F. Michael Saunders

Genetic Identification of a Putative Vinyl Chloride Reductase in Dehalococcoides sp. Strain BAV1

ABSTRACT Dehalococcoides sp. strain BAV1 couples growth with the reductive dechlorination of vinyl chloride (VC) to ethene. Degenerate primers targeting conserved regions in reductive dehalogenase (RDase) genes were designed and used to PCR amplify putative RDase genes from strain BAV1. Seven unique RDase gene fragments were identified. Transcription analysis of VC-grown BAV1 cultures suggested that bvcA was involved in VC reductive dechlorination, and the complete sequence of bvcA was obtained. bvcA was absent in Dehalococcoides isolates that failed to respire VC, yet was detected in four of eight VC-respiring mixed cultures.

Assessment of plant-driven removal of emerging organic pollutants by duckweed

Constructed treatment wetlands have the potential to reclaim wastewaters through removal of trace concentrations of emerging organic pollutants, including pharmaceuticals, personal care products, and pesticides. Flask-scale assessments incorporating active and inactivated duckweed were used to screen for plant-associated removal of emerging organic pollutants in aquatic plant systems. Removals of four of eight pollutants, specifically atrazine, meta-N,N-diethyl toluamide (DEET), picloram, and clofibric acid, were negligible in all experimental systems, while duckweed actively increased aqueous depletion of fluoxetine, ibuprofen, 2,4-dichlorophenoxyacetic acid, and triclosan. Active plant processes affecting depletion of experimental pollutants included enhancement of microbial degradation of ibuprofen, uptake of fluoxetine, and uptake of degradation products of triclosan and 2,4-dichlorophenoxyacetic acid. Passive plant processes, particularly sorption, also contributed to aqueous depletion of fluoxetine and triclosan. Overall, studies demonstrated that aquatic plants contribute directly and indirectly to the aqueous depletion of emerging organic pollutants in wetland systems through both active and passive processes.

The effect of solute competition on ozonolysis of industrial dyes

Abstract Ozonation of three industrial dyes was examined in batch studies with single- and multi-solute dye solutions. The kinetics of dye oxidation were controlled by gas transfer limitations and oxidation took place at the gas-liquid interface. Competition by dye molecules for the gas-liquid interface and relative chemical reactivity resulted in the preferential oxidation of selected dyes in mixtures of three dyes and auxilliary compounds typically found in dye-bath wastewaters.

Glycosidation of chlorophenols by Lemna minor.

Metabolic fate of xenobiotics in plant tissues has an important role in the ultimate fate of these compounds in natural and engineered systems. Chlorophenols are an important class of xenobiotics used in a variety of biocides and have been shown to be resistant to microbial degradation. Three chlorophenyl glycosides were extracted from tissues of Lemna minor exposed to 2,4-dichlorophenol (DCP). The products were identified as 2,4-dichlorophenyl-beta-D-glucopyranoside (DCPG), 2,4-dichlorophenyl-beta-D-(6-O-malonyl)-glucopyranoside (DCPMG) and 2,4-dichlorophenyl-beta-D-glucopyranosyl-(6 --> 1)-beta-D-apiofuranoside (DCPAG). Identification was based on reverse phase retention (C18), electrospray mass spectra collected in negative and positive mode (ESI-NEG and ESI-POS, respectively), and nuclear magnetic resonance (NMR) spectra comparisons to reference materials synthesized in the laboratory. Liquid chromatography-mass spectrometry (LC-MS) analysis of plants exposed to 2,4,5-trichlorophenol (TCP) formed analogous compounds: 2,4,5-trichlorophenyl-beta-D-glucopyranoside (TCPG), 2,4,5-trichlorophenyl-beta-D-(6-O-malonyl)-glucopyranoside (TCPMG) and 2,4,5-trichlorophenyl-beta-D-glucopyranosyl-(6 --> 1)-beta-D-apiofuranoside (TCPAG). Enzyme catalyzed hydrolysis with beta-glucosidase was ineffective in releasing the beta-glucosides with chemical modifications at C6. Presence of these glucoconjugates confirmed that L. minor was capable of xenobiotic uptake and transformation. Identification of these products suggested that chlorophenols were incorporated into vacuoles and cell walls of L. minor.

Multistage Decomposition Kinetics of Ozone In Dilute Aqueous Solutions

Abstract AbstractDecomposition of ozone in dilute aqueous solutions was found to be a complex process kinetically. Initial ozone dose-time had a significant impact on reaction order. Solutions dosed initially for less than one minute displayed uniform second-order kinetics. For doses applied over 5 and 15 min periods at a pH -2, reaction order changed from 2 to 1 to 0 as ozone decomposition progressed. At a pH of 6.65, the transition was from a reaction order of 2.5-3 to 2. This behavior has been ascribed to the effect of accumulated ozone decomposition products on the decomposition process.

Development and application of oxygen production rate assessment to uptake of fluorinated organics by Lemna minor.

The effects of contaminant concentration on contaminant removal by Lemna minor were examined under elevated plant densities typical of full surface coverage. Uptake of 3-fluorophenol and 3-trifluoromethylphenol by L. minor was determined at concentrations from 10 to 1750 microM. Because standardized toxicity tests typically do not measure plant activity of L. minor at high plant densities, an oxygen production rate (OP) assessment was developed with consideration of experimental parameters that may inhibit OP by L. minor, including concentrations of carbonate and phosphate buffer in the media, time of assessment, and mass of L. minor. The OP by L. minor was inhibited by increasing media pH and mass of L. minor. The developed assessment used 0.5 g of L. minor per 60 ml of modified Standard Methods medium. A total of 30 h was needed to determine toxicity of fluorinated phenols, with an exposure period of 24 h, an incubation time of 6 h, and negligible analysis time. At concentrations from 10 to 1750 microM, 3-trifluoromethylphenol exhibited a sigmoidal toxicity response. However, 3-fluorophenol was neither toxic nor inhibitory at the experimental concentrations tested. Substantial decreases in uptake rate constants were observed for increasing concentrations of both contaminants, indicating that concentration may be a more important indicator of uptake by L. minor compared with decreasing plant activity because of toxicity.

Phytoremediation of fluorinated pollutants by duckweed

In natural and engineered systems, aquatic plants actively remediate agricultural wastes and pollutants. Characterization of pollutant removal by aquatic plants is essential for improved design of phytoremediation systems for polluted surface waters. To measure removal of fluorinated pollutants by duckweed, duckweed was exposed to fluorinated pollutants in batch reactors. Aqueous pollutant concentration was regularly sampled and analyzed (HPLC/DAD/MS). After a 50-hr exposure, duckweed activity was quantified using oxygen production assessment to determine whether duckweed was inhibited. Removal of fluorinated pollutants by duckweed was rapid, with pseudo-first-order uptake rates of 0.21 – 0.85 d-1 for fluoro- and trifluoromethyl- phenols. Uptake rates of fluorinated pollutants were pollutant-specific and appeared to depend on factors affecting rates of enzymatic processing. However, attempts to correlate removal rates with chemical parameters were unsuccessful. The positioning and type of fluoro- substituents on the phenol ring was the most indicative parameter of uptake rates. TFM, a lampricide used in the Great Lakes, was the only fluorinated pollutant that was not uptaken by duckweed. Negligible uptake of TFM by duckweed was not attributed to presence of the nitro- or trifluoromethyl- groups, as 2,4,6- trinitrotoluene and 3-trifluoromethylphenol were actively uptaken. Although uptake rates were not easily predicted by known chemical parameters, uptake rates indicated that duckweed plays an important role in phytoremediation of fluorinated pollutants in surface waters.

Callus Cultures for Phytometabolism Studies: Phytometabolites of 3-Trifluoromethylphenol in Lemnaceae Plants and Callus Cultures

Plant callus cultures have the potential to advance phytoremediation science by allowing study of cellular phytometabolism in absence of sorption, translocation, microbial degradation, and other phytoremediation processes; however, studies demonstrating the applicability of results from callus cultures to whole plants are limited. The aim of this study was to evaluate the feasability and applicability of using callus cultures to study phytometabolism. This aim was accomplished through evaluation of induction and growth of Lemnaceae callus cultures and comparison of phytometabolism in callus cultures and whole plants. Four out of eight published methods for callus culture of Lemnaceae successfully induced callus cultures that exhibited doubling times of 1.7 to 23 wks. Callus cultures and whole plants of Landoltia punctata and Lemna minor metabolized 3-trifluoromethylphenol (3-TFMP) through conjugation with glucopyranoside, malonyl-glucopyranoside, and glucopyranosyl-apiofuranoside. However, concentrations of metabolites were approximately 10 times less in callus cultures than in plants. While results demonstrated applicability of callus cultures results to whole plants, the low success rate of callus induction procedures, length of time required to produce substantial callus mass, and the low accumulation of metabolites in callus cultures may limit the feasibility of callus cultures for assessing phytometabolism.

Heavy metal impact on disposal and reclamation of aluminum‐anodizing residues

Abstract Finishing architectural aluminum using caustic etching and sulfuric‐acid anodizing produces voluminous, aluminum‐hydroxide residues for disposal. Implementation of etch recovery systems can reduce total residue volume. Acidic reclamation of conventional and etch‐recovery residues to produce liquid alum can eliminate residue disposal problems. The heavy metal contents of aluminum‐anodizing residues are low and in general meet regulations for metals in potable waters. Concentrations of copper, nickel, tin and zinc should be further monitored or controlled within an anodizing plant, if liquid alum is to be produced.