by M. Lambert, B.A. Leven, and R.M. New Methods of Cleaning Up Heavy in and Innovative solutions to an environmental problem This publication is published by the - ous Substance Research Centers as part of There are several options for treating Joplin. Here, mine spoils (locally called their Technical Outreach Services for Com- or cleaning up soils contaminated with ) cover much of the open space in- munities (TOSC) program series of Environ- heavy . This paper discusses side the , and contain high levels of mental Science and Technology Briefs for three of those methods. , , and . Heavy metal Citizens. If you would like more information about the TOSC program, contact your re- can be carried with gional coordinator: Introduction particles swept away from the initial At many sites around the nation, heavy areas of by wind and rain. Northeast HSRC metals have been mined, smelted, or Once these soil particles have settled, New Jersy Institute of Technology Otto H. York CEES used in other . The the may spread into the 138 Warren St. waste (, smelter , etc.) has surroundings, polluting new areas. Newark, NJ 07102 sometimes been left behind to pollute Cleanup (or remediation) (201) 596-5846 surface and ground water. The heavy available for reducing the harmful ef- Great Plains/Rocky Mountain HSRC metals most frequently encountered in fects at heavy metal-contaminated sites Kansas State University this waste include , cadmium, include excavation (physical removal of 101 Ward Hall , , lead, , and the contaminated ), stabiliza- Manhattan, KS 66506 zinc, all of which pose risks for human tion of the metals in the soil on site, (800) 798-7796 health and the environment. They typi- and the use of growing plants to stop Great Lakes/Mid-Atlantic HSRC cally are spread out over former indus- the spread of contamination or to ex- A-124 Research Complex- trial sites and may cover acres of land. tract the metals from the soil State University Figure 1 shows one such site in south- (). East Lansing, MI 48824 (800) 490-3890 western Missouri, near the city of

South/Southwest HSRC Environmental Science & Technology Program Georgia Tech Research Institute 229 Baker Building Atlanta, GA 30332 (404) 894-7428

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Acknowledgment: Although this article has been funded in part by the U.S. Environmen- tal Protection Agency under assistance agree- ment R-819653, through the Great Plains/ Rocky Mountain Hazardous Substance Re- search Center, it has not been subjected to the agency’s peer and administrative review Figure 1. Mine spoils called chat, near the city of Joplin, Missouri. and, therefore, may not reflect the views of Wind and rain can cause the chat to scatter, spreading heavy metal the agency. No official endorsement should contamination. be inferred. ENVIRONMENTAL SCIENCE AND TECHNOLOGY BRIEFS FOR CITIZENS PAGE 2

Excavation Table 1. Comparative costs for different types of heavy metal soil remediation Excavation and physical removal of the (Schnoor, 1997). soil is perhaps the oldest remediation TrnoitaidemeRfoepy Cdetemcibuc/tso eriuqeRemiT method for contaminated soil. It is still in use at many locations, including resi- E0lavomerdnanoitavacx $s04$-001 htnom9-6 dential areas contaminated with lead utisnI noitaxif $s002$-09 htnom9-6 in southwestern Missouri. Advantages )stnemdnemaliosgnidulcni( of excavation include the complete re- moval of the contaminants and the rela- P0noitcartxeotyh $s4$-51 htnom06-81 tively rapid cleanup of a contaminated site (Wood, 1997). Disadvantages in- ity of heavy metals on site has many lead. Chemical reactions between the clude the fact that the contaminants advantages over excavation. One way and the lead cause a min- are simply moved to a different place, of stabilizing heavy metals consists of eral to form called lead . where they must be monitored; the risk adding chemicals to the soil that cause Lead pyromorphite and similar miner- of spreading contaminated soil and dust the formation of that contain als called heavy metal are particles during removal and transport the heavy metals in a form that is not extremely insoluble. This means the of contaminated soil; and the relatively easily absorbed by plants, animals, or new minerals cannot dissolve easily in high cost. Excavation can be the most people. This method is called in situ (in water (Lambert et al., 1997). This has expensive option when large amounts place) fixation or stablization. This two beneficial effects. The minerals of soil must be removed or disposal as process does not disrupt the environ- (and the heavy metals) cannot be eas- hazardous or is required ment or generate hazardous wastes. ily spread by water to pollute streams, (see Table 1). Instead, the heavy metal combines with lakes, or other . Also the the added chemical to create a less phosphates are less likely Stabilizing Metals in compound. The heavy metal remains to enter the by being ab- the Soil in the soil, but in a form that is much sorbed into plants or animals that may Heavy metals can be left on site and less harmful. eat soil particles. Table 1 shows the cost treated in a way that reduces or elimi- of treating the soil by in situ fixation nates their ability toadversely effect One example of in situ fixation of heavy may be about half the cost of excava- human health and the environment. metals involves adding phosphate fer- tion and disposal of heavy metal con- This process is sometimes called stabi- tilizer as a soil amendment to soil that taminated soil. This method is rela- lization. Eliminating the bioavailabil- has high amounts of the heavy metal tively rapid and takes about the same amount of time as excavation. Use of Plants Growing plants can help contain or re- duce heavy metal pollution. This is of- ten called phytoremediation (EPA, 1988). It has the advantage of relatively low cost and wide public acceptance (Schnoor, 1997). It can be less than a quarter of the cost of excavation or in situ fixation. Phytoremediation has the disadvantage of taking longer to accom- plish than other treatment . Plants can be used in different ways. Sometimes a contaminated site is simply reveg- etated in a process called phytostabilization. The plants are used to reduce wind and water that spread containing heavy metals. In one example, grass or tree buffers could reduce loss from Figure 2. Test plots for evaluating revegetation of chat material in , the chat piles at a contaminated site in Kansas. Here, tall fescue is being grown as a way of reducing sediment runoff Galena, Kansas, anywhere from 18% and the spread of heavy metal pollution. The bare center plot is a control in to 25% (Green, et al. 1997). If all of the which fescue was not planted. ground could be revegetated, sediment ENVIRONMENTAL SCIENCE AND TECHNOLOGY BRIEFS FOR CITIZENS Page 3 loss could be cut by approximately 70%. Conclusions sis Center Technology Evaluation However, it would be necessary to find During the 1990’s, new methods have Report TE-98-01, 37. plants that could tolerate high levels of been developed to clean up heavy metal- heavy metals. Figure 2 shows a series contaminated soil. The expensive pro- Wood, P., 1997, Remediation Methods of several revegetation test plots on the cess of excavating and disposing con- for Contaminated Sites: in R. chat piles in Galena, Kansas. taminated soil has been augmented with Hester and R. Harrison, Contami- new methods that treat the soil in place. nated Land and Its Reclamation, Another way plants can be used to clean In situ fixation is a process that cre- the Royal Society of , up heavy-metal contaminated soil is ates new chemical coumpounds in Cambridge, p. 47 – 71. called phytoextraction. Some plant spe- which heavy metals are much less cies can take up heavy metals and con- available to living things. This on-site U.S. Environmental Protection centrate them in their tissue. The cleanup is less disruptive to people’s Agency (US EPA), 1998, A Citizen’s plants can be harvested and the con- lives and to the environment compared Guide to Phytoremediation, Office taminated plant material disposed of to excavating and disposing contami- of Waste and Emergency safely. Sometimes soil amendments are nated soils elsewhere. Phytoreme- Response (5102G) EPA 542-F-98- added to the soil to increase the ability diation uses plants by several methods 001 August 1998. of the plants to take up the heavy met- to contain or clean up heavy metals. als. One type of plant used for this Phytoremediation has the benefit of be- US EPA, 2000, Introduction to purpose is called Indian mustard. This ing a relatively low-cost, natural solu- Phytoremediation, National Risk plant has been used to extract lead from tion to an environmental problem. Management Research Laboratory, soil and reduce lead contamination at Office of Research and Develop- various contaminated sites. Other More information on these and other ment, EPA/600/R-99/107, February plants that may be used for new cleanup methods for contaminated 2000. phytoextraction include alfalfa, cab- soils and water is on the internet at bage, tall fescue, juniper, and poplar many sites, including . ABOUT THE AUTHORS: Michael Lambert has a B.S. from Kansas State University, Another way plants are used to treat References an M.S. from Indiana University, and a Ph.D. heavy metal contamination is called Green, R., L. Erickson, R. Govin- from the University of Kansas, all in geol- rhizofiltration (EPA, 2000). In this daraju, and P. Kalita, 1997, ogy. He works for the TOSC and method, heavy metals are removed di- Modeling the Effects of Vegetation Brownfields programs of the Great Plains/ rectly from water by plant roots. The on Heavy Metals Containment: 12th Rocky Mountain Hazardous Substance Re- plants are grown directly in water or Conference on search Center. in water rich materials such as sand, Research, Kansas City, Missouri, using aquatic species or hydroponic pp. 476-487. Blase Leven has a B.S. from the University methods. In field tests sunflowers on of -Davis, and an M.S. from the floating rafts have removed radioactive Lambert, M., G. Pierzynski, L. Colorado School of Mines, both in . metals from water in ponds at Erickson, and J. Schnoor, 1997, He is a program manager for the Great Chernobyl, and other plants removed Remediation of Lead-, Zinc-, and Plains/Rocky Mountain Hazardous Sub- metals from mine drainage flowing Cadmium-Contaminated Soils: in stance Research Center. through diversion troughs (EPA, 2000). R. Hester and R. Harrison, Con- taminated Land and Its Reclama- Ryan Green has a B.S. and an M.S. from Plants used for phytoextraction may ac- tion, the Royal Society of Chemis- Kansas State University, in chemical engi- cumulate high concentrations of met- try, Cambridge, p.91 - 102. neering. He works for the Pollution Pre- als. Fences or other ways to limit ac- vention Institute, a non-regulatory environ- cess to people and animals, and disposal Schnoor, J., 1997, mental assistance program at Kansas State of plant matter as special waste is some- Phytoremediation: Groundwater University. times necessary. Remediation Technologies Analy-

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