Development of aquatic plant bioassays for rapid screening and interpretive risk assessments of metal mining liquid waste waters

The use of non-photosynthetic organisms alone to describe environmental impact has been recognized by regulatory agencies, industry, and academia as being insufficient both in Europe and North America. Lack of adequate testing methods for photosynthetic aquatic organisms is considered as a major impediment to the successful regulation and safe use of pesticides and waste discharges and is of even more concern to the metal mining industry due to the non-biodegradable nature of its waste streams. This work shows that the chemical effluent limits set in the “Metal mining liquid effluent regulations and guidelines” provide variable protection of aquatic photosynthetic organisms. Aquatic effects of the more toxic metals (e.g., copper, nickel, and zinc) may occur at levels that are one to two orders of magnitude lower than present limits. To establish adequate protection of receiving water bodies it may be necessary to establish site-specific criteria taking into consideration toxicity modifying factors of individual sites. If the establishment of such criteria is determined with a host of ecologically relevant organisms, it will be possible to design effective environmental protection at the least possible cost.