Data collected during the United Nations High Commissioner for Refugees (UNHCR) water quality database project yielded three trends from the Kutupalong Refugee Camp in Bangladesh: (1) A negative correlation between pH and nitrate, (2) an increase of aqueous lead as pH decreases below pH 5, (3) an increase in the concentrations of iron and manganese at ~pH 6. Soil incubation experiments were designed to measure the chemical and microbial kinetics of the modeled system. Synthetic minerals ferrihydrite (nominally 5Fe2O3�9H2O) and birnessite ((K0.5Mn2O4�1.5H2O) were synthesized, lead-loaded (12�M), inoculated with a microbial community in a synthetic groundwater under 25 and 5 mg/L NO2- and NO3- with 4 mM lactate electron donor. Experimental vessels were initially brought to pH 4.2, capped, continuously shaken and incubated at 32�C for 25-40 days. Samples were analyzed for 208Pb, 56Fe, and 55Mn using ICP-MS. Dissimilatory iron and manganese reductive dissolution was sustained in experiments without an added nitrogen species, where 7�M Fe2+ and 125�M Mn2+, respectively, were released into solution. Manganese was released into solution under all experimental conditions with kinetic constants (KMn,(1/day)) ranging from 689.7�87.0, to 1132.3�31.8, where Fe2+ release was severely limited in the nitrogen experiments, confirmed by FerroZine method. Lead was retained on birnessite in all experiments, while it was effectively de-sorbed from ferrihydrite sustaining 1�M in solution for 25mg/L NO3-, 5mg/L NO2- and 25mg/L NO2- experiments, and 3�M for the nitrogen free experiment. Birnessite more effectively removes lead from solution during anaerobic reductive dissolution. Therefore, wells where lead is released in the Bangladesh refugee camp must be absent of birnessite and controlled solely by sorption to iron oxides. In wells where high iron and manganese are in solution, yet lead is absent, Mn-oxides are the controlling species.

Effects of varied NO2- and NO3- concentrations on Pb release from Fe and Mn rich soils in the Kutupalong Refugee Camp, Bangladesh

247th National Meeting (2014)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.