Assessment of Remediation Efficiency for Soils Contaminated with Metallic Mercury in Hydrocarbon Extraction Zones  
Anna Krol  
Cil and Gas Institute--National Research Institute, ul. Lubicz 25a, 31-503 Krakow, Poland; [EMAIL_ADDRESS] (E.K.-Z. ); [EMAIL_ADDRESS] (M.G.) [PERSON]  
Cil and Gas Institute--National Research Institute, ul. Lubicz 25a, 31-503 Krakow, Poland; [EMAIL_ADDRESS] (E.K.-Z. ); [EMAIL_ADDRESS] (M.  
It should be noted that the typical mercury content in uncontaminated soils worldwide ranges from 0.008 to 1.11 mg/kg [1; 21]. In Poland, typical mercury concentrations in soil range from 0.002 to 1.5 mg/kg [1; 21]. However, as shown in Table 1, the mercury content in contaminated soils is highly variable, ranging from 0.05 to even 9000 mg/kg. The test results described in the literature most commonly refer to the total mercury content in the soil. Specific studies have also investigated areas contaminated with metallic mercury, with metallic mercury constituting up to 38-98% of the soil contamination [12; 13; 18; 19]. Increased mercury levels in soils can also result from dust emissions from cement plants and other sources of dust. The cement significantly contributes to both European and global mercury emissions [4; 5]. As mentioned earlier, industrial areas involved in hydrocarbon exploitation and extraction are seldom described as mercury-polluted zones. However, the 2013 Global Mercury Assessment: Sources, Emissions, Releases, and Environmental Transport by UNEP highlights the oil and gas industry as a significant contributor to mercury emissions into the air [6; 7; 8]. Another report, the IKIMP Mercury Knowledge Exchange [20], extensively discusses the harmful effects of mercury and the sources and extent of mercury in technologies for the extraction, processing, and use of fluid and gaseous fuels. Previous studies also indicate the potential for local mercury contamination in soils of industrial areas associated with hydrocarbon extraction [21; 22; 23]. Given the global presence of mercury contamination in soils, it is necessary to develop methods for the disposal of mercury and the remediation of soils contaminated with mercury. There are \begin{table}
\begin{tabular}{l l l l} \hline \hline
**Type of Activity** & **Contaminated Area** &
\begin{tabular}{l} **Determined Soil Mercury** \\ **Content [mg/kg]** \\ \end{tabular} & **Source of Data** \\ \hline Mercury mines & China, Spain, Slovenia, USA, Turkey & 0.05–9000 & [17] \\ Gold and silver mines & China, Venezuela, Mexico & 0.05–1100 & [1; 4; 7; 17; 19] \\ Cinnabar and sulfide mines & Spain, Italy, Portugal & 1–1709 & [4; 14; 15; 16; 17; 19] \\ Chemical factory & Portugal, Romania, the Netherlands & 0.07–4150 & [4; 12; 17; 18] \\ Discharge lamp production plant & Poland & 0.03–39.25 & [4] \\ Aerometer factory & Warsaw (Poland) & 62–393 & [2; 4] \\ Coal power plant Siersza & Poland & 0.02–0.18 & [2; 4] \\ Natural gas mines & Polish Lowland Region (Poland) & 0.05–495 & [21; 22; 23] \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Summary of exemplary results from studies on mercury in soil in areas related to industrial activities worldwide [1; 2; 4; 7; 12; 14; 15; 16; 17; 18; 19; 20; 21; 22; 23]. Figure 1: Industrial sectors associated with mercury environmental pollution. many ways to remediate mercury-contaminated soils [1; 24; 25; 26; 27; 28; 29; 30; 31; 32; 33; 34; 35]. These methods can be categorized based on whether they are applied directly at the contaminated site, known as in situ methods (methods applied directly in the area where the contamination occurred), or applied outside the contaminated area, known as ex situ methods. Another criterion for categorizing the remediation methods is the nature of the method used.