Porewater Collection and Risk Evaluation 27 th Alabama Water Resources Conference Orange Beach, AL Jacob Gruzalski Environmental Standards, Inc.

Acknowledgements I would like to thank the following individuals for their significant contributions and input:  Dr. Bill Rogers - Tennessee Valley Authority  Dr. Neil Carriker - Tennessee Valley Authority  Mr. Rock Vitale - Environmental Standards, Inc.  Mr. David Thal - Environmental Standards, Inc.  Dr. James Markwiese - Environmental Standards, Inc. 2

Objectives  Define Porewater  Reason for Porewater Collection and Analysis  Importance of Proper Porewater Sampling  Overview of Case Studies  Conclusions 3

Porewater Basics 4

Sediment  Sediment is naturally occurring material that is broken down by processes of weathering and erosion and transported by wind, water, or ice.  Sediment is comprised of an aqueous and solid phase. 5

Porewater – Definition  Porewater is the water filling the spaces between grains of the solid phase of sediment o Sand, silt, and clay  Porewater is the aqueous phase of sediment  By definition porewater cannot exist separate from the solid phase of sediment in the environment 6

Porewater – Ecological Significance  Sediment porewater is a primary exposure pathway of contaminants to the benthic community.  These organisms then have the potential of introducing contaminants into the food chain (fish, aerial feeding birds). 7

Pictorial Conceptual Site Model 8

Why Analyze Porewater? 9

Why analyze porewater?  To collect complete information on sediment contamination  Chemical concentration profiles in sediment porewater are widely used in studies and investigations into contaminant exposure, fate, and transport.  To evaluate potential exposure pathways o Bioavailable vs. Total o Line of evidence in ecological risk assessments o Toxicity testing 10

Why analyze porewater? (cont.)  An understanding of porewater in relation to sediment properties provides for the following: o Complete picture of the exposure to the benthic aquatic environment; o Comprehensive identification of contaminant sources and sinks and their extent; o Prediction of contaminant flux across the sediment-water interface. 11

Why analyze porewater? (cont.)  Evaluating concentrations in porewater is important to differentiate bioavailability of the contaminant from total concentration of the contaminant in the sediment.  This is possible only if porewater data truly reflects the in-situ conditions.  Many sampling and processing techniques do not address the possibility of geochemical transformation during porewater collection and extraction. 12

Porewater Collection 13

Porewater Collection  Collection and processing methods have the potential to cause geochemical changes to the porewater, primarily through oxidation.  This oxidation can lead to biased results that do not accurately represent the natural conditions.  Results can be biased to indicate both higher and lower concentrations compared to in-situ conditions.  What does this mean?  The collection and processing technique selected should be able to produce the most “realistic” data possible 14

Case Studies  Ubatuba Bay, Brazil, River Study  Tennessee Valley Authority Kingston Ash Recovery Project 15

Ubatuba Bay, Brazil, River Study  Aim of study to present results of chemical analysis of ammonium ions from porewater extracted in oxygen-free environment  Sediment samples collected from four river estuaries on Ubatuba Bay in southeast Brazil  Historically, rivers have received discharges of raw sewage 16

Ubatuba Bay, Brazil, River Study (cont.)  Six samples collected from each location and split into two groups  One sample group processed in oxygen-free environment and other sample group exposed to the atmosphere 17

Ubatuba Bay, Brazil, River Study (cont.) 18

Tennessee Valley Authority Kingston Ash Recovery Project (TVA KRP)  Large release of fly ash spilled from containment area at the Kingston, TN, fossil plant in December  Approximately 5.4 million cubic yards of ash released from containment area with the majority discharging into the Emory River.  Two high flow storm events shortly after release 19 December 22, 2008

TVA KRP  In addition to the chemical constituents in fly ash (primarily metals – As, Se), this release also had the ecological impacts of large deposits of ash on the bottom of the river  Fly ash removed from the Emory River by hydraulic and mechanical dredging  Extensive sampling and monitoring program executed throughout the life of the project (ongoing) 20

TVA KRP – Porewater Sampling  Due to the nature of the project, multiple organizations are involved  Porewater samples have been collected by TVA and third-party researchers  Sampling occurred over multiple years at same general locations  Multiple porewater sampling methodologies have been implemented 21

As Porewater vs Total (sediment) 22 As Porewater (mg/L) Total As – Sediment (mg/kg)

As Sequential Extraction Procedure 23

TVA KRP - Summary  PW vs Total As concentrations between the collection methods suggest aerobic technique results in biased (high) data  Sediments included in TVA study have little to no sulfides  SEP data and previously published literature suggest Fe oxide is binding potentially bioavailable As.  Exposure to atmosphere during processing releases As to the porewater 24

Summary  If porewater sample collection is planned, proper collection and processing methods are essential.  The documented effects of oxidation of porewater during collection drives the need for collection and processing of porewater in oxygen-free environment.  Improper sample collection can lead to biased data not reflective of in-situ conditions.  Evaluating in-situ conditions needed to assess bioavailability of contaminants. 25

QUESTIONS? 26

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