Monitoring of soil biochemical quality parameters under greenhouse spinach cultivation through animal waste recycling

Under the intensive agricultural system, direct application of animal slurries to soils can provide a sustainable disposal of these wastes by inducing positive changes in soil quality and fertility. However, how animal wastes quantitatively affect the key nutrients (C, N, P and S) transforming soil enzymes is not clearly known. A greenhouse spinach cultivation study demonstrated that pig slurry, either in raw (RS) or processed (aerobically aged) (PS) form, significantly (p?β-glucosidase (23–39%), urease (59–103%), nitrate reductase (73–103%) and dehydrogenase (27–72%)) and microbial growth in soil as compared to the unamended control. However, it did not significantly (p?>?.05) alter the aryl sulphatase enzyme activity. Slurry applications also significantly improved the macro (N, P and K) and micronutrients (Cu, Mn, Zn and Fe) uptake by spinach plant and hence the yield (2.9–3.38 times higher than control). Similarly, compared to chemical fertilisers the application of pig slurries improved soil biological and biochemical parameters as well as plant nutrients uptake. This study demonstrated the closing of global energy and nutrient cycles through land application of animal wastes without compromising the crop yield.     

Inhibition of pyrite oxidation by surface coating: a long-term field study

Pyrite and other iron sulfides are readily oxidized by dissolved oxygen in aqueous phase, producing acidity and Fe²⁺, which causes significant environmental problems. Applications of surface coating agents (Na₂SiO₃ and KH₂PO₄) were conducted at Boeun (Chungbuk, South Korea) outcrop site, and their efficiencies to inhibit the oxidation of sulfide minerals were monitored for a long-term period (449 days). The rock sample showed positive Net Acid Production Potential (NAPP = 20.23) and low Net Acid Generation pH (NAGpH = 2.42) values, suggesting that the rock sample was categorized in the potential acid-forming group. For the monitored time period (449 days), field study results showed that the application of Na₂SiO₃ effectively inhibited the pyrite oxidation as compared to KH₂PO₄. Na₂SiO₃ as a surface coating agent maintained pH 5–6 and reduced oxidation of pyrite surface up to 99.95 and 97.70 % indicated by Fe²⁺ and SO₄ ^2? release, respectively. The scanning electron microscope and energy-dispersive X-ray spectrometer analysis indicated that the morphology of rock surface was completely changed attributable to formation of iron silicate coating. The experimental results suggested that the treatment with Na₂SiO₃ was highly effective and it might be applicable on field for inhibition of iron sulfide oxidation.     

Antibiotic resistance profile of bacterial isolates from animal farming aquatic environments and meats in a peri-urban community in Daejeon, Korea

The increasing usage of antibiotics in the animal farming industry is an emerging worldwide problem contributing to the development of antibiotic resistance. The purpose of this work was to investigate the prevalence and antibiotic resistance profile of bacterial isolates collected from animal farming aquatic environments and meats in a peri-urban community in Daejeon, Korea. In an antibacterial susceptibility test, the bacterial isolates showed a high incidence of resistance (～26.04%) to cefazolin, tetracycline, gentamycin, norfloxacin, erythromycin and vancomycin. The results from a test for multiple antibiotic resistance indicated that the isolates were displaying an approximately 5-fold increase in the incidence of multiple antibiotic resistance to combinations of two different antibiotics compared to combinations of three or more antibiotics. Most of the isolates showed multi-antibiotic resistance, and the resistance patterns were similar among the sampling groups. Sequencing data analysis of 16S rRNA showed that most of the resistant isolates appeared to be dominated by the classes Betaproteobacteria and Gammaproteobacteria, including the genera Delftia, Burkholderia, Escherichia, Enterobacter, Acinetobacter, Shigella and Pseudomonas.     

Blood lead levels of residents living around 350 abandoned metal mines in Korea

In 2007, as part of the control and prevention of environmental contamination threatening public health, the Korean Ministry of Environment planned to implement a national biomonitoring survey of three metals: lead, cadmium, and mercury in the blood of residents living near 350 abandoned metal mines known to be contaminated and as possible threats to the health of inhabitants. Thus, we investigated demographic and lifestyle variables and blood lead levels in residents living around the mines and compared them against those of control subjects. We measured the blood lead concentrations in 14,849 subjects (14,132 from nearby the 350 abandoned metal mines and 717 subjects from eight control areas). A questionnaire was provided to all subjects to determine gender, age, mining experience, period of time living in the vicinity of mines, smoking status, and personal perception of abandoned mines as a health risk. The geometric means (95% confidence intervals) of the blood lead levels of residents living around the abandoned metal mines and control areas were 3.017 (2.996-3.037 μg/dL) [female, 2.797 μg/dL (2.771-2.822 μg/dL); male, 3.330 μg/dL (3.298-3.363 μg/dL)] and 2.757 (2.677-2.837 μg/dL) [female, 2.604 μg/dL (2.506-2.700 μg/dL); male, 2.993 μg/dL (2.859-3.126 μg/dL)], respectively. Among residents of the mining areas, nonsmokers and residents who had no mining experience showed significantly lower mean blood lead levels than did smokers, past smokers, and those with mining experience. The mean blood lead concentrations of residents who expressed some concern about the abandoned mines were significantly higher than those of residents without concerns. The mean blood lead concentration of residents living around the abandoned mines was significantly higher than that of residents living in control areas as well as that of the general adult Korean population. We also confirmed that smoking is an important variable to consider, as it increases blood lead concentration.     

Performance of an electrochemical COD (chemical oxygen demand) sensor with an electrode-surface grinding unit

An electrochemical COD (chemical oxygen demand) sensor using an electrode-surface grinding unit was investigated. The electrolyzing (oxidizing) action of copper on an organic species was used as the basis of the COD measuring sensor. Using a simple three-electrode cell and a surface grinding unit, the organic species is activated by the catalytic action of copper and oxidized at a working electrode, poised at a positive potential. When synthetic wastewater was fed into the system, the measured Coulombic yields were found to be dependent on the COD of the synthetic wastewater. A linear correlation between the Coulombic yields and the COD of the synthetic wastewater was established (10-1000 mg L(-1)) when the electrode-surface grinding procedure was activated briefly at 8 h intervals. When various kinds of wastewater samples obtained from various sewage treatment plants were measured, linear correlations (r(2)> or = 0.92) between the measured EOD (electrochemical oxygen demand) value and COD of the samples were observed. At a practical wastewater treatment plant, the measurement system was successfully operated with high accuracy and good stability over 3 months. These experimental results show that the application of the measurement system would be a rapid and practical method for the determination of COD in water industries.     

Effect of arsenic species on the growth and arsenic accumulation in Cucumis sativus

The effects of arsenic (As) species, such as As(III), As(V) and dimethylarsinic acid (DMA), on the accumulation of As in cucumber (Cucumis sativus), as well as on its growth in a soil mesocosm were evaluated. When Cucumis sativus was cultivated in soils contaminated with 20 and 50 mg/kg of As(III), As(V) or DMA for 40 days, the growth was markedly inhibited by the inorganic As (As(III) and As(V)) rather than the organic As (DMA). Irrespective of the As species, the As concentrations accumulated in Cucumis sativus increased with increasing As concentration in the soil. The As bioaccumulation factors from soil into the tissue of Cucumis sativus were 17.5-35.4, 29.3-42.7 and 17.6-25.7 for As(III), As(V) and DMA, respectively. In addition, the As translocation factors from the roots to shoots were 0.025-0.031, 0.018-0.032 and 0.014-0.026 for As(III), As(V) and DMA, respectively. In conclusion, Cucumis sativus mainly accumulated As in its roots rather than its shoots and easily accumulated inorganic rather than organic As from the soil into its tissue.     

Effect of arsenic species on the growth and arsenic accumulation in <Emphasis Type="Italic">Cucumis sativus</Emphasis>

The effects of arsenic (As) species, such as As(III), As(V) and dimethylarsinic acid (DMA), on the accumulation of As in cucumber (Cucumis sativus), as well as on its growth in a soil mesocosm were evaluated. When Cucumis sativus was cultivated in soils contaminated with 20 and 50 mg/kg of As(III), As(V) or DMA for 40 days, the growth was markedly inhibited by the inorganic As (As(III) and As(V)) rather than the organic As (DMA). Irrespective of the As species, the As concentrations accumulated in Cucumis sativus increased with increasing As concentration in the soil. The As bioaccumulation factors from soil into the tissue of Cucumis sativus were 17.5–35.4, 29.3–42.7 and 17.6–25.7 for As(III), As(V) and DMA, respectively. In addition, the As translocation factors from the roots to shoots were 0.025–0.031, 0.018–0.032 and 0.014–0.026 for As(III), As(V) and DMA, respectively. In conclusion, Cucumis sativus mainly accumulated As in its roots rather than its shoots and easily accumulated inorganic rather than organic As from the soil into its tissue.     

Distributions of heavy metals in the sediments of South Korean harbors

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.     

Mercury flows in a zinc smelting facility in South Korea

To prepare for the international mercury convention, the characteristics of mercury emissions from a zinc smelting facility in South Korea have been reviewed and a material flow analysis (MFA) has been conducted in this research. As inputs into the mercury MFA study, zinc ores and sulfuric acid were examined, whereas wastewater sludge, effluence water, spent catalyst, and emissions from the casting and roasting processes were examined as outputs. Mercury concentrations extracted from end products like zinc ingots, cadmium ingots, and sulfuric acid were then analyzed. Our results showed that the wastewater sludge discharged from the zinc smelting process had a relatively higher concentration of mercury, indicating that the concentration of mercury was further enriched in the wastewater sludge. The wastes discharged through the zinc smelting process should be thoroughly controlled, as results of the MFA showed that approximately 89 % of the mercury contained in the original input was later found in the waste. According to this study, the higher the concentration of mercury within zinc ores at the input stage, the higher is the mercury concentration found in the wastewater sludge at the output stage.     

Numerical study of heat transfer characteristics of char from waste tire pyrolysis

To investigate heat transfer of char from waste tire pyrolysis, the cooling of char was simulated by the computational fluid dynamics. To scrutinize the heat transfer characteristics, bed height, temperature of cooling wall, and mixing time were selected as calculation parameters. From the results, increasing the char bed height from 0.005 to 0.02 m, the total heat transfer is decreased as from 45.5 to 26.5 J. As the char bed height is further increased from 0.02 to 0.06 m, the total heat transfer is decreased from 26.5 to 9.1 J. The char bed height affects the total heat transfer significantly. The total heat transfer decreases from 15.9 to 14.0 J as the temperature of cooling wall increases from 273.15 to 323.15 K. The total heat transfer mildly depends on the temperature of cooling wall. The particle mixing time increases from 10 to 120 s and the total heat transfer decreases from 28.6 to 22.6 J. It is noted that the particle contact is enhanced between char particles as well as the particles and cooling wall as the particle mixing time decreases. Consequently, heat transfer is augmented.