RESEARCH WATCH
GREEN CHEMISTRY Heavy metal sorbents Polymer microsphere sorbents are among the most promising materials for separating metal ions from aqueous solutions. B. Salih and co-workers characterized sorbents made by chemically attaching Congo Red dye, poly(ethyleneglycoldimethacrylatehyroethyl), to microspheres made from poly[ethyleneglycoldimethacrylate (EGDMA)-hydroxyethylmethacrylate (HEMA)]. Congo Red served as the chelating ligand for adsorption of heavy metal ions. The Congo Redattached poly(EGDMA-HEMA) microspheres showed adsorption rate and a high capacity for cadmium ions After five sorption-desorption cycles the microspheres' capacity as a sorbent did not significantly decrease The researchers concluded that Congo
Global fractionation of PCBs in Arctic lakes The "global fractionation" hypothesis predicts that greater deposition of semivolatile polychlorinated biphenyls (PCBs) will occur in polar regions, with temporal trends in deposition delayed and prolonged compared with temperate regions. D. C. Muir and co-workers tested the hypothesis by collecting sediment cores from 11 remote Canadian lakes. Cores were dated and analyzed for up to 90 PCB congeners. Measurements from nine Arctic lakes showed high proportions of lower chlorinated congeners Furthermore PCBs in the Arctic sedimentary record appeared later (1Q^fte—fifis) than those in midlatitiide and snh-Arctic sites H'nfis-40sl The authors report that the finriings are c o n s i s t e n t VA/ith g l o b a l
fractionation Tprhnnl ,his issup
Red-attached DOIV(EGDMA-HEMA)
microsnheres ma? provide an effective terhnimip for removing cadmiu " f . e o . . cnliitiniT! (j A i P i s iq9fi fin R71-771
PESTICIDES DDT persistence How do land management practices applied 23 years ago affect the persistence and volatility of DDT in soils with high concentrations of the pesticide? W. F. Spencer and colleagues revisited an experimental site at which DDT-contaminated soils were deep plowed, flooded, and/or enriched with organic matter in 1971. All of the DDT isomers in the soil decreased during the 19711994 period of the study. The highest concentrations found in deepplowed unflooded fields. Deep-plowing apparently increases DDT persistence by protecting it from decomposition and volatilization. Small amounts of DDT isomers continue to volatilize from the field with
unknown health implications for humans or animals exposed through the air. (J. Environ. Qual. 1996, 25, 815-21)
POLICY Environmental justice Minority groups organized in the early 1980s to oppose the siting of hazardous waste facilities in their neighborhoods spawned the environmental justice movement, an effort to remedy the inequitable distribution of environmental harm among communities. W. G. Hernandez reviews the history and substance of the movement and discusses legal responses to environmental justice concerns. He reports that existing environmental laws provide inadequate environmental justice protection to minority communities. Penalties under hazardous waste laws
5 1 8 A • VOL. 30, NO. 12, 1996 / ENVIRONMENTAL SCIENCE & TECHNOLOGY / NEWS
are up to 500% greater in white communities. Cleanup projects in minority communities begin up to 42% later than in white communities. Recent environmental justice remedies such as Executive Order 12898 are well intentioned but have little practical effect, because they lack permanence and enforceability. (UCLA Journal of Environmental Law and Policy 1996, 14{\), 181-208)
REMEDIATION Proton binding in sediments The transport and exchange of metals in natural waters depend mainly on the properties of natural particulates that enter and exit water by resuspension (due to wind and dredging) and settling of sediments. R Brassard and co-workers describe proton-binding titrations of sediments with a model based on simple diffusion. Results were compared with those for divinylbenzene macroporous spheres. Particle surface sites accounted for one-third to one-half the binding capacity with the rest resulting from polyelectrolyte sorption in the particle interior The authors report that proton (and metal) exchange by particles occurs by an initial fast exchange with surface sites followed by slower processes as the ions penetrate the particle Exchange bv laree particles mav become imDortant on lone sralps (.Environ Sr; Tprhnnl .999
Groundwater and catalysis Photocatalysis with titanium dioxide illuminated with ultraviolet light is an emerging treatment technology for organic pollutants in groundwater. It has advantages over traditional techniques that use adsorbents or stripping and produce byproducts that may require treatment. Yet its use has been hampered by fouling, loss of catalyst, and low efficiency. J. C. Crittenden cincl co-workers re-
0013-936X/96/0930-518A$12.00/0 © 1996 American Chemical Society
Microbial effects on aquifer denitrification Relative rates of microbial metabolism and physical flow influence the transport of many contaminants in groundwater. R. L Smith and coworkers studied the impact of microbes on the rate of denitrification in a nitrate-contaminated aquifer in situ. Acetylene tracer added to the aquifer was transported with the natural groundwater flow to ensure minimal perturbation of the natural physical environmental conditions. Denitrifying activity produced nitrous oxide. Rates measured in situ (0.61 51 nmol N 0 per cm3 aquifer day) were much lower than those for laboratory-based methods The authors conclude that the laboratory method's tendenrv to overestimate the rafp
