MMSD Watercourse Corridor Study: Contaminants in Water and Sediment Active

During the current 5-year study period for Phase VI (2021-2025) of the Milwaukee Metropolitan Sewerage District (MMSD) Watercourse Corridor Study, the following six topics are being addressed by one or more USGS subprojects:

1.    Ecological Assessments and Trends

2.    Geomorphology and Habitat Studies Related to Stream and Estuary Rehabilitation

3.    Contaminants in Water and Sediment

       a.   Per- and Polyfluoroalkyl Substances (PFAS) Surveillance in Milwaukee Area Streams

       b.   Evaluation of Polycyclic Aromatic Hydrocarbons (PAH) Trends and Estimation of Source Contributions in Stream Sediments

       c.   Characterization of Microplastic Sources in Milwaukee-Area Streams

       d.   Basin-Wide Microbial Investigations and Sewage Loading to the Estuary

       e.   Long-Term Water-Quality Trends in Milwaukee-Area Streams

4.    Green Infrastructure

5.    Nutrient Evaluations

6.    Continuous Real-Time Streamflow

This webpage focuses on topic 3. Contaminants in Water and Sediment.

There are many kinds of potential contaminants contained in water and sediment in our rivers and lakes, and new or “emerging” contaminants are continually being discovered because of improvements in analytical techniques as well as the addition of new types of contaminants. Contaminants can be chemical, physical, or biological. For example, chemical contaminants can include metals and metal-like chemicals (e.g., copper, lead, zinc, and mercury to name just a few), organic/carbon-based chemicals (e.g., DDT, PCBs, PAHs), or nutrients (for example, nitrogen, phosphorus, and sulfur). Physical contaminants can include such things as fine sediment or trash that can also carry attached chemical and biological contaminants. Biological contaminants can include bacteria, viruses, and those that are pathogenic or indicators of potential pathogen presence that may also pose a hazard to humans or animals. Depending on their nature and chemical makeup, contaminants may be associated more with water or with sediment, and the association can change with time because of physical, chemical, or biological interactions with a contaminant. There are a wide variety of natural and anthropogenic contaminant sources with various mechanisms for fate and transport that may be influenced by human activities.

USGS investigations of contaminants in Phase VI include studies of PFAS, PAHs, microplastics, wastewater contamination, as well as modeling long-term trends in water quality.

3a. Per- and Polyfluoroalkyl Substances (PFAS) Surveillance in Milwaukee Area Streams

BACKGROUND

Per- and polyfluoroalkyl substances (PFAS) are commonly used chemicals that have risen to national attention in recent years as chemicals of high priority for potential hazard to human and ecological health.  Use of PFAS chemicals began in the 1940s and have since expanded to use in numerous industrial and commercial processes and products, including items such as clothing, cosmetics, cookware, stain repellants, polishes, paints, coatings, including products such as carpet, leather, textiles, paper, packaging (including food packaging), rubber, plastics, and many others. One common form of environmental contamination has resulted from use of aqueous film forming foams (AFFF) during fire-fighting training exercises, and another form results from incomplete treatment in wastewater treatment systems and subsequent discharge in treated effluent.

There are thousands of different PFAS chemicals used currently. Depending on individual PFAS chemical properties, some do not transform and are extremely persistent as parent compounds, and others (precursors) degrade into compounds that ultimately are very persistent as well. Fate of PFAS in the aquatic environment can vary by chemical property. For example, short chain PFAS (≤ 6 carbon atoms) are commonly found in the water column while long chain PFAS also partition to the sediment and have potential to bioaccumulate.

Exposure to PFAS in area streams has potential to result in adverse effects on aquatic organisms, but given the number of chemicals and relatively recent increase in focus on biological effects of PFAS, there is still much to be learned about the breadth of potential effects. USEPA has recently proposed water quality criteria for two PFAS chemicals (USEPA, 2022a, b), but there are many more that are commonly present in environmental waters with no formal statement on what concentrations may be of concern (Ahrens and Bundschuh, 2014).

OBJECTIVES

The primary objective of this study is to provide a synoptic evaluation of the level of PFAS contamination along major reaches of Milwaukee-area streams during different hydrologic conditions and assess the potential for biological effects based on observed concentrations and various sources of bioeffect data.

APPROACH

As an initial assessment of ambient conditions in Milwaukee-area streams, a surveillance program for PFAS will be conducted under Phase VI of the Corridor Study. This will include sampling of 22 stream locations to represent a longitudinal assessment of PFAS from upstream to downstream in the Milwaukee River, Menomonee River, Kinnickinnic River, Oak Creek, and Root River watersheds and selected tributaries, including all Core Ecology sites regularly monitored for the Corridor Study. For an initial assessment of hydrologic influence, two low-flow period and two periods of increased runoff will be sampled at each site. Results will be used to identify potential areas of concern by comparing to water-quality benchmarks, levels of concern in the ToxCast database, and by comparing to concentrations reported in other areas of Wisconsin and the Great Lakes region.

CONTACT

• Owen Stefaniak (USGS Upper Midwest Water Science Center)

3b. Evaluation of Polycyclic Aromatic Hydrocarbons (PAH) Trends and Estimation of Source Contributions in Stream Sediments

BACKGROUND

Previous USGS/MMSD studies have shown that PAHs likely pose a greater risk to Milwaukee-area stream ecosystems than any other class of organic contaminants monitored, with concentrations in streambed sediment above aquatic toxicity thresholds at most locations (Baldwin and others, 2013). Natural and manmade sources contribute to PAH presence in the environment, including emissions from volcanoes, forest and grassland fires, vehicles and power plants, tire particles, motor oil, crude oil, and coal-tar-based pavement sealcoat (CTS). Comparison of Milwaukee-area streambed sediment samples collected in 2014 with the chemical signatures of various PAHs indicated that CTS is likely the dominant source of the PAHs to Milwaukee area streams (Baldwin and others, 2017). Previously, studies in other areas have also identified CTS as the primary source of PAHs in sediments (Van Metre and others, 2009, 2010; Mahler and others, 2012; Pavlowsky, 2013; Crane, 2014). Considering this body of evidence, many cities, counties, and states, including Dane County, WI (2007), Milwaukee (2017) and more than fifteen communities near Milwaukee (2017-2019), have enacted a ban on the use of high-PAH pavement sealants.

OBJECTIVES

This project aims to evaluate differences in stream sediment PAH content in areas of southern Wisconsin after high PAH (> 1 percent PAHs) pavement sealant bans. The specific objective is to:

1. Maintain a long-term (>10 years) stream sediment monitoring program for tracking PAH concentrations by examining trends in PAHs over time from before the high PAH pavement sealant ban and at least 10 years after implementation bans in the Milwaukee area.

APPROACH

This study has two components to achieve objectives:

Component 1 includes examination of PAH signatures in urban streams of Milwaukee, where bans did not exist before 2017, with Dane County, WI, where a ban of high PAH pavement sealant was implemented in 2007. A total of 21 sites were chosen to represent different levels of urban influence in both regions, including 14 streams in the Milwaukee area and seven streams in Dane County.

Component 2 will include analysis of trends in the PAH signatures from streams with urban influence that were chosen for Component 1. Streams will be sampled at each Component 1 site two times during Phase VI (through 2025). The relative magnitude of PAH presence as well as the composition of the PAH profile will be examined to assess temporal trends.

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CONTACT

• Steve Corsi (USGS Upper Midwest Water Science Center)

3c. Characterization of Microplastic Sources in Milwaukee-Area Streams

BACKGROUND

Microplastics, plastic particles less than 5 mm in diameter, are a known contaminant in marine waters (Thompson and others, 2004; Moore, 2008), and research has begun to define characteristics of microplastics in freshwater systems (Lechner and others, 2014). Several studies have reported microplastic concentrations in rivers and lakes to be as high, or higher, than those in marine environments (Yonkos and others, 2014). Results from a study of Great Lakes tributaries found median concentrations nearly an order of magnitude higher in tributaries than in the Great Lakes (Baldwin and others, 2016).

It is believed that potential pathways which introduce various microplastics to freshwater systems include, but are not limited to, the breakdown of larger plastic litter in urban runoff (e.g., Styrofoam, plastic bags, bottles, wrappers, cigarette butts), wet and dry deposition of microplastics from the atmosphere, and wastewater treatment plant effluent (e.g., synthetic fibers from clothing and textiles, fragments of larger debris, microbeads from personal care products).

To understand potential for management-related reductions in microplastics delivery to the aquatic environment, additional information on microplastics sources and pathways is required. The relative amount of microplastics originating from common urban land uses such as residential and commercial areas, surfaces such as parking lots and roadways, or even from atmospheric deposition are currently not well understood. Developing an understanding of the relative amounts of microplastics from individual sources is a long-term process.

OBJECTIVES

 The objectives of this project are to begin to understand individual sources of microplastics by: 1) defining the predominant types and sources of microplastics to water and sediment in Milwaukee area streams by monitoring selected small watersheds representing specific urban land use types (e.g., commercial, residential), and 2) assessing atmospheric contributions of microplastics to water and sediment by sampling wet and dry atmospheric deposition.

APPROACH

Four sampling locations will be established in small watersheds within the MMSD service area. These sites will be sampled for microplastics at the water surface, as well as the surficial sediment.  Water samples will be collected during both low flow and storm event periods.  In addition, air samples will be collected to assess the atmospheric contribution of microplastics to water and sediment. Results will be analyzed to better understand how common urban land uses influence the sources of different types of microplastics (fibers, fragments, foam, etc.).

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CONTACT

• Pete Lenaker (USGS Upper Midwest Water Science Center)

3d. Basin-Wide Microbial Investigations and Sewage Loading to the Estuary

BACKGROUND

One well-established approach for investigating the composition of dissolved organic matter (DOM) in aquatic systems includes the measurement of optical properties. A fraction of the chemicals included in natural organic matter and anthropogenic substances interact with light, which allows them to be measured by absorbance and fluorescence methods (optical properties). The extent to which light of a certain wavelength interacts with the organic matter reflects the chemical composition of the organic matter, thereby permitting the identification of contaminant sources in environmental waters using optical fluorescence methods. Optical measurements are rapid, inexpensive, reliable, and can be made in the laboratory or field.

Laboratory studies have used fluorescence measurements as indicators of human- and animal-derived wastewater (Bergamaschi et al., 2005). Previous studies have found an association between fluorescence values and the magnitude of wastewater contamination in small creeks and coastal systems (Hartel et al., 2008; McDonald et al., 2006, Hudson et al., 2007).  Additionally, previous studies in the Milwaukee area indicated similar approaches may be useful in relating optical properties to wastewater contamination in area surface water. An analysis indicated that human-associated indicator bacteria (HIB) concentrations, which are specific to wastewater and human sewage, could be estimated by optical properties used in existing field meters at watershed and subwatershed scales (Corsi et al., 2021).  Once relations to specific types of contamination have been established, optical measurements can allow for real time estimation of sewage contamination in surface water environments.  For example, field deployment of existing fluorescence sensors, fluorescent dissolved organic matter (FDOM) and tryptophan-like fluorescence, along with turbidity and streamflow allowed for model development and the estimation of HIB concentrations and the proportion of sewage in the stream at ten-minute intervals for the lower Menomonee River (Lenaker et al., 2023).

OBJECTIVES

The objective is to use currently available optical sensor technology to characterize the dynamics of wastewater contamination in the Milwaukee River, Menomonee River, Kinnickinnic River, and the mouth of the Milwaukee River estuary. Specific objectives are as follows:

1) use fluorescent optical sensor technology to characterize dissolved organic matter dynamics.

2) validate relations between human-associated bacteria (a measure of wastewater contamination) and fluorescent optical signals.

3) provide continuous estimates of wastewater contamination in the three main Milwaukee area rivers and at the mouth of the Milwaukee River estuary over a two-year period.

APPROACH

Initial relations between optical properties and human-associated bacteria (a measure of sewage contamination) were developed with data collected during Phase IV; this provided a preliminary assessment of the specific optical signals that will be predictive of wastewater contamination in this area. The practicality of using in situ optical measurements as tools for continuous real-time assessment of human wastewater contamination in the Menomonee River watershed was evaluated in Phase V.  During Phase V sensors were deployed with these fluorescent signals to provide a continuous estimate of wastewater contamination in the lower Menomonee River. In Phase VI, fluorescent optical sensors will be deployed again on the lower Menomonee River, in addition to deployments on the Kinnickinnic and Milwaukee Rivers and at the mouth of the Milwaukee River estuary. Water samples will be collected and analyzed for optical properties of water (fluorescence, absorbance, and dissolved organic carbon) and human-associated bacteria over a range of flow conditions throughout different seasons in all three locations and the Milwaukee River estuary. Results will be used to estimate human-associated indicator bacteria and the proportion of sewage within the stream. The goal for this project is to deploy and use these fluorescent sensors at fixed locations to capture the timing and magnitude of wastewater pulses in the stream.

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CONTACTS

• Pete Lenaker (USGS Upper Midwest Water Science Center)
• Steve Corsi (USGS Upper Midwest Water Science Center)

3e. Long-Term Water-Quality Trends in Milwaukee-Area Streams

BACKGROUND

The past 40 years have seen a multitude of changes in the Milwaukee area.  In addition to substantial landscape and stream alterations occurring during this time, operation of the Deep Tunnel commenced in 1993. These changes have the potential to influence water quality in Milwaukee area watersheds. MMSD, USGS, and other agencies have collected water quality and streamflow information for many water quality parameters in multiple streams over this period. USGS has developed advanced statistical techniques to detect temporal trends in long-term water-quality datasets such as these, while accounting for variable flow and seasonality (Hirsch, Moyer, and Archfield, 2010, Hirsch and De Cicco, 2014). These statistical techniques as well as numerous graphical visualization options are included in the Exploration and Graphics for RivEr Trends software package (EGRET; https://github.com/USGS-R/EGRET/wiki).

EGRET has been used to assess trends in water quality during previous phases of the Corridor Study: Phase IV efforts characterized long-term trends in chloride (Corsi and others, 2015); Phase V efforts characterized long-term trends in fecal coliform, total phosphorus, ammonia, biochemical oxygen demand, and total suspended solids (publication in prep). In Phase VI, we again plan to assess trends for multiple water-quality parameters.  We will reassess trends in chloride, with an emphasis on characterizing the changes have occurred in the 10 years since our last study.  We will also characterize trends for other parameters that MMSD identifies as high priorities for their future planning efforts.  

Overall, further application of these techniques to water-quality parameters in the Milwaukee area will provide valuable insight into patterns of water-quality change, possible causes of those changes, and will help inform additional decisions related to watershed management actions in the coming years.

OBJECTIVES

The overall objective of this study is to examine historical data for streams in the Milwaukee area to identify patterns of change in water quality and provide this information to stakeholders such as MMSD, other watershed managers, and policy makers to help inform future watershed management decisions. 

APPROACH

Existing water-quality data for chloride and other high-value parameters in the Milwaukee area will be mined and assessments will be completed to determine whether there are sufficient data for evaluation of temporal trends.  Sites around the Milwaukee area with adequate data records will be selected, and data will be analyzed with the Weighted Regressions on Time Discharge and Season (WRTDS) model contained within the EGRET software package to examine changes in water quality over extended periods of time.  Results from these studies will be published in scientific publications and presented to stakeholders.

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CONTACTS

• Michelle Nott (USGS Upper Midwest Water Science Center)