A novel immunoassay monitor Inexpensive monitoring devices are needed to confirm compliance with EPA-mandated heavy-metal contaminant loading reductions in aqueous waters. M. Khosraviani and colleagues developed a novel selective immunoassay for cadmium. The rapid assay is based on a monoclonal antibody that recognizes Cd2*-EDTA complexes but not free EDTA and can detect Cd2* at concentrations ranging from 7 to 500 ppb. The assay is not affected by interference from commonly encountered cations such as Ca2* Na* and K*. Other metals likely to be present in natural waters including Fe3\ Pb2t Zn2* Ni2\ In3* Mn2* and Mg2\ do not create Cd2* measurement problems at relevant contaminant concentrations However Hg2* can giv/P a false nn^itiup response at concentrations greate r
than 1 pM {Environ Sci Technol this
A. T. Yeung and colleagues evaluated the potential use of electrophoresis of clay particles for plugging liner leaks without prior removal of impoundment contents. They found that an imposed direct-current electric field caused clay particles to migrate toward leaks and form a seal. Effects of clay type, particle concentration in suspension, leak size, and electric-field strength on leak closure success were evaluated. The feasibility for use and limitations of the method at full scale are discussed. The authors suggest that even if sealing efficiency in field applications is the method could still be used in an economical for locating leaks in subsurface liners (J Environ Eng.NY) )997 723(10] 993-1001)
MEASUREMENTS
difficult to perform. D. Chambers and co-workers developed an ionstore, time-of-flight mass spectrometer that preconcentrates samples and is designed for real-time monitoring of trace-level changes of VOCs and semivolatile compound concentrations in large-volume air samples. Favorable measurements of trace concentrations of several aromatic and chlorinated compounds were performed. The system has analytical detection limits typically in the low parts-per-billion volume range and a 2000-m/Am mass resolution. Results are shown for analysis of several trace aromatic and chlorinated compounds and demonstrate typical system pabilities (Anal Chem 1997 69(18) 3780-90)
Groundwater metals probe Rapid screening methods are needed for heavy metals in groundwater. A proof-of-concept field evaluation made it possible for J. Herdan and co-workers to evaluate the performance of an electrochemical probe for in situ detection of copper, cadmium, lead, and zinc in groundwater. The novel probe, consisting of a micrographically fabricated iridium ultramicroelectrode array sensor, a custom-built miniaturized potentiostat, and a microcontroller, detected the metal contaminants at part-per-billion levels in a proof-ofconcept field demonstration at a metals-contaminated landfill site The authors concluded that the method is aooropriate for initial rapid fieldbaspri scrppning of rnntaminated sitPQ fnllprtpH data agreeri uuithin an order of magnititHo uwith thnco
SEDIMENT
obtainort K\y other conwontional anal (En\/imn
EDTA metal solubilization When present as a contaminant, ethylenediaminetetraacetic acid (EDTA) may solubilize metals in river sediments. S. J. Gonsior and colleagues developed a statistically significant, no-observed-effect-level (NOEL) standard for EDTA solubilization of nickel, cobalt, copper, zinc, cadmium, iron, and lead in simulated river-sediment microcosms. If EDTA concentration is below the corresponding NOEL standard for each metal observable metal solubilization does not occur. Concentrations of EDTA present as a contaminant in actual river-sediment samples were found to be below NOEL levels leading the authors to conclude that metal solubilization by EDTA complexation was unlikelv to be significant in tested river waters The method can be aDDlied to other water systems (J Environ Qual 1997 26 957-66)
WASTEWATER
VOC detection method
Sludge denitrification
The Clean Air Act requires detection of VOCs, often in trace amounts in complex sample matrices. Real-time measurement of trace-level chemical species concentrations in these environments has been particularly
Nitrate ion, often found in industrial wastewater discharges, is a soluble and easily transportable primary drinking water contaminant that must be removed. Activated sludge removes nitrate, but denitrification
Qri Tpph-
nnl this ksiip pp 131-?fil
can be inhibited by formation of nitrite ion, a reaction intermediate. In laboratory-scale experiments, C. Glass and co-workers evaluated the influence of initial nitrite concentration, pH, and suspended solids on the sludge denitrification process. Results indicate that extensive denitrification with little inhibition occurs at pH levels of 8 or higher, but the process is inhibited at lower pH levels, even when nitrite concentrations are low. Suspended solids in industrial wastewater discharges did not appear to affect nitrite inhibition of denitrification for conditions studied (Water Environ Res 1997 69(6) 1086-93) Contributors: Michael Brauer, University of British Columbia, Vancouver; Brian Eitzer, Connecticut Agricultural Experiment Station, New Haven, Conn.; Stephen Geiger, Remediation Technologies, Inc.. King of Prussia, Pa.; Vincent Hand, Miami University, Institute of Environmental Sciences, Oxford, Ohio; Louis Kovach, Ecolife Associates, Wilmington, Del.; Geoffrey Nobes, McGill University, Montreal, Canada; Raeuryn Town, Queen's University yo Belfast, Northern Ireland; and Margaret Whittaker, NSF International, Ann Arbor, Mich.
JAN. 1, 1998/ENVIRONMENTAL SCIENCE & TECHNOLOGY / NEWS • 49 A
