MnO 2 coprecipitations . Samples were spiked with 150–500 mBq of 209 Po, 230 Th, 232 U, and nat U. After appropriate tracers were added, MnO 2 coprecipitations were performed, based on published methods ( Burnett et al. 2012 ; Moore 1976 ; Nour et al. 2004 ). Potassium permanganate (15 or 30 mg) and bromocresol purple (1 mL, %) were added to acidified (pH < 2) produced fluid ( L) in glass beakers. The sample was diluted 2-fold in distilled water (dH 2 O), covered with a watch glass, and boiled (1 hr). The pH was adjusted to 7–8, and the sample was boiled for 1 hr and cooled overnight. Following the cooling period, the supernatant was aspirated; the remaining slurry (~ 50 mL) was transferred to a plastic conical tube (50 mL) and centrifuged (10 min), and the supernatant was discarded. Beakers were washed twice (5 mL 6 M HCl; 1 mL 1 M ascorbic acid), each time transferring the wash liquid to the 50-mL centrifuge tube to dissolve the MnO 2 pellets. Centrifuge tubes were then gently heated in a water bath to fully dissolve the pellet and clarify the solution.
Should the production and use of chlorine and all chlorinated organic compounds be halted, in view of their adverse effects on the environment and human health?
Those in favour argue that certain chlorinated compounds (PCBs, DDT, CFCs, etc.) have large negative environmental effects. The use of chlorine in disinfectants leads to the production of chloroform, while bulk products (PVC) contribute to the production of chlorinated dibenzo- p -dioxins and dibenzofurans when they are burned.
Those against argue that chlorine and many chlorinated compounds are essential in the control of human health (the prevention of disease transmitted through drinking water that has not been disinfected), and that chlorinated compounds are indispensable intermediates in many production processes, representing a vast economic value.
But such discussions often ignore the fact that Nature contributes significantly to the production of chlorinated organic compounds. More than 1000 such compounds are known, and their contribution to the biogeochemical cycling of chlorine is underestimated. Chlorine is organically bound in large quantities to humic materials, and natural production mechanisms are known for low molecular weight compounds (methyl chloride, chloroform, chlorinated dibenzo- p -dioxins and dibenzofurans). The role of these compounds in the environment is largely unknown.
Naturally-Produced Organohalogens gives a complete overview of the present state of knowledge on the subject, giving a much needed balance to the argument sketched out above.
High levels of testosterone that are naturally produced by some elite female athletes give them a "significant" competitive edge in athletics events that depend on stamina and visuospatial abilities, reveals the first study of its kind, published online in the British Journal of Sports Medicine . This advantage should be taken into consideration when judging women's eligibility for these events in light of the suspension of International Association of Athletics Federations (IAAF) rules, suggest the researchers.