ABSTRACT
Analytical techniques were combined with geochemical modelling to study the release mechanisms of pollutants from an abandoned gold mining tailings storage facility near Johannesburg. Inverse modelling of sampled tailings pond water and experimental single extractions using various solutions indicated which combination of naturally occurring leaching solutions were likely to give rise to the observed pond water quality. The potential fate of metals in the pond was predicted by modelling the formation of efflorescent crusts and adsorption onto hydrated iron oxide minerals.
Subject(s)
Environmental Pollutants/chemistry , Metals/chemistry , Models, Chemical , Gold , Mining , South AfricaABSTRACT
The search for novel insect repellents has been driven by health concerns over established synthetic compounds such as diethyl-m-toluamide (DEET). Given the diversity of compounds known from frog skin and records of mosquito bite and ectoparasite infestation, the presence of mosquito repellents in frogs seemed plausible. We investigated frog skin secretions to confirm the existence of mosquito repellent properties. Litoria caerulea secretions were assessed for mosquito repellency by topical application on mice. The secretions provided protection against host-seeking Culex annulirostris mosquitoes. Olfactometer tests using aqueous washes of skin secretions from L. caerulea and four other frog species were conducted to determine whether volatile components were responsible for repellency. Volatiles from Litoria rubella and Uperoleia mjobergi secretions were repellent to C. annulirostris, albeit not as repellent as a DEET control. The demonstration of endogenous insect repellents in amphibians is novel, and demonstrates that many aspects of frog chemical ecology remain unexplored.
