Biogeochemical Treatment of ARD at the Island Copper Mine Pit Lake Presented by: C. Pelletier, D. Muggli, M. Wen, and G. Poling Rescan Environmental Services Ltd.
Rupert Inlet and Island Copper Mine Site
Island Copper Mine Open Pit Closure: Approved closure plan included filling open pit with seawater to control ARD from pit walls. Open pit was filled with seawater to approximately 30 meters from the top and a freshwater cap was allowed to develop. Pit Lake to become a passive treatment for run-off coming from the land waste rock dumps. Pit flooding was completed in July 1996 over a period of approximately 30 days.
ICM - Pit Infilling, July 1996
ICM Mine Site - Summer 1999
ICM ARD Qualities (Avg. Quarterly Values during 2001)* NIS SIS ph 7 8 4 5 SO 4 ppm 400 700 1,200 1,600 Ca ppm 140 230 280 410 Mg ppm 20 35 60 100 Cu ppm 0.012 0.023 0.320 1.3 Zn ppm 1.1 2.4 4.8 7.3 Cd ppm 0.007 0.014 0.016 0.035 Mo ppm 0.008 0.012 0.0005 0.001 * Island Copper Mine Annual Environmental Assessment Report
Pit Lake Basic Physical Parameters BASIC DATA Approximate total water volume of lake 241,000,000 m з Surface area of pit lake 1,720,000 m² Volume of top brackish layer (current at 8M depth) Volume of intermediate layer Volume of bottom layer 13,760,000 m з 212,400,000 m з 14,700,000 m з Volume of ARD flows into pit lake combined N & S 1998: 4,500,000 m з 1999: 5,200,000 m з Volume of direct rainfall on pit lake @ 1.78 m/y 3,060,000 m з Volume of run-in, not included in ARD estimate 300,000 m з Total 3,360,000 m з /y
Island Copper Mine: Plan View of Pit Lake
Cross-section of Pit Lake showing Injectors
Pit Lake Fertilization Study Vertical Profiles of Temperature, Salinity, Density and Transmissivity, Pit Lake Station 11, May 24, 2001
ICM Pit Lake - Year 2000 Water Column Chemistry 16 14 12 10 8 6 4 2 0 Aug-96 Oct-96 Dec-96 Feb-97 Apr-97 Jun-97 Aug-97 Oct-97 Dec-97 Feb-98 Apr-98 Jun-98 Aug-98 Oct-98 Dec-98 Feb-99 Apr-99 Jun-99 Aug-99 Oct-99 Dec-99 Feb-00 Apr-00 Jun-00 Aug-00 Oct-00 Dec-00 Feb-01 Apr-01 Jun-01 Aug-01 Oct-01 Dec-01 Feb-02 Dissolved Oxygen (mg/l) W 0 W 100 W 200 W 300 Bottom
Fertilization of the Pit Lake: General Background Current Application Details Apply mixture of liquid ammonium polyphosphate (10-34-0) and urea ammonium nitrate (28-0-0) Introduce fertilizer to top layer of Pit Lake by mixing into propwash Fertilizer is applied to lake every 10 days Monitoring occurs 5 days after application
Pit Lake: Fertilization Study Baseline Sampling 11 Stations 7 Depths (surface, 1, 3, 5, 7, 10, 50 m) CTD, Transmissivity, DO, Secchi, Total and Dissolved Metals, Physical Parameters, Nutrients, Chlorophyll a, Phytoplankton and Zooplankton Taxonomy Post Fertilization Sampling 11 Stations 7 Depths, decreasing to 3 depths (1, 5, 10 m) CTD, Transmissivity, DO, Secchi, Total and Dissolved Metals, Physical Parameters, Nutrients, Chlorophyll a, Phytoplankton and Zooplankton Taxonomy
Pit Lake Fertilization Study Fertilizer container on boat Liquid Fertilizer
Pit Lake Fertilization Study Application of fertilizer to Pit Lake
ICM - Pit Lake Stations
Pit Lake: Fertilization Tracks, May 25, 2001
Pit Lake Fertilization Fertilization 1 (May 25, 2001) Volume Time Distance Area (gallons) (min) (m) (m 2 ) Line 1 80 7.02 1807 7228 Line 2 80 5.11 1313 5252 Line 3 80 4.38 1335 5340 Line 4 80 6.07 1802 7208 Line 5 80 3.52 1146 4584 Line 6 80 3.37 965 3860 Line 7 80 4.1 1139 4556 Line 8 80 3.32 995 3980 Total 640 36.89 10,502 42,008 2.4% of lake area fertilized, assuming 4 m wide lines
Evolution of Pit Lake - Precipitation
Evolution of Pit Lake Slurry Wall with Notch Cuts
Evolution of Pit Lake Water Surface & Pycnocline
Evolution of Pit Lake Events Effecting Levels
Evolution of Pit Lake Zinc Concentrations & Fertilization Periods
Evolution of Pit Lake - Dissolved Copper with Fertilization Periods
Evolution of Pit Lake Cadmium with Fertilization Periods
Chlorophyll a (1 and 3 m) and Fertilizer Applications in Pit Lake, 2001-2002 Chlorophyll a ( µ g/l) 60 50 40 30 20 10 645 kg N 77 kg P N:P= 8.4:1 667 kg N 74 kg P N:P=9.0:1 667 kg N 74 kg P N:P=9.0:1 667 kg N 74 kg P N:P=9.0:1 629 kg N 106 kg P N:P=5.9:1 1.0 m depth Chlorophyll a (µg/l) 0 60 50 40 30 20 10 0 645 kg N 77 kg P N:P= 8.4:1 1/2/97 1/5/97 667 kg N 74 kg P N:P=9.0:1 1/8/97 1/11/97 1/2/98 1/5/98 1/8/98 1/11/98 1/2/99 1/5/99 1/8/99 1/11/99 667 kg N 74 kg P N:P=9.0:1 1/2/00 Date 667 kg N 74 kg P N:P=9.0:1 1/5/00 1/8/00 1/11/00 1/2/01 1/5/01 1/8/01 629 kg N 106 kg P N:P=5.9:1 3.0 m depth 1/11/01 1/2/02 1/5/02 1/8/02 1/11/02
Chlorophyll a (10 and 100 m) and Fertilizer Applications in Pit Lake, 2001-2002 Chlorophyll a ( µ g/l) 60 50 40 30 20 10 645 kg N 77 kg P N:P= 8.4:1 667 kg N 74 kg P N:P=9.0:1 667 kg N 74 kg P N:P=9.0:1 667 kg N 74 kg P N:P=9.0:1 629 kg N 106 kg P N:P=5.9:1 10.0 m depth Chlorophyll a (µg/l) 0 60 50 40 30 20 10 0 1/2/97 1/5/97 1/8/97 1/11/97 1/2/98 1/5/98 1/8/98 1/11/98 1/2/99 1/5/99 1/8/99 1/11/99 1/2/00 Date 100.0 m depth 1/5/00 1/8/00 1/11/00 1/2/01 1/5/01 1/8/01 1/11/01 1/2/02 1/5/02 1/8/02 1/11/02
Phytoplankton Biomass and Dissolved Zinc (0.05, 1 and 3 m) in Pit Lake, 2001-2002 25 0.05 m depth 1.25 Chlorophyll a ( µ g/l) 20 15 10 5 Zn 1.00 0.75 0.50 0.25 Dissolved Zn (mg/l) 0 25 1.0 m depth 0.00 1.25 Chlorophyll a ( µ g/l) 20 15 10 5 Zn 1.00 0.75 0.50 0.25 Dissolved Zn (mg/l) 0 25 3.0 m depth 0.00 1.25 Chlorophyll a ( µ g/l) 20 15 10 5 0 1/3/01 1/4/01 Zn 1/5/01 1/6/01 1/7/01 1/8/01 1/9/01 1/10/01 1/11/01 1/12/01 1/1/02 1/2/02 Date 1/3/02 1/4/02 1/5/02 1/6/02 1/7/02 1/8/02 1/9/02 1/10/02 1/11/02 1/12/02 1.00 0.75 0.50 0.25 0.00 Dissolved Zn (mg/l)
Phytoplankton Biomass and Dissolved Zinc (5, 10 and 100 m) in Pit Lake, 2001-2002 25 5.0 m depth 1.25 Chlorophyll a ( µ g/l) 20 15 10 5 Zn 1.00 0.75 0.50 0.25 Dissolved Zn (mg/l) 0 25 10.0 m depth 0.00 1.25 Chlorophyll a ( µ g/l) 20 15 10 5 Zn 1.00 0.75 0.50 0.25 Dissolved Zn (mg/l) Chlorophyll a ( µ g/l) 0 30 25 20 15 10 5 0 1/3/01 1/4/01 Zn 1/5/01 1/6/01 1/7/01 1/8/01 1/9/01 1/10/01 1/11/01 1/12/01 1/1/02 1/2/02 Date 100.0 m depth 1/3/02 1/4/02 1/5/02 1/6/02 1/7/02 1/8/02 1/9/02 1/10/02 1/11/02 1/12/02 0.00 1.50 1.25 1.00 0.75 0.50 0.25 0.00 Dissolved Zn (mg/l)
Chlorophyll a ( g/l) Dissolved Copper (mg/l) Chlorophyll a ( g/l) Dissolved Copper (mg/l) Chlorophyll a ( g/l) Dissolved Copper (mg/l) Phytoplankton Biomass and Dissolved Copper (0.05, 1 and 3 m) in Pit Lake, 2001-2002 25 0.05 m depth 0.025 20 0.020 µ 15 0.015 10 Cu 0.010 5 0.005 0 25 1.0 m depth 0.000 0.025 20 0.020 µ µ 15 0.015 10 Cu 0.010 5 0.005 0 25 3.0 m depth 0.000 0.025 20 0.020 15 0.015 10 5 0 1/3/01 1/4/01 Cu 1/5/01 1/6/01 1/7/01 1/8/01 1/9/01 1/10/01 1/11/01 1/12/01 1/1/02 1/2/02 Date 1/3/02 1/4/02 1/5/02 1/6/02 1/7/02 1/8/02 1/9/02 1/10/02 1/11/02 1/12/02 0.010 0.005 0.000
Phytoplankton Biomass and Dissolved Copper (5, 10 and 100 m) in Pit Lake, 2001-2002 Chlorophyll a ( µ g/l) Chlorophyll a ( µ g/l) 25 20 15 10 5 0 25 20 15 10 5 Cu Cu 5.0 m depth 10.0 m depth 0.25 0.20 0.15 0.10 0.05 0.00 0.25 0.20 0.15 0.10 0.05 Dissolved Copper (mg/l) Dissolved Copper (mg/l) Chlorophyll a ( µ g/l) 0 25 20 15 10 5 0 1/3/01 1/4/01 Cu 1/5/01 1/6/01 1/7/01 1/8/01 1/9/01 1/10/01 1/11/01 1/12/01 1/1/02 1/2/02 Date 100.0 m depth 1/3/02 1/4/02 1/5/02 1/6/02 1/7/02 1/8/02 1/9/02 1/10/02 1/11/02 1/12/02 0.00 0.25 0.20 0.15 0.10 0.05 0.00 Dissolved Copper (mg/l)
Phytoplankton Biomass and Dissolved Cadmium (0.05, 1 and 3 m) in Pit Lake, 2001-2002 Chlorophyll a ( µ g/l) Chlorophyll a ( µ g/l) Chlorophyll a ( µ g/l) 25 20 15 10 5 0 25 20 15 10 5 0 25 20 15 10 5 0 1/3/01 1/4/01 Cd Cd Cd 1/5/01 1/6/01 1/7/01 1/8/01 1/9/01 1/10/01 1/11/01 1/12/01 1/1/02 1/2/02 Date 0.05 m depth 1.0 m depth 3.0 m depth 1/3/02 1/4/02 1/5/02 1/6/02 1/7/02 1/8/02 1/9/02 1/10/02 1/11/02 1/12/02 0.025 0.020 0.015 0.010 0.005 0.000 0.025 0.020 0.015 0.010 0.005 0.000 0.025 0.020 0.015 0.010 0.005 0.000 Dissolved Cadmium (mg/l) Dissolved Cadmium (mg/l) Dissolved Cadmium (mg/l)
Phytoplankton Biomass and Dissolved Cadmium (5, 10 and 100 m) in Pit Lake, 2001-2002 Chlorophyll a ( µ g/l) Chlorophyll a ( µ g/l) Chlorophyll a ( µ g/l) 25 20 15 10 5 0 25 20 15 10 5 0 25 20 15 10 5 0 1/3/01 1/4/01 Cd Cd Cd 1/5/01 1/6/01 1/7/01 1/8/01 1/9/01 1/10/01 1/11/01 1/12/01 1/1/02 1/2/02 Date 5.0 m depth 10.0 m depth 100.0 m depth 1/3/02 1/4/02 1/5/02 1/6/02 1/7/02 1/8/02 1/9/02 1/10/02 1/11/02 1/12/02 0.025 0.020 0.015 0.010 0.005 0.000 0.025 0.020 0.015 0.010 0.005 0.000 0.025 0.020 0.015 0.010 0.005 0.000 Dissolved Cadmium (mg/l) Dissolved Cadmium (mg/l) Dissolved Cadmium (mg/l)
Phytoplankton/Bacteria Cell Density Above and Below Pycnocline February March April A B A B A B Diatoms (# cells/ml) 13.2 2 23 2.3 27 4.6 Green Algae (# cells/ml) 101242 14942 125945 10188 181261 7013 Cyanobacteria (# cells/ml) 1086 159 3212 131 3923 190 May June July A B A B A B Diatoms (# cells/ml) 7.2 6.5 0.8 5.6 375 3.1 Green Algae (# cells/ml) 188431 12519 165245 8421 133607 9518 Cyanobacteria (# cells/ml) 3552 216 6337 95 8923 17 A = Above Pycnocline, B = Below Pycnocline
Fertilization of the Pit Lake: Controlling Factors Dissolved Zn concentrations are influenced by the phytoplankton population residing in the upper water layer Elevated phytoplankton biomass levels result in low dissolved Zn concentrations To maintain elevated phytoplankton biomass levels, need the following conditions: Adequate nutrients (N, P, C, others) Adequate light and temperature Minimal grazing pressure Non-toxic conditions
Fertilization of the Pit Lake: Optimization: Fertilizer Use by Phytoplankton Fertilizer use by phytoplankton: phytoplankton biomass since 2001 fertilization began (see following figure) Nutrient requirements of phytoplankton: require N, P, Si (some species), C, micro-nutrients Liquid fertilizer adds the following nutrients: nitrate total ammonium urea (not an important N source for phyto.) orthophosphate Examined Residual Nutrients in Upper Layer (only data for nitrate, orthophosphate, silicic acid)
Fertilization of the Pit Lake: Optimization: Fertilizer Use by Phytoplankton Summary From examining residual nutrients: Excess nitrate was being added to the system initially waste of liquid fertilizer was not contributing to enhanced biomass was adding a potential contaminant to the middle layer (e.g. an oxygen source) Adjusted N:P ratio as a result (late July 2001) Orthophosphate was being used up; good, as similar to natural situation; also indicated no other major limiting factor (e.g. a micronutrient)
Fertilization of the Pit Lake: Optimization: Nutrient Limitation of Phytoplankton In order to access nutrient status of resident population, compared phytoplankton composition to the Redfield Ratio Redfield Ratio=7 N: 1 P by weight Used N and P content of particulate matter as estimate of phytoplankton content In nature, lake phytoplankton populations are typically P-limited
Fertilization of the Pit Lake: Optimization: Nutrient Limitation of Phytoplankton Summary Nutrient-status of resident phytoplankton (in situation where adding liquid fertilizer with a 6 N:1 P composition) Likely N-limited during the summer Likely P-limited all other times (P-limitation is more desirable; N-limitation could result in undesirable shifts to cyanobacteria) Conclude: increasing the N content of the fertilizer during the summer months may result in higher phytoplankton biomass levels; extra N would not be wasted
Zinc Mass Balance for Middle Layer (ML) 3.00e+5 4.0 2.75e+5 2.50e+5 3.5 Dissolved Zn Mass (kg) 2.25e+5 2.00e+5 1.75e+5 1.50e+5 1.25e+5 1.00e+5 7.50e+4 ML (kg) NIS+SIS (kg) 3.0 2.5 2.0 1.5 1.0 Dissolved Zn Concentration (mg/l) 5.00e+4 2.50e+4 ML (mg/l) 0.5 0.00 1/1/1997 1/1/1998 1/1/1999 1/1/2000 Time 1/1/2001 1/1/2002 1/1/2003 0.0
Copper Mass Balance for Middle Layer (ML)
Pit Lake Metal Mass Balance Bottom Layer Copper Copper Mass Balance for Bottom Layer (BL) of Island Copper Pit Lake
Sediment Trap Deployed at Deepest Spot in Lake
Bottom Anchor at 353 m Surface Upper Pycnocline at 4.3 m Sediment Trap Samples 6 m 138 days Dec 21, 2001 - May 8, 2002 125 days May 8-Sep 10, 2002 Not Available 71 days Sep 10-Nov 20, 2002 100 m Not Available 153 m Lower Pycnocline at 220 m 352 m
Diatom, Bacteria and Organic Debris in Sediment Trap at 6 m Depth
Bacteria (unidentified) in Sediment Trap at 6 m Depth
Gypsum in Sediment Trap at 153 m Depth
Conclusion Fertilization of top layer of pit lake on semicontinuous basis is very effective as a removal mechanism for zinc, copper and cadmium Geochemical processes (precipitation & adsorption) in the middle layer is removing large amounts of zinc, copper and cadmium The anoxic conditions in the bottom layer promote the iron and manganese cycle which appears to be removing significant quantities of zinc. Copper and cadmium Sulphate reduction is starting to develop in the bottom sediments of the pit lake
Island Copper Mine Schematic of Biogeochemical Processes in Pit Lake
Plant Site with Major Buildings Removed