## 3 Results
### Sources of Mercury in Soils
\begin{table}
\begin{tabular}{p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline
**Country** & **Studied Land Uses** & **Results** & **Reference** \\ \hline Canada & Remote subarctic lake catchments with forested, wetland, and mixed terrain & Mercury concentrations in sediment were positively correlated with catchment characteristics such as dissolved organic carbon (DOC) input and forest cover. Forested and lower-elevation catchments had higher sediment THg. & [30] \\ \hline China & Mining area in the Wanshan region, Guizhou Province & Hg detected in soils at all sites; no significant bioaccumulation from soil. Hg concentrations were highest in upper watershed areas near former mercury mines. Pollution source analysis identified mining as the main source of Hg in soils. & [22] \\ \hline China & Peri-industrial and urbanized area in Gongzhuling, Northeast China & 24\% of samples exceeded the provincial background value (0.04 mg/kg). & [31] \\ \hline Finland and Sweden & Subarctic lake catchments along a climate–productivity gradient from pristine to intensive forestry & THg leaching from soils increases with forestry preattland ditching. Higher THg baseline values found in eutrophic lakes with intensive land-use. Soil-related leaching of historical mercury due to land modification was a key factor. THg baseline positively correlated with catchment land use and the climate–productivity gradient. & [21] \\ \hline Norway & Boreal forest and peatland soils, with undisturbed and disturbed catchments & Forest soils had higher THg due to canopy throughfall, while MeHg levels were similar across soil types. Soil disturbance from machinery increased MeHg and MeHg-to-THg ratios in topsoil. Peatlands had higher \%MeHg in deeper layers, indicating more local production. Disturbed areas showed significantly elevated MeHg production compared to non-disturbed areas. & [23] \\ \hline Slovenia & Nationwide study covering urban, rural, agricultural, and mining areas including Idrija and Litija & Hg concentrations were highest in western Slovenia due to mining. Urban and industrial areas showed elevated Hg. Hg values exceeded European averages; atmospheric and river sediment transport contributed to regional dispersion. & [23] \\ \hline Sweden & Borealiferous forests in watersheds with clear-cut and mature Norway spruce & MeHg in organic topsoil increased after clear-cutting. & [19] \\ \hline United States & Urban stormwater catchment treated by bioretention rain garden near San Francisco Bay & Hg and MeHg were concentrated in the top 100 mm of soil. Sublerange helped reduce MeHg formation. Soil near nitels exceeded EPA residential screening levels, but not for Hg. Findings highlight surface soil as the main zone of Hg retention. & [32] \\ \hline United States & Green roofs and conventional gravel roofs on campus and commercial buildings & Hg concentrations in runoff were significantly higher from green roofs than gravel roofs, despite runoff reduction benefits from green roofs. Long-term accumulation or immobilization of retained Hg remains uncertain. & [33] \\ \hline \end{tabular}
\end{table} 
Table 1: Summary of the reviewed studies on mercury contamination and pollution in soils from various land uses. Despite the limited presence of studies, irrigation with treated sewage water has also been associated with elevated mercury accumulation in soils. In the study by [PERSON] et al. [35], long-term irrigation with treated sewage water containing mercury concentrations between 0.1 and 1.0 ng/mL resulted in soil mercury levels reaching up to 500 ng/g, compared to only 12 ng/g in control soils irrigated with potable water. [PERSON] et al. [36] also reported that irrigation practices contributed to both surface deposition and vertical migration of mercury in paddy fields, especially under waterlogged and reducing conditions that favored methylation. In a more recent assessment, [PERSON] et al.