Explore the vast range of titles available.

Rapid, accurate detection of heavy-metal content is extremely important for precise risk control and targeted remediation. Herein, a general modeling method and process based on the relationship between Pxrf measured values and site parameters are explored to construct a Pxrf correction model suitable to improve each site’s measurement accuracy. Results show a significant correlation between Pb, Mn, and Zn Pxrf measured values and actual concentrations, with correlation coefficients between 0.8 and 0.93. Through the correlation analysis, the correlation coefficient between the water content and the measured value of pxrf is in the range of 0.2–0.5. Pxrf measurement of all heavy metals was weakly affected by soil organic matter content, with correlation coefficients all lower than 0.5. Model transformation effectively improved the correlation between measured Pxrf value and actual concentration, and transformation increased the correlations of Sr, Mn, and Cu by around 0.11. Model verification results showed that the Pb, Zn, Fe, and Mn models can be used to improve Pxrf method detection accuracy.

Vertical flexible barriers (VFBs) are widely used for contaminant source separation and risk control. Inherent or externally caused damage to a VFB can affect its effectiveness in pollution containment and control, but its effective detection is a major challenge due to its concealed nature. This paper presents a combined pumping and tracer approach to detect defects in VFBs. A high-performance model is used to model the detection process revealing the migration and distribution behavior of the tracer in the triple media system of wellbore–aquifer–VFB to better understand the effectiveness of the method and its performance indicators, including response time, detectable depth, and defect size, and to optimize its application. Simulation results show that the tracer quickly moves through the defect to the monitoring well, and temporal tracer concentration reveals details of the breach in the wall. Sensitivity analysis reveals influential factors, including defect size, depth, and tracer concentration. Results indicate that the size and depth of defects will affect the penetration and response time. Breakthrough is less clear, and response time is longer if defects are small and deep. However, a higher tracer injection concentration can shorten the response time and increase tracer concentration in the monitoring well. Therefore, it is necessary to design the tracer dosing concentration according to the site conditions. For the Yancheng site, tracer concentration was increased from 1000 ppb to 2660 ppb to ensure the detection of leakage points at 4 m or deeper.