major (Al and Fe), minor (Mn) andtrace (As, Cd, Co, Cr, Cu, Hg, Li, Mo, Ni, Pb, Sb, Vand Zn) metals along with material of grain size<63 m, TOC and TN have been determined insediment grab and core samples from the Kara Sea, andthe Ob and Yenisey estuaries, Russia. Surprisingly,the levels of trace metals, with the exception of As,were much lower than was anticipated from speculativereports of extensive contamination in the Arcticmarine areas adjacent to the Siberian coastline ofRussia. Lithium normalization indicates that theabundance and distribution of the metals, with theexception of As and Mo, are controlled by theaccumulation of their fine grained aluminosilicatehost minerals at sites determined by hydrodynamicconditions in the Kara Sea and in the estuaries. Metallevels in the Kara Sea and the Ob and Yeniseyestuaries, except for some anomalous As, Cu and Nivalues, are close to natural baseline levels of otherEurasian Arctic shelf sediments. High levels of As,however, occur in surface and subsurface sediments.The accumulation of As, as well as Mo, can beattributed to the post-depositional diagenetic effectsof Fe-Mn cycling both at and near the sediment waterinterface. Subsurface As and Fe maxima and minimasuggest alternating oxic and anoxic water conditionsduring post-glacial rises in sea level. In contrast tothe results from the adjacent Pechora Sea, in the KaraSea there is no correlation between the levels of Asand radionuclides in the sediments.     

Environmental impact of mining waste disposal on a tropical lowland river system: a case study on the Ok Tedi Mine, Papua New Guinea

The 1000 km long Ok Tedi/Fly River system receives about 66 Mt/year of mining waste from the Ok Tedi copper-gold porphyry mine. Mine input has increased the suspended sediment load of the Middle Fly River about 5–10 times over the natural background. A significant yet unknown amount of copper-rich material deposits unevenly in the extensive tropical lowland floodplain. Recent alluvial sediments of the Fly River floodplain have copper contents of 620 mg/kg (±1σ: 430–900), whereas the regional background is 40 mg/kg (±σ: 25–60). This pattern is mirrored and enhanced by the gold dispersal pattern with a 7 ppb Au background versus a 140–275 ppb population in mine-derived material. Very high deposition rates (around 4 cm/y) of mine-derived sediment were determined in locations close to the creeks and channels which link the Fly River with the outer floodplain. A thin layer of 1–5 cm of copper-rich material (400–900 mg/kg Cu) was usually found on the bottom of drowned (tributary) valley lakes. Average dissolved copper content in waters of the inner floodplain is around 9 μg/l (±1σ: 5–14) as compared to unpolluted water from the outer floodplain with < 2 μg/l Cu. The present Fly River water, about 600 km downstream of the mine site, has concentrations of 17 ± 3 μg/l dissolved Cu. Received: 30 June 1996 / Accepted: 9 January 1997