Bioavailable Ferric Iron (BAFelll) Assay

摘要

CDM invented and developed a bioavailable ferric iron (BAFeIII) assay with funding from the U.S. Air Force (USAF). This is a standardized bioassay that directly measures the concentration of BAFeIII in soil or sediment. A BAFeIII test kit based on the assay is manufactured by New Horizons Diagnostics Corporation (NHD) of Columbia, Maryland. BAFeIII is defined as ferric iron (FeIII) that is capable of being reduced by microorganisms that oxidize another chemical species and derive energy from the electron transfer. BAFeIII is an important terminal electron acceptor with significant assimilative capacity in many natural environments. Dissolved ferrous iron (FeII) in groundwater is typically measured to assess FeIII reduction and calculate assimilative capacity, but this measurement underestimates this terminal electron accepting process (TEAP) because most FeII remains bound to the soil. Dissolved FeII also gives no indication of the amount of FeIII present in aquifer soil that is bioavailable. BAFeIII in the soil must be measured in order to quantify the true assimilative capacity of an aquifer. Iron-reducing bacteria (FeRB) use and are dependent on BAFeIII. FeRB are known to oxidize or mineralize various organic compounds, such as benzene, toluene, vinyl chloride (VC), and methyl tertiary butyl ether (MTBE). Continued activity over a period of years is dependent on the presence of sufficient BAFeIII. BAFeIII can also affect reductive dechlorination in monitored natural attenuation (MNA) and enhanced anaerobic biodegradation (EAB) applications. BAFeIII can result in trichloroethene (TCE) being reductively dechlorinated to cis-Dichloroethene (cDCE) only, and further reductive dechlorination can be inhibited (AFCEE, 2004). Thus, knowledge of the BAFeIII concentration can indicate the potential for incomplete reductive dechlorination of TCE. It can also be used for planning EAB remedies.