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Inhibitory Effect of Veterinary Antibiotics on Denitrification in Groundwater: A Microcosm Approach
Ahmad, Mahtab,Vithanage, Meththika,Kim, Kangjoo,Cho, Ju-Sik,Lee, Young Han,Joo, Young Kyoo,Lee, Sang Soo,Ok, Yong Sik Hindawi Publishing Corporation 2014 The Scientific World Journal Vol.2014 No.-
<P>Veterinary antibiotics in groundwater may affect natural microbial denitrification process. A microcosm study was conducted to evaluate the influence of sulfamethazine and chlortetracycline at different concentrations (0, 0.01, 0.1, and 1.0 mg/L) on nitrate reduction in groundwater under denitrifying condition. Decrease in nitrate removal and nitrite production was observed with the antibiotics. Maximum inhibition of nitrate removal was observed after seven days of incubation with 0.01 mg/L sulfamethazine (17.0%) and 1.0 mg/L chlortetracycline (15.4%). The nitrite production was inhibited with 1.0 mg/L sulfamethazine to 82.0% and chlortetracycline to 31.1%. The initial/final nitrate concentrations indicated that 0.01 mg/L sulfamethazine and 1.0 mg/L chlortetracycline were most effective in inhibiting activity of denitrifying bacteria in groundwater. After 12 days of incubation, the sulfamethazine biodegradation was observed whereas chlortetracycline was persistent. Sulfamethazine and chlortetracycline in groundwater could inhibit the growth and capability of naturally occurring denitrifying bacteria, thereby threatening nitrate pollution in groundwater.</P>
Ahmad, Mahtab,Soo Lee, Sang,Yang, Jae E.,Ro, Hee-Myong,Han Lee, Young,Sik Ok, Yong Elsevier 2012 Ecotoxicology and environmental safety Vol.79 No.-
<P><B>Abstract</B></P> <P>Bioavailability and bioaccessibility determine the level of metal toxicity in the soils. Inorganic soil amendments may decrease metal bioavailability and enhance soil quality. This study used mussel shell, cow bone, and biochar to reduce lead (Pb) toxicity in the highly contaminated military shooting range soil in Korea. Water-soluble and 1-M ammonium nitrate extractions, and a modified physiologically based extraction test (PBET) were performed to determine Pb bioavailability and bioaccessibility in the soil, respectively. Active C in the soil was also measured to evaluate the effects of the amendments on biological soil quality. The Pb contaminated soil was diluted in serial with uncontaminated soil for the bioassays. Seed germination and root elongation tests using lettuce (<I>Lactuca sativa</I>) showed increases in germination percentage and root length in soil treated with the amendments. Biochar was most effective and increased seed germination by 360% and root length by 189% compared to the unamended soil. Up to 20% soil dilution resulted in more than 50% seed germination. Bioavailability and bioaccessibility of Pb in the soils were decreased by 92.5% and 48.5% with mussel shell, by 84.8% and 34.5% with cow bone, and by 75.8% and 12.5% with biochar, respectively, compared to the unamended soil. We found that the Pb availability in the military shooting range soil can be reduced effectively by the tested amendments or soil dilution alternately, thereby decreasing the risk of ecotoxicity. Furthermore, the increasing active C from the amendments revitalized the soil contaminated with Pb.</P> <P><B>Highlights</B></P> <P>► Mussel shell, cow bone, and biochar decreased Pb toxicity in shooting range soil. ► Lettuce germination and root elongation were improved by the amendments. ► Soil dilution aided the amendments in reducing Pb toxicity. ► Bioavailable and bioaccessible fractions of Pb were decreased by the amendments. ► Biologically active soil carbon was increased by the amendments.</P>
Effects of Natural and Calcined Oyster Shells on Antimony Solubility in Shooting Range Soil
Ahmad, Mahtab,Moon, Deok Hyun,Wazne, Mahmoud,Kim, Hee Joung,Lee, Young Han,Ok, Yong Sik The Korean Society for Applied Biological Chemistr 2013 Applied Biological Chemistry (Appl Biol Chem) Vol.56 No.4
Waste oyster shells (OS) and calcined oyster shells (COS) were used to treat metal-contaminated shooting range soil, where antimony (Sb) leachability was assessed. Changes in soil pH induced by the amendments strongly influenced Sb leachability. Sb was immobilized by COS most likely due to calcium antimonate precipitation. This is the first time to our knowledge to report that COS can effectively immobilize Sb in the soil.
Ahmad, Mahtab,Lee, Sang Soo,Oh, Sang-Eun,Mohan, Dinesh,Moon, Deok Hyun,Lee, Young Han,Ok, Yong Sik Ecomed 2013 Environmental science and pollution research inter Vol.20 No.12
<P>Trichloroethylene (TCE) is one of the most hazardous organic pollutants in groundwater. Biochar produced from agricultural waste materials could serve as a novel carbonaceous adsorbent for removing organic contaminants from aqueous media. Biochars derived from pyrolysis of soybean stover at 300 C and 700 C (S-300 and S-700, respectively), and peanut shells at 300 C and 700 C (P-300 and P-700, respectively) were utilized as carbonaceous adsorbents to study batch aqueous TCE remediation kinetics. Different rate-based and diffusion-based kinetic models were adopted to understand the TCE adsorption mechanism on biochars. With an equilibrium time of 8-10 h, up to 69 % TCE was removed from water. Biochars produced at 700 C were more effective than those produced at 300 C. The P-700 and S-700 had lower molar H/C and O/C versus P-300 and S-300 resulting in high aromaticity and low polarity accompanying with high surface area and high adsorption capacity. The pseudo-second order and intraparticle diffusion models were well fitted to the kinetic data, thereby, indicating that chemisorption and pore diffusion were the dominating mechanisms of TCE adsorption onto biochars.</P>
Mahtab Ahmad,Adel R.A. Usman,이상수,Sung-Chul Kim,Jin-Ho Joo,양재의,옥용식 한국공업화학회 2012 Journal of Industrial and Engineering Chemistry Vol.18 No.1
Rapid industrialization in Korea has led to the discharge of heavy metals to water, posing a threat to the environment. The use of natural materials as low cost sorbents for the removal of heavy metals from aqueous solutions has recently received increasing attention. The present study was conducted to evaluate the effectiveness of eggshell and coral wastes for the removal of Pb2+, Cd2+ and Cu2+ from aqueous solutions. Batch equilibrium experiments were conducted using heavy metal solutions with waste eggshell and coral powders. Langmuir and Freundlich adsorption models were used for the mathematical description of sorption equilibrium. The maximum amounts of metals (Cu2+, Pb2+ and Cd2+) adsorbed were found to be 32.3, 22.9 and 4.47 mmol kg1 for eggshell and 6.77, 5.52 and 1.03 mmol kg1 for coral wastes,respectively. At low initial concentrations the adsorption of heavy metals onto both sorbents can be described as H-type (except for the Cd adsorption onto coral), indicating high-affinity isotherms and strong adsorbate–adsorptive interactions such as inner sphere complexes. However, the metal adsorption was described by L-type isotherm at high initial concentrations. Based on the distribution coefficient (Kd) values and the percentage of metal removed, the selectivity sequence in eggshells and coral wastes was found to be Pb2+ > Cu2+ > Cd2+. The Kd values and the percentage of metals removed were higher in eggshells than coral with its higher capacity to adsorb heavy metals. Based on the results of the present study, eggshell and coral wastes can be used for the removal of heavy metals from aqueous solutions.
Ahmad, Mahtab,Moon, Deok Hyun,Vithanage, Meththika,Koutsospyros, Agamemnon,Lee, Sang Soo,Yang, Jae E,Lee, Sung Eun,Jeon, Choong,Ok, Yong Sik John Wiley Sons, Ltd 2014 Journal of chemical technology and biotechnology Vol.89 No.1
<P><B>Abstract</B></P><P><B>BACKGROUND</B></P><P><B><I>Ambrosia trifida</I> L. (buffalo‐weed) is a ubiquitous invasive plant species in Korea, causing severe allergy problems to humans and reduction in crop yields. Converting buffalo‐weed biomass to biochar and its use as an adsorbent for the depuration of trichloroethylene (TCE) contaminated water could help resolve two existing environmental issues simultaneously</B>.</P><P><B>RESULTS</B></P><P><B>The plant biomass was converted to biochar at 300 °C (BC300) and 700 °C (BC700). The pyrolysis temperature strongly influenced the properties of resulting biochars. The higher temperature resulted in a higher degree of C‐enrichment. The loss of H‐ and O‐containing functional groups shifted the BC700 composition towards a less polar, more aromatic carbon structure evidenced by lower O/C (0.06) and H/C (0.15) values compared with those of BC300 (0.07 and 0.65, respectively). These properties of BC700 further highlighted its greater efficiency of TCE removal (88.47%) from water, compared with that of BC300 (69.07%). The TCE adsorption data was well described by the Hill isotherm model indicating the mechanism of adsorption to be cooperative interaction. Linear correlations between model parameters and biochar properties were also observed</B>.</P><P><B>CONCLUSIONS</B></P><P><B>Buffalo‐weed can be converted to value‐added biochar that can be used as an effective adsorbent for the treatment of TCE contaminated groundwater. © 2013 Society of Chemical Industry</B></P>