Spore release by the green alga Ulva: a quantitative assay to evaluate aquatic toxicants

A toxicity test using spore release of the aquatic green alga, Ulva, was developed and evaluated by assessing the toxicity of different organic and inorganic chemicals and elutriates of sewage or waste sludge. The toxic ranking of four metals was: Cu (EC50 of 0.040mgL(-1))>Cd (0.095mgL(-1))>Pb (0.489mgL(-1))>Zn (0.572mgL(-1)). The EC50 for TBTO ranged from 24 to 63microgL(-1). The most toxic VOC was formalin (EC50 of 0.788microlL(-1)) and the least toxic was acetone. Spore release was significantly inhibited in all elutriates; the greatest and least toxic effects were for industrial sewage (3.29%) and filtration bed (10.08%), respectively. The bioassay is simple, inexpensive and sensitive. The cosmopolitan distribution of Ulva means that the test would have a potential application worldwide.     

Determination of cytotoxicity of nephrotoxins on murine and human kidney cell lines

The present study investigates renal inner medullary collecting duct (mIMCD3) cells and human embryonic kidney cells (HEK293) for evaluation of cytotoxicity of nephrotoxic compounds. The 24 h LC(50) values for cisplatin, paraquat and ibuprofen in mIMCD3 cells were 135, 155 and 3600 microM, respectively. The 24 h LC(50) values for paraquat and ibuprofen in HEK293 cells were 180 and 1000 microM, respectively. Effects of hyperosmolality on cytotoxicity of paraquat were additive in mIMCD3 cells. These data demonstrate that renal hyperosmolality has an additive effect on cytoxicity of paraquat.     

Using GA-Ridge regression to select hydro-geological parameters influencing groundwater pollution vulnerability

For groundwater conservation and management, it is important to accurately assess groundwater pollution vulnerability. This study proposed an integrated model using ridge regression and a genetic algorithm (GA) to effectively select the major hydro-geological parameters influencing groundwater pollution vulnerability in an aquifer. The GA-Ridge regression method determined that depth to water, net recharge, topography, and the impact of vadose zone media were the hydro-geological parameters that influenced trichloroethene pollution vulnerability in a Korean aquifer. When using these selected hydro-geological parameters, the accuracy was improved for various statistical nonlinear and artificial intelligence (AI) techniques, such as multinomial logistic regression, decision trees, artificial neural networks, and case-based reasoning. These results provide a proof of concept that the GA-Ridge regression is effective at determining influential hydro-geological parameters for the pollution vulnerability of an aquifer, and in turn, improves the AI performance in assessing groundwater pollution vulnerability.     

Heavy metal contamination and metallothionein mRNA in blood and feathers of Black-tailed gulls (Larus crassirostris) from South Korea

The objectives of this study were to determine levels of heavy metal in the feathers and blood of Black-tailed gulls (Larus crassirostris), to evaluate metallothionein (MT) mRNA level in Black-tailed gulls on three independent islets, and to examine the correlation between heavy metal concentrations and MT mRNA expression. Eleven heavy metals (Al, Cd, Mn, Pb, Cr, Fe, Cu, Zn, Se, Hg, and As) were investigated in blood and feathers of 65 chicks from breeding colonies (Seomando, Hongdo, and Dokdo islet) of South Korea in 2010. Heavy metals were assayed by PerkinElmer NexION 300 inductively coupled plasma mass spectrometry. The mean concentrations of non-essential heavy metals were found to blood containing Cd (0.002?~?0.02 ppm), Pb (0.06?~?0.18) ppm, Hg (0.03?~?0.05) ppm, and As (0.26?~?0.48 ppm), and feather containing Cd (0.05?~?0.30 ppm), Pb (2.47?~?10.80 ppm), Hg (1.18?~?1.57 ppm), and As (0.15?~?0.44 ppm). Chicks on Seomando islet showed the highest levels of metals (Cd, Pb, Mn, Cr, Cu, and Se in blood; Al, As, Mn, Cr, Fe, Cu, and Se in feathers) among the colonies. Concentrations of Pb and Hg in feathers were the highest on Hongdo, and the levels of Cd and Zn in feathers were the highest on Dokdo islet. MT mRNA in the blood of Black-tailed gulls was relatively higher in gulls from Seomando than in gulls from Hongdo and Dokdo islet. MT mRNA level is thus positively correlated to heavy metal concentrations in Black-tailed gulls.     

Assessment of phenanthrene bioavailability in aged and unaged soils by mild extraction

It has become apparent that the threat of an organic pollutant in soil is directly related to its bioavailable fraction and that the use of total contaminant concentrations as a measure of potential contaminant exposure to plants or soil organisms is inappropriate. In light of this, non-exhaustive extraction techniques are being investigated to assess their appropriateness in determining bioavailability. To find a suitable and rapid extraction method to predict phenanthrene bioavailability, multiple extraction techniques (i.e., mild hydroxypropyl-β-cyclodextrin (HPCD) and organic solvents extraction) were investigated in soil spiked to a range of phenanthrene levels (i.e., 1.12, 8.52, 73, 136, and 335 μg g^− 1 dry soil). The bioaccumulation of phenanthrene in earthworm (Eisenia fetida) was used as the reference system for bioavailability. Correlation results for phenanthrene suggested that mild HPCD extraction was a better method to predict bioavailability of phenanthrene in soil compared with organic solvents extraction. Aged (i.e., 150 days) and fresh (i.e., 0 day) soil samples were used to evaluate the extraction efficiency and the effect of soil contact time on the availability of phenanthrene. The percentage of phenanthrene accumulated by earthworms and percent recoveries by mild extractants changed significantly with aging time. Thus, aging significantly reduced the earthworm uptake and chemical extractability of phenanthrene. In general, among organic extractants, methanol showed recoveries comparable to those of mild HPCD for both aged and unaged soil matrices. Hence, this extractant can be suitable after HPCD to evaluate risk of contaminated soils.     

A simplified sampling procedure for the estimation of methane emission in rice fields

Manual closed chamber methods are widely used for CH₄ measurement from rice paddies. Despite diurnal and seasonal variations in CH₄ emissions, fixed sampling times, usually during the day, are used. Here, we monitored CH₄ emission from rice paddies for one complete rice-growing season. Daytime CH₄ emission increased from 0800 h, and maximal emission was observed at 1200 h. Daily averaged CH₄ flux increased during plant growth or fertilizer application and decreased upon drainage of plants. CH₄ measurement results were linearly interpolated and matched with the daily averaged CH₄ emission calculated from the measured results. The time when daily averaged emission and the interpolated CH₄ curve coincided during the daytime was largely invariant within each of the five distinctive periods. One-hourly sampling during each of these five periods was utilized to estimate the emission during each period, and we found that five one-hourly samples during the season accurately reflected the CH₄ emission calculated based on all 136 hourly samples. This new sampling scheme is simple and more efficient than current sampling practices. Previously reported sampling schemes yielded estimates 9 to 32% higher than the measured CH₄ emission, while our suggested scheme yielded an estimate that was only 5% different from that based on all 136-h samples. The sampling scheme proposed in this study can be used in rice paddy fields in Korea and extended worldwide to countries that use similar farming practices. This sampling scheme will help in producing more accurate global methane budget from rice paddy fields.     

Factors dominating stratification cycle and seasonal water quality variation in a Korean estuarine reservoir

A comprehensive monitoring program was conducted during 2005-2007 to investigate seasonal variations of hydrologic stability and water quality in the Yeongsan Reservoir (YSR), located at the downstream end of the Yeongsan River, Korea. A principal component analysis (PCA) was performed to identify factors dominating the seasonal water quality variation from a large suite of measured data--11 physico-chemical parameters from 48 sampling sites. The results showed that three principal components explained approximately 62% of spatio-seasonal water quality variation, which are related to stratifications, pollutant loadings and resultant eutrophication, and the advective mixing process during the episodic rainfall-runoff events. A comparison was then made between YSR and an upstream freshwater reservoir (Damyang Reservoir, DYR) in the same river basin during an autumn season. It was found that the saline stratification and pollutant input from the upstream contributed to greater concentrations of nutrients and organic matter in YSR compared to DYR. In YSR, saline stratification in combination with thermal stratification was a dominant cause of the longer period (for two consecutive seasons) of hypoxic conditions at the reservoir bottom. The results presented here will help better understand the season- and geography-dependent characteristics of reservoir water quality in Asian Monsoon climate regions such as Korea.     

Comparison of DNA extraction methodologies used for assessing fungal diversity via ITS sequencing

Traditional methods of assessing fungal exposure have been confounded by a number of limiting variables. The recent utilization of molecular methods such as internal transcribed spacer (ITS) sequencing of ribosomal RNA genes has provided improved insight into the diversity of fungal bioaerosols in indoor, outdoor and occupational environments. However, ITS analyses may also be confounded by a number of methodological limitations. In this study, we have optimized this technology for use in occupational or environmental studies. Three commonly used DNA extraction methodologies (UltraClean Soil kit, High Pure PCR Template kit, and EluQuik/DNeasy kit) were compared in terms of sensitivity and susceptibility to PCR inhibitors in dust for three common fungal bioaerosols, Aspergillus versicolor, Rhizopus microsporus and Wallemia sebi. Environmental dust samples were then studied using each extraction methodology and results were compared to viable culture data. The extraction methods differed in terms of their ability to efficiently extract DNA from particular species of fungi (e.g. Aspergillus versicolor). In addition, the ability to remove PCR inhibitors from dust samples was most effective using the soil DNA extraction kit. The species composition varied greatly between ITS clone libraries generated with the different DNA extraction kits. However, compared to viable culture data, ITS clone libraries included additional fungal species that are incapable of growth on solid culture medium. Collectively, our data indicated that DNA extraction methodologies used in ITS sequencing studies of occupational or environmental dust samples can greatly influence the fungal species that are detected.     

Monitoring bacterial community structure and variability in time scale in full-scale anaerobic digesters

Using a high-throughput pyrosequencing technology, this study assessed bacterial community structure and time-scale variability in great detail in seven full-scale anaerobic digesters operated variously in terms of influent substrate, digestion temperature, and reactor configuration. Pyrosequencing generated a total of 83,774 sequence reads from 40 digester sludge samples collected monthly for six months. The highest number of sequence reads were detected within Proteobacteria (20.5%), followed by those within Bacteroidetes (19.7%), Firmicutes (17.8%), and Chloroflexi (4.8%). The relative composition of bacterial populations was varied within the digesters as well as between the digesters, and the bacterial community structures were mainly influenced by digestion temperature. Detailed bacterial community structures were assessed by analyzing the operational taxonomic units (OTUs) based on 97% sequence similarity, which resulted in a total of 9051 OTUs. Among these, a total of 31 core OTUs were analyzed and inferred phylogenetically, which enabled us to classify the sequences within an unclassified phylum. Unclassified sequences were mostly affiliated with the sequences within Spirochaetes and Firmicutes. Interestingly, numerically dominant novel phylotypes (18% of the total sequence reads) presumably involved in anaerobic digestion within Spirochaetes were identified. Temporal variability was further explored using a non-metric multidimensional scaling ordination which demonstrated that the variability of the bacterial community within the digesters was smaller than between digesters. Correlation analysis demonstrated that digester performance and operational conditions affected the pattern of bacterial community in the ordination. Additionally, a multi-response permutation procedure revealed that the bacterial communities within the digesters were more similar than those belonging to other digesters statistically, demonstrating a patchiness of the digesters in the distribution of bacterial populations. Overall, this study revealed the correlation of bacterial community structure and time-scale variability with digester performance and operating conditions.