## 3 Results
### Mercury Removal Performance of NbSs
#### 3.3.2 Hg Removal Through Plant Uptake  
In addition to NbS types, the influence of specific vegetation on THg removal and MeHg dynamics in NbSs has been extensively examined in recent studies, which are summarized in Table 3. In the study by [PERSON] et al. [45], _Aquarius palifolius_ was used in a free water surface constructed wetland system to remediate mercury-contaminated water, particularly from artisanal gold mining sources. The plant was found to function effectively as a hyperaccumulator, absorbing Hg from the water primarily through its submerged roots. The process followed a Langmuir isotherm model, indicating monolayer adsorption on a homogenous surface, and achieved up to 91.8% mercury removal. This model assumes that mercury binds to the plant surface in a uniform way, forming only one layer of adsorption. Moreover, in the study by [PERSON] et al. [47], a constructed wetland in South Florida was investigated for its role in mercury methylation, particularly under varying inflow sulfate concentrations and dry-rewet cycles. The study demonstrated how environmental factors such as sulfate influx and drought-induced dryouts enhance in situ microbial methylation of Hg. Cells experiencing dryouts showed significantly higher MeHg levels, with inflow sulfate identified as a major stimulant of sulfate-reducing bacteria that facilitate Hg methylation. Meanwhile, [PERSON] et al. [48] implemented a novel engineered system using zero-valent iron and pyrrhotite in a vertical flow constructed wetland planted with _Acorus calamus_. This configuration achieved 98.9% total Hg removal by enhancing redox reactions, which allowed efficient Hg uptake by the substrate and plants while suppressing MeHg formation, making it one of the most effective configurations reported. The study by [PERSON] et al. [41] evaluated a pilot-scale constructed wetland treatment cell amended with gypsum (CaSO\({}_{4}\)) to reduce mercury in contaminated water. While the system achieved \(\sim\)50% removal of THg, it also stimulated microbial activity that increased MeHg concentrations eightfold, especially in sulfate-rich conditions. However, planting _Potamogeton pusillus_ was shown to mitigate MeHg buildup through demethylation, highlighting the importance of vegetation in balancing treatment outcomes. This pattern in MeHg buildup was similarly observed in a study by [PERSON] et al. [40], where the untreated control wetland increased MeHg concentrations by 11%, indicating enhanced methylation activity in the absence of chemical coagulants. Both findings emphasized that while wetlands can effectively lower total Hg, they also have the potential to promote MeHg production if not properly managed. \begin{table}
\begin{tabular}{p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline \hline
**NbS Type** & **THg Removal Efficiency** & **MeHg Change** & **Statistical Significance** & **Reference** \\ \hline Free water surface flow constructed wetland & 86.3 & Not reported & Not reported & [44] \\ \hline Free water surface flow constructed wetland with amendments & 98.9 & Decreased & \(p<0.01\) & [38] \\ \hline Constructed wetland mesocosm & 50 & Increased & \(p=0.0001\) & [40] \\ \hline Free water surface flow constructed wetland & 91.8 & Not reported & Not reported & [45] \\ \hline Biochar cells & 63 & Increased & \(p<0.05\) & [41] \\ \hline Biochar mesocosoms & 92 & Decreased & \(p<0.05\) & [39] \\ \hline Floating wetland & 78 & Not reported & Not reported & [46] \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Summary of Hg removal efficiencies and MeHg responses across various NbS configurations. Though less frequent, non-wetland treatment systems such as phytoaccumulation reactors were also studied in the obtained articles. [PERSON] et al. [46] studied the effect of four native aquatic plant species (_Eichhornia crussipes, Ludwigia helminthhorriiza, Marsilea quadrifolia_, and _Lenna minor_) in a pilot-scale phytoaccumulation systems for mercury removal from mining wastewater. The study found that _L. helminthhorriiza_ and _E.