Jae-Woo Park

Dissolved organic matter effects on the performance of a barrier to polycyclic aromatic hydrocarbon transport by groundwater.

In order to contain the movement of organic contaminants in groundwater, a subsurface sorption barrier consisting of sand or clay minerals coated with a cationic surfactant has been proposed. The effectiveness of such a sorption barrier might be affected by the presence of dissolved organic matter (DOM) in the groundwater. To study the impact of DOM on barrier performance, a series of batch experiments were performed by measuring naphthalene and phenanthrene sorption onto sand coated with cetylpyridinium chloride (CPC) and bentonite coated with hexadecyltrimethylammonium bromide (HDTMA) in the presence of various concentrations of DOM. The overall soil-water distribution coefficient (K*) of naphthalene and phenanthrene onto CPC-coated sand decreased with increasing DOM concentration, whereas the K* of the compounds onto HDTMA-coated bentonite slightly increased with increasing DOM concentration. To describe the overall distribution of polycyclic aromatic hydrocarbons (PAHs) in the systems, a competitive multiphase sorption (CMS) model was developed and compared with an overall mechanistic sorption (OMS) model. The modeling studies showed that while the OMS model did not explain the CPC-coated sand experimental results, a model that included competitive sorption between DOM and PAH did. The experimental results and the modeling study indicated that there was no apparent competition between DOM and PAH in the HDTMA-coated bentonite system, and indicated that in groundwater systems with high DOM, a barrier using HDTMA-coated bentonite might be more effective.

Environmental impact assessment using a GSR tool for a landfarming case in South Korea.

An environmental impact assessment of a landfarming process, which was performed at an actual petroleum-contaminated site, was conducted using a green and sustainable remediation (GSR) tool in this study. The landfarming process was divided into four stages: site preparation, installation, system operation, and system dismantling/waste disposal. The environmental footprints of greenhouse gas (GHG) emissions, water consumption, total energy usage, and air pollutants (SOx, NOx, and PM10) were analyzed. GHG emissions and water consumption were approximately 276xa0metric tons and 7.90Eu2009+u200905xa0gal, respectively, in stage III, where they were the highest due to the consumables and equipment use in the system operation. Total energy usage had the highest value of 1.54Eu2009+u200903xa0MMBTU in stage II due to material production. The SOx and NOx emissions primarily occurred in stages I and II due to energy usage. The PM10 was mostly emitted in stages I and III and was associated with heavy use of equipment. To reduce the environmental footprints, biodiesel and sunlight were suggested as alternatives in this study. The GHG and SOx emissions decreased to 1.7 and 4.4E-04xa0metric tons, respectively, on the basis of total emissions with a 1xa0% increase in biodiesel content, but the NOx emissions increased to 5.6E-03xa0metric tons. If sunlight was used instead of electricity, the GHG and NOx emissions could be reduced by as much as 79 and 84xa0%, respectively, and the SOx emissions could also be reduced.

A Study on the Synergistic Effects of Hybrid System Simultaneously Irradiating the UV and US

Both ultraviolet (UV) and ultrasound (US) systems are used in degrading of organic contaminants and they can thus be applicable simultaneously as an UV/US hybrid system in attempts further to increase the degradation efficiency. The pseudo-first order degradation rate constants with the UV, US and UV/US hybrid irradiation were 2.60, 10.34, and 14.81 × 10 min, respectively. It was observed that the synergistic effect of UV/US hybrid system for degrading the bis (2-ethylhexyl) phthalate (DEHP). The highest rate of DEHP degradation was found during UV/US hybrid irradiation and the synergistic effect factor (SEF) was calculated to be 1.15 based on the pseudo-first order degradation rate constants. Results indicate that synergistic effect of UV/US hybrid system is closely correlated to the enhancement of sonochemical reactivity with the UV-US interaction of increasing the formation rate of OH by providing additional H2O2 production through the pyrolysis of water molecules during UV/US hybrid irradiation.

A simplified sampling procedure for the estimation of methane emission in rice fields

Manual closed chamber methods are widely used for CH4 measurement from rice paddies. Despite diurnal and seasonal variations in CH4 emissions, fixed sampling times, usually during the day, are used. Here, we monitored CH4 emission from rice paddies for one complete rice-growing season. Daytime CH4 emission increased from 0800xa0h, and maximal emission was observed at 1200xa0h. Daily averaged CH4 flux increased during plant growth or fertilizer application and decreased upon drainage of plants. CH4 measurement results were linearly interpolated and matched with the daily averaged CH4 emission calculated from the measured results. The time when daily averaged emission and the interpolated CH4 curve coincided during the daytime was largely invariant within each of the five distinctive periods. One-hourly sampling during each of these five periods was utilized to estimate the emission during each period, and we found that five one-hourly samples during the season accurately reflected the CH4 emission calculated based on all 136 hourly samples. This new sampling scheme is simple and more efficient than current sampling practices. Previously reported sampling schemes yielded estimates 9 to 32% higher than the measured CH4 emission, while our suggested scheme yielded an estimate that was only 5% different from that based on all 136-h samples. The sampling scheme proposed in this study can be used in rice paddy fields in Korea and extended worldwide to countries that use similar farming practices. This sampling scheme will help in producing more accurate global methane budget from rice paddy fields.

Identifications of Optimal Conditions for Photo-Fenton Reaction in Water Treatment

Fenton is the reaction using the OH· radicals generating by interaction between hydrogen peroxide and Fe 2+ which can oxidize the contaminants. Fe 2+ ions are oxidized to Fe 3+ ions by reaction with H2O2 and formed OH· radicals. UV-Fenton process includes the additional reaction that generates the OH· radicals by photodegradation of H2O2. In methylorange (MO) decolourization experiment with UV-Fenton, optimal Fe 2+ :H 2O2 ratio was obtained at 1 : 10. Based on the obtained condition (H2O2 =1 0 mM, Fe 2+ = 1 mM) with/without UV-fenton experiment was carried out. Removal efficiency and sludge production were measured at 30 min. The case of w/o UV irradiation and only H2O2 was hardly treated and only Fe 2+ showed 65% removal owing to coagulation. When UV-Fenton process in optimal ratio (Fe 2+ :H 2O2 = 1 : 10), UV irradiation showed better removal efficiency than of w/o UV irradiation. Also, MO decolourization was a function of the hydrogen peroxide concentration (x1), Fe 2+ :H2O2 ratio (x2), and numbers of UV lamp (x3) from the application of the response surface methodology. Statistical results showed the order of significance of the independent variables to be hydrogen peroxide concentration > numbers of UV l amp > Fe 2+ :H 2O2 ratio.

Photoreduction of Carbon Dioxide using Graphene Oxide-Titanium Oxide Composite

In this study, we synthesized a combination of graphene oxide (GO) and titanium dioxide (TiO 2) and confirm that GO can be used for CO2 photoreduction. TiO2 exhibited highly efficient combination with other conventional electric charges generated by these paration phenomenon for suppression of hole-electron recombination. This improved the efficiency of CO2 photo - reduction. The synthetic form of GO-TiO 2 used in this study was agraphene sheet surrounded by TiO2 powder. Efficiency and stability were enhanced by combination of GO and TiO2. In a CO2 photoreduction experiment, the highest CO conversion rate was 0.652 μmol/g h in GO10-TiO 2 (2.3-fold that of pure TiO2) and the highest CH4 production rate was 0.037 μmol/g h in GO0.1-TiO 2 (2.4-fold that of pure TiO2). GO enhances photocatalytic efficiency by functioning as a support and absorbent, and enabling charge separation. With increasing GO concentration, the CH4 level decreases to~45% due to decreased transfer of electrons. In this study, TiO2 together with GO yielded a different result than the normal doping effect and selective CO2 photoreduction.

Effects of Pb, Cu, and Cr on Anaerobic Biodegradation of Diesel Compounds by Indigenous Bacteria

Anaerobic biodegradation of diesel with coexisting heavy metals (Pb) was monitored in batch mode. Two different groups of the indigenous bacteria from a site contaminated with diesel and lead were used in this research: the first group was composed of a single species and the second group was composed of several species. The effect of heavy metals on the microbial population was monitored and confirmed the biodegradation mechanism in each combined contaminant. Growth of the microorganisms in 21 days was observed Diesel > Diesel + Pb > Diesel + Cu > Diesel + Pb + Cu > Diesel + Cr > Diesel + Pb + Cr. Indigenous microorganisms showed the adaptation in the Pb contaminate. Interactive toxic effect using AMES test observed larger synergistic effect than antagonistic in Diesel + Cr and Diesel + Pb + Cr. Therefore, the main effects of diesel biodegradation in the present of heavy metals are likely to exist other factors as well as toxic of heavy metals. This is a necessary part of the future studies.

Kinetic Studies of Nanoscale Zero-Valent Iron and Geobacter lovleyi for Trichloroethylene Dechlorination

Nanoscale zero-valent iron (nZVI) has recently received much attention for remediation of soil and groundwater contaminated with trichloroethylene (TCE). But there have been many debates on the toxic or inhibitory effects of nZVI on the environment. The objective of this study was to investigate the effects of nZVI on the activity of Geobacter lovleyi and to determine the potent effect of combination of abiotic and biotic treatment of TCE dechlorination. TCE degradation efficiencies of Geobacter lovleyi along with nZVI were more increased than those when nZVI was solely used. The amount of total microbial protein was increased in the presence of nZVI and hydrogen evolved from nZVI was consumed as electron donor by Geobacter lovleyi. In addition, dechlorination of TCE to cis-DCE by Geobacter lovleyi along with nZVI in respiking of exogenous of TCE shows that the reactivity of Geobacter lovleyi was also maintained. These results suggest that the application of Geobacter lovleyi along with nZVI for the dehalorination is beneficial for the enhancement of TCE degradation rate and reactivity of Geobacter lovleyi.

Synthesis of Multi-Terminalized Magnetic-Cored Dendrimer for Adsorption of Chromium and Enhancement of Magnetic Recovery

A chrome absorbent that is useful in rapid magnetic recovery and recycling was developed though a synthesis of MultiTerminalized Magnetic-core Dendrimer (MTMD). Divergence through coprecipitation and rotation growth was used for synthesis. The dendrimer was multi-terminilized through methyl propionate and glutaric acid. The property analysis of the synthesized sample was performed through XRD, FT-IR, TEM, EDS, TGA and zeta potential analyzer. A magnetic-core of MTMD had a magnetite crystal and the size of 4th generation dendrimer was identified to be from 15 nm to 20 nm. Through the analysis of the TGA, the rate of the dendrimer branch for the first generation dendrimer was about 7% and 3% of diminished weight occurred as the generation grows. Also, the potential of the dendrimer when multi-terminalized, had variation from 25.26 mV to -6.53 mV. As a result of MTMD adsorption experiment, it absorbed more than 80% within 5 minutes and indicated absorptivity of 6.308 mg/g. When it was compared with COOH Dendrimer (COOH-D) after magnetic recovery, the recovery time was rapidly reduced by more than half and it could recover 100% within 30 minutes. In case of the regeneration experiment that used chrome, it was identified to maintain the same adsorptivity for four runs.