51����

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• • Sam Krueger was featured in a report titled: “” by Freshwater Collaborative of Wisconsin.
  • August 7, 2025: Ms. Rahmah Sajid completed her ACS Project-SEED summer internship and presented her research on “Variations in chemical composition of DOM released from polyester and PVC microplastics under different pH and leaching conditions” at the symposium of the 2025 ACS Project-SEED Program at 51����.
  • Aug-02-2025: Dr. Shimaa Kteeba’s manuscript titled: “UV-induced release and characterization of dissolved organic matter from disposable face mask layers and polypropylene’ has been accepted for publication in ” (see link at or ). Congratulations Shimaa!
  • Molly Fox-Kincaid completed her summer internship and presented her research project on “Influence of pH and Leaching Conditions on the Chemical Composition of Microplastic-Derived Dissolved Organic Matter” at the 2025 Summer Research Symposium, Madison (August 1, 2025).
  • Dr. Guo attended the the 2025 Goldschmidt Meeting during 6-11 July 2025 in Prague, Czech Republic, and presented a paper on “Depositional history of PFAS in the bay of Green Bay in Lake Michigan over the last 80 years”.
  • Ms. Samantha Krueger received the 2025-2026 Graduate Student Excellence Fellowship award from 51����’s Graduate School. Congratulations, Sam!
  • Ms. Samantha Krueger attended the ACS Great Lakes Region Meeting during June 4-6, 2025. Appleton, Wisconsin, and presented a paper on “Chemical Characterization of Dissolved Organic Matter Released from Biodegradable Polyhydroxyalkanoate Microplastics”.
  • Ms. Wenxin Zhang attended the 68th Conference in Milwaukee, WI, and presented a paper on “Partitioning of PFAS between dissolved and colloidal phases in freshwater environments“, authored by  Krueger, S.J., Zhang, W., Kteeba, S.M., Wang, Y. and Guo, L.
  • Dr. Guo chaired a session on “Fate and Transport of Microplastics, PFAS, and other Emerging Contaminants” during the 68th Conference in Milwaukee, WI. Co-Chairs are Prof.. John Lenhart (OSU) and Prof. Liz Minor (UMN-Duluth). Dr. Guo also presented a paper on “Variations of PFAS in Milwaukee estuary sediments: insights into contamination history and sources”.
  • Ms. Samantha Krueger attended the 68th Conference in Milwaukee, June 2-6, 2025, and presented a paper titled: “Pollution history of toxic metals and metalloids in the Bay of Green Bay sediments” (with coauthors including Wahl, T., Klump, J.V., and Guo, L.).
  • Dr. Shimaa Kteeba attended the 68th Conference in Milwaukee, June 2-6, 2025, and presented a paper titled: “Impacts of Leaching Methods on the Chemical Properties of Dissolved Organic Matter released from PVC Microplastics”.
  • Ms. Samantha Krueger attended the 2025 Society for Freshwater Science meeting during May 18-22, 2025 in San Juan, PR and presented a paper titled: “Spatial and vertical variations in heavy metal concentrations in Green Bay sediments”.
  • from visited Guo’s Lab on February 10, 2025 and gave a presentation on “ in Wisconsin surface water” in SFS’s Colloquium.
  • Ms. Kaitlyn Suchomel joined Guo’s Lab as a undergraduate research fellow (SURF award recipient) in Feb 2025. Welcome Kait!
  • Mr. Miles Carlson joined Guo’s Lab as a undergraduate research fellow (SURF award recipient) in Feb 2025. Welcome Miles!
• 2024
  • Dr. Guo attended the 2024 AGU Fall Meeting (December 9-13, 2025) in Washington DC.
  • Ms. Sam Krueger has been awarded the 2024-25 Mick A. Naulin Foundation Research Award  for $6,500. Congratulations Sam!
  • A long-overdue manuscript titled: “A comparative study of optical and size properties of dissolved organic matter in the lower Mississippi River and Pearl River“, led by former students Zhengzhen Zhou and Hui Lin, has been accepted for publication in Marine Chemistry (see link at ).
  • Dr. Shimaa Kteeba’s manuscript titled: “Photodegradation processes and weathering products of microfibers in aquatic environments” submitted to , has been accepted for publication (see link at or ). Congratulations Shimaa!
  • Dr. Guo attended the in Denver, Colorado (August 18-22, 2024), and presented a paper titled: “PFAS binding to dissolved organic matter released from microplastics ()” in the session, Division of Environmental Chemistry.
  • Dr. Shimaa Kteeba presented a paper titled: “Chemical and optical characterization of dissolved organic matter released from Disposable Face Masks under UV-irradiation ()” during the in Denver, Colorado (August 18-22, 2024).
  • Prof. (Distinguished Professor from Department of Oceanography, National Sun Yat-sen University, Taiwan) visited Guo’s Lab for collaborative research on oceanic DOM, microplastics, and other topics.
  • Dr. Peng Lin’s manuscript titled:”Chemical speciation, reactivity, and long-term burial of sedimentary phosphorus in a seasonally hypoxia-influenced freshwater estuary” has been accepted for publication in . (Vol. 948, art# 174957; ).
  • Dr. Guo co-authored an article published in along with and : “Lead water pipes created a health disaster in Flint, but replacing them with cheap PVC plastic – as many cities are doing – carries hidden costs” (see for the article).
  • Ms. Nadalee Thao joined Guo’s lab on June 17, 2024 as a summer intern of program from . Welcome Nadalee!
  • Ms. Bridget Wilson joined Guo’s lab as a Freshwater@UW 2024 summer intern. She will study the fate and transport of emerging contaminants. Welcome Bridget!
  • Ms. Samantha Krueger joined Guo’s lab in May 2024 as a graduate student. She will conduct research on the fate and transport of emerging contaminants in aquatic environments. Welcome Sam!
• 2023
  • Dr. Guo has been included in Stanford University’s list of “” scientists every year since 2020.
  • Mitch Schutte (Master student) published his research article entitled:”” in (Vol 911, article# 168616. ). Congratulations Mitch!
  • August 16, 2023: Freshwater Collaborative awards 51���� nearly $1 million for six research and education projects.
  • July 27, 2023: Dr. Hui Lin’s manuscript titled: “Distinct variations in fluorescent DOM components along a trophic gradient in the lower Fox River-Green Bay as characterized using one-sample PARAFAC approach” has been accepted for publication in .
  • Mr. Samuel Broadnax (Master student) will work as a Research Assistant in Guo’s Lab starting in the fall 2023 semester. Welcome Sam!
  • Ms. Margaret Sollberger and Mr. Darwin Weidert joined us on July 6, 2023 as undergraduate research fellows supported by UR@51����.  They will work on spectroscopic characterization of plastic-derived dissolved organic matter.
  • Ms. Nadalee Thao joined us as a summer intern of program from on June 19, 2023. She is from Milwaukee . Welcome Nadalee!
  • Ms. Jena Choi joined us as a undergraduate research fellow from 51����’s SURF program on June 5, 2023. She also works as a research assistant in our lab. Welcome Jena!
  • Mr. Sean Gibbs, a 51����’s Undergraduate Research Fellow in Guo’s Lab, received at the 2023 51���� Undergraduate Research Symposium for his poster titled: “Photochemical Degradation of Disposable Face Masks and Polypropylene in Aquatic Environments”. Congratulations!
  • Dr. Dan Li’s manuscript titled:”Comparison of molecular weight distributions and size-dependent optical properties among model and reference natural dissolved organic matter” has been accepted for publication in
• 2022
  • 29 June 2022: Preserving permafrost ecosystems is crucial to humanity: faster decarbonization is essential: International experts call for decisive action to protect global permafrost. According to a study published this week in , rapid warming is causing cascading changes in permafrost regions that are threatening biodiversity, the stability of global climate, and the wellbeing of over 1.5 billion people. This study was initially conceived by both Dr. Benjamin Abbott, a professor at Brigham Young University, and Dr. Laodong Guo, a professor at University of Wisconsin-Milwaukee and an Associate Editor of – Biogeocheical Dynamics. A team of 33 international experts summarized more than 200 recent studies about how climate change and permafrost are interacting. The science and policy experts focused on four key permafrost regions: the Arctic Ocean, the Boreal Forest, the Arctic Tundra, and the Tibetan Plateau. Together called the permafrost domain, these areas are especially vulnerable to climate change because of their dependence on ice. This is a problem because they are warming three-times faster than the global average, with many regions already 2 to 5 degrees Celsius warmer than before the Industrial Revolution (see details in Abbott et al. Front. Environ. Sci., 29 June 2022, ).
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  • Mr. Sean Gibbs and Ms.Tia Walker joined us as 51����’s summer 2022 SURF fellows. They will work on assessing the abundance and chemical speciation of nutrients (N and P) in a coastal lagoon. Welcome Sean and Tia!
  • Ms. Princy Patel, a summer intern student of program from , joined us on 13 June 2022. Welcome Princy!
  • Dr. Shimaa Kteeba joined us as a postdoc in May 2022.  She will work on several research projects and help supervise summer interns and undergraduate and graduate students in our lab. Welcome back Shimaa!
  • Hui Lin’s paper titled: “Dynamic changes in size-fractionated dissolved organic matter composition in a seasonally ice-covered Arctic river” has been published in (see link at ).
  • Hui receives the 51���� Distinguished Dissertation Fellowship Award. Congratulations, Hui!
  • Mr. Hui Lin’s paper entitled: “Variations in colloidal DOM composition with molecular weight within individual water samples as characterized by flow field-flow fractionation and EEM-PARAFAC analysis” has been published in (see link at ).
  • Dr. Dan Li’s paper from her work at Guo and Carvan Labs at 51����: “Mitigative effects of natural and model dissolved organic matter with different functionalities on the toxicity of methylmercury in embryonic zebrafish” has been published in (see ).
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  • Guo delivered a seminar/presentation during his visit to Dr. Guebuem Kim’s Lab at the Seoul National University (Seoul, South Korea) and Dr. Kyung-Hoon Shin’s Group at Hanyang University (Anshan, South Korea) during January 2019.
  • Dr. Bin Yang has returned to his home institute, Qinzhou University, after working at 51���� for one year. His research here was on the molecular weight distribution of dissolved organic phosphorus and the biogeochemical cycling in river and estuarine environments.
  • Guo attended the XMAS-IV meeting in Xiamen during January 6-9, 2019, co-chaired a session on the “Biogeochemistry of organic matter and associated elements along the river-estuary-ocean continuum” and gave an oral presentation during the meeting.
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  • Professor Xuchen Wang and his colleagues from Ocean University of China visited Guo’s Lab at 51���� during their stay at NEC in Wisconsin.
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  • Dr. Changyou Wang, a new visiting scholar from Nanjing, China, arrived at 51���� in August 2018.  He will conduct collaborative research in the School of Freshwater Sciences (Changyou and his wife).
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  • Guo visited Dr. Lei Gao at East China Normal University in July 2018 and gave a talk titled “Variations in molecular-size and composition of heterogeneous dissolved organic matter in estuarine environments”.
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  • Dr. Miao Liu, from Chinese Academy of Sciences, and Dr. Wei Zhang, from Shenyang Agricultural University, visited School of Freshwater Sciences. They also gave a talk introducing their research.
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  • Dr. Huacheng Xu’s series papers have been published in ( x4, see also graphic abstracts below), (x1), and (x1), during 2018.
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  • Dr. Shimaa Kteeba’s 2nd manuscript entitled “Exposure to ZnO nanoparticles alters neuronal and vascular development in zebrafish: Acute and transgenerational effects mitigated with dissolved organic matter.” has been published in , 242: 433-448, doi:1.  Congratulations Shimaa!
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  • Steve’s (Stephen DeVilbiss) recent paper entitled: “Excretion of organic matter and nutrients from invasive quagga mussels and potential impact on carbon dynamics in Lake Michigan” published in the (43, 79-89) was highlighted in NOAA Wisconsin website (see the ).

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  • Ms. Shimaa Kteeba’s manuscript entitled “Zine oxide nanoparticle toxicity in embryonic zebrafish: Mitigation with different natural organic matter” has been published in , 230, 1125–1140. doi:. (see also graphical abstract below).  Congratulations Shimaa!
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  • Dr. Guo participated in the Frontiers in Earth Science / 2017 Annual Meeting in Senzhen, China.  His presentation was on “Simultaneous separation and characterization of heterogeneous dissolved organic matter in aquatic environments”.
  • Dr. Huacheng Xu’ manuscript entitled: “Molecular size-dependent abundance and chemical composition of dissolved organic matter in river, lake and sea waters” has been published in (see graphical abstract below; doi:
    • 

• • Dr. Guo visited , Qingdao, in April 2017 and gave a talk in the Workshop on Marine Chemistry Frontiers.

• • Mr. Stephen DeVilbiss’s manuscript entitled:”Excretion of organic matter and nutrients from invasive quagga mussels and potential impact on carbon dynamics in Lake Michigan” has been accepted for publication in . (43, 79-89. )
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  • Dr. arrived at 51���� on December 11, 2016.  He is a Research Professor at , Chinese Academy of Sciences, and will work as a visiting scholar for 12 months in the School of Freshwater Sciences.  Welcome Dr. Gao!
  • Dr. Peng Lin’s manuscript entitled:”Do invasive quagga mussels alter CO2 dynamics in the Laurentian Great Lakes? ” has been accepted for publication in , (full citation: Scientific Reports, 6, article number: 39078. doi: ).
  • Dr. , from Center for Environmental Nanoscience and Risks at the University of South Carolina, visited Guo Lab and delivered an invited seminar in the School of Freshwater Sciences, on Noverber-10, 2016, entitled:” Environmental fate and behavior of engineered nanoparticles”,
  • Mr. Hui Lin, a new PhD student in Guo lab, arrived at SFS/51���� right before the fall semester.  Welcome Hui!
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  • Dr. Guo presented a talk entitled: “Chemical speciation and transformation of phosphorus in seasonally hypoxic Green Bay” during the 2016 Asia Oceania Geosciences Society (AOGS) meeting in Beijing, China, during August 1-5, 2016.  He also visited Xiamen University and the 2nd and 3rd Institute of Oceanology, SOA, and gave an invited seminar at each institute.
  • Mr. Tarek Teber has successfully defended his thesis entitled: “Seasonal and Spatial Variations in Chemical Composition and Fluxes of Dissolved Organic Matter and Nutrients in the Lower Milwaukee River“.  Congratulations Tarek!
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  • Dr. Zhijun Gong and his colleagues from Chinese Academy of Sciences, Nanjing Institute of Geography and Limnology, arrived at Milwaukee on July 9.  They will visit 51���� School of Freshwater Sciences and other Institutes/Facilities during their stay in Milwaukee.
  • Dr. Guo presented a keynote talk entitled: “Size and chemical characterization of dissolved organic matter across the river-lake and river-sea interfaces using FlFFF coupled with fluorescence EEMs” at the at Yokohama, Japan, during June 26-July 1, 2016.
  • Dr. Guo visited Professor Kyung-Hoon Shin’s lab at Han-Yang University, South Korea, for collaborative research and delivering a seminar in the Department of Marine Science.
  • Shimaa and Steve attended the 2016 ASLO Aquatic Science Meeting in Santa Fe, NM during June 5-10.  Shimaa presented a poster entitled “” and Steve gave a oral presentation entitled: ““.
  • Professor Chin-Chang Hung, from National Sun Yet-sen University, Taiwan, arrived at School of Freshwater Sciences/51���� on June 2, 2016.  He will visit Dr. Guo lab and conduct collaborative research.
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• • Steve’s manuscript entitled: “Spatiotemporal variations in the abundance and composition of bulk and chromophoric DOM in seasonally hypoxia-influenced Green Bay, Lake Michigan” has been accepted for publication in (doi: ). Congratulations Steve!
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• • Dr. Wenzhi Liu, a visiting scientist from Chinese Academy of Sciences,  arrived at 51���� on April 28.  He will work in  Guo Lab for one year.  Welcome Wenzhi!
  • Mr. Stephen DeVilbiss has successfully defended his thesis entitled: “Characterization of dissolved organic matter and its interactions with invasive quagga mussels in Lake Michigan”, on April-22, 2016.  Congratulations Steve!
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• • Dr. Zhengzhen Zhou’s manuscript entitled: “Characterization of bulk and chromophoric dissolved organic matter in the Laurentian Great Lakes” has been accepted for publication in . doi: .
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• March 2016
  • Dr. Huacheng Xu  arrived at 51���� in March.  He will work in SFS as a visiting scientist for 12 months.  Welcome Huacheng!
  • Dr. Zhengzhen Zhou’s manuscript entitled: “Colloidal size spectra, composition and estuarine mixing behavior of DOM in river and estuarine waters of the northern Gulf of Mexico” has been published in , 181, 1-17.�� .
  • Dr. Peng Lin’s manuscript entitled: “Dynamic changes in abundance and chemical speciation of dissolved and particulate phosphorus across the river-lake interface in southwest Lake Michigan ” has been published in (current impact factor: 3.79), 61, 771-189, doi: .
  • Steve DeVilbiss and Guo participated in a public outreach event, the , organized by Liz Sutton at SFS/51���� last weekend (Oct-24, 2015).
  • Dr. ‘s manuscript entitled: “Abundance, stable isotopic composition, and export fluxes of DOC, POC and DIC from the Lower Mississippi River during 2006-2008” is now accepted for publication in .
  • Dr. Guo delivered an invited talk on “A snapshot of the state of health of the Laurentian Great Lakes” in the of the American Chemical Society () on October 15, 2015.
  • Dr. Guo gave an invited seminar in the and Biochemistry at the on September 25, 2015.  His presentation was on “Characterization of colloidal organic matter using flow field-flow fractionation coupled with fluorescence EEM techniques”.  He also visited the at UMD (09/24/2015).
  • Dr. Peng Lin’s manuscript entitled: “Dynamics of dissolved and particulate phosphorus influenced by seasonal hypoxia in Green Bay, Lake Michigan (DOI: )” was accepted for publication in (current impact factor: 4.09).  Congratulations!
  • A sampling cruise has been scheduled for Friday, Sept-18, 2015, on board the R/V Neeskay to Lake Michigan.  Activities will include collecting box cores, quagga mussels, large volume water for ultrafiltration, in addition to routine sampling for nutrients, CDOM/FDOM and others .
  • Professor Dr. Lars , Director of Cornell Biological Field Station, Cornell University, visited Guo Lab after their sampling cruise on board the R/V to the Great Lakes (09/16/2015).
  •   Ms. Shimaa Kteeba, a Visiting PhD student from Egypt, will extend her stay for one more year from October-2015 to Sept-2016 in the School of Freshwater Sciences at 51���� (09/15/2015).
  • Dr. Jianyu Ni’s manuscript entitled: “Distribution, source and chemical speciation of phosphorus in surface sediments of the central Pacific Ocean” has been published in “, Vol. 105: 74–82, doi: .(09/09/2015)
  • Our new high resolution sector field ICP-MS (Thermo Scientific Element 2) has been installed and ready for use.  A laser ablation component will be added on in September 2015.

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