Impact of land-use types on nitrate concentration and δN in unconfined groundwater in rural areas of Korea

An understanding of the long-term changes in the nitrate contamination pattern of unconfined groundwater is critical to conservation of drinking water in rural areas supporting mixed land-use activities such as cropping, livestock farming, and residence. To examine the effect of different land-use activities on nitrate contamination, groundwater samples were collected monthly for 3 years (1997–1999) from 12 wells in rural areas with different land-use activities and analyzed for the concentrations and N isotopic ratios (δ¹⁵N) of nitrate. The characteristics of nitrate contamination clearly differed with land-use activities. The percentages of samples that had a nitrate concentration exceeding the national standard for drinking water (10 mg N L⁻¹) were 0, 23, 43, and 67% for the uncontaminated natural area, cropping area, cropping-livestock farming complex area, and residential area, respectively. The range of δ¹⁵N values was between +1.4 and +4.5‰ for groundwater nitrate from the uncontaminated natural area. In the cropping area, the δ¹⁵N values were slightly different with the type of fertilizer applied to fields in the vicinity of the well, and the values ranged between +8.7 and +14.4‰ for the compost-applied area and between +4.5 and +8.5‰ for the area where urea was applied with compost. The δ¹⁵N values of the cropping-livestock farming complex area ranged from +1.0 to +17.7‰, probably resulting from mixed contamination sources (inorganic fertilizer and livestock manure). The well located closest to the livestock feedlot had relatively higher δ¹⁵N values, with a range between +8.7 and +17.6‰. In the residential area, a higher δ¹⁵N (most frequently above +10‰) of nitrate suggested that the major source of contamination was effluent from leaky septic tanks. Our data showed that unconfined groundwater is susceptible to land-use activities above the aquifers, and the impacts of the activities could be more precisely inferred from long-term data on the concentration and δ¹⁵N of nitrate. By determining the impacts, more effective (specific to contamination sources) measures for preventing groundwater quality could be implemented.     

Modeling the effects of constructed wetland on nonpoint source pollution control and reservoir water quality improvement

This article describes the integrated modeling approach for planning the size and the operation of constructed wetlands for maximizing retention of nonpoint source pollutant loads and reservoir water-quality improvement at a catchment scale.The experimental field-scale wetland systems (four sets,0.88 ha each) have been in operation since 2002,where water depth was maintained at 30–50 cm and hydraulic loading rate was at 6.3–18.8 cm/day.The wetland system was found to be adequate for treating polluted stream water with stable removal efficiency even during the winter.The integrated modeling system (modified-BASINS) was applied to the Seokmoon estuarine reservoir watershed and calibrated with monitoring data from constructed wetland,stream,and reservoir.The calibrated integrated modeling system estimated that constructing wetlands on 0.5% (about 114 ha) of the watershed area at the mouth of reservoir could reduce 11.61% and 13.49% of total external nitrogen and phosphorus loads,respectively.It also might improve the nitrogen and phosphorus concentration of the reservoir by 9.69% and 16.48%,respectively.The study suggested that about 0.1%–1.0% of the watershed area should be allocated for constructed wetland to meet specified water-quality standards for the estuarine reservoir at the polder area where land use planning is relatively less complicated.     

Green synthesis, characterization and antimicrobial activity of silver nanoparticles using methanolic root extracts of Diospyros sylvatica

The current research study focuses to formulate the biosynthesized silver nanoparticles for the first time from silver acetate using methanolic root extracts of Diospyros sylvatica, a member of family Ebenaceae. TEM analysis revealed the average diameter of Ag NPs around 8 nm which is in good agreement with the average crystallite size (10 nm) calculated from X-ray Diffraction (XRD) analysis. Further the study has been extended to the antimicrobial activity against test pathogenic Gram (+) ve, Gram (−) ve bacterial and fungal strains. The bioinspired Ag-NP showed promising activity against all the tested bacterial strains and the activity was enhanced with increased dosage levels.     

Recovery of iron oxide and calcium chloride from an iron-rich chloride waste using calcium carbonate

Journal of Material Cycles and Waste Management - The ilmenite-chloride process has used for the production of TiCl4 from the ilmenite (FeTiO3) ore, which produces cyclone dust containing mostly...     

Analysis of gas flow behavior in an annular fluidized-bed reactor for polystyrene waste treatment

The characteristics of bubble properties and the chaotic flow behavior of gas were investigated in an annular fluidized bed (0.102 m in inner diameter and 2 m in height) because the behavior of gas flow in such a reactor is one of the important factors governing reactor operation, reactor performance, and the reaction itself. Pressure fluctuations as a state variable for the analysis of gas flow behavior were measured and analyzed. Bubble properties were determined by adopting the cross-correlation function of pressure fluctuations. The resultant chaotic flow behavior of gas was interpreted by means of chaotic parameters such as the Kolmogorov entropy. It was found that the Kolmogorov entropy could be utilized effectively to explain the nonlinear dynamic behavior of gas-solid flow in the annular fluidized bed. The pierced length and rising velocity of bubbles increased with increasing gas velocity, bed temperature, and particle size of the bed material. The bubble frequency increased with increasing gas velocity and bed temperature, while it decreased with increasing particle size of the bed material. Correlations to predict the bubble properties in annular fluidized-bed reactors were suggested.     

Enhancement of Tensile Strength and Flexibility of Polycaprolactone/Tapioca Starch Blends by Octadecylamine Modified Clay

Polycaprolactone/tapioca starch/octadecylamine modified clay (OMMT) nanocomposites were successfully prepared by melt blending. X-ray diffraction and transmission electron microscopy (TEM) of the products showed that they are nanocomposites of a mixture intercalated and exfoliated types. In addition, the TEM also revealed that the OMMT layers are homogeneously distributed in the polymer matrix. The presence of 1 php of OMMT improved the compatibility of the polymers in the blends which consequently increased the tensile strength of the blend of more than 60% and elongation at break of more than 1,000%.     

Improved enzymatic hydrolysis of waste paper by ozone pretreatment

Waste paper samples made from newsprint, copier paper, and magazine paper, as well as samples of kraft pulp and thermomechanical pulp, were pretreated with ozone to improve enzymatic hydrolysis. The ozone treatment of pulps of newsprint and of magazine paper increased the specific surface areas and total pore volumes while decreasing the lignin content so that these values became similar to those of thermomechanical pulps. These morphological and chemical changes in the pulps resulted in the increased access of cellulase to the pulp fiber surface and increased enzymatic hydrolysis. For copier paper, in which the lignin content was very low, additives on the pulp fiber surface were oxidized and removed by ozone treatment and extraction, and this allowed improved enzymatic hydrolysis. In contrast, surface areas and total pore volumes of kraft pulp and bleached kraft pulp were decreased by the ozone treatment, resulting in morphological changes in the pulps that decreased enzymatic hydrolysis.     

Assessment of airborne environmental bacteria and related factors in 25 underground railway stations in Seoul,Korea

This study assessed bacterial concentrations in indoor air at 25 underground railway stations in Seoul, Korea, and investigated various related factors including the presence of platform screen doors (PSD), depth of the station, year of construction, temperature, relative humidity, and number of passengers. A total of 72 aerosol samples were collected from all the stations. Concentrations of total airborne bacteria (TAB) ranged from not detected (ND) to 4997 CFU m^?3, with an overall geometric mean (GM) of 191 CFU m^?3. Airborne bacteria were detected at 23 stations (92%) and Gram-negative bacteria (GNB) were detected at two stations (8%). TAB concentrations of four stations (16%) exceeded 800 CFU m^?3, the Korea indoor bio-aerosol guideline. The results of the study showed that TAB concentrations at the stations without PSD showed higher TAB concentrations than those with PSD, though not at statistically significant levels. TAB concentrations of deeper stations revealed significantly higher levels than those of shallower stations. Based on this study, it is recommended that mitigation measures be applied to improve the indoor air quality (IAQ) of underground railway stations in Seoul, with focused attention on deeper stations.     

Photodegradation of the endocrine-disrupting chemical 4-nonylphenol in biosolids applied to soil

There is increasing concern about the environmental fate and impact of biosolids-associated anthropogenic organic chemicals, among which 4-nonylphenol (4-NP) is one of the most studied chemicals. This is primarily because 4-NP is an endocrine disruptor and has been frequently detected in environmental samples. Due to its high hydrophobicity, 4-NP has high affinity for biosolids. Land application of 4-NP-containing biosolids could potentially introduce large quantities of this chemical into the environment. A laboratory experiment was conducted to investigate the effect of artificial sunlight on 4-NP degradation in biosolids applied to soil. When exposed to artificial sunlight for 30 d, the top-5-mm layer of biosolids showed a 55% reduction of 4-NP, while less than 15% of the 4-NP was degraded when the biosolids were kept in the dark. Our results indicate that sensitized photolysis reaction plays an important role in reducing the levels of 4-NP in land-applied biosolids. Surface application rather than soil incorporation of biosolids could be effective in reducing biosolids-associated organic chemicals that can be degraded through photolysis reactions. However, the risks of animal ingestion, foliar deposition, and runoff should also be evaluated when biosolids are applied on the soil surface.