• Animal cells and systems
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• v.7 no.4
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• pp.289-294
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• 2003

To quantify nutrient loading from emergent macrophytes through leaching in the littoral zones of Paldang Reservoir, we conducted incubation experiments using leaf litter of the emergent macrophyte, Zizaniz latifolia. To separate the leaching process from microbial decay, we used $HgCl_2$ to suppress microbial activity during the experiment. We measured electric conductivity, absorbance at 280nm, total nitrogen and dissolved inorganic nitrogen, total phosphorus and soluble reactive phosphorus, Na, K, Mg and Ca amounts in leaf litter and in water. In addition, we examined the effects of water temperature and ion concentrations of ambient water on the leaching process. A total of 6% of the initial ash-free dry mass of leaf litter was lost due to leaching during incubation (four days). Electric conductivity and A280 continued to increase and saturate during the incubation. To compare reaching rates of different nutrients, we fitted leaching dynamics with a hyperbolic saturation function [Y=AㆍX/(B+X)]. From these fittings, we found that ratios of leaching amounts to nutrient concentration in the litter were in the order of K > Na > Mg > P > Ca > N. Leaching from leaf litter of Z. latifolia was dependent on water temperature while it was not related with ion concentrations in the ambient water. Our results suggest that the leaching process of nutrients, especially phosphorus, from aquatic macrophytes provides considerable contribution to the eutrophication of the Paldang Reservoir ecosystem.

• Journal of Forest and Environmental Science
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• v.30 no.2
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• pp.208-217
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• 2014

Leaf litter is the main and quick source of organic matter and nutrient to the soil compared to other parts of litter. This study focused on the nutrients (N, P and K) leaching from leaf litter of Melia azadirachta, Azadirachta indica, Eucalyptus camaldulensis, Swietenia macrophylla, Mangifera indica, Zizyphus jujuba, Litchi chinensis, Albizia saman, Artocarpus heterophyllus, Acacia auriculiformis, Dalbergia sissoo and Khaya anthotheca as the common cropland agroforest tree species of Bangladesh. About (9 to 35) % of initial mass was lost, while Electric Conductivity (EC) and TDS (Total Dissolved Solid) of leaching water increased to (573 to 3,247) ${\mu}S/cm$ and (401 to 2,307) mg/l respectively after 192 hours of leaching process. Mass loss (%) of leaf litter, EC and TDS of leaching water showed significant (ANOVA, p<0.05) curvilinear relationship with leaching time. Initial concentration of NH4, PO4 and K in leaching water was found to increase significantly (p<0.05) up to 48/72 hours and then remained almost constant at later stages (48/72 to 192 hours). Mass loss of leaves; EC, TDS, $NH_4$, $PO_4$ and K in leaching water was varied also significantly (ANOVA, p<0.05) among the studied tree species. All the tree species showed similar pattern of nutrients (K>N>P) release during the leaching process. The highest $NH_4$ (4,097 ppm) and potassium (8,904 ppm) concentration was found for M. azadirachta while the highest $PO_4$ (1,331 ppm) concentration was found for E. camaldulensis in the leaching water. Among the studied tree species, M. azadirachta, A. indica, D. sissoo, E. camaldulensis and Z. jujuba was selected as the best tree species with respect to nutrient leaching.

• Journal of the Korean Wood Science and Technology
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• v.35 no.5
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• pp.46-57
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• 2007

The leachability of boron in zinc borate (ZB)-modified oriented strandboard (OSB) from southern wood species was investigated in this study. The leaching experiments were conducted by exposing edge-sealed OSB samples under running water at $31^{\circ}C$ for 8, 24, 72, and 216 h. The results from leached samples were compared with those from the unleached controls. Boron leaching of the modified OSB occurred upon the initial water exposure, and the leaching rate decreased as the leaching time increased. Initial boric acid equivalent (BAE) level, wood species, and sample thickness swelling significantly influenced the leachability. There was no consistent effect of polyethylene glycol (PEG) on zinc borate leaching. The glue-line washing within OSB due to thickness swelling of the test samples under water and decomposition of the borate to form water-soluble boric acid were thought to be two possible causes for the observed leaching. The relationship between assayed BAE and leaching time followed a decaying exponential function for zinc borate treated OSB. From the boron/zinc ratio after each leaching period, boron element in ZB was more or less leachable. The material constant of the regression models allowed comparing the leachability of the modified OSB for various wood species. An unified leaching method for treated wood composite materials is needed.

• Journal of Korean Society on Water Environment
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• v.16 no.4
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• pp.469-477
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• 2000

Bisphenol-A (BPA), a known endocrine disruptor, is a main building block of epoxy resin which is widely used as a coating agent in residential water storage tanks. Therefore, BPA leaching from the epoxy resin may have adverse effects on human health. The possibility of BPA leaching from three epoxy resins were tested with a modified KS D 8502 method at 20, 50, 75 and $100^{\circ}C$ in deionized water and the specified test water, respectively. BPA leached to the test water was identified using GC-MS and quantified with GC-FID after a sequential extraction and concentration. The results showed that BPA leaching has occurred in all three samples tested. The quantify of BPA leaching from unit area of epoxy resin coating was in the range of $10.677{\sim}273.120{\mu}g/m^2$ for sample A, 29.737~1734.045 for sample B and 52.857~548.778 for sample C depending on the test temperature, respectively. In general, the amount of BPA leaching increased as the water temperature increases. This result implies a higher risk of BPA leaching to drinking water during a hot summer season. In addition, microbial growth, measured by colony forming units, in epoxy coated water tanks was higher than that in a stainless steel tank suggesting that compounds leaching from epoxy resin may support the growth of microorganisms in a residential water holding tank.

• Journal of the Mineralogical Society of Korea
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• v.31 no.2
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• pp.67-73
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• 2018

The objective of this study was to investigate the application of sulfate solvents for the economic and eco-friendly leaching of valuable metals from Au concentrate using an acid bake-water leaching system (AWS). AWS experiments were performed using an electric furnace with various baking temperatures ($100-500^{\circ}C$) and sulfate solvents ($H_2SO_4$, $K_2SO_4$, $(NH_4)_2SO_4$, $MgSO_4$, and $CaSO_4$). The efficiency of the valuable metal leaching increased as the baking temperature was increased to $400^{\circ}C$. Based on the AWS leaching time experiments, the maximum leaching rate occurred with the aqueous $(NH_4)_2SO_4$ solvent. This study demonstrates that aqueous $(NH_4)_2SO_4$ could be used as an effective solvent for valuable metal leaching using an AWS.

• Journal of Soil and Groundwater Environment
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• v.18 no.1
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• pp.85-93
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• 2013

This study is conducted to evaluate the leaching of contaminants from mine tailing by natural water and finally to estimate the leaching and transportation of heavy metal contaminants by rainfall. In order to identify contaminated heavy metal of soil, 17 soil, 2 tailing and 2 waste dump and 2 control samples were taken at mine area and analyzed total metal contents. The leaching experiments were conducted using distilled water. Cu, Pb, Zn was extracted from the reddish mine tailing in a short period time, especially the extraction rate of Cu (45.0%) was highest. The contaminants were leached from the yellowish mine tailing within an hour and the leaching rate of Cd (42.0%) and Zn (17.2%) were relatively high. The reddish soil from the waste dump showed leaching of Cu (5.1%), Pb (4.0%) and Zn (3.3%), however the leaching rate was low except Mi (14.2%). From the yellowish soil sampled from the dumping site, the leaching of Cu (8.2%) and Ni (9.7%) was high while the leaching of Zn (0.2%) were relatively low.

• Journal of the Korean Wood Science and Technology
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• v.34 no.5
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• pp.98-103
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• 2006

Radial and tangential diffusion coefficients of boron in wood under water leaching conditions were determined from the change of concentration profiles of boron. Egner's solution was used to obtain variable diffusion coefficients of boron because it has been known to be the only method to determine variable diffusion coefficients with no cumbersome assumption. The values of diffusion coefficients were between $0.18{\times}10^{-6}m^2/sec$ and $25.6{\times}10^{-6}cm^2/sec$. They increased with the increase of sample thicknesses, and decreased with the increase of leaching times. There was a region where Egner's method was not valid. However, Egner's solution illustrates a convenient way to evaluate diffusion characteristics of boron from wood under water leaching conditions. The diffusion coefficients at wood surface may be regarded as leaching coefficients.

• Nuclear Engineering and Technology
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• v.32 no.1
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• pp.10-16
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• 2000

Preliminary experiment was peformed to investigate the leaching characteristics of paraffin waste forms that had been recently generated in large quantities at domestic nuclear power plants. At first, waste simulants whose compositions were different in mixing ratio of paraffin to boric acid were prepared. Their compressive strengths were measured and ninety-day leaching test of specimen including cobalt was carried out according to ANSI/ANS-16.1 test procedure. Water immersion test was also conducted keeping pace with leaching test and the weight change and the compressive strength of specimen were observed after ninety days. The compressive strength of waste form exhibited 666 psi (4.53 MPa) in the case where mixing ratio of boric acid to paraffin was 78/22, which was adopted in concentrate waste drying system of domestic nuclear power plants. The leaching test resulted in about 50% of the cumulative fraction leached for boric acid and cobalt, respectively. The specific gravity of waste form was 0.87 ［g/g］whose value was less than that of water because the weight loss of about 39% occurred after the water immersion test of ninety days. It was also observed that the waste form which had undergone ninety-day water immersion test exhibited the compressive strength of 203 psi (1.38 MPa).

• Korean Journal of Materials Research
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• v.21 no.12
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• pp.679-684
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• 2011

One of the trace constituents included in cement clinker, chromium, has become prominent and highly noticed lately as a social issue both inside and outside of this country because it affects the human body negatively. The purpose of the present study was to investigate leaching properties of water-soluble hexavalent chromium by different manufacturing conditions of cement clinker. Raw materials were prepared to add different $SiO_2$, $Al_2O_3$ and $Fe_2O_3$ sources. After the raw materials, such as limestone, sand and clay, iron ore was pulverized and mixed, and the raw meal was burnt at $1450^{\circ}C$ in a furnace with an oxidizing atmosphere. Leaching of soluble hexavalent chromium showed a tendency to decrease with an increasing LSF and IM. However, leaching of soluble hexavalent chromium increased with an increasing S.M. Alkali contents of iron source minerals is closely related to the leaching properties of soluble hexavalent chromium. Green sludge has the highest content of alkali added; leaching of water-soluble hexavalent chromium was mostly high. In order to reduce the water-soluble hexavalent chromium in cement, reducing the alkali content in raw materials is important.

• Resources Recycling
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• v.1 no.1
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• pp.29-36
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• 1992

The extration of vanadium and nickel from heavy oil fly ash was carried out by using water ans sulfuric acid as leaching agent. In the leaching with water, vanadium and nickel were extracted 86% and 88% respectively under pulp density of 25g/l, room temperature and leaching time of 60 minutes, but extraction of vanadium decreased with increasing leaching time. Addition of oxidant decreased the extractions of vanadium and nickel, and roasting of fly ash at temperature higher than $300^{\circ}C$ before water leaching decreased the vanadium extraction to about zero. In the leaching with 1N sulfuric acid, the extractions of vanadium and nickel both increased to 96% and the addition of oxidant did not affect the extraction of these metals.