Ali Shareef

Biodegradation of three selected benzotriazoles under aerobic and anaerobic conditions

We examined the biodegradability of three benzotriazoles (benzotriazole: BT, 5-methylbenzotriazole: 5-TTri and 5-chlorobenzotriazole: CBT) under aerobic and anaerobic (nitrate, sulfate, and Fe (III) reducing) conditions. All three benzotriazoles were degraded by microorganisms under aerobic and anaerobic conditions. Both the biodegradation efficiency and biodegradation products were dependent on the predominant terminal electron-accepting condition. Among the redox conditions studied, the shortest biodegradation half lives for BT and 5-TTri were 114 days and 14 days, respectively, under aerobic condition. The shortest half-life for CBT was 26 days under Fe (III) reducing condition. The longest biodegradation half lives for BT and CBT were 315 days and 96 days, respectively, under sulfate reducing condition, while that of 5-TTri was 128 days under nitrate reducing condition. These results suggest that aerobic biodegradation is the dominant natural attenuation mechanism for BT and 5-TTri, while the most favorable process for CBT was anaerobic biodegradation. This study demonstrated that different predominant terminal electron-acceptors present in natural environment play a key role on the biodegradation of BT, 5-TTri and CBT, leading to specific biodegradability. This could have significant implications on in-situ biodegradation of the selected benzotriazoles in aerobic and anaerobic waters, soils and sediments.

Biodegradation of three selected benzotriazoles in aquifer materials under aerobic and anaerobic conditions

We investigated the biodegradation of three selected benzotriazoles (BTs), namely benzotriazole (BT), 5-methyl-benzotriazole (5-TTri) and 5-chloro-benzotriazole (CBT), in aquifer materials. Biodegradation experiments were conducted in microcosms with fresh groundwater and aquifer sediment materials under aerobic and anaerobic (nitrate, sulfate, and Fe (III) reducing) conditions. All three BTs were degraded by microorganisms in aquifer materials under aerobic and anaerobic conditions. Under aerobic conditions, BT and 5-TTri were found to be degraded fastest with their half-lives of 43 days and 31 days, respectively, among the redox conditions used. Under anaerobic conditions, CBT was found to be degraded better with its half-life of 21 days under nitrate reducing conditions than under aerobic conditions with its half-life of 47 days. The two BT derivatives 5-TTri and CBT could be biotransformed into BT via demethylation and dechlorination reactions, respectively.

Selected personal care products and endocrine disruptors in biosolids: an Australia-wide survey.

Personal care products (PCPs) and endocrine disrupting compounds (EDCs) are groups of organic contaminants that have been detected in biosolids around the world. There is a shortage of data on these types on compounds in Australian biosolids, making it difficult to gain an understanding of their potential risks in the environment following land application. In this study, 14 biosolids samples were collected from 13 Australian wastewater treatment plants (WWTPs) to determine concentrations of eight compounds that are PCPs and/or EDCs: 4-t-octylphenol (4tOP), 4-nonylphenol (4NP), triclosan (TCS), bisphenol A (BPA), estrone (E1), 17β-estradiol (E2), estriol (E3) and 17α-ethinylestradiol (EE2). Concentration data were evaluated to determine if there were any differences between samples that had undergone anaerobic or aerobic treatment. The concentration data were also compared to other Australian and international data. Only 4tOP, 4NP, TCS, and BPA were detected in all samples and E1 was detected in four of the 14 samples. Their concentrations ranged from 0.05 to 3.08 mg/kg, 0.35 to 513 mg/kg, <0.01 to 11.2 mg/kg, <0.01 to 1.47 mg/kg and <45 to 370 μg/kg, respectively. The samples that were obtained from WWTPs that used predominantly anaerobic treatment showed significantly higher concentrations of the compounds than those obtained from WWTPs that used aerobic treatment. Overall, 4NP, TCS and BPA concentrations in Australian biosolids were lower than global averages (by 42%, 12% and 62%, respectively) and 4tOP concentrations were higher (by 25%), however, of these differences only that for BPA was statistically significant. The European Union limit value for NP in biosolids is 50 mg/kg, which 4 of the 14 samples in this study exceeded.

Field dissipation of 4-nonylphenol, 4-t-octylphenol, triclosan and bisphenol A following land application of biosolids

The persistence of contaminants entering the environment through land application of biosolids needs to be understood to assess the potential risks associated. This study used two biosolids treatments to examine the dissipation of four organic compounds: 4-nonylphenol, 4-t-octylphenol, bisphenol A and triclosan, under field conditions in South Australia. The pattern of dissipation was assessed to determine if a first-order or a biphasic model better described the data. The field dissipation data was compared to previously obtained laboratory degradation data. The concentrations of 4-nonylphenol, 4-t-octylphenol and bisphenol A decreased during the field study, whereas the concentration of triclosan showed no marked decrease. The time taken for 50% of the initial concentration of the compounds in the two biosolids to dissipate (DT50), based on a first-order model, was 257 and 248 d for 4-nonylphenol, 231 and 75 d for 4-t-octylphenol and 289 and 43 d for bisphenol A. These field DT50 values were 10- to 20-times longer for 4-nonylphenol and 4-t-octylphenol and 2.5-times longer for bisphenol A than DT50 values determined in the laboratory. A DT50 value could not be determined for triclosan as this compound showed no marked decrease in concentration. The biphasic model provided a significantly improved fit to the 4-t-octylphenol data in both biosolids treatments, however, for 4-nonylphenol and bisphenol A it only improved the fit for one treatment. This study shows that the use of laboratory experiments to predict field persistence of compounds in biosolids amended soils may greatly overestimate degradation rates and inaccurately predict patterns of dissipation.

Degradation of 4-nonylphenol, 4-t-octylphenol, bisphenol A and triclosan following biosolids addition to soil under laboratory conditions

Land application of biosolids is common practice in many countries, however, there are some potential risks associated with the presence of contaminants within the biosolids. This laboratory study examined the degradation of four commonly found organic compounds, 4-nonylphenol, 4-t-octylphenol, bisphenol A, and triclosan, in soil following the addition of two biosolids over 32 weeks. The pattern of degradation was assessed to determine if it followed a standard first-order decay model or if a biphasic model with a degrading and a recalcitrant fraction better described the data. The time taken for the initial concentrations to decrease by 50% (DT50), based on a first-order model, was 12-25 d for 4-nonylphenol, 10-14 d for 4-t-octylphenol, 18-102 d for bisphenol A, and 73-301 d for triclosan. For 4-nonylphenol, bisphenol A and triclosan, the biphasic model fitted the degradation data better than the first-order model, indicating the presence of a degrading fraction and a non-degrading recalcitrant fraction. The recalcitrant fraction for these three compounds at the completion of the 32 week experiment was 17-21%, 24-42%, and 30-51% of the initial concentrations, respectively. For 4-t-octylphenol, the first-order model was sufficient in explaining the degradation data, indicating that no recalcitrant fraction was present. This study showed that biphasic degradation occurred for some organic compounds in biosolids amended soil and that the use of standard first-order degradation models may underestimate the persistence of some organic compounds following land application of biosolids.

Photostability of the UV filter benzophenone-3 and its effect on the photodegradation of benzotriazole in water

Environmental context The environmental fate of a particular contaminant can be influenced by the presence of other chemicals. It is shown that the photodegradation in water of benzotriazole, a common household and industrial chemical, is reduced in the presence of a sunscreen compound. Thus, contaminants such as benzotriazole may persist longer in the environment in the presence of chemicals designed to filter ultraviolet rays, such as those used in sunscreens. Abstract The presence of co-solutes (e.g. UV filters) can potentially influence the environmental fate of micropollutants. The photolysis of benzotriazole (BT, an anticorrosion agent) and benzophenone-3 (BP-3, a UV filter), as well as their interactions in aqueous solutions under UV and artificial solar light with or without added humic acid (HA) and metal ions (Cu2+ and Fe3+), has been investigated. BT was found to be photosensitive under UV irradiation, but photostable under solar light. The half-lives for the photolysis of BT were 2.8 h in pure aqueous solution and increasing to 4.5 h in the presence of BP-3 (1.0 mg L–1). BP-3 was photostable under both UV and artificial solar light. Solar radiation exposure of 50 days resulted in a small loss of BP-3 (8 %) in pure aqueous solution, and resulted in a greater loss of BP-3 (up to 31 %) at 50 mg L–1 of HA. UV irradiation of the BT solutions containing BP-3 led to formation of five photoproducts, formed mainly by N–N and N–NH bond scission, polymerisation and hydroxylation. In the case of BP-3, one major photoproduct was isolated and tentatively identified as 2,4-dimethylanisole, formed by the loss of hydroxy and benzoyl groups.

Quantitative determination of fullerene (C60) in soils by high performance liquid chromatography and accelerated solvent extraction technique

Environmental context.Due to the increasing adoption of nanotechnology, synthetic nanoparticles such as fullerenes (nC60), are likely to emerge as contaminants in aquatic and terrestrial environments. Currently, our understanding of the fate and effects of C60 in the terrestrial environment is poor and is primarily hampered by the lack of reliable quantitative analytical methods. In this paper, we describe a method for effective extraction and sensitive detection of C60 residues in soils which will facilitate environmental fate studies on nC60. Abstract.Fullerenes (e.g. C60) are emerging as environmental contaminants due to their wide range of applications, such as in optics, electronics, cosmetics and biomedicine. Residue analysis is a crucial step in understanding the fate and effects of C60 in the terrestrial environments. However, there is a lack of reliable quantitative analytical methods for extraction and analysis of C60 in soils or sediments. We developed a method for determination of C60 in soils using accelerated solvent extraction (ASE) followed by HPLC-UV detection. Separation of C60 from soil matrix interferences was achieved by gradient elution using methanol–toluene mobile phase. Mean recoveries obtained from extraction efficiency tests using six contrasting soils spiked (wet and dry tests with freeze drying of wet and aged soils before ASE) at varying concentrations of C60 ranged from 84 to 107%. The current method provides adequate sensitivity (limit of quantitation = 20 μg kg–1), and can be used for quantitative determination of C60 in soils and sediments (especially for environmental fate studies) without needing expensive HPLC-mass spectrometry.

Behaviour of fullerenes (C60) in the terrestrial environment: Potential release from biosolids-amended soils

Owing of their wide-range of commercial applications, fullerene (C60) nanoparticles, are likely to reach environments through the application of treated sludge (biosolids) from wastewater treatment plants to soils. We examined the release behaviour of C60 from contaminated biosolids added to soils with varying physicochemical characteristics. Incubation studies were carried out in the dark for up to 24 weeks, by adding biosolids spiked (1.5mg/kg) with three forms of C60 (suspended in water, in humic acid, and precipitated/particulate) to six contrasting soils. Leaching of different biosolids+soil systems showed that only small fractions of C60 (<5% of applied amount) were released, depending on incubation time and soil properties (particularly dissolved organic carbon content). Release of C60 from unamended soils was greater (at least twice as much) than from biosolids-amended soils. The form of C60 used to spike the biosolids had no significant effect on the release of C60 from the different systems. Contact time of C60 in these systems only slightly increased the apparent release up to 8 weeks, followed by a decrease to 24 weeks. Mass balance analysis at the completion of the experiment revealed that 20-60% of the initial C60 applied could not be accounted for in these systems; the reasons for this are discussed.

Biodegradation of the ultraviolet filter benzophenone‐3 under different redox conditions

Biodegradation of the ultraviolet (UV) filter benzophenone-3 (BP-3) was investigated in the laboratory to understand its behavior and fate under oxic and anoxic (nitrate, sulfate, and Fe [III]-reducing) conditions. Biodegradation experiments were conducted in microcosms with 10% of activated sludge and digested sludge under oxic and anoxic conditions, respectively. Benzophenone-3 was well degraded by microorganisms under each redox condition. Under the redox conditions studied, the biodegradation half-life for BP-3 had the following order: oxic (10.7 d) > nitrate-reducing (8.7 d) > Fe (III)-reducing (5.1 d) > sulfate-reducing (4.3 d) ≥ anoxic unamended (4.2 d). The results suggest that anaerobic biodegradation is a more favorable attenuation mechanism for BP-3. Biodegradation of BP-3 produced two products, 4-cresol and 2,4-dihydroxybenzophenone, under oxic and anoxic conditions. Biotransformation of BP-3 to 2,4-dihydroxybenzophenone by way of demethylation of the methoxy substituent (O-demethylation) occurred in cultures under each redox condition. The further biotransformation of 2,4-dihydroxybenzophenone to 4-cresol was inhibited under oxic, nitrate-reducing, and sulfate-reducing conditions.

Photolysis of benzotriazole and formation of its polymerised photoproducts in aqueous solutions under UV irradiation

Environmental context Benzotriazole is an anti-corrosion agent that is widely applied in various industrial processes and in household products. It has been found persistent in various aquatic environments. Our investigation found that benzotriazole can be rapidly transformed under UV light to form several photoproducts. Photolysis rates decreased with increasing solution pH, whereas salinity had no significant effect. Metal species Cu2+ and Fe3+, and humic acid in aquatic environment could have inhibitory effects on the photolysis of benzotriazole. Abstract Benzotriazole (BT) is an anti-corrosion agent used widely in some industrial processes and household products, and it has been detected in surface water and ground water due to its high mobility and low biodegradability. We have investigated the photolysis of benzotriazole in aqueous solutions under UV radiation at 254 nm and the effect of pH, salinity, metal species and dissolved organic matter on the photo-transformation processes. Benzotriazole was found to undergo rapid transformation to form several photoproducts. The half-lives for the photolysis of benzotriazole ranged from 2.8 to 14.3 h in various aqueous solutions containing metal ions and dissolved organic matter. Photolysis rates decreased with increasing solution pH, whereas salinity had no significant effect. Metal species Cu2+ and Fe3+, and especially humic acid had inhibitory effects on the photolysis of benzotriazole under UV light irradiation at 254 nm. We propose the formation of three major photoproducts via instantaneous polymerisation of small intermediates generated during the photolysis of benzotriazole including 2,6-diethylaniline, phenazine and 1,6-dihydroxyphenazine.