Research Watch: SPME pesticide detection - Environmental Science


Research Watch: SPME pesticide detection - Environmental Science...

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RESEARCH WATCH

BIOREMEDIATION High concentrations Most microorganisms known to degrade halogenated benzenes, phenols, and benzoates in soil are gramnegative, such as Pseudomonas and Alcaligenes species, and require contaminants to be present at low concentrations. G. M. Zaitsev and colleagues evaluated the ability of a gram-positive organism, Rhodococcus opacus strain GM-14, to use 117 different aromatic and haloaromatic compounds as its sole sources of carbon energy. The organism grew on 48 of the 117 compounds tested at relatively high concentrations. This included growth in saturated solutions of benzene, chlorobenzene, and 1,3- and 1,4-dichlorobenzene. This ability and the widespread presence of this organism in soils may make it useful in soil bioremediation systems. [Appl. Environ. Microbiol. 1995, 61(12), 4191-201]

DRINKING WATER

Filtration shortfalls Recent outbreaks of disease in rural community residents who use groundwater as a potable water supply has prompted the use of point of-use, powdered activated carbon filters (PAC) to remove organic and microbial contamination. J. W. Snyder, Jr., and colleagues examined the effect of PAC filters on the bacteriological quality of groundwater in rural West Virginia. They evaluated 24 supplies for total coliform and heterotrophic plate count for 12 months. Results indicated that total coliform and heterotrophic plate count numbers were significantly reduced below the levels of untreated water flushed from the tap for at least 2 min. following overnight stagnation. The authors conclude that although PAC filters do not compromise the bacteriological quality of groundwater, they should

New model of alternative bioremediation methods C. Fu and co-workers developed and verified models that evaluated three alternative bioremediation techniques: soil slurry bioreactors, use of land farming and bioventing, and in-situ bioremediation. The authors derived biokinetic parameters using phenol in a bench-scale soil water slurry reactor. A bench-scale soil water experiment allowed them to determine the effects of contaminant diffusion in soil. Finally, soil compacted in a porous tube added the complexity of the oxygen diffusion rate, which controls biodegradation during bioremediation. In all cases, the models accurately predicted experimental data. (Environ. Sci. Techno!., this issue, 743-50)

not be used in lieu of required coliform testing and disinfection. [Appl. Environ. Microbiol. 1995, 61{12), 4291-95]

and consistent coagulation and flocculation scheme was primary in achieving a high, consistent degree of removal. (]• Am. Water Works Assn. 1995, 87, 83-89)

GROUNDWATER Surveying nitrates Ground electromagnetic conductivity surveys have been used to detect several contaminant plumes. D. J. Drommerhausen and colleagues used electromagnetic conductivity to detect soil pore nitrate beneath dairies, which they inferred were areas of high groundwater nitrate. Conductivity was measured on a grid, and contours were created and compared with groundwater nitrate concentrations. However, in using electromagnetic conductivity, the authors assumed homogeneity of site soil physical properties and that nitrate was the dominant anion in soil pore water. (J. Environ. Qual. 1995, 24, 1083-91)

Viral contaminations Resistance of protozoan parasites Cryptosporidium and Giardia to chemical disinfection poses a significant threat to public health and makes the removal of these microbial contaminants from municipal water supplies a challenging problem. J. E. Ongerth and J. P. Pecoraro applied direct filtration with multimedia filters to remove Giardia cysts and Cryptosporidium oocysts from water supplies. Low-turbidity feedwater was seeded with about 5000 cysts and 5000 oocysts. Various coagulation and flocculation regimens were applied, followed by direct, rapid-rate, gravity filtration through a multimedia filter consisting of anthracite, silica sand, and garnet. Results indicated that the amounts of both cysts and oocysts could be reduced by about three logs. The extent of removal was dependent on the quality of pretreatment. The authors conclude that a well-controlled

1 0 4 A • VOL. 30, NO. 3, 1996 / ENVIRONMENTAL SCIENCE & TECHNOLOGY / NEWS

MEASUREMENTS SPME pesticide detection Solid-phase micro extraction (SPME) is a relatively new technique for analyzing organic pollutants in aqueous samples, which involves a solventfree extraction and concentration of the pollutant. R. Eisert and K. Levsen developed an SPME gas chromatography/mass spectrometry-based, multiresidue method for the determining 49 nitrogen- and phosphorus-containing pesticides in aqueous samples. The method involves exposing an 85-pm polyacrylate fiber to an aqueous sample for 30 min to extract the pesticides. The pesticides are desorbed from the fiber in the heated injector of the GC/MS instrument. The results showed detection limits ranging between 5 and 90 ng/L with a coefficient of variation