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Single‐Well, “Push‐Pull” Test for In Situ Determination of Microbial Activities
Author(s) -
Istok J. D.,
Humphrey M. D.,
Schroth M. H.,
Hyman M. R.,
O'Reilly K. T.
Publication year - 1997
Publication title -
groundwater
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.84
H-Index - 94
eISSN - 1745-6584
pISSN - 0017-467X
DOI - 10.1111/j.1745-6584.1997.tb00127.x
Subject(s) - aquifer , methanogenesis , tracer , contamination , nitrate , environmental chemistry , chemistry , sulfate , groundwater , extraction (chemistry) , nitrite , environmental science , in situ , denitrification , environmental engineering , chromatography , methane , geology , ecology , nitrogen , geotechnical engineering , physics , organic chemistry , nuclear physics , biology
A single‐well, “push‐pull” test method is proposed for the in situ determination of microbial metabolic activities in ground‐water aquifers. The method consists of the pulse‐type injection (“push”) of a test solution into the saturated zone of an aquifer through the screen of an existing monitoring well followed by the extraction (“pull”) of the test solution/ground‐water mixture from the same well. The test solution contains a tracer and one or more reactive solutes selected to investigate specific microbial activities. During the injection phase, the test solution flows radially away from the monitoring well into the aquifer. Within the aquifer, biologically reactive components of the test solution are converted to various products by the indigenous microbial community. During the extraction phase, flow is reversed and solute concentrations are measured to obtain breakthrough curves, which are used to compute the quantities of reactant(s) consumed and/or product(s) formed during the test and reaction rates. Tests were performed to determine rates of aerobic respiration, denitrification, sulfate reduction, and methanogenesis in a petroleum contaminated aquifer in western Oregon. High rates of oxygen, nitrate, nitrite, and hydrogen utilization and nitrite, and carbon dioxide production support the hypothesis that petroleum contamination has resulted in an increase in microbial activity in the anaerobic portion of the site. The results suggest that the push‐pull test method should be useful for obtaining quantitative information on a wide range of in situ microbial processes.