Pilot Experiment for Real-time Monitoring Technology Development of Underground Fluids Contaminated with BTEX and NO3-N

The study aimed to analyze staggered change trends and correlations by comparing the values measured by the probe-type sensor with the laboratory analysis values obtained through direct sampling in a pilot experiment. For the experiment, a pilot-scale device (40 cmW × 100 cmL × 50 cmH) was fabricated, and an artificial mixed sample containing BTEX and NO₃-N (BTEX: 9.24 mg/L, NO₃-N: 50 mg/L) was continuously injected at a flow rate of 5.36 L/hr for 6 hours, followed by tap water for 4 hours. The pilot experiment results showed that the BTEX concentrations could not be detected by the probe-type sensor due to its sensitivity and turbidity interference effects. However, the TOC and DOC concentrations showed a strong proportional correlation with the BTEX concentrations analyzed in the laboratory (R² > 0.9). Additionally, while the NO₃-N concentrations measured by the probe-type sensor exhibited a dispersed pattern, the trend was relatively similar to that of the laboratory analysis (R²=0.66). Notably, the NO₃-N concentrations analyzed from the laboratory were highly correlated with electrical conductivity values. Therefore, it can be concluded that TOC, DOC, and electrical conductivity from the probe-type sensor can be very useful for the indirect detection of contaminants, particularly in the cases of early, continuous high-concentration pollutant inflows at actual pollution leakage sites. The results of this pilot experiment will serve as basic data for evaluating the applicability of the testbed for developing an integrated system technology for real-time monitoring of specific types of groundwater contaminants.