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Displacement of Br− and P22 in a Wetland Environment
2015
Vidales-Contreras, Juan A. | Rodríguez Fuentes, Humberto | Luna-Maldonado, Alejandro I. | Hernandez-Escareño, Jesus J.
Relative displacement of bromide (Br⁻) and coliphage P22 was analyzed in surface water and vadose zone solution from a 3-ha surface flow constructed wetland. In the vadose zone, water samples at 0.3-, 0.76-, 1.5-, and 3-m depth were collected to quantify Br⁻ and P22 simultaneously added into the wetland influent for a transport study. When P22 was detected, Br⁻ arrived earlier to the monitoring depths than the phage suggesting that preferential flow facilitated P22 displacement in the vadose zone. Concentrations for both tracers indicated that bacteriophage removal through the vadose zone profile was exceeding 99.21 % of the peak concentration observed in surface water samples. For transport parameter estimation, the temporal moment method (MOM) was used to calculate convective velocity (v) and longitudinal dispersion coefficient (D) from the outlet Br⁻ breakthrough curve. The transport parameters were estimated to be 55.7 m day⁻¹ and 1652 m² day⁻¹ for v and D, respectively. For P22 simulation, a first-order removal coefficient of 0.3 day⁻¹ (R ² = 0.943) was assessed. The observed results suggest that this method can be applied for solute transport simulation in constructed wetlands.
Show more [+] Less [-]Influence of physicochemical and chemical parameters on polybrominated diphenyl ethers in selected landfill leachates, sediments and river sediments from Gauteng, South Africa
2015
Olukunle, O. I. | Sibiya, Innocentia Velaphi | Okonkwo, O. J. | Odusanya, A. O.
Polybrominated diphenyl ethers (PBDEs) are known to be persistent, endocrine disruptors and bioaccumulative and can cause adverse health effects in animals and humans. In this study, river and landfill sediment samples were collected from selected rivers and municipal solid waste landfill (MSWL) sites across Gauteng Province in South Africa to determine the levels of common PBDEs (BDE-17, BDE-47, BDE-99, BDE-100, BDE-153, BDE-154, BDE-183 and BDE-209). The mean and median concentrations of Σ₈ PBDEs from river sediment samples was 2.4 and 0.4 ng g⁻¹, respectively, and a range of 0.8–114 ng g⁻¹. The highest concentration of Σ₈ PBDEs (43.6 ng g⁻¹) was observed at Jukskei River with more than two orders of magnitude greater than the rest. The observed total PBDE concentrations in landfill sediment and leachate samples ranged from 0.8 to 8.4 ng g⁻¹ and 127–3,702 pg L⁻¹ for the two matrices. BDE-209 was predominantly detected in most of the sediment samples. Two of the MSWLs which are lined with geomembranes gave the highest concentrations of ∑₇ PBDEs (2,678 and 3,702 pg L⁻¹). Correlation values for ∑₇ PBDEs versus Co (r = 0.65), Cu (r = 0.52), Mn (r = 0.10), Mg (r = 0.76), Ca (r = 0.66) and Ni (r = 0.77) with a statistical significance (p < 0.05) were observed except for Na, Cr, Pb, K, Fe and Zn (p > 0.05). The observed positive correlation may suggest a possible influence of trace metals on PBDE concentrations in leachates. Furthermore, a test of relationship between major anions and PBDEs yielded positive relationship with Cl⁻ (r = 0.94, p = 0.16), F⁻ (r = 0.97, p = 0.21), Br⁻ (r = 0.6, p = 0.29) and NO₃²⁻ (r = 0.96, p = 0.08) with an insignificant statistical difference. However, evaluation of the relationship between some water quality parameters (pH, dissolved oxygen and electrical conductivity) gave negative correlation with PBDE concentrations.
Show more [+] Less [-]Winter time chemical characteristics of aerosols over the Bay of Bengal: continental influence
2015
Aryasree, S. | Nair, Prabha R. | Girach, I. A. | Jacob, Salu
As part of the Integrated Campaign for Aerosols, gases and Radiation Budget (ICARB) conducted under the Geosphere Biosphere Programme of Indian Space Research Organisation, ship-based aerosol sampling was carried out over the marine environment of Bay of Bengal (BoB) during the northern winter months of December 2008 to January 2009. About 101 aerosol samples were collected, covering the region from 3.4° to 21° N latitude and 76° to 98° E longitude—the largest area covered—including the south east (SE) BoB for the first time. These samples were subjected to gravimetric and chemical analysis and the total aerosol loading as well the mass concentration of the ionic species namely F⁻, Cl⁻, Br⁻, NO₂ ⁻, NO₃ ⁻, PO₄ ²⁻, SO₄ ²⁻, NH₄ ⁺, etc. and the metallic species, Na, Mg, Ca, K, Al, Fe, Mn, Zn, and Pb were estimated for each sample. Based on the spatial distribution of individual chemical species, the air flow pattern, and airmass back trajectory analysis, the source characteristics of aerosols for different regions of BoB were identified. Significant level of continental pollution was noticed over BoB during winter. While transport of pollution from Indo-Gangetic Plain (IGP) contributed to aerosols over north BoB, those over SE BoB were influenced by SE Asia. A quantitative study on the wind-induced production of sea salt aerosols and a case study on the species dependent effect of rainfall are also presented in this paper.
Show more [+] Less [-]Characterization of mechanisms and processes of groundwater salinization in irrigated coastal area using statistics, GIS, and hydrogeochemical investigations
2015
Bouzourra, Hazar | Bouhlila, Rachida | Elango, L. | Slama, Fairouz | Ouslati, Naceur
Coastal aquifers are at threat of salinization in most parts of the world. This study was carried out in coastal shallow aquifers of Aousja-Ghar El Melh and Kalâat el Andalous, northeastern of Tunisia with an objective to identify sources and processes of groundwater salinization. Groundwater samples were collected from 42 shallow dug wells during July and September 2007. Chemical parameters such as Na⁺, Ca²⁺, Mg²⁺, K⁺, Cl⁻, SO₄²⁻, HCO₃⁻, NO₃⁻, Br⁻, and F⁻were analyzed. The combination of hydrogeochemical, statistical, and GIS approaches was used to understand and to identify the main sources of salinization and contamination of these shallow coastal aquifers as follows: (i) water-rock interaction, (ii) evapotranspiration, (iii) saltwater is started to intrude before 1972 and it is still intruding continuously, (iv) irrigation return flow, (v) sea aerosol spray, and finally, (vi) agricultural fertilizers. During 2005/2006, the overexploitation of the renewable water resources of aquifers caused saline water intrusion. In 2007, the freshening of a brackish-saline groundwater occurred under natural recharge conditions by Ca-HCO₃meteoric freshwater. The cationic exchange processes are occurred at fresh-saline interfaces of mixtures along the hydraulic gradient. The sulfate reduction process and the neo-formation of clays minerals characterize the hypersaline coastal Sebkha environments. Evaporation tends to increase the concentrations of solutes in groundwater from the recharge areas to the discharge areas and leads to precipitate carbonate and sulfate minerals.
Show more [+] Less [-]Effect of bromide ion on the reaction pathway between hydroxyl radical and glycine
2015
Ying, Liwen | Dong, Wenbo | Yuan, Haixia | Liu, Yan | Ma, Luming
Br⁻and nitrogen-containing organic pollutants, such as amino acids, protein, etc., were often detected in water and wastewater treatment plants using advanced oxidation technologies. All these technologies have one common characteristic, that is, the removal processes involve ·OH. Therefore, it is necessary to study the different reaction pathways among ·OH, Br⁻, and amino acids. In this research, glycine was chosen as the representative of amino acids and H₂O₂was selected as ·OH precursor. Results showed that Br⁻had a shielding effect on H of α-carbon in glycine, when it was abstracted by ·OH. The main reaction pathway in the system containing Br⁻was the abstraction of H from amino group in glycine by ·OH, contributing 85 % of total abstracted H. This system had a prominent phenomenon of decarboxylation and performed as alkali production dominating. However, in the system not containing Br⁻, the main reaction pathway was the abstraction of H from α-carbon in glycine by ·OH, contributing 97 % of total abstracted H. This system performed as acid production dominating. By laser flash photolysis, the second-order rate constants of abstraction of H from both α-carbon and amino group in glycine by ·OH were obtained as (3.3 ± 0.5) × 10⁷M⁻¹·s⁻¹and (8.2 ± 0.8) × 10⁸ M⁻¹·s⁻¹, respectively. The second-order rate constants of the reaction between H₂NCH₂COO⁻, HṄCH₂COO⁻ and H₂O₂ were (1.5 ± 1.1) × 10⁷ M⁻¹·s⁻¹and (4.4 ± 0.3) × 10⁷ M⁻¹·s⁻¹, respectively. In addition, Br⁻was found to play a catalytic role in the decomposition of H₂O₂under UV radiation. The results mentioned above were significant for the application of advanced oxidation technologies for water containing both amino acids and Br⁻in water and wastewater treatment plants.
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