A bioloigcal and chemical comparison of impacted subsurface sediments of the lower Mahoning River /

Abstract

Abstract-Microbial Activity To examine potential for bioremediation of industrially contaminated sediments in the Mahoning River of northeast Ohio, microbial activity measurements were made by estimating dehydrogenase activity using INT. Dehydrogenases take part in respiration and is fundamental to microbial activity. As !NT accepts electrons, it is reduced to a red colored formazan (INTF), which allows for rate ofreduction determination by colorimetric analysis. Attempts using previously published methods for this technique were unsuccessful due to background chemical reactions from high levels ofPAHs and metals in the sediments. Major modifications were necessary to circumvent these reactions. To find a solvent that did not chemically reduce INT, the following solvents were examined: acetonitrile, methanol, ethanol, N,N-dimethylformamide, dichloromethane, formaldehyde and ethyl acetate. Acetonitrile had the highest extraction efficiency and least chemical interference. Temperature trials were performed at 4,22, 40,60 and 95°C. The INT reduction was inhibited at 95°C indicative of biological activity. Various INT concentrations were also tested, with a 1.08 mM solution having the least variance and did not require dilution for analysis. Two and sixty minute incubations were performed. Two-minute incubations showed initial activity and rate, while sixty minutes gave overall activity. The method reported here yields a simple, quick, inexpensive, and precise estimation ofmicrobial activity.

Abstract- River Sediment Survey The Mahoning River, located in northeastern Ohio, has received direct industrial effluents for over eighty years that have accumulated in the sediments. This study compares the distribution of microbial activities, microbial biomass, toxicity and levels of polycyclic aromatic hydrocarbons (PAHs) in subsurface sediments. Microbial activities were measured via dehydrogenase reduction of iodonitrotetrazolium chloride to a formazan dye. Microbial biomass was determined by lipid phosphate extraction. Toxicity assays were performed using a modified basic solid phase test with MicrotoxOmni from Azur Environmental Inc. The PAHs were extracted using USEPA organic extraction method #3550 and quantified in a gas chromatograph/mass spectrometer as per USEPA method #8270. The results show microbial activities and microbial biomass higher in anthropogenically-contaminated sediments, which is indicative of potential for use of indigenous microbes for bioremediation.