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NATIONAL PERSPECTIVE ON SEDIMENT QUALITY Christopher Zarba U.S. Environmental Protection Agency ABSTRACT To address the growing concerns on the effects of contam- inated sediments on aquatic life, wild life, and human health, the U.S. Environmental Protection Agency (EPA) placed greater emphasis on development of a regulatory mech- anism to aid in evaluating and making decisions concerning contaminated sediments. Started in 1984, one of the first activities conducted under this effort was a national assessment of the scope of contaminated sediments. At that time, need and available resources did not warrant exhaus- tive study of the extent of contaminated sediments; however, to focus future activities a general assessment was needed. EPA Storage and Retrieval System (STORET) data was used (and supplemented with data from the literature) to provide a partial picture of distribution of some commonly found chem- icals in sediments and to identify chemical concentrations associated with contaminated sediments on a national basis. The following identifies the findings of the national assessment study. SEDIMENT QUALITY ASSESSMENT AND REGULATION The Environmental Protection Agency's (EPA) Criteria and Standards Division (CSD) develops and revises criteria, regulations, standards, r and guidelines in support of the mandates of the Clean Water Act. The CSD has published water quality criteria for 65 priority pollutants and pollutant categories. These criteria are based on an assessment of water column pollutant concentrations, which--if not exceeded--will pro- tect designated uses of a water body and 95 percent of the aquatic life from adverse effects. The EPA recognizes that while ambient water qual- ity criteria are an important component in assuring a healthy aquatic and human environment, contaminated sediments may be responsible for significant adverse effects even though water quality criteria are being met. To meet the growing need for a regulatory tool that could be used in assessing and making decisions concerning contaminated sediments, a sediment criteria development effort was undertaken by CSD. One of the These criteria are based on an assessment of 38
39 first activities conducted in this effort was development of a better understanding of the scope of contaminated sediments on a national basis. A national assessment on sediment quality was conducted. While this national assessment of sediment quality was not intended to be an exhaustive study, it was intended to provide those responsible for directing and focusing sediment criteria development activities with a clearer picture on the extent of the problem. The assessment was conducted using a total of 48 chemical contam- inants representing a diverse group of naturally occurring and anthro- pogenic materials indicative of compounds of increasing environmental concern. This list is not intended to be exhaustive, but rather is illustrative of the types of chemical data available for sediment. The seven chemical categories identified are polynuclear aromatic hydrocarbons, 2. pesticides, 3. chlorinated hydrocarbons, 4. mononuclear aromatic hydrocarbons, S. phthalate esters, 6. metals, and 7. miscellaneous. Threshold concentrations were then developed to judge differences in the levels of various chemicals in sediments. The majority of these values were calculated using the methodology of the Sediment-Water Equilibrium Partitioning Approach. To do this the assumption was made that the distribution of a chemi- cal between the organic carbon phase of the sediment and the soluble phase in interstitial water in equilibrium with the solid phase is determined by the organic carbon-water partitioning coefficient (Kook) for the chemical. If the water quality criterion value for the chemi- cal is taken to be the maximum acceptable concentration of the chemical in solution in the interstitial water, then the threshold concentration of the chemical in the bulk sediment is calculated based on the sedi- ment organic carbon-normalized KoC for the chemical. This allows for a numerical threshold to be established against which available monitoring data can be compared. The nonjudgmental use of this approach allows the distribution of the data set into percent- iles above and below the threshold even though one might question the significance of the results relative to the observed integrity or lack of integrity of biological communities. Threshold values derived from the sediment-water partitioning approach are based on the organic carbon content of the particular sed- iment (Table 1~. These values were adjusted to a whole sediment basis on the assumption that an average sediment contains 4 percent organic carbon. Furthermore, the values are compared to the monitoring data on a dry weight equivalent basis. For several chemicals, for which no acute and chronic water quality criterion values are available, other toxicological endpoints were used.
40 TABLE 1 Contaminants Reviewed and Developed Threshold Values Threshold value Threshold value Contaminants mg/kg Contaminants mg/kg Polynuclear aromatic Monoaromatic hydro- hydrocarbons carbons benzoapyrene 1,800 toluene 10 naphthalene 42 benzene 1.36 phenanthrene 56 ethylbenzene 5.6 chrysene 460 nitrobenzene 6.6 fluorene 28 dinitrobenzene 0.88 acenaphthene 66 anthracene 44 Phthalates benzoaanthracene 220 butylbenzyl phthalate 220 acentphthalene 24 di-N-butylphthalate 2,000 indeno(l,2,3-CD) diethylphthalate 1.28 pyrene 24,000 dimethylphthalate 1.96 benzod fluoranthene 5,000 Metals arsenic 33 Pesticides cadmium 31 lindane 0.012 copper 136 DDD 13 lead 132 DDE 28 mercuryb 0.8 aldrin 0.021 zinc 760 isophrone 9.6 chromiume 25 DDT 0.006 nickele 20 chlordaneb 0.020 toxapheneb 0.020 Miscellaneous heptachlorb 0.020 cyanide 0.1 Chlorinated hydrocarbons hexachloroethane 14.4 hexachlorobutadiene 1.28 tetrachloroethylene 1.8 trichloroethylene 6.4 dichlorobenzene 2.8 methylene chloride 2 PCBsC 0.28 NOTES: aThreshold concentrations are those determined by the EPA/OWRS unless otherwise stated. Criteria for organic contaminants are calculated on the basis of 4 percent organic carbon content of sediment. bU.S. Geological Survey sediment alert levels. CBased on criterion for hexachlorobiphenyl. ~he value of 0.8 was not corrected for organic carbon. Correction of this value would have resulted in a mercury concentration of 0.03. which is considerably lower than the concentration of this metal in most sediments. eEPA Region V guidelines for designating contaminated verses noncon- taminated sediments.
41 The methods used to evaluate the level of various chemicals in sedi- ments of fresh waters, marine waters, and estuaries was consistent to the extent that the data search included the same chemical and selected threshold values. To compare the monitoring data, the concentrations were divided for convenience into four subranges: level 1, less than threshold value; level 2, 1-3 times threshold value; level 3, 3-10 times threshold value; and level 4, greater than 10 times threshold value. THE DATA BASE Due to the limitations of the EPA Storage and Retrieval System (STORET) data base for this type of analysis, it is likely that there are numerous additional areas with significant contaminant levels that are not represented in this report. Figures 1, 2, and 3 depict loca- tions where contaminants were at levels 3 and 4. Freshwater Data A very large data base was available for evaluation of contamina- tion of sediments in streams, rivers, lakes, and reservoirs. The STORET system was the primary source of data for this effort. Of the group of 48 chemicals identified initially, data on 22 were obtained from the STORET system and over 255,000 data records were processed. No attempt was made to judge the quality of these data or the accuracy and precision of the analytical techniques used to obtain them. Marine/Estuarine Data Concentrations of various chemicals in marine and estuarine sedi- ments were obtained from the published literature and from some litera- ture with limited distributions. An additional set of referenced data points was derived from STORET data files. Marine/e stuarine STORET data were limited to median concentrations of various chemicals. No ranges of concentrations were given and the data base was sufficient to manipulate data. OBSERVATIONS AND CONCLUSIONS Fresh Water There was a clustering of a variety of chemicals at certain sites rather than a general scattering of data. In general, coastal areas were the most noticeably affected regions. New York, New Jersey,
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45 Michigan, Arizona, Nevada, Washington, and California contain areas which were repeatedly identified as contaminated. This distribution indicated a broad spectrum of contamination within certain areas. The limited analysis of station-by-station data for the top 200 measurements indicate that (1) areas are widely scattered around the country, justifying development of sediment criteria on a national basis, and (2) the highest contamination levels for many chemicals represent potential hot spots rather than general high concentrations over a broad area. Metal concentrations were, for the most part, classified in level 1. Only nickel, which had 42 percent of the data in the upper three concentration levels, was an exception. In situ and bioassay data sug- gest a need to reevaluate threshold values derived from water quality criteria. Almost all of the PAN data were classified in level 1. A wide span exists between the currently suggested threshold values and even the highest observed concentrations. The biological impact data suggest a need to reevaluate threshold levels. A significant percent of phthalate data fell in the higher classifi- cation levels: 36 percent for diethylphthalate and 35 percent for dimethylphthalate. However, no biological impact data were found to indicate a need to review threshold values. The vast majority of the pesticide data were in the level 1 range. Chlordane, DOT, and toxaphene had 16, 7, and 14 percent of the data points in the level 2 range, respectively. Biological impact data indi- cated a need to reevaluate threshold levels. The PCB data were distributed with 18 percent of the data above level 1. However, only 0.04 percent would be located in level 2 at the highest proposed threshold value using alternative criteria. There is a need for further evaluation using biological impact data. Much of the available in situ or in viva data were inappropriate to determine sediment-related toxic effects, because parallel measurements of chemical concentrations and biological species distribution of other biological effects have not been made. Marine/Estuartne Waters The principal sites that contained chemicals of interest at high concentrations include Puget Sound waterways, Corpus Christi Harbor, New York Harbor, Baltimore Harbor, Boston Harbor, New Bedford Harbor, Blackrock Harbor, the California sewage outfalls at Palos Verdes, and parts of San Francisco Bay. Chemicals of major concern were those that exceeded the provisional sediment threshold values of several coastal locations. These chemi- cals include toxic metals, PAR, PCBs, and DOT. Other chemicals in this inventory of coastal sites did not reach or exceed the first-cut sedi- ment threshold values. The marine/c stuarine survey was based on a very limited data base. A more detailed literature search may reveal additional chemicals of major concern.
46 Threshold concentrations for chemicals in sediments based on sediment-water equilibrium partitioning are probably set too high for the majority of chemicals considered, most notably for PAR compounds and metals. This overestimation was best illustrated by the discrepancy between biological effects observed in New York Bight sediments, despite corresponding sediment contaminant concentrations of inventoried chemicals that rarely exceed threshold biological effects levels. ACKNOWLEDGMENT The material presented in this paper is a summary of material pre- sented in the EPA document "National Perspective on Sediment Quality." This document was assembled in 1985 and in many cases reflects the state of knowledge on toxic sediments at that time. If this document were updated. changes in the conclusions identified above would be likely. For copies of the document or for additional information con- tact Christopher Zarba at (202) 47S-7326.
