environmental chemistry of copper in torch lake, michigan

E N V I R O N M E N T A L C H E M I S T R Y OF C O P P E R

IN T O R C H L A K E , M I C H I G A N

JOSE M A N U E L LOPEZ and G. FRED LEE

Center for Environmental Studies, University of Texas, Dallas, Richardson, TX 75080, U.S.A.

"(Received 7 January, 1976; revised 25 January, 1977)

Abstract. A study of Keweenaw Peninsula and adjacent Lake Superior waters was undertaken to evaluate the significance of Cu tailings deposits as a potential source of Cu and the controlling Cu concentrations in these waters. Metal concentrations were determined by atomic absorption techniques. Copper concentrations, especially in areas affected by discharge of large quantities of Cu mine tailings for over 100 yr, were relatively high. Concentrations of apparently dissolved Cu of up to 100 ~tg 1 -~ were found in Torch Lake in the summer of 1972. These high Cu levels may be partially explained by industrial spills of copper wastes that occurred around that time. However, relatively high concentrations appeared to persist in Torch Lake waters throughout the annual cycle. The vast quantities of crushed Cu-bearing ore that comprise the bottom sediments and line the shores show a Cu content ranging from 1300 to 3800 mg 1-1. These materials act as a reservoir of Cu providing a continual supply of Cu to these waters. Laboratory leaching studies of these materials demonstrate that they can release potentially significant amounts of Cu when suspended in lake water.

Although the Cu levels found in Torch Lake exceed US EPA-recommended maximum allowable levels for these waters, there are reports of substantial fish and algal populations. Equilibrium calculations indicate the predominance of various soluble Cu species in the following order of abundance: Cu(OH) + > Cu ++ > CuCO 3. However, Cu in these waters may not be controlled by solubility relationships of Cu compounds but rather by sorption onto surfaces of Fe and Mg hydrous oxides resulting in the occurrence of Cu in relatively non-toxic forms. Any additional mining or reclamation operations pose a potential hazard to aquatic ecosystems because of the wide-spread Cu contamination that already exists in the waters of this area.

1. Previous Studies on Torch Lake

Copper mining activities over the past hundred years in the Keweenaw Peninsula, Michigan, have resulted in large quantities of Cu mine tailings being discharged into lakes and streams, some of which are tributary to Lake Superior. Nussmann (1965) attributed Cu enrichment of the surface sediments of Keweenaw Bay an d adjacent areas to discharges of tailings and to stream transport of Cu-rich sediments from the peninsula. The Keweenaw Waterway, which connects Torch and Portage Lakes with Lake Superior waters on the west and Keweenaw Bay on the east, drains a large area potentially affected by Cu mine tailings discharges (Figure 1). Brandt and Leddy (1973) and Wright et aL (1973) have reported Cu concentrations in the waters of this area ranging from 0.5 gg 1-1 in Keweenaw Bay to 100 ~tg 1-1 in Torch Lake during the summer of 1972. The high Cu content of Torch Lake waters was in part attributed to industrial spills of cupric ammonium carbonate, which occurred in late fall 1971 and early summer 1972 (Wright et al., 1973).

Tailings deposits in Torch Lake and other waters of this area contain Cu in excess of 0.1%. In fact, mining of these deposits may become economically feasible in the near

Water, Air, and Soil Pollution 8 (1977) 373-385. All Rights Reserved Copyright © 1977 by D. Reidel Publishing Company, Dordrecht-Holland

374 JOSE MANUEL LOPEZ AND G. FRED LEE

Loke Superior

L. GIo

32 ~L4Medora

Eogle River Svstem---i ~ 5 26 35

ley

Bell,

16

ngonese

22, 23, 24 -

Torch Loke Keweenow Boy

t dg I

Fig. 1. Sampling stations for the Keweenaw peninsula area of Lake Superior.

future. Available information suggests a potential hazard to aquatic ecosystems associated with any additional mining activities because of the widespread Cu con-

tamination that already exists in area waters. This study focuses on the aqueous environmental chemistry of Cu in Torch Lake

and selected waters of the Keweenaw Peninsula and Lake Superior. The objective is to evaluate the significance of Cu tailings deposits as a potential source of Cu to the water and the factors controlling Cu concentration in these waters.

Torch Lake, located in Houghton, Michigan, has an area of 1,100ha and a maximum depth of 31 m. An amount of water equivalent to the lake volume enters the lake annually. The watershed is mostly covered with hard woods and farming activity is limited. The lake is tributary to Portage Lake which is tributary to Lake Superior (Figure 1). According to Wright et al. (1973), during the period of 1946-1970, an estimated 20% of the Lake's volume was filled with Cu mine tailings with more than 0.1% Cu content. During the latter part of this period, previously discharged tailings were reclaimed using an ammonia leach and then again discharged into the Lake.

The bottom sediments of the Lake, primarily derived from tailings, consist of a very fine material of little organic content. The benthic fauna is extremely poor. However, Wright et al. (1973) have reported phytoplankton populations in the range of 200 to 6000 cells ml -a based on a limited number of surface samples. In addition, substantial populations of fish were observed in Torch Lake by Fetterolf (1972). Since Cu con-

ENVIRONMENTAL CHEMISTRY OF COPPER IN TORCH LAKE, MICHIGAN 375

centrations in excess of those known to be deleterious to aquatic life have been found in the Lake, these occurrences raise questions about the forms of Cu present in the Lake and the reliability of previously collected data.

The toxicity of Cu to aquatic organisms can vary significantly with the chemical species of the metal and the physical and chemical characteristics of the water, such as temperature, pH, turbidity, hardness, and alkalinity. Lethal Cu concentrations for fish and aquatic invertebrates range from 0.015 to 3.0 mg 1-1 according to McKee and Wolf (1963). Further, for many trace metals chronic sublethal effects occur at concentrations 10 to 1000 times less than those causing acute lethal effects on the same organisms. In studies using Lake Superior water (45 mg 1-1 hardness as CaCO3), McKim and Benoit (1971) determined that 9.5 gg Cu1-1 is the maximum acceptable level at which no significant effect would be expected on survival, growth or reproduction of brook trout.

Copper salts can show marked toxicity to aquatic plant life as well. For example, a significant decrease in the growth of the green alga ChloreIla pyrenoidosa at a concentration of 1 ~tg 1-1 of Cu when the Fe content was 6 ~g 1-1 was shown by Steeman- Nielsen and Kamp-Nielsen (1970). In fact, Cu salts have been widely used for aquatic plant growth control.

The Quality Criteria for Water (US E.P.A., 1973) recommend a maximum acceptable Cu concentration in water of 1/10 of the 96-h LCs0 value using the water in question and the most sensitive and important local organism. This would place maximum acceptable concentrations of Cu for Torch Lake in the range of 6 to 30 ~tg 1-1.

2. Methods and Materials

Samples of water and sediments were obtained during a reconnaissance of Keweenaw Peninsula and adjacent Lake Superior in mid-June 1972. Sampling locations are shown in Figures 1 and 2. Subsequent sampling programs through April 1973 focused on Torch Lake, where high Cu concentrations had been found (Figure 2).

At each station, dissolved 02 and temperature profiles were determined using a YSI Model 54 Dissolved Oxygen Meter. A Van Dorn water sampler was used and the water placed on acid-washed polyethylene bottles. Shortly after collection of the samples, pH, specific conductance, chloride, and alkalinity determinations were made following procedures outlined in Standard Methods (APHA et al., 1971).

Vertical distribution of Cu, Zn, Fe, Cd, and Ni was determined for each sampling station. Portions of the water were filtered through 0.45 gm pore size membrane filters (MiUipore Corp.). Materials passing through the filter were considered to be dissolved. Total concentrations were determined from unfiltered samples. Trace metal analyses were performed on a Perkin-Elmer Model 303 Atomic Absorption Spectrophotometer (AAS) after concentration by the APDC-MIBK extraction method (Lopez, 1973). Detection limits for this method were 1.0 gg 1-1 for Cu, Ni, and Zn; 5.0 ~ag 1-1 for Fe and Mn; and 0.5 gg 1-1 for Cd.

Metal composition of the sediments was also determined. Grab samples of the


A

D 7j

t

/ Fig. 2. Sampl ing s ta t ions for Torch Lake.

sediments, collected with Ponar or Ekman dredges, were placed in plastic bags. A

strong acid digestion ( H F - - H C 1 0 4 - H N O 3 ) was used to dissolve the sediments, and metal analyses were performed by direct aspiration of the aqueous solution on AAS. Details of the analytical procedure can be found in Lopez (1973).

Sediment release studies were conducted to examine the likelihood of Cu release from Torch Lake sediments and tailings deposits on the shores. Weighed portions of the fresh, wet sediments were put into 19-1 carboys containing 141 of water. The resulting suspensions contained from 0.7 to 1.2% sediments. Leaching tests on the tailings and sediments were conducted in distilled water and in Torch Lake water under aerated and anoxic conditions. Compressed air or N 2 gas was bubbled through the suspensions. The gas flow was sufficient to maintain suspension of the substrate at all times. Samples of the suspensions were siphoned from mid-depth in order to maintain essentially the same water-to-substrate ratio throughout the experiment. The samples were centrifuged to remove the coarser material and then filtered through 0.45/am pore size membrane filters. The filtrates were analyzed for metals on AAS using the APDC-MIBK extraction method.


3. Results

A s u r v e y o f K e w e e n a w B a y a n d P e n i n s u l a a r ea w a t e r s d u r i n g J u n e 1 5 - 1 8 , 1972,

r evea led t h a t c o n c e n t r a t i o n s o f me t a l s , e spec ia l ly C u , were h ighe r in p o r t i o n s o f the

Eag le R ive r a n d T o r c h L a k e t h a n in o the r w a t e r s o f the a rea (Tab le I). In the s t u d y

area , t h e s e t w o bod ie s o f w a t e r are a m o n g t h o s e m o s t a f fec ted by C u m i n e ta i l ings

d i s c h a r g e s . Tab l e II s h o w s c o n c e n t r a t i o n s o f C u , Fe , a n d Z n in fil tered a nd unf i l te red

w a t e r s a m p l e s col lec ted f r o m v a r i o u s l oca t i ons a n d d e p t h s in T o r c h La ke . C a d m i u m

a n d Ni were ba re ly de t ec t ab l e in the a r ea w a t e r s su rve ye d .

TABLE I

Average total concentrations of various constituents in waters of the Keweenaw Peninsula area found during June 15-18, 1972

Specific Alkalinity conductance Cu Fe Zn

Location pH mg 1-1 CaCO 3 umhos cm -~ at 20°C gg 1-1 gg 1-1 gg 1-1

Torch Lake 7.8 38 180 81 62 8.0 Keweenaw Bay 7.8 40 86 2.5 4.6 3.5 Lake Lac La Belle 7.4 17 46 4.8 16.5 3.8 Portage Lake 7.7 30 86 10.0 15.0 3.0 Eagle River,

West Branch 8.1 67 126 69 435 4.0 Eagle River 8.0 57 120 74 230 1.7 Jacobs Creek 8.2 95 180 5.3 217 2.0 Owl Creek 8.2 95 174 9.6 320 2.0 Eliza Creek 7.7 47 104 2.0 92 7.0 Lake Bailey 7.9 41 90 2.3 89 12.5 Lake Glazon 8.0 55 110 2.5 130 2.5 Lake Manganese 7.7 38 78 4.2 100 0.5 Lake Medora 7.5 22 - - 0.8 88 7.0

TABLE II

Metal concentrations (gg 1-1) found in Torch Lake water on June 15, 1972

Cu Fe Zn Depth Sample No. and location (m) N.F. F. N.F. F. N.F. F.

1 - Torch Lake, Outlet 17 104 79 63 15 18.5 15.0 2 - Torch Lake, Lower 14.5 90 76 55 25 11.0 13.5 3 - Torch Lake, Lower 6 90 76 60 27 9.5 8.5 4 - Torch Lake, South 3 89 73 57 30 8.0 4.5 5 - Torch Lake, West 27 117 100 60 28 11.0 9.5 6 - Torch Lake, North 12 100 80 65 31 5.5 6.0 7 - Torch Lake, East 9 89 83 55 33 5.5 7.5

*36 - Torch Lake, SW Shore 0 48 - - 48 - - 3.0 - - *37 -To rch Lake, W Shore 0 82 - - 100 - - 4.5 - - *38 - Torch Lake, N Shore 0 53 - - 60 - - 4.0 - -

N.F. - Not filtered. F. - Filtered through 0.45 lam pore size membrane filters. * - Samples 36, 37, and 38 obtained on June 18, 1972.


A p p a r e n t l y d i s so lved C u in T o r c h L a k e r a n g e d f r o m u p w a r d s o f 70 ~tg 1-1 to

100 lag i -1 a n d i n c r e a s e d w i th dep th . C o p p e r c o n c e n t r a t i o n s in t h e unf i l te red s a m p l e s

were as h igh as 1 17 ~tg 1-1. I r o n c o n t e n t in the unf i l t e red s a m p l e s w a s a p p r o x i m a t e l y

60 rtg 1-1, o f w h i c h a b o u t h a l f or less p a s s e d the 0 .45 ~tm po re size filters. Po t en t i a l l y

s ign i f ican t a m o u n t s o f Z n were a lso f o u n d in these wa te r s .

3.t. HEAVY METALS IN SEDIMENTS

T a b l e I l l p r e s e n t s me ta l c o m p o s i t i o n o f b o t t o m s e d i m e n t s a n d ta i l ings depos i t s

t h r o u g h o u t K e w e e n a w P e n i n s u l a a n d a d j a c e n t L a k e Supe r io r wa te r s . I r o n w as t h e

m o s t a b u n d a n t m e t a l in all l o c a t i o n s s amp led . H i g h e r c o n t e n t s o f Cu were f o u n d in

s e d i m e n t s o f t h o s e w a t e r s a f fec ted b y C u m i n e ta i l ings d i s c h a r g e s t h a n in w a t e r s n o t

a f fec ted by the se act ivi t ies . T h e b o t t o m s e d i m e n t s o f T o r c h L a k e ( s amp le s 1 - 7 ) h a d a

C u c o n t e n t c o m p a r a b l e to t h o s e o f t he ta i l ings depos i t s o n the s h o r e s ( s a m p l e s 3 6 - 3 8 ) .

T h e L a k e s e d i m e n t s r a n g e d f r o m 0 .13 to 0 . 2 6 % C u w h e r e a s ta i l ings s a m p l e s r a n g e d

f r o m 0 .13 to 0 . 2 6 % Cu. S imi la r C u c o n t e n t w a s f o u n d in s e d i m e n t s f r o m the p o r t i o n s

o f P o r t a g e L a k e a f fec ted b y ta i l ings d i s cha rges . Samp l e s f r o m W e s t B r a n c h Eagle

R ive r s h o w e d 0 . 5 9 % Cu , whi le C e n t r a l , a ta i l ings d u m p i n g a r e a in t h e Eag le River ,

s h o w e d 0 . 7 6 % Cu .

Analysis of sediments from selected sites

TABLE III

of the Keweenaw peninsula a dry weight basis

area. Concentrations are expressed on

Cu Fe Zn Ni Cd Sample No. mg kg -1 g kg -~ mg kg 4 mg kg -~ mg kg -~

I - Torch Lake (TL Outlet 1610 119.4 250 165 2.8 2 - TL, Lower 1650 152.6 240 150 2.5 3 - TL, Lower 3060 156.3 225 170 2.3 4 - TL, South 1310 154.4 315 155 2.3 5 - TL, West 1875 80.6 178 130 2.0 6 - TL, North 3860 147.5 345 198 4.3 7 - TL, East 1350 145.6 260 205 2.5 8 - Keweenaw Bay (KB) 510 95.6 153 90 3.3

1 0 - KB 580 11.6 23 6.0 1.3 12 - KB 300 12.0 17.5 8.5 1.6 13 - KB, OffGay 1950 97.5 123 45 3.0 16 - KB 200 21.2 41 16 1.8 19 - KB 80 8.4 12 5.0 1.4 20 - KB, at Portage canal 300 17.8 34.5 20 1.7 21 - KB, at Portage canal 680 25.8 59 24 2.1 22 - Portage Lake

(PL) Lower 1380 34.8 71 32 1.9 23 - PL, Torch Bay 1100 107.5 238 165 4.4 24 - PL, North 1450 98.8 125 73 3.6 25 - Eagle River, West Branch 5920 88.1 105 155 4.4 35 - Eagle River, at Central 7650 105.0 115 160 3.5 36 - TL, Shore tailings 2650 95.0 135 185 4.3 37 - TL, Shore tailings 1290 90.0 135 50 3.4 38 - TL, Shore tailings 1275 45.0 105 60 3.1

Note: TL refers to Torch Lake, KB refers to Keweenaw Bay, PL refers to Portage Lake.


The lowest metal concentrations were found in the sediments of Lake Superior. Copper in these sediments northward of Portage Entry decreased from 0.008 to 0.07%; however, 0.2% Cu was found near Gay, a tailings discharge site.

Lesser concentrations of other metals were found. Cadmium in the study area sediments was below 0.0004%. The Zn and Ni composition of Torch Lake sediments was substantially higher than elsewhere in the peninsula, ranging from 0.02 to 0.03% Zn and 0.01 to 0.02% Ni.

3.2. METALS IN WATER

On August 23, 1972, Torch Lake was thermally stratified, the middle point of the metalimnion being at 9 m of depth. Metal analysis of the unfiltered water showed increasing metals concentration with depth (Figure 3). Copper concentration was 25 ~tg 1 -x at 4 m and 87 lag 1 -x at 31 m (bottom). Throughout the water column, Fe was more abundant than Cu, varying from 38 to 116 ~tg1-1 in the interval 4 to 31 m. Relatively high concentrations of Mn, increasing with depth from 8 to 132 lag 1-1, were also measured. Zinc concentrations ranged from less-than-detectable (1 lag1-1) to 6 lag 1 -l. Nickel and Cd were present at less than 1 lag 1-1. These water samples were not filtered and substantial portions of the measured concentrations presumably represent particulate metal, especially in the case of Fe and Mn. It is of interest to note that the vertical distribution of the various metals follows similar patterns.

During fall overturn, the waters of Torch Lake were completely mixed. The Cu distribution throughout the water column then was a uniform 60 lag 1-1 apparently dissolved Cu (Wright et aL, 1973).

•}i I l I I i I l I i I g I I

? z L o z .

C~20 _

2 4 _

5 2 0 20 40 60 80 I O0 120 140

CONCENTRATION /a.g / I

Fig. 3. Vertical distribution of various heavy metals for Station A, Torch Lake, on August 23, 1972.

380

Fig. 4.

JOSE MANUEL LOPEZ AND G. FRED LEE

g

29

0 4 8 12. 16 20 24 28 52 36 40

CONCENTRATION ~ g / l

Vertical distribution of Cu, Fe, and Zn for Station A, Torch Lake, on January 26, 1973.

Figure 4 represents the vertical distribution of Cu, Fe, and Zn under the ice cover on January 26, 1973. Copper and Fe exhibited similar vertical distribution patterns with concentration increasing slightly with depth, and decreasing again towards the bottom meter. Copper ranged from 25 gg 1-1 to 36 gg 1-1 and Fe from 18 gg 1-1 to 33 ~tg 1-1 for

both Cu and Fe. Minimum values occurred at 5 m and maximum values at 27 m. Zinc concentration averaged about 3 ~tg 1-1 throughou t most of the water column, although

a high value of 18 gg 1-1 Zn was observed at 1 m depth. Shortly after ice was out (April 27, 1973), the lake was well mixed. At this time Zn

concentrations were mostly below the detection limit. Average concentrations of 45 gg 1-1 dissolved Cu and 55 ~tg 1-1 dissolved Fe were almost uniform throughout the lake. Average concentrations in the unfiltered samples were 48 ~tg 1-1 Cu and 85 gg 1-1 Fe (Figure 5). The increased metal content of the waters at that time was probably the

result of metal-enriched high water inflows after spring thaw.

7. Copper Release from Sediment and Tailings

A series of tests was run to determine whether Cu could be released from the tailings present on the shores of Torch Lake. The conditions of the test included the use of Torch Lake water or distilled water under oxic and anoxic situations. Table IV lists the conditions of each experiment and the corresponding rate of Cu release. The data obtained are presented in Figures 6 and 7. Approximately 1 gg 1-1 of Cu was released per day in Torch Lake water suspensions of Torch Lake tailings and sediment that were treated with air or N 2 gas. Some of the carboys showed considerable scatter from day to day. The rate of Cu release reported above are eyeball estimates of overall trends


I

5

9 A

E 13

I I - - 17 Q.. W a 21

2 5

Fig. 5.

29

40

Dissolved

4-2 44

COPPER

Total

46 48 50

/.Lg/I

I

5

9

E 13 "!- I - -17 n W D 21

25

29

40

Dissolved I

50 60

I R O N

Total ,

I

70 80 90

/.Lg/I

Vertical distribution of total and dissolved Cu and Fe.for Station A, Torch Lake, on April 27, 1973.

TABLE IV

Description of leaching conditions and approximate rate of Cu release

Carboy

Wet weight of Wet weight of Torch Lake Type of Type of Tailings, g Sediment, g Water Gas

Rate of Release, gg 1-1 day -~

1 97 0 TLW Air 0.8 2 0 163 TLW Air 1 3 101 0 DW Air 0 4 0 100 DW Air 0 5 99 0 TLW N~ 1 6 0 146 TLW N 2 1 7 98 0 DW Nz 0 8 0 i01 DW N 2 0

Note: TLW refers to Torch Lake Water; DW refers to Distilled Water.

(exc lud ing the e x t r e m e po in t s ) s h o w n in F i g u r e s 6 a n d 7. S u s p e n s i o n o f ta i l ings a n d o f

s e d i m e n t s in dist i l led w a t e r r e su l t ed in a n a p p a r e n t r ap id init ial re lease o f C u the first

d a y a n d s u b s e q u e n t d e c r e a s e to b a c k g r o u n d va lues the rea f te r .


150

IOO

::L 50

0 o

150 I I I I I I I I

Carboy I

I00

f . : 1"50

I , I I I ( I f I I

Io 20 30 40 50 0 io 20 30 40 50

T I M E (days) TIME(days)

1 5 0 , , , 1 5 0 , , , ,

= I 0 0

:k

Carboy 3

0 I i 0 I 0 20 3 0 40 5 0

TIME(days)

IOO :D

0

::L 5O

o

Carboy 4

\ V I o IO

I I I

20 30 40 50

TIME(days)

Fig. 6. Leaching rates of Cu under oxic conditions in Torch Lake water and distilled water.

5. Discuss ion

The Cu concentrations found in Torch Lake during this study are in agreement with those of Brandt and Leddy (1973) and Wright et al. (1973). Equilibrium calculations indicate that the predominant soluble Cu species in Torch Lake water is Cu(OH) +, followed by Cu ++, and then lesser quantities of the complex species CuCO3 °.


1 5 0 , , ; , 1 5 0 , , , j

Carboy 5 Carboy 6

=,oo- - 3,oo- - 0

::I-50 _ :I" 5 _

0 1 I, I I I O 0 I 0 2 0 5 0 4 0 5 0 0 I 0 2 0 :50 4 0 5 0

T I M E (days) T I M E (days)

1 5 0 , , , 1 5 0 , , , ,

- = I 0 0 ¢J

50 50 -

0 ~ 0 I 1 I I 0 Io 20 so 40 50 0 I0 zo so 40 50

T I M E (doys ) T I M E (doys)

Fig. 7. Leaching rates of Cu under anoxic conditions in Torch Lake water and distilled water.

I 0 0 0

:L

Higher metal concentrations, especjaily Of Cu, have been found in areas affected by mine tailings discharges than have been found in areas not so affected. In Torch Lake, the shore tailings deposits and the sediments are implicated in the maintenance of relatively high Cu concentrations in the water throughout the year. These materials were shown to release potentially significant amounts of Cu when suspended in Torch

3 8 4 JOSE MANUEL LOPEZ AND G. FRED LEE

Lake water. Windblown tailings particles from shore deposits can reach Torch Lake water, and thus may also represent a potential source of Cu to the water.

Also, it appears that the lake sediments and tailings deposits on shore can act as a pool or reservoir of available Cu. Because of the relatively short flushing time, this could result in considerable amounts of Cu being transported every year from Torch Lake and surrounding watershed into Keweenaw Waterway and Lake Superior.

The rising cost of Cu may make Cu reclamation from lake sediments and from tailings economically feasible in the near future. However, in the study area, measures must be taken to insure that significant amounts of Cu are not introduced into natural waters as a result of any such operations.

The vertical distributions of Cu, Fe, and Mn in Torch Lake water appear to be correlated. It is possible that hydrous oxides of Fe and Mn control Cu concentrations in these waters. Both Jenne (1968) and Lee (1974) indicate the ability of these hydrous metal oxides to control the concentrations of metals in natural waters through sorlJtion. Association of Cu ions and Cu comlbounds with Fe and Mn hydrous oxides could result in reduced toxicity of Cu. This could partially explain reported occurrences of apparently abundant fish and algal populations in Torch Lake waters despite the presence of Cu concentrations in excess of those considered toxic to some forms of aquatic life.

6. Conclusions

The following conclusions can be drawn from the results of this study:

(1) Up to 100 ~tg 1-1 of apparently dissolved Cu were found in Torch Lake waters during June 1972. Reported spills of cupric ammonium carbonate can partially explain these values; however, relatively high Cu concentrations are found in the Lake all year round.

(2) Higher Cu concentration values occur in those waters studied that have been affected by Cu mine tailings discharges than in those that have not.

(3) Equilibrium calculations indicate that predominance of various soluble Cu species in the order Cu(OH( + > Cu ++ > CuCO3 °.

(4) Reports offish and algal populations living in Torch Lake suggest the occurrence of Cu in a relatively non-toxic form in those waters. This may be due to the fact that Cu in Torch Lake waters appears to be controlled by hydrous oxides of Fe and Mn and not by solubility relationships of Cu compounds. Sorption onto the surfaces of these ubiquitous minerals could result in reduced toxocity of Cu.

(5) Potentially mineable amounts of Cu, contained in taiiings deposits and sediments of Torch Lake, are widespread throughout Keweenaw Peninsula. Laboratory leaching tests demonstrate that Torch Lake sediments and shore Cu tailings deposits can release potentially significant amounts of Cu when suspended in Lake water. Therefore, these materials represent a potentially significant source of Cu to the water on Keweenaw Peninsula and in Lake Superior.


Acknowledgments

This project was supported in par t by the University o f Wisconsin Sea Gran t College

Program, part of the Nat ional Sea Gran t Program, maintained by the Nat ional Oceanic

and Atmospher ic Administrat ion, U.S. Depar tment of Commerce. Jose Manuel Lopez

is supported by the Economic Development Adminis t ra t ion 's Scholarship from the

Commonweal th o f Puerto Rico.

Addit ional support was provided by the Depar tment o f Civil and Environmental

Engineering, University of Wisconsin at Madison where this study was conducted, and

the Center for Environmental Studies University of Texas at Dallas.

We also wish to acknowledge the assistance of J . D . Spain and others at the

Michigan Technological University for sample collection and advice.

References

APHA, AWWA, and APCF: 1971, 'Standard Methods for the Examination of Water and Wastewater', 13th Ed., Amer. Pub. Health Assn., New York, N.Y.

Brandt, D. J. and Leddy, D. G.: 1973, 'Factors Controlling Soluble Copper--(II) Levels in the Keweenaw Waterway', Abstracts, 16th Conf. Great Lakes Res., Internatl. Assoc. Great Lakes Res.

Fetterolf, C. M.: 1972, Private communication. Jenne, E. A.: 1968, in Trace Inorganics in Water, Advances in Chemistry Series, No. 73, ACS,

Washington, D.C. Lee, G. F.: 1974, 'Role of Hydrous Metal Oxides in the Transport of Heavy Metals in the Environment',

Proc. Symposium on Heavy Metals in the Environment, Vanderbilt Univ., In Press. Lopez, J. M.: 1973, 'Aqueous Environmental Chemistry of Copper and Other Heavy Metals in Torch Lake

and Selected Waters of Keweenaw Peninsula', M.S. Thesis, Univ. of Wisconsin at Madison. McKee, J. E. and Wolf, H. W.: 1963, 'Water Quality Criteria', The Resources Agency of California (2nd

Ed.) State Water Quality Control Board, Public. No. 3A. McKim, J. H. and Benoit, D. A.: 1971, J. Fish. Res. Bd. Can. 28, 655. Nussmann, D. G.: 1965, 'Trace Elements in the Sediments of Lake Superior', Ph.D. Thesis, Univ. of

Michigan, Ann Arbor. Steeman-Nielsen, E. and Kamp-Nielsen, L.: 1970, Physiologia Plantarum, 28, 655. U.S. Environmental Protection Agency: Quality Criteria for Water,EPA-440/9-76-023, July, 1976. Wright, T. D., Leddy, D. G., Brandt, D. J., and Virnig, T. T.: 1973, 'Water Quality Alteration of Torch

Lake, Michigan, by Cultural Factors', Proc. 16th Conf. Great Lakes Research, 329.

environmental chemistry of copper in torch lake, michigan

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