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Current Issues

Bioaccumulation

This Executive Summary is reproduced from the EPA Guidance Manual referred to by Don Cox below.

Executive Summary

Traditionally, concerns relative to the management of aquatic resources in freshwater ecosystems have focused primarily on water quality. As such, early aquatic resource management efforts were often directed at assuring the potability of surface water or groundwater sources. Subsequently, the scope of these management initiatives expanded to include protection of instream (i.e., fish and aquatic life), agricultural, industrial, and recreational water uses. While initiatives undertaken in the past twenty years have unquestionably improved water quality conditions, a growing body of evidence indicates that management efforts directed solely at the attainment of surface water quality criteria may not provide an adequate basis for protecting the designated uses of aquatic ecosystems.

In recent years, concerns relative to the health and vitality of aquatic ecosystems have begun to reemerge in North America. One of the principal reasons for this is that many toxic and bioaccumulative chemicals [such as metals, polycyclic aromatic hydrocarbons (PAHs), polychlorinatedbiphenyls (PCBs), chlorophenols, organochlorine pesticides (OC pesticides), and polybrominated diphenyl ethers]; which are found in only trace amounts in water, can accumulate to elevated levels in sediments. Some of these pollutants, such as OC pesticides and PCBs, were released into the environment long ago. The use of many of these substances has been banned in North America for more than 30 years; nevertheless, these chemicals continue to persist in the environment. Other contaminants enter our waters every day, from industrial and municipal discharges, urban and agricultural runoff, and atmospheric deposition from remote sources. Due to their physical and chemical properties, many of these substances tend to accumulate in sediments. In addition to providing sinks for many chemicals, sediments can also serve as potential sources of pollutants to the water column when conditions change in the receiving water system (e.g., during periods of anoxia, after severe storms).

Information from a variety of sources indicates that sediments in aquatic ecosystems throughout North America are contaminated by a wide range of toxic and bioaccumulative substances, including metals, PAHs, PCBs, OC pesticides, a variety of semi-volatile organic chemicals (SVOCs), and polychlorinated dibenzo -p- dioxins and furans (PCDDs and PCDFs). For example, contaminated sediments pose a major risk to the beneficial uses of aquatic ecosystems throughout the Great Lakes basin, including the 43 areas of concern (AOCs) identified by the International Joint Commission. The imposition of fish consumption advisories has adversely affected commercial, sport, and food fisheries in many areas. In addition, degradation of the benthic community and other factors have adversely affected fish and wildlife populations. Furthermore, fish in many of these areas often have higher levels of tumors and other abnormalities than fish from reference areas. Contaminated sediments have also threatened the viability of many commercial ports through the imposition of restrictions on dredging of navigational channels and disposal of dredged materials. Overall, contaminated sediments have been linked to 11 of the 14 beneficial use impairments that have been documented at the Great Lakes AOCs. Such use impairments have also been observed elsewhere in Canada and the United States.

In response to concerns raised regarding contaminated sediments, responsible authorities throughout North America have launched programs to support the assessment, management, and remediation of contaminated sediments. The information generated under these programs provide important guidance for designing and implementing investigations at sites with contaminated sediments. In addition, guidance has been developed under various sediment-related programs to support the collection and interpretation of sediment quality data. While such guidance has unquestionably advanced the field of sediment quality assessments, the users of the individual guidance documents have expressed a need to consolidate this information into an integrated ecosystem-based framework for assessing and managing sediment quality in fresh water ecosystems (i.e., as specified under the Great Lakes Water Quality Agreement). Practitioners in this field have also indicated the need for additional guidance on the applications of the various tools that support sediment quality assessments. Furthermore, the need for additional guidance on the design of sediment quality monitoring programs and on the interpretation of the resultant data has been identified.

This guidance manual, which comprises a three-volume series and was developed for the United States Environmental Protection Agency, British Columbia Ministry of Water, Land and Air Protection, and Florida Department of Environmental Protection, is not intended to supplant the existing guidance on sediment quality assessment. Rather, this guidance manual is intended to further support the design and implementation of assessments of sediment quality conditions by:

  • Presenting an ecosystem-based framework for assessing and managing contaminated sediments (Volume I);
  • Describing the recommended procedures for designing and implementing sediment quality investigations (Volume II); and,
  • Describing the recommended procedures for interpreting the results of sediment quality investigations (Volume III).

The first volume of the guidance manual, An Ecosystem-Based Framework for Assessing and Managing Contaminated Sediments in the Freshwater Ecosystems, describes the five step process that is recommended to support the assessment and management of sediment quality conditions (i.e., relative to sediment-dwelling organisms, aquatic-dependent wildlife, and human health). Importantly, the document provides an overview of the framework for ecosystem-based sediment quality assessment and management (Chapter 2). In addition, the recommended procedures for identifying sediment quality issues and concerns and compiling the existing knowledge base are described (Chapter 3). Furthermore, the recommended procedures for establishing ecosystem goals, ecosystem health objectives, and sediment management objectives are presented (Chapter 4). Finally, methods for selecting ecosystem health indicators, metrics, and targets for assessing contaminated sediments are described (Chapter 5). Together, this guidance is intended to support planning activities related to contaminated sediment assessments, such that the resultant data are likely to support sediment management decisions at the site under investigation. More detailed information on these and other topics related to the assessment and management of contaminated sediments can be found in the publications that are listed in the Bibliography of Relevant Publications (Appendix 2)- not included here.

The second volume of the series, Design and Implementation of Sediment Quality Investigations , describes the recommended procedures for designing and implementing sediment quality assessment programs. More specifically, Volume II provides an overview of the recommended framework for assessing and managing sediment quality conditions is presented in this document (Chapter 2). In addition, Volume II describes the recommended procedures for conducting preliminary and detailed site investigations to assess sediment quality conditions (Chapters 3 and 4). Furthermore, the factors that need to be considered in the development of sampling and analysis plans for assessing contaminated sediments are described (Chapter 5). Supplemental guidance on the design of sediment sampling programs, on the evaluation of sediment quality data, and on the management of contaminated sediment is provided in the Appendices to Volume II. The appendices of this document also describe the types and objectives of sediment quality assessments that are commonly conducted in freshwater ecosystems.

The third volume in the series, Interpretation of the Results of Sediment Quality Investigations , describes the four types of information that are commonly used to assess contaminated sediments, including sediment and pore-water chemistry data (Chapter 2), sediment toxicity data (Chapter 3), benthic invertebrate community structure data (Chapter 4), and bioaccumulation data (Chapter 5). Some of the other tools that can be used to support assessments of sediment quality conditions are also briefly described (e.g., fish health assessments; Chapter 6). The information compiled on each of the tools includes: descriptions of its applications, advantages, and limitations; discussions on the availability of standard methods, the evaluation of data quality, methodological uncertainty, and the interpretation of associated data; and, recommendations to guide the use of each of these individual indicators of sediment quality conditions. Furthermore, guidance is provided on the interpretation of data on multiple indicators of sediment quality conditions (Chapter 7). Together, the information provided in the three-volume series is intended to further support the design and implementation of focused sediment quality assessment programs.

Don Cox has researched the aquatic herbicides used for aquatic weed control by Citrus county (see county web site: http://www.bocc.citrus.fl.us/pubworks/aquatics/herbicides/herbicides.htm). The pdf files found at this site are:

Agrisolutions 2, 4-D Amine 4 (http://www.bocc.citrus.fl.us/pubworks/aquatics/herbicides/agrisolutions.pdf)
Aqua Start (http://www.bocc.citrus.fl.us/pubworks/aquatics/herbicides/aqua_star.pdf)
Aquathol K (http://www.bocc.citrus.fl.us/pubworks/aquatics/herbicides/aquathol_k.pdf)
Aquathol Super K (http://www.bocc.citrus.fl.us/pubworks/aquatics/herbicides/aquathol_superk.pdf)
Reward (http://www.bocc.citrus.fl.us/pubworks/aquatics/herbicides/reward.pdf)
Sonar A.S (http://www.bocc.citrus.fl.us/pubworks/aquatics/herbicides/sonar_as.pdf)
Sonar PR (http://www.bocc.citrus.fl.us/pubworks/aquatics/herbicides/sonar_pr.pdf)
Sonar SRP (http://www.bocc.citrus.fl.us/pubworks/aquatics/herbicides/sonar_srp.pdf)

He has been able to identify five out of six herbicides found in the eight herbicides used by the county. They are:

2,4-Dichloro-phenoxyacetic acid found in Agrisolutions 2, 4-D Amine 4 http://www.epa.gov/safewater/dwh/c-soc/24-d.html
Diquat found in Reward http://www.epa.gov/safewater/dwh/t-soc/diquat.html
Endothal found in Aquathol and Aquathol k http://www.epa.gov/safewater/dwh/t-soc/endothal.html
Glyshosat found in AquaStar http://www.epa.gov/safewater/dwh/c-soc/glyphosa.html
Fluridone found in Sonar A.S http://www.pesticideinfo.org/

The active ingredients found in these aquatic weed control herbicides are 2, 4-Dichloro-phenoxyacetic acid, Diquat dibromide, Dipotassium of endothall, Glyphosate, and Fluridone that are found in Agrisolutions, Reward, Aquathol K, Aquathol Super K, Aqua-star, and Sonar respectively.

EPA has provided the information on the Environmental fate of the herbicide, for example, Diquat "When absorbed to sediment, little or no degradation probably occurs. In any case, the diquat disappears from the water in 2-4 weeks" It is the absorption into the sediment that creates the toxic problem.

These herbicides can generate toxicity by continual use, especially during drought periods. Starting back in the 1970's, aquatic weed control utilized copper-based and several other types of herbicide formulations until the late 90's have created a toxic problem with the new herbicides now being used. (see below, extract from page 20 of Kings Bay/Crystal River Florida: A Conceptual Proposal To Restore A Submerged Macrophyte Ecosystem Through Adaptive Management Rather Than Maintenance Control by Jason Evans, School of Natural Resources and the Environment, University of Florida, April 2006).

Early hydrilla ( Hydrilla verticillata) control efforts within Kings Bay were varied and largely ineffective, including a now notorious attempt to control hydrilla (Hydrilla verticillata) through the application of large amounts of sulfuric acid obtained from a nearby phosphate mine into the Hunter Springs area of Kings Bay. While an initial report indicated somewhat favorable results from the sulfuric acid treatment method (Phillipy 1966), aquatic plant managers later suggested that this treatment had only temporary effects on hydrilla ( Hydrilla verticillata) and severe detrimental effects on both fish and desirable aquatic vegetation (Friedman 1987). A more long-term hydrilla (Hydrilla verticillata) treatment program using a combination of copper-based and several other types of herbicide formulations was instituted in the 1970s (Haller et al. 1983). However, this program was also considered by many citizens and managers to be ineffective and counter-productive (see Dick 1989), and was eventually abandoned after elevated levels of copper were detected in Kings Bay's sediments and the organs of deceased manatees (Trichecus manatus) (O'Shea et al. 1984; Facemire 1991; Leslie 1992; SWFWMD 2000). A hydrilla ( Hydrilla verticillata) management program based upon shredding, mechanical harvest in navigational trails, and limited application of non-copper containing herbicide formulations of diquat, endothall, and flurodine was instituted in the late 1980s (Dick 1989; Cowell and Botts 1994) and remains the foundation of current hydrilla (Hydrilla verticillata) management within Kings Bay (Interagency Working Group 2005).

Bioaccumulation (see EPA - A Guidance Manual to Support the Assessment of Contaminated Sediments in Freshwater Ecosystems, Volume III (see Executive Summary above) — Interpretation of the Results of Sediment Quality Investigations from EPA, see Glossary of Terms extract below). It is the bioaccumulative effect of herbicides in sediment(s) that can present a toxic problem when released by dredging or grubbing the lake and bay bottoms. Now, factor in the Bioaccumulation of various herbicides applied in Citrus County, and you may well have a toxic soup of sediments just like the copper/herbicide/pesticides that are found in Kings Bay sediments. Copper sediments react negatively with a lot of the common herbicides and pesticides according to EPA studies on Bioaccumulation in Florida (see McDonald studies in Florida, Bioaccumulation Series, http://www.epa.gov/waterscience/cs/pubs.htm ).

Ecotoxicity — Found on the Fluoride Action Network Pesticide Project, (http://www.pesticideinfo.org/Index.html) Pesticide Action Network, North America, Aquatic Ecotoxicity for Fluridone for Sonar Products containing Fluridone have identified morbidity in several organism groups. The following summary was given for four groups.

Summary of Acute Toxicity for Organism Group
Organism Group Average Acute Toxicity Acute Toxicity Range
Crustaceans Slightly Toxic Slight to Moderate Toxicity
Fish Slightly Toxic Slight to Moderate Toxicity
Molluscs Moderately Toxic Moderate Toxicity
Zooplankton Slightly Toxic Slight to Moderate Toxicity

One of the major sources contributing to the Bioaccumulation of toxic sediments is golf course* and street run off into Kings Bay and local waters. Arsenic is one of the contaminates that have been found on and in the ground water at South Florida golf courses at unhealthful levels. Arsenic, like the copper sediments, can react negatively with the application of herbicides and pesticides in the shallow waters of bay or lakes.

* DERM Technical Report, Environmental Quality Monitoring at Five Municipal Golf Courses in Miami-Dade County, Prepared By the Department Of Environmental Resources Management in cooperation with the Florida Department Of Agriculture And Consumer Services, Final Report, December 2002.

Don Cox

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