1、Technical Protocol for Evaluating the Natural Attenuation of MtBE Regulatory and Scientific Affairs Department API PUBLICATION 4779 MAY 2007Technical Protocol for Evaluating the Natural Attenuation of MtBE Regulatory and Scientific Affairs DepartmentAPI PUBLICATION 4779MAY 2007Prepared by:Peter Zeeb
2、, Ph.D., L.S.P., P.G. Geosyntec Consultants, Inc. Acton, MassachusettsandTodd H. Wiedemeier, P.G. T.H. Widemeier however, the Institute makes no representation, warranty, or guarantee in connection with this publication and hereby expressly disclaims any liability or responsibility for loss or damag
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8、ny means, electronic, mechanical, photocopying, recording, or otherwise, without prior written permission from the publisher. Contact the Publisher, API Publishing Services, 1220 L Street, N.W., Washington, D.C. 20005.Copyright 2007 American Petroleum InstituteFOREWORDNothing contained in any API pu
9、blication is to be construed as granting any right, by implication or otherwise, for the manufacture, sale, or use of any method, apparatus, or product covered by letters patent. Neither should anything contained in the publication be construed as insuring anyone against liability for infringement o
10、f letters patent.This document and other oxygenate resources can be found at: www.api.org/mtbe. Trademarks: C-Flex is a registered trademark of consolidated Polymer Technologies, Inc. CHEMetrics is a registered trademark of CHEMetrics, Inc. En Core is a registered trademark of En Novative Technologi
11、es, Inc. Hach is a registered trademark of the Hach Company. Teflon is a registered trademark of the E. I. Du Pont De Nemours and Company Corporation. Waterra is a trademark of Waterra Pumps, Ltd.Suggested revisions are invited and should be submitted to the Director of Regulatory and Scientific Aff
12、airs, API, 1220 L Street, NW, Washington, D.C. 20005.iiiTABLE OF CONTENTS 1 INTRODUCTION 1 1.1 Purpose and Objectives of Document 1 1.2 Regulatory Status of MNA of MtBE . 2 1.3 Anticipating and Addressing Stakeholder Concerns . 3 1.4 MtBE Attenuation State-of-the-Science 3 1.4.1 Physio-Chemical Mech
13、anisms of MtBE Attenuation . 4 1.4.2 MtBE Biodegradation . 6 2 DEVELOPING A NATURAL ATTENUATION EVALUATION STRATEGY 8 2.1 Overview of MNA as a Remediation Tool 8 2.1.1 Overview of Existing MNA Guidance 8 2.1.2 Applicability of Site Characteristics to MNA . 13 2.2 Tiered Approach for Evaluating the N
14、atural Attenuation of MtBE and Required Supporting Data. 14 2.2.1 Tier 1 Evaluation of Plume Behavior. 15 2.2.2 Tier 2 Geochemical Data 18 2.2.3 Tier 3 Supplemental Data. 19 2.3 An Integrated Approach for Utilizing the Three Tiers of Data . 19 2.3.1 Tier 1 Data are Adequate to Evaluate Natural Atten
15、uation. 20 2.3.2 Tier 2 Data are Collected 20 2.3.3 Tier 3 Data are Collected 20 2.3.4 Site Characterization and Conceptual Model Development . 20 2.3.5 Sites That Have Adequate Site Characterization Data 22 2.3.6 Sites That Do Not Have Adequate Site Characterization Data. 23 2.4 Mass Flux Estimates
16、 24 3 SAMPLE COLLECTION AND ANALYSIS 25 3.1 Sampling Location and Frequency 25 3.2 Sample Preservation 26 3.3 Laboratory Analytical Methods. 27 3.3.1 MtBE . 27 3.3.2 Breakdown Products of MtBE and Other Associated Chemicals 30 TABLE OF CONTENTS (Continued) 3.3.3 Geochemical Data . 31 3.3.4 Compound
17、Specific Stable Isotope Analyses 33 3.3.5 Laboratory Microcosms 34 3.3.6 Molecular Microbial Community Analysis. 35 4 MtBE MNA DATA EVALUATION AND PRESENTATION. 38 4.1 Tiered Approach for Evaluating the Natural Attenuation of MtBE 38 4.2 Tier 1 Data Analysis 40 4.2.1 Hydrogeologic Evaluation. 40 4.2
18、.2 Hydrogeologic Data Presentation 41 4.2.3 Evaluation of Source Strength and Composition 43 4.2.4 Techniques for Evaluating Plume Stability. 46 4.3 Tier 2 Data Analysis 64 4.3.1 Biogeochemistry Evaluation . 65 4.3.2 Presentation of Spatial/Temporal Changes in Geochemical Parameters . 67 4.4 Tier 3
19、Data Analysis 70 4.4.1 Compound Specific Isotope Analysis . 70 4.4.2 Microcosm Study Data 73 4.4.3 Presentation of Microcosm Study Data. 74 5 REFERENCES . 77 APPENDIX ABIODEGRADATION MECHANISMS A-1 APPENDIX BPHYSIOCHEMICAL ATTENUATION MECHANISMS B-1 APPENDIX CESTIMATING MASS FLUX . C-1 APPENDIX DFIE
20、LD DATA COLLECTION PROTOCOLS.D-1 APPENDIX EDATA QUALITY ASSURANCE E-1 APPENDIX FEXAMPLE MANN-KENDALL ANALYSIS F-1 APPENDIX GEXAMPLE FIRST ORDER RATE CALCULATION.G-1 APPENDIX HSUMMARY OF THE RESULTS OF TBA NAPL/ AQUEOUS PARTITIONING EXPERIMENTS H-1 TABLE OF CONTENTS (Continued) TABLES Table 1-1 Physi
21、cal Properties of MtBE and Other Constituents of Gasoline 5 Table 2-1 Technical Protocols and Other Guidance Documents for Evaluating the Efficacy of Natural Attenuation.10 Table 2-2 Summary of the Lines of Evidence Used to Evaluate Natural Attenuation and Enhanced Remediation.11 Table 2-3 Tier 1 Da
22、ta .12 Table 2-4 Tier 3 Data .12 Table 3-1 Sample Preservation and Hold Times29 Table 3-2 Methods for Analysis of MtBE, TBA and Other Volatile Organic Compounds of Interest.32 Table 3-3 Laboratory Analysis for Tier 2 Geochemical Parameters33 Table 4-1 Definition of Plume Geochemistry for Anaerobic C
23、onditions 65 Table 4-2 Example of Microcosm Data Table .75 Table A-1 Aerobic Respiration Processes for MtBE . A-7 Table A-2 MtBE Degrading Microorganisms A-8 Table A-3 Anaerobic Processes for MtBE. A-9 Table A-4 Biodegradation of TBA. A-10 Table A-5 MtBE-Specific Attenuation Issues A-11 Table B-1 Ph
24、ysiochemical MtBE Attenuation Mechanisms B-10 Table B-2 Methods for Inferring Groundwater Flow and Chemical TransportB-11 Table D-1 Measurement Methods for Hydraulic Data. D-4 Table D-2 Groundwater Sampling Equipment. D-5 Table D-3 Field Test Methods for Groundwater Analysis. D-6 Table E-1 Data Qual
25、ity CriteriaE-3 FIGURES Figure 2-1 Flow Chart Showing Stepwise Approach for Using the Three Tiers of Data 16 Figure 4-1 Example Conceptual Site Model .39 Figure 4-2a Example Rose Plot.43 Figure 4-2b Example Rose Plot.44 Figure 4-3 Concentrations of MtBE, Benzene, and Xylene in Groundwater in a Monit
26、oring Well with a NAPL Source .48 Figure 4-4 Concentrations of MtBE, Benzene, and Xylene in Groundwater in a Monitoring Well with a Vapor Source48 Figure 4-5 Typical Plot of Concentration vs. Time.50 Figure 4-6 Typical Isopleth Maps53 TABLE OF CONTENTS (Continued) Figure 4-7 Hypothetical Source Area
27、 MtBE and TBA Concentrations as a Function of NAPL Saturation and MtBE and TBA Content of Gasoline .55 Figure 4-8 Example of How to Discretize a Plume Transect 60 Figure 4-9 Presentation of Mass Flux Data .61 Figure 4-10 Typical Plot of Geochemical data69 Figure 4-11 Plot of Isotopic Data Demonstrat
28、ing Natural Biodegradation of MtBE72 Figure F-1 Worksheet for Concentration Trend Analysis using the Mann-Kendall Test F-2 Figure F-1a Mann-Kendall Analysis for MtBE at Well with Obviously Decreasing Trend.F-3 Figure F-1b Mann-Kendall Analysis for MtBE at Well with Slightly Decreasing Trend.F-4 Figu
29、re F-1c Mann-Kendall Analysis for MtBE at Well with No TrendF-5 Figure F-2a MtBE Concentration Versus Time for Well with Obviously Decreasing Trend.F-6 Figure F-2b MtBE Concentration Versus Time for Well with Slightly Decreasing Trend.F-7 Figure F-2c MtBE Concentration Versus Time for Well with No T
30、rendF-8 Figure G-1 Attenuation Rate Sample Calculation. G-3 EXECUTIVE SUMMARY Methyl tert-butyl ether (MtBE) has been produced commercially in the United States since 1979 and has been used as both an octane enhancer and oxygenate in gasoline. Over the last few years, MtBE-oxygenated gasoline has be
31、en phased-out of most US markets, though it continues to be used in various international markets. Releases of MtBE-containing gasoline have led to the detection of MtBE in soil, surface water, and groundwater. MtBE may be removed from environmental media by some of the active or passive strategies
32、typically employed for gasoline remediation, including Monitored Natural Attenuation (MNA). The objective of this protocol is to provide a framework for incorporating MtBE (and other oxygenates or degradation byproducts e.g., tert-butyl alcohol) MNA into an overall site remediation strategy at any s
33、ite where these compounds have been released to the subsurface. The fundamental approaches for MNA were documented by EPA and ASTM beginning in the late-1990s. This protocol follows these approaches in principle and includes specific data needs and evaluation flowcharts for selecting and implementin
34、g an MNA strategy for MtBE. This technical protocol addresses data collection, evaluation, and interpretation procedures that consider the physical, chemical and biological properties of MtBE and other oxygenates and degradation byproducts. A tiered approach is provided that can be used by stakehold
35、ers to interpret several lines of evidence to evaluate natural attenuation on a site-specific basis. Several resources are provided to support an MNA evaluation, including: a review of basic scientific principles relevant to the evaluation of MtBE natural attenuation, including biodegradation and ph
36、ysicochemical attenuation mechanisms; a discussion of data that can be used to assess MtBE (and other oxygenates or degradation byproducts) natural attenuation; technical references for relevant chemical properties, analytical methods, and field sampling techniques; guidance for data quality assuran
37、ce and interpretation, including statistical analysis; and guidance on the presentation of natural attenuation data/information to facilitate regulatory and other stakeholder review and acceptance of MNA remedies. 1 1 INTRODUCTION 1.1 Purpose and Objectives of Document Releases of MtBE-containing ga
38、soline have led to the detection of MtBE in soil, surface water, and groundwater. Methyl tert-butyl ether may be removed from environmental media by some of the active or passive strategies typically employed for gasoline remediation, including Monitored Natural Attenuation (MNA). However, based upo
39、n the physical and chemical properties of MtBE, the data needs and evaluation procedures for selecting and implementing an MNA strategy for MtBE differ from those typically used for other gasoline constituents. This technical protocol addresses data collection, evaluation, and interpretation procedu
40、res that consider the properties of MtBE when evaluating natural attenuation. Natural attenuation refers to all biological and abiotic processes that dilute, remove, degrade, or detoxify chemicals in the environment (USEPA, 1999 and 2001). Natural attenuation has become an accepted strategy for many
41、 classes of chemicals provided that risks can be managed effectively and the remedial timeframe is comparable to other practicable alternatives. Evaluation of the performance of natural attenuation strategies relies upon monitoring networks that can quantify changes in chemical concentration and/or
42、mass and related geochemistry and hydrology that influence, or are products of, attenuation processes. This remedial approach is often referred to as MNA. This protocol provides guidance to those interested in assessing MtBE natural attenuation, and those with the responsibility of reviewing such wo
43、rk. This manual is designed to: Present the basic scientific principles relevant to the evaluation of MtBE natural attenuation; Develop a framework for assessing the feasibility of incorporating MtBE natural attenuation into an overall site strategy; Identify those data that can be used to assess Mt
44、BE natural attenuation; Provide a concise technical reference for relevant chemical properties, analytical methods, and field sampling techniques; Provide protocols and guidance for data interpretation; and Provide guidance on the presentation of natural attenuation data/information to facilitate re
45、gulatory and other stakeholder review and acceptance of MNA remedies. This protocol is not a prescriptive manual to be followed step by step for all sites with MtBE. Rather, the protocol helps stakeholders identify and quantify attenuation mechanisms and assess whether these mechanisms provide for s
46、ufficient MtBE natural 2 attenuation in a particular environment. This protocol may be used at any stage of a site evaluation, from site discovery to remedy re-evaluation. The material presented in this protocol is intended to support work plan development, site investigation, data analysis, and dec
47、ision making for regulators, site managers, and practitioners. The remainder of this document is organized as follows: The remainder of Section 1 summarizes the regulatory status of MNA for MtBE and discusses attenuation mechanisms specific to MtBE; Section 2 presents a tiered approach that can be u
48、sed by stakeholders to interpret several lines of evidence to evaluate natural attenuation on a site-specific basis; Section 3 provides methods for field data collection and chemical analysis; and Section 4 describes data evaluation and presentation methods for the three tiers of data. 1.2 Regulator
49、y Status of MNA of MtBE Monitored Natural Attenuation as a tool for the remediation of petroleum hydrocarbons has reached wide-spread acceptance among State and Federal regulators since the late 1990s (ASTM, 1998; USEPA, 1998 and 2001; Wiedemeier and Chapelle, 2000). The stability of benzene, toluene, ethylbenzene, and xylene (BTEX) plumes at sites with a continuing primary source of contamination, or the rapid shrinkage of these plumes, especially following source removal (only secondary source as defined in Section 2.1.2 remaining), has
