RESEARCHWATCH
MEASUREMENTS Detecting herbicides The imidazolinones, a new class of herbicides used in a wide variety of agricultural applications, are low-use rate herbicides and therefore need to be measured in low parts per billion concentrations in soil. S. J. Stout and colleagues developed a new method to measure these compounds with decreased sample preparation time and improved sensitivity. The method incorporates microwave-assisted extraction, solid-phase extraction cleanup, and gas chromatography/ electron capture negative chemical ionization mass spectrometry analysis with selected ion monitoring. The authors averaged 92% recovery from four soil types at a fortification from 1 to 50 DDb with a 13% RSD They processed 12 samples for analin 2 h with an additional 30 min per sample for instrumental analysis (Anal Chem 1996 68 653-58)
QSARs for inorganics Although quantitative structureactivity relationships (QSARs) often have been used to predict environmental behavior of organic compounds, few such relationships exist for inorganic substances. M. C. Newman and J. T. McCloskey determined QSARs for eight divalent metals in the Microtox aquatic toxicity assay. Toxicities of Ca(II), Cd(II), Hg(II), Mg(II), Mn(II), Ni(II), Pb(II), and Zn(II) were correlated with decreasing acidity. Metal ion acidity is linked to the metal's affinity for binding to important biochemicals. The authors also were ctble to pre*dict metal interactions The results suggested that similar correlations may be possible for other aauatic toxicitv tests (Environ Toxicol Chem 1996 15 275-81)
Characterizing PAHs Characterization of polycyclic aromatic hydrocarbons (PAHs), carcinogenic compounds formed by incom-
Characterizing colloids Environmental colloids in soil are believed to play an important role in the geochemistry, transport, and bioavailability of contaminants. However, data are scarce because methods generally do not allow artifact-free isolation and characterization of colloidal materials. R. M. Burgess and co-workers assessed ultrafiltration and reverse-phase chromatography as methods for isolating marine sediment interstitial colloids. They found that reverse-phase chromatography was a suitable method for quantifying interactions between colloids and polychlorinated biphenyls (PCBs). Data were reproducible, and K values agreed with the literature. In contrast, ultrafiltration suffered from colloidal break-through problems and sorption of dissolvedphase PCBs to the filter. (Environ. Sci. Techno!..,his issue, ,923-32)
plete fuel combustion, has focused on die lower atomic weight species, which are more volatile. A. L. Lafleur and colleagues used atmospheric pressure chemical ionization mass spectrometry (APCI-MS) to greatiy extend the molecular weight range of PAHs that can be characterized. They developed two techniques: highperformance liquid chromatography (HPLC) combined witii APCI-MS and direct liquid introduction (DLI) combined with APCI-MS. Both used a heated nebulizer to introduce sample. The HPLC technique separated and analyzed PAHs up to molecular weights of higher weights were not achievable for the chromatography The DLI technique characterized PAHs at molecular weights between 400 and 2000 amu (/ Am Soc Mass Spectrom 1996 7 276-86)
POLICY Technology barriers N. Derzko examined barriers to sustainable development such as legal and regulatory restraints on environmental technologies. Status quo methodologies and programs, including die U.S. patent system and command-and-control, technologybased standards established under the Clean Air Act, hinder technological advancement. Derzko found that cost, time, and uncertainty determine whether new environmental technologies are developed and
0013-936X/96/0930-233AS12.00/0 © 1996 American Chemical Society
should be factored into future regulatory and legal agendas. She proposes establishing an environmental patent system, restructuring environmental permits, and using treaties as a means to propel the development and use of environmental technologies. (Harvard Environ. Law Review 1996, 20, 3-59)
RECYCLING Laser-printed paper Increased demand for recycled paper products has resulted in an increased need for high-quality recycled fiber. Office paper contains such fiber, but laser-printed toners are difficult to remove by conventional de-inking. O. U. Heise and co-workers investigated industrialscale, enzymatic de-inking. Pulp strength was maintained compared witii a conventional control but oo~ ticcil properties were mixed. Effluent oxygen demand was similar to the control, while toxicity reportedly decreased. Results indicated that enzymatic de-inking is a promising alternative for recycling mixed office waste papers (TAPPIJ 1199 77 207-12)
REMEDIATION Irradiating dioxins Dioxin in soil is a significant remediation problem. Current techniques
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such as incineration, bioremediation, chemical treatment, and photolysis all have significant disadvantages, not the least of which is cost. R. J. Hilarides and colleagues evaluated gamma irradiation used to degrade dioxin in soil. They used 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) as a model compound, applied it to soil, and exposed the soil to a dose of 800 kGy. Results indicated about 99% degradation. Additionally, a dose of 450 kGy reduced TCDD in a native soil by nearly 75%. The results demonstrated gamma irradiation as a potential alternative for degrading dioxins in soil. {Water Environ. Res. 1996, 68, 178-87)
Cr(VI) removal B. T. Nivas and co-workers developed a method to remediate chromate-contaminated subsurface environments. Cr(VI) is toxic and mutagenic, and in the subsurface, its highly mobile anionic forms pose significant risk of contaminating groundwater. The researchers achieved optimal removal of Cr(VI) from contaminated soil samples by using a combined micellar surfactant-complexing agent system. The extent of chromate elution by this system was 12 times that of water The authors determined that ion exchange is the dominant mechanism for Cr(VI) removal by surfactants alone Several other surfactants were also tested but they were more susceptible topreciDitation and sorption {Water Res 1996 30 511-20)
Modeling the behavior of humic substances M. F. Benedetti and co-workers used a Donnan model to consider electrostatic interactions and account for the effect of salt concentrations on the charge of humic acid molecules. They applied the model to interpret proton binding by humic and fulvic acids. In this approach, the volume of the Donnan phase was assumed to change with salt level, not charge. The authors found that the Donnan model was physically realistic for the swelling gel-like structure of humic acids but not for fulvic acids which have smaller molecules with limited swelling and shrinkage capabilities Results suggested that humic acid volumes may be more dependent on ionic strength than on pH The authors propospri that t h k information could promote understanding of cirganic pollutant infpractinnQ in natural
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Infants' DDT intakes Elevated levels of DDT and its degradation products DDE and DDD have been found in the sediments and fish of Washington's Yakima River. K. Marien and D. Laflamme examined the health implications of consuming DDT-contaminated fish from the river. They developed a tolerable daily intake for DDT and DDE for nursing infants based on epidemiological and toxicological literature and compared it with the infants' estimated daily intake level of DDT and DDE They estimated infant daily intake levels between 2 x 10~2 mg/kg-day and 2 5 x 10"2 mg/kg-dav which exceeded die tolerable daily intake level of 5 x 10"3 mg/kg-day for
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SEM-to-AVS ratio of 1 0 did not provide additional information from the sediment sairmles The authors observed variability in the SEM-to-AVS ratio from sediments sampled at different locations and at different depths of the same location {Environ Toxicol Chem 1996 15 286-93)
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SOILS these compounds. The results suggested that eating subsistence quantities of contaminated fish may expose newborn infants to unsafe levels of DDT and DDE. {Risifc Anal. 1995, 15, 709-17)
SEDIMENTS Metals extraction
RISK
Metal bioaccumulation J. M. Besser and colleagues studied the spatial distribution of acidvolatile sulfides (AVSs) and the simultaneously extracted metals (SEMs) copper and zinc in fresh water sediments from a river previously affected by mining. The growth and bioaccumulation of metals by midge larvae {Chironomus teutons) exposed to different sediment deptiis and metal concentrations indicated that the bioaccumulation of copper and zinc was associated with sediment SEM-to-AVS ratios. However, die prediction of heavy metal toxicity based
A new method of determining the bioavailability and toxicity of metals in anoxic sediments uses the ratio of acid-volatile sulfide (AVS) to simultaneously extracted metals (SEMs). W. G. Brumbaugh and I. W. Arms studied the method used to extract AVS and SEM to determine whether slight changes would affect the results. Slightly increasing the acid extractant resulted in increased extraction of low concentrations of AVS from the sediment, but this did not occur at high AVS concentrations. Although most SEMs were not affected by acid strength, copper concentrations increased with increased extractant acidity when sediments contained high concentrations of AVS In general increasing extractant acidity decreased the SEM-to-AVS ratio at low concentrations of AVS (Environ Toxicol Chem 1996 ,1 ,82-85)
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Inhibiting landfill methane Methane emission from landfills can be mitigated through oxidation by methanotrophs in the landfill cover soil. E Boeckx and O. Van Cleemput studied the effects of soil moisture content, temperature, and nitrogen nutrient sources on the efficiency of methane oxidation in landfill cover soil. They found optimal soil moisture content between 10 and 20%; methanotrophic activity was inhibited below this and methane diffusion in the soil was decreased above this range. Optimal temperatures were between 25 and 30 °C. Methane oxidation was inhibited by the addition of ammonium nitrogen or organic residues widi high carbon-to-nitrogen ratios because the ammonium competed with methane for active enzyme sites No inhibition occurred with the addition of nitrate nitrogen or organic residues with low carbon-to-nitroeen ratios IT Fnviron dual 1
