In situ evaluation of soil contaminated by total petroleum hydrocarbons using membrane interface probe: a case study from Nanjing, China

Delineation of contaminated soils is important for their remediation; however, reliable and efficient methods remain lacking. In this study, a contaminated site around an abandoned refuelling station in Southeastern China was investigated using resistivity piezocone penetration (RCPTU) and membrane interface probe (MIP) tests to evaluate the spatial distribution of organic contaminants. Various influences on the MIP results were analyzed, such as contaminant concentrations, the soil–groundwater interface and soil properties. Based on RCPTU and sampling results, MIP data were quantitatively evaluated in terms of relative percentage differences. Results from a photoionization detector (PID) and flame ionization detector (FID) were found to overestimate and underestimate the total petroleum hydrocarbon concentrations, respectively. In general, the PID was slightly more accurate than FID. Maps of regional contaminant concentrations were derived from geostatistical analysis of MIP data and were compared with contaminant concentrations measured in soil samples in the laboratory. This paper provides a method for interpreting MIP data with consideration of the influence of soil properties. It demonstrates the effectiveness of using MIP to determine contaminant distributions and increase the efficiency of site remediation programs.