## 4 Discussion and Future Perspective
\begin{table}
\begin{tabular}{p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt}} \hline \hline
**NbS Type** & **Relative Capital Costs** &
\begin{tabular}{c} **Hg Removal** \\ **Efficiency** \\ \end{tabular} & **Advantages** & **Drawbacks/Risks** \\ \hline \multirow{4}{*}{Constructed wetland} & \multirow{4}{*}{50–120 (installation) [68]} & \multirow{4}{*}{30–98\%} & \(\bullet\) & Passive long-term treatment & \(\bullet\) & Potential MeHg formation under low redox \\  & & & \(\bullet\) & High retention capacity & \(\bullet\) & Performance sensitive to vegetation and microbial activity \\ \hline \multirow{4}{*}{Bioretention cells} & \multirow{4}{*}{100–200 (installation) [69]} & \multirow{4}{*}{24–78\%} & \(\bullet\) & Proven THz retention & \(\bullet\) & Risk of MeHg export under baseflow areas & \(\bullet\) \\  & & & \(\bullet\) & Customizable soil and plant media & \(\bullet\) & Sensitive to hydrologic changes and media composition \\ \hline \multirow{4}{*}{Biochar-amended soils} & \multirow{4}{*}{300–500 (per ton, production cost) [70; 71]} & \multirow{4}{*}{57–95\%} & \(\bullet\) & Enhances soil pH & \(\bullet\) & Variable performance based on feedback \\  & & & \(\bullet\) & Strong sorption for Hg & \(\bullet\) & Risk of MeHg generation under reducing conditions \\ \cline{1-1}  & & & & \(\bullet\) & Flexible application options & \(\bullet\) & May require periodic replacement \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Comparison of cost, mercury removal efficiency, scale, advantages, and risks of selected NbS technologies. Convention on Mercury, which promotes the reduction of mercury emissions and releases to the environment [72]. Incorporating NbS strategies into national action plans under this treaty may support compliance while offering nature-based co-benefits and localized resilience. To strengthen this alignment, financial mechanisms have been recommended for adaptation in order to reflect the multi-functional value of NbSs. Although support has been provided under the Minamata Convention through mechanisms such as the Global Environment Facility and the Specific International Programme, NbSs have not been consistently recognized as eligible for funding. It has been suggested that expanding eligibility to include NbS interventions, particularly those that demonstrate both Hg removal and ecosystem restoration, may allow access to blended financing from climate, biodiversity, and pollution-related funds. Long-term adoption may be facilitated if NbSs are formally integrated into national mercury management strategies, supported by dedicated funding channels and outcome-based monitoring frameworks  
Reflecting the bibliometric analysis conducted in this study, the application of NbSs for mercury mitigation in developing countries has remained limited due to financial, technical, and institutional challenges. Conventional engineering solutions have typically been prioritized in infrastructure investment, while understanding of NbS implementation methods and their associated benefits has often been lacking. Barriers such as insecure land tenure, limited availability of baseline mercury data, and weak monitoring capacity have further constrained progress. It is proposed that these technologies could be advanced using capacity-building programs, policy incentives, and the demonstration of successful pilot projects. Greater integration of NbSs into national mercury control and climate adaptation plans has been viewed as an important step toward enabling equitable and sustainable remediation efforts in resource-constrained regions. Additionally, the potential application of NbSs in artisanal and small-scale gold mining (ASGM) regions, particularly in Africa, has garnered increasing attention due to the growing environmental burden posed by mercury contamination. In Mauritania, elevated levels of Hg were detected in soils near ASGM sites in Chami town, with dispersion patterns driven by wind and tailings transport [73].