The document discusses in situ benthic observation tools for characterizing sediments and assessing risk. It describes how such tools provide insights into contaminant transport pathways, sediment-organism interactions, and chemical fluxes that influence exposure and effects. Integrating these observations with modeling helps evaluate risks of management strategies for contaminated sediments.

1. In Situ Benthic Observation Tools in Sediment Risk Assessments - and- The Need for Biogeochemistry in Characterizing In-situ Exposure and Effects Sabine E. Apitz, Ph.D. SEA Environmental Decisions, Ltd 1 South Cottages, The Ford Little Hadham, Hertfordshire SG11 2AT, UK 01279 771890 [email_address] … Linking science and applications

2. How we assess and manage sediment systems depends in part on how we conceptualise them In this conceptual model we view sediments and benthic organisms merely as pathways of contaminant transfer up a food chain

3. This shows a similar conceptual model in cartoon form

14. When one surveys a site, there can be a range of contaminant concentrations. How one uses the data depends upon the goals and assumptions – what is relevant to the in situ assay? Focus of public Focus of models Cu in sediments Range of Cu in case study sediments from different sites max median mean min

15. Where are the Contaminants? - Macro Scale In situ and on site chemical screening tools can provide rapid maps of sediment contaminant levels, guiding sampling and the placement of biological studies, and providing insight into heterogeneity Example: Field-portable XRF for rapid screening and mapping of metals

17. How contaminants behave In sediments, and how organisms interact with them, and how particles move is largely dependent upon the nature of the sediments Scanning Electron Microscope Imaging Provides Insight into Sediment Grain Size and Texture Light Microscopy Can Lend Insight into Sediment Grain Type, Mineralogy and Source Where are the contaminants? Micro-Scale

18. Sediments can bind contaminants in different ways, depending upon sediment characteristics, geochemical conditions and even degree of aging. This can affect contaminant mobility, bioavailability, degradability, fate and risk Chemo- and bio-availability Other organisms Sediment Particle Sediment micelle Cu PCB TPH Zn Pb PAH bacterial cell cell wall

20. PAH signature TPH signature PCB signature Cu vs. background signatures Cu/ grain size signatures Using Contaminant Concentrations Alone Does Not Provide Enough Information It is important to know what form your contaminants are in to understand and predict exposure, effects, fate and management

21. PAHs are a class of compounds. Although there are countless congeners with varying degree of substitution, most research and regulation focuses on the unsubstituted “parent” compounds Phenanthrene Pyrene Chrysene Benzo(a)pyrene Fluoranthene

22. Science – a search of citations for (PAHname* AND sediment AND biodeg*) yielded: Once you get to the substituted PAHs, there are almost no references 23 fluorene 17 chrysene 38 fluoranthene 66 Pyrene 151 Phenanthrene 157 Naphthalene Number of citations PAH

23. Whether one examines all PAHs over time in the sample, or just a subset, dramatically affects the degree of attenuation one predicts. What you examine depends on whether you want to track regulatory compliance or the reduction of PAH toxicity What is regulated and tracked (and what many lab organisms see) What is actually in sediments (and what in situ organisms see)

24. Integrating Regional and Historical Data Puts Site Data in Perspective However, if data sets are to be plotted together to look at regional trends, care should be taken to ensure equivalent data sets. In these Bay area results for Cr in sediments, the 1997 samples were prepared by total digestion and the 1998 samples were prepared by acid leach. Merging of data sets results in an offset – data are not comparable.

26. Stacked hazard quotients for case study sediment In all cases, actual effects should be evaluated

27. “ pristine” sites urbanized and lightly industrialized sites heavily industrialized sites Stacked hazard quotients for international case study sediments In all cases, actual effects should be evaluated

31. PRISM Program Integrates Field-Measurable Flux Parameters into Adapted Theoretical Models Age-dated cores BFSD Degradation Assays SPI Seep meter Microprofiler Sediment Traps Multicores In-situ flume Current Meters

34. Scale bars = 2cm Other in situ imaging applications: Infaunal functional groups from Joe Germano

36. Organisms alter the sediment structure, and thus the fluid and chemical fluxes from Joe Germano Flow-induced Advection: biogenically induced topography induces fluid flow, and thus localized redox states and chemical fluxes In situ microelectrodes can map small-scale chemical gradients, elucidating these processes

39. Sensors added to images: In situ planar oxygen optode module provides insight into the spatial and temporal dynamics of oxygen in sediments UCOP CCD camera LED trigger board lens LED array + emission filter dichroic mirror mirror planar optode excitation filter glass 8 mm silicon 40 µm dye 10 µm

40. Time-lapse 2-D images of O 2 distribution from planar Optodes – over a 24 hour period, much of this “reduced” sediment is oxic UCOP How does this affect chemical fluxes? Should we treat sediments as reduced or oxic?

42. Flux and Geochemistry Case study: Cu in Pearl Harbor Sediment Two sites at Pearl Harbor with very different grain size, geochemistry and use were examined (Site 2) (Site 4)

44. Flux and geochemical information are important: At other sites (in San Diego Bay), coarse-grained Cu-rich particles contained Cu which was less mobile than that sorbed to fine-grained particles Electron Dispersive X-Ray Scanning Electron Micrograph The Cu sulfides in these sediments were the result of ore spills from ship loading

52. Inserting field measurements into models – PAHs Flux into sediments Flux out of sediments