Browsing by Subject "mercury"

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Advanced treatment technologies that remove solids from municipal wastewater consistently meet mercury effluent limits.
(2022-06) Hogan, Kelsey
Since many other sources of mercury (Hg) are difficult to control, the removal of Hg from wastewater is an essential component of maintaining low Hg levels in ecosystems. Numerous studies have investigated solid-liquid interactions of Hg at ng/L levels in natural systems, but few studies have translated insights to highly-engineered, organic-rich systems such as municipal wastewater treatment plants. There is a lack of guidance for design engineers concerned with meeting exceptionally low-level Hg limits, particularly the 1.8 ng/L limit applicable to the Laurentian Great Lakes. A historic Minnesota Pollution Control Agency dataset from over 150 municipal wastewater treatment plants (MWWTP) was analyzed and categorized into technology types. Starting with secondary technology types and continuing to tertiary technology types, Hg concentrations from MWWTP in each technology type were analyzed to indicate if there are technologies that reliably reduce HgT in the effluent to below 1.8 ng/L. Additionally, correlations between total suspended solids (TSS) and HgT (total Hg) were evaluated. Certain technology types were better at removing HgT than others. Secondary technologies including conventional activated sludge, MBRs, and polishing ponds as well as tertiary technologies including fine dual media filters, rotating cloth membrane, and deep bed mono-media filters all consistently meet low-level HgT discharge limits. Effluent HgT measurements were correlated with TSS for several secondary technologies with a hydraulic residence time similar to conventional activated sludge, while technologies with very short (attached growth) or very long (ponds) showed little relation between TSS and HgT in effluent water. Nonparametric statistics were used to compare the effluent HgT among technologies and estimate the reliability of meeting mercury limits. The results of this study could help MWWTP determine appropriate technologies to install to meet regional or state mercury discharge limits.
Data and R code for analysis of mercury concentration and food web differences in walleye and yellow perch from Minnesota lakes with and without invasive zebra mussels, 2019 - 2021
(2023-02-24) Blinick, Naomi S; Ahrenstorff, Tyler D; Bethke, Bethany J; Fleishman, Abram B; Link, Denver; Nelson, Jenna KR; Rantala, Heidi M; Rude, Claire L; Hansen, Gretchen JA; nsblinick@gmail.com; Blinick, Naomi S; University of Minnesota Department of Fisheries, Wildlife, Conservation Biology; Minnesota Department of Natural Resources
This dataset contains δ13C and δ15N stable isotope data for 3,765 biological samples (fish, littoral macroinvertebrates, and zooplankton) collected from 21 lakes between 2019 and 2021, collaboratively by the University of Minnesota and the Minnesota Department of Natural Resources. In addition, 403 samples have corresponding mercury data, based on laboratory analyses conducted by USGS (Tate et al. 2022).
Ecology and Conservation of Common Terns (Sterna hirundo) Breeding in the North American Great Lakes Region
(2021-05) Bracey, Annie
The common tern (Sterna hirundo) is a long-distance migratory waterbird that breeds in both freshwater and marine environments in many parts of the world. Although the most wide-spread tern species in North America, populations have experienced extreme fluctuations during the last half century, with significant declines documented in the Great Lakes region and other inland breeding sites. Because of their reliance on coastal habitats, population declines have often been attributed to direct and indirect effects of human activity, such as habitat loss, modification, and degradation. In the Great Lakes most active breeding colonies occur at managed sites. The goal of my dissertation research was to document population dynamics of common terns breeding in western Lake Superior to understand how movement and demographic parameters vary between colonies and among colonies outside the region. A variety of intrinsic and extrinsic tagging methods were used to follow individuals throughout their annual cycle to identify potential risks to survival and fitness. Each chapter identifies potential risks to the population at different life stages and at different spatial and temporal scales. The first chapter documents large-scale movement patterns of adults breeding in the ‘central population unit’ using solar geolocation tracking devices to identify important migratory routes and wintering locations. Chapter 2 examines how adult foraging behavior influences mercury exposure in adults and chicks, to estimate exposure risk for birds nesting in western Lake Superior. Chapter 3 uses 36 years of mark-recapture data to identify drivers of population change by estimating survival, fecundity, and local-scale movements of adults and juveniles in western Lake Superior. These results filled gaps in knowledge about basic life history of Great Lakes nesting Common Terns and identified multiple potential risks (e.g., conditions at important stopover and non-breeding locations, especially coastal Peru, contaminant exposure at industrially-influenced breeding sites) to this population which can be mitigated through targeted conservation and management actions. Because climate change is expected to exacerbate these threats, it is imperative that suitable nesting habitat be restored and maintained for common terns breeding in the Great Lakes region, especially in the face of future environmental uncertainty and an ever-changing landscape.
The Effect of Atmospheric Sulfate Deposition on Mercury Biogeochemistry in an Experimental Peatland: Impacts, Recovery, and Natural Variability
(2014-07) Coleman Wasik, Jill
Elevated mercury deposition resulting from human activities has caused wide-spread mercury contamination of aquatic systems around the world. Peatlands are generally considered to be sinks for mercury deposited to the landscape, but also act as biogeochemical reactors wherein inorganic mercury is transformed into bioaccumulative, organic methylmercury (MeHg). Recent, short-term investigations have demonstrated that sulfate deposition alone can increase MeHg production in, and flux from, peatlands through the stimulation of sulfate-reducing bacteria, a group of known mercury methylators. However, over longer periods of time the interaction between the biogeochemical cycles of mercury and sulfur is complicated by variability in climate, hydrology, and sulfur and mercury deposition rates. These complexities were addressed by experimentally altering sulfate-loading to a 2.5-ha peatland in northern Minnesota over eight years. The peatland was initially divided into control and experimental treatments and sulfate was added to the latter three times each field season in simulated rainfall events. Porewaters were sampled before and after each sulfate addition and peat samples were collected five times from sites located within the raised central bog and along the peatland margins. The lagg margin is generally considered to be the primary site of mercury methylation in peatlands. However, sulfate addition caused more pronounced and persistent increases in MeHg in the central bog sites, relative to the margin sites, demonstrating that sulfate delivery to the central bog can greatly expand the areal extent of mercury methylation in peatlands. MeHg production also responded to sulfate release following severe summer drought. The increase was much higher in experimental-treatment sites than in control sites suggesting that the experimental treatment was "primed" to quickly respond to new sulfate inputs. In early 2006 sulfate addition was halted to the upgradient one-third of the original experimental treatment in order to monitor how MeHg production changed as sulfate deposition declined. Although drought appeared to slow the recovery process by increasing sulfate availability and mobilizing MeHg, three years after sulfate additions ceased MeHg in the recovery treatment was significantly lower than in the experimental treatment. This indicates that MeHg production in peatlands formerly affected by elevated sulfate deposition may return to background conditions and highlights the potential benefits that further controls on atmospheric sulfur emissions may have on MeHg production in peatlands and consequent mercury burdens in aquatic foodwebs. The long-term nature of this study allowed for an in-depth exploration of the effects that hydrologic flucutations on mercury cycling in peatlands and calls attention to the potential negative consequences that changing precipitation patterns and evapotranspirative demands may have on MeHg production in these systems.
Information Circular 43. Background Levels of Mercury and Arsenic in Paleoproterozoic Rocks of the Mesabi Iron Range, Northern Minnesota
(Minnesota Geological Survey, 1999) Morey, G.B.; Lively, R.S.
This study was primarily designed to calculate background levels of mercury and arsenic in the Biwabik Iron Formation of the Mesabi range. A second objective was to evaluate the ability of various laboratories to provide analytical data for mercury and arsenic that is reasonably priced yet sufficiently reliable for the purpose of environmental screening. Mercury and arsenic where present in sufficient concentrations are considered to be hazardous substances. They may be naturally occurring, of anthropogenic origin, or some combination thereof. To establish natural background levels and to reduce the possibility of anthropogenic sources, 191 samples of the Biwabik Iron Formation were collected from drill-core sites located south of the Mesabi range (Fig. 1). Ten samples of the overlying Virginia Formation were also analyzed for comparison. Four of the selected sites were jointly drilled by the Minnesota Geological Survey and the Iron Range Resources and Rehabilitation Board (IRRRB) in 1966 and 1967; principal facts for these holes are summarized in Pfleider and others (1968). The fifth site, U.S. Steel 17,700 was drilled sometime in the 1950s, and the core was donated to the Minnesota Geological Survey in the late 1960s; principal facts for it are summarized in Morey and others (1972).
An investigation of mercury dynamics in the pore water of peat columns during experimental warming, freezing, and thawing
(2016-12) Sirota, Jennie
Biogeochemical processes in northern peatland ecosystems are influenced by seasonal temperature fluctuations that are becoming altered with changes in climate. Since mercury is commonly found in peatlands, it is important to understand how temperature impacts mercury dynamics. This study investigates how changes in temperature influences belowground concentrations of total mercury (THg), methylmercury (MeHg), and dissolved organic carbon (DOC) in peat pore waters. Four large peat columns were removed from an ombrotrophic peat bog and exposed to experimental warming, freezing, and thawing. Pore water was sampled across seven depths in the peat columns during the different temperature treatments and analyzed for THg, MeHg, and DOC concentrations. Results indicated that a 2 degree Celsius air temperature increase during warming was not great enough to change the THg and MeHg concentrations in the peat pore water. Freezing resulted in significant decreases in THg and MeHg concentrations and showed evidence of THg exclusion from the ice structure. During thawing, THg concentrations significantly increased while MeHg concentrations remained low. Depth results showed increased bulk density and decreased THg, MeHg, and DOC after 15 cm, which may be indication of the mesotelm layer in the peat columns. These findings fill a gap in peatland research by providing data related to how the freeze-thaw cycle impacts mercury dynamics in peat pore water.
Linking Riparian Flow-Concentration Integration Modeling and HSPF to Predict Background Methylmercury Concentrations in Northeastern Minnesota Streams
(2017-05) Rutelonis, Wes
The St. Louis River Watershed in Northeastern Minnesota has been studied extensively to determine the degree to which sulfate loading from the Mesabi Iron Range affects microbial methylation and bioaccumulation of mercury. Recent studies have identified natural processes unrelated to mining, most often in non-mining portions of the region, as the primary source of methylmercury loading to the river. Here, we further evaluate those contributions by interpreting water chemistry (DOC, THg, MeHg and Fe) from seven St. Louis River tributaries and three main channel sampling sites with the Riparian Flow-Concentration Integration Model (RIM) which was developed for interpretation of stream chemistry in boreal streams in Sweden. This model assumes that riparian wetland soil, the last substrate that porewater encounters before becoming river water, controls the chemistry of local groundwater recharging the river. In locations that contain mixed mining and non-mining contributions, a watershed model (Hydrologic Simulation Program – Fortran: HSPF) was used to estimate the relative groundwater and point source contributions. The RIM approach with soil temperature incorporated as a time-varying parameter is more physically based compared to regression-based methods that have been used previously to interpret stream loads in the region. The comparison of Nash-Sutcliffe model efficiency calculations for both RIM and regression-based models indicate that RIM offers a significant improvement in model predictive power. Since stream flow and temperature are the main drivers, RIM reduces the necessity for widespread, repetitive methylmercury sampling efforts to estimate methylmercury loads.
Mercury concentration and aquatic food web alterations associated with zebra mussel invasion in Minnesota lakes
(2023-08) Link, Denver
Zebra mussels (Dreissena polymorpha) are an invasive species documented in 299Minnesota lakes, with 231 of those lakes managed as walleye fisheries. Many ecological changes are associated with zebra mussel invasion, including increased water clarity, depleted pelagic energy resources, expanded littoral zones, deposition of benthic organic matter causing anoxic sediments, and increased benthic energy reliance of food webs. However, the effects of zebra mussels vary among lakes, and few opportunities exist to examine lake ecosystems and food webs pre- and post- zebra mussel invasion. Furthermore, recent evidence has suggested that Dreissenid mussels may impact contaminant bioaccumulation in higher trophic levels, but these effects have not been well-studied in inland lakes. I took two distinct approaches to understanding zebra mussel impacts on food webs and contaminants in fishes. I combined historic Minnesota statewide mercury monitoring data from 1997-2021 coupled with stable isotope data to provide insight into food web dynamics and mercury concentration alterations with zebra mussel invasion. I found the probability of exceeding the Minnesota safe threshold for safe eating of average sized northern pike (Esox Lucius) and walleye (Sander vitreus) ranged from 60%-70%, with zebra mussel lakes having an increased chance. Specifically, mercury concentrations analyzed using Before-After Control-Impact (BACI) study design increased by 8.2% in northern pike and 15.4% in walleye for invaded lakes, while uninvaded systems were stagnant or decreased. To quantify resource use and community structure, food webs in Leech Lake were analyzed pre- and post- invasion using stable isotope analysis of δ13C and δ15N. Fish community response to zebra mussel invasion varied spatially in Leech Lake. Bays on the western shoreline of Leech Lake with heterogeneous habitat increased niche size by 39.81% and fish in those areas relied more heavily on benthic resources following invasion. In contrast to the western bays and to hypothesized effects of zebra mussels, fish from the main basin of Leech Lake, containing mostly homogenous pelagic resources, decreased in niche size by 32.26% and relied more heavily on offshore resources. Taken together, high mercury concentrations in Minnesota northern pike and walleye are exacerbated in zebra mussel lakes. Food web dynamics are variable within the same lake, suggesting preexisting food web structure and access to benthic resources are important to community resilience with zebra mussel invasion.
Mercury Uptake by Wild Rice Plants in Northern Minnesota
(2015-09) Mahr, Christopher
Mercury (Hg) is a naturally occurring element that can be taken up by microbes, converted into toxic, organic methylmercury (MeHg), and exported into surrounding sediment. The MeHg can then be taken up by plants through rhizofiltration. In Minnesota, 2-4 million lbs of Wild Rice is harvested each year and 1 lb yield 10.5 cups of rice. This study involves sampling surface water, surface sediment, and wild rice grains from 6 lakes on the White Earth Reservation, Fond du Lac Reservation, and 1854 Treaty Area in Minnesota. This was done in order to assess a possible toxicity risk from the consumption of Wild Rice. Finished and unfinished rice grains were analyzed, and all samples were consistent for the six lakes. Using a chronic exposure formula and the highest THg and MeHg concentrations in finished rice grains, it was determined that the toxicity in wild rice grains in Minnesota is extremely low.
Minnesota Pollution Control Agency Wild Rice Sulfate Standard Mesocosm Study: Water, Sediment, and Porewater "Synoptic" Sampling 2013 and 2015
(2017-05-30) Myrbo, Amy; amyrbo@umn.edu; Myrbo, Amy
This dataset represents opportunistic, "synoptic" sampling of 30 experimental mesocosms for chemical parameters. The mesocosm experiments were undertaken by Dr. John Pastor (UMN-Duluth) and the Minnesota Pollution Control Agency (MPCA) to improve the understanding of why wild rice (Zizania palustris, manoomin, psin) is observed to thrive only in waters with low sulfate (SO4), and to contribute to evaluation of Minnesota Rules 7050.0224, promulgated in 1973, which seeks to limit the exposure of wild rice to sulfate concentrations exceeding 10 mg/L.The dataset is now released as manuscripts using it are being published.
Zebra mussel invasion associated with higher reliance on littoral energy sources and higher mercury levels in walleye and yellow perch
(2022-02) Blinick, Naomi
Zebra mussels (Dreissena polymorpha), an aquatic invasive species, shift lake food resources from the pelagic to the littoral zone, while simultaneously altering physical habitat by increasing water clarity. Using stable isotope analysis, we find that walleye (Sander vitreus), a specialist piscivore with strict habitat requirements, and yellow perch (Perca flavescens), a generalist in both diet and habitat, respond similarly to food web and habitat differences in zebra mussel invaded lakes, with significant increases in littoral reliance from ~50% to ~75% for both species. We also report a correlated increase in mercury concentrations in fish tissue, which were 66% higher for adult walleye and 90% higher for adult yellow perch in lakes containing zebra mussels. Considering the importance of these fish for consumption, it is critical that we understand how changes to nutrient cycling and lake food webs ultimately increase toxin concentration in fish consumed by humans.

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