• Journal of Korean Society of Environmental Engineers
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• v.34 no.4
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• pp.288-294
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• 2012

The current growth of nano-industries has resulted in released nanoparticles entering into water and soil ecosystems via various direct or indirect routes. Physicochemical properties of nanoparticles differ from bulk materials, and nanomaterials influence the fates of nanoparticles and the interactions of living or non-living things in the environment. Microcosm analysis is a research methodology for revealing natural phenomena by mimicking part of an ecosystem under controlled conditions. Microcosm study allows for the integrated analysis of toxic effects and fates of nanoparticles in the ecosystem. Ecotoxicity studies of nanomaterials are steadily increasing, and microcosm studies of nanomaterials are currently beginning to surface. In this study, microcosm studies of nanomaterials in water and soil ecosystems were extensively investigated based on SCI(E) papers. We found that the microcosm studies have been reported in 12 instances, and mesocosm studies have been reported in only once until now. Advanced research was mostly evaluated at the microorganism level. But integrated analysis of nanotoxicity is required to research the interactions based of various species. Thus, our studies analysed the trend of microcosm studies on nanomaterials in water and soil ecosystems and suggested future directions of microcosm research of nanomaterials.

• Korean Journal of Ecology and Environment
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• v.49 no.3
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• pp.228-235
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• 2016

Aquatic ecosystems are receiving various harmful effects due to anthropogenic chemical pollutions. To protect wildlife, risk assessments of the chemicals are conducted using reference indexes of toxicity estimated by species-level laboratory tests and/or micro-/mesocosm community-level studies. However, the existing micro-/mesocosm communities are structurally too complicated, and it is also difficult to compare the experimental results directly with those from species-level tests. Here, we developed a procedure of a simple bi-trophic microcosm experiment which contains the common species (a green algae, Pseudokirchneriella subcapitata and a cladoceran, Daphnia magna) for testing chemical toxicities. For the proper operation of bitrophic microcosm experiment, the minimum required concentration of primary producer (P. subcapitata) is $5{\times}10^5cells\;mL^{-1}$. The microcosm system showed higher stability when the initially introduced D. magna population was composed of neonates (<24-h old) than adults and those mixture. This simple microcosm system would be an applicable tool to estimate the disturbing impacts of pollutants on plant-herbivore interactions, and linking the species- and population-/community level risk assessments in the future studies.

• Journal of Soil and Groundwater Environment
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• v.10 no.2
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• pp.52-58
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• 2005

In Korea, little attention has been paid to microbial perchloroethylene (PCE) and/or trichloroethylene (TCE) dechlorination activity and identification of microorganisms involved in PCE reductive dechlorination at a PCE-contaminated aquifer. We performed microcosm tests using the groundwater samples from 4 different contaminated sites (i.e. Changwon A, Changwon B, Bucheon and Yangsan) to assess PCE reductive dechlorination activity. We also adapted molecular techniques to screen what types of known reductive dechlorinators are present at the PCE-contaminated aquifers. In the Changwon A and Changwon B active microcosms where potential electron donors such as sodium propionate, sodium lactate, sodium butyrate, and sodium fumarate, were added, ethylene, an end-product of complete reductive dechlorination of PCE, was detected after a period of 90 days of incubation. In the Bucheon and Yangsan active microcosms, cis-1,2-dichloroethylene (c-DCE) was accumulated without the production of vinyl chloride (VC) and ethylene. Molecular techniques were used to evaluate the microbial community structures in the Changwon B and Yangsan aquifer. We found two sequence types that were closely related to a known PCE to ethylene dechlorinator, named uncultured bacterium clone DCE47, in the Changwon B site clone library. However, in the Yangsan site clone library, no sequence type was closely related to known PCE dechlorinators reported. It is plausible that microorganisms being capable of completely dechlorinating PCE to ethylene may be present in the Changwon B site aquifer. In this study we find that complete PCE reductive dechlorinators are present at some PCE-contaminated sites in Korea. In an engineering point of view this information makes it feasible to apply a biological reductive dechlorination process for remediating PCE- and/or TCE-contaminated aquifers in Korea.

• Economic and Environmental Geology
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• v.36 no.5
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• pp.349-356
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• 2003

As industrial activities are growing, pollutants found in the contaminated land are getting diverse. Some contaminated areas are subject to mixed wastes containing both organic and inorganic wastes such as hydrocarbon and heavy metals. This study concerns with the influence of the degradation of organic pollutants on the coexisting heavy metals, expecially for As. As mainly exists as two different oxidation state; As(III) and As(V) and the conversion between the two chemical forms may be induced by organic degradation in the soil contaminated by mixed wastes. We operated microcosm in an anaerobic chamber for 60 days, using sandy loam. The soils in the microcosm are artificially contaminated both by tetradecane and As, with different combination of As(III) and As(V); As(III):As(V) 1:1, As(III) only and As(V) only. Although not systematic, ratio of As(III)/As(Total) increase slightly at the later stage of experiment. Considering complicated geochemical reactions involving oxidation/reduction of organic materials, Mn/Fe oxides and As, the findings in the study seem to indicate the degradation of the organics is connected with the As speciation. That is to say, the As(V) can be reduced to As(III) either by direct or indirect influence induced by the organic degradation. Although Fe and Mn are good oxidising agent for the oxidation of As(III) to As(V), organic degradation may have suppressed reductive dissolution of the Fe and Mn oxides, causing the organic pollutants to retard the oxidation of As(III) to As(V) until the organic degradation ceases. The possible influence of organic degradation on the As speciation implies that the As in mixed wastes may be have elevated toxicity and mobility by partial conversion from As(V) to As(III).

• Journal of Wetlands Research
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• v.17 no.2
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• pp.203-208
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• 2015

To identify the effect of fallen cherry blossom on the artificial pond ecosystem, microcosm experiment was conducted into the aquatic decomposition of Prunus species petals. Petals were put in $1mm^2$ mesh nylon litter bags. For treatment group, one flower litter bag was placed into each pot microcosm ($27{\times}20{\times}8cm^3$) filled with influent water from the artificial pond, whereas control group microcosm contained pond water only. Decomposition time were set differently (4, 8, 12, 16 days) among treatment groups. At the end of experiment, most petals were decomposed and only 32.3% of initial dry weight remained with the decay rate (k) of $7.06{\times}10^{-2}day^{-1}$. $NO_3-N$ concentration of microcosm water decreased sharply from 1.90 mg/L at first to 0.02 mg/L, whereas $NH_4-N$ concentration increased from 0.03 mg/L to 2.85 mg/L continually. $PO_4-P$ concentration was 0.03 mg/L at first and increased to 2.39 mg/L by decomposition. Therefore, available phosphorus seems to have leached with higher rate than nitrogen from the petals litter. Increase about 0.02 mg/L in $PO_4-P$ concentration could be estimated in artificial pond from the calculation on the total quantity of fallen blossoms. This result suggests that available phosphorus from the decomposed Prunus petals could cause eutrophication in the artificial pond.

• Ecology and Resilient Infrastructure
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• v.1 no.1
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• pp.25-28
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• 2014

Constructed wetlands have widely been employed to improve water quality, but only a few studies have assessed removal efficiencies of cations in pond-type and marsh-type wetlands comparatively. This study conveys removal efficiencies of cations in those types of wetlands. High removal efficiencies of $NH_4{^+}$, $K^+$, $Mg^{2+}$ were observed, which appeared to be related to plant uptake and soil absorption. In contrast, release of $Ca^{2+}$ was distinctive in pond-type wetland of which mechanism is yet to be revealed.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.36 no.5
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• pp.839-846
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• 2016

Since oil leakage is one of the most common nonpoint pollution sources that contaminate soil in Korea, the capacity of soil microbial community for degrading petroleum hydrocarbons should be considered to assess the functional value of soil resource. However, conventional methods (e.g., microcosm experiments) to assess the remediation capacity of soil microbial community are costly and time-consuming to cover large area. The present study suggests a new approach to assess the toluene remediation capacity of soil microbial community using a microbial diversity index, which is a simpler detection method than measuring degradation rate. The results showed that Shannon index of microbial community were correlated with specific degradation rate ($V_{max}$), a degradation factor. Subsequently, a correlation equation was generated and applied to Michaelis-Menten kinetics. These results will be useful to conveniently assess the remediation capacity of soil microbial community and can be widely applied to diverse engineering fields including environment-friendly construction engineering fields.

• Korean Journal of Organic Agriculture
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• v.23 no.4
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• pp.847-858
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• 2015

Bacillus amyloliquefaciens GR4-5 was isolated from the rhizosphere soil of Korean ginseng and displayed broad-spectrum suppression of ginseng root rot pathogens. The survivability of B. amyloliquefaciens GR4-5 in soil was investigated under three different conditions; indoor, outdoor - of which soil was put in 14 mL tube after treatment - and field environments. Soil samples were collected over a four-week period from three experimental designs, and assessed for 16S rRNA gene copy number by quantitative polymerase chain reaction (qPCR). In outdoor condition, the 16S rRNA gene copy number of Bacillus spp. was 8.35 log copies g $soil^{-1}$ immediately after the GR4-5 treatment. Two weeks later, the 16S rRNA gene copy number of Bacillus spp. (6.70 log copies g $soil^{-1}$) was similar to that of the control (6.38 log copies g $soil^{-1}$). In indoor condition, the 16S rRNA gene copy number of Bacillus spp. maintained in a certain level for a longer period than those in outdoor and field. The 16S rRNA gene copy number of Bacillus spp. in field experiment was reduced faster than that of outdoor condition. Our results show that B. amyloliquefaciens GR4-5 can survive in bulk soil for 1 week, indicating its potential use as a biocontrol agent following 7 day application intervals. This study presents that outdoor microcosm system design could be a useful method to assess easily the survivability of beneficial microorganisms.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.4
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• pp.2971-2977
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• 2015

This study aimed to understand the changes in microbial community after algicide dosing to control the fish-killing dinoflagellate Cochlodinium polykrikoides in 10L microcosm. Based on our microcosm experiments, the algicidal activity for C. polykrikoides of yellow clay at the concentrations of 4g and 10g per 10 L was < 20%. At $0.8{\mu}M$ concentration of thiazolidinedione(TD49), the population of C. polykrikoides was controlled to be > 85%. In microbial community, a significant increase in heterotrophic bacterial (HB) abundance was observed at day 1 in the TD49 and yellow clay treatments including control. The HB remained high for 2 days and then gradually decreased. In contrast, the abundance of heterotrophic nanoflagellates (HNFs) increased significantly on days 3 and 5 in the TD49 treatments, indicating that the decline in HB was probably a result of predation by the high density of HNFs. In addition, fluctuations in the aloricate ciliate Uronema sp., which feed on bacteria, was clearly correlated with fluctuations in HB abundance, with a lag period of 1-3 days. Therefore, the short-term responses of the HNF and Uronema sp. may have been a result of the rapidly increasing of HB abundance, which is related to degradation of the dense C. polykrikoides bloom, particularly in the TD49 treatment. In addition, large aloricate ciliate Euplotes sp. was significantly increased after reproduction of HNFs and Uronema sp. Consequently, the algicide TD49 had positive effect on the microbial communities, which indicates that the microbial loop was temporarily enhanced in the microcosm by energy flow from HB through HNFs to ciliate.

• Microbiology and Biotechnology Letters
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• v.46 no.3
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• pp.253-260
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• 2018

Beneficial microorganisms are widely used in the forestry, livestock, and, in particular, agricultural sectors to control soilborne diseases and promote plant growth. However, the industrial utilization of these microorganisms is very limited, mainly due to uncertainty concerning their ability to colonize and persist in soil. In this study, the survival of beneficial microorganisms in field soil microcosms was investigated for 13 days using quantitative PCR with B. subtilis group-specific primers. Bacterial community dynamics of the treated soils were analyzed using 16S ribosomal RNA (rRNA) gene amplicon sequencing on the Illumina MiSeq platform. The average 16S rRNA gene copy number per g dry soil of Bacillus spp. was $4.37{\times}10^6$ after treatment, which was 1,000 times higher than that of the control. The gene copy number was generally maintained for a week and was reduced thereafter, but remained 100 times higher than that of the control. Bacterial community analysis indicated that Acidobacteria ($26.3{\pm}0.9%$), Proteobacteria ($24.2{\pm}0.5%$), Chloroflexi ($11.1{\pm}0.4%$), and Actinobacteria ($9.7{\pm}2.5%$) were abundant phyla in both treated and non-treated soils. In the treated soils, the relative abundance of Actinobacteria was lower, whereas those of Bacteroidetes and Firmicutes were higher compared to the control. Differences in total relative abundances of operational taxonomic units belonging to several genera were observed between the treated and non-treated soils, suggesting that inoculation of soil with the Bacillus strains influenced the relative abundances of certain groups of bacteria and, therefore, the dynamics of resident bacterial communities. These changes in resident soil bacterial communities in response to inoculation of soil with beneficial Bacillus spp. provide important information for the use of beneficial microorganisms in soil for sustainable agriculture.