Chemical Education Today
Reports from Other Journals
Research Advances by Angela King
Water chemistry is important in many areas, ranging from wildlife biology to fields as diverse as food chemistry and waste management. Current scientific research includes using reptiles to monitor levels of environmental contamination, developing innovative ways to use waste material to improve water quality, and using chemical techniques to determine whether fish are wild or farm-raised. Here is a sampling of modern “wet” chemistry avenues of exploration. Hard-Shelled Bioindicators
Images courtesy Canadian Wildlife Service
Both Canada and the United States are working toward the elimination of persistent toxic compounds from the Great Lakes Basin Ecosystem. Governed by the Great Lakes Water Quality Agreement, their efforts are guided by the designation of substances by Levels of need, with Level I needing virtual elimination as soon as possible. Included on the listing of Level I chemicals are DDT, polychlorinated biphenyls (PCBs), dibenzo-p-dioxins, and dibenzofurans. Polybrominated diphenyl ethers (PBDEs) are flame retardants that were manufactured in North America until 2004, although products containing PDBEs are still being used and one form of PDBEs (Deca-BDEs) is still being produced. PBDEs and PCBs have similar toxicological mechanisms, including aryl hydrocarbon receptor agonism, neurotoxicity, and alteration of thyroid function. Both classes of compounds are also persistent in the environment and bioaccumulate in organisms. The level
of PBDEs in North American organisms continued to increase almost exponentially until at least the turn of the century, despite reduced production. While PCBs are classified as a Level I compound, targeted for virtual elimination, PBDEs have not been designated either Level I or Level II. Given their toxicological similarity to PCBs and rapid increase in recent years, a team of Canadian scientists used snapping turtle (Chelydra serpentina) eggs (Figure 1) to gauge relative levels of PBDEs in the environment and to determine whether levels correlated with distance from urban/industrial centers. Led by Shane de Solla and Kim Fernie of the Canadian Wildlife Service, the team collected eggs from 15 locations, with five eggs taken from each clutch of eggs, over a threeyear period. Egg contents from the same clutch were pooled, extracted, and analyzed for PCBs and organochlorine (OC) pesticides by gas chromatography–electron capture detection (GC–ECD) and gas chromatography–mass selective detection (GC–MSD). The extract was analyzed for PCBEs with GC–MSD. Data were statistically analyzed using ANOVA and Factor Analysis, as is commonly done for sources of complex mixtures of contaminants. The results confirmed that PCB contamination in turtle eggs was associated with industry locations and highest near large urban centers with substantial industry (Figure 2). Many commercial mixtures of PCB compounds are known in the U.S. by the trade name Aroclor, and the profile of contaminants in eggs reflected the composition of specific Aroclor product pro-
Figure 1. Snapping turtle (Chelydra serpentine) eggs can be used as bioindicators of PCB and PBDE contamination in the environment. GC-ECD and GC-MSD indicate that pollutant levels are greatest near urban areas with industrial sites.
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Figure 2. Mean sum-PCB (34 congeners) concentrations (ng/g wet weight) in snapping turtle eggs in lower Canadian Great Lakes collected 2001–2004. The error bars show the ±SD of the mean concentrations. All sites differed from the pooled reference sites (Algonquin Park and Tiny Marsh). Reprinted with permission from Environ. Sci. & Technol. 2007, 41, 7252–7259. Copyright 2007 American Chemical Society.
Journal of Chemical Education • Vol. 85 No. 2 February 2008 • www.JCE.DivCHED.org • © Division of Chemical Education
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files, especially Aroclor 1254, which is in agreement with other species being monitored. Although it is at a lower level than observed in eggs near urban/industry centers, there was PCB contamination in snapping turtle eggs deposited in Algonquin Park, a site far removed from industrial activity and with no known source of PCB contamination. Scientists hypothesize that the PCB levels in these eggs result from airborne deposition. Levels of PCB were higher than PBDE concentrations in the eggs. However, unlike PCB, the relative amounts of specific PBDE congeners in eggs were consistent among nest sites. Turtle eggs reveal bioaccumulation of congeners that comprise the Penta-BDE formulation. Unlike gulls and ospreys previously used to monitor environmental contamination, snapping turtles are nonmigratory and have small home ranges, affording the opportunity to look closely at sources of local contamination and how it affects turtles and their embryonic development. More Information 1. de Solla, S. R.; Fernie, K. J.; Letcher, R. J.; Chu, S. G.; Drouillard, K. G.; Shahmiri, S. Snapping Turtles (Chelydra serpentina) as Bioindicators in Canadian Areas of Concern in the Great Lakes Basin. 1. Polybrominated Diphenyl Ethers, Polychlorinated Biphenyls, and Organochlorine Pesticides in Eggs. Environ. Sci. Technol. 2007, 41, 7252–7259. 2. This Journal has published an experiment utilizing GC to determine PCB levels in river and bay sediment. See J. Chem. Educ. 1996, 73, 558. 3. In its Contemporary History Series, JCE published a perspective on the development of DDT in J. Chem. Educ. 1992, 69, 362. 4. Additional information on the Great Lakes Water Quality Agreement is available online at http://www.ijc.org/en/activities/consultations/glwqa/agreement.php (accessed Nov 2007). 5. More information on this and related research carried out by the Canadian Wildlife Service can be found online at http:// binational.net/solec/English/SOLEC%202004/Tagged%20PDFs/ SOGL%202005%20Report/English%20Version/Individual%20Indicators/4506_Contaminants_in_Snapping_Turtle_Eggs.pdf and http:// wildspace.ec.gc.ca/b-ferniek-e.html (both sites accessed Nov 2007). 6. Background information on environmental monitoring of PCBs was published in an issue paper available online at http://web. ead.anl.gov/ecorisk/issue/pdf/PCB%20IssuePaperNavy.pdf (accessed Nov 2007). 7. More information on Chelydra serpentina may be found at http://animaldiversity.ummz.umich.edu/site/accounts/information/ Chelydra_serpentina.html (accessed Nov 2007).
Improving Water Quality with Chicken Manure? Char is the product of burning plant material in the absence of oxygen. Charcoal is one example of char that humans use extensively—it fuels many grills for summer cookouts. Now a team of scientists have developed a new type of char that may prove just as useful, in two different ways. The United States has a thriving poultry industry. In 2005, 9 billion broilers and 0.3 billion turkeys were produced. With
this incredible number of birds comes an undesired side-product: manure. These feathered creatures produced an amazing 10 million metric tons of manure in 2005. On a small scale, poultry manure is a useful fertilizer and coveted by home gardeners who prize it for its high nitrogen content. But on the mega scale of commercial poultry farming, the manure and soiled poultry litter poses environmental hazards. If consistently disposed of in the same area, it may introduce soil saturation of some elements and increased pollution due to run-off and penetration into groundwater. Plant-based char can be treated to produce activated carbon, which offers a wonderful way to both dispose of byproducts from the production of sugar, soybeans, and nutshells and produce a product with commercial value. Now researchers at the USDA-ARS Southern Regional Research Center in New Orleans have demonstrated that steam-activated poultry manure-based activated carbon possesses excellent adsorption properties for metal ions, and could potentially be used to purify contaminated water. Broiler and turkey litter and cake are forms of poultry manure that differ in age and the quantity of wood shavings (used as bedding) present. Poultry cake has less litter and is fresher when compared to poultry litter. The researchers, led by Isabel Lima, took samples of both poultry litter and cake and milled them to a particle size 20% of the brain dry weight and is the most abundant neural fatty acid. DHA has been linked to visual acuity and normal development of neural tissue in infants. But there may also be compounds present in fish that do not contribute to one’s health. Persistent organic pollutants (POP), such as PCBs and dioxins, are known to accumulate in fish. Levels of both beneficial HUFA and undesired pollutants vary in fish samples, and the team of scientists wanted to know whether these levels could be used to determine whether a fish was wild-caught or commercially cultured. For instance, due to increased aquaculture production, producers must now use plant-derived raw materials in aqua feed, where they traditionally only used fish oil and fishmeal as the basis for the feed. This increase in the amount of plant-derived material in fish diets has led to reductions in levels of both POP and HUFA in farmed fish relative to levels in wild fish. Therefore knowing the origin of fish available for consumption can help consumers make sound decisions. Gordon Bell and colleagues point out that European Union legislation requires that retailers and consumers have information on the geographical origin and production method for seafood. “Due to the global nature of production, similar fish products can be sourced from variable points of origin, and this can lead to instances of mislabeling, both intentional and fraudulent”, their report states. Other considerations, aside from
Journal of Chemical Education • Vol. 85 No. 2 February 2008 • www.JCE.DivCHED.org • © Division of Chemical Education
Photo by Stephen Ausmus, ARS
Figure 3. Manure pellets (top) are converted to activated carbon pellets (left) and can then be ground into either granular (center) or powdered (right) form, depending on end use and filtering task.
Chemical Education Today
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% lipid Figure 5. Individual plots of flesh lipid (A) and choline nitrogen (B) concentration (%) of farmed and wild sea bass and a bivariate plot (C) showing discrimination of wild and farmed bass using these two parameters. Columns assigned different letters are significantly different (P < 0.05). Reprinted with permission from J. Agric. Food Chem. 2007, 55, 5934–5941. Copyright 2007 American Chemical Society.
price, make it important to distinguish between wild and farmed fish, the report notes. Bell’s team developed a new method for identifying fish samples as being wild-caught or farmed by employing chemical techniques. The new test is based on differences found in farmed and wild fish in fatty acid and isotopic compositions (δ13C and δ18O) of total flesh oil, δ15N of the glycerol/choline fraction, and compound-specific analysis of fatty acids (δ13C) by isotope ratio mass spectrometry. 150 g samples of fillets were extracted using isohexane/isopropanol and the resulting oil fraction was used to determine isotope ratios for 18O/16O (by elemental analyzer-combustion-isotope ratio mass spectrometry, EA–IRMS). 15N/14N ratios were determined by EA–IRMS of a concentrated glycerol/choline fraction prepared by saponification of flesh oil followed by reflux extraction and acidification. All isotope ratios determined by IRMS are expressed on a relative scale. The deviation is referred to in delta (δ) units with the notation 0/00,
parts per thousand or per mil with respect to the isotope ratio of an internal standard, Rstd. Fatty acid methyl esters (FAMEs) were prepared by base-catalyzed transesterification of dried flesh oil. FAMEs were then separated and quantified using gas– liquid chromatography in comparison to a standard solution of 12 FAMEs. Wild sea bass had a significantly lower fresh lipid content and higher choline nitrogen content than farmed sea bass (Figure 5). The observed differences originate because of lower levels of marine-derived ingredients in farmed fish diets. Wild sea bass had a significantly lower level of flesh lipids but higher choline nitrogen content when compared to farmed sea bass. Scientists were able to discriminate between wild-caught and farmed sea bass on only these two parameters. With tests done on 10 wild and 10 farmed sea bass, the researchers cite the need to verify the findings on larger samples of different fish. This research team has recently published related work on authenticating production origin of gilthead sea bream using related methodology. More Information 1. Bell, J. Gordon; Preston, Tom; Henderson, R. James; Strachan, Fiona; Bron, James E.; Cooper, Karen; Morrison, Douglas J. Discrimination of Wild and Cultured European Sea Bass (Dicentrarchus labrax) Using Chemical and Isotopic Analyses. J. Agric. Food Chem. 2007, 55, 5934–5941. 2. Morrison, D. J.; Preston, T.; Bron, J. E.; Henderson, R. J.; Strachan, F.; Bell, J. G. Authenticating Production Origin of Gilthead Sea Bream (Sparus aurata) by Chemical and Isotopic Fingerprinting. Lipids 2007, 42, 537–545. 3. This Journal has published numerous articles on chemistry related to marine organisms. For instance, see J. Chem. Educ. 2007, 84, 310 and 2004, 81, 1457. 4. Additional discussion of health benefits and risks of wild and farmed fish is online at http://news.mongabay.com/2005/1223-cornell. html (accessed Nov 2007). 5. More information on this and related research carried out at University of Sterling’s Institute of Aquaculture can be found online at http://www.aquaculture.stir.ac.uk/index.html (accessed Nov 2007).
Supporting JCE Online Material
http://www.jce.divched.org/Journal/Issues/2008/Feb/abs174.html Abstract and keywords Full text (PDF) with links to cited URLs and JCE articles
Angela G. King is Senior Lecturer in Chemistry at Wake Forest University, P.O. Box 7486, Winston-Salem, NC 27109;
[email protected].
© Division of Chemical Education • www.JCE.DivCHED.org • Vol. 85 No. 2 February 2008 • Journal of Chemical Education
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