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Understanding the greenhouse gas (GHG) emission from rice paddy fields is essential to come up with appropriate countermeasure in response to global warming. However, GHG emissions from paddy fields in South Korea are not well characterized. The objectives of this study were to estimate the carbon dioxide (CO2) and methane (CH4) emissions from rice paddy fields in South Korea, under the Representative Concentration Pathway 8.5 (RCP-8.5) climate change scenario using the DNDC (i.e., DeNitrification-DeComposition) model at 1-km2 resolution. The performance of the model was verified with field data collected using a closed chamber, which supports the application of the model to South Korea. Both the model predictions and field measurements showed that most (> 95%) GHG emissions occur in the cropping period, between April and October. As a baseline (assuming no climate change), the national sums of the CO2 and CH4 emissions for the 2020s and 2090s were estimated to be 5.8 × 106 and 6.0 × 106 t CO2-equivalents (CO2-eq) year–1 for CO2 and 6.4 × 106 and 6.6 × 106 t CO2-eq year–1 for CH4, respectively, indicating no significant changes over 80 years. Under RCP-8.5, in the 2090s, CH4 emissions were predicted to increase by 10.7 × 106 and 14.9 × 106 t CO2-eq year–1, for a 10- or 30-cm tillage depth, respectively. However, the CO2 emissions gradually decreased with rising temperatures, due to reduced root respiration. Deep tillage increased the emissions of both GHGs, with a more pronounced effect for CH4 than CO2. Intermittent drainage in the middle of the cropping season can attenuate the CH4 emissions from paddy fields. The findings of this work will aid in developing nationwide policies on agricultural land management in the face of climate change.

Cellulose–silk fibroin (CSF) films were prepared by blending cellulose and silk fibroin (SF) in different ratios (10:0, 10:3, 10:6, 10:9, and 10:12 wt%) in 60% LiBr aqueous solution. All of the blend films were transparent, and their coloration gradually increased with increasing SF content. Interestingly, cross-sections of all of the tested films were observed by scanning electron microscopy and exhibited similar morphologies. The silk II structure was not well developed in the CSF; however, regenerated SF affected the crystal structure of the cellulose and formed intermolecular hydrogen bonds with cellulose. EDS mapping showed that cellulose and silk in the film were distributed uniformly. The mechanical properties of the dry-state film was greatly improved with the addition of an appropriate amount of SF. In contrast with the dry-state films, the films in the wet state exhibited smaller tensile strengths and E-modulus as SF content increased; however, the elongation values were higher than those in the dry-state films.

Ecological risk assessment based on scientific data is crucial for understanding causal relationships between chemical pollution and environmental risks. Simultaneously, a balance is required between socioeconomic factors and scientific evidence. The TRIAD approach, which incorporates three lines of evidence (LoE)-chemical (Chem-LoE), ecotoxicological (Ecotox-LoE), and ecological (Eco-LoE)-was applied in five sites of an abandoned mine for site-specific soil ecological risk assessment (SERA). In combination, the three LoEs showed that two sites had extremely high risks, one site had moderate risk, and the other site had low risk. At all sites, Chem-LoE exhibited high-integrated risk values. In Ecotox-LoE and Eco-LoE, some species were not affected despite high metal concentrations in the soil samples collected from the sites, indicating that the bioavailability of metals differed according to the physiochemical properties of the soil medium. This study is significant as multiple analyses were performed considering ecosystem structure to reduce uncertainty in SERA. The results provide information to support effective decision-making risk management to protect the soil ecosystem. Moreover, these findings will be useful in establishing policies and priorities for soil risk management.

For site-specific soil ecological risk assessments (SERAs), an integrated chemical, ecotoxicological, and ecological analysis needs to be performed. The SERA guidelines of international institutions and countries recommend that a SERA be initiated at the screening level to save time and social economic cost, however, they provide no unified test species for this screening level. This study performed SERAs for field soils and confirmed the importance of selecting bioassay test species that reflect the ecotoxicity of field soils at the screening level. To confirm test species that reflect the ecological risk of field soils, correlation analysis was performed on the results of each bioassay with the integrated ecotoxicological risk index (EtoxRI). Our results showed that soil algae, nematodes, and plants were the most representative species in soil assays, with high correlation coefficients with EtoxRI. The results imply the importance of selecting test species that represent ecological risk for the screening level of SERAs. Based on these findings, when using SERAs, species sensitivity, ecological relevance, and economic aspects should be considered when selecting the bioassay test species.

The accumulation of metalloid elements during transfer from contaminated soil to higher trophic levels may potentially result in the exposure of parasitic arthropods to toxic concentrations of these elements. This study examined the transfer of arsenate (As(V)) to aphids (Myzus persicae) from pepper plants cultivated in As(V) contaminated soils of two concentrations (2 and 6 mg As(V)/kg dry soil), and the subsequent biological effects on the aphid parasitoid, Aphidius colemani. Results showed that considerable quantities of As(V) were transferred to the plant in a concentration-dependent manner and were partitioned in the plant parts in the order of roots > stems > leaves. The accumulation of As(V) in the aphids increased with the concentrations in the plants; however, the transfer coefficient of As(V) from leaf to aphid was relatively similar and constant (0.07–0.08) at both soil As(V) concentration levels. Increased levels of As(V) significantly affected fecundity and honeydew production in aphids, but survival and developmental time were unaffected. Fecundity (mummification rate) of the parasitoid was not impaired by host As(V) contamination; however, vitality (eclosion rate) was significantly affected. Results are discussed in relation to possible ecological risks posed by the transfer of soil As(V) via the plant-arthropod system to parasitoid arthropods in agroecosystems.

Ammonia (NH3) is an important precursor for particulate secondary aerosol formation. This study was conducted to evaluate the applicability of a passive sampler (PAS) for estimating the NH3 emission from chemical fertilizer application (85 kg-N&middot, ha&minus, 1) at field scale and to compare the results with a chamber system for the calculation of NH3 emission flux at lab scale. The application of chemical fertilizer increased the ambient NH3 concentration from 7.11 to 16.87 &mu, g&middot, m&minus, 3. Also, the ambient NH3 concentration measured by the PAS was found to be highly influenced by not only the chemical fertilizer application but also the weather (temperature and rainfall). Wind rose diagram data can be useful for understanding the distribution of ambient NH3 concentration. In the case of a chamber with few environmental variables, NH3 was emitted very quickly in the early stages and gradually decreased, whereas it was delayed at intervals of about one week at the site. It was found that daily temperature range, atmospheric disturbance by wind and rainfall, changes in soil moisture, and the presence of a flooded water table were the main influencing factors. The PAS data and the chamber system data were observed to have significant differences in spatial-temporal scale. In order to reduce the gap, it seems to be necessary to further develop a chamber system, in order to improve the precision of field analysis and to strengthen the connection between experimental results.

A surface-engineered nano-support for enzyme laccase-immobilization was designed by grafting the surface of halloysite nanotubes (HNTs) with Fe3O4 nanoparticles and chitosan. Herein, HNTs were magnetized (HNTs-M) by a cost-effective reduction-precipitation method. The synthesized HNTs-M were grafted with 0.25%, 0.5%, 1%, and 2% chitosan (HNTs-M-chitosan), respectively. Synthesized HNTs-M-chitosan (0.25%), HNTs-M-chitosan (0.5%), HNTs-M-chitosan (1%) and HNTs-M-chitosan (2%) were linked with glutaraldehyde (GTA) for laccase immobilization. Among these formulations, HNTs-M-chitosan (1%) exhibited the highest laccase immobilization with 95.13% activity recovery and 100.12 mg/g of laccase loading. The optimized material was characterized thoroughly by scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM), X-ray powder diffraction (XRD), thermal gravimetric analysis (TGA), and vibrating sample magnetometer (VSM) analysis. The immobilized laccase (HNTs-M-chitosan (1%)-GTA-Laccase) exhibited higher pH, temperature, and storage stabilities. The HNTs-M-chitosan (1%)-GTA-Laccase possesses excellent reusability capabilities. At the end of 10 cycles of the reusability experiment, HNTs-M-chitosan (1%)-GTA-Laccase retained 59.88% of its initial activity. The immobilized laccase was utilized for redox-mediated degradation of sulfamethoxazole (SMX), resulting in 41%, 59%, and 62% degradation of SMX in the presence of 2,2&prime, Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS), guaiacol (GUA), and syringaldehyde (SA), respectively. Repeated SMX degradation (57.10% after the sixth cycle) confirmed the potential of HNTs-M-chitosan (1%)-GTA-Laccase for environmental pollutant degradation. Thus, we successfully designed chitosan-based, rapidly separable super-magnetic nanotubes for efficacious enhancement of laccase biocatalysis, which can be applied as nano-supports for other enzymes.

There is a lack of information on how aging affects the sorption of ionizable organic compounds on biochar-amended soils. To that end, this study investigates the sorption of two hydrophobic solutes (anthracene (ANT) and 9-anthroic acid (9-ANCA)) onto biochar-amended (5%, w/w) soils as a function of aging period (0, 6, and 12 months), electrolyte (5 mM CaCl

Paddy mesocosms comprising of rice (Oryza sativa), snail (Pomacea canaliculata), and worm (Tubifex tubifex) were used to assess the damage caused by two acids (HNO3 and H2SO4) at predicted no-effect concentration (PNEC) and hazardous concentration for 50% of species (HC50) levels. In the fourth week, the fresh weight and shoot height of O. sativa at H2SO4-HC50 were reduced by 83.2% and 30.3%, respectively. Wilted leaves (%) at HC50 were approximately twice that at PNEC. No P. canaliculata and T. tubifex were recovered at HC50. At H2SO4-PNEC, the length and weight of P. canaliculata were reduced by 7.4% and 25.9%, respectively, whereas fewer adult (46.5%) and juvenile (84%) T. tubifex were recovered. In the 20th week, rice growth and productivity were correlated with initial pH (pHi) and nitrogen levels. Poor correlation with chlorophyll at the active tillering stage suggests the disturbance of nutrient uptake by roots. Partial least squares path modeling (PLS-PM) results further supported that the pHi directly affects grain yield and quality, as well as plant growth. The indirect effect via intervening fourth-week-variables was also substantial. Therefore, it is important to measure initial pH upon acid spill to estimate the risk to the paddy ecosystem. Information on the change in soil properties associated with acidity will also aid in predicting the yield and quality of grain to be harvested.

Paddy mesocosms comprising of rice (Oryza sativa), snail (Pomacea canaliculata), and worm (Tubifex tubifex) were used to assess the damage caused by two acids (HNO3 and H2SO4) at predicted no-effect concentration (PNEC) and hazardous concentration for 50% of species (HC50) levels. In the fourth week, the fresh weight and shoot height of O. sativa at H2SO4-HC50 were reduced by 83.2% and 30.3%, respectively. Wilted leaves (%) at HC50 were approximately twice that at PNEC. No P. canaliculata and T. tubifex were recovered at HC50. At H2SO4-PNEC, the length and weight of P. canaliculata were reduced by 7.4% and 25.9%, respectively, whereas fewer adult (46.5%) and juvenile (84%) T. tubifex were recovered. In the 20th week, rice growth and productivity were correlated with initial pH (pHi) and nitrogen levels. Poor correlation with chlorophyll at the active tillering stage suggests the disturbance of nutrient uptake by roots. Partial least squares path modeling (PLS-PM) results further supported that the pHi directly affects grain yield and quality, as well as plant growth. The indirect effect via intervening fourth-week-variables was also substantial. Therefore, it is important to measure initial pH upon acid spill to estimate the risk to the paddy ecosystem. Information on the change in soil properties associated with acidity will also aid in predicting the yield and quality of grain to be harvested.

La/Mg/Si-activated carbon derived from palm shell has been a suitable material for removal of aluminum and fluoride from aqueous solution. In the study, the mechanism of simultaneous removal of aluminum and fluoride by La/Mg/Si-activated carbon (La/Mg/Si-AC) was investigated to understand its high efficiency. It was found that the removal of aluminum and fluoride by La/Mg/Si-AC was favored at lower pH compared to the point of zero charge of La/Mg/Si-AC and high temperature. Adsorption capacity of Al(OH)4- was about 10 times higher than that of F- due to the strong binding affinity of Al(OH)4- on protonated surface and competition between F- and OH- toward charged adsorption site. Kinetics results showed that the aluminum and fluoride adsorption were explained using the pseudo-second-order kinetic model and intra-particle diffusion model. Adsorption process of Al(OH)4- and F- was driven by the potential rate-limiting step involved in mass transport process occurred on the boundary diffusion layer of porous adsorbent surface. Electrostatic interaction between protonated surface of La/Mg/Si-AC and negatively charged ions (i.e., Al(OH)4- and F-) as well as ion-exchange between hydroxide and ionic metal species were important mechanisms in the process of aluminum and fluoride adsorption. Driving forces for adsorption of individual Al(OH)4- and F- were not entirely different. Identifying the dominant mechanism will be helpful in understanding the adsorption process and developing new adsorbent.

Leachate from abandoned mine is frequently enriched with toxic elements but their off-site movement is not well addressed. In this study, the attenuation potential of mine-related metallic elements (Zn, As, and Cd) through downward soil was investigated using batch equilibrium sorption and seepage column studies under simulated leachate composition (single, binary, and ternary solutes in 5-mM CaSO 4 ). In the batch result, the retention of Cd was suppressed by 40–45% in the presence of Zn while the Zn was less affected by Cd. The retention of As increased by 14–25% in the presence of both cations, with a greater effect from Zn. The phenomena were explained by the combined effects of sorption selectivity, the relative element abundance, and the operating sorption mechanism (nonspecific vs. specific). These effects also influenced the effluent element concentrations in the seepage study, as numerically indicated by a two-site model fit and moment analysis (e.g., the peak arrival time and peak concentration). For 500 PV seepage, element retention by the column ( M retention ) was strongly correlated ( r 2 = 0.907) with the sorption constant ( K d ∗ ) during the sorption-dominant stage, but the same correlation was poor ( r 2 = 0.346) during the depletion-dominant stage, due to the desorption resistance of As compared to Zn and Cd. Therefore, the attenuation of the leaching potential by surrounding soils and the effect of cosolutes dissolved in the leachate phase must be concurrently understood when assessing the off-site leaching of metallic elements from abandoned mine sites.

In this study, we applied the Denitrification and Decomposition model to predict the greenhouse gas (GHGs, CO2 and N2O) emissions and cabbage yields from 8072 cabbage fields in Korea in the 2020s and 2090s. Model outputs were evaluated as a function of tillage depth (T1, T2, and T3 for 10, 20, and 30 cm) and fertilizer level (F1, F2, and F3 for 100, 200, and 400 kg N ha−1) under the Representative Concentration Pathways 8.5 climate change scenario. For both time periods, CO2 emissions increased with tillage depth, and N2O emissions were predominantly influenced by the level of applied N-fertilizers. Both cabbage yields and GHGs fluxes were highest when the T3F3 farming practice was applied. Under current conventional farming practices (T1F3), cabbage yield was projected at 64.5 t ha−1 in the 2020s, which was close in magnitude to the predicted cabbage demand. In the 2090s, the predicted cabbage supply by the same practice far exceeded the projected demand at 28.9 t ha−1. Cabbage supply and demand were balanced and GHGs emissions reduced by 19.6% in the 2090s when 94% of the total cabbage farms adopted low carbon-farming practices (e.g., reducing fertilizer level). Our results demonstrate the large potential for Korean cabbage farms to significantly contribute towards the mitigation of GHGs emissions through the adoption of low-carbon farming practices. However, in order to incentivize the shift towards sustainable farming, we advise that lower yield and potential economic losses in farmlands from adopting low-carbon practices should be appropriately compensated by institutional policy.

There is a lack of information on how aging affects the sorption of ionizable organic compounds on biochar-amended soils. To that end, this study investigates the sorption of two hydrophobic solutes (anthracene (ANT) and 9-anthroic acid (9-ANCA)) onto biochar-amended (5%, w/w) soils as a function of aging period (0, 6, and 12 months), electrolyte (5 mM CaCl2 and 10 mM KCl), and aqueous pH. The isotherm plot of both solutes was fairly linear (r2 > 0.998) and the linear sorption coefficient (Kd, L kg−1) was obtained from this. In CaCl2 solution at pH 5, the log Kd of ANT tended to decrease (from 3.90 to 3.72) with an increasing aging period, which was attributed to clogged pore surface, whereas the differences in 9-ANCA sorption (from 2.56 to 2.51) were not significant (α = 0.05). The increased ANT sorption at acidic pH ( 8). The spectroscopic data and isoelectric point measurement results indicated that the number of oxygen-containing functional groups and the content of elemental oxygen were both higher in aged samples, resulting in a more polar (negatively charged) surface. The formation of surface polar groups and the associated deformation altered the adsorbent nature of the tested biochar, thereby fortifying the hydrophilic retention propensity for ionizable organic solutes.

Soil attenuation of off-site leaching potential of metallic elements at the two abandoned mine sites was investigated using batch sorption and layered column studies. In batch study, the leachate concentration-specific sorption (Kd*) by downgradient clean soils was in the order of Pb>Cu>Cd>Zn>As for DY site and Pb>As>Cu>Cd>Zn for BS site. In the layered (mine+clean) soil column, element elution was significantly reduced (e.g., no initial flush, retarded peak arrival, and lower peak concentration) while sulfate elution can be an indicator of the dissolution of sulfur-bearing minerals in mine soils. The greatest reduction was observed for Pb and Cu while the lowest was for Cd (2-19%) and Zn (6-51%), consistent with the batch data. Both the reduced elution at slow seepage and concentration drop after flow interruption support the time-limited propensity. In column segments, the sorptive elements (Cu, Pb, and As) were dominantly found in the inlet while less sorptive ones (Zn and Cd) in the outlet. Both batch and column data suggest that the element leaching with mine leachate movement can be greatly attenuated by the interactions with the surrounding downgradient soil during the seepage process.

Chemical stability of As(V) in amended mine-impacted soils was assessed according to functions of incubation period (0, 1, 2, 4, and 6 months), amendment dose (2.5 and 5%), and application timing (0 and 3rd month). Six soils contaminated with 26-209 mg kg-1 of As(V) were collected from two abandoned mine sites and were treated with two alkaline iron-rich materials (mine discharge sludge (MS) and steel-making slag (SS)). Seventeen to 23% of As(V) in soils was labile. After each designated time, As(V) stability was assessed by the labile fractions determined with sequential extraction procedures (F1-F5). Over 6 months, a reduction (26.9-70.4%) of the two labile fractions (F1 and F2) and a quantitative increase (7.4-29.9%) of As(V) in F3 were observed (r 2 = 0.956). Two recalcitrant fractions (F4 and F5) remained unchanged. Temporal change of As(V) stability in a sample was well described by the two-domain model (k fast, k slow, and Ffast). The stabilization (%) correlated well with the fast-stabilizing domain (Ffast), clay content (%), and Fe oxide content (mg kg-1), but correlated poorly with kinetic rate constants (k fast and k slow). Until the 3rd month, the 2.5%-MS amended sample resulted in lower As(V) stabilization (25-40%) compared to the 5% sample (50-60%). However, the second 2.5% MS addition on the 2.5% sample upon the lapse of the 3rd month led to a substantial reduction (up to 38%) of labile As(V) fraction in the following 4th and 6th months. As a result, an additional 15-25% of As(V) stability was obtained when splitting the amendment dose into 3-month intervals. In conclusion, the As(V) stabilization by Fe-rich amendment is time-dependent and its efficacy can be improved by optimizing the amendment dose and its timing.

A common-pool resource (CPR) is a type of good consisting of a natural or human-made resource system. Jeju common ranches are historical CPRs located in Jeju Province where mid-mountainous grassland has been shared for livestock farming by the members of adjacent villages since the 10th century. Because of the recent globalization movement, the number of ranches has decreased from 126 in the 1940s to only 53 in 2015; while the majority of the ranches did not survive the transformation, others have remained active by adopting various solutions. In this study, we analyzed the administrative characteristics of the CPRs to explain their current status (i.e., extinction or continuance as a common property) using logistic regression analysis. From this analysis, four statistically meaningful variables were extracted using a forward stepwise selection method; these include the type of ranch management, ratio of land area to population, number of internal committees in the village, and number of local government grants. These variables correlate well with previously recognized ‘community resilience dimensions’ and can be used to explain the fate of the Jeju common ranches during the study period. This study elucidates what community dimensions should be fortified to promote the resilience of Jeju common ranches in order to effectively cope with the on-going effects of globalization.

The joint toxic effects of binary metal mixtures of copper (Cu), manganese (Mn) and nickel (Ni) on reproduction of Paronhchiurus kimi (Lee) was evaluated using a toxic unit (TU) approach by judging additivity across a range of effect levels (10-90%). For all metal mixtures, the joint toxic effects of metal mixtures on reproduction of P. kimi decreased in a TU-dependent manner. The joint toxic effects of metal mixtures also changed from less than additive to more than additive at an effect level lower than or equal to 50%, while a more than additive toxic effects were apparent at higher effect levels. These results indicate that the joint toxicity of metal mixtures is substantially different from that of individual metals based on additivity. Moreover, the close relationship of toxicity to effect level suggests that it is necessary to encompass a whole range of effect levels rather than a specific effect level when judging mixture toxicity. In conclusion, the less than additive toxicity at low effect levels suggests that the additivity assumption is sufficiently conservative to warrant predicting joint toxicity of metal mixtures, which may give an additional margin of safety when setting soil quality standards for ecological risk assessment.

Leaching of toxic metallic elements (Cu, Zn, As, Cd, and Pb) from two solid mine wastes was characterized under different drying treatments. During 14 batch decant-refill leaching steps, samples were intermittently dried four times in 40 °C oven or −20 °C freezer. For all leachates, the pH, pE, Fe2+/Fe3+, and SO42− were analyzed. The parameters of the two-site model (kfast, kslow, and ffast) and labile fractions (F1 + F2) were determined. High levels of toxic metallic elements were determined in waste samples; however, their leaching was limited, as evidenced by the magnitudes of F1 + F2, ffast, and kslow. Leachate solutions were acidic, at pH 3–4, and oxic, at 150 mV −20 °C drying ≥ continuous wetting. Results indicate that the element leachability is increased through drying events and the leachate concentration is associated with the dissolution reaction of sulfur-bearing minerals. Frequent occurrence of prolonged droughts along with high temperatures over the mine waste disposal site, can enhance the leaching potential of toxic metallic elements.

In the present study, a screening level site-specific ecological risk assessment (ERA) was conducted on 10 abandoned metal mines in Korea to determine the ecological risk and prioritize the mines requiring further investigation. A cost-saving approach was adopted by combining both the chemical (ChemLoE) and the ecotoxicological (EcotoxLoE) lines of evidence for the evaluation of integrated risk (IR), rather than applying the full spectrum of Triad, including ecological LoE. The risk values for ChemLoE were derived by calculating the toxic pressure based on the total and 0.01 M CaCl2 extractable metal(loid) concentrations. The risk values for EcotoxLoE were based on the mortality and reproduction of the collembolan species Paronychiurus kimi in the mine soils. A response surface model with a central composite design (CCD) was constructed to standardize the effects of soil physicochemical properties (i.e., organic matter content, clay content, and soil pH) on the reproduction of P. kimi. The predicted number of offspring was used as a reference for the calculation of risk value for reproduction. The ChemLoE and EcotoxLoE values ranged from 0.34 to 1.00 and 0.12 to 0.49, respectively, in the surveyed mines. The contribution of the ChemLoE value to the IR was higher than that of the EcotoxLoE value for all mines. Overall, two of the 10 mines were classified as high-risk soils with high IR values (IR > 0.76), but large deviations were also observed between the LoEs in these mines, suggesting the need for further studies to confirm the potential risks. The future investigations of these mines should focus particularly on providing additional evidence to reduce the degree of uncertainty for risk assessment.

A novel treatment mix was designed for the simultaneous immobilization of As, Cu, and Pb in contaminated soils using natural (waste oyster shells (WOS)) and industrial (coal mine drainage sludge (CMDS)) waste materials. The treatments were conducted using the standard U.S. sieve size no. 20 (0.85 mm) calcined oyster shells (COS) and CMDS materials with a curing time of 1 and 28 days. The As immobilization treatments were evaluated using the 1-N HCl extraction fluid, whereas the Pb and Cu immobilization treatments were evaluated using the 0.1-N HCl extraction fluid based on the Korean leaching standards. The treatment results showed that the immobilization of As, Cu, and Pb was best achieved using a combination mix of 10 wt% COS and 10 wt% CMDS. This treatment mix was highly effective leading to superior leachability reductions for all three target contaminants (>93 % for As and >99 % for Cu and Pb) for a curing period of 28 days. The X-ray absorption near-edge structure (XANES) results showed that As was present in the form of As(V) in the control sample and that no changes in As speciation were observed following the COS-CMDS treatments. The scanning electron microscopy (SEM)-energy dispersive X-ray spectroscopy (EDX) sample treated with 10 wt% COS and 10 wt% CMDS indicated that As immobilization may be associated with the formation of Ca–As and Fe–As precipitates while Pb and Cu immobilization was most probably linked to calcium silicate hydrates (CSHs) and calcium aluminum hydrates (CAHs).

Leaching of metallic elements (Cu, Zn, As, Cd, and Pb) from two mine-impacted soils (DY and BS) was evaluated by batch decant-refill and seepage flow experiments. During eight consecutive leaching steps, aqueous As concentrations remained relatively constant (approx. 1.6 and 0.1 mg L(-)(1) for DY and BS, respectively), while Cu (0.01-3.2 mg L(-1)), Zn (0.2-42 mg L(-1)), and Cd (0.004-0.3 mg L(-1)) were quickly reduced. The reduction of Pb concentration (0.007-0.02 mg L(-1) and 0.2-0.9 mg L(-1) for DY and BS, respectively) was much lesser. This pattern was well-explained by the biphasic leaching model by allocating a large fast leaching fraction (ffast0.2) for Cu, Zn, and Cd while a negligible ffast for As and Pb (0.001). For all elements in column effluents, mass export through first-flush and steady-state concentration were elevated under slow seepage, with the greatest impact observed for As. Element export was enhanced after flow interruption, especially under fast seepage. A transient drop in As export in slow seepage was likely due to sorption back to soil phase during the quiescent period. The ratio of Fe(2+)/Fe(3+) and SO4(2-) concentration, related to the dissolution of sulfide minerals, were also seepage rate-dependent. The results of batch and column studies imply that the leachate concentration will be enhanced by initial seepage and will be perturbed after quiescent wetting period. The conversion from kinetically leachable pool to readily leachable pool is likely responsible for nonequilibrium metal leaching from the long-term abandoned mine soils.

The sorption of naphthalene (NAP) and 1-naphthoic acid (1-NAPA) onto giant Miscanthus–derived biochar was investigated in methanol volume fractions (fc) of 0–0.6 as a function of ionic composition (5 mM CaCl2 and 10 mM KCl) and liquid pH (2 and 7). The sorption onto biochar was nonlinear with 0.42 ≤ N ≤ 0.95; thus, a concentration-specific sorption constant (Km) was compared. The Km log linearly decreased with increasing fc, except for 1-NAPA from a CaCl2 mixture at pH 7. Isotherm data was fitted with a cosolvency sorption model through which the slope (ασ) of the inverse log linear Km-fc plot and empirical constant (α) were obtained. NAP sorption was well described by the cosolvency model with the α value being 0.41–0.53, indicating a methanol–biochar interaction favoring more sorption than the cosolvency based prediction. In particular, the slope (ασ) of 1-NAPA was lower than that of NAP, indicating less reduction of 1-NAPA sorption (i.e., lower α value) by methanol. In comparison with other sorbents, the α value was approximately intermediate between a humic substance and kaolinite clay. An analysis of FT-IR spectra suggested the transformation of O-containing functional groups by methanol, which will subsequently boost the π–π interaction between an organic solute and biochar. Moreover, Ca2 +-induced sorption between anionic 1-NAPA and a negatively charged biochar surface was also fortified in the methanol mixture. The results revealed unexplored cosolvent effects on organic solute sorption onto biochar and identified the hydrophobic and hydrophilic sorption moieties of biochar as affected by the cosolvent.

Agricultural soil was treated with biochar (5% w/w) produced from two pyrolysis temperatures (400 and 700 °C) of giant Miscanthus (GMC-400 and GMC-700, respectively), and the subsequent sorption of sulfathiazole (STZ) was evaluated as a function of pH (2, 5, and 7) and aging period (0, 3, and 6 months). Because sorption was nonlinear, with 0.51 pH 5 > pH 7. The sorption hysteresis (H) index for the GMC-400 treatment was higher at pH 7 (3.99) than at pH 5(2.53), and both values had increased after 6 months (4.18 and 3.17, respectively). The results of this study clearly demonstrate that the sorption of STZ on GMC-treated soils is greatly enhanced, mainly through the greater micropore surfaces, the abundance of hydrophilic functional groups over time, and π+-π electron donor-acceptor interaction at low pH.

Leachate from ash landfills is frequently enriched with As and Se but their off-site movement is not well understood. The attenuation potential of As and Se by soils surrounding selected landfills during leachate seepage was investigated in laboratory column studies using simulated ash leachate. As(III, V) and Se(IV, VI) concentrations as well as pH, flow rate, and a tracer were monitored in influent and effluent for up to 800 pore volumes followed by sequential desorption, extraction, and digestion of column segments. Column breakthrough curves (BTCs) were compared to predictions based on previously measured sorption isotherms. Early As(V) breakthrough and retarded As(III) breakthrough relative to predicted BTCs are indicative of oxidative transformation during seepage. For Se(VI), which exhibits linear sorption and the lowest sorption propensity, measured BTCs were predicted fairly well by equilibrium sorption isotherms, except for the early arrival of Se(IV) in one site soil, which in part, may be due to higher column pH values compared to batch isotherms. Most of the As and Se retained by soils during leaching was found to be strongly sorbed (60-90%) or irreversibly bound (10-40%) with5% readily desorbable. Redox potential favoring transformation to the more sorptive valence states of As(V) and Se(IV) will invoke additional attenuation beyond equilibrium sorption-based predictions. With the exception of Se(IV) on one site soil, results indicate that attenuation by down-gradient soils of As and Se in ash landfill seepage will often be no less than what is predicted by equilibrium sorption capacity with further attenuation expected due to favorable redox transformation processes, thus mitigating contaminant plumes and associated risks.

The concentrations of heavy metals such as cadmium (Cd), chromium (Cr), copper (Cu), lead (Pb), zinc (Zn), nickel (Ni), and arsenic (As) in sand samples collected from selected children’s playground and their correlation with environmental parameters, such as concentration of particulate matter in the atmosphere (PM 10 ), apartment age (> 5 years), clay and organic matter contents in sand samples, were analyzed. The average heavy metal concentration in samples was 0.040 mg kg -1 for Cd, 0.200 mg kg -1 for Cr, 1.75 mg kg -1 for Cu, 15.1 mg kg -1 for Ni, 3.42 mg kg -1 for Pb, 66.7 mg kg -1 for Zn and 0.750 mg kg -1 for As, all of which were below the environmental regulatory level established by Korea Ministry of Environment. However, in the consideration of direct and oral exposure by children to playground sand, the risk of the concentration range in the samples might be greatly enhanced. Heavy metal concentration in samples collected from high PM 10 (> 70 μg m -3 ) area was slightly greater than in samples from low PM 10 ( -3 ), indicating the contribution of particulate matter in air phase to heavy metal concentration in playground sand samples. The concentrations of both Cd and Pb were the highest in apartments older than 21 years (0.050 mg kg -1 and 5.28 mg kg -1 for Cd and Pb respectively) and showed positive correlation with apartment age (p 10 ) from atmosphere.

A stabilization/solidification treatment scheme was devised to stabilize Pb and Cu contaminated soil from a firing range using renewable waste resources as additives, namely waste oyster shells (WOS) and fly ash (FA). The WOS, serving as the primary stabilizing agent, was pre-treated at a high temperature to activate quicklime from calcite. Class C FA was used as a secondary additive along with the calcined oyster shells (COS). The effectiveness of the treatment was evaluated by means of the toxicity characteristic leaching procedure (TCLP) and the 0.1 M HCl extraction tests following a curing period of 28 days. The combined treatment with 10 wt% COS and 5 wt% FA cause a significant reduction in Pb (>98 %) and Cu (>96 %) leachability which was indicated by the results from both extraction tests (TCLP and 0.1 M HCl). Scanning electron microscopy–energy dispersive X-ray spectroscopy (SEM–EDX) analyses are used to investigate the mechanism responsible for Pb and Cu stabilization. SEM–EDX results indicate that effective Pb and Cu immobilization using the combined COS–FA treatment is most probably associated with ettringite and pozzolanic reaction products. The treatment results suggest that the combined COS–FA treatment is a cost effective method for the stabilization of firing range soil.

Pb(2+) and Cu(2+) contamination at army firing ranges poses serious environmental and health risks to nearby communities necessitating an immediate and prompt remedial action. In this study, a novel mixture of calcined oyster shells (COSs) and waste cow bones (WCBs) was utilized to immobilize Pb(2+) and Cu(2+) in army firing range soils. The effectiveness of the treatment was evaluated based on the Korean Standard leaching test. The treatment results showed that Pb(2+) and Cu(2+) immobilization in the army firing range soil was effective in significantly reducing Pb(2+) and Cu(2+) leachability upon the combined treatment with COS and WCB. A drastic reduction in Pb(2+) (99%) and Cu(2+) leachability (95%) was obtained as compared to the control sample, upon treatment with 5 wt.% COS and 5 wt.% WCB. The combination treatment of COS and WCB was more effective for Pb immobilization, than the treatment with COS or WCB alone. The 5 wt.% COS alone treatment resulted in 95% reduction in Cu(2+) leachability. The SEM-EDX results suggested that Pb(2+) and Cu(2+) immobilization was most probably associated with the formation of ettringite, pozzolanic reaction products and pyromorphite-like phases at the same time.

We investigated effects of phosphorus (P) and iron (Fe) on root elongation (RE) of lettuce in arsenic (As)–spiked soils using response surface methodology (RSM). To stabilize interactions between As and Fe in a soil preparation, the sequential incorporation method using Fe and P (SIMFe-P) was applied. From a phytotoxicity assay, As in roots (Asroot) was negatively associated with RE, Fe in soils, and P in roots and soils. The P in roots was also positively related to RE. In a model study, As and interaction factor between P and Fe showed negative coefficients but others showed positive ones. From a confirmation study, RE on exposure to As was verified to be much greater in soils treated by SIMFe-P than in soils separately treated with both elements. These results indicated that application of SIMFe-P to As-contaminated soils might be expected to have an advantage during the early stage of plant root growth.

Concentrations, distributions, fate, and partitioning of perfluoroalkyl acids (PFAAs) were investigated in surface water (n=34) collected from the Youngsan and Nakdong River Estuaries of South Korea. Thirteen individual PFAAs in water and suspended solids (SS) were quantified by use of HPLC-MS/MS. PFAAs were detected in all samples, which indicated that they were widely distributed in the study area. Greater concentrations of PFAAs were found at some inland sites which seemed to be affected by direct input from point sources, such as wastewater treatment plants, and/or indirect diffusive sources, such as surface runoff. Spatial distributions of PFAAs in estuaries along transects toward the open sea demonstrated that these chemicals were transported to the outer region primarily by water discharged during the rainy season. Field-based partition coefficients (K(d)) for long-chain PFAAs (C≥8) were significantly correlated with salinity (r(2)=0.48 to 0.73, p

This study investigated producing biochar from Geodae-Uksae 1 for soil applications to sequestrate carbon from the atmosphere and improve the productivity of crops. Using a lab-scale packed bed reactor, pyrolysis products of Geodae-Uksae 1 were produced over a temperature range of 300-700°C with a heating rate of 10°C/min. Pyrolysis at 500°C was found appropriate for biochar production considering the properties of char and the amount of heat required. It yielded biochar of 27.2wt.% that contained approximately 48% carbon in the raw biomass. The surface area of the biochar rapidly increased to 181m(2)/g. Large cylindrical pores with diameters of 5-40μm developed within the biochar due to the vascular cell structure of the parent biomass. The byproducts (bio-oil and gases) were also analyzed for use as fuel.

Variation of the chemical extractability and phytoavailability of two metallic elements (e.g., As and Pb) on amendment-treated soils was investigated. Four mine-impacted agricultural soils contaminated with both As (174-491 mg kg-1) and Pb (116-357 mg kg-1) were amended with an iron-rich sludge at the rate of 5 % (w/w). After a 4-, 8-, and 16-week incubation, the extractability of metallic elements was assessed by sequential extraction procedure (SEP; F1-F5). The control without amendment was also run. In amended soils, the labile element mass (i.e., F1 + F2) promptly decreased (15-48 % of As and 5-10 % of Pb) in 4 weeks, but the decrement was continued over 16 weeks up to 70 and 28 % for As and Pb, respectively. The labile mass decrement was quantitatively corresponded with the increment of F3 (bound to amorphous metal oxides). In plant test assessed by radish (Raphanus sativus) grown on the 16-week soils, up to 57 % of As and 28 % of Pb accumulation was suppressed and 10-43 % of growth (i.e., shoot/root elongation and fresh weight) was improved. For both the control and amended soils, element uptake by plant was well correlated with their labile soil concentrations (r 2 = 0.799 and 0.499 for As and Pb, respectively). The results confirmed that the iron-rich material can effectively suppress element uptake during R. sativus seedling growth, most likely due to the chemical stabilization of metallic elements in growth medium.

The well-known cosolvency-induced sorption model is not applicable to predict the sorption of carboxylic acids in cosolvent system. To investigate the phenomenon, sorption and solubility of chlorinated phenols (2,4-dichlorophenol (2,4-DCP) and 2,4,6-trichlorophenol (2,4,6-TCP)) and carboxylic acids (benzoic acid and 2,4-dichlorophenoxyacetic acid (2,4-D)) were measured in soil-methanol mixture with various ionic strengths. The sorption (K(m)) of chlorinated phenols was explained by a cosolvency-induced sorption model; the inverse log-linear relationship between the K(m) and methanol volume fraction (f(c)). However, the K(m) of carboxylic acids increased with increasing f(c). This discrepancy was attributed to the effect of the carboxylic moiety. To explain the effect, solubility was measured for benzoic acid and 2,4,6-TCP from various liquid conditions. For both solutes, the cosolvency power (σ) increased with CaCl(2) concentrations and the salting constant (K(s)) became smaller as f(c) increased. However, the σ value at a given salt concentration and the K(s) value at a given f(c) were greater for 2,4,6-TCP than for benzoic acid, both of which were due to the greater hydrophobicity of the former. Overall, the solubility profiles of the both solutes on combination of f(c) and CaCl(2) concentration evidenced no specific role of the carboxylic moiety. Therefore, it can be reasonably concluded that the positive relationship between K(m) and f(c) for carboxylic organic acid can be attributed to the modification of the activity coefficient occurred in the solid phase, which cannot be traceable by cosolvency-based model.

This study was performed to evaluate the spatial distribution of heavy metals using principal component analysis and Ordinary Kriging technique in the Gangwon Mine site. In the soils from the sub soil, the contents of Zn and Ni in the PC1 were gradually dispersed from south to north direction, while the components of Cd and Hg in the PC2 showed an increase significantly from middle-south area in the Gangwon Mine site. According to the cluster analysis, pollutant metals of As and Cu were presented a strong spatial autocorrelation structure in cluster D. The concentration of As was 0.83mg/kg and shown to increase from the south to north direction. The spatial distribution maps of the soil components using geostatistical method might be important in future soil remediation studies and help decision-makers assess the potential health risk affects of the abandoned mining sites.

The spent potliner (SPL) landfill liner system provides the primary attenuation mechanism that blocks the leaching of ferrocyanide. If the seepage occurs, however, the off-site leaching potential of ferrocyanide will be enhanced, resulting in contaminant dispersion. In this study, the adsorptive attenuation of ferrocyanide by two common lining materials (kaolinite and montmorillonite) was investigated under various seepage settings, such as influent concentration, liner thickness, and seepage velocity. The attenuation of ferrocyanide through both lining materials was obvious by lowering the maximum concentration and retarding the peak arrival time and was greater than that expected from batch data, likely due to the high mass-volume ratio under seepage condition. In comparison, seepage of ferrocyanide through lining material layer was retarded when (1) influent concentration was halved, (2) liner thickness was 1.5-fold, and (3) seepage velocity was halved. These experimental results strongly support the concentration-specific and rate-limited adsorptive attenuation of ferrocyanide by lining materials during the seepage process. An extended desorption front was observed for all seepage conditions; it was particularly more apparent for montmorillonite with a slow seepage velocity, further supporting that the release of adsorbed ferrocyanide from adsorbent is energetically hysteretic. Among the factors investigated in this study, the greatest retardation of ferrocyanide movement from seepage water was achieved upon doubling liner thickness. Therefore, for the design of a SPL landfill liner to minimize the leaching potential and thus the environmental risk of ferrocyanide, optimization of the liner thickness should be considered foremost.

The fate of the acidic organic solute from the soil-water-solvent system is not well-understood. In this study, the effect of the acidic functional group of organic solute in the sorption from cosolvent system was evaluated. The sorption of naphthalene (NAP) and 1-naphthoic acid (1-NAPA) by three kaolinitic soils and two model sorbents (kaolinite and humic acid) were measured as functions of the methanol volume fractions (f (c) ≤ 0.4) and ionic compositions (CaCl(2) and KCl). The solubility of 1-NAPA was also measured in various ionic compositions. The sorption data were interpreted using the cosolvency-induced sorption model. The K (m) values (= the linear sorption coefficient) of NAP with kaolinitic soil for both ionic compositions was log linearly decreased with f (c). However, the K (m) values of 1-NAPA with both ionic compositions remained relatively constant over the f (c) range. For the model sorbent, the K (m) values of 1-NAPA with kaolinite for the KCl system and with humic acid for both ionic compositions decreased with f (c), while the sorption of 1-NAPA with kaolinite for the CaCl(2) system was increased with f (c). From the solubility data of 1-NAPA with f (c), no significant difference was observed with the different ionic compositions, indicating an insignificant change in the aqueous activity of the liquid phase. In conclusion, the enhanced 1-NAPA sorption, greater than that predicted from the cosolvency-induced model, was due to an untraceable interaction between the carboxylate and hydrophilic soil domain in the methanol-water system. Therefore, in order to accurately predict the environmental fate of acidic pesticides and organic solutes, an effort to quantitatively incorporate the enhanced hydrophilic sorption into the current cosolvency-induced sorption model is required.