The New Lead. Belt of southeastern Missouri has recently become the largest lead producing region of the world. The impact of this rapid development on the previously rural and undeveloped region of the Missouri Ozarks is the subject of a continuing interdisciplinary study. Since the industrial development began, there have been a number of nuisance biological blooms in several of the small streams receiving effluent from the mines and mills. The major constituents of the problem algal growths were identified and found to include: Cladophora, Oscillatoria, Mougeotia, Zygnema, Spirogyra, Cymbella, and a variety of other stalked and non‐stalked diatoms. Secondary blooms of Sphaerotilus were observed to reach problem proportions in some streams, particularly in the autumn. Finely ground rock flour and mineral particles escaping from tailings dams were found to be trapped by the stream vegetation. Concentrations of lead, zinc, copper, and manganese in the algal and bacterial mats were found to be inversely related to distance downstream from the tailings dams. Consumer organisms, including crayfish, snails, aquatic insects, tadpoles, minnows and larger sunfish were analyzed to determine the extent of dissemination and concentration of the heavy metals through food chains. Preliminary results indicated insignificant concentrations of heavy metals in those consumer organisms studied, though in at least one problem stream the normal consumer organisms mentioned were markedly reduced in numbers.

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A microplate technique was developed to determine the conditions under which pure cultures of algae removed heavy metals from aqueous solutions. Variables investigated included algal species and strain, culture age (11 and 44 days), metal (mercury, lead, cadmium, and zinc), pH, effects of different buffer solutions, and time of exposure. Plastic, U-bottomed microtiter plates were used in conjunction with heavy metal radionuclides to determine concentration factors for metal-alga combinations. The technique developed was rapid, statistically reliable, and economical of materials and cells. Results (expressed as concentration factors) were in reasonably good agreement with literature values. All species of algae studied removed mercury from solution. Green algae proved better at accumulating cadmium than did blue-green algae. No alga studied removed zinc, perhaps because cells were maintained in the dark during the labeling period. Chlamydomonas sp. proved superior in ability to remove lead from solution. Many species of algae have been reported to accumulate metals from their aqueous environment. This characteristic is expressed quantitatively by a concentration factor (CF), i.e.,-the ratio of the metal concentration in the algae (micrograms per gram of dry cells) to that in the surrounding water (micrograms per milliliter) (26). This approach makes it possible to compare the metal avidity of different species and strains of algae. However, broad application of this concept has been hindered by the time-consuming nature of the metal assays and the large number of interdependent variables which influence metal removal, e.g., pH, algal species, metal concentration, competing salts, light, culture age, etc. Despite these limitations, several investigators have demonstrated that metal removal by algae is probably largely due to chelation and surface adsorption and constitutes an important response of aquatic flora to metal pollution.-Polikarpov (26) studied a number of freshwater and marine organisms which concentrated radionuclides from nuclear power plant effluents and weapons testing debris and calculated the CF for radionuclides such as "lRu, "7Cs and 'Sr. The CF for algae were found to be high,

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