The goal of this research is to better understand the ecological significance and aquatic community impairments resulting from exposures to trace organic chemicals (TOrC) (including pharmaceuticals and personal care products) below municipal wastewater treatment plant discharges in freshwater streams. We are creating a decision-making screening framework for utility managers to assess the likelihood of ecologically significant TOrC exposures from their discharges in the context of multiple stressors which usually occur in these receiving waters. A field-based Tier 2 assessment approach is being evaluated to test the effectiveness of the screening framework and assist in discerning significant impairments. This approach includes field studies at three sites in the U.S., assessing chemical loadings, habitat quality, benthic macroinvertebrate and fish community metrics, endocrine disruptor and other biochemical and genomic responses in caged fish, and in situ fractionation/organism exposures to a range of chemical classes using a novel in situ Toxicity Identification Evaluation approach (see preliminary system in Burton and Nordstrom 2004ab).
Our WERF project is applying site screening tools to evaluate the ecological effects of trace organics, such as personal care products and pharmaceutical’s, on aquatic environments. In situ TIE (Toxicity Identification and Evalutation) devices (above photo) will be used downstream of WWTP discharges to selectively fractionate which chemical groups the aquatic organisms are exposed to. This will help us identify which dominant toxicant classes have the biggest impacts on individual or population responses. It is extremely challenging to establish causality between any particular chemical exposures and adverse biological effects in most contaminated waters and sediments, due the multitude of chemicals present. This makes it often impossible to determine which chemicals are problematic in receiving aquatic ecosystems and thereby confound attempts to regulate and/or manage the sources of those chemicals. The in situ Toxicity Identification Evaluation system was created to separate out chemical classes of compounds that are frequently linked to adverse biological effects (nonpolar organics, metals and ammonia). The approach proved to be more sensitive that the U.S. EPA laboratory based TIE approach and less prone to manipulation artifacts (Burton and Nordstrom 2004a,b). This diagnostic tool is being modified to a more robust system that can be deployed in a wide range of systems and better separate differing types of organic chemicals. It is being used in a range of ecosystems and should improve causality determinations.Funding is provided by the Water Environment Research Foundation (WERF).
The Nickel Producer Environmental Research Association (NiPERA) has funded us to evaluate the usefulness of a wide-range of assessment methods to determine when nickel is biologically available, toxic to organisms, and impairing benthic communities below Ni mining operations. We will conduct a field, weight-of-evidence based assessment of water and sediment quality in the Thompson mine area of northern Manitoba. This mining operation is unique to most, in that Ni is the primary metal and other co-occurring metals are at low concentrations. This will allow for a strong causality linkage between Ni exposures and biological responses. A gradient-study design will be used consisting of a range of physicochemical characterizations to document exposures to both caged organisms and indigenous communities, assessing a multitude of biological endpoints. The results of this research will aid future evaluations of mining impacts to better characterize ecological impairments and their significance.
Collaborators: Dr. David Costello, Kent State University
There have been substantial improvements in how we model sediment metal bioavailability from the inclusion of complexing agents (i.e., sulfide, organic carbon) yet experimental conditions often lead to overestimates of toxicity. We are setting out to develop laboratory exposure scenarios that best replicate metal contamination in stream sediments. Our goal is to create a model that accounts for (1) the increased bioavailability associated with using metal salts for laboratory amendments and (2) scavenging of heavy metals by Fe and Mn oxides that are common found in natural stream sediments. Ultimately, we hope to improve predictions of toxicity due to metal contamination to better inform restoration efforts.
Collaborators: Dr. David Costello, Kent State University
Recent studies have demonstrated that plastic debris is present in the Great Lakes, and has even been found at some of the highest concentrations yet to be documented for any other water body. The presence of this material has the potential to impact aquatic organisms both through the effects on digestion and energetics associated with consuming the material and through the exposure to contaminants that adhere to or are present in the plastic polymers. Ongoing research in the Burton Lab focuses on characterizing the potential exposure to, and effects of, small microplastic (< 5 mm) and microfiber materials. This is part of a larger U-M project that seeks to quantify and qualify microplastic debris by establishing a long-term multidisciplinary research platform of researchers focused on the processes that concentrate, disperse, and degrade microplastics as well as the ecosystem and human health effects of the material.Article in UM Ecology & Evolutionaly Biology News
The Strategic Environmental Research and Demonstration Program (SERDP) has again funded us (see Metal Bioavailability projects below) as part of a multi-investigator team to assess the potential for stormwaters to contaminate and re-contaminate sediments in receiving waters. Massive and expensive sediment remediation efforts are being conducted at a plethora of sites in North America, Europe and southeast Asia whereby dredging and capping operations are removing chemically contaminated sediments from harbors and rivers. Unfortunately, the sources of the legacy and on-going contamination are often not removed prior to the remediation actions which raises concerns of recontamination primarily from urban and agricultural runoff. We will assess chemical loadings and assess exposure dynamics and fate of these contaminants (dissolved and particulate) in San Diego Bay and link these loadings to adverse biological effects and sediment contamination. This research will better define the significance of ongoing nonpoint source loadings on receiving waters.
The objective of these projects is to improve understanding of how the interplay of physical, chemical, and biological processes controls the transformation, mobility, bioavailability, and toxicity of metals in sediments. Researchers will focus on the following key controls on the behavior of metals in sediments: (1) the effects of biological activity and overlying flows on pore water transport, sediment structure, chemical speciation, and contaminant fluxes; (2) the role that sediment structure plays in the exposure of organisms to contaminants; (3) the role of sediment diagenesis in modifying contaminant speciation, mobility, and bioavailability; and (4) the net effects of these processes on overall contaminant efflux and the bioavailability and toxicity of metals to benthic organisms.
These experimens looks specifically at two types of sediment disturbances. (1) Sediment resuspension events, such as those caused by propeller wash, is prevalent in harbors and navigation systems. (2) Bioturbation of sediments by benthic organims, specially polychaetes and oligiochaetes, which can release metals bound in sediments into overlying water. Physical-chemical models will be developed that predict metal contaminant speciation, partitioning, and transport and the resulting exposures linked to biological effects in these dynamic ecosystems.SERDP ER-1746 Research Summary SERDP ER-1745 Research Summary
The objective of this project is to demonstrate, commercialize, and promote regulatory acceptance of the integrated assessment tools, namely the Sediment Ecotoxicity Assessment Ring (SEA-Ring), developed in the SERDP Sediment Ecosystem Assessment Protocol (SEAP) project (ER-1550). Specific technical objectives of the demonstration are to (1) refine the current prototype to be more robust, user friendly, and cost-effective for commercial application and standardize test and quality control procedures; (2) generate sufficient high-quality data to scientifically validate the SEAP technology, introduce the Department of Defense (DoD) user community to the technology, and promote regulatory acceptance through rigorous demonstrations at select DoD sites located in geographically diverse settings; and (3) develop cost and performance data to support the commercialization of the technology and establish a pathway for full-scale DoD implementation.
Urban runoff is well-documented to be a major stressor of aquatic ecosystems and a leading cause of impairments (Burton and Pitt 2001, 2002). Impervious areas as low as 2 percent can result in impaired benthic macroinvertebrate communities. The city of Detroit has an old combined sanitary sewer and stormwater sewer system that results in combined sewer overflows following rain events – severely impacting the Detroit River and downstream Lake Erie. The U-M Water Center has funded this project to provide a demonstration of how contaminated and toxic urban runoff can be reduced in residential neighborhoods where abandoned properties are demolished and road and land runoff is diverted on-site for ground filtration, rather than allowing it to enter the storm sewers. We will assess the toxicity using in situ caged exposures of organisms to runoff in neighborhoods where this new practice is demonstrated.
Wetland soils generally decrease the bioavailablity of metals in the environment (Zn, Cu, Ni, Cd, and Cr) due to a unique biogeochemistry with high sediment accumulation rates; however, water level fluctuations may impact metal speciation and bioavailability. The Society of Wetland Scientists has in-part funded this project to (1) assess in-field spatial variability of bioavailable metals as a function of soil redox and vegetative cover; (2) assess the role of hydrologic fluctuation on bioavailability with an in-lab mesocosm study; and (3) test associated impacts on biologically important species, such as Chironomus spp. and Hyallela azteca. The findings from this study can provide insight to wetland managers and toxicologists on how to better manage metal contaminated wetlands to prevent exposure to organisms.
Sara Nedrich, PhD Candidate, is the project lead.
As the effects of climate change and watershed development compound upon aquatic ecosystems, stream biotic communities are forced to persist under altered hydrologic flow regimes or perish. Aquatic communities that reside in hydrologically altered streams are additionally exposed to increased risk from the effects of contaminated surface waters and sediments. In these uncertain hydrologic conditions, an influx of groundwater to streams can provide refuge to aquatic communities that face exposure to both hydrologic alterations and contaminants. This influx of groundwater occurs in the hyporheic zone, located at the interface of groundwater and surface water in stream sediments, and it may buffer organisms from the negative impacts of contaminants and hydrologic alterations. Unfortunately, few studies have analyzed the biological importance of contaminants in hyporheic exchanges. This research aims to better understand the influence of the hyporheic zone on stream biota, specifically in areas with contaminated sediments and hydrologic alterations.
Anna Harrison, PhD Student, is the project lead.
We have teamed with the School of Environment at Nanjing University, where Dr. Burton is a Concurrent Professor, to assess the multitude of water and sediment quality issues on Lake Taihu, a large freshwater lake in the Yangtze Delta plain near Shanghai, China. Lake Taihu has challenging issues with excess nutrients, harmful algal blooms and chemical contamination. It is also one of the largest and most important lakes in China, as it supplies drinking water to millions of people. The lead investigator is Professor Xiaowei Zhang who is assessing the biodiversity in the lake using gene bar-coding (comparing to traditional taxonomy) and using genomic responses to identify the primary chemical exposures. We are using the in situ TIEs (see above project), SEA Rings (see above project), and biofilm/periphyton (see above project) experiments to better understand contaminant exposures, their partitioning and both direct and indirect ecological responses. These studies will assist in the government-led management efforts of this important resource.