Nation's water quality reported much improved According to the Environmental Protection Agency's fifth National Water Quality Inventory, 73% of assessed river miles, 78% of assessed lake acres, and 82% of assessed estuarine and coastal waters can now support their designated uses, such as fishing and swimming, without harm to a person's or a fish's health. That represents a large improvement over water conditions in 1972 when the first water pollution control law was enacted. The word "assessed" is a slight hedge, since the waters represented in the inventory are only a small percentage of the nation's total waters. But because the states concentrate their monitoring efforts on waters most likely to be affected by pollution, EPA maintains that the remaining unassessed waters are most likely to be of equal or better quality.
The upbeat conclusion doesn't mean that all water quality problems have been solved. Thirty-seven states reported elevated levels of toxic pollutants in some of their waters, as evidenced by their elevated levels in fish tissue. Metals were the most frequently reported toxic pollutants, followed by pesticides and other organic chemicals. Thirtyfive states reported some problems with groundwater contamination by chlorinated solvents, pesticides, miscellaneous hydrocarbons such as gasoline, salts, and radionuclides. The most commonly reported sources of this contamination are industrial and municipal landfills or lagoons; u n d e r g r o u n d storage tanks; pesticide applications; septic tanks; and chemical and oil spills. Copies of the water quality inventory can be obtained by 'ailing (202) 382-7018. •
Unit measures surface magnetic microstructure Scientists at the National Bureau of Standards have developed an instrument that simultaneously measures the magnetic character of a surface and its physical structure, down to 10-nm dimensions. The device is expected to have important applications in many fields. John Unguris, Daniel T. Pierce, and Robert J. Celotta of NBS's Center for Radiation Research and Gary G. Hembree of its Center for Manufacturing Engineering have combined an ultrahigh-vacuum, high-
resolution scanning electron microscope (SEM) with a new, compact electron spin polarization detector developed at NBS. They call the resulting technique SEMPA, for scanning electron microscopy with polarization analysis. SEMPA is based on research results reported in 1982, in which the NBS scientists demonstrated that secondary electrons emitted by magnetic targets struck by an electron beam retain the spin polarization of the region of the surface from
NBS instrument gives high-resolution polarization image of magnetic domains in iron-3% silicon crystal surface (picture is 50 fim X 50 pm)
which they originate. The instrument measures the spin polarization of low-energy secondary electrons generated by incidence of the SEM's electron beam on ferromagnetic materials. It images directly the magnitude and orientation of the magnetic structure of materials with resolution far better than current instruments, at the same time giving a conventional topographic SEM image of the surface. Initial measurements were done on iron-3% silicon single crystals, producing about a 60% difference between light and dark domains (corresponding to areas of opposite magnetization). A key element is the compact electron spin polarization analyzer, based on the spin-dependent, lowenergy elastic scattering of electrons from an evaporated polycrystalline gold film. The analyzer is at least as efficient as conventional spin detectors (Mott scattering polarimeters), but is fist-sized and operates at about 150 volts. By contrast, Mott detectors require at least a cubic meter of space and operate at about 100,000 volts, requiring special highvoltage precautions. Potential applications of the new instrument include study of magnetic microstructure and its relationship to surface topographic and chemical features for magnetic storage and recording media, permanent magnet materials, and communications devices. Initial results will be described in the September issue of the Journal of Microscopy. U
U.S. closes loophole in tariffs on fuel ethanol The U.S. Customs Service, reversing its own year-old ruling, has closed a loophole in U.S. tariff regulations through which imported fuel ethanol has entered the country without being subjected to the normal 60 cent-per-gal duty on ethanol earmarked for fuel use. Under intense pressure from some influential Congressional leaders, Customs now says that blends of fuel-grade ethanol and certain hydrocarbons, such as methyl tert -butyl ether (MTBE) or aromatics (benzene, toluene, and xylene), no longer can August 12, 1985 C&EN
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