Jiyeon Park

Morphological and Elemental Classification of Freshly Emitted Soot Particles and Atmospheric Ultrafine Particles using the TEM/EDS

The Transmission Electron Microscopy (TEM) and Energy Dispersive Spectroscopy (EDS) were used to determine morphology and elemental composition of a variety of freshly emitted soot particles (acetylene flame, candle flame, kerosene flame, diesel exhaust, electric arc, plastic burning, styrofoam burning, wood burning [white oak and pine bark], and rice straw burning), which can be possible candidate soot in the ambient atmosphere, and ultrafine particles sampled in urban, industrial, and coastal sites during ultrafine particle formation events (combustion and photochemical events). By using mobility-classified non-refractory ((NH 4 ) 2 SO 4 ) and refractory (Polystyrene latex (PSL) and salt (NaCl)) particles, limitation of the TEM was tested. Data showed that the TEM method can be used to examine shapes of both volatile particles such as (NH 4 ) 2 SO 4 (100 nm) at low, but not high magnification (refer to low and high beam intensity, respectively), and non-volatile particles like NaCl (100 nm) and PSL (84 nm) at either low or high magnification. Distinct differences in morphological properties such as primary particle diameter, fractal dimension, and microstructure were observed among the different types of fresh soot particles. The atmospheric ultrafine particles were classified as agglomerates, sulfate mixtures (spherical), metallic oxides (spherical and polygonal), C-rich refractory (not agglomerated), C-rich non-refractory (not agglomerated), Si-rich (spherical), Na-rich (porous), or P-containing (non-spherical) particles. At the urban Gwangju site, a higher fraction of fresh and aged agglomerates was observed than at other sites. The C-rich non-refractory and sulfate mixtures were often observed in the photochemical event. The C-rich refractory particles were abundant at the Gwangju and Yeosu sites. The coastal Taean site had few agglomerates due to limited anthropogenic combustion source.

Size-resolved culturable airborne bacteria sampled in rice field, sanitary landfill, and waste incineration sites

Size-resolved bacterial concentrations in atmospheric aerosols sampled by using a six stage viable impactor at rice field, sanitary landfill, and waste incinerator sites were determined. Culture-based and Polymerase Chain Reaction (PCR) methods were used to identify the airborne bacteria. The culturable bacteria concentration in total suspended particles (TSP) was found to be the highest (848 Colony Forming Unit (CFU)/m(3)) at the sanitary landfill sampling site, while the rice field sampling site has the lowest (125 CFU/m(3)). The closed landfill would be the main source of the observed bacteria concentration at the sanitary landfill. The rice field sampling site was fully covered by rice grain with wetted conditions before harvest and had no significant contribution to the airborne bacteria concentration. This might occur because the dry conditions favor suspension of soil particles and this area had limited personnel and vehicle flow. The respirable fraction calculated by particles less than 3.3 mum was highest (26%) at the sanitary landfill sampling site followed by waste incinerator (19%) and rice field (10%), which showed a lower level of respiratory fraction compared to previous literature values. We identified 58 species in 23 genera of culturable bacteria, and the Microbacterium, Staphylococcus, and Micrococcus were the most abundant genera at the sanitary landfill, waste incinerator, and rice field sites, respectively. An antibiotic resistant test for the above bacteria (Micrococcus sp., Microbacterium sp., and Staphylococcus sp.) showed that the Staphylococcus sp. had the strongest resistance to both antibiotics (25.0% resistance for 32 microg ml(-1) of Chloramphenicol and 62.5% resistance for 4 microg ml(-1) of Gentamicin).

Phytoremediation of soil contaminated with heavy metals using Brassica napus

In order to examine the feasibility of utilizing oil extracted from plant seed in the contaminated areas, the phytoremediation applicability of soils contaminated with heavy metals and its follow-up result in the production of biodiesel was investigated. Brassica napus was chosen as the main target plant because it is widely used for phytoremediation and is an advantage of biodiesel production. From the perspective of heavy metal concentrations in Brassica napus, plants grown in contaminated soil show significantly higher concentration than those in non-contaminated soil. From the results of sequential extraction analysis, it was also found that heavy metal concentrations in plant may be increased with the enhancement of phyto-available fraction of heavy metal in the soil. These results show the feasibility of oil production extracted from Brassica napus, which was grown in heavy metal-contaminated soil. The seed contains a low concentration of most kinds of heavy metals except Zn in soil, which is essential for seed growth. The results of oil analysis show that more than 50% of heavy metal remained in the residues. Therefore, the application of phytoremediation by Brassica napus is a feasible technique for the removal of heavy metals and its following biodiesel production as an energy source is acceptable.

Natural attenuation of arsenic in the wetland system around abandoned mining area

Mechanisms of natural attenuation of arsenic (As) by wetland plants may be classified by plant uptake and adsorption and/or co-precipitation by iron (oxy)hydroxide formed on the root surface of plants or in rhizosediment. A natural Cattail (Typha spp.) wetland impacted by tailings containing high levels of As from the Myungbong abandoned Au Mine, South Korea was selected, and the practical capability of this wetland to attenuate As was evaluated. The As concentrations in the plant tissues from the study wetland were several-fold higher than those from control wetland. SEM-EDX analyses demonstrated that iron plaques exist on the rhizome surface. Moreover, relatively high As contents bonded with hydrous iron oxides were found in the rhizosediments rather than in the bulk sediments. It was revealed through the leaching and sequential extraction analyses that As existed as more stable forms in the wetland sediment compared with adjacent paddy soil, which is also contaminated with As due to input of mine tailings. The As concentration ratios of extracted solution to sediment/soil represented that the wetland sediment showed significant lower values (10-fold) rather than the paddy soil with indicating high As stability. Also, As in the wetland sediment was predominantly bonded with residual phases on the basis of results from sequential extraction analysis. From these results, it is concluded that transformation of As contaminated agricultural field to wetland environment may be helpful for natural attenuation until active remediation action.

Combination of transmission electron and atomic force microscopy techniques to determine volume equivalent diameter of submicrometer particles

Morphological properties of atmospheric particles are directly related to their residence time and transport behaviors, and their deposition patterns in human respiratory systems. The projected properties of particles measured by transmission electron microscopy (TEM) were combined with the particle height measured by atomic force microscopy (AFM) to determine volume equivalent diameter of submicrometer particles. For nonvolatile (refractory) laboratory‐generated spherical polystyrene latex and cubic NaCl particles, the measured volume equivalent diameters agreed well with the true values (within 4%). However, for nonrefractory (NH4)2SO4 particles, the measured volume equivalent diameter was much smaller than the true value due to evaporation of volatile species at low vacuum pressure and high electron‐beam intensity conditions in TEM, and deformation of particles in AFM. We observed that the volume equivalent diameter of 100 nm mobility‐classified atmospheric particles was 35 ± 5 nm, suggesting that these particles contain nonrefractory species, whereas that of 20 nm mobility‐classified atmospheric particles was found to be 19 ± 6 nm, suggesting that these particles were refractory and spherical. Microsc. Res. Tech., 2011.

Effect of phytoplankton biomass in seawater on chemical properties of sea spray aerosols.

This study is to investigate the effect of biological seawater properties on sea spray aerosols (SSA). Concentrations of chlorophyll-a and bacteria were measured at coastal site in Korea in fall and summer seasons. Also, aerosol mass spectrometer (AMS) was used to determine chemical constituents (organics, sulfate, nitrate, ammonium, and chloride) of non-refractory submicrometer aerosols sprayed from seawaters using a bubble bursting system. The average concentration of chlorophyll-a in seawater in fall was 1.75±0.78μg/l, whereas it significantly increased to 5.11±2.16μg/l in summer. It was found that the fraction of organics in the submicrometer SSA was higher in summer (68%) than fall (49%), and that the organic fraction in the SSA increased as the concentration of chlorophyll-a increased in seawater, suggesting that the high phytoplankton biomass in seawater could lead to the enhancement of organic species in the SSA.