Interaction of plant secondary metabolites and organic carbon substrates affected on biodegradation of polychlorinated biphenyl.

Using plant secondary metabolites (PSM) as an inducer to stimulate biodegradation of polychlorinated biphenyl (PCB) is considered a promising strategy to remove PCB from the environment. In this study, the effects of PSM including naringin, salicylic acid or biphenyl on PCB biodegradation using soil isolates were tested in mineral salt medium using either soil organic carbon (MSMS) or glucose (MSMG). In addition, the effects of surfactant hydroxypropyl-beta-cyclodextrin (HP-beta-CD) were examined.

Effects of microbial iron reduction and oxidation on the immobilization and mobilization of copper in synthesized Fe(III) minerals and Fe-rich soils.

The effects of microbial iron reduction and oxidation on the immobilization and mobilization of copper were investigated in a high concentration of sulfate with synthesized Fe(III) minerals and red earth soils rich in amorphous Fe (hydr)oxides. Batch microcosm experiments showed that red earth soil inoculated with subsurface sediments had a faster Fe(III) bioreduction rate than pure amorphous Fe(III) minerals and resulted in quicker immobilization of Cu in the aqueous fraction. Coinciding with the decrease of aqueous Cu, SO4(2-) in the inoculated red earth soil decreased acutely after incubation.

Anaerobic digestion of municipal solid waste composed of food waste, wastepaper, and plastic in a single-stage system: performance and microbial community structure characterization.

The performance of municipal organic solid waste anaerobic digestion was investigated using a single-stage bioreactor, and the microbial community structures were characterized during the digestion. The results showed that the biogas and methane production rates were 592.4 and 370.

Biochars prepared from anaerobic digestion residue, palm bark, and eucalyptus for adsorption of cationic methylene blue dye: characterization, equilibrium, and kinetic studies.

Biochars prepared from anaerobic digestion residue (BC-R), palm bark (BC-PB) and eucalyptus (BC-E) were used as sorbents for removal of cationic methylene blue dye (MB). The FE-SEM images indicated that the biochars have a well-developed pore structure, and the Brunauer-Emmett-Teller surface areas of BC-R, BC-PB, and BC-E were 7.60, 2.

Prediction of aluminum, uranium, and co-contaminants precipitation and adsorption during titration of acidic sediments.

Batch and column recirculation titration tests were performed with contaminated acidic sediments. A generic geochemical model was developed combining precipitation, cation exchange, and surface complexation reactions to describe the observed pH and metal ion concentrations in experiments with or without the presence of CO2. Experimental results showed a slow pH increase due to strong buffering by Al hydrolysis and precipitation and CO2 uptake.

Innovative mathematical modeling in environmental remediation.

There are two different ways to model reactive transport: ad hoc and innovative reaction-based approaches. The former, such as the Kd simplification of adsorption, has been widely employed by practitioners, while the latter has been mainly used in scientific communities for elucidating mechanisms of biogeochemical transport processes. It is believed that innovative mechanistic-based models could serve as protocols for environmental remediation as well.

Modeling uranium transport in acidic contaminated groundwater with base addition.

This study investigates reactive transport modeling in a column of uranium(VI)-contaminated sediments with base additions in the circulating influent. The groundwater and sediment exhibit oxic conditions with low pH, high concentrations of NO(3)(-), SO(4)(2-), U and various metal cations. Preliminary batch experiments indicate that additions of strong base induce rapid immobilization of U for this material.

Dissolution of uranium-bearing minerals and mobilization of uranium by organic ligands in a biologically reduced sediment.

The stability and mobility of uranium (U) is a concern following its reductive precipitation or immobilization by techniques such as bioremediation at contaminated sites. In this study, the influences of complexing organic ligands such as citrate and ethylenediaminetetraacetate (EDTA) on the mobilization of U were investigated in both batch and column flow systems using a contaminated and bioreduced sediment. Results indicate that both reduced U(IV) and oxidized U(VI) in the sediment can be effectively mobilized with the addition of EDTA or citrate under anaerobic conditions.

Sequestering uranium and technetium through co-precipitation with aluminum in a contaminated acidic environment.

This research evaluated a method of controlled base addition for immobilizing uranium (U) and technetium (Tc) through coprecipitation with aluminum (Al) and other metal ions which coexist in a highly contaminated acidic environment. The batch and column experiments indicate that the addition of strong base (NaOH) provided a rapid yet effective means of sequestering U, Tc, and toxic metal ions such as nickel (Ni2+) and cobalt (Co2+) in the sediment and groundwater. Greater than 94% of soluble U (as UO2(2+)) and > 83% of Tc (as TcO4-) can be immobilized at pH above 4.

Dissolution and mobilization of uranium in a reduced sediment by natural humic substances under anaerobic conditions.

Biological reduction and precipitation of uranium (U) has been proposed as a remedial option for immobilizing uranium at contaminated sites, but the long-term stability and mobility of uranium remain a concern because the uranium is neither removed nor destroyed. In this study, the dissolution and mobilization of reduced and oxidized forms of uranium [U(IV) and U(VI)] by natural humic substances were investigated in batch and column-flow systems using a bioreduced sediment containing both U(IV) and U(VI). The addition of humic substances significantly increased the dissolution of U(IV) under anaerobic conditions.

Geochemical modeling of reactions and partitioning of trace metals and radionuclides during titration of contaminated acidic sediments.

Many geochemical reactions that control aqueous metal concentrations are directly affected by solution pH. However, changes in solution pH are strongly buffered by various aqueous phase and solid phase precipitation/dissolution and adsorption/desorption reactions. The ability to predict acid-base behavior of the soil-solution system is thus critical to predict metal transport under variable pH conditions.

Surface-enhanced Raman spectroscopy for uranium detection and analysis in environmental samples.

Techniques for rapid screening of uranium in environmental samples are needed, and this study entails the development of surface-enhanced Raman scattering (SERS) for analyzing uranium in aqueous media with improved sensitivity and reproducibility. A new SERS substrate based on (aminomethyl)phosphonic acid (APA)-modified gold nanoparticles was found to give greater than three orders of magnitude SERS enhancement compared with unmodified bare gold nanoparticles. Intensities of uranyl band at about 830 cm(-1) were proportional to the concentrations of uranium in solution, especially at relatively low concentrations (<10(-5) M).

In situ bioreduction of uranium (VI) to submicromolar levels and reoxidation by dissolved oxygen.

Groundwater within Area 3 of the U.S. Department of Energy (DOE) Environmental Remediation Sciences Program (ERSP) Field Research Center at Oak Ridge, TN (ORFRC) contains up to 135 microM uranium as U(VI).

Influence of bicarbonate, sulfate, and electron donors on biological reduction of uranium and microbial community composition.

A microcosm study was performed to investigate the effect of ethanol and acetate on uranium(VI) biological reduction and microbial community changes under various geochemical conditions. Each microcosm contained an uranium-contaminated sediment (up to 2.8 g U/kg) suspended in buffer with bicarbonate at concentrations of either 1 or 40 mM and sulfate at either 1.

Organic carbon effects on aerobic polychlorinated biphenyl removal and bacterial community composition in soils and sediments.

Certain organic compounds, including biphenyl and salicylic acid, stimulate polychlorinated biphenyl (PCB) degradation by microorganisms in some environments. However, the usefulness of these amendments for improving PCB removal by microorganisms from diverse habitats has not been extensively explored. This study evaluated the effects of biphenyl, salicylic acid, and glucose on changes in aerobic PCB removal and bacterial communities from an agricultural soil, a wetland peat soil, a river sediment, and a mixture of these samples.