1、Designation: E 1624 94 (Reapproved 2002)Standard Guide forChemical Fate in Site-Specific Sediment/Water Microcosms1This standard is issued under the fixed designation E 1624; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year
2、 of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This guide provides procedures and criteria for thedevelopment and use of sediment/water microcosms for labo-rato
3、ry evaluations of the fate of chemical substances in theenvironment. It does not specify specific microcosms but itestablishes minimum criteria for distinguishing acceptablemicrocosms from those that may be incomplete or inappropri-ate for site-specific extrapolation (see 5.1 and 10.1).1.2 This stan
4、dard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 A
5、STM Standards:2E 729 Practice for Conducting Acute Toxicity Tests withFishes, Macroinvertebrates, and AmphibiansE 1279 Test Method for Biodegradation By a Shake-FlaskDie-Away Method2.2 U.S. EPA Standard:Toxic Substances Control Act Test Guidelines; ProposedRule, Site-Specific Aquatic Microcosm Test3
6、3. Terminology3.1 Description of Term Specific to This Standard:3.1.1 microcosman intact, minimally disturbed portion ofan ecosystem brought into a laboratory for study undercontrolled experimental conditions.4. Summary of Guide4.1 This guide provides guidance on the development, use,and evaluation
7、of microcosm studies used to evaluate the fateof chemical substances in specific aquatic ecosystems. Itestablishes minimum criteria for distinguishing acceptablesite-specific fate microcosms.5. Significance and Use5.1 The fate of chemicals released to the environment maybe evaluated in the field or
8、in laboratory studies. This guideprovides direction on the development, use, and evaluation ofmicrocosm studies that simulate a specific aquatic ecosystemand include sediment and relevant biota.Akey objective in theuse of site-specific microcosms is the ability to extrapolateinformation obtained in
9、the laboratory system to field situationswith a reasonable degree of confidence.5.2 Field studies can obtain important information about thefate of chemicals in a particular ecosystem but have manydisadvantages. In field studies, environmental variables, ingeneral, cannot be controlled and the study
10、 may be subject towide fluctuations in variables such as temperature, rainfall orsunlight. Introduction of a chemical into an ecosystem mayproduce an unacceptable environmental risk. Furthermore,field studies often are prohibitively expensive.5.3 Some environmental fate studies use structural or syn
11、-thetic communities (not site-specific microcosms) created byplacing water, soil or sediment, plants, animals and microbiotain a container according to an established protocol. Somesynthetic communities have been specifically designed toexamine the fate of chemical substances in aquatic environ-ment
12、s (that is, Metcalf et al. (1)4and Isensee and Tayaputch(2). These synthetic communities provide reproducible envi-ronments in which to evaluate and rank chemicals according totheir fate but extrapolation to specific ecosystems is difficult.This is because they lack complex population structures and
13、processes analogous to specific natural ecosystems. In addition,they frequently contain a biomass of organisms that is notscaled to the volume of water or sediment, thereby givingexaggerated rates of chemical metabolism.5.4 A microcosm replicates many of the processes affectingthe fate of a chemical
14、 in a complex ecosystem. A microcosmcan be examined under controlled laboratory conditions in theabsence of certain variables that might interfere with anunderstanding of a particular process. Microcosms provide anopportunity to manipulate variables and to study their effectsand interactions. Microc
15、osms also offer replication possibilitiesfor assessing environmental variability, an advantage that is notavailable from field studies.1This guide is under the jurisdiction of ASTM Committee E47 on BiologicalEffects and Environmental Fate and is the direct responsibility of SubcommitteeE47.04 on Env
16、ironmental Fate of Chemical Substances.Current edition approved July 15, 1994. Published September 1994.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standard
17、s Document Summary page onthe ASTM website.3Federal Register, Vol 52, No. 187, 1987, pp. 3635236360.4The boldface numbers given in parentheses refer to a list of references at theend of the text.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, Unit
18、ed States.5.5 Microcosms can be used to examine the significance ofvarious fate processes. By examining test compounds inmicrocosms it is possible to determine the relative effects ofvarious fate processes (for example, biotic versus abiotic). Thismakes it possible to focus on critical processes and
19、 considersite-specific environmental situations where these processespredominate or are absent. Although some fate processes suchas hydrolysis or partitioning to sediments may be quantifiedadequately in simpler studies (for example, shake-flask oraquaria tests) others such as bioturbation may requir
20、e thecomplexity of a microcosm for adequate assessment. Animportant aspect of microcosm testing is determining thesignificance of biological processes in environmental fate. Bystudying test compound fate in sterilized microcosms, the roleof bioturbation (that can distribute a chemical deep in sedime
21、ntbeds) can be assessed along with biodegradation.5.6 The following are examples of chemical fate informa-tion that might be obtained in microcosm studies.5.6.1 How long a chemical substance will persist in itsparent form in a particular environment,5.6.2 Whether the fate of a chemical is primarily
22、dependenton biotic or abiotic processes,5.6.3 The effect on the fate of a chemical by the presence ofplants that may take up the chemical and store or metabolize itand that provide additional surfaces for microbial colonization,5.6.4 The effect on the fate of a chemical by the activity ofbenthic org
23、anisms that move water and sediment, and5.6.5 The effect of nutrient flux at the water sedimentinterface on the biodegradation of chemicals in the watercolumn and in the sediment.6. Preliminary Studies6.1 A shake-flask test with site water and sediment (forexample, using Test Method E 1279) is recom
24、mended toprovide preliminary information about the fate of a testcompound. Biotic and abiotic degradation rate constants, in thepresence and absence of sediment, can be determined with thistest along with an indication of potential sorption to sediments.An example of data for the pesticide fenthion
25、generated fromboth shake flask and microcosm tests has been reported (3, 4).The preliminary study may identify those fate processes thatshould receive close attention during a microcosm study andprovide guidance on sampling frequency. Some test com-pounds, such as those that persist for a very short
26、 time periodin shake flask tests, may not require further testing in amicrocosm. An appropriate reference chemical such as methylparathion (5) or LinearAlkylbenzene Sulfonate (LAS)5may beused with the shake flask and microcosm tests.7. Design Features for Sediment/Water Microcosms7.1 Size:7.1.1 Beca
27、use of their size, microcosms can model only asmall part of any aquatic ecosystem. They may vary in sizefrom a fraction of a litre to several hundred litres. Smaller sizesmaximize the advantages of microcosm use, including opera-tion within a controlled laboratory environment, replicability,containm
28、ent of toxic chemicals and simplification of dosingand mixing.7.1.2 Amicrocosm should be sufficiently large to permit theremoval of water and sediment samples during the course ofthe study without significantly affecting surface to volumeratios over the course of an experiment and without signifi-ca
29、ntly depleting either the water or sediment volumes. Micro-cosms also must be large enough to readily accommodatemonitoring probes, mixing apparatus, etc.7.1.3 The inclusion of relatively large biotic species (forexample, clams and large plants) may not be appropriate inmicrocosms of only a few litr
30、es size. Small microcosms,however, may be the most appropriate for studies of chemicalfate processes such as biodegradation and sorption, whichgenerally are not affected significantly by this size constraint.7.1.4 Since the size and design of a microcosm dependsprimarily on the issue that is being a
31、ddressed (6, 7), no “ideal”microcosm design can be recommended. For example, studiesfocusing on the interaction of a test compound with sediment,benthic macrophytes, bioturbating-macrofauna, or small fisheach require specific modifications to accommodate the neces-sary compartments/organisms. A vari
32、ety of water/sediment,site-specific microcosms have been described for studying thefate of xenobiotic compounds in the aquatic environments.These test systems vary in size from Ecocores, used by Spain,et al., containing approximately 175 mLof water (8), to the 140L test systems used by Perez et al.
33、(9), with many intermediatesizes (3, 10, 11, 12).7.2 Water:7.2.1 Collect water for the microcosm from the field siteabove or nearly above the site of sediment core collection.Collect water by hand bucketing or non-destructive pumping.If the water column in the natural system is stratified, themicroc
34、osm water should contain samples taken from represen-tative depths.7.2.2 If the site water is to be the source of the testcompound, sampling containers should be composed of mate-rials such as glass or fluorocarbon plastics to minimizesorption. Take care to avoid the use of plastics (for example,pla
35、sticized polyvinyl chloride) that may leach plasticizers intothe water. Transport water samples to the test facility withminimum delay and maintain field temperatures as close aspossible. Effects of containerization (“wall effect”) may occursoon after collection, and thus shipment over long distance
36、smay be detrimental. If, for some reason water must be held inthe laboratory overnight, gently stir it using a magnetic stirrerand loosely cover the water container to prevent dissolvedoxygen depletion.7.3 Sediment:7.3.1 Because of the well-documented significance of sedi-ment in the biodegradation
37、of many chemical substances (13,14, 15, 16), the microcosm designs covered by this guideinclude intact sediment cores.5Linear Alkylbenzene Sulfonate (LAS) is available from Quality AssuranceResearch Division, Room 525, Environmental Monitoring Systems Laboratory, USEPA, Cincinnati, Ohio 45168.E 1624
38、 94 (2002)27.3.2 Site-specific extrapolation of sediment-enhanced bio-degradation information must take into consideration the watercolumn volume to sediment surface area ratio. Sediment-mediated processes will be accentuated in shallow bodies ofwater and may be insignificant relative to processes i
39、n deepwater.7.4 Coring:7.4.1 For microcosms consisting of sediment and a watercolumn, it is important to obtain sediment cores that are asintact as possible to preserve the structural integrity of thesample, including the redox gradient and the benthic commu-nity.7.4.2 The inner diameter of the core
40、r may be designed suchthat the microcosm sediment surface area to water volume ratioequals that of the natural system.7.4.3 For some microcosms (17, 18) the corer becomes the“microcosm”. Insert a suitably sized glass tube (for example,the 3.5 cm diameter and 40 cm length tube used by Spain et al.(17
41、), into the sediment to a depth of 8 cm or more, sufficient toinclude relevant biological activity. Seal the top with a siliconestopper. Carefully remove the tube from the sediment and closethe bottom of the tube with another silicone stopper. Aftercarefully transporting the cores back to the labora
42、tory, adjustthe water volume of the microcosm to the desired watervolume to core surface area ratio.7.4.4 Alternatively, obtain an intact core in the field andextrude it into a microcosm vessel (10, 19, 20). A simple andeffective coring device can be made of clear acrylic tubing withserrations along
43、 the bottom for cutting through plant roots. Sealthe top with an acrylic disc containing a hole that can beplugged with a stopper. Insert the corer into the sediment to adepth equal to or greater than the depth of biological habitationor activity. This could range up to 20 cm in depth (21). Plug the
44、hole on top with a stopper and carefully raise the corer andinsert it into the microcosm vessel. Remove the stopper and liftthe corer out of the microcosm, leaving the sediment plugintact. For large water volume to sediment surface area ratios,place the corer in a glass dish (for example, crystalliz
45、ationdish) with a diameter slightly larger than the corer and theentire assembly (core + corer + dish) placed into the micro-cosms (19). Some sediments are very difficult to work with andseveral attempts may have to be made before an intact core canbe lifted and transferred.7.4.5 Since coring and tr
46、ansport from the field often sus-pends sediment in the overlying water column, a carboy of sitewater is also collected. At the laboratory, carefully siphon offthe overlying water column and gently add new water to thedesired volume.7.4.6 Scuba equipment may be required to obtain undis-turbed cores i
47、n relatively deep water.7.5 Dosing Microcosms:7.5.1 Maintain microcosms in either flow-through or static-renewal modes. For the latter, replace a fixed percentage ofmicrocosm water with fresh site water.Aflow-through mode isthe most complex to operate but may avoid nutrient deficien-cies and build-u
48、p of metabolic waste products. A one-timepulse dose of test compound may be applied in conjunctionwith any of these modes. For a pulse dose in a flowing system,the relationship between molecular overturn (partial replace-ment) time and the flow rate and volume of the microcosmchamber is characterize
49、d in a graph by Sprague (22).7.5.2 For flow-through systems employing relatively largeconcentrations of test compounds, as in the case of effluenttesting, a pump or headbox/siphon arrangement is recom-mended. All parts of the pump and delivery tubing that comeinto contact with either test compound or diluent water shouldbe inert and should minimize sorption of the test substance.7.5.3 Test substance may be dissolved in a carrier (ideally,sterile diluent water) and the resulting stock solution meteredinto flowing diluent water. Use peristaltic pumps utilizingsilicone tubing for adding
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