Novel use of a dual-zone restricted access sorbent: normal-phase solid-phase extraction separation of methyl oleate from polynuclear aromatic hydrocarbons stemming from semi-permeable membrane devices.

A normal-phase solid-phase extraction (SPE) method was developed utilizing a dual-zone restricted-access sorbent to separate methyl oleate from the 16 US Environmental Protection Agency priority-pollutant polynuclear aromatic hydrocarbons in a hexane matrix. This technique represents a new development in SPE methodology expanding the limited number of available normal-phase SPE sorbents. While based on a specific application (removal of methyl oleate from semipermeable membrane device extracts), this cleanup method could easily be adapted for other uses requiring the removal/isolation of methyl oleate and potentially related compounds.

Selective and sensitive method for PCR amplification of Escherichia coli 16S rRNA genes in soil.

A set of PCR primers targeting 16S rRNA gene sequences was designed, and PCR parameters were optimized to develop a robust and reliable protocol for selective amplification of Escherichia coli 16S rRNA genes. The method was capable of discriminating E. coli from other enteric bacteria, including its closest relative, Shigella. Selective amplification of E. coli occurred only when the annealing temperature in the PCR was elevated to 72 degrees C, which is 10 degrees C higher than the optimum for the primers. Sensitivity was retained by modifying the length of steps in the PCR, by increasing the number of cycles, and most importantly by optimizing the MgCl(2) concentration. The PCR protocol developed can be completed in less then 2 h and, by using Southern hybridization, has a detection limit of ca. 10 genomic equivalents per reaction. The method was demonstrated to be effective for detecting E. coli DNA in heterogeneous DNA samples, such as those extracted from soil.

Effects of Soil Water Content and Soil Temperature on Efficacy of Metham-Sodium Against Verticillium dahliae.

Soil column studies were conducted to investigate the influence of soil water content and temperature on the efficacy of metham-sodium and its degradation product methyl isothiocyanate against Verticillium dahliae. The viability of the microsclerotia (MS) of the fungus in the top 30 cm of fumigated and control columns was measured. Temperatures for studies were 2 or 22°C, and the soil water content, expressed as soil matric potential, varied from -23 (wet), -113 (moist), to -2485 J/kg (dry). There was a significant interaction of soil water content and temperature on the efficacy of metham-sodium against V. dahliae MS. For the low soil temperature (2°C) the fumigant was more effective against MS of the fungus in wet than in moist or dry soil Soil water content did not affect fungicidal activity of metham-sodium when the soil columns were maintained at 22°C. These results suggest that the fumigant has a greater efficacy against V. dahliae in wet/cold soil conditions compared to the other conditions tested. Consequently, it was recommended that metham-sodium be applied to fields by chemigation in late fall or early spring to obtain efficacious results.

Assessment of chemical toxicity using mammalian mitochondrial electron transport particles.

New spectrophotometric bioassay procedures have been developed for evaluating chemical toxicity, using electron transport particles isolated from bovine heart mitochondria, based on the ability of many toxic chemicals to interfere with the integrated function of electron transport enzymes. The sensitivity of the mitochondrial assay is compared to published sensitivities of other in vivo and in vitro toxicity testing methods. Regression analysis of logarithmically transformed toxicity values for 42 chemicals, including 8 pesticides, 5 drugs, 6 metals, 8 alcohols, 5 respiratory inhibitors, 4 phenols, and 2 phthalates, indicates excellent correlation between the sensitivity of the new assays and the sensitivity of mammalian cytotoxicity studies (r2 = 0.86). Data from aquatic exposure toxicity tests conducted in fish are also highly correlated with the mitochondrial assay results (r2 = 0.79). However, correlation of data from these methods with median lethal dose studies conducted in rats is not as good because of the inability of in vitro and aquatic exposure analyses to account for the gastrointestinal absorption, hepatic metabolism, and excretion processes which modify toxic responses following oral administration.

A rapid bioassay for chemicals that induce pro-oxidant states.

A new bioassay has been developed that allows rapid, sensitive detection of chemicals such as paraquat and adriamycin, which manifest their acute toxicity, mutagenicity or carcinogenicity by inducing a pro-oxidant state in vivo. Submitochondrial particles isolated from bovine myocardium are used to catalyze NADH-dependent enzymatic reduction of these chemicals to free radicals. The highly reactive species generated in this system reduce molecular dioxygen to the superoxide anion radical, which is detected spectrophotometrically using the adrenochrome reaction. The anticancer drug adriamycin, the herbicides paraquat and diquat, the analytical dye sulfonazo III, and the experimental carcinogen 4-nitroquinoline-N-oxide have been used to test the sensitivity of this new method. This assay can be used to screen fresh water samples for the presence of pollutants that can generate oxygen-centered free radicals in vivo, or to test newly synthesized chemicals for this activity, and may therefore be valuable for environmental monitoring and preliminary toxicity evaluation of industrial or pharmaceutical products.

Environmental fate of alachlor and metolachlor.

Decision-makers, scientists, and the interested public should be informed what future research and education is needed if a strong pesticide regulatory program is imposed. Recommendations are intended to highlight research gaps. Some may be of general concern and apply to many pesticides. A situation that calls into question the value of many of our management decisions, is the lack of good field-scale experimentation and of logical mechanisms for translating and extrapolating laboratory data to field-scale dimensions. Many experiments were not designed to allow application of basic statistical criteria. High costs often preclude sufficient replication in field-scale experiments so that researchers must make the "no-win" choice between doing one investigation well or doing two or three poorly. The following observations about alachlor and metolachlor are provided: Pysicochemical properties are accurately determined. The herbicides' modes of action and plant selectivity have received a great deal of attention, but gaps remain in defining which of three modes of action are most important. Geographic distribution and extent of residue contamination of surface waters is documented, but groundwater contamination is poorly defined. Any groundwater monitoring protocol should limit the investigation based on sound scientific judgment since a nationwide monitoring network cannot be economically justified. Enough data are needed, however, to allow mathematical model development, verification and validation for a diversity of soil, geographic, climatic, and agricultural management conditions. In view of the importance of adsorption in determining the fate of pesticides, improved methods of determining adsorption coefficients (KD) are needed particularly for very low concentrations. The impact of soil aggregation on adsorption/desorption needs to be examined. The role of temperature and water content in adsorption/desorption processes needs clearer definition. Although volatilization is probably of limited concern for herbicides with Henry's Law constants less than 10(-5), better field-scale methods of estimating volatilization are needed. Lack of clear relationships between laboratory and field investigations is particularly acute in leaching studies. Differentiation between transport rates in the root and vadose zones are limited. Methods of sampling water in the vadose zone await innovative technology. Techniques to confine pesticides to the root zone or to retard their movement beyond the root zone are needed. Management strategies must protect groundwater by curtailing movement or reducing pesticide use. Losses of chloracetanilide herbicides through surface runoff and erosion is poorly documented. When erosion control was linked to soil productivity, use of small plot experiments was probably justified. If improved surface water quality is a goal, small plot findings must be extrapolatable to large watersheds.(ABSTRACT TRUNCATED AT 400 WORDS)

Degradation of methoxylated benzoic acids by a Nocardia from a lignin-rich environment: significance to lignin degradation and effect of chloro substituents.

Strain A81 of Nocardia corallina hydroxylates or demethylates p-anisic acid to p-hydroxybenzoic acid and isovanillic acid. It demethylates veratric acid to a mixture of vanillic and isovanillic acids. These are both demethylated to protocatechuic acid, which undergoes ring cleavage to afford beta-carboxy-cis-cis-muconic acid. The intermediacy of protocatechuic acid in the catabolic pathway of veratric acid was confirmed by blocking ring cleavage with an additional substituent in the ring: 5-chlorovanillic acid was demethylated to 5-chloro-protocatechuic acid, which accumulated. Chloro substituents in the ring of other methoxylated benzoic acids also arrested their normal metabolism by the Nocardia: an ortho-chloro substituent thwarted both demethylation and ring-opening. ortho-Hydroxylation of p-methoxybenzoic acid to isovanillic acid was unaffected by a chlorine ortho to the methoxyl group. Washed whole cells of veratric acid-grown N. corallina A81 produced no detected structural changes in an isolated lignin. The implications of this observation are discussed.

Lignification in trees: indication of exclusive peroxidase participation.

Syringaldazine did not turn purple on cross sections of tree branches or saplings or on cambial tissue cultures unless hydrogen peroxide was added; this indicated the absence of laccase but presence of peroxidase in lignifying cells. Peroxidase, therefore, apparently is the only en enzyme that polymerizes p-coumaryl alcohols to lignin in trees.

Bacterial cleavage of an arylglycerol- -aryl ether bond.

The first known cleavage by a bacterium of an arylglycerol-beta-aryl ether linkage, the most common intermonomer linkage in lignin, is described.