2009:066
M A S T E R ' S T H E S I S
Geochemical Baseline Study of Gold Mineralization in the Barsele Area,
North Sweden
Elvis Tangwa
Luleå University of Technology Master Thesis, Continuation Courses Exploration and Environmental Geosciences Department of Chemical Engineering and Geosciences
Division of Applied Geology
2009:066 - ISSN: 1653-0187 - ISRN: LTU-PB-EX--09/066--SE
Master Thesis
Geochemical Baseline Study of Gold
Mineralization in the Barsele Area, North Sweden
Elvis Tangwa
Supervisor: Prof. Björn Öhlander
Luleå University of Technology
Master Thesis, Continuation Courses Exploration and Environmental Geosciences Department of chemical Engineering and Geosciences
Division of Applied Geology
ii
Quotation
“I have learned that success is to be measured not so much by the position that one has reached in life as by the obstacles overcome while trying to succeed.”
(Booker T Washington, 1856-1915)
iii
Abstract
Two lake sediment cores and 10 lake water samples were sampled at different depths to assess trace metal content and water quality prior to the possibility of mining two orogenic gold deposits at Barsele, North Sweden. Existing regional water data sampled at different seasonal conditions was provided. Data from the Swedish Environmental Protection Agency (SEPA), the Kalix River and Lake Kutsasjärvi were also used as reference data to quantify metal pollution and assess their possible impact on aquatic systems. Bedrock composition, location of ore body and existing assay data were equally reviewed.
Till close to gold deposits has high As but low base metal enrichment. Streams B7and B4 interacting with the ore bodies and mineralized till has a neutral pH and a good buffering capacity due to the weathering of calcite veins associated with ore bodies. Arsenic (18.2µg/l, SEPA class 4, Stream B7) is the most elevated in the drainage basin while Zn, Ni, Cu Hg, Mo, Cd and Pb in all surface waters are within the tolerance limit (SEPA class 1or2).
Sorption onto Fe- oxy hydroxides in addition to a near neutral pH seems to limit greatly the mobility of heavy metals but less on the mobility of As due to its ability to form mobile complex anions. Lake water has a relatively low metal content due to its neutral pH and its near stable oxygen concentration. Arsenic (SEPA class 4) is particularly enriched in lake sediments, in association with precipitation of Fe-oxyhdroxide. Copper and Ni are equally elevated in lake sediments. Generally, metal enrichment in lake sediment is higher at sampling station A compared to station B and reflects variations in redox processes and the recycling of Fe-Mn. Although lake water and mineralized streams have a good buffering capacity, their metal content could be upgraded once mining begins because large volumes of rocks will be exposed to weathering. Thus, adequate measures should be taken to dispose waste rocks and monitor water chemistry.
Keywords: water chemistry, lake sediments, trace elements, arsenic pollution, gold
mineralization, Barsele
iv Table of Contents
Quotation ... ii
Abstract ... iii
Table of Contents ... iv
1 Introduction ... 1
1.1 Background Information ... 1
1.2 Location of Study Area ... 2
1.3 Objectives ... 3
2. Bedrock geology and mineralization ... 4
2.1 Regional Geology ... 4
2.2 Geology of Barsele Area ... 6
2.3 Mineralization ... 6
2.4 Quaternary Geology and Mineralization ... 8
3) Materials and Methods ... 12
3.1 Regional water ... 12
3.2 Lake water and Lake Sediments ... 12
3.3 SEPA Data ... 15
4. Results and Discussions ... 16
4.1: Bedrock Assay ... 16
4.2: Till/Soil ... 19
4.3 Regional Water ... 23
4.4 Lake water ... 32
4.5 Lake Sediments ... 35
5. Conclusions and Recommendations ... 41
Acknowledgments ... 42
References ... 43
Appendices ... 46
Appendix 1: lake water station A ... 46
Appendix 2: lake water station B ... 46
Appendix 3: lake sediments Station A ... 47
Appendix 4: lake sediments station B ... 48
1
1 Introduction
1.1 Background Information
Geochemical Baselines, refers to the natural variation in the concentration of an element in the superficial environment (Salminen and Gregorauskiene, 2000 and Salminen and Tarvainen, 1997). Geochemical baseline studies provide information which might be indicative of an ore occurrence (e.g. Hawkes and Webb 1962) or it may provide guidelines for environmental legislation; because it prescribes limits for heavy metals in contaminated land and other surficial materials as defined by environmental authorities, (Salminen and Tarvainen, 1997). Baseline concentrations depends on sample material collected, grain size, analytical and extraction methods (Rose et al., 1979). For this reason, common challenges with baseline studies include the fact that sometimes different scales or averages or boundaries are used. Moreover, detail information regarding how regulatory levels have been established may be lacking. Hence, baseline concentration may vary for different countries and even within a particular project area, (Reimann and Garett, 2005). In this study, guidelines provide by the Swedish Environmental Protection agency (SEPA) and also data from the Kalix River and Lake Kutsasjärvi which are both unpolluted and unmineralized surface waters in north Sweden have been used to assess metal pollution in surface waters and lake sediments in the Barsele area. The SEPA guidelines prescribes different ranges of concentration for different elements in different sampling media taking into account the adaptability level of biological systems under different metal concentrations and environmental conditions. As a means to quantify metal pollution, SEPA has grouped these ranges of element concentrations into five different classes, (Table2 and 3).
Gold mineralization in the Barsele area is one of the more than 85 pyritic Zn-Cu-Au-Ag massive sulphide deposits that make up the well known mineralized Skellefte district in north Sweden (Weihed et al., 1992). In such a region where sulphides have concentrated several orders of magnitude than their average crustal concentrations, Acid Rock Drainage (ARD) is a common environmental problem likely to be experienced before, during and after mining.
Hence, background metal concentrations in sediments or till, surface water and subsequently groundwater will vary and may greatly deviate from those in unmineralized areas (Rose et al., 1979). More to these problems is erosion, loss of biodiversity and the leaching of processed water onto surface and ground water during mineral exploitation. For these reasons, accountability and environmental performance are important issues for mining companies today. To meet these challenges and mitigate their effects on the environment, it is important to understand the inherent hydrogeochemical conditions as well as the geochemistry of lake sediments in the study area.
In keeping with environmental standards and to prepare the company for any future
exploration and mining operations, preliminary hydrogeochemical study was carried out in
the Barsele area by Pelagia Environmental AB, an environmental consulting firm on behalf of
Northland Resources AB. As a follow up to this study, the geochemistry of lake water and
lake sediments in addition to existing regional water data provided by Pelagia Environmental
AB were further studied. In this study, metal content in bedrock, till, surface water and lake
sediments have also been studied and compared to their average crustal concentrations and
their concentrations likely to be observed in an unmineralized river such as the Kalix River
2 (Pekka et al., 2008) and also in an unmineralized lake such as Lake Kutsasjärvi, (Peinerud, 2000).
However, besides bedrock composition, the geochemistry of surface water is also controlled by factors such as pH, relief, climate, oxidation-reduction, adsorption and the mixing of waters (Levinson, 1974). On the other hand, the geochemistry of lake sediments is influenced by particle size, redox processes, sedimentation rate, groundwater composition, chemical speciation, and the recycling of Mn-Fe in pore water, (Stumm, 1885).
Gold exploration in the Barsele area was initiated by Terra Mining INC (1984-1998) followed by MimMet PLC (2003) and then Northland Resources INC (2004). Presently, Northland Resources AB, a subsidiary of Northland Resources INC, a Canadian Exploration /mining company is actively involved in Fe, Cu and Au exploration in Finland and North Sweden (Barsele technical report 2006).
1.2 Location of Study Area
Regionally, Barsele is located about 230km from Umeå and about 519km from Kiruna.
Barsele has an undulating relief which is characterized by wide plains and isolated hills occurring at slightly different altitude. Hills are dominant in some location and could reach an altitude of 791m, while plains lay at an altitude of about 260 – 400m, Geological Survey of Sweden (SGU). Barsele and its environs are surrounded by numerous lakes, rivers and streams and a thick coniferous forest. Annual precipitation ranges between 800 to 1,000 millimetres. Winter conditions prevail from late November to early/mid April with snow cover normally in the range of 50 to 75 centimetres.
The project area is located some 40 kilometres east-southeast of the town of Storuman in
Västerbottens Län, a regional district of northern Sweden. The geographical coordinates of
the project area are approximately 65
0.05` north latitude and 17
0. 30` east longitude,
(Figure 1)
3 Figure 1 Location map of Barsele and its Environs
1.3 Objectives
The main objectives of this study are to:
a) Evaluate the hydrogeochemical conditions of Barsele and its environs and provide baseline information against which any potential impact of future mining operations on water quality and metal content in lake sediments can be assessed.
b) Interpret existing regional water data and to supplement existing results provided by Pelagia Environmental AB.
c) Correlate and account for variations between metal content with depth in lake water and lake sediments.
d) Understand the influence of climate, geology, proximity of ore body on the
geochemistry surface water and lake sediments.
4
2. Bedrock geology and mineralization 2.1 Regional Geology
The project area occurs within the Skellefte district which covers an area of 120km by 30km and is located on the Paleoproterozoic part of the Fennoscandian Shield. The Fennoscandian Shield is dominantly made up of Achaean, Proterozoic gneisses and greenstone rocks which have undergone several episodes of deformation throughout history with a peak in most areas during the Svecokarelian orogeny c 1.90 and 1.80 Ga, (Lundqvist et al., 1998b; Bergman et al., 2001). Sedimentary and felsic magmatic rocks of low to medium metamorphic grade, elongated in a NW-SE direction are the dominant rocks in the Skellefte district, (Weihed et al., 1992). These metasedimentary and metavolcanic rocks in a regional context constitute the Svecofennian rocks system. In the study area, these rocks are without any known Achaean basement, (Mellqvist et al., 1999 and Richard 1986). Generally, granites especially the Revsund granite are the most abundant covering about 70% of the Skellefte district (Richard 1986, Fig 2.1.) They are generally course-grained, porphyrytic and light gray in colour.
Within the granite areas, there are several rather large granodiorite intrusive which have been greatly deformed. Granites and supracrustal rocks are often cut by dolerite dykes especially in the in the project area (Weihed, 1992b, Fig 2). Felsic volcanic rocks in this region have been interpreted as pyroclastic rocks formed due to a violent explosive submarine volcanism at large volcano which resulted to the scattering of these rocks in the district. (Lundberg, 1980;
Richard, 1986; Vivallo and Classon, 1987).
The west end of the Skellefte district is bordered by Caledonian rocks which are mainly Neoproterozoic to Silurian metasedimentary and metavolcanic rocks. These rocks lie structurally on top of the autochthonous, plat formal cover sequence to the Precambrian crystalline basement rocks, (Stephens et al. 1997)
The south east of the Skellefte district is dominated by metasedimentary rocks which occur within a sedimentary basin, the Bothnia basin. These metasedimentary rocks contain remnants of older volcanic rocks c. 1.95Ga which are confined to the Knaften and Barsele areas. Still within the south east of this district, intrusive granites and some pegmatites are associated with high grade gneissic and migmatitic equivalence of supracrustal rocks. These intrusives are commonly referred to as the as Skellefte granites and date about 1.80Ga (Weihed et al., 2002; Romer and Smeds, 1994). Similar granites to the south are referred to as Härnö granites (Classon and Lundqvist, 1995).
The northern part of the Skellefte district consist of extensively less deformed and less altered supracrustal rocks. They are mainly of brown continental felsic intrusion, porphyrytic lavas, sub volcanic intrusions and tuffs and minor sediments called Arvidsjaur Group. The Arvidsjaur Group is topmost layer of the regional stratigaphy of the Skellefte district. Under laying this layer is the Vargsfor which together with the Arvidsjaur group are with or with any major unconformity (Skiöld et al.; 1993 & Billström and Weihed 1996). They are red in colour, often oxidized, have high potassium content and occur in association with welded ignimbrites and accretionary lapilli and strongly resemble rocks of lower horizon, the Skellefte Group, (Barnstorm 2001). The Vargfors Group is composed of fine to coarse- grained sedimentary rocks such as conglomerates with some intercalations of volcanic rocks.
Under laying the Vargfors group is the Skellefte group. They are notably; acid porphyry
characterized by volcaniclastic rocks, mainly rhyolite and rhyodacites, coherent sub volcanic
porphyrytic intrusion lavas and intercalated sedimentary rocks such as mudstones, breccias
and conglomerates, (Allen et al., 1996b). Some coarser sedimentary rocks occur within the
5 Skellefte Group and are lime-cemented, but only very rarely does limestone occur within the Skellefte Group. They were emplaced between 1880-1890Ma and have a complex internal stratigaphy, (Billstöm and Weihed.; 1996). Lundberg (1980) interpreted the depositional environment of many of these volcanic rocks as shallow water or sub aerial. More about the regional stratigaphy of the Skellefte district has been extensively studied by (Allen et al., 1996b)
Figure 2: Bedrock Maps of Barsele and its Environs showing, the main lithological units. Map produced by the Geological Survey of Sweden (SGU 2003)
6 Tectonically, the Skellefte District is considered to be a remnant of a ca. 1.9 Ga Palaeoproterozoic volcanic arc formed at the margin of an Achaean continental landmass (Allan et al, 1996). The Svecofennian rocks in this district are known to have been formed after the final break-up of the Karelian Craton at c.a 1.95 Ga and Svecokarelian Orogeny.
During these processes, a sedimentary basin, the Bothnian basin was formed towards south.
Within this basin, quartzite, conglomerates, turbidites and graphite schist were deposited and later metamorphosed in the lower to upper amphibolites facie .These rocks were later intruded by different types of granitites during the c 1.9-1.8 Ga Svecokarelian Orogeny (Claesson &Lundqvist 1995).
2.2 Geology of Barsele Area
The project area lies within a boundary-zone between the Bothnian metasedimentary basin to the south and a volcanic province to the north (Barsele project technical report, 2006).
Metasedimentary and metavolcanic rocks are the most common, with the metasedimentary rock being the most abundant, (Figure 2). The metasedimentary assemblages include:
metamorphosed greywacke which are the most abundant, pelites and to a lesser extend conglomerates equally exist. The metavolcanic rocks consist of felsic, intermediate, mafic, pillow lava and pyroclastic materials (Richard 1986). The metagraywackes are rich in graphite and equally contain sulphides minerals. Both rocks are very similar in all aspects with no clear cut distinction due to alteration and deformation. They are blackish gray, biotite-rich, and less coherent in appearance. They also contain a higher density of mainly quartz and feldspar porphyroclasts and thin calcite veins. However, the metavolcanic rocks are dark grey in colour, contain amphibole as the main mafic mineral and are more uniformly carbonate-altered (Bark et al.; 2007). The metavolcanic rocks are more specifically referred to as the Härnö Formation and were probably deposited in a back-arc setting. The felsic volcanics are thought to represent a volcanic inlier within the Bothnian Basin, or alternatively, an outlier of the Skellefte district (Classon and Lundqvist, 1995).
These rocks are strongly foliated with a roughly N–S trending and have steeply dipping foliation planes. They show variable amounts of mainly quartz and feldspar porphyroclasts and phenocrysts in a more fine-grained matrix. Most supracrustal rocks at Bersele like in most parts of Sweden and Finland have been intruded by granitoids, mainly tonalite or diorite dykes, (Weihed, 1992b, Figure 2).
2.3 Mineralization
Mineralization in most parts of north Sweden is associated with Paleoproterozoic rocks. The Skellefte District hosts over 85 pyritic Zn-Cu-Au-Ag Volcanogenic Massive Sulphide (VMS) deposits, (Allen et al., 1996 and Wiehed et al., 1992). The District also hosts a few porphyry- type low-grade Cu deposits and a good number of orogenic gold deposits in different geological settings, including shear zones (Weihed et al. 1992).
The Barsele area hosts both orogenic and epithermal gold rich VMS deposit. Orogenic gold is
confined to the Barsele central, the Avan, and the Skiråsen zones while epithermal gold is
confined to the Norra zone respectively, (Barsele technical report, 2006, figure 3)
7 Figure 3 Map showing location of main ore bodies in project area
Orogenic gold mineralization at Barsele is one in a series of 14 well known gold deposits related to the NW–SE trending belt of Au in till often referred to as the ―gold line‖, (Figure 4). Epithermal gold on the other hand is mostly associated with faults and fractures. Gold occurrence is predominantly within a granodiorite that ranges in width from 200 to 500 metres with a strike-extent in excess of some 8 kilometres (Barsele Technical report 2006).
Like in most parts the Skellefte district gold in the Barsele area occurs as native metal locally alloyed with silver, and demonstrates a general association with arsenopyrite also occurring with pyrrhotite, calcite, chlorite and biotite. Base metal content of the deposit is typically low (Barsele Technical Report 2006)
Norra
Avan
Barsele central
Skiråsen
8
Figure 4 Gold content in the till overburden, Västerbotten County. Data from the Geological Survey of Sweden2.4 Quaternary Geology and Mineralization
Till and discontinuous soil covers are the dominant quaternary deposits at Barsele and its environs. The thickest till cover occur at the bottom of wide valleys and extensive plains (Rudberg 1954). These valleys and plains are characterized by ablation and glaciofluivial till which are generally coarse-grained, less compacted and well sorted (Ivarsson, 1992). There equally exist local occurrences of peat deposits in some plains (SGU, 2003)
On hill summits, till is generally shallow or absent and forms discontinuous covers on bedrock (Figure 5a). The thickness of till cover on hills hardly excess 2m and their morphology closely follow the topography of the underlying bedrock (Ivarsson, 1992).
However, coarser and thicker till covers of up to about 5-20m usually occur on lee side positions of hills while basal till (fine till) which is more compacted and has a comparatively high content of fine fraction occurs on the hill side (Ivarsson, 1992). Glaciofluivial sand and glaciofluivial gravel equally occur with glaciofluivial grave being the most common.
Till in areas greatly affected by wave ablation is generally coarse-grained and sometimes
have boulder-sized fractions oriented in the direction of ice movement (SGU, 2003). Such
deposits compared to fine till are generally enriched in SiO
2and impoverished in the fine
9 fractions and base metals (Haldorsen, 1982). Generally, fine silt and clay deposit are rare. A total of 35 samples collected by SGU from an average depth of 2 to 3m show that homogenous sandy to silty till usually about 0.5m thick overlies a rather heterogeneous deposit. In most parts of Barsele the boundary between both deposits can be sharp or gradual.
According to Granlund (1943), areas dominated by the Revsund granites are particularly characterized by sandy to silty till compared to finer till in areas dominated by supracrustal rocks. He equally observes that granite dominated areas have <25% fine fraction (silt + clay) with less than 12% heavy minerals while areas dominated by metasedimentary and gneissic rocks have about 45% and 30% silt +clay respectively. Till samples collect by Northland Resources AB at depths ranging from 0 to 21m show great variation in physical and chemical composition. Generally clayey silt is the dominant fine fraction and could be rusty (sulphide enrichment), black brown, and could contain argillite or granodiorite clast. Elsewhere, clays are mostly dark gray to light gray and could also be orange, yellow, yellow green, silty or sandy, and tan with argillite clast. Silt could be sandy, clayey and could contain graphite in few locations. Till mostly contains angular to subanglar pebbles or fragments of granodiorite, granite, quartz schist, black shale and rarely fragments of conglomerates, graywackes, amphibolites, metavolcanics and massive sulphides. Very high As and Cu in till occurs between 0 to 2.4m and sometimes to about 4.2m below the surface. Elevated concentrations of As and base metals are associated with dark gray clays, black shale, clayey silt, yellow orange clay, greenish gray clay, clay with mica, chlorite, schist, amphibole and pyrite in greywacke but rarely with light clays, except Pb which shows high metal content in some cases, (Figure 7a and 7b) . Till with angular to sub rounded fragments of schist, and till with traces of sulphides in granodiorite also have high metal content. A study form a total of 293 samples by (Ivarsson et al., 1992) shows that soil and till pH varies from 4 at the coast of västerbotten to 5.2 inland and around the study area. The study equally shows that Granite dominated areas have a relatively low pH compared to area dominated by metasedimentary, mafic and granodiorite rocks.
The direction of ice movement based on 250 points shows that most bed rocks have two
main directions of ice movement; the older is about 280
0from the west and the younger
which is 310
0-225
0from the NW is considered to be the dominant direction of flow (SGU,
2003, Figure 5b). Ice flow in most cases is more or less parallel with large river valleys,
boulders and drumlins. (Bergström, 1968).
10
Figure 5a: Till/soil map of Barsel. Project area enclosed in rectangle. Map from the Geological Survey of Sweden (SGU, 2003)11 Figure 5b: Direction of ice movement; from oldest to youngest. Map from (SGU)
12
3) Materials and Methods 3.1 Regional water
A total of 160 regional water samples were collected by Pelagia Environmental AB from 10 sampling stations in 8 water bodies (1 lake, 6 streams and 1 river, Table 3.1). Samples were collected at different seasonal conditions from October 2001 to September 2002 and again from May 2005 to November 2008 to check for variations in chemical composition. Each stream was given a reference number for convenience. Samples from all sampling stations were taken from a depth of 0.2m except for station B3b, where water samples were collected from a depth of 1m. Samples were filtered in situ using a 0.45µm pore size membrane filter and analysed for Ca, Mg and Fe using ICP-AES and As, Cu, Pb, Zn, Ba, Cd, Ni, Co, Hg and other heavy metal using ICP-AM methods (Pelagia Environmental AB, 2008)
The analytical ICP regional water data provided for this thesis was analysed and interpreted separately and based on the name of each stream
Table 1 (a) Streams sampled by Pelagia (red dots figure 5) and their respective coordinates. Data compiled by Pelagia Environmental AB
River Local Reference Number of Samples Coordinates
Vintervägabäck B1 20 7214535/1582810
Skirträskbäcken B2 20 7214701/1582872
Skirträsket B3y 18 7217070/1580900
B3b 14 7217070/1580900
Stentjärnbäcken B4 20 7217820/1579739
Främmentjärnbäcken B5 20 7217916/1579779
Umeälven upp B6 13 7215880/1574550
Barseleavanbäcken B7 11 7216422/1579258
Umeälven ned B8 13 7207672/1583727
Godängesbäcken B15 11 7217800/1576440
3.2 Lake water and Lake Sediments
In April 2009, sampling was done at two sampling stations in Lake Skirträsket: station A and station B, (Table 3.1). Both sampling stations are located about 250m and 180m respectively from the banks of the lake, figure 5. Prior to sampling, water depth at station A (17.8m) and station B (19.6m) was investigated using an echo sounder. The geographical coordinates of sampling stations were noted with the aid of a global positioning system (GPS), (Table 1b).
Table 1(b) Lake sampled and their corresponding sampling stations (blue dots fig 3.1), depth, number of samples collected and coordinates
Lake Sampling
stations Depth Number of water
samples Number of
sediment samples Coordinates
Skirträsket A 17.8 5 5 7216960/1580721
B 19.5 5 5 7215928/1581341
13 Water pH, conductivity and temperature, were equally investigated in situ using a Hydrolab minisonde (water quality miniprobe). At station A, five lake water samples from different depths were collected. Simultaneously, 5 lake sediments samples were collected from the same sampling station using a sediment corer. The same procedure was repeated at sampling station B. The equipment for water sampling consisted of 12V battery (power source) connected to a pump onto which pipe was connected a tube to allow the follow of water.
Water samples were collected at intervals of one minute during which pumping voltage was increased from 2V to 7V to allow water retained in the tube from the preceding depths to be flushed out. Prior to water sampling, sample containers (plastic bottles) were rinsed three times with water to avoid contamination. Samples from each depth were filtered using a 0.22µm filter to separate the dissolve fraction from the particulate fraction. Samples were then collected in plastics bottles and labelled on paper tapes based on their respective depths and sampling stations. After sampling, water samples were stored for two days at a temperature of 4
0C and analysed for Al, Ca, Fe, K, Mg, Na, S and Si using the ICP-AES methods. Arsenic, Ba, Cd, Co, Cr, Cu, Hg, Mn, Mo, Ni, P, Pb, Sr, and Zn were analysed using ICP-SMS methods at ALS Scandinavia, an accredited analytical laboratory in north Sweden, (appendix 1 and 2). Lakes sediments cores about 30cm thick from each sampling station were collected by slowly deploying to the bottom of a Lake Skirträsket, a sediment corer on to which a meter tape was attached to check the depth and speed of deployment.
Once collected, sediment cores were sliced at intervals of 1cm. They were then collected in plastic containers and labelled based on their respective sampling stations. Just like water samples, they were stored at a temperature 4
0C for two days and then analysed for SiO
2,Al
2O
3,CaO, Fe
2O
3, MgO, MnO, Na
2O, P
2O
5, TiO2, LOI, As, Ba, Cd, Co, Cr, Cu, Hg, Mn,
Mo, Ni, P, Pb, Sr, and Zn by ICP methods at ALS Scandinavia, (appendix 3 and 4).
14
Figure 5: Map showing sampling station, streams and rivers in the projectBlue dots: sampling stations for lake water and sediment. Red dots: sampling station for surface waters
Bedrock assay and till assay data for samples collected at depths in the range of 0 to21m was provided by Northland Resources AB, and was further studied. The average concentrations of a few metals in rivers around the project area were compared to the average concentration in a typically unpolluted or unmineralized river like the Kalix River in northern Sweden (Table 4). To assess metal enrichment in lake sediments, analytical data of As, Cu, Ni, Pb and Zn were compared to date from Lake Kutsasjärvi, (Table 7).
Umeälven upp, B6
Godängesbäcken, B15 Främmentjärnabäcken, B5
Stentjärnbäcken B4
Barseleavanbäcken, B7
Skirträsket, B3y, B3b
Station A, SSA
Station B, SSB
Skiräskbäcken, B2
Vintervägabäcken, B1
Umeälven ned, B8
15
3.3 SEPA Data
To assess the magnitude of metal pollution on surface water and its possible effects on aquatic and biological systems, analytical data was compared with data from the Swedish Environment Protection Agency (SEPA, Table 2). To quantify metal pollution in lake sediment, metal concentration in lake sediments were also compared with data from SEPA.
Table 2: Classification of water quality status (SEPA, 4913)
Metal concentration in water (µg/
l)
Class Description
As Cd Cu Ni Pb Zn1
No or low risk ofbiological effects <0.4 <0.01 <0.5 <0.70 <0.2 <5
2
Low risk of biologicaleffect 0.4-5 0.01-0.1 0.5-3 0.7-15 0.2-1 5-20
3
Biological effects can occur5-15 0.1-0.3 3-9 15-45 1-3 20-60
4
Increasing risk for biological effects esp. in soft nutrient poor, humus poor acidic water15-75 0.3-1.5 9-45 45-225 3-15 60-300
5
Survival of aquatic organism is affected even after short exposure>75 >1.5 >45 >225 >15 >300
Table 3. Classification of metal content in sediment based on (SEPA) standards Class Description Cu
(mg/kgTS) Zn (mg/kgTS)
Pb (mg/kgTS)
Ni (mg/kgTS)
As (mg/kgTS)
Hg (mg/kg TS)
Cd (mg/kg TS) 1 Very low
concentration
<15 <150 <50 <5 <5 <0.15 <0.8
2 Low
concentration
15-25 150-300 50-150 5-15 5-10 0.15-0.3 0.8-2
3 Moderately high
concentration
25-100 300-1000 150-400 15-50 10-30 0.3-1.0 2-7
4 High
concentration
100-500 1000-5000 400-2000 50-250 30-150 1-5 7-35
5 Very high concentration
>500 >5000 >2000 >250 >150 >5 >35
16
4. Results and Discussions 4.1: Bedrock Assay
Gold enrichment in bedrock varies from 0.4ppm to 67,000ppb compared to 0.004ppb as its average crustal concentration (Levinson 1974, table 4.2) and reflects its high enrichment in the ore body, (figure 6a). The concentration of As varies from 0 to 99999 ppm compared to 1.8ppm as its average crustal concentration. Roughly more than 95% of As concentration is above the average crustal concentration (figure 6b). This trend also reflects its high content and close association with Au. The concentration of Copper varies from 0 to 105430ppm. It can be said that more than 75% of Cu in ore body is below crustal concentration (figure 6c).
Zinc varies from 0 to 99999ppm with about 49% of its content in ore body below average crustal concentration (figure 6d). The concentration of Pb varies from 0 to 23259 with about 46% of its concentration below the average crustal value (figure 6e). About 89% of Ni is below crustal concentration. These trends supports earlier studies showing that the gold mineralization in the ore body is strongly associated with arsenopyrite and also the fact that base metal enrichment in the ore body is low compared Au (Barsele technical report 2006, Bark 2007).
Figure 6a: Variation of As concentration in bedrock assay
0 1000 2000 3000 4000 5000 6000
0 5 10 15 20 25
0-1.8 89-132 265-308 397-440 529-572 749-792 881-924 1013-1056 1145-1188 1321-1364 1453-1496 1589-1628 1717-1760 1849-1892 1981-2024 2465-2508 2685-2728 2949-2992 3741-3784 4049-4092 4269-4312 4621-4664 4885-4928 5017-5060 5457-5500 5763-5808 5985-6028 6251-6292 7261-7304 11001-11044 99969-100012 Frequency
% frequency
Range (ppm) As in bedrock assay
17
Figure 6b: Variation of Au concentration in bedrock assayFigure 6c: Variation of Cu concentration in bedrock Assay.
0 2000 4000 6000 8000 10000 12000 14000 16000
0 10 20 30 40 50 60
0-45 136-180 271-315 406-450 541-585 676-720 811-855 946-990 1081-1125 1216-1260 1351-1395 1486-1535 1626-1670 1761-1805 1896-1940 2031-2075 2166-2210 2301-2345 2436-2485 2981-3025 3116-3160 4016-4160 5051-5095 6041-6085 7976-8020 9011-9055 10046-10090 14996-15040 30206-30250 66970-67015 Frequency
Frequency %
Range(ppb) Au in bedrock assay
0 10 20 30 40 50 60 70 80 90
0 5000 10000 15000 20000 25000
0-44 133-176 265-308 397-440 529-572 661-704 793-836 925-968 1057-1100 1189-1232 1321-1364 1453-1496 1589-1628 1717-1760 1937-1980 2069-1212 2201-2244 2333-2376 2465-2508 2597-2640 2861-2904 2993-3036 4621-4664 5941-5984 9989-10032 18085-18128 105425-105468 frequency %
frequency
Range (ppm) Cu in bedrock assay
18
Figure 6d: Variation of Zn concentration in bedrock assay.Figure 6e: Variation of Pb concentration in bedrock Assay.
0 5 10 15 20 25 30 35 40 45
0 2000 4000 6000 8000 10000 12000 14000
0-45 136-180 271-315 406-450 541-585 676-720 811-855 946-990 1081-1125 1216-1260 1351-1395 1486-1535 1626-1670 1761-1805 1896-1940 2031-2075 2166-2210 2301-2345 2436-2485 2981-3025 3116-3160 4016-4160 5051-5095 6041-6085 7976-8020 9011-9055 10046-10090 14996-15040 30206-30250 66116-66160 Frequency %
Frequency
Range (ppm) Zn in bedrock assay
0 10 20 30 40 50 60 70 80 90
0 5000 10000 15000 20000 25000
0-44 89-132 177-220 265-308 353-396 441-484 529-572 617-660 705-748 793-836 881-924 969-1012 1057-1100 1145-1188 1233-1276 1321-1364 1401-1452 1497-1540 1589-1628 1673-1716 1761-1804 1849-1892 1937-1980 2157-2200 2289-2332 2377-2420 2553-2596 2641-2684 2729-2772 2817-2860 2949-2992 3125-3168 4973-5016 7041-7084 8978-9021 9990-10033 11001-11044 15401-15444 19713-19756 Frequency %
Frequency
Range (ppm)
Histogram plot for Pb in bedrock assay
19
Figure 6f: Variation of Ni concentration in bedrock Assay4.2: Till/Soil
Table 4. Median metal content in till and bedrock assay compared to their crustal abundance. Au in ppb, S in % while Ag, As, Cu, Fe, Mn, Mo, Ni, Pb and Zn in ppm (levinson, 1974
)
Element Bedrock Till Average crustal
concentration (levinson, 1974)
Ag (ppb) 0.3 0.225 0.007
As (ppm) 180 35 1.8
Au (ppb) 51 7 0.004
Cu (ppb) 25 38 55
Fe (ppb) 9.2 3.25
Mn (ppb) 463 401.5 950
Mo (ppb) 2.5 3 1.5
Ni (ppb) 23 42 75
Pb (ppb) 19 16 12.5
S (%) 0.3 0.23
Zn (ppb) 91 100 70
Arsenic, Au and base metals are equally elevated in till, though to a lesser extent. Generally till around ore body has very high concentration of As and heavy metals, (figure 8a, 8b, 8c and 8d). It can be said that dispersed clastic sulphide mineralization in biotite, chlorite, amphiboles, granodiorite and pyrite which are associated with clayey silt, black clays, and
0.00%
10.00%
20.00%
30.00%
40.00%
50.00%
60.00%
70.00%
80.00%
0 5000 10000 15000 20000 25000
Frequency %
Frequency
Range (ppm) Ni in bedrook assay
20 gray clays are probably the main sources of these elements, (fig 2.1 fig 7a, fig 7b,). Till with such composition are mostly associated with the weathering of mafic metavolcanic.
Elevated metal concentrations could also be due the occurrence of shallow soils in which metals released from bed rock have been deposited in situ. High As and base metal concentration in some locations could be due to local occurrence of transported soils or the occurrence of possible ore bodies. The concentration of Cu, Mo, Ni, and Zn are higher in till compared to bed rock and could mainly be due elevated concentrations in shallow soils. It could as well be that their release rates are lower than their input from bedrock, (Land, 1998).
Arsenic, Au, Ag, Fe, S and Mn generally have a higher concentration in bed rock compared to till.
Figure 7a: fine fraction type in till
Figure 7b Metal content in till fine fraction
0.00%
5.00%
10.00%
15.00%
20.00%
25.00%
30.00%
35.00%
40.00%
clay silt Lt gray clay Dark clay+shale fine sand+sand silt
Silt+clay Others
Freq %
Fine fraction
Frequency % of fine fraction type in till
0 100 200 300 400 500 600 700 800 900 1000
clay silt Lt gray clay Dark clay+shale fine sand+sand silt Silt+clay Others
Average metal conc. (ppm)
Fine fraction
Trace metal conc. in fine fraction type in till
Zn Pb Ni Mn Cu As
21
Figure 8a. Thematic map of Arsenic in tillFigure 8b Thematic Map of Copper in Till
22
Figure 8c Thematic Map of Zn in TillFigure 8d Thematic Map of Pb in Till
23
4.3 Regional Water
Table 5: Average metal concentration, pH and other measured parameters in some streams and rivers at Barsele compared to those in the Kalix River, North Sweden
Measured parameter
Average Concentration in Rivers and Streams Around Project Area
Average Concentration in unpolluted Freshwater (e.g. Kalix River, North Sweden)
B1 B2 B3y B3b B4 B5 B6 B7 B8 B15
As(µg/l) 0.5
±1.1E-04 2
±2.8E-04 2
±2.5E-04 1.8
±8.1E-04 4.8
±0.001 1
±1.9E-04 0.18
±7.9E-05 18.2 ±5.8E- 03
0.16
±7.78E- 05
0.57
±8.0E-05 0.14
Ca(mg/l) 7.68
±1.6
9.6
±071 9.6
±0.94
9.5
±0.69
9.97
±1.16
8.94
±1.8
3.96
±1.2
24.9
±4.32
4.07
±0.85
4.17
±0.96
Cd (µg/l) - - 0.077 - 0.0043 - - 0.0022 - 0.0016
Cr (µg/l) 0.19
±7.3E-05
0.008
±2.1E-05 0.01
±1.4-04
0.009
±4.0-E04 0.016
±9.0E-05 0.027
±1.5E-04 0.012
±6.9E-05 0.016
±1.0E-04 0.015
±1.6E-04 0.023
±7.9E-05 Cu(µg/l) 1.25
±1.1E-03
0.78
±5.4E-04 1.6
±6.6E-04 1.2
±2.3E-03 0.97
±6.7E-04 0.93
±6.0E-04 1.1
±8.1E-05 1.2
±8.8E-04 1.12
±0.0017 1.08
±8.7E-04 0.5
Fe(µg/l) 96.6
±0.37
3 4 0.065 34
±8.4E-04 137
±0.06
128
±0.046 88
±0.256 77.5
±0.042 112
±0.053 492
Mg(mg/l) 0.89
±0.19
0.77
±0.18
0.74
±8.3E-02 0.74
±0.05
0.65
±7.9E-02 0.857
±0.21
1.26
±2.1
1.5
±0.301 1.35
±2.268
0.796
±0.18 1.3
±0.28 Ni(µg/l) 1.1
±3.5E-04
0.34
±9.1E-05 1.2
±5.7E-04 0.93
±1.8E-03 0.37
±8.2E-05 0.64
±1.3E-03 0.89
±6.5E-04 0.9
±3.8E-04 1.4
±2.3E-03 0.95
±3.1E-04 0.35 Pb (µg/l) 0.067
±8.8E-05
0.046
±3.4E-05 0.08
±8.7E-05 0.7
±1.7E-03 0.1
±8.1E-04 0.1
±2.1E-04 0.83
±0.0019 0.039
±3.0E-05 0.136
±1.5E-04 0.048
±3.3E-05 0.04 Zn(µ/l) 3.1
±1.9E-03
1.4
±7.2E-04 7.6
±4.0E-03 3.8
±6.5E-03 2.1
±8.5E-05 1.85
±6.3E-04 3.6
±2.1E-03 4.4
±1.2E-03 3.3
±3.8E-03 5.5
±0.0012 0.74 Alkalinity
mgHCO3/L 20
±7.2
25.72
±1.6
26.17 1.72
26.09
±0.94
25.71
±6.94
24.35
±7.5
10.77
±4.69
66.90
±18.6
11.66
±3.2
10.5
±4.6 21.17
±58.6 Conductivity
(µS/m)
55
±1.2
65.9
±0.63 66
±0.49
65
±0.17 65
±1.27 76
±7.3
31.6 0.98
146
±2.87
34.6
±0.531 35.5
±0.74
43.2
Sulphate(mg /l)
6.47
±2.3
5.15
±0.47
7.37
±4.9
5.32
±0.33 5
±2.68
5.73
±5.9
2.15
±0.44
13.6
±4.435 2.16
±0.416 3.13
±1.56 1.6
pH 7.2
±0.24
7.5
±0.18 7.4
±0.25
7.4
±0.13 7.4
±0.15 7.4
±0.32 7.3
±0.25 7.5
±0.165 7.3
±0.164 7.03
±0.17 6.9
Generally, regional water pH in most rivers and stream sampled is neutral to alkaline and
varies from 6.8 to 8.5, (Fig 9a). Streams B15 with an average pH of 7.03 is the lowest in the
drainage basin while streams B2 and B7 with an average pH of 7.5 are the highest (Table: 5).
24 Relatively Low pH values were mostly recorded during the 1
stspring flood maximum flow, summer and sometimes during the 2
ndspring flood recession (Fig. 9a). These seasons coincide with periods of snow melting and decomposition of organic matter. These are undoubtedly the main processes regulating water pH. Stream B7 flows over the Avan ore body, its high pH is due to the weathering and buffering effects of carbonates especially calcite veins associated with ore body and supracrustal rocks (Barsele Technical Report 2006, Bark 2007). Besides its relatively high pH, Stream B7 equally has elevated concentrations of Ca, Mg, SO
42-and elevated conductivity levels which are about 2.5 to about 6.5 times greater than in all the other streams. The concentration of Ca is generally higher than Mg in all the streams and suggests that the surrounding bedrocks and hence till are enriched in Ca bearing minerals like plagioclase and calcite which is generally depleted in Mg. Just like pH, the lowest concentration levels of Ca and Mg were equally recorded during the 1st spring flood maximum flow, summer and to a lesser extend 2
ndspring flood recession while elevated concentrations were recorded during base flow.
Alkalinity varies from 4 HCO
3/l in stream B6 and B15 to 85 HCO
3/l in Stream B7. Stream 7 has the highest buffering capacity which is about three to seven times higher compared to other streams in the drainage basin, (Figure 9b). Such a high buffering capacity is due to the weathering of calcite veins associated with the ore body. Streams B6, B8 and B15 have the lowest buffering capacity in the drainage and possibly reflect variation in rock type or the absences of carbonates veins in bedrock.
Generally, sulphate concentrations in all streams sampled were greater than the average concentration in the Kalix River and could be explained by the rustiness of till in some location; mainly due to the weathering of fragments of pyrite and sulphide minerals or the occurrence of clay silt as the dominant fine fraction. An anomalous sulphate concentration (13.23mg/l) in Stream B7 is due its proximity in to the Avan ore body compared to other streams in the drainage basin. This ore body is hosted by a granodiorite formation and is also bounded meta mafic volcanic (Fig 2.) which is an indication that fine till which is normally the weathering product of such rocks should be enriched in clastic sulphide minerals and dark clayey. Thus, these sulphides are continuously weathered, oxidized and leached into Stream B7. Very low sulphate concentration in Stream B8 could be attributed to its location in the drainage basin. Compared to other streams, Stream B8 is located downs stream and it is the furthest from Stream B7 and B4 which are closest to the main ore bodies. Distance from the main ore body also implies that dilution by barren streams should be strong enough to reduce its persistence in the drainage basin. Dilution by barren water is further supported by the fact that the lowest sulphate concentrations were recorded during summer and spring flood which coincide with the melting of snow.
Conductivity varies from 2µS/m in stream B6 to 18µS/m in stream B7. The median
conductivity in stream B7 (15.5 µS/m) is about three to five times higher compared to other
streams in the drainage basin, (Figure 9c). Stream B6, B8 and B15 have the lowest
conductivity levels which is an indication that calcite vein may not be associated with rocks
bordering these streams. It is worth stating that the concentration trend for Ca and Mg
25 correlates with conductivity, (Table 5) and possibly suggests that Ca and Mg together with sulphate and alkalinity are the main factors controlling the conductivity of these streams.
The concentration of Fe in all streams varies from 0mg/l in streams B2, B3y, B3b and B4 to 0.3mg/l in stream B5, (Figure 9d) and are consistently low compared to the Kalix River with an average concentration 0.492mg/l, (Table: 5). This deviation is mainly due to occurrence of mires and swamps concentrating Fe around the Kalix river. Though low, relatively high Fe concentration was observed during summer, 1
stspring flood maximum flow and in some cases during the 2nd spring flood recession indicating the influence of a slight change in pH on its mobility. Besides changes in pH, relatively high Fe concentration could also be due to the release of high Fe concentration at the snow-soil inter face during the late stage of snowmelt. Stream B5 with an average concentration of 0.137mg/l is most elevated in Fe possibly because of the oxidation of arsenopyrite and pyrrohtite associated Norra ore body.
Relative high Fe concentration could also be associated to the dominance of mafic volcanic rocks around Stream B5 (fig 2). The influence of these rock is reflected in till and soil which are dominantly made up of dark clays , or silty clays possibly containing fragments of Fe- bearing minerals like olivine, pyroxenes amphiboles and biotite minerals. However, it must be stressed that the low Fe concentration observed in some streams could be due to the fact that in such surface waters with abundant oxygen (high Eh) and with a neutral to alkaline pH, Fe is insoluble but exist mainly as Fe- oxyhydroxide which has a general tendency to form precipitation barriers for most heavy metal (Rose et al.; 1979). This together with the near neutral pH of streams in the drainage basin possibly explains the relatively low concentration of Pb, Ni and Cu in most streams.
Generally, elevated concentrations of As, Cu Ni Pb and Zn in all the streams sampled somewhat correlate with a relatively low seasonal pH values, base flow and to a lesser extend with spring flood seasons, and demonstrate the role of a slight drop in pH in the remobilization of these elements. In most of the unmineralized streams and rivers, the metal concentration and mobility decrease in the order Pb<Ni<As<Cu<Zn (Fig 10a and 10b), which is just typical of most surface waters mainly because these metal form free aqueous species and complexes with SO
42-, (OH)
-1and CO
32-at different pH (Appelo and Postma,
2005 and Hem, 1976). However, in mineralized streams like stream B7, B4 and B2, their
mobility trends decrease in the order Pb<Ni<Cu<Zn<As, or Pb<Ni=Cu<As<Zn (Fig 10c and
10d) and reflect the influence of ore bodies or at least possible ore bodies, mineralized till and
to a lesser extent pH, complexing ligands and sorption processes on their mobility. It is
equally important to consider the fact that As forms mobile complex anions which could
inhibit its adsorption on precipitation barriers and therefore is mobile even at neutral pH,
(Morel and Hering, 1993). Dark clays containing fragments of pyrite, sulphides minerals,
biotite and granodiorite should possibly be the dominant till type around these streams, (Fig 2
and Fig 7b). Thus, the fine fractions in till exposes a large surface area and high cation
exchange capacity for the adsorption of arsenic and other trace metals. It can be said that As
mainly as arsenopyrite is continuously being oxidized and leached into sediments and hence
surface waters (Smelly and Kinniburgh, 2002). It is worth mentioning that the concentration
of As in Stream B7 is 3.8 to about 36 times greater than the average concentration in most
streams sampled and equally correlates with high sulphate, Ca, Mg and conductivity.
26 Stream B4 is closer or flows over the Norra ore body (Fig 3) and its As level is five times greater than in Stream B5 which flows close to it. Both of streams constitute the main inlets of Lake Skirträsket. (Fig 5 and table 5). Such variations could be traced from the difference in rock type and hence till type. It can be seen from (Fig 2) that metasedimentary rocks and hence sandy silts with fragments of granite, quartz, seem to be dominant around Stream B5 unlike mafic volcanic rocks with fine till around Stream B4. The flow directions or sources of both streams should equally be considered, (Fig 5) because the nature of the relief around these streams could greatly influence which direction As leached from the Norra ore body or from mechanically dispersed till will flow. Thus, As in this case serves as a pathfinder for Au, and its low concentration in stream B5 possibly delineates the upper limit of the Norra ore body. Just like Stream B4 and Stream B5, Stream B1 which is closer to Stream B2 is relatively depleted in As and could be explained by fact that Stream B2 flows from the southeast of Lake Skirträsket and is bounded by mafic intrusion and possibly till rich in fragments of mafic volcanic, biotite, massive sulphides and thin covers of soils. Stream B1 constitute the main outlet of Lake Skirträsket is mostly surrounded by till containing fragments of granite, sand, and quartz which generally have a low heavy metal content, (Fig 5). In the case of B3y and B3b (lake Skirträsket) the near uniform concentration of As reflects homogenous mixing of barren and mineralized water flowing into Lake Skirträsket.
Stream B15 is located upstream compared to most streams in the drainage basin and appears to be the furthest from Stream B7 and Stream B4 which are the closest to the ore body. Thus, its location together with its surrounding rocks, mainly metasedimentary and metagranitoid (Fig 3) accounts for its low As concentration. River B6 and B8 are the least polluted with As and their average As concentration near equals the average As concentration in the Kalix River, (table 5). River B8 is located downstream of B6, and its low As concentration could mainly be attributed to dilution effect. River B8 is mainly surrounded by glaciofluivial sediments, granites, sandy silt and metasedimentary rocks which are known to have very low As concentration. It is equally important to consider the fact that generally in such oxygenated surface waters with high Eh values, As could equally exist as H
2AsO
4-and could be adsorbed onto Fe (OH)
3at neutral pH (Moore and Ramamoothy 1984). This could account for low As levels in some of the Streams. Distance from the ore body is equally worth considering because this could account for the progressive decay in As concentration and further explains the relatively low As level observed in some streams.
Though depleted in As, Stream B15 has the most elevated levels of Zn, about 7.5 times greater than the average concentration in the Kalix River and 5.6 times greater than average concentration in stream B2 with the lowest concentration. Such elevated levels could be more related to upstream enrichment. It is equally important to consider its relatively low pH (pH 7.03, table 5) which is somewhat low enough to remobilize Zn. The influence of pH is further illustrated by the fact that the concentration of Cu and Pb are low or near background concentration. It could as well be that Stream B15 is being fed by streams with elevated concentration of Zn.
The concentration of Pb varies from 0 to 0.0068mg/l, (Figure 8i). Generally, its concentration
in all streams sampled is low and could be attributed to the relatively high pH of streams in
the drainage basin. Stream B6 and B3b are most elevated in Pb. Relatively elevated levels in
Stream B6 concentration could further be attributed to Pb sulphide mineralization in addition
to the fact that K-feldspars and micas as common minerals in metasedimentary rocks could
27 equally be enriched in Pb. It is equally important to consider the fact glaciofluivial and quaternary deposits enriched in these metals could mainly be derived or could be of a
complex origin (fig 2.4a) The concentration of Cu varies from 0.0002 to 0.009mg/l. Its average concentration is highest
Stream B3y and lowest in Stream B2, (Table5 and Figure 8g). All other streams have near average concentration or twice the average concentration in the Kalix River and could still be attributed to the relatively high pH of streams in the drainage basin together with sorption on to Fe- oxyhydroxide
Nickel concentration varies from 0 to 0.009 mg/l. Its average concentration is highest in Stream B3y, B3b and B8, (Figure 8h and Table 5). Its concentration in other streams is two to four times greater than the average concentration in the Kalix River
Figure: 9a pH variation in streams
Figure 9b Variation of alkalinity in stream 6.4
6.6 6.8 7 7.2 7.4 7.6 7.8 8
B1 B2 B3y B3b B4 B5 B6 B7 B8 B15
pH
Streams pH
0 10 20 30 40 50 60 70 80 90
B1 B2 B3Y B3b B4 B5 B6 B7 B8 B15
Alkalinity ( HCO3/l)
Streams Alkalinity
28
Figure: 9c Variation conductivity in stream B5Figure 9d Variation of Fe in streams
Figure 9e Variation of sulphate concentration in stream 1
3 5 7 9 11 13 15 17 19
B1 B2 B3Y B3B B4 B5 B6 B7 B8 B15
Conductivity (mS/m
Streams
Conductivity
-0.03 0.02 0.07 0.12 0.17 0.22 0.27 0.32
B1 B2 B3Y B3B B4 B5 B6 B7 B8 B15
Fe (mg/l)
Streams Fe
-0.2 4.8 9.8 14.8 19.8 24.8 29.8
B1 B2 B3Y B3b B4 B5 B6 B7 B8 B15
Sulphate (mg/l).
Streams Sulfate
29
Figure 9f Variation of As concentration in streamsFigure 8gVariation of Cu concentration in streams
Figure 9h Variation of Ni in streams 0
0.005 0.01 0.015 0.02 0.025 0.03
B1 B2 B3Y B3b B4 B5 B6 B7 B8 B15
As (mg/l)
Streams AS
0 0.002 0.004 0.006 0.008 0.01
B1 B2 B3Y B3B B4 B5 B6 B7 B8 B15
Cu (mg/l)
Streams Cu
-0.001 0 0.001 0.002 0.003 0.004 0.005 0.006 0.007 0.008 0.009 0.01
B1 B2 B3y B3b B4 B5 B6 B7 B8 B15
Ni (mg/l)
Streams Ni
30
Figure 9i Variation of Pb in streamsFigure 9j Variation of Zn in streams
Figure10a: Variation of trace metals with time in mineralized stream e.g. 1 Stream B15. Trend is typical of streams with relatively low As concentration. (Mobility is of the order Zn>Cu>As>Pb)
0 0.001 0.002 0.003 0.004 0.005 0.006 0.007
B1 B2 B3y B3b B4 B5 B6 B7 B8 B15
Pb (mg/l)
Streams Pb
-0.005 0 0.005 0.01 0.015 0.02 0.025 0.03
B1 B2 B3y B3b B4 B5 B6 B7 B8 B15
Zn (mg/l)
Streams Zn
0 0.001 0.002 0.003 0.004 0.005 0.006 0.007 0.008 0.009
Metal content (mg/l)
Dates Stream B15
Zn Cu Pb As Ni
31
Figure 10b Variation of trace metals with time in unmineralized stream e.g. 2, Stream B1. Trend is typical of streams with relatively low As concentration. Mobility also of the order Zn>Cu>As>Pb)Figure 10c Variation of trace metals with time in a typically mineralized stream e.g. 1, Stream B7. Trend is common for streams with relatively high As concentration. Mobility is of the order As>Zn>Cu>Pb
Figure 10d Variation of trace metals with time in mineralized streams e.g. 2, Stream B7. Trend is common for streams with relatively high As concentration. Mobility is of the order As>Zn>Cu>Pb
0 0.001 0.002 0.003 0.004 0.005 0.006 0.007 0.008 0.009 0.01
Metal content (mg/l)
Dates
Stream B1
Zn Cu Pb As Ni
0 0.005 0.01 0.015 0.02 0.025 0.03
Metal contant(µg/l)
Dates Stream B7
Zn Cu Pb As Ni
0 0.001 0.002 0.003 0.004 0.005 0.006 0.007 0.008
Metal contant(µg/l)
Dates Stream B4
Zn Cu Pb As Ni
32 Data from the Kalix River serve as a good reference to assess pollution because its metal concentration going by SEPA standards falls mostly in class 1or 2. In Stream B7 As (18µg/l, SEPA class4, table 6) is the most polluted in the drainage basin and shows increasing risk for biological activities. All the other streams have As concentration belonging to class 2 or class 1 and can thus have little or no effect on biological activities. These observations clearly support earlier investigation by Pelagia Environmental AB. River B6, As (1.8µg/l, SEPA class1) and River B8, As (1.6µg/l SEPA, class 1) are unpolluted or have a near background concentration
Generally Cu and Ni concentration in most streams can be grouped in class 2 and rarely in class 1. They are the most elevated in the drainage basin after As. Thus, Cu and Ni concentration in these streams could have little effect on aquatic species. This observation equally supports earlier investigation by Pelagia Environmental AB.
Zinc, Pb, Cd and Mo can be grouped in class 1. These metals have little or no effect on biological systems. Generally, Stream, B2 has the lowest base metal concentration, (SEPA class1or 2, Table 5). It is the least polluted with base metals.
Table 6: Classification of metal content in stream and rivers around Barsele. Classification is based on standards set by the Swedish environmental Protection Agency (SEPA).
Metal
Streams / Rivers Class
B1 B2 B3y B3b B4 B5 B6 B7 B8 B15
As 2 2 2 2 2 2 1 4 1 2 1
Cu 2 2 2 2 2 2 2 2 2 2 2
Ni 2 1 2 2 1 1 2 2 2 2 3
Pb 1 1 1 2 1 1 2 1 1 1 4
Zn 1 1 1 or 2 1 1 1 1 1 1 2 5
4.4 Lake water
The concentration of As, S and Zn are marked by a homogenous decrease from surface down
to about 6m in the water column at station A, but not at station B as the concentration of Zn
rather increases within this depth interval. From 6m to about 15m, the concentration of As,
Cu S remain constant whereas the concentration of Zn steadily decrease to a depth of about
12m and then stays constant to a depth of 15m at station B. However, at station A its
concentration steadily increases to a depth of 11cm and then steadily decreases again to a
depth of 15 and becomes stable below this depth (fig 9c & fig 9d). Judging from the lake
water profile of Cu, Mg, Ca, As, Fe, Mn and S it can be said that lake water is somewhat well
mixed. The concentration of Fe and Mn are almost uniform at both sampling stations (fig 9e
and 9f) and points to the near stable oxygenated condition in the water column. However,
slide variations in the concentration of some these elements e.g. Ca, (fig 9a and 9b) from the
surface to about 5m in the water column and could mainly be due to slide differences in water
temperature and oxygen concentration. The concentration of Pb at both sampling stations was
33 very low or below detection possibly because of the high water pH precipitating Pb compared to other heavy metal.
Figure 9a Variation of Ca and Mg in lake water with depth, station A
Figure 9b Variation of Ca and Mg in lake with depth, station B
Figure 9c variation of Sulphur and trace metal with depth in lake water, station A 0
2 4 6 8 10 12 14 16 18
0 2 4 6 8 10 12
Depth (m)
Element (mg/l)
Ca and Mg (station A)
Ca Mg
0 2 4 6 8 10 12 14 16 18 20
0 2 4 6 8 10 12
Depth (m)
Element(mg/l)
Ca and Mg (station B)
Ca Mg
0 2 4 6 8 10 12 14 16 18
0 0.5 1 1.5 2 2.5
Depth (m)
Metals(µg/l) except S (mg/l)
Metal conc (station A)
AS Cu Zn S
34
Figure 9d variation of Sulphur and base metal with depth in lake water, station BFigure 9e variation of Fe and Mn in lake water with depth, station A
Figure 9f variation of Fe and Mn in lake water with depth, station B 0
2 4 6 8 10 12 14 16 18 20
0 0.5 1 1.5 2 2.5
Depth(m)
Element conc (µg/l) except S (mg/l)
Element conc. (station B)
As S Zn Cu Ni
0 2 4 6 8 10 12 14 16 18
0.0001 0.001 0.01 0.1 1
Depth (m)
Fe (mg/l) , Mn (µg/l)
Fe and Mn (station A)
Fe Mn
0 2 4 6 8 10 12 14 16 18 20
0.0001 0.001 0.01 0.1 1
Depth (m)
Fe(mg/l) , Mn (µg/l)
Fe and Mn (station B)
Fe Mn
