Dark field microscope from the manuscript, " a) A dark-field image of 1.5 µm PS LMMPs on a 0.4 μm PCTE membrane sensor. b) A Raman map of PS acquired by tracking its Raman band at 996 cm-1
Sarah E Janssen
Sarah Janssen is an isotope geochemist working in the Mercury Research Lab (MRL) located within the Upper Midwest Water Science Center.
She has a PhD in environmental chemistry from Rutgers University and a bachelor’s in chemistry from
University of the Sciences in Philadelphia. Her work focuses on the application of stable isotope techniques for understanding sources and transformations of mercury (Hg) in the environment. Her research interests include Hg cycling in contaminated ecosystems, the investigation of microbial Hg transformations using stable isotopes, and development of analytical methods to improve Hg isotope measurements.
Current Projects
- Mercury Cycling and Source Identification in the St Louis River Estuary MN/WI (collaboration with US EPA and Minnesota Pollution Control Agency)
- Mercury Isotope Fractionation during Microbial Uptake and Transformations of Hg (collaboration with Rutgers University and University of Ottawa)
- Method Development for the Pre-concentration of Waters and Low Concentration Environmental Samples for Mercury Isotopic Analysis
Science and Products
Innovative Sensor Development for Detecting Low-Micrometer Plastics in Freshwater Systems
Plastic pollution is a significant global issue in aquatic ecosystems, with low-micrometer plastics (LMMPs) posing particular risks owing to their small size and prevalence in various environments. The U.S. Geological Survey and collaborators are developing an innovative sensor to detect and analyze LMMPs in freshwater systems, achieving rapid and accurate results without the need for additional...
Wildfires Increase Mercury Concentrations in Headwater Streams
The U.S. Geological Survey is researching the effect of wildfires on the release of stored mercury from forest watersheds and subsequent transport, methylmercury formation, and bioaccumulation post-fire. Wildfires not only alter the re-release of mercury into the environment but also affect its reactivity and availability to the food web, complicating predictions of mercury exposure risks to...
Mercury Isotope Ratios used to Determine Sources of Mercury to Fish in Northeast U.S. Streams
Mercury isotope analyses were used to distinguish different sources of mercury to fish in 23 streams along a forested-rural to urban-industrial land-use gradient in the Northeastern United States. The use of mercury isotope measurements in fish tissue allow for distinguishing different sources of mercury that are bioaccumulating into the food web. Mercury isotope signatures in fish in forested...
Mercury studies
The USGS Mercury Research Lab is a national leader in advancing mercury research and science, specializing in low-level mercury speciation and isotope analysis and mercury-source fingerprinting. The MRL leads national cutting-edge collaborative studies, including state-of-the-art sample analysis, methods development for field and lab procedures, and data interpretation and dissemination.
Dark field microscope image, microplastics
Dark field microscope from the manuscript, " a) A dark-field image of 1.5 µm PS LMMPs on a 0.4 μm PCTE membrane sensor. b) A Raman map of PS acquired by tracking its Raman band at 996 cm-1
Sarah Janssen presents at Great Lakes AOC Conference 2023 in Green Bay
Sarah Janssen presents at Great Lakes Areas of Concern Conference 2023 in Green Bay, Wisconsin.
Sarah Janssen presents at Great Lakes Areas of Concern Conference 2023 in Green Bay, Wisconsin.
USGS scientist using the Raman microscope to identify and characterize microplastics
Michael Tate using the Raman microscope to identify and characterize microplastics at the Upper Midwest Water Science Center
Michael Tate using the Raman microscope to identify and characterize microplastics at the Upper Midwest Water Science Center
Filtered plastics from surface water in Madison, WI.
Filtered plastics from surface water in Madison, WI. This photo was taken at UMID for microplastic analysis and method development.
Filtered plastics from surface water in Madison, WI. This photo was taken at UMID for microplastic analysis and method development.
Wildfire burn site located in Oregon
This is a landscape photo of a wildfire burn site located in Oregon, USA. Photo taken in November of 2021.
This is a landscape photo of a wildfire burn site located in Oregon, USA. Photo taken in November of 2021.
Field collection of surface soils from burned watershed
Field collection of surface soils from a burned watershed by USGS Contaminant Ecology Research Laboratory
Field collection of surface soils from a burned watershed by USGS Contaminant Ecology Research Laboratory
Nippon mercury analyzer for sediments and fish
Nippon mercury analyzer for sediments and fish.
Nippon mercury analyzer for sediments and fish.
MC-ICP-MS used for mercury stable isotope analyses
MC-ICP-MS used for mercury stable isotope analyses.
MC-ICP-MS used for mercury stable isotope analyses.
Graduate student performing mercury uptake studies in plankton
Graduate student, Grace Armstrong, performing mercury uptake studies in plankton at Mercury Research Laboratory, Middleton, Wisconsin.
Graduate student, Grace Armstrong, performing mercury uptake studies in plankton at Mercury Research Laboratory, Middleton, Wisconsin.
Internal look at the MC-ICP-MS flight tube when magnet is removed
Internal look at the MC-ICP-MS flight tube when magnet is removed.
Internal look at the MC-ICP-MS flight tube when magnet is removed.
Assessing soil sampling locations at the Badger Army Ammunition Plant
Scientist in field assessing soil sampling locations at the Badger Army Ammunition Plant site in Sauk County, WI.
Scientist in field assessing soil sampling locations at the Badger Army Ammunition Plant site in Sauk County, WI.
Mobile water isotope collection on shore of Mobile River, Alabama
Scientists collecting water samples for mercury isotope analysis in the Mobile River, Alabama.
Scientists collecting water samples for mercury isotope analysis in the Mobile River, Alabama.
Science and Products
Innovative Sensor Development for Detecting Low-Micrometer Plastics in Freshwater Systems
Plastic pollution is a significant global issue in aquatic ecosystems, with low-micrometer plastics (LMMPs) posing particular risks owing to their small size and prevalence in various environments. The U.S. Geological Survey and collaborators are developing an innovative sensor to detect and analyze LMMPs in freshwater systems, achieving rapid and accurate results without the need for additional...
Wildfires Increase Mercury Concentrations in Headwater Streams
The U.S. Geological Survey is researching the effect of wildfires on the release of stored mercury from forest watersheds and subsequent transport, methylmercury formation, and bioaccumulation post-fire. Wildfires not only alter the re-release of mercury into the environment but also affect its reactivity and availability to the food web, complicating predictions of mercury exposure risks to...
Mercury Isotope Ratios used to Determine Sources of Mercury to Fish in Northeast U.S. Streams
Mercury isotope analyses were used to distinguish different sources of mercury to fish in 23 streams along a forested-rural to urban-industrial land-use gradient in the Northeastern United States. The use of mercury isotope measurements in fish tissue allow for distinguishing different sources of mercury that are bioaccumulating into the food web. Mercury isotope signatures in fish in forested...
Mercury studies
The USGS Mercury Research Lab is a national leader in advancing mercury research and science, specializing in low-level mercury speciation and isotope analysis and mercury-source fingerprinting. The MRL leads national cutting-edge collaborative studies, including state-of-the-art sample analysis, methods development for field and lab procedures, and data interpretation and dissemination.
Dark field microscope image, microplastics
Dark field microscope from the manuscript, " a) A dark-field image of 1.5 µm PS LMMPs on a 0.4 μm PCTE membrane sensor. b) A Raman map of PS acquired by tracking its Raman band at 996 cm-1
Dark field microscope from the manuscript, " a) A dark-field image of 1.5 µm PS LMMPs on a 0.4 μm PCTE membrane sensor. b) A Raman map of PS acquired by tracking its Raman band at 996 cm-1
Sarah Janssen presents at Great Lakes AOC Conference 2023 in Green Bay
Sarah Janssen presents at Great Lakes Areas of Concern Conference 2023 in Green Bay, Wisconsin.
Sarah Janssen presents at Great Lakes Areas of Concern Conference 2023 in Green Bay, Wisconsin.
USGS scientist using the Raman microscope to identify and characterize microplastics
Michael Tate using the Raman microscope to identify and characterize microplastics at the Upper Midwest Water Science Center
Michael Tate using the Raman microscope to identify and characterize microplastics at the Upper Midwest Water Science Center
Filtered plastics from surface water in Madison, WI.
Filtered plastics from surface water in Madison, WI. This photo was taken at UMID for microplastic analysis and method development.
Filtered plastics from surface water in Madison, WI. This photo was taken at UMID for microplastic analysis and method development.
Wildfire burn site located in Oregon
This is a landscape photo of a wildfire burn site located in Oregon, USA. Photo taken in November of 2021.
This is a landscape photo of a wildfire burn site located in Oregon, USA. Photo taken in November of 2021.
Field collection of surface soils from burned watershed
Field collection of surface soils from a burned watershed by USGS Contaminant Ecology Research Laboratory
Field collection of surface soils from a burned watershed by USGS Contaminant Ecology Research Laboratory
Nippon mercury analyzer for sediments and fish
Nippon mercury analyzer for sediments and fish.
Nippon mercury analyzer for sediments and fish.
MC-ICP-MS used for mercury stable isotope analyses
MC-ICP-MS used for mercury stable isotope analyses.
MC-ICP-MS used for mercury stable isotope analyses.
Graduate student performing mercury uptake studies in plankton
Graduate student, Grace Armstrong, performing mercury uptake studies in plankton at Mercury Research Laboratory, Middleton, Wisconsin.
Graduate student, Grace Armstrong, performing mercury uptake studies in plankton at Mercury Research Laboratory, Middleton, Wisconsin.
Internal look at the MC-ICP-MS flight tube when magnet is removed
Internal look at the MC-ICP-MS flight tube when magnet is removed.
Internal look at the MC-ICP-MS flight tube when magnet is removed.
Assessing soil sampling locations at the Badger Army Ammunition Plant
Scientist in field assessing soil sampling locations at the Badger Army Ammunition Plant site in Sauk County, WI.
Scientist in field assessing soil sampling locations at the Badger Army Ammunition Plant site in Sauk County, WI.
Mobile water isotope collection on shore of Mobile River, Alabama
Scientists collecting water samples for mercury isotope analysis in the Mobile River, Alabama.
Scientists collecting water samples for mercury isotope analysis in the Mobile River, Alabama.