API Publ 4668:1998 pdf download

API Publ 4668:1998 pdf download.Delineation and Characterization of the Borden MTBE Plume: An Evaluation of Eight Years of Natural Attenuation Processes.
MTBE/C1 concentration ratios were calculated for each sampling point and found to be between 0.001 and 0.008, much lower than the ratios of 0.33 to 1.0 calculated during the initial 16 months of the experiment This drop in the MTBEJCI ratio could either suggest that MTBE had undergone transformation or that additional Cl from other sources, such as the underlying landfill leachate plume, had mixed with the plume. Neither TBA nor TBF, two potentiai MTBE degradation products, was found in any of the samples. This could suggest that MThE had not been transformed or that these compounds are also degraded readily if they are formed. Finding potential degradation products is usually a good indication of transformation; however, in the case of very slow degradation rates, as expected for MTBE, those compounds might be found at concentrations too small to be measured.
This mass balance comparison of predicted versus observed MTBE mass suggests a significant loss of MTBE in the Borden aquifer, which could potentially be attributed to biodegradation, abiotic degradation, sorption, volatilization, or plant uptake. Abiotic MTBE degradation involving subsurface material was only shown in one set of experiments by Yeb and Novak (1995). These researchers found MTBE to hydrolyze when hydrogen peroxide was added but iron was needed to act as a catalyst This reaction is not favored in aerobic or near-neutral (pH > 6.5) environments such as the Borden aquifer and therefore is not likely to contribute to MTBE mass loss in this study. Based on linear sorption, the calculated MTBE retardation factor is 1.02 for the Borden aquifer (Schirmer ef a!, 1998). This low value suggests that sorption cannot account for the large discrepancy between the initial and final MTBE mass. Furthermore, the MTBE was introduced into the aquifer 1.5 m below the water table; therefore, volatilization is not an attenuation factor in this experiment.
Plant uptake or phytorernediation is another potential attenuation factor. At the site, two forested areas exist with predominantly aspen and pine trees and ferns. The main orientation of tree roots is horizontal, not vertical, and such roots generally spread horizontally as far as 1-3 times the tree height Almost 90 percent of a tree’s roots can be found within the upper 0.6 m of soil (Dobson and Moffat, 1995). Root gro1h has been found to stop completely when air space dropped to 2 percent.