1、A Guide to Understanding, Assessment, and Regulation of PAHs in the Aquatic EnvironmentAPI PUBLICATION 4776SEPTEMBER 2011A Guide to Understanding, Assessment, and Regulation of PAHsin the Aquatic EnvironmentRegulatory and Scientific AffairsAPI PUBLICATION 4776SEPTEMBER 2011Special NotesAPI publicati
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11、 and should be submitted to the Director of Regulatory and Scientific Affairs, API,1220 L Street, NW, Washington, DC 20005.iiiA GUIDE TO UNDERSTANDING, ASSESSMENT, AND REGULATION OF PAHS IN THE AQUATIC ENVIRONMENT I CONTENTS 1.0 Executive Summary 1 2.0 Scope of This Guide . 2 3.0 Why This Guide was
12、Developed . 2 4.0 Why PAHs Are Important . 3 5.0 Chemical Structure of PAHs 3 6.0 Formation of PAHs 6 6.1 Petrogenic 6 6.2 Pyrogenic . 7 6.3 Biogenic . 7 6.4 Diagenetic 7 7.0 Distribution of PAHs . 8 7.1 PAHs in the Environment 8 7.1.1 Air 8 7.1.2 Water . 8 7.1.3 Aquatic Sediments 8 7.1.4 Soil . 9 7
13、.2 PAHs in Source Materials 9 7.2.1 Crude Oils . 10 7.2.2 Fuels 10 7.2.3 Exploration and Production Wastes . 11 7.2.4 Pyrogenic and Mixed Sources of PAHs 12 8.0 Environmental Fate . 13 8.1 PAH Partitioning . 14 8.1.1 Estimation Techniques . 14 8.1.2 Direct Measurement Techniques . 15 8.2 Transformat
14、ion Processes . 15 8.3 Bioaccumulation 16 9.0 Toxicity and Health Effects 17 9.1 Human and Ecological Effects . 17 9.2 Bioavailability and Influence on Toxicity 18 II API PUBLICATION 4776 9.3 Individual Compounds Versus Mixtures 18 10.0 Regulations, Standards, and Guidelines 19 10.1 Water Quality St
15、andards . 19 10.2 Sediment Quality Standards 20 10.3 Impaired Surface Waters and TMDLs . 20 10.4 Sediment Quality Guidelines . 23 10.4.1 Equilibrium Partitioning (EqP) . 24 10.4.2 National Status and Trends (NS however, they have their own limitations, which should be well understood before they are
16、 applied. Site investigations involving PAHs in sediments should use a tiered approach, with initial efforts focused on identifying whether environmental impacts actually exist, and using the more simple chemical analysis methods. If further study is warranted, advanced site investigation techniques
17、 can be used, including advanced chemical fingerprinting. 2 API PUBLICATION 4776 2.0 Scope of This Guide This document was designed to be an introductory guide to understanding and assessing polycyclic aromatic hydrocarbons (PAHs) in the aquatic environment (water and sediments). The American Petrol
18、eum Institute (API) commissioned this guide primarily for refinery personnel and home office environmental staff who may have to address PAH issues. In addition, this guide may also be useful to staff in regulatory agencies that work with PAHs in wastewater discharge permits, waste load allocations
19、(TMDLs), and sediment investigation and remediation. The guide provides an overview on the chemistry, fate, and sources of PAHs in the environment, and the regulatory implications. The guide also includes descriptions of the different sources of PAHs (petrogenic, pyrogenic, diagenic, biogenic) and t
20、echniques for differentiating these sources through their characteristic fingerprints, including straightforward ways to help identify or rule out potential sources. 3.0 Why This Guide was Developed In the environmental field of water and sediments, there is an emerging focus on sediment quality. Th
21、e United States Environmental Protection Agency (EPA) has developed the concept of sediment quality criteria, which could lead to numerical targets for contaminants in sediment similar to water quality criteria in the water column. Some states, such as California and Washington, have adopted or are
22、adopting sediment quality standards based on such criteria. Failure of sediments to meet the criteria may result in waters being listed as impaired and/or remediation of the sediments. There is also an emerging focus on PAHs as a family of contaminants, especially in sediments. PAHs are a class of c
23、ompounds containing from 2 to more than 10 fused aromatic hydrocarbon rings, for example, naphthalene (2 rings) and ovalene (10 rings). Lower ringed compounds, such as naphthalene, are relatively soluble and biodegradable, but they can exhibit significant acute toxicity to aquatic organisms. Higher
24、ringed compounds, such as benzo(a)pyrene (5 rings), are more persistent in the environment. Higher ringed compounds tend to exhibit lower direct toxicity, but a higher potential to be carcinogenic, mutagenic, or teratogenic to a wide range of organisms, including amphibians, fish, birds, and mammals
25、. Often, the higher ringed PAHs are assumed to bioaccumulate more than the lower ringed PAHs; however, studies have shown that higher ringed PAHs actually bioaccumulate less in higher trophic levels. PAHs occur naturally in trace amounts in crude oil and certain petroleum-based products such as dies
26、el. Consequently, petroleum refineries are often blamed for PAH contamination in water or sediments. Studies have shown, however, that combustion can be a major contributor to PAHs. Recent studies have also identified pavement sealers as significant sources of PAHs. As a family of compounds, PAHs va
27、ry in source materials by type and quantity. Consequently, many PAH sources have distinctive characteristics that provide a signature or fingerprint that can be used to identify and quantify their contribution to the total PAH content in sediments. For example, pyrogenic PAHs, whose source is combus
28、tion, present a much different signature than petrogenic PAHs, whose source is petroleum. A variety of techniques, ranging from simple to very complex, can be used to differentiate among PAHs sources reflected in sediments at a particular location. This guide was developed to address these issues by
29、 providing basic, factual information on PAHs that affect water and sediments. This guide can be used by both refinery and regulatory personnel to understand how differences among individual PAHs relate to their environmental impacts, how to properly differentiate among sources of PAHs, and how to p
30、roperly regulate PAHs in petroleum industry discharges. API has published other reports containing useful information on PAHs, some of which has been incorporated into this guide. Interested readers will find additional information in those reports: (1) A Guide to Polycyclic Aromatic Hydrocarbons fo
31、r the Non-specialist (2002, API Publication No. 4714); (2) Fate and Effects of Polynuclear Aromatic Hydrocarbons in the Aquatic Environment (1978, API Publication No. 4297); and (3) Bioaccumulation: How Chemicals Move from the Water Into Fish and Other Aquatic Organisms (1997, API Publication No. 46
32、56). A GUIDE TO UNDERSTANDING, ASSESSMENT, AND REGULATION OF PAHS IN THE AQUATIC ENVIRONMENT 3 4.0 Why PAHs Are Important PAHs are nearly ubiquitous trace contaminants of freshwater and marine sediments worldwide. Some PAHs are toxic to organisms that live in the water and sediments. Some PAHs are k
33、nown or suspected carcinogens, making the consumption of contaminated fish and water a concern. Concern about PAHs due to their toxicity or carcinogenicity, and their persistence in the environment, has led to regulation of PAHs under numerous environmental laws such as the Clean Air Act, Clean Wate
34、r Act, Emergency Planning and Community Right-to-Know Act, Occupational Safety and Health Act, Resource Conservation and Recovery Act, and Safe Drinking Water Act. 5.0 Chemical Structure of PAHs Polycyclic aromatic hydrocarbons, or PAHs, are a class of hydrocarbon compounds consisting of two or more
35、 fused aromatic hydrocarbon rings. PAHs may also be referred to as polynuclear aromatic hydrocarbons (PNAs) or polycyclic aromatic compounds (PACs). The hydrocarbon ring is hexagonal (six sides), with a carbon atom at each corner or point. Although there are many individual chemicals that are PAHs,
36、the ones most common in environmental investigations are shown in Figure 1 and Table 1. Of these PAHs, 16 are referred to as the priority pollutant PAHs because they are the PAHs on EPAs priority pollutant list. Consequently, they are the ones most commonly analyzed in environmental samples. As note
37、d in Table 1, seven of the 16 priority pollutant PAHs are known or suspected carcinogens: benz(a)anthracene; benzo(a)pyrene; benzo(b)fluoranthene; benzo(k)fluoranthene; chrysene; dibenz(a,h)anthracene; and indeno(1,2,3-cd)pyrene. Figure 1 shows common PAHs containing from two to six rings. Naphthale
38、ne, consisting of 2 rings, is the simplest PAH. Most PAHs found in the environment contain two to seven rings joined into a variety of shapes, although PAHs with more rings are also found. The ultimate PAH is graphite, an inert material consisting of planes of fused rings. True PAHs are made up only
39、 of hydrogen and carbon atoms. Closely related compounds, called heterocycles, in which nitrogen, oxygen, or sulfur replaces one of the carbon atoms in a ring, are commonly found with PAHs. Figure 1 also shows examples of heterocyclic compounds such as dibenzothiophene, a sulfur heterocycle. Althoug
40、h not PAHs, certain nitrogen- and sulfur-containing heterocyclic compounds are frequently used for forensic PAH fingerprinting purposes. PAHs often occur with aliphatic and non-aromatic cyclic hydrocarbons attached to the rings at one or more points. These PAHs are described as alkylated PAHs. An ex
41、ample of aliphatic, alkylated PAHs in Table 1 would be the C1-naphthalene group, which would include 1-methylnaphthalene and 2-methylnaphthalene. Examples in Table 1 of non-aromatic cyclic hydrocarbons attached to PAHs are acenaphthene, acenaphthylene, fluorene, and fluoranthene. The basic, unalkyla
42、ted form of a PAH is called the parent PAH; all of the 16 priority pollutant PAHs are parent PAHs. For example, naphthalene would be the parent PAH of its series of alkylated forms. A parent PAH and its various alkylated homologues is called a homologous series. A homologue is a chemical that has th
43、e same basic structure as other homologues in the series, but differs in the number of repeated structural units; in this case, the alkyls. Because there are many possible locations, number, and length of alkyl chains on the parent PAH, alkylated PAHs are often classified by the number of alkyl carb
44、ons they contain. For example, 1-methylnaphthalene is a C1-naphthalene PAH and ethylpyrene is a C2-pyrene PAH. The environmental significance of PAHs stems from their ubiquitous nature in aquatic systems as well as their perceived persistence and toxicity. Solubility, molecular weight, and structure
45、 all play important roles in assessing persistence and toxicity. The smaller, two- to three-ringed PAHs are generally more soluble in water, more available to ecological receptors, and therefore, more toxic to aquatic life than higher ringed PAHs. Other effects of exposure are also variable based on
46、 the size and structure of a given PAH. While toxicity has been shown to decrease with increasing size; carcinogenicity, mutagenicity, and teratogenicity may all increase with molecular size. The division between low and highmolecular weight PAHs (LPAHs, HPAHs) is somewhat arbitrary. LPAHs typically
47、 are taken to include: naphthalene, acenaphthylene, acenaphthene, fluorene, phenanthrene, and anthracene 4 API PUBLICATION 4776 (2- and 3-ring parent PAHs). HPAHs typically are taken to include: fluoranthene, pyrene, benz(a)anthracene, chrysene, total benzofluoranthenes, benzo(a)pyrene, indeno(1,2,3
48、,c,d)pyrene, dibenz(a,h)anthracene, and benzo(g,h,i)perylene (i.e., 4-, 5-, and 6-ring member parent PAHs). In general, the presence and predominance of HPAHs is a fairly good indicator of pyrogenic input to the environment. A GUIDE TO UNDERSTANDING, ASSESSMENT, AND REGULATION OF PAHS IN THE AQUATIC
49、 ENVIRONMENT 5 Table 1. PAHs and Related Heterocyclic Compounds Commonly Used in Advanced Chemical Fingerprinting to Distinguish Among PAH Sources Analyte/Analyte Group Abbreviation Rings *EPA 16 priority pollutants Suspected or known carcinogen Naphthalene* N0 2 C1-Naphthalenes N1 C2-Naphthalenes N2 2 C3-Naphthalenes N3 C4-Naphthalenes N4 2 Biphenyl B,Bph Acenaphthylene* AY,Acl 3 Acenaphthene* AE,Ace Dibenzofuran DF,DbF Fluorene* F0 3 C1-Fluorenes F1C2-Fluorenes F2C3-Fluorenes F3 3 Anthracene* A0,AN Phenanthrene* P0 C1 Phenanthrenes/Anthracenes PA1,P1 3 C2 Phenanthrenes/Anthracenes PA
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