A study was undertaken using urban soils in Detroit, MI and reference materials (cerussite, anglesite, pyromorphite, apatite, goethite, calcite, pyrolusite, and peat) to determine which geochemical forms of Pb measured by sequential extraction analysis are bioaccessible. The results suggest that the water soluble (Pb-fulvic acid complexes), exchangeable, and part of the carbonateoccluded fractions are bioaccessible. The Fe oxideoccluded, Mn oxide-occluded, and higher molecular weight component of the organically bound fraction are not bioaccessible. Sequential extraction predicts the presence of detectable levels of bioaccessible Pb in the rhizosphere when the summed total is ≥90 mg kg-1 and labile Pb is ≥30 mg kg-1. Cerussite (paint-Pb) and anglesite (auto-Pb), recovered mainly in the carbonateoccluded fraction, may cause an overestimation of calcite-Pb. Pyromorphite and apatite Pb (bone) may cause an overestimation of Fe oxide-occluded Pb. © Springer Science+Business Media Dordrecht 2013.

A special sequential extraction (SE) procedure for mercury (Hg) was conducted to determine biogeochemical fractions of Hg and their controlling factors in four contaminated soil profiles located in two distinct floodplain ecosystems which differ in their industrial histories and thus in their Hg loads. The first study area is located at the Wupper River (Western Germany) and the soil profiles reveal sum of Hg (Hgₛᵤₘ) concentrations up to 48 ppm. The second study area is located at the Saale River (Eastern Germany) and the soil profiles have Hgₛᵤₘ concentrations up to 4.3 ppm. The majority of Hg was found in fraction IV (FIV, Hg⁰) for both study areas, indicating its anthropogenic origin. Moreover, we have detected Hg in fraction V (FV) and in fraction III (FIII). As Hg in FV is mostly associated with Hg sulfides being formed under reducing conditions, it indicates reduction processes which usually occurred during flooding. Mercury in FIII (organo-chelated Hg) exhibits a moderate mobility and a high methylation potential. Between Hg in FIII and hot-water-extractable carbon (CHWE) as a measure of easy degradable, labile soil organic matter, we found a significant correlation. Sum of Hg seem to have a high affinity to organic carbon (Cₒᵣg). The concentrations of Hg in the mobile and exchangeable fractions FI and FII were low. Moreover, the significant positive correlation between iron (Fe) and Hg in FIV indicate an interaction between Hg and Fe. The majority of the Hg in our soils is considered to be relatively immobile. However, since the formation of more mobile Hg species via oxidation or methylation might occur in floodplain soils, the low Hg concentrations in mobile fractions should not be underestimated due to their high mobility and potential plant availability.

Volatile organic compounds (VOCs) are ubiquitous in marine areas in many parts of the world. Effect of environmental factors (light intensity, temperature, oxygen levels, and presence of sensitizer) on photodegradation of VOCs present in water-soluble fraction of Kuwait crude oil was investigated in laboratory conditions. The results showed that all factors investigated had significant effects on photo degradation rates. Higher temperatures produced faster degradation rates. At 15 °C, most of the volatile optimally degraded when light intensity was set at 750 W/m². Oxygen level of 7 ppm and presence of sensitizer was also required. Oxygen level of 4 ppm and light intensity of 500 W/m² and presence of a sensitizer produced optimal degradation rates for most of the compounds at 30 °C. At 40 °C, deoxygenated water-soluble fraction and light intensity of 500 W/m² produced the fastest degradation for many of the volatile compounds. Linear regression indicated that for most of the compounds temperature had the greatest effect on degradation rates.

A titanium mesostructure was synthesized, and its surface was subsequently modified by adsorbing phosphate. The modified structure was later investigated for photocatalytic activity against the organic contaminant 2,4,6-trichlorophenol with UV irradiation. This research found that the effects of calcination temperature, phosphate concentration for surface modification, amine grafting as a function, and initial pH condition contributed to the enhanced degradation rate of the chlorinated phenol. The results of this study demonstrated an increased photocatalytic degradation rate for 2,4,6-trichlorophenol under the following conditions: (1) titanium mesostructure calcined at 600 °C; (2) adsorption from a 100 mg/L as PO₄-P solution; (3) an amine-functionalized titanium mesostructure synthesized with the molar ration of 1:0.5 (titanium mesostructure: amine group); and (4) acidic condition (pH 4) to promote efficient adsorption of phosphate. This research indicates that phosphate removal and enhanced degradation of organic contaminants could be carried out simultaneously in sewage treatment.

There are growing concerns about the increasing trends of emerging micropollutants in the environment due to their potential negative impacts on natural ecosystems and humans. This has attracted attention from both governmental and non-governmental organisations worldwide. Pharmaceuticals, personal care products, and endocrine disruptors are continuously being released consciously or unconsciously into water sources due to poor regulatory frameworks especially in the developing countries. The effects of these contaminants are poorly known. They are not easily biodegradable and have become an environmental nuisance and public health issue. This has heightened the risk of exposure to their deleterious effects in such countries where the majority of the population are still struggling to have access to good quality drinking water supplies and better sanitation. With the rising fear of short- and long-term impacts of the ever-increasing number of persistent recalcitrant organic compounds accumulating in the environment, their removal is gradually becoming an issue to the water treatment industry. Hence, there is a need to develop functional techniques for the management of water contaminated by these emerging contaminants so as to increase the availability and access to safe and good-quality drinking water. We conducted a narrative review on these emerging micropollutants and examined their various documented sources, effects, as well as recent techniques for their effective removal. This becomes necessary due to the increasing occurrence of these pollutants in the aquatic and terrestrial environment. These levels are expected to further increase in the coming years as a consequence of the ever-increasing population density which undoubtedly characterizes developing economies. Our findings show that the present reported treatment techniques in the literature such as biological oxidation/biodegradation, coagulation/flocculation, ozonation, electrodialysis, reverse osmosis, sedimentation, filtration, and activated carbon were not designed for removal of these newly identified contaminants, and as such, the techniques are not sufficient and unable to completely degrade the compounds. We therefore recommended the need for concerted efforts to develop better techniques, especially combined advanced oxidative methods to address the shortcomings of and growing challenge to current practices.

Copper(II) biosorption in the presence of complexing agents (CA) onto orange peel (OP) and chemically modified OP (OPᴴ⁺, OPᴺᵃ⁺, and OP⁽ᴺᵃ⁺⁾⁽ᴴ⁺⁾) was studied. The study of the effect of pH showed that OPᴴ⁺ presented a copper(II) uptake similar to OP in the pH range 1.5–6.0, whereas OPᴺᵃ⁺ and OP⁽ᴺᵃ⁺⁾⁽ᴴ⁺⁾ showed the highest copper(II) uptake in the pH range 4–6. Copper(II) sorption isotherms were obtained with Cu(II)/CA mass ratios of 1:0 and 1:2 at pH 5. The Sips model fitted best the isotherms without CA, whereas the Freundlich and Brunauer-Emmett-Teller (BET) models fitted best the isotherms in the presence of ethylenediaminetetraacetic acid (EDTA) and citrate, respectively. The CA reduced the copper(II) uptake due to the presence of copper(II)-chelated species, though the interference of citrate was less important than that of EDTA. OPᴺᵃ⁺ and OP⁽ᴺᵃ⁺⁾⁽ᴴ⁺⁾ showed a higher copper(II) uptake capacity than OP, also in the presence of CA in solution. Copper(II) sorption mechanisms were studied using energy-dispersive X-ray and Fourier transform infrared spectroscopy and revealed ion exchange as one of the mechanisms. Biosorption reversibility and biosorbent reuse were evaluated in sorption/desorption cycles. Reversibility of copper(II) sorption was obtained (90 % metal recovery), though an important reduction of the metal uptake was observed in the second cycle.

Photoreactivation is considered to be one of the principal disadvantages of the application of ultraviolet disinfection, but knowledge about the photoreactivation potential is limited since few studies to model photoreactivation have been carried out. In order to develop a model for the prediction of the photoreactivation potential, the photoreactivation of Escherichia coli, fecal coliforms, and total coliforms in the tertiary effluent of a wastewater treatment plant was investigated using traditional plate count methods in this study. The tested bacteria were exposed to various UV doses (5-80 mJ/cm2) with a low-pressure UV-collimated beam apparatus and then put under sunlight lamp to experience photoreactivation for up to 72 h. All tested bacteria underwent photoreactivation with a similar trend. When the UV dose increased from 5 to 20 mJ/cm2, the maximum reactivation value of E. coli decreased from 105 to 10 CFU/mL over 8 h, and the reactivation rate decreased from 3.6 to 3.0 × 10-4/h. Based on the photoreactivation results, an exponential model was developed to predict the possible maximum photoreactivation level (N m = αD - β N 0). This simple photoreactivation potential prediction model contains only two variables (UV dose and initial bacterial count), with two constants related to the microorganism species. This model can be easily generalized and is helpful for the optimum design of UV disinfection systems. © 2013 Springer Science+Business Media Dordrecht.

Poised to gain insight into nitrate adsorption and removal processes from water through employment of modified surfaces, a well-defined inorganic manganese species was used in connection with hydrophobic mesoporous silica. To this end, the surface of hydrophobic mesoporous silica was modified by coating silica with a manganese oxychloride (Mn₈O₁₀Cl₃) nanoparticle layer. A sol–gel method was utilized for the synthesis of hydrophobic silica, using tetraethyl orthosilicate–methyl triethoxysilane (TEOS–MTES) as precursors. Subsequent coating with Mn₈O₁₀Cl₃ took place by mixing MnCl₂ and NaOH with hydrophobic silica. Physicochemical characterization of the Mn₈O₁₀Cl₃-coated silica was carried out by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and N₂ sorption. The achieved surface modification reduced remarkably the specific surface area by 80.7 % and influenced the ability of nitrates to adsorb on Mn-modified silica. Nitrate adsorption kinetics on Mn₈O₁₀Cl₃-coated silica was studied by a batch reactor. Process parameters including pH, temperature, and initial nitrate concentration were examined thoroughly. The experimental adsorption data were fitted satisfactorily through Langmuir isotherm equations and were found to be well-represented by a pseudo-second-order kinetic model. The collective data emphasize the significance of well-defined inorganic manganese phases, coating hydrophobic silica, in optimally influencing water decontamination from pollutant nitrates.

The present paper examines the phosphate adsorption from aqueous solutions onto goethite, bentonite, and bentonite–goethite system. The properties of the materials were studied by X-ray diffraction (XRD), attenuated total reflectance (ATR), and NMR spectra and by the measurement of the specific surface area, the point of zero charge (p.z.c.) and the pore-specific volume. ATR and NMR spectra of bentonite and bentonite–goethite system show peaks which correspond to tetrahedrally and octahedrally coordinated Al. The specific surface area of the system differs according to the appropriate method used, while system’s p.z.c. is higher than bentonite and lower than goethite. The pore-specific volume of bentonite–goethite system is higher than that of bentonite or goethite. According to XRD spectrum of bentonite–goethite system, goethite coats the (001) spacing of bentonite while the coating of (010) plane of bentonite is limited. The crystallinity of the system decreases and the negative permanent charge increases. Phosphate adsorption experiments took place at different pH (3.8–9.0) and concentrations (40.3–443.5 μmol L⁻¹) and constant capacitance model was applied to describe adsorption. A ligand exchange mechanism characterizes the model because the charge is divided among adsorbate and adsorbent. The constant capacitance model describes the adsorption mechanism in all examined pH. This model can be utilized in such systems using the surface protonation-dissociation constant of goethite and showing the exact shape of the adsorption isotherms for different pH values. Τhe produced low-cost bentonite–goethite system presents the highest adsorption of P per kilogram of goethite.

This study examined the potential for regrowth of Escherichia coli in laboratory-incubated microcosms spiked with ultraviolet (UV)-disinfected sewage effluent and extracts derived from turfgrass or leaf litter. A second part of the study examined the potential of nutrients for predicting E. coli in two urban streams with point source effluent. Microcosms containing effluent and vegetation extracts were incubated for 72 h, samples were withdrawn over six time periods for measurement of E. coli. Streams were sampled every 2 weeks and E. coli and nutrients measured. E. coli counts in the microcosms exceeded the Texas state secondary contact recreation standard for surface water quality within 12 h for the turfgrass and within 18 h for leaf litter extracts. Univariate analysis of variance found that the interaction between vegetation extract source and concentration was more important than source of vegetation or concentration of extract alone. In the two streams sampled downstream of a point source effluent discharge, between 82 and 92 % of the variance in annual E. coli during high stream flow and between 55 and 57 % of the variance in annual E. coli during low stream flow was described by stream water-dissolved organic carbon (DOC) and dissolved organic nitrogen (DON), NH₄-N, NO₃-N, or PO₄-P. Once effluent is discharged to surface water, particularly during high flow conditions, DOC and DON derived from the landscape and nitrogen and PO₄-P derived from the effluent will provide ideal conditions for E. coli regrowth in surface waters downstream of the point source discharge.