0504447 Korshin This proposal addresses an important problem, release of lead into drinking water, motivated by recent observations of greatly increased lead release in Washington D.C. The problem is attributed to a switch from the practice of free chlorination to use of chloramination. The researchers propose a new paradigm governing lead release consistent with this observation and based on several hypothesized phenomena: 1) formation of Pb(IV), an insoluble form by oxidation of Pb(II), the soluble form by free chlorine, 2) reduction of Pb(IV) and colloidal mobilization of it by natural organic matter, and 3) electrochemical reduction of oxygen at the lead bearing material surface to produce Pb(II). The proposed activity is experimental and focuses on these three aspects using model waters and a variety of lead-bearing materials. Work will be aimed at elucidating these processes including their kinetics. The PIs will use collected natural organic matter as well as model NOM substances. Surface characterization would also focus on identification of the surface oxide layers.
