Mechanism for the stabilization/solidification of arsenic-contaminated soils with Portland cement and cement kiln dust

In this study, the mechanism for the stabilization/solidification (S/S) of arsenic (As)-contaminated soils with Portland cement (PC), and cement kiln dust (CKD) using 1 N HCl extraction fluid, X-ray powder diffraction (XRPD), X-ray absorption near edge structure (XANES) and Extended X-ray absorption fine structure (EXAFS) spectroscopy was investigated. The degree of As immobilization after stabilization was assessed using a 1 N HCl extraction on the basis of the Korean Standard Test (KST). After 1 day of curing with 30 wt% PC and 7 days of curing with 50 wt% CKD, the concentration of As leached from the amended soils was less than the Korean countermeasure standard (3 mg L^?1). The As concentrations in the leachate treated with PC and CKD were significantly decreased at pH > 3, indicating that pH had a prevailing influence on As mobility. XRPD results indicated that calcium arsenite (Ca–As–O) and sodium calcium arsenate hydrate (NaCaAsO₄·7.5H₂O) were present in the PC- and CKD-treated slurries as the key phases responsible for As(III) and As(V) immobilization, respectively. The XANES spectroscopy confirmed that the As(III) and As(V) oxidation states of the PC and CKD slurry samples were consistent with the speciated forms in the crystals identified by XRPD. EXAFS spectroscopy showed As–Ca bonding in the As(III)-PC and As(III)-CKD slurries. The main mechanism for the immobilization of As-contaminated soils with PC and CKD was strongly associated with the bonding between As(III) or As(V) and Ca.     

Blood levels of cadmium and lead in residents near abandoned metal mine areas in Korea

We analyzed national data on blood lead levels (BLL) and blood cadmium levels (BCL) in residents living near 38 abandoned metal mining areas (n?=?5,682, 18–96 years old) in Korea that were collected by the first Health Effect Surveillance for Residents in Abandoned Metal mines (HESRAM) from 2008 to 2011. The geometric mean BCL and BLL were 1.60 μg/L (95 % CI?=?1.57–1.62 μg/L) and 2.87 μg/dL (95 % CI?=?2.84–2.90 μg/dL), respectively, notably higher than levels in the general population in Korea and other countries. We found significantly higher BLL and BCL levels in people living within 2 km of an abandoned metal mine (n?=?3,165, BCL?=?1.87 μg/L, BLL?=?2.91 μg/dL) compared to people living more than 2 km away (n?=?2,517, BCL?=?1.31 μg/L, BLL?=?2.82 μg/dL; P?<?0.0001) and to the general population values reported in the literature.     

Monitoring of selected veterinary antibiotics in environmental compartments near a composting facility in Gangwon Province, Korea

Many studies have been recently reported that veterinary antibiotics released into the environment have a detrimental effect on humans such as the occurrence of antibiotic-resistant bacteria. However, only limited information is available regarding to the release of antibiotics in environmental compartments in Korea. Objectives of this study were to evaluate the concentrations of antibiotics in water, sediment, and soil adjacent to a composting facility in Korea and to determine the dilution effects of antibiotics when released into the environment. Seven antibiotics of chlortetracycline, oxytetracycline, tetracycline, sulfamethazine, sulfamethoxazole, sulfathiazole, and tylosin were evaluated by high-performance liquid chromatography?Ctandem mass spectrometry following pretreatment using solid-phase extraction to clean the samples. Results showed that the highest concentration of each antibiotic in both aqueous and solid samples was detected from a site adjacent to the composting facility. We also found that the studied water, sediment, and soil samples are contaminated by veterinary antibiotics throughout comparison with studies from other countries. However, relatively lower concentrations of each antibiotic were observed from the rice paddy soil located at the bottom of the water stream. Further research is necessary to continuously monitor the antibiotics release into ecosystems, thereby developing an environmental risk assessment.     

Thermal and Biodegradable Properties of Poly(<Emphasis Type="SmallCaps">l</Emphasis>-lactide)/Poly(ε-Caprolactone) Compounded with Functionalized Organoclay

Poly(l-lactide) (PLLA)/Poly(ε-caprolactone) (PCL) blends were compounded with commercially available organoclay Cloisite 25A (C25A) and C25A functionalized with epoxy groups, respectively. Epoxy groups on the surface of C25A were introduced by treating C25A with (glycidoxypropyl)trimethoxy silane (GPS) to produce so called Functionalized Organoclay (F-C25A). The silicate layers of PLLA/PCL/F-C25A were exfoliated to a larger extent than PLLA/PCL/C25A. Incorporation of the epoxy groups on C25A improved significantly mechanical properties of PLLA/PCL/C25A. The larger amount of exfoliation of the silicate layers in PLLA/PCL/F-C25A as compared with that in PLLA/PCL/C25A was attributed to the increased interfacial interaction between the polyesters and the clay due to chemical reaction. Thermo gravimetric analysis revealed that the nanocomposites with exfoliated silicate layers were more thermally stable than those with intercalated silicate layers. The biodegradability of the neat PLLA/PCL and corresponding nanocomposite was studied under compost, and the rate of biodegradation of PLLA/PCL increased after nanocomposite preparation.     

Economic and environmental optimization of a multi-site utility network for an industrial complex

Most chemical companies consume a lot of steam, water and electrical resources in the production process. Given recent record fuel costs, utility networks must be optimized to reduce the overall cost of production. Environmental concerns must also be considered when preparing modifications to satisfy the requirements for industrial utilities, since wastes discharged from the utility networks are restricted by environmental regulations. Construction of Eco-Industrial Parks (EIPs) has drawn attention as a promising approach for retrofitting existing industrial parks to improve energy efficiency. The optimization of the utility network within an industrial complex is one of the most important undertakings to minimize energy consumption and waste loads in the EIP.In this work, a systematic approach to optimize the utility network of an industrial complex is presented. An important issue in the optimization of a utility network is the desire of the companies to achieve high profits while complying with the environmental regulations. Therefore, the proposed optimization was performed with consideration of both economic and environmental factors.The proposed approach consists of unit modeling using thermodynamic principles, mass and energy balances, development of a multi-period Mixed Integer Linear Programming (MILP) model for the integration of utility systems in an industrial complex, and an economic/environmental analysis of the results. This approach is applied to the Yeosu Industrial Complex, considering seasonal utility demands. The results show that both the total utility cost and waste load are reduced by optimizing the utility network of an industrial complex.     

Estimation of the recycled content of an existing construction project

The Government's Sustainable Buildings Task Group recently recommended a benchmark requirement for a minimum 10% of reused/reclaimed or recycled content (by material value) in construction projects. The benchmark would be implemented through Building Regulations and public sector procurement. This paper presents the findings of a pilot study to inform decision-making on the feasibility of setting and meeting such a requirement.The project involved determining current levels of recycled content in Defence Estates’ standard design for modern barracks accommodation, and quantifying the scope to increase this content. The existing designs for the new barracks were found to use nearly 20% recycled and recovered materials. The project identified opportunities to increase this proportion to nearly 25% with no increase in cost or risk.     

Photocatalytic oxidation of propoxur in aqueous titanium dioxide suspensions

Abstract

The photocatalytic oxidation of propoxur, a nitrogen‐containing pesticide, has been investigated using aqueous TiO₂ suspensions as catalyst in this study. The operating variables considered in the study were initial pH, temperature, [H₂O₂] and TiO₂ loading. Results showed that 1 g/l of TiO₂ was the optimum dosage for oxidizing propoxur in this system. Hydrogen peroxide can increase the oxidation rate with increasing its initial concentration. There was no obvious difference in the rate of propoxur oxidation at the initial pH of 4, 6 and 9, and the final pHs of reaction solutions were around 5.5. However, propoxur degraded slower at initial pH 2, and the pH did not vary during the period of photocatalytic reaction. The photocatalytic oxidation of propoxur using TiO₂ suspensions as the photocatalyst was reaction‐controlled as indicated by the activation energy.     

Oyster shell as substitute for aggregate in mortar.

Enormous amounts of oyster shell waste have been illegally disposed of at oyster farm sites along the southern coast of Korea. In this study to evaluate the possibility of recycling this waste for use as a construction material, the mechanical characteristics of pulverized oyster shell were investigated in terms of its potential utilization as a substitute for the aggregates used in mortar. The unconfined compressive strengths of various soil mortar specimens, with varying blending ratios of cement, water and oyster shell, were evaluated by performing unconfined compression tests, and the results were compared with the strengths of normal cement mortar made with sand. In addition, the effect of organic chemicals on the hardening of concrete was evaluated by preparing ethyl-benzene-mixed mortar specimens. The long-term strength improvement resulting from the addition of fly ash was also examined by performing unconfined compression tests on specimens with fly-ash content. There was no significant reduction in the compressive strength of the mortars containing small oyster shell particles instead of sand. From these test data, the possible application of oyster shells in construction materials could be verified, and the change in the strength parameters according to the presence of organic compounds was also evaluated.     

Assessment of Future Climate Change Impact on Water Quality of Chungju Lake,South Korea,Using WASP Coupled with SWAT

This study is to evaluate the future potential impact of climate change on the water quality of Chungju Lake using the Water Quality Analysis Simulation Program (WASP). The lake has a storage capacity of 2.75 Gm³, maximum water surface of 65.7 km², and forest‐dominant watershed of 6,642 km². The impact on the lake from the watershed was evaluated by the Soil and Water Assessment Tool (SWAT). The WASP and SWAT were calibrated and validated using the monthly water temperatures from 1998 to 2003, lake water quality data (dissolved oxygen, total nitrogen [T‐N], total phosphorus [T‐P], and chlorophyll‐a [chl‐a]) and daily dam inflow, and monthly stream water quality (sediment, T‐N, and T‐P) data. For the future climate change scenario, the MIROC3.2 HiRes A1B was downscaled for 2020s, 2050s, and 2080s using the Change Factor statistical method. The 2080s temperature and precipitation showed an increase of +4.8°C and +34.4%, respectively, based on a 2000 baseline. For the 2080s watershed T‐N and T‐P loads of up to +87.3 and +19.6%, the 2080s lake T‐N and T‐P concentrations were projected to be 4.00 and 0.030 mg/l from 2.60 and 0.016 mg/l in 2000, respectively. The 2080s chl‐a concentration in the epilimnion and the maximum were 13.97 and 52.45 μg/l compared to 8.64 and 33.48 μg/l in 2000, respectively. The results show that the Chungju Lake will change from its mesotrophic state of 2000 to a eutrophic state by T‐P in the 2020s and by chl‐a in the 2080s. Editor's note: This paper is part of a featured series on Korean Hydrology. The series addresses the need for a new paradigm of river and watershed management for Korea due to climate and land use changes.     

NUMERICAL MODELING OF SOLUTE TRANSPORT PATTERNS IN THE DAMMAM AQUIFER1

ABSTRACT: During the past two decades, the Kingdom of Saudi Arabia has witnessed rapid development in its agricultural and urban areas, which has resulted in greater reliance being placed on its ground water aquifers. The intensive development, particularly along the coastline and in the absence of adequate replenishment sources, has led to major deterioration in the quality and quantity of ground water resources. A numerical model of the Dammam aquifer in the Eastern Province is developed and used to predict the extent of the saline intrusion in the aquifer. The types of stresses effecting the solute transport were identified and remedial measures were suggested. (KEY TERMS: numerical modeling; Saudi Arabia; aquifer; modeling/statistics.)