P900: a putative novel ERP component that indexes countermeasure use in the P300-based concealed information test.

Countermeasures pose a serious threat to the effectiveness of the Concealed Information Test (CIT). In a CIT experiment, Rosenfeld and Labkovsky in Psychophysiology 47(6):1002-1010, (2010) observed a previously unknown positive ERP component at about 900 ms post-stimulus at Fz and Cz that could potentially serve as an index of countermeasure use. Here, we explored the hypothesis that this component, termed P900, occurs in response to a signal that no further specific response is required in a trial, and could thus appear in countermeasure users that respond differentially depending on the stimulus that appears. In the present experiments, subjects viewed four non-meaningful (irrelevant) dates and one oddball date. In three experiments, we examined P900's antecedent conditions. In the first, the unique item was a personally relevant oddball (the subject's birthdate). In a second, the unique item was a non-personally relevant oddball (an irrelevant date in a unique font color). In a third, all dates were irrelevant. We speculated that the presence of an oddball would not be necessary for P900. All participants made countermeasure-like responses following two specific irrelevant dates. As hypothesized, P900s were seen to non-responded-to irrelevant and oddball stimuli in all subjects but not to responded-to irrelevant stimuli, and the presence of an oddball was not necessary for elicitation of P900. This finding has potential application in deception settings-the presence of a P300 accompanied by the presence of a P900 in response to non-countered stimuli could provide evidence of incriminating knowledge accompanied by the attempt to use countermeasures to evade detection.

Phytoremediation of BTEX hydrocarbons: potential impacts of diurnal groundwater fluctuation on microbial degradation.

Volatile hydrocarbons have multiple potential fates in phytoremediation. This research investigated the relationship between biodegradation and plant uptake of BTEX compounds in laboratory and field settings. At a phytoremediation site, preliminary studies revealed minimal uptake into trees and enhanced degradation potential in the rhizosphere and in the bulk soiL Increased oxygen transport to the vadose zone caused by diurnal rise and fall of the water table was hypothesized to enhance degradation in the bulk soil. A detailed greenhouse study was then conducted to investigate potential bioremediation impacts using field-site soil and DN34 hybrid poplar trees. In rhizosphere soils, the contaminated-planted reactor had significantly higher BTEX degrader populations versus the uncontaminated-planted reactor, as was anticipated. The bulk soil in the planted-contaminated reactor had increased degrader populations than the unplanted-contaminated soil or planted-uncontaminated soil, and planting increased degradation throughout the soil profile, not just in the limited volume of rhizosphere soils. Oxygen diffusive and advective transport into reactors was modeled and calculated. Oxygen input in planted reactors was at least 3 to 5 times higher than in unplanted reactors, and increasing oxygen input lead to increased degrader populations in a linear manner. These results combined with the knowledge that high-transpiration trees draw the contaminated groundwater to the capillary fringe and the rhizosphere indicate that phytoremediation can aid microbial degradation via multiple mechanisms: increasing degrader populations, increasing oxygen input via groundwater diurnal fluctuations, and transporting contaminants to the biologically-enriched soil profile.