The effects of heavy rain on the fate of urban and agricultural pollutants in the riverside area around weirs using multi-isotope, microbial data and numerical simulation.

The increase in extreme heavy rain due to climate change is a critical factor in the fate of urban and agricultural pollutants in aquatic system. Nutrients, including NO and PO, are transported with surface and seepage waters into rivers, lakes and aquifers and can eventually lead to algal blooms. δN-NO, δO-NO, and δB combined with hydrogeochemical and microbial data for groundwater and surface water samples were interpreted to evaluate the fate of nutrients in a riverside area around weirs in Daegu, South Korea.

Spatial investigation of water quality and estimation of groundwater pollution along the main stream in the Geum River Basin, Korea.

This study aims to identify spatially water quality distribution of groundwater and surface water in reservoirs, and comprehensively to address possible influencing factors. The concentration of NO in the reservoirs along the main stream of the Geum River was generally lower than that in groundwater. The pollution level of the reservoir, especially the particulate pollutant SS, clearly showed seasonal variations and increased significantly downstream.

National-scale investigation of dual nitrate isotopes and chloride ion in South Korea: Nitrate source apportionment for stream water.

Nitrate sources in surface water have been identified using dual-isotope compositions of nitrate with various tools to efficiently manage the water quality at the local scale. Correlation between Cl and NO has also been used to identify NO. In this study, we assess the reliability of the dual-isotope approach and Cl in terms of nitrate source apportionment.

Evaluating the sources and fate of nitrate in riparian aquifers under agricultural land using in situ-measured noble gases, stable isotopes, and metabolic genes.

Riparian zones with their buffering ability and abundant water supply are often subjected to intensive agricultural activities. We investigated a riparian aquifer located near a stream in South Korea that recently experienced sharply decreasing groundwater levels and elevated nitrate (NO) concentrations, which were attributed to local agricultural activities. Our goal was to identify the predominant nitrogen sources and NO removal processes.

Estimation of nutrient sources and fate in groundwater near a large weir-regulated river using multiple isotopes and microbial signatures.

The excessive input of nutrients into groundwater can accelerate eutrophication in associated surface water systems. This study combined hydrogeochemistry, multi isotope tracers, and microbiological data to estimate nutrient sources and the effects of groundwater-surface water interactions on the spatiotemporal variation of nutrients in groundwater connected to a large weir-regulated river in South Korea. δB and δN-NO values, in combination with a Bayesian mixing model, revealed that manure and sewage contributed 40 % and 25 % respectively to groundwater nitrate, and 42 % and 27 % to nitrate in surface water during the wet season.

Analysis of Natural Organic Matter in Water from Cold and Hot Mineral Springs in South Korea Using 15T FT-ICR-MS.

The natural organic matter (NOM) properties in water from cold and hot mineral springs in South Korea are not well documented. We analyzed the characteristics of NOM in water from 25 cold and hot mineral springs located across South Korea. The NOM of each sample was concentrated using solid-phase extraction and analyzed using 15T Fourier-transform ion cyclotron resonance mass spectrometry.

Exposure of Metal Oxide Nanoparticles on the Bioluminescence Process of and Recombinant Strains.

Comparison of the effects of metal oxide nanoparticles (NPs; CuO, NiO, ZnO, TiO, and AlO) on different bioluminescence processes was evaluated using two recombinant ( and ) strains of with same inducer exposure. Different sensitivities and responses were observed according to the type of NPs and recombinant strains. EC values were determined.

Spatial distributions of oxygen and hydrogen isotopes in multi-level groundwater across South Korea: A case study of mountainous regions.

This study presents the spatial distributions of stable isotopes for groundwater according to well depth and spring water across South Korea, using an interpolation model to provide baseline information for hydrological studies. In total, 888 groundwater and 108 spring water samples were collected across South Korea; their oxygen and hydrogen isotopic compositions (δO and δH) were analyzed. δO and δH values biased toward the summer local meteoric water line and low d-excess values indicate that summer precipitation is important for groundwater recharge.

Comparisons of the Effect of Different Metal Oxide Nanoparticles on the Root and Shoot Growth under Shaking and Non-Shaking Incubation, Different Plants, and Binary Mixture Conditions.

We evaluated the toxicity of five metal oxide nanoparticles (NPs) in single or binary mixtures based on root and shoot growth of two plant species under non-shaking and shaking conditions. The effects of NPs on root and shoot growth differed depending on the NP type, incubation condition, and plant type. The half maximal effective concentration (EC) of NPs based on root growth were significantly lower, by 2.

Evaluation of the Effects of Particle Sizes of Silver Nanoparticles on Various Biological Systems.

Seven biological methods were adopted (three bacterial activities of bioluminescence, enzyme, enzyme biosynthetic, algal growth, seed germination, and root and shoot growth) to compare the toxic effects of two different sizes of silver nanoparticles (AgNPs). AgNPs showed a different sensitivity in each bioassay. Overall, the order of inhibitory effects was roughly observed as follows; bacterial bioluminescence activity ≈ root growth > biosynthetic activity of enzymes ≈ algal growth > seed germination ≈ enzymatic activity > shoot growth.

Comparative Effects of Particle Sizes of Cobalt Nanoparticles to Nine Biological Activities.

The differences in the toxicity of cobalt oxide nanoparticles (Co-NPs) of two different sizes were evaluated in the contexts of the activities of bacterial bioluminescence, - gene, enzyme function and biosynthesis of β-galactosidase, bacterial gene mutation, algal growth, and plant seed germination and root/shoot growth. Each size of Co-NP exhibited a different level of toxicity (sensitivity) in each biological activity. No revertant mutagenic ratio (greater than 2.

Oxidation and reduction of redox-sensitive elements in the presence of humic substances in subsurface environments: A review.

The oxidation and reduction (redox) processes of redox-sensitive elements (RSE) in the presence of humic substances (HS) have become a significantly important issue in the terms of biogeochemical cycles. Redox processes are crucial for determining the speciation, mobility, toxicity, and bioavailability of RSE in natural environments. It is known that HS act as an effective redox mediator for accepting and donating electrons, and thereby transfers them to RSE.

Toxicity Evaluation of Individual and Mixtures of Nanoparticles Based on Algal Chlorophyll Content and Cell Count.

The toxic effects of individual and binary mixtures of five metal oxide nanoparticles (NPs) were evaluated based on changes in two endpoints of algal growth: the cell count and chlorophyll content. Various effects were observed according to the concentration tested and type of NPs, and there were no significant differences in findings for the two endpoints. In general, ZnO NPs caused the greatest inhibition of algal growth, and Fe₂O₃ NPs the least.

Evaluation of the Effects of Nanoparticle Mixtures on Brassica Seed Germination and Bacterial Bioluminescence Activity Based on the Theory of Probability.

Effects of binary mixtures of six metal oxide nanoparticles (NPs; 54 combinations) on the activities of seed germination and bacterial bioluminescence were investigated using the theory of probability. The observed toxicities of various NPs combinations were compared with the theoretically expected toxicities, calculated based on individual NPs toxicities. Different sensitivities were observed depending on the concentrations and the types of NPs.

Determination of recharge fraction of injection water in combined abstraction-injection wells using continuous radon monitoring.

The recharge fractions of injection water in combined abstraction-injection wells (AIW) were determined using continuous radon monitoring and radon mass balance model. The recharge system consists of three combined abstraction-injection wells, an observation well, a collection tank, an injection tank, and tubing for heating and transferring used groundwater. Groundwater was abstracted from an AIW and sprayed on the water-curtain heating facility and then the used groundwater was injected into the same AIW well by the recharge system.

Hydrologic Controls on Nitrogen Cycling Processes and Functional Gene Abundance in Sediments of a Groundwater Flow-Through Lake.

The fate and transport of inorganic nitrogen (N) is a critically important issue for human and aquatic ecosystem health because discharging N-contaminated groundwater can foul drinking water and cause algal blooms. Factors controlling N-processing were examined in sediments at three sites with contrasting hydrologic regimes at a lake on Cape Cod, MA. These factors included water chemistry, seepage rates and direction of groundwater flow, and the abundance and potential rates of activity of N-cycling microbial communities.

Using ²²²Rn as a naturally occurring tracer to estimate NAPL contamination in an aquifer.

The naturally occurring radioisotope (222)Rn was used as a partitioning tracer to evaluate the presence and amount of a non-aqueous phase liquid (NAPL) in an aquifer. The batch experiment results of a diesel contaminated soil showed that the emanation rate of (222)Rn decreased to 31%, relative to a background rate. Batch experiment results of water contaminated by gasoline, diesel, PCE and TCE were similar.

Molecular analysis of spatial variation of iron-reducing bacteria in riverine alluvial aquifers of the Mankyeong River.

Alluvial aquifers are one of the mainwater resources in many countries. Iron reduction in alluvial aquifers is often a major anaerobic process involved in bioremediation or causing problems, including the release of As trapped in Fe(III) oxide. We investigated the distribution of potential iron-reducing bacteria (IRB) in riverine alluvial aquifers (B1, B3, and B6 sites) at the Mankyeong River, Republic of Korea.

Land-use controls on sources and fate of nitrate in shallow groundwater of an agricultural area revealed by multiple environmental tracers.

Sources and transformation processes of nitrate in groundwater from shallow aquifers were investigated in an agricultural area in the mid-western part of South Korea using a multi-tracer approach including δ²H and δ¹⁸O values of water, δ¹⁵N and δ¹⁸O values of nitrate, Cl/Br ratios and chlorofluorocarbons (CFCs). The study area was comprised of four land-use types with natural areas at higher altitudes, upland areas with fruit orchards, paddy fields and residential areas at lower elevations. The isotopic composition of water was suitable for distinguishing groundwater that had infiltrated in the higher elevation natural areas with lower δ²H and δ¹⁸O values from groundwater underneath paddy fields that was characterized by elevated δ²H and δ¹⁸O values due to evaporation.