Contaminated Sediment in the St. Clair River: Ecological - - PowerPoint PPT Presentation

Contaminated Sediment in the St. Clair River: Ecological Implications and the Path Forward

ENVIRON International Corporation Public Consultation

Presentation Topics

• 1. Background
• 2. COA Framework Overview
• 3. Lines of Evidence
• 4. Prioritization of Zones for Sediment

Management

• 5. Questions/Discussion

• St. Clair Area of Concern (AOC)
• International Joint Commission identified 43

AOCs under the Great Lakes Water Quality Agreement

• St. Clair River named an AOC in 1985

– Contaminated sediment in the upper St. Clair River defined as high priority issue – Portions of upper St. Clair River remediated in 2004

• This study was done to

– Evaluate risks posed by key chemicals in the remainder of the AOC – Help prioritize sediment management solutions

• St. Clair River

Area of Interest (AOI)

1. Will fish or wildlife be harmed by chemicals in the sediment, invertebrates and fish? 2. Does the sediment need to be cleaned up to prevent harm to fish or wildlife? 3. If so, which areas are most important for cleanup? 4. What areas need to be studied more before decisions can be made? These questions are answered by applying the COA Framework

Key Questions Evaluated in this Study

What is Sediment?

Mud at the bottom of the river

= minerals + water + decaying plants & animals (“organic matter”) + insects, clams and worms (“invertebrates”)

Home to invertebrates, which are the base of the food chain

– Food for fish

Sediment sampling

What Are Chemicals?

Everything is made of chemicals

– Caffeine is a chemical – Organic chemicals contain carbon – Inorganic chemicals are everything else

Pollution occurs when people add harmful chemicals to the environment

– Dose

• se determines the effect

Many sources of pollution to the

• St. Clair River

– Mercury and octachlorostyrene pollution are of primary concern – There are natural sources of mercury and

• ther chemicals

Caffeine Octachlorostyrene

What are Mercury and Octachlorosytrene?

Mercury

– Occurs naturally and as pollution – Converted in sediment from mercury (like in a thermometer) to methylmercury (methylation) – Methylmercury is biologically available

Octachlorosytrene

– Byproduct of chlorination of organic chemicals – From industrial discharges

Both are persistent, bioaccumulative and toxic

– Don’t break down much over time (persistent) – Build up in fish and animals that eat fish (bioaccumulative) – Potential to cause injury or harm (toxic) – Goal is to eliminate such chemicals from the natural environment, including sediment

How are Levels of Chemicals Described?

“parts per million” or ppm In a jar of 1,000,000 jelly beans, 20 are green Concentration of green jelly beans = 20 ppm

Are Chemicals in Sediment Causing Harm?

The answer depends on: Which chemicals are found in the sediments, where, and at what level? Which chemicals may move in the environment, how, and where? What levels of chemicals are safe for fish and wildlife?

Summary of Key Messages

Risk from Biomagnification

• Risk to some fish species
• No risk to fish-eating wildlife

Sediment Chemistry

• All samples exceed Lowest Effect Level for Hg
• 61% of samples exceed Severe Effect Level for Hg
• Deep sediment 4 – 5 x surface sediment concentrations for

Hg

• No exceedances for octachlorostyrene (OCS)

Benthic Alteration

• No clear evidence of differences compared to reference

sites due to Hg or OCS

Sediment Toxicity

• No strong evidence of toxicity

Methylmercury in Surface Sediment of the AOI

Blue = lowest levels Brown = highest levels

Octachlorostyrene in Surface Sediment

• f the AOI

Blue = lowest levels Brown = highest levels

What is the COA Framework?

• Tool for making

decisions about how to manage the contaminated sediment

• Helps prioritize future

sediment management actions

COA Framework Uses Four Main Lines of Evidence

• 1. Risk from Biomagnification
• 2. Sediment Chemistry
• 3. Benthos* Alteration
• 4. Sediment Toxicity

* insects, worms, clams etc. that live in sediment

How are the Lines of Evidence Evaluated?

• Rules for when

– Adverse effects likely – Adverse effects uncertain – Adverse effects unlikely

• Results for each LOE

are combined to decide whether

– No further action necessary – Further study necessary – Sediment management necessary

Which Species Were Studied?

Invertebrates (insects, clams, and worms) Fish (sportfish such as northern pike and pickerel, and forage fish such as shiners) Birds (herring gull, double- crested cormorant) Mammal (raccoon)

Zebra mussels

Mayfly

Redhorse sucker Emerald shiner Herring gull Double- crested cormorant

Raccoon

Why Do Invertebrates Matter?

Important food for fish

– No invertebrates → no fish

They recycle nutrients

– One species' waste is another’s food

They live in the sediment with the mercury and

• ctachlorostyrene

– Pass chemicals to fish when eaten

Mayfly Midge Amphipod

Why Do Fish Matter?

Central to aquatic ecosystems Fish eat invertebrates People and wildlife eat fish People enjoy fishing Fish are key indicator of water and sediment quality

Northern pike Pickerel

Why Do These Wildlife Matter?

Top of this food chain

– Eat the big fish that eat the little fish that eat the bugs that live in the sediment

Their biology is well known, so studying them is possible Sensitive to mercury and organic chemicals Indicators of sediment quality and ecosystem health

Raccoon Double-crested cormorant Herring gull

Lines of Evidence

• 1. Risk from Biomagnification

For each species, depends on

• a. Exposure
• b. Toxicity
• 2. Sediment Chemistry
• 3. Benthos Alteration
• 4. Sediment Toxicity

• 1a. How Is Exposure Measured in

Invertebrates and Fish?

For invertebrates

– Levels of mercury and

• ctachlorostyrene in sediment

For fish

– Levels of mercury and

• ctachlorostyrene in fish and

their prey

Sediment Sampling Fish Tissue Sampling

• 1a. How Is Exposure Estimated

for Wildlife?

What do the wildlife living in/near the AOI eat? How much food do they eat? How often? What levels of chemicals are in their food? This information in used in mathematical equations to estimate “exposure”

• 1b. How Is Toxicity Measured in

Fish?

Field data

– Are they “fit”? – Are there equal numbers of males and females? – How do they compare to fish in

• ther waterbodies?

– Are differences linked to mercury and octachlorostyrene levels?

Safe fish tissue levels from scientific literature

– Mercury: 0.2 ppm – Octachlorostyrene: 0.015 to 0.18 ppm

Fish Sampling

• 1b. How Do We Measure

Toxicity in Wildlife?

We reviewed and summarized published studies that report safe levels of mercury and

• ctachorostyrene in

birds and mammals Calculate safe levels in their prey

• 2. How Is Sediment Chemistry

Measured?

• Chemicals settle out of the water and build up
• Sediment samples collected as core or grab
• Laboratory analyzes sediment samples for chemical

concentrations

• Physical properties of sediment provides information on

how chemicals move

Sediment Core Sampling Sediment Grab Sampling

• 3. How Is Benthos Alteration

Measured?

Community survey

– Collect sediment from the AOI and from “reference” areas – Count the types and numbers

• f invertebrates that live in the

sediment – Compare the AOI community to reference area communities

Benthic Sampling Sorting and Identifying Benthic Invertebrates

• 4. How Is Sediment Toxicity

Measured?

Divide AOI sediment into jars Add lab-reared invertebrates Over time, record growth, reproduction, and survival Compare the AOI results to reference area results

Toxicity Testing Toxicity Testing

Results

• 1. Risk from Biomagnification
• 2. Sediment Chemistry
• 3. Benthos Alteration
• 4. Sediment Toxicity

• 1. Are AOI Fish at Risk from

Biomagnification?

Compared levels in fish tissue to safe levels

– Categorized risk based on % of samples exceeding safe levels

Evaluated sex ratios and fitness of fish sampled for SFCMP

– No evidence of decreased fitness – SMB & YP appear female-biased in St. Clair River, compared to other regional waterbodies – Female bias correlated with mercury concentrations in fish tissue in FWD, SMB, NP & YP – But correlation ≠ causation and there are potential confounding factors

medium Freshwater drum Medium White sucker Northern pike Redhorse sucker Carp Yellow perch Rock bass Species high High medium medium low Risk

Conclusion: Some Fish Species May Be Harmed

• 1. Are AOI Wildlife at Risk from

Biomagnification?

Wildlife not at risk from mercury or

• ctachlorostyrene because

prey levels below safe levels

Safe Prey Levels Conclusion: Wildlife Not Likely To Be Harmed

• 2. Are Surface Sediment

Chemistry Levels Elevated?

All mercury concentrations above the LEL

[But sediment chemistry not necessarily related to biological effects]

No locations exceed calculated benchmark for

• ctachlorostyrene

• 2. Are Subsurface

Chemistry Levels Elevated?

In most significantly elevated locations, subsurface mercury levels are 4 – 5 X higher than in surface sediment No locations exceed benchmark for

• ctachlorostyrene

Contaminated sediment is being buried Potential for risk if subsurface sediment is disturbed and mobilized

Are Invertebrates at Risk?

• 3. Benthos Alteration

– Compared the number and type of invertebrates in the AOI to reference areas – No clear evidence of differences between AOI and reference areas – Pollution tolerant invertebrates common throughout river

• 4. Sediment Toxicity

– Compared growth, survival, and reproduction of invertebrates in AOI to reference areas – Mixed results from different studies, but limited toxicity not likely due to mercury and octachlorostyrene Conclusion: Invertebrates Not Likely To Be Harmed

What Areas Contribute Greatest Risk to Fish?

• Calculated safe level of

mercury in fish’s prey

• Mapped measured

concentrations in that prey

• Simulated removal of

“hot spots” until average equals safe level

• Prioritized zones of risk

to fish for sediment management (low, intermediate, high)

What About Mercury in Deep Sediment?

Factors that could disturb sediment

– Ice scour – Physical structures like docks

Several areas have conditions where mobilization is possible

Recommendation

Before deciding extent and methods of sediment management,

– Evaluate existing data and/or conduct new studies – To understand effects of

physical structures/ice

• n mercury distribution

and potential sediment disturbance

Questions & Discussion