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.     

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.     

Water Quality and Pollution in the Hunchun Basin, China

Chemical properties and pollution of water resources were studied in the Hunchun basin, which is located in northeast China and borders directly North Korea and Russia along the Tumen river. Water quality was characterised according to its major constituents and geological features. Ground waters could generally be grouped into (Ca+Mg)-HCO₃ type and (Ca+Mg)-(SO₃+Cl) type in first and the second terrace areas, respectively. The mixing of these two types depends on the local conditions, such as pumping or permeability variations.Hunchun city is a pollution source for local water resources due to its uncontrolled sewage and urban discharge. In a previous study of the southwestern part of the Hunchun basin, groundwater contamination by Fe, Mn and NO₃-N was reported. In addition, this study identified Cd and F as prevailing contaminants in the water resources. Pollution of water resources by these contaminants appeared to be affected by the application of fertilisers, irrigation practice, variation of aquifer characteristics, solubility of mineral phases, and discharge of domestic sewage. Wide distribution and high levels of Cd and F in surface- and ground waters could pose significant problems if they are utilised as major water supply sources.     

Proteomic analysis in Daphnia magna exposed to As(III), As(V) and Cd heavy metals and their binary mixtures for screening potential biomarkers

In this study, the effects of three widespread heavy metals, As(III), As(V) and Cd, and their binary mixtures on the proteomic profile in D. magna were examined to screen novel protein biomarkers using the two-dimensional gel electrophoresis method (2DE). Ten 20d daphnia were exposed to the LC20 concentrations for each of a total of 8 treatments, including the control, As(III), As(V), Cd, [As(III)+As(V)], [As(III)+Cd], [As(V)+Cd], and [As(III), As(V), Cd], for 24 h before protein isolation. Three replicates were performed for each treatment. These protein samples were employed for 2DE experiments with a pH gradient gel strip from pH 3 to pH 10. The protein spots were detected by a silver staining process and their intensities were analyzed by Progenesis software to discover the differentially expressed proteins (DEPs) in response to each heavy metal. A total of 117 differentially expressed proteins (DEPs) were found in daphnia responding to the 8 treatments and mapped onto a 2D proteome map, which provides some information of the molecular weight (MW) and pI value for each protein. All of these DEPs are considered as potential candidates for protein biomarkers in D. magna for detecting heavy metals in the aquatic ecosystem. Comparing the proteomic results among these treatments suggested that exposing D. magna to binary mixtures of heavy metals may result in some complex interactive molecular responses within them, rather than just the simple sum of the proteomic profiles of the individual chemicals, (As(III), As(V), and Cd).     

Photocatalytic pre-treatment with food-grade TiO2 increases the bioavailability and bioremediation potential of weathered oil from the Deepwater Horizon oil spill in the Gulf of Mexico

Using the 2010 Deepwater Horizon oil spill in the Gulf of Mexico as an impetus, we explored the potential for TiO₂-mediated photocatalytic reactive oxygen species (ROS) generation to increase the bioavailability (solubility) and biodegradability of weathered oil after a spill. Food grade TiO₂, which is FDA approved for use as food additive in the United States, was tested as a photocatalyst for this novel application. Photocatalytic pre-treatment (0.05 wt.% TiO₂, UV irradiation 18 W m^?2, 350–400 nm) for 24 h in a bench top photoreactor increased the soluble organic carbon content of weathered oil by 60%, and enhanced its subsequent biodegradation (measured as O₂ consumption in a respirometer) by 37%. Photocatalytic pre-treatment was also tested outdoors under sunlight illumination, but no significant increase in solubility or biodegradation was observed after 11 d of exposure. Although sunlight irradiation of food-grade TiO₂ generated ROS (assessed by the degradation of 4-chlorophenol as a probe compound), the efficacy of weathered oil pre-treatment was apparently hindered by sinking of the photocatalysts under quiescent conditions and illumination occlusion by the oil. Overall, results indicate that photocatalytic pre-treatment to stimulate bioremediation of weathered oil deserves further consideration, but controlling the buoyancy and surface hydrophobicity of the photocatalysts will be important for future efforts to enable ROS generation in proximity to the target compounds.     

Evaluation of the antifungal effects of bio-oil prepared with lignocellulosic biomass using fast pyrolysis technology

This study was performed to investigate the utility of bio-oil, produced via a fast pyrolysis process, as an antifungal agent against wood-rot fungi. Bio-oil solutions (25-100 wt.%) were prepared by diluting the bio-oil with EtOH. Wood block samples (yellow poplar and pitch pine) were treated with diluted bio-oil solutions and then subjected to a leaching process under hot water (70 °C) for 72 h. After the wood block samples were thoroughly dried, they were subjected to a soil block test using Tyromyces palustris and Trametes versicolor. The antifungal effect of the 75% and 100% bio-oil solutions was the highest for both wood blocks. Scanning electron microscopy analysis indicated that some chemical components in the bio-oil solution could agglomerate together to form clusters in the inner part of the wood during the drying process, which could act as a wood preservative against fungal growth. According to GC/MS analysis, the components of the agglomerate were mainly phenolic compounds derived from lignin polymers.     

Visioneering: an essential framework in sustainability science

The science of sustainability has inevitably emerged as a vibrant field of research and education that transcends disciplinary boundaries and focuses increasingly on understanding the dynamics of social-ecological systems (SES). Yet, sustainability remains an elusive concept, and its nature seems unclear for the most part. In order to truly mobilize people and nations towards sustainability, we place emphasis on the necessity of understanding the nature, cost and principles of ‘visioneering’—the engineering of a clear vision. In SES, purpose is the most important pillar, which gives birth to vision—the key to fulfilling the systems’ mission. Such a systems perspective leads us to redefine resilience as jumping back to the original purpose, for which SES do not necessarily retain the same structures and functioning after disturbances. A sustainable future will require purpose-driven transformation of society at all scales, guided by the best foresight, with insight based on hindsight that science can provide. Visioneering with resilience-based systems thinking will provide communities with a logical framework for understanding their interconnections and purposes, envisioning a sustainable web of life, and eventually dancing with the systems.     

Evaluation of the potential impact of polluted sediments using Manila clam Ruditapes philippinarum: bioaccumulation and biomarker responses

An assessment was made to monitor the short-term impact of heavily polluted sediments that may move out from the brackish man-made Lake Shihwa outside of the sea dike due to operations of a tidal power plant. Here, we exposed the Manila clam Ruditapes philippinarum collected from the western coast of Korea to natural sediment under lab condition for 96?h. Sediments were collected from Lake Shihwa and outside of the sea dike representing polluted and reference conditions, respectively. The results of chemical analysis revealed that the concentrations of nonylphenol and heavy metals in water and sediment from the inner region of Lake Shihwa were significantly higher than those of reference sediments. After 48 and 96?h of exposure, 30 specimens of clams were sampled from each experimental condition, and concentrations of nonylphenol and metals were measured in clams, water, and sediments. Several biomarkers, including concentrations of metallothionein-like proteins, and activities of the antioxidant enzymes glutathione S-transferase and catalase were determined in clams to characterize the effects of polluted sediments to clams. After 96?h of exposure, R. philippinarum assimilated nonylphenol up to 71 times compared to initial concentrations. However, there was no apparent uptake of heavy metals into the clams. Additionally, antioxidant enzymes exhibited higher activities in clams exposed to the polluted sediment. The results of the present study with physiological responses in R. philippinarum suggest that sediment transportation caused by the operation of a tidal power plant in Lake Shihwa will have striking effects on benthic organisms in the adjacent coastal area.     

Distribution and characteristics of PAHs in sediments from the marine environment of Korea

To assess the contamination of polycyclic aromatic hydrocarbons (PAHs) in the marine environment of Korea, 117 sediment samples along the coast were collected and analyzed. This study provides perspectives on concentration ranges and on geographic distributions of PAHs. Sum of 16 PAHs concentrations are in the range of 8.80-18500 ng/g dry weight. Industrialized and urbanized region showed high level of PAHs contamination. When compared with nationwide monitoring results of USA and UK, concentration of total PAHs are in the order of UK>US>this study. Major PAHs sources inferred from diagnostic indices and statistical approach were both pyrogenic and petrogenic. In coastal and offshore sediments of Korea, 7.76% sites had a mean PAH ERL quotient >1.0, indicating the potential to cause adverse effects in sensitive species. Youngil Bay was recognized as highly contaminated with PAHs, and recommended to be managed with special plan.     

Mineralization of phenol by Ce(IV)-mediated electrochemical oxidation in methanesulphonic acid medium: a preliminary study

The mediated electrochemical oxidation (MEO) process using cerium(IV) in methanesulphonic acid (MSA) as the oxidizing medium was employed for the mineralization of phenol in batch and continuous feeding modes. Although nitric acid was an extensively studied electrolyte for organic mineralization reactions in MEO processes it does possess the problem of NO(x) gas production during the reduction of nitric acid in the cathode compartment of the electrochemical cell. This problem could be circumvented by proper choice of the electrolyte medium such as MSA. The mediator cerium in MSA solution was first oxidized to higher oxidation state using an electrochemical cell. The produced Ce(IV) oxidant was then used for the destruction of phenol. It was found that phenol could be mineralized to CO2 by Ce(IV) in MSA. The evolved CO2 was continuously measured and used for the calculation of destruction efficiency. The destruction efficiency was observed to be 85% based on CO2 evolution for 1000 ppm phenol solution at 80 degrees C in continuous feed mode.