## 3 Results
### Trends in Epilimnetic Methylmercury, Total Mercury, and Sulfate Concentrations
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & \multicolumn{3}{c}{**Hg Deposition, \(\mu\)g m\({}^{2}\)**} & \multicolumn{3}{c}{**Precip.-Weighted [Hg], ng L\({}^{-1}\)**} \\ \hline
**MDN/NTN Site** & **EV\({}_{\text{1998}}\)** & **EV\({}_{\text{2018}}\)** & **\% Change** & **EV\({}_{\text{1998}}\)** & **EV\({}_{\text{2018}}\)** & **\% Change** \\ \hline Marcell (MN16) & 9.37 & 7.47 & \(-20\%\) & 11.41 & 9.63 & \(-16\%\) \\  & [8.05, 10.70] & [6.14, 8.80] & & [9.88, 12.95] & [8.10, 11.17] & \\ Fernberg (MN18) & 8.00 & 6.12 & \(-24\%\) & 12.31 & 7.93 & \(-36\%\) \\  & [6.99, 9.01] & [5.11, 7.12] & & [11.12, 13.50] & [6.74, 9.13] & \\  & Mean percent change: & \(-22\%\) & & & \(-26\%\) \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Trend analysis results for wet mercury (Hg) deposition rate and precipitation-weighted mean concentrations for two National Atmospheric Deposition/Mercury Deposition Network sites in northern Minnesota. [Hg deposition \(\mu\)g m\({}^{-2}\), annual Hg deposition rate in micrograms per square meter; Precip.-weighted [Hg], ng L\({}^{-1}\), annual precipitation-weighted mean Hg concentration in nanograms per liter; EV\({}_{\text{1998}}\) and EV\({}_{\text{2018}}\) are expected values for 1998 and 2018, respectively, from locally weighted regression of the variable of interest versus time in years. % change, percentage change in expected values from 1998–2018. Lower and upper 95 percent confidence limits shown in brackets.]. Aqueous total mercury declined modestly in Brown, Peary, and Shoepack Lakes, with an overlap of the 95-percent confidence intervals for the start and end period of the study (again, indicating perhaps a lack of statistical significance) (Figure 4). The 47% decline in THgq in Ryan Lake appears to be a significant decline with clear separation of confidence intervals in the beginning versus end of the study period. Figure 3: Time series plots for methylmercury (MeHgq) in epilimnetic lake water. Smooth lines are locally weighted regression lines; smoothing parameters, selected as described in the methods section: (**A**) Brown Lake, smoothing parameter = 0.713; (**B**) Peary Lake, smoothing parameter = 0.424; (**C**) Ryan Lake, smoothing parameter = 0.489; and (**D**) Shoepack Lake, smoothing parameter = 0.633. Gray shading indicates the 95-percent confidence interval. A high outlier for Brown Lake (reported concentration 0.51 ng L\({}^{-1}\) for 30 August 2012) is omitted from the plot and regression. Epilimmetic sulfate concentrations decreased in each lake over the study period (Table 4; Figure 5). The trends were nonlinear, revealing midtime series peak concentrations around 2007 for Brown, Ryan, and Shoepack Lakes, and somewhat later (~2010) for Peary Lake. The modest trends reported here (mean decrease of 45%) follow much larger decreases for these lakes from the 1980s to 2000, as reported by [PERSON] et al. (2016), based on a 1980s lake survey reported by [PERSON] (2012). Figure 4: Time series plots for total mercury (TH\({}_{\text{gaq}}\)) in epilimnetic lake water. Smooth lines are locally weighted regression lines; smoothing parameters, selected as described in the methods section: (**A**) Brown Lake, smoothing parameter = 0.713; (**B**) Peary Lake, smoothing parameter = 0.641; (**C**) Ryan Lake, smoothing parameter = 0.424; (**D**) Shoepack Lake, smoothing parameter = 0.3. Gray shading indicates the 95-percent confidence interval.