## 4 Conclusions  
This work aimed to describe the current state of groundwater contamination with CLHCs used for a long time in a former refrigerator factory and to apply the semi-quantitative screening of selected chemical parameters (VOCs, CH4, CO2, O2 and TP) in soil gas to identify the extent of observed groundwater contamination using a portable PID device. The present study has significant applied information as it tries to verify the suitability of soil gas screening as a substitute for the time-consuming and expensive monitoring of groundwater contamination with CLHCs. Despite the cessation of production more than 20 years ago, chemical analyses have confirmed the continuing contamination of groundwater with PCE, TCE, DCE, VC and TCA, which is widespread even below the residential area. It was shown by comparing current concentration data to the older ones that CLHCs in groundwater were attenuated over time, but the presence of accumulation in the form of DNAPLs and probable use in existing smaller industrial operations limit a further decrease in their concentrations. The similarity of the spatial distribution maps of VOCs and CH4 concentrations in soil gas to the dot distribution maps of CLHCs concentrations in groundwater and their statistically significant correlation confirmed by multivariate statistics (PCA method) suggested that soil gas screening was a fast, cheap and relatively reliable method for the identification and spatial delineation of groundwater contamination with these types of industrial organic compounds. Specifically, both CLHCs and VOCs concentrations are highly correlated with the first principal component (PC1) with high values of the component scores (>0.96) and their almost complete overlap. There are some limitations and uncertainties in this study which result mainly from the size of the study area. They can be reduced by the methodology and optimisation only to a certain extent and can bias the results and conclusions. Such uncertainties are the possible presence of preferential pathways (i.e., soil cracks, utilities or conductive zones) in a densely built-up area with still-active industrial facilities, ambient air intrusion, the possible distortion of the concentration gradient between the groundwater table and ground surface in soil gas by hydrologic and geologic variables, such as a varying moisture content, perched water or impermeable layers, heterogeneity in microbial activity and the content of organic matter and clay that affects the adsorption of hydrocarbons in soils and limits the partitioning of contaminants into the vapour phase and other factors. Despite this, the application of soil gas screening led to the identification of before undetected groundwater contamination sources, confirmed by subsequent groundwater sampling by newly designed monitoring wells. Without the application of screening soil gas measurements, these contamination sources would remain undetected, leading to a difficult and risky decision about site management. This emphasises the advantage of applying soil gas measurements and sampling as one of the inexpensive screening methods that are able to cover wide areas with reasonable efforts. **Supplementary Materials**: The following supporting information can be downloaded at: [[https://www.mdpi.com/xxx/s1](https://www.mdpi.com/xxx/s1)]([https://www.mdpi.com/xxx/s1](https://www.mdpi.com/xxx/s1)), Figure S1: Relief of the Neogene sediment formation: Supplementary Text S1: Human health risk assessment: Table S1: Chemical toxicity values of chlorinated hydrocarbons used in the human health risk assessment: Table S2: Exposure parameters used to calculate chronic average daily doses (CADD) and lifetime averaged daily dose (LADD) and their explanation: Table S3: Drinking water standards according to the European Union (EU), the United States Environmental Protection Agency (USEPA) and the World Health Organisation (WHO) and indication and intervention criteria (ID and IT, respectively) for chlorinated hydrocarbons in groundwater. The values are in ug/L.