Evaluation of Toxicity, Bioavailability and Speciation of Lead, Zinc and Cadmium in Mine/Mill Wastewaters

The toxicity of common compounds of lead, cadmium and zinc was evaluated in waters similar to that found in the world\u27s largest lead producing area in Missouri. Static, acute toxicity tests were performed using fathead minnows (Pimephales promelas) and water fleas (Daphnia magna) respectively. Test organisms were subjected to varying amounts of sulfide, carbonate, chloride and sulfate salts of lead, zinc and cadmium mixed in hard, alkaline waters typical to this region. Median lethal concentrations were calculated using nominal versus measured metal concentrations. Measured metal concentrations included four different metal fractionation (extraction/filtration) techniques at different pH levels which included dissolved , available , easily dissolved and total metals. Most consistent correlations between mortality and metal concentrations were found with the Total or Nominal values. The Easily Dissolved metals which corresponded to acid soluble criteria did not effectively represent toxicity and bioavailability of metals. A metal speciation model, MINTEQA2, was used to predict the concentrations of the dissolved metal species at the pH levels commonly seen in the toxicity test vessels. MINTEQ model results suggested that analysis of metals in aqueous environment is better understood when examining speciation characteristics and would likewise be a better mechanism to develop site-specific water quality criteria for metals

The Distribution Of Chlorine And Iodine In Soil In The Vicinity Of Lead Mining And Smelting Operations, Bixby Area, S.E. Missouri, U.S.A.

Iodine and Cl are enriched in soils in the vicinity of the Magmont and Buick lead mines near Bixby, southeastern Missouri. The enrichments, up to 5.6 ppm I and 305 ppm Cl, are against regional background of 1.26 ppm I and 41 ppm Cl. The area of highest I and Cl is thought to reflect a zone of base metal sulphide mineralization occurring about 400 m below the surface. Iodine and Cl are also enriched in soils immediately adjacent to a tailings pond, hence these elements would appear to be leached from this source. A zone of enhanced I values (up to 2.65 ppm I) to the north of a lead smelter is superimposed on a much larger zone of lead enrichment (up to 12,000 ppm Pb) and is thought to represent I released from sulphide ores on smelting. © 1988

Sex differences in the adult human brain:Evidence from 5216 UK Biobank participants

Sex differences in the human brain are of interest for many reasons: for example, there are sex differences in the observed prevalence of psychiatric disorders and in some psychological traits that brain differences might help to explain. We report the largest single-sample study of structural and functional sex differences in the human brain (2750 female, 2466 male participants; mean age 61.7 years, range 44–77 years). Males had higher raw volumes, raw surface areas, and white matter fractional anisotropy; females had higher raw cortical thickness and higher white matter tract complexity. There was considerable distributional overlap between the sexes. Subregional differences were not fully attributable to differences in total volume, total surface area, mean cortical thickness, or height. There was generally greater male variance across the raw structural measures. Functional connectome organization showed stronger connectivity for males in unimodal sensorimotor cortices, and stronger connectivity for females in the default mode network. This large-scale study provides a foundation for attempts to understand the causes and consequences of sex differences in adult brain structure and function

Fish From Missouri\u27s Lead Belt: To Eat Or Not To Eat

Data collected over the past four years indicate that filets of suckers and some species of sunfish taken from certain sites in Missouri\u27s Old Lead Belt consistently contain elevated lead concentrations which exceed the limit of 0.3 μg/g suggested by the World Health Organization. The problem exists in bottom-feeding species taken from some sites along the Big River affected by erosion from abandoned lead tailings piles. Fish from many other sites within the Old Lead Belt and the New Lead Belt, including current wastewater treatment systems, are within the acceptable limits for lead in food. Public health implications are discussed relative to observed lead concentrations and available data regarding lead toxicity to humans. © 1986 Science and Technology Letters

Lead Concentrations in Fish and River Sediments in the Old Lead Belt of Missouri

Although active mining activities in the Old Lead Belt of Missouri ceased in 1968, old tailings piles remain and continue to impact the lead (Pb) concentrations in sediments and fish in the Big River and Flat River Creek in Missouri. A 3-year study was conducted that examined the Pb concentrations in organic-rich sediments, fish fillets, and fish whole bodies at 13 sites in these two rivers. The results showed that the sediments had significantly elevated Pb concentrations near and beyond the tailings piles compared with control sites upstream from the mining activity. The results also showed the Pb concentration in sediments correlated well with Pb concentrations in suckers (r = 0.86, p \u3c 0.0001) and small sunfish (r = 0.82, p \u3c 0.0001). Annual average Pb concentrations in sucker fillets ranged up to 0.67 g/g (wet weight basis) and exceeded the World Health Organization guidelines of 0.3 g/g (wet weight basis) at many of the sample sites. Fillets of bass, which feed at a higher trophic level, had much lower Pb concentrations than either suckers or small sunfish, and no bass fillet samples exceeded the WHO guideline. Whole body Pb concentrations in small sunfish were also determined and correlated strongly (r = 0.92, p = 0.0004) with sediment concentrations before leveling at a maximum of approximately 20 g/g (wet weight basis)

Lead and Zinc Removal by Laboratory Scale Constructed Wetlands

Constructed wetlands have the potential to trap and remove metals in mine wastewater. to determine the effectiveness of constructed wetlands for treating selected heavy metals in neutral mine effluent typical of lead mines, eight laboratory-scale constructed wetlands were set up to treat a synthetic, slightly alkaline, mine water containing 34.2 mg/L sulfate (SO4(2-)), 50 micrograms/L lead (Pb), and 300 micrograms/L zinc (Zn). after 45 days, one of the wetlands was switched to treat a synthetic smelter effluent with a much greater load of SO4(2-), sodium (Na+), and Pb. Temperature, hydraulic loading, and substrate composition typically did not affect treatment efficiency. the pH of the effluent was reduced from 8.0 to 8.5 to near neutral. the average removal in the eight wetlands was 90% for Pb and 72% for Zn. in wetlands operating on synthetic mine water, SO4(2-) was completely removed, likely by conversion to sulfide by sulfate-reducing bacteria. in the wetland operating on synthetic smelter effluent, only approximately 25% of 6 g/L influent sulfate was removed, and a breakthrough period of 4 days for Na+ was observed. Whole effluent toxicity assays on undiluted wetland effluent from wetlands treating mine and smelter water had 100% survival of fathead minnows and Daphnia magnia. Survival of Ceriodaphnia dubia was zero in undiluted effluent, but 75 to 100% survival was observed when the effluent was diluted to one-half strength