API Publ 4657:1997 pdf download.EFFECTS OF SAMPLING AND ANALYTICAL PROCEDURES ON THE M EASUREMENT OF GEOCHEMICAL INDICATORS OF INTRINSIC BIOREMEDIATION:ABORATORY AND FIELD STUDIES.
A limited amount of field work was done to evaluate data collection methods involving no purging of monitonng wells. For wells in zones geochemically affected by hydrocarbon releases, downholc DO probe measurements on unpurged monitoring wells often yield DO readings that are higher than the DO of formation groundwater. Of the sampling methods examined, the no purging method resulted in the greatest loss of iron and methane from groundwater in geochemically reduced zones.
COMPARISON OF ANALYTICAL METHODS
During the field studies, a comparison of field and commercial laboratory analytical methods for nitrate, sulfate, iron, and alLalinity was made. Field methods are of interest because the rapid sample analyses reduce the potential for changes in composition during shipment and storage. and allow for “real time” data evaluation in the field. Generally, there was fairly good correlation among data produced using the two methods, suggesting that field methods are generally viable alternatives to use of a commercial laboratory.
CONCLUSIONS
While certain groundwater sampling techniques can alter the samples’ geochemistry, these changes may or may not significantly affect data interpretation. Groundwater in hydrocarbon bearing zones often has a geochemistry radically different than background groundwater as a result of naturally occurring hydrocarbon biodegradation. These general shifts in geochemistry can be readily detected using conventional groundwater monitoring and sampling techniques. If the objective is simply to provide geochemical evidence of hydrocarbon biodegradation activity, then any of the groundwater monitoring and sampling techniques examined in this study generally will suffice, as long as they are consistently applied across a particular site. It is typically the differences among multiple measurements at a site that are important. If, on the other hand, the geochemical data are used in quantitative projections of plume migration (e.g., input parameters in BIOPLIJME III modeling), the potential biases in geochemical data introduced through sample collection should be considered In scoping data collection activifles. The potential for samphng methodology to significanUy affect a quantitative intrinsic bioremediation evaluaton will be highest on sites where the dominant biodegradation mechanisms are aerobic respiration, iron reduction, and/or methanogenesis.
In summary, there are several groundwater sampling and analytical methods that may be appropriate for measuring geochemical indicators of intrinsic bioremediation. The methods vary in aecuracy, level of effort, and cost. The choice of the best method for a given application should be based on project-specific and site-specific considerations, particularly the specific manner in which the data are to be used.
API Publ 4657:1997 pdf download
