Mercury in a Swedish landscape over 30 years : a thesis on mercury concentrations in different water-cathments in Krycklan and Degerö stormyr

Sammanfattning: The purpose of this thesis is to examine trends in concentrations of total mercury (TotHg) and methylmer¬cury (MeHg) in water streams around Vindeln, Sweden, located northwest of Umeå. The relation¬ship between dissolved organic carbon (DOC) and TotHg were also examined in this thesis. Data gathered for 30 years from four different sample sites collected from Krycklan catchment study (KCS) and Degerö stormyr. All samples were compiled into excel files and sorted by location and date to later analyse the concentrations of TotHg, MeHg and DOC. To analyse the concentrations of TotHg and MeHg a Mann-Kendall test was conducted to identify monotonic trends, with a sig¬nificance level of 0.05, using RStudio. The tests null hypothesis was that there were no monotonic trends in the data. The alternative hypothesis was that a significant trend could be observed. When testing the correlation between DOC and TotHg scatterplots were made with a trendline, with TotHg on the y-axis and DOC on the x-axis. A descriptive analysis was made to observe any trends present in the plots as the samples was dependent to each other a linear regression could not be conducted. The results presented no significant trend in the concentration of TotHg and MeHg on any of the sites. Most surprising, no positive trend could be observed in the correlation between TotHg and DOC. One emphasized importance of this thesis is that it’s furthered and the work of monitoring mercury in these streams are continued, to see how a longer timespan effects concentration.