AQUATIC EFFECTS MONITORING IN THE MINING INDUSTRY: REVIEW OF APPROPRIATE TECHNOLOGIES

Danielle Rodrigue, Karen Mailhiot, Thomas P. Hynes, Linda J. Wilson and Marcia Blanchette

Canada Centre for Mineral and Energy Technology (CANMET), Natural Resources Canada, 555 Booth St., Ottawa, K1A 0G1

SUMMARY

As part of a review of the Canadian Metal Mine Liquid Effluent Regulations (MMLER), the CANMET Aquatic Effects Technology Evaluation (AETE) program was established to review appropriate technologies for assessing the impacts of mine effluents on the aquatic environment. The AETE program targets the technology involved in the impact assessment process and has a mandate to identify affordable, effective tools for determining and characterizing the impacts of mine effluents on receiving waters. The program is undertaken from a technical and economic versus regulatory perspective. It will not make recommendations for regulations, but provide tools to implement regulatory requirements, with descriptions of benefit and limitations of these tools if used for regulation.

The program is funded by the Canada Centre for Mineral and Energy Technology (CANMET) and the Mining Association of Canada (MAC), but is directed by a consortium of federal, provincial and industrial partners. These include Environment Canada, Department of Fisheries and Oceans, Indian Affairs and Northern Development Canada, Natural Resources Canada, MAC (including participants from Teck, Homestake, Inco, American Barrick, Noranda and Syncrude), and the provinces of Newfoundland, Nova Scotia, New Brunswick, Quebec, Ontario, Manitoba, Saskatchewan and British Columbia. This $3.4 million program began in April 1994 and will conclude in March 1998. The deliverables will be a series of reports on appropriate, cost-effective methods of determining the biological and non-biological impacts of mine effluents on Canada's lakes, rivers and streams.

The program consists of three main technical areas: i. biological monitoring methods in receiving waters; ii. water and sediment monitoring methods; and iii. toxicity testing methods. The scope of the program includes i. base metal mines, including copper, zinc, lead, and nickel, ii. precious metals mines, excluding placer mining, and iii. uranium mines, excluding effects associated with radioactivity. The focus of the current presentation is the toxicity evaluation component which involves both acute and chronic testing.

The objective of the acute toxicity testing program is to evaluate alternatives to rainbow trout (Oncorhynchus mikiss) and Daphnia magna acute toxicity testing methods both of which involve considerable costs and turn-around times. The lengthy process required for sample collection, shipping, testing and report preparation often delays appropriate remedial action to deal with toxic effluent test results. The total cost of a trout bioassay to a mining operation, including laboratory fees and the cost required for sample collection and shipping, may be $1K - $2K. Such costs can become prohibitive when weekly or monthly samples must be taken from a number of effluent streams or receiving environments.

The candidate alternate acute toxicity methodologies will be evaluated in terms of cost, sensitivity, speed (turn-around time), accuracy, applicability, and reproducibility. These potential alternative tests, as determined by the program participants have commercially available test kits and are:

Microtox (luminescent bacteria)

LUMIStox (luminescent bacteria) (excluded: not available in North America)

Toxi-Chromotest (bacteria)

Rotoxkit F (rotifer)

Thamnotoxkit F (crustacean)

Daphnia IQ (D. magna)

Microtox is manufactured by Microbics Corporation of California and is available from Les Technologies Polycontrôles Inc. of Brossard, Québec. An initial investment of at least $25,000 is required for the temperature-controlled photometer and the computerized data reduction software. The cost per analysis will vary but is estimated to be $40. The test involves the measurement of changes in light production by luminescent bacteria (Photobacterium phosphoreum) exposed to an effluent or toxicant. The time required for each test is less than an hour.

Toxi-Chromotest kits are manufactured and sold by Environmental Bio Detection Products Inc. (EBPI) of Brampton, Ontario. One kit costs $300 and can be used for up to 20 quantitative bioassays ($15 plus labour per test). The test is based on the ability of toxic materials to inhibit synthesis of an inducible enzyme in an engineered strain of Escherichia coli. The activity of the enzyme is detected by reacting it with a chromogenic substrate which may be measured either visually or with a spectrophotometer. The time required for a test is 1.5 - 2 hours.

Toxkits (Rotoxkit F and Thamnotoxkit F) are manufactured and sold by Creasel Ltd. of Belgium. Each kit costs US$245 and can be used to perform six complete toxicity tests (US$41 plus labor per test). These kits are based on a 24-hour LC50 bioassay performed in a multiwell testplate using larvae of selected invertebrate species hatched from cysts. The Rotoxkit F uses the freshwater rotifer Brachionus calyciflorus while the Thamnotoxkit F uses the freshwater fairy shrimp Thamnocephalus platyurus. The tests require the use of an incubator and a dissection microscope, and involve a 24-hour incubation period.

The Daphnia magna IQ Toxicity Test is manufactured and distributed by Aqua Survey Inc. of Flemington, New Jersey. The cost for one test is US$50 plus organisms and labour. The test assesses, by means of a visual endpoint, a decrease in a specific enzymatic activity due to toxic stress. The Daphnia magna are exposed to a toxicant dilution series for one hour after which a fluorogenic substrate is added. Unstressed organisms ingest the substrate, cleave the fluorescent marker and fluoresce brightly under longwave ultraviolet light. However, the enzymatic process is inhibited by toxicant-induced stress in organisms. The test provides results in 1.5 hours.

A number of papers which compare the various acute toxicity testing methods with each other and with the conventional toxicity tests were found in the literature. The review indicates that there are many studies in the literature comparing various acute toxicity testing methods as applied to an assortment of chemicals and effluents but that mining effluents have not been included in these examinations.

The evaluation of these alternative acute toxicity tests will be performed in 1995. Eighteen selected mine effluents, including at least 3 non-toxic effluents, will be sampled over a period of 6 months. These test effluents will span the range of parameters (particularly metal concentrations, pH and alkalinity/hardness factors) that are typical of Canadian mine discharges. Test effluents will focus on base-metal discharges from mining, milling and smelting operations.

The results obtained from all acute toxicity testing and chemical analyses will be collated and analyzed by an independent contractor and recommendations will be made on the feasibility of the alternatives.

Similarly to acute testing, chronic testing will also be done on a series of mine effluents spanning a range of parameters (e.g. metal concentrations, pH, and alkalinity/hardness factors) typical of Canadian mine discharges. Finally, sediment toxicity testing will be addressed under the Water and Sediment component, which along with Biological Monitoring component completes the AETE program.

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