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.     

On East Asian Sand and Duststorms and Associated Significant Dustfall Observed from January to May 2001

Monitoring of dust pollution at the western shore of Tae-ahn Peninsula (TAP) and in the Chongju area of central Korea was carried out from January to May 2001. It was found that in Koreathere were 9 cases of sand and duststorms (DS) and 16 associatedsignificant dustfall (SD) days. Observed maximum concentrations of DS and SD coming from NW China and Mongolia were in the rangeof 300–920 for TSP, 200–690 for PM₁₀ and 100–170 g m^-3 for PM_2.5.Satellite measurements clearly showed the formation and subsequent movement of DS to the Korean Peninsula and onward to the Korea East Sea, Japan and the Gulf of Alaska. According to satellite image analysis of dust clouds there were abundant coarse particles, measuring in size of 11.0 m. Medium-sizedparticles measuring in the range of 3.5–7.0 were also prevalent,while fine particles of less than 2.0 m were less distinctive in reflectivity. Measured values of PM_2.5 were alsorelatively low with SD events.The measured average pH values of dusty precipitation associatedwith DS were 7.24. Alkaline precipitation can play a `temporary'role in the neutralization of acidified soil until the subsequentevent of acidic rain. The new selection criteria of SD days from PM_2.5 at 85 g m^-3, PM₁₀ 190 g m^-3 and TSP 250 g m^-3 are recommended on dust pollution occurring from the invasion of a DS elsewhere.     

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.     

Adsorption characteristics of Ni(II) on gamma-type alumina particles and its determination of overall adsorption rate by a differential bed reactor

The adsorption experiment of nickel ion [Ni(II)] on gamma-type alumina by a differential bed reactor in aqueous solutions was investigated to determine the adsorption characteristics and overall adsorption rate. The adsorbed amount increased rapidly with pH from pH 2 to 6 and kept constant over pH 6. The adsorbed amount of Ni(II) increased with temperature from 20 to 50 degrees C. Correlation coefficients (R2) of Langmuir and Freundlich adsorption isotherms were 0.9268 and 0.9489, respectively, and Freundlich isotherm was more suitable for adsorption on gamma-type alumina than Langmuir isotherm.The overall adsorption rate of Ni(II) on gamma-type alumina at pH 6 by a differential bed rector was determined as follows: r = 68.77Ce(1.61) - 17.60qe(0.36). Al(III) ions in solutions were away from the alumina surface during the adsorption of Ni(II) and Al(III) concentration increased with an increasing Ni(II) adsorbed amount on alumina.     

Climatology,Trend Analysis and Prediction of Sandstorms and their Associated Dustfall in China

Based on statistical data about Sand and Dust Storms (SDS) and their associated dustfall, features of temporal and spatialdistribution were studied first in this article. SDS and associateddustfalls occurred most often in northern China, especiallynorthwestern China. However, in the last two years, they have atendency to occur on the central and western parts of the Inner Mongolia Autonomous Region. As a result, Beijing is now among the impact areas, and the Chinese government is paying greaterattention to the matter. The changing trends of SDS and associated dustfalls were subsequently analyzed. Occurrences were seen to be decreasing with the feature of fluctuation duringthe period of 1954–2001, but they have slightly increased since 2000. Also, climate factors related to SDS and associated dustfalls were discussed. Finally, it was recommended that methods to predict SDS in China be further studied in the future.     

Modification of mutagenic activity of benzo[a]pyrene by trace elements in the Ames assay

Benzo[a]pyrene (BaP) is one of the most ubiquitous environmental contaminants and exerts potent carcinogenicity and mutagenicity. In the presence of rat liver S9 mix, four trace elements, germanium (Ge), iron (Fe), zinc (Zn), and molybdenium (Mo), were included in the Ames Salmonella microsome/mutagenic assay to test their inhibitory effects on BaP-induced mutations. All trace elements were found to exert an inhibitory effect in tester TA98 and TA100 strains; Fe was the most potent among the elements tested, whereas Zn was weakly inhibitory to prevent mutations. The present findings demonstrate that the antimutagenic potential of trace elements, notably Fe, may be attributed to its modulatory effect on the bioactivation and detoxification processes of BaP.     

Effects of ellagic acid on arylamine N‐acetyltransferase activity in human colon tumor cells

The inhibition of arylamine N‐acetyltransferase (NAT) activity by ellagic acid was determined in a human colon tumor (adenocarcinoma) cell line. Two assay systems were performed, one with cellular cytosols (9000g supernatant), the other with intact colon tumor cell suspensions. The NAT activity in a human colon tumor cell line was inhibited by ellagic acid in a dose‐dependent manner in both types of examined systems: i.e. the greater the concentration of ellagic acid in the reaction, the greater the inhibition of NAT activities in both systems. The data also indicated that ellagic acid decreased the apparent K _m and V _max of NAT enzymes from human colon tumor cells in both the systems examined. This report is the first demonstration which showed ellagic acid affect human colon tumor cell NAT activity.