Vertical distribution and characteristics of soil humic substances affecting radionuclide distribution

The humic substances extracted from different soil depths are separated into humic (HA) and fulvic (FA) acids, and characterized for their chemical composition, proton exchange capacity, spectroscopic characteristics and binding properties to the europium ion. The chemical and spectroscopic results show that FA compared to HA has a relatively high O/C ratio, high acidic functional group contents and low aromatic contents. The synchronous fluorescence spectroscopic results show that the stability constant (K) of the soil humic substances with Eu(III) ion tends to increase as the soil depth becomes deeper, and HA has a slightly stronger binding ability than FA. The measured total site concentrations (C(L)) reveal that Eu(III) ion is loaded onto HA by 62-77% of the total acid sites, but FA is only approximately 50% covered by Eu(III) ion. Information could be useful in understanding the migration of radionuclides in soil layer.     

Global pollution monitoring of polychlorinated dibenzo-p-dioxins (PCDDs), furans (PCDFs) and coplanar polychlorinated biphenyls (coplanar PCBs) using skipjack tuna as bioindicator

In order to elucidate the global distribution of dioxins and related compounds, such as PCDDs, PCDFs and coplanar PCBs, levels of these compounds were determined in the muscle of skipjack tuna (Katsuwonus pelamis) collected from the offshore waters and open seas near Japan, Taiwan, Philippines, Indonesia, Seychelles and Brazil, and the Japan Sea, the East China Sea, the South China Sea, the Indian Ocean and the North Pacific Ocean. PCDDs, PCDFs and coplanar PCBs were detected in almost all the specimens collected from all the locations surveyed, indicating widespread contamination by these compounds in the marine environment. Higher concentrations of dioxins and coplanar PCBs were detected in the samples from temperate Asian regions, plausibly due to larger usage and anthropogenic generation in highly industrialized countries around the East China Sea and the South China Sea, such as Japan, Korea, Taiwan, Hong Kong and coastal China.     

Ecological modeling for water quality management of Kwangyang Bay, Korea

This study estimated the appropriate pollutant load reduction from point sources in Kwangyang Bay, Korea, using an eco-hydrodynamic model. The total chemical oxygen demand (COD), nitrogen (TN), and phosphorus (TP) loads from rivers and ditches that provide input to the bay were approximately 2.8x10(4), 2.5x10(4), and 5.9x10(2) kg day-1, respectively. Wastewater discharge from industrial complexes was the greatest contributor to pollutant loads in the inner part of the bay. COD values in the inner part of the bay were greater than 3.0 mg l-1, and exceeded Korean seawater quality grade III limits. A residual current was simulated, using a hydrodynamic model, to have a slightly complicated pattern in the inner part of the bay, ranging from 0.001 to 8 cm s-1. In the outer part of the bay, the simulated current flowed out to the South Sea with a southward flow at a maximum of 15 cm s-1. The results of the ecological model simulation of COD levels showed high concentrations, exceeding 4 mg l-1, in the southwest of the Myodo, an area of wastewater discharge, and lower levels, approaching less than 1 mg l-1, closer to the outer part of the bay. Engineering countermeasures to reduce the organic and inorganic material loads from point sources by more than 45% were required to keep the COD levels below 2 mg l-1.     

Identification of the source of nitrate contamination in ground water below an agricultural site, Jeungpyeong, Korea

This study applied hydrogeological characterization and isotope investigation to identify source locations and to trace a plume of ground water contaminated by nitrate. Most of the study site is agricultural fields with the remainder being residential. A poultry farm is also within the study area, so that potential point and nonpoint sources were present. Estimates of seasonal ground water recharge from irrigation and precipitation, leakage of sewage, and the regional ground water flow were linked to the seasonal changes in isotopic values. Ground water recharge largely occurred in spring and summer following precipitation or irrigation, depending on the locations. Natural and fertilized soils were identified as nonpoint sources of nitrate contamination in this area, while septic and animal wastes were identified as small point sources. The seasonal changes in the relative impact of these sources on ground water contamination were related to such factors as source distribution, the aquifer confining condition, precipitation rate, infiltration capacity, recharge rate, and the land use pattern.     

Industrial storm water pollution prevention: Effectiveness and limitations of source controls in the transportation industry

Industrial activities that are sources of pollutants in storm water runoff at typical facilities of the transportation industry are identified by site investigations at five facilities. This research then evaluates pollution prevention measures implemented to reduce those pollutants, as required by storm water regulations under the U.S. Clean Water Act. Activities that potentially generate storm water pollutants, particular to facilities of this industry, include: vehicle maintenance; vehicle fueling; vehicle washing; and activities on paved access roads and vehicle storage areas. Activities common to this industry, but also found in other industries, include: storage and handling of process materials and wastes; operation of industrial equipment located outdoors or exposed to storm water; and design and operation of site drainage facilities. Most control measures cited in the compliance documents of the facilities in the case studies were not developed specifically for storm water pollution prevention, but serve to reduce storm water pollutants as part of compliance with regulations for hazardous waste, wastewater, worker safety, or other purposes. Most identified control measures were operational practices or employee procedures, rather than structural facility modifications or devices to remove pollutants. Implementation of such measures is difficult to enforce or verify by regulatory agencies, and evidence at the case study facilities suggests that measures described similarly at different facilities are unevenly implemented and unequally effective at controlling storm water pollutants.     

Long-term operation of a biofilter for simultaneous removal of H2S and NH3

Simultaneous removal of NH3 and H2S was investigated using two types of biofilters--one packed with wood chips and the other with granular activated carbon (GAC). Experimental tests and measurements included analyses of removal efficiency (RE), metabolic products, and results of long-term operation (around 240 days). The REs for NH3 and H2S were 92 and 99.9%, respectively, before deactivation. After deactivation, the RE for NH3 and H2S were decreased to 30-50% and 75%, respectively. The activity of nitrifying bacteria was inhibited by high concentrations of H2S (over 200 ppm) but recovered gradually after H2S addition was ceased. However, the Thiobacillus thioparus as sulfur oxidizing bacteria did not show inhibition at the NH3 concentration under 150-ppm conditions. The deactivation of the biofilter was caused by metabolic products [elemental sulfur and (NH4)2SO4] accumulating on the packing materials during the extended operation. The removal capacities for NH3 and H2S were 6.0-8.0 and 45-75 mg N, S/L/hr, respectively.     

Effect of dissolved metal ions on PCE decomposition by gamma-rays

This study investigates the effect of initial tetrachloroethylene (PCE) concentration, irradiation dose and dissolved metal ions such as Cr3+, Mn2+, Fe3+, Co2+, Ni2+, Cu2+ and Zn2+ on removal of PCE by gamma irradiation. The amount of removed PCE decreased with increase in initial PCE concentration and increased with increase in irradiation dose. PCE removal reached a maximum in the presence of Fe3+, while Cu2+ strongly hindered PCE decomposition. Except for Cu2+, the amount of removed PCE in the presence of metal ions was linearly dependent on the standard reduction potential of the metal ions. The extraordinary inhibition of Cu2+ in PCE removal was caused by the action of Cu2+ as a strong *OH scavenger, that was directly confirmed by electron paramagnetic resonance spectroscopy.     

Effects of heavy rainfall on the composition of airborne bacterial communities

Wet deposition scavenges particles and particle-associated bacteria from the air column, but the impact of raindrops on various surfaces on Earth causes emission of surface-associated bacteria into the air column. Thus, after rainfall, these two mechanisms are expected to cause changes in airborne bacterial community composition (BCC). In this study, aerosol samples were collected at a suburban site in Seoul, Korea before and after three heavy rainfall events in April, May, and July 2011. BCC was investigated by pyrosequencing the 16S rRNA gene in aerosol samples. Interestingly, the relative abundance of non-spore forming Actinobacteria operational taxonomic units (OTUs) was always higher in post-rain aerosol samples. In particular, the absolute and relative abundances of airborne Propionibacteriaceae always increased after rainfall, whereas those of airborne Firmicutes, including Carnobacteriaceae and Clostridiales, consistently decreased. Marine bacterial sequences, which were temporally important in aerosol samples, also decreased after rainfall events. Further, increases in pathogen-like sequences were often observed in post-rain air samples. Rainfall events seemed to affect airborne BCCs by the combined action of the two mechanisms, with potentially adverse effects on human and plant health.

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A Comparison of Waste Reduction Practices and the New Environmental Paradigm in Four Southern Chinese Areas

On domestic waste recycling, it was found that source separation of domestic waste in mainland China was supported by 85% of the urban population and about 11–13% of the household waste was recovered and sold by the householders for financial gains. It was also found that the lower income group tended to recover a greater portion of waste, indicating that voluntary waste recovery activities in mainland China were carried out largely due to economic reasons. Thus, the Western type of source separation program in which residents are requested to separate recyclables for the community may not be welcomed in mainland China. In Hong Kong, despite the presence of community waste recovery programs, the recovery of domestic waste is only about 6% and is therefore less than those of the mainland Chinese cities surveyed. On the choice of source separation programs, it was found that Hong Kong people ranked familiarity a more important criterion than convenience. Therefore, the collection frequency of recyclables and time and place for setting out recyclables should be as similar to those of normal waste collection as possible to attract high participation in source separation programs.     

Effect of Fe-chelating complexes on a novel M2FC performance with ferric chloride and ferricyanide catholytes

As an effort to better utilize the microbial fuel cell (MFC) technology, we previously proposed an innovative MFC system named M2FC consisting of ferric-based MFC part and ferrous-based fuel cell (FC) part. In this reactor, ferric ion, the catholyte in the MFC part, was efficiently regenerated by the FC part with the generation of additional electricity. When both units were operated separately, the ferric-based MFC part produced approximately 1360 mW m⁻² of power density with FeCl₃ as catholyte and Fe-citrate as anolyte. The ferrous-based FC part with FeCl₃ as catholyte and Fe-EDTA as anolyte displayed the highest power density (1500 mW m⁻²), while that with ferricyanide as catholyte and Fe-noligand as anolyte had the lowest power density (380 mW m⁻²). The types of catholytes and chelating complexes as anolyte were found to play important roles in the reduction of ferric ions and oxidation of ferrous ion. Linear sweep voltammetry results supported that the cathode electrolytes were electrically active and these agreed well with the M2FC reactor performance. These results clearly showed that ligands played critical role in the efficiency and rate for recycling iron ion and thus the M2FC performance.