Transport of acridine in saturated porous media.

The effects of the aqueous solution pH, temperature, initial solute concentration and non-equilibrium processes on the transport of acridine in saturated porous media (silica) were investigated in a series of continuous-flow column experiments. The enthalpy of the adsorption reaction was more exothermic when the solution pH was above acridine's pKa (5.6) than when it was below. The extent of adsorption was greater when the solution pH was below the pKa of acridine than when it was above. Non-equilibrium effects on the adsorption reaction were found to be unimportant at groundwater velocities. The results from this study suggest that the mobility of acridine in aquifers, in which adsorption to silica edge sites is significant, would increase as the temperature of the groundwater increased and the acridine mobility would be greatest when the pH of the groundwater is above the pKa of acridine. The transport of acridine in such aquifers can be effectively modeled using the local equilibrium assumption.

Antarctic-wide array of high-resolution ice core records reveals pervasive lead pollution began in 1889 and persists today.

Interior Antarctica is among the most remote places on Earth and was thought to be beyond the reach of human impacts when Amundsen and Scott raced to the South Pole in 1911. Here we show detailed measurements from an extensive array of 16 ice cores quantifying substantial toxic heavy metal lead pollution at South Pole and throughout Antarctica by 1889 - beating polar explorers by more than 22 years. Unlike the Arctic where lead pollution peaked in the 1970s, lead pollution in Antarctica was as high in the early 20(th) century as at any time since industrialization. The similar timing and magnitude of changes in lead deposition across Antarctica, as well as the characteristic isotopic signature of Broken Hill lead found throughout the continent, suggest that this single emission source in southern Australia was responsible for the introduction of lead pollution into Antarctica at the end of the 19(th) century and remains a significant source today. An estimated 660 t of industrial lead have been deposited over Antarctica during the past 130 years as a result of mid-latitude industrial emissions, with regional-to-global scale circulation likely modulating aerosol concentrations. Despite abatement efforts, significant lead pollution in Antarctica persists into the 21(st) century.