Manganese is a metallic element that occurs naturally in rock and soils/sediments weathered from rock. It is most abundant in areas of metamorphic and sedimentary rock. Dissolution from rock and soils/sediments into ground water and surface water has resulted in the presence of varying levels of manganese in natural waters. The Canadian Water Quality Guidelines (CCME, 1987) lists a range of manganese concentrations of 0.01-1.70 mg/L for Pacific Region surface waters. High concentrations of dissolved manganese have been observed in many coastal areas, including the Lower Mainland, Vancouver Island and the Queen Charlotte Islands (SEACOR, 1998).
Adverse effects of manganese on freshwater aquatic organisms have been reported in a number of studies, although the cause-effect evidence is not extensive. In order to lay the foundation for the establishment of scientifically based guidelines for the protection of aquatic life in British Columbia, a number of toxicity tests were initiated using representative freshwater and marine organisms present in BC waters. The studies were commissioned by the Water Management Branch of the BC Ministry of Environment, Lands and Parks and were conducted by Environment Canada at their Pacific Environmental Science Center aquatic toxicity laboratory in North Vancouver, BC.
1.1 OBJECTIVES
The primary purpose of the toxicity testing was to provide new ecological toxicity data for British Columbia freshwater and marine organisms and to use the data to develop scientifically based, defensible guidelines for the protection of aquatic life. Use of species native to British Columbia waters should result in guidelines that are more applicable to BC waters. Evaluation and interpretation of this data has provided new research information on the concentration/effects relationship of manganese on aquatic organisms that are present in BC waters. This thesis research concentrates on freshwater organisms rather than marine organisms.
The objectives of the research presented in this thesis are as follows:
1. To review the existing freshwater aquatic life guideline for manganese;
2. To evaluate the practicality of the existing guideline;
3. To review the information available in the literature on manganese toxicity in aquatic environments; and
4. To use new toxicity test data generated by the BC Ministry of Environment, Lands and Parks for native BC species and information gathered in Step 3 in order to improve the existing freshwater aquatic life guideline.
1.2 REGULATORY BASIS OF EXISTING GUIDELINE
The BC Ministry of Environment, Lands and Parks has a mandate (under the Environment Management Act and the Guideline and Standard Procedure Policy) to establish water quality guidelines to protect water quality in BC The Canadian Council of Ministers of Environment (CCME) develops water quality guidelines at the national level to protect the Canadian environment and publishes Canadian Water Quality Guidelines (CCME, 1987) for inorganic and organic parameters based on various water uses including drinking water, irrigation, and aquatic life support. BC Environment will adopt CCME guidelines as working values for parameters for which no B.C. guidelines exist.
The BC Ministry of Environment, Lands and Parks published the document Approved and Working Criteria for Water Quality - 1995 (BCMELP 1995) which compiled water quality criteria for various substances and several water uses, including aquatic life. For manganese, values were recommended for drinking water, food processing, fresh water aquatic life, marine water aquatic life, irrigation water and industrial uses including boilers, textiles, pulp and paper, tanning, chemical production and cooling. Recommended values of 0.1 to 1 mg/L were provided for fresh water aquatic life and dissolved manganese and manganese precipitates were the important forms to consider.
At present, BC guidelines for manganese are tentative and under review. CCME guidelines for manganese exist for water used for human consumption and for irrigation watering but no guidelines exist for the protection of aquatic life. The drinking water guideline of 0.05 mg/L was not toxicologically based; it was established to address aesthetic considerations such as staining of plumbing and laundry and undesirable taste. The irrigation water guideline of 0.2 mg/L was applied to continuous watering on all soil types specifically to protect possible toxic responses by plants growing in acidic soils. A guideline of 10 mg/L was recommended for neutral and alkaline soils for water use of up to twenty years. Data regarding toxic effects on aquatic life were not considered sufficient to recommend a guideline.
1.3 SCIENTIFIC BASIS OF EXISTING GUIDELINE
The source document for the recommended manganese fresh water aquatic life values of 0.1 to 1 mg/L was the United States Environmental Protection Agency (National Academy of Sciences, 1973). A document titled A Review of the EPA Red Book: Quality Criteria for Water (Thruston et. al., 1979) reviewed many of the existing water quality criteria, including manganese. The chapter on manganese raised several questions regarding the scientific basis for the EPA guidelines and stated that the Red Book's description of the effects of manganese on aquatic life "is inadequate, of little value to aquatic biologists, generally out of date, lacks completeness, and seldom cites the available literature." This suggests that the existing water quality criteria for aquatic life protection are not soundly based.
Review of data generated from research conducted since 1979 in conjunction with the BC Environment toxicity tests, is expected to provide new information to enhance the data used by EPA to establish the Red Book guidelines on which the BC Environment criterion was based. Review of new literature information is one of the objectives of this thesis research and is presented in the Literature Review section.