Carbonaceous resin capsule for vapor-phase monitoring of volatile hydrocarbons in soil: partitioning and kinetic model verification

The resin capsule system (RCS) was tested as a means of providing data on the presence and forms of volatile hydrocarbons. Results indicated that resin capsules provided data showing sensitivity to soil variables (texture and moisture content) and time. The objectives of this paper are to evaluate the RCS methodology and to determine whether carbonaceous resin capsules provide results that can be described by fundamental chemical partitioning and kinetic principles. Findings revealed a significant relationship between quantities of benzene, toluene, ethylbenzene, and xylene adsorbed on the capsule and quantities partitioned into the vapor phase. Kinetic evaluation indicated that the vapor adsorption by the resin capsule is regulated by diffusion processes. No verification of rate-limiting processes was possible due to limitations imposed by the experimental design, but it appears that during early stages, adsorption rate was limited by vapor diffusion through the soil. The resin capsule data also reflected differences that would be expected due to properties of the organic liquids present. These results provide further evidence that the RCS could be developed to suggest direct in situ monitoring to reveal quantities and nature of organic substances in soils.     

Degradation of ammonium dinitramide (ADN) in digested sewage sludge under strict anaerobic conditions

The biodegradation of one popular nitramine energetics, ammonium dinitramide (ADN) by mixture of denitrifying bacterial species was investigated. ADN was observed to be effectively mineralized in the anaerobic mixed culture. The initial ADN concentration of 250 mg/L was reduced to non‐detectable levels (> 99% removal efficiency) in 5 days of incubation under anaerobic conditions. Final products generated from anaerobic degradation of nitramine energetics by anaerobic metabolism were NH₄ ⁺, CH₄, and CO₂ that were released to the environment with the denitrifiers’ growth. In addition, it was found that the activity of denitrifiers was inhibited by high concentration of ammonia generated through the degradation reactions of energetic nitrites.     

Structural effect of the in situ generated titania on its ability to oxidize and capture the gas-phase elemental mercury

Structural effect of the in situ generated TiO(2) sorbent particle was examined for its ability to capture elemental mercury under UV irradiation in a simulated combustion flue gas. Titania particles were prepared by thermal gas-phase oxidation of Titanium (IV) isopropoxide (TTIP) using a high temperature electric furnace reactor. The structural characteristics of the in situ generated TiO(2) at various synthesis temperatures were investigated; size distribution and the geometric mean diameter were measured using a scanning mobility particle sizer, while fractal dimension and radius of gyration were evaluated from the transmission electron microscopy images. Results from the Hg(0) capture experiment show that with increasing titania synthesis temperature, the overall aggregate size increases and the morphology becomes more open-structured to gas-phase Hg(0) and UV light, resulting in the improved mercury removal capability.     

Synthesis of mesoporous magnesium oxide: Its application to CO2 chemisorption

Mesoporous magnesium oxide (MgO) was synthesized using mesoporous carbon CMK-3 obtained from mesoporous SBA-15 as exotemplate. P123 was used as the structure-directing template and rice husk ash (RHA) as the silica source for the synthesis of SBA-15, which was subsequently treated with sucrose and sulphuric acid to obtain mesoporous carbon (CMK-3). X-ray powder diffraction (XRD) results and the type-IV adsorption isotherm with H1 hysteresis obtained by N₂ adsorption/desorption study for SBA-15, CMK-3 and mesoporous MgO suggests its resemblance with materials synthesized using conventional silica sources. Mesoporous MgO was subjected for CO₂ adsorption study in TGA; adsorption was 8 and 10 wt% at 25 and 100 °C, respectively. Finally, mesoporous MgO is selective to CO₂ gas, thermally stable and regenerable. Thus, this study contributes a better route to enhance CO₂ gas adsorption and use ecological waste rice husk for the synthesis of such efficient mesoporous materials.     

Significance of anion exchange in pentachlorophenol sorption by variable-charge soils

Sorption data and subsequent predictive models for evaluating acidic pesticide behavior on variable-charge soils are needed to improve pesticide management and environmental stewardship. Previous work demonstrated that sorption of pentachlorophenol (PCP), a model organic acid, was adequately modeled by accounting for pH-and pKa-dependent chemical speciation and using two organic carbon-normalized sorption coefficients; one each for the neutral and anionic species. Such models do not account for organic anion interaction to positively charged surface sites, which can be significant for variable-charge minerals present in weathered soils typical of tropical and subtropical regions. The role of anion exchange in sorption of ionizable chemicals by variable-charge soils was assessed by measuring sorption of PCP by several variable-charge soils from aqueous solutions of CaCl2, CaSO4, Ca(H2PO4)2 as a function of pH. Differences in sorption from phosphate and chloride electrolyte solutions were attributed to pentachlorophenolate interactions with anion exchange sites. Suppression of PCP sorption by phosphate ranged from negligible in a soil with essentially no positively charge sites, as measured by negligible anion exchange capacity, to as much as 69% for variable-charge soils. Pentachlorophenolate exchange correlated well with the ratio of pH-dependent anion exchange capacity to net surface charge. Sorption reversibility of PCP by both CaCl2 and Ca(H2PO4)2 solutions was also demonstrated. Results for PCP clearly demonstrate that sorption to anion exchange sites in variable-charge soils should be considered in assessing pesticide mobility and that phosphate fertilizer application may increase the mobility of acidic pesticides.     

Effects of carbon nanotube and biochar on bioavailability of Pb,Cu and Sb in multi-metal contaminated soil

This study examined the effects of carbon nanotube and biochar on the bioavailability of Pb, Cu and Sb in the shooting range soils for developing low-cost remediation technology. Commercially available multi-walled carbon nanotube (MWCNT) and biochar pyrolyzed from soybean stover at 300 °C (BC) at 0.5, 1 and 2.5% (w w^?1) were used to remediate the contaminated soil in an incubation experiment. Both DTPA (bioavailable) and TCLP (leaching) extraction procedures were used to compare the metal/loid availability and leaching by the amendments in soil. The addition of BC was more effective in immobilizing mobile Pb and Cu in the soil than that in MWCNT. The BC reduced the concentrations of Pb and Cu in the soil by 17.6 and 16.2%, respectively. However, both MWCNTs and BC increased Sb bioavailability by 1.4-fold and 1.6-fold, respectively, in DTPA extraction, compared to the control. The toxicity characteristic leaching procedure (TCLP) test showed that the leachability of Pb in the soil amended with 2.5% MWCNT was 1.3-fold higher than that the unamended soil, whereas the BC at 2.5% decreased the TCLP-extractable Pb by 19.2%. Precipitation and adsorption via electrostatic and π–π electron donor–acceptor interactions were postulated to be involved in the interactions of Pb and Cu with surfaces of the BC in the amended soils, whereas ion exchange mechanisms might be involved in the immobilization of Cu in the MWCNT-amended soils. The application of BC derived from soybean stover can be a low-cost technology for simultaneously immobilizing bioavailable Pb and Cu in the shooting range soils; however, neither of amendments was effective in Sb immobilization.     

Effect of biosolid hydrochar on toxicity to earthworms and brine shrimp

The hydrothermal carbonization of sewage sludge has been studied as an alternative technique for the conversion of sewage sludge into value-added products, such as soil amendments. We tested the toxicity of biosolid hydrochar (Sewchar) to earthworms. Additionally, the toxicity of Sewchar process water filtrate with and without pH adjustment was assessed, using brine shrimps as a model organism. For a Sewchar application of 40 Mg ha^?1, the earthworms significantly preferred the side of the vessel with the reference soil (control) over side of the vessel with the Sewchar treatments. There was no acute toxicity of Sewchar to earthworms within the studied concentration range (up to 80 Mg ha^?1). Regarding the Sewchar process water filtrate, the median lethal concentration (LC50) to the shrimps was 8.1% for the treatments in which the pH was not adjusted and 54.8% for the treatments in which the pH was adjusted to 8.5. The lethality to the shrimps significantly increased as the amount of Sewchar process water filtrate increased. In the future, specific toxic substances in Sewchar and its process water filtrate, as well as their interactions with soil properties and their impacts on organisms, should be elucidated. Additionally, it should be identified whether the amount of the toxic compounds satisfies the corresponding legal requirements for the safe application of Sewchar and its process water filtrate.     

Impact of natural and calcined starfish (<Emphasis Type="Italic">Asterina pectinifera</Emphasis>) on the stabilization of Pb,Zn and As in contaminated agricultural soil

Metal stabilization using soil amendments is an extensively applied, economically viable and environmentally friendly remediation technique. The stabilization of Pb, Zn and As in contaminated soils was evaluated using natural starfish (NSF) and calcined starfish (CSF) wastes at different application rates (0, 2.5, 5.0 and 10.0 wt%). An incubation study was conducted over 14 months, and the efficiency of stabilization for Pb, Zn and As in soil was evaluated by the toxicity characteristic leaching procedure (TCLP) test. The TCLP-extractable Pb was reduced by 76.3–100 and 91.2–100 % in soil treated with NSF and CSF, respectively. The TCLP-extractable Zn was also reduced by 89.8–100 and 93.2–100 % in soil treated with NSF and CSF, respectively. These reductions could be associated with the increased metal adsorption and the formation of insoluble metal precipitates due to increased soil pH following application of the amendments. However, the TCLP-extractable As was increased in the soil treated with NSF, possibly due to the competitive adsorption of phosphorous. In contrast, the TCLP-extractable As in the 10 % CSF treatment was not detectable because insoluble Ca–As compounds might be formed at high pH values. Thermodynamic modeling by visual MINTEQ predicted the formation of ettringite (Ca₆Al₂(SO₄)₃(OH)₁₂·26H₂O) and portlandite (Ca(OH)₂) in the 10 % CSF-treated soil, while SEM–EDS analysis confirmed the needle-like structure of ettringite in which Pb was incorporated and stabilized in the 10 % CSF treatment.     

Reducing security vulnerabilities for critical infrastructure

In this paper, we show the need for improved Process Control System (PCS) security, and describe some of the promising research areas in PCS security. One implementation of PCS in critical infrastructure and factory automation is a supervisory, control, and data acquisition (SCADA) system, a real-time industrial process control system which centrally monitors and controls remote and/or local processes utilizing plant, equipment, or devices (such as switches, valves, pumps, relays, etc.) while collecting and logging field data. Current SCADA systems are distributed, networked, and dependent on open protocols for the internet, which are exposed to remote cyber terrorism. They are particularly vulnerable to unauthorized access. We give some examples of SCADA processes with natural gas control systems in USA and the Ubiquitous Sensor Network (USN) in Korea. We also examine a representative vulnerability and corresponding measures for security, and present an example of concrete measures for the security of mass transportation as a critical infrastructure.