Screening triclocarban and its transformation products in river sediment using liquid chromatography and high resolution mass spectrometry

Occurrence and risk evaluation of endocrine-disrupting chemicals in wastewater and surface water of Lahore, Pakistan

The current study highlights the occurrence, spatial distribution, and risk assessment of 16 endocrine-disrupting chemicals (EDCs) including their transformation products (TPs) in the wastewater and surface water of Lahore, Pakistan, using solid-phase extraction followed by liquid chromatography-mass spectrometry and gas chromatography-mass spectrometry. The parent EDCs include bisphenol A (BPA), triclosan (TCS), triclocarban (TCC), estrone (E1), estradiol (E2), estriol (E3), ethinylestradiol (EE2), 4-n-octylphenol (4n-OP), and 4-n-nonylphenol (4n-NP). The TPs include two TPs each of BPA, TCC, and estrogens along with a TP of TCS. Most EDCs showed 100% detection frequency in the wastewater with highest median concentration of 1310 ng/L for E3. In the surface water, the highest median concentration was, however, observed for BPA (54.6 ng/L). Spatial variations in terms of sum of concentration due to all EDCs and their TPs were observed at different sampling points which suggest contamination due to industrial waste from nearby industrial estate. Risk evaluation in terms of risk quotient (RQ) and estradiol equivalent factor (EEQ) showed that most of EDCs and their TPs could pose high risk and estrogenicity to the surrounding environment. From the results of the current study, it is observed that the environment of Pakistan is deteriorating and is potential risk for endocrine disruption. It is, therefore, recommended to take stringent measures to make it sustainable for current as well as for future generations.

Complementary Biotransformation of Antimicrobial Triclocarban Obviously Mitigates Nitrous Oxide Emission toward Sustainable Microbial Denitrification

Sustainable nitrogen cycle is an essential biogeochemical process that ensures ecosystem safety and byproduct greenhouse gas nitrous oxide reduction. Antimicrobials are always co-occurring with anthropogenic reactive nitrogen sources. However, their impacts on the ecological safety of microbial nitrogen cycle remain poorly understood. Here, a denitrifying bacterial strain Paracoccus denitrificans PD1222 was exposed to a widespread broad-spectrum antimicrobial triclocarban (TCC) at environmental concentrations. The denitrification was hindered by TCC at 25 μg L^-1 and was completely inhibited once the TCC concentration exceeded 50 μg L^-1. Importantly, the accumulation of N₂O at 25 μg L^-1 of TCC was 813 times as much as the control group without TCC, which attributed to the significantly downregulated expression of nitrous oxide reductase and the genes related to electron transfer, iron, and sulfur metabolism under TCC stress. Interestingly, combining TCC-degrading denitrifying Ochrobactrum sp. TCC-2 with strain PD1222 promoted the denitrification process and mitigated N₂O emission by 2 orders of magnitude. We further consolidated the importance of complementary detoxification by introducing a TCC-hydrolyzing amidase gene tccA from strain TCC-2 into strain PD1222, which successfully protected strain PD1222 against the TCC stress. This study highlights an important link between TCC detoxification and sustainable denitrification and suggests a necessity to assess the ecological risks of antimicrobials in the context of climate change and ecosystem safety.

The Influence of the Chemical Composition of Natural Waters about the Triclocarban Sorption on Pristine and Irradiated MWCNTs

The influence of the chemical composition of natural waters on triclocarban (TCC) sorption on pristine and irradiated multi-walled carbon nanotubes (MWCNTs) at different temperatures was studied. Natural waters have been characterized in terms of the concentrations of cations and anions, pH, and electric conductivity. The sorption process of TCC on MWCNTs is influenced by both the chemical composition of natural waters and the variation of the temperature. The adsorption capacity of TCC on pristine and irradiated MWCNTs in the studied natural waters increased by increasing the temperature. The increase of the concentration of monovalent cations (Na+ and K+) in natural waters determined a significant decrease of the adsorption capacity of TCC on both pristine and irradiated MWCNTs while the increase of the bivalent cations (Ca2+ and Mg2+) determined an easy increase adsorption capacity. Freundlich and Langmuir models were selected to describe the steady adsorption of the TCC on the pristine and irradiated MWCNTs.

Aquatic and human health risk assessment of Humanogenic Emerging Contaminants (HECs), Phthalate Esters from the Indian Rivers

Phthalate esters (PEs) one of the widely used plasticizers, and are known for their environmental contamination and endocrine disruption. Hence, it is important to study their distribution in a riverine environment. This study was aimed to determine the Spatio-temporal trends of 16 PEs in surface water, sediment and fish from rivers in southern India, and to assess their environmental health risks. Phthalates were quantified in all matrices with the mean concentrations (∑₁₆PEs) in water, sediment and fish as 35.6 μg/L, 1.25 μg/kg and 17.0 μg/kg, respectively. The Kaveri River is highly loaded with PEs compared to the Thamiraparani and Vellar Rivers. PEs such as DBP, DEHP, DCHP and DiBP were most frequently detected in all matrices, and at elevated concentrations in the dry season. The risk quotient (RQ < 1) suggests that the health risk of PEs from river water and fish to humans is negligible. However, DBP and DEHP from the Kaveri River pose some risk to aquatic organisms (HQ > 1). DEHP from the Vellar River may pose risks to algae and crustaceans. Non-priority phthalate (DiBP) may pose risks to Kaveri and Vellar River fish. The bioaccumulation factor of DCHP and DEHP was found to be very high in Sardinella longiceps and in Centropristis striata, and also exceeded the threshold limit of 5000 suggesting that PEs in the riverine environment may pose some health concerns. This is the first study to assess the spatio-temporal distribution, riverine flux and potential ecological effects of 16 PEs from the southern Indian Rivers.

A Review on the Fate of Legacy and Alternative Antimicrobials and Their Metabolites during Wastewater and Sludge Treatment

Antimicrobial compounds are used in a broad range of personal care, consumer and healthcare products and are frequently encountered in modern life. The use of these compounds is being reexamined as their safety, effectiveness and necessity are increasingly being questioned by regulators and consumers alike. Wastewater often contains significant amounts of these chemicals, much of which ends up being released into the environment as existing wastewater and sludge treatment processes are simply not designed to treat many of these contaminants. Furthermore, many biotic and abiotic processes during wastewater treatment can generate significant quantities of potentially toxic and persistent antimicrobial metabolites and byproducts, many of which may be even more concerning than their parent antimicrobials. This review article explores the occurrence and fate of two of the most common legacy antimicrobials, triclosan and triclocarban, their metabolites/byproducts during wastewater and sludge treatment and their potential impacts on the environment. This article also explores the fate and transformation of emerging alternative antimicrobials and addresses some of the growing concerns regarding these compounds. This is becoming increasingly important as consumers and regulators alike shift away from legacy antimicrobials to alternative chemicals which may have similar environmental and human health concerns.

Fate, risk and removal of triclocarban: A critical review

The halogenated antimicrobial triclocarban (TCC) has large production and consumption over last decades. Its extensive utilization in personal care products and insufficient treatment in conventional wastewater treatment plants (WWTPs) has led to its listing as one of emerging organic contaminants (EOCs). Due to the hydrophobicity and chemical stability of TCC, it has been omnipresent detected in terrestrial and aquatic environments, and its prolonged exposure has thrown potential pernicious threat to ecosystem and human health. Considering its recalcitrance, especially under anoxic conditions, both biological and non-biological methods have been exploited for its removal. The efficiency of advanced oxidation processes was optimistic, but complete removal can rarely be realized through a single method. The biodegradation of TCC either with microbial community or pure culture is feasible but efficient bacterial degraders and the molecular mechanism of degradation need to be further explored. This review provides comprehensive information of the occurrence, potential ecological and health effects, and biological and non-biological removal of TCC, and outlines future prospects for the risk evaluation and enhanced bioremediation of TCC in various environments.

Occurrence and fate of antimicrobial triclocarban and its transformation products in municipal sludge during advanced anaerobic digestion using microwave pretreatment

This study, for the first time, investigated the impact of microwave pretreatment on the fate of the pervasive antimicrobial triclocarban (TCC) that was already present in municipal sludge, before and during advanced anaerobic digestion (AD) under thermophilic and mesophilic conditions. A range of microwave temperature (80 and 160 °C) and exposure duration (1 and 30 min) configurations were studied by employing ten bench-scale anaerobic digesters fed with mixed sludge at three different solids retention times (SRTs) including 20, 12, and 6 days. Seasonal changes influenced the levels of TCC in municipal sludge sampled from a plant employing the biological nutrient removal. Initial batch pretreatment studies showed that microwave irradiation itself can achieve TCC removal efficiencies up to 30 ± 4 and 64 ± 5% at 80 and 160 °C, respectively. The control digesters utilizing un-pretreated mixed sludge showed limited TCC removals, between 18 and 32% and 11-26% respectively, under thermophilic and mesophilic temperatures. On the other hand, the highest TCC elimination (78 ± 2%) was obtained from the thermophilic digester utilizing microwaved sludge at 160 °C for 30 min at SRT of 12 days. The non-chlorinated carbanilide (a transformation product of TCC) was detected and quantified for the first time during conventional and microwave-pretreated anaerobic sludge digestion. The formation of carbanilide in biosolids through reductive dechlorination could be an indicator of efficient and complete TCC transformation. This research demonstrated that AD coupled with microwave pretreatment can be used to reduce environmental concentrations of TCC in municipal sludge and biosolids.

Bioaugmentation of triclocarban and its dechlorinated congeners contaminated soil with functional degraders and the bacterial community response

Partial removal of haloaromatic antimicrobial triclocarban (TCC) during wastewater treatment caused the final introduction of residual TCC into soils. Bioaugmentation has been proposed for the biodegradation of TCC and its dechlorinated congeners 4,4'-dichlorocarbanilide (DCC) and carbanilide (NCC) in soil. The isolated TCC-degrading strain Ochrobactrum sp. TCC-2 and chloroanilines-degrading strain Diaphorobacter sp. LD72 were used to study the removal efficiency of TCC, DCC and NCC mixture and their chloroanilines intermediates, respectively. The potential degradation competition between TCC and its dechlorinated congeners, and the response of bacterial community during the bioremediation were also investigated. The biodegradation of DCC and TCC was significantly enhanced for soil with inoculums compared with sterilized and natural soils. Chloroanilines products could also be effectively removed. For the degradation of combined substrates in the aqueous medium, NCC had negative effect on the degradation of TCC and DCC, while TCC and DCC negatively influenced each other. The bioaugmentation with two degraders obviously changed the phylogenetic composition and function of indigenous soil microbiome. Importantly, the inoculated degraders could be maintained, suggesting their adaptability and potential application in bioaugmentation for such recalcitrant contaminants. This study offers new insights into the enhanced bioremediation of TCC and its dechlorinated congeners contaminated soils by the bioaugmentation of functional degraders and the structure and function response of the indigenous soil microbiome to the bioremediation process.

Study of aquatic life criteria and ecological risk assessment for triclocarban (TCC)

Triclocarban (TCC) is used as a broad-spectrum antimicrobial agent, the intensive detection of TCC in aquatic environments and its potential risks to aquatic organisms are concerned worldwide. In this study, 8 Chinese resident aquatic organisms from 3 phyla and 8 families were used for the toxicity tests, and four methods were employed to derive the aquatic life criteria (ALC). A criterion maximum concentration (CMC) of 1.46 μg/L and a criterion continuous concentration (CCC) of 0.21 μg/L were derived according to the USEPA guidelines. The acute predicted no effect concentrations (PNECs) derived by species sensitivity distribution (SSD) methods based on log-normal, log-logistic and Burr Type Ⅲ models were 2.64, 1.88 and 3.09 μg/L, respectively. The comparisons of ALCs derived with resident and non-resident species showed that the CMC and CCC of TCC derived with Chinese resident species could provide a sufficient protection for non-resident species. The higher toxicity of TCC on aquatic organisms was found compared with other antimicrobial agents (except for Clotrimazole) in aquatic environment. The strong positive linear correlation was observed between the TCC and TCS concentrations in aquatic environment with a correlation coefficient (R²) of 0.8104, it is of great significance in environmental monitoring and risk assessment for TCC and TCS. Finally, the ecological risk assessment showed that the TCC in Yellow River basin and Pearl River basin had higher risk with the mean potential affected fractions (PAFs) of 9.27% and 7.09%, and 22.10% and 15.00% waters may pose potential risk for 5% aquatic organisms, respectively. In general, the risk of TCC in Asian waters was higher than that in Europe and North America.

Target, Suspect and Non-Target Screening of Silylated Derivatives of Polar Compounds Based on Single Ion Monitoring GC-MS

There is growing interest in determining the unidentified peaks within a sample spectra besides the analytes of interest. Availability of reference standards and hyphenated instruments has been a key and limiting factor in the rapid determination of emerging pollutants in the environment. In this work, polar compounds were silylated and analyzed with gas chromatography mass spectrometry (GC-MS) to determine the abundant fragments within the single ion monitoring (SIM) mode and methodology. Detection limits and recoveries of the compounds were established in river water, wastewater, biosolid and sediment matrices. Then, specific types of polar compounds that are classified as emerging contaminants, pharmaceuticals and personal care products, in the environment were targeted in the Mgeni and Msunduzi Rivers. We also performed suspect and non-target analysis screening to identify several other polar compounds in these rivers. A total of 12 compounds were quantified out of approximately 50 detected emerging contaminants in the Mgeni and Msunduzi Rivers. This study is significant for Africa, where the studies of emerging contaminants are limited and not usually prioritized.

Newly Identified AhR-Active Compounds in the Sediments of an Industrial Area Using Effect-Directed Analysis

Effect-directed analysis was used to identify previously unidentified aryl hydrocarbon receptor (AhR) agonists in sediments collected from a highly industrialized area of Ulsan Bay, Korea. The specific objectives were to (i) investigate potent fractions of sediment extracts using the H4IIE-luc bioassay, (ii) determine the concentrations of known AhR agonists (polycyclic aromatic hydrocarbons (PAHs) and styrene oligomers (SOs)), (iii) identify previously unreported AhR agonists in fractions by use of GC-QTOFMS, and (iv) evaluate contributions of individual compounds to overall AhR-mediated potencies, found primarily in fractions containing aromatics with log K_ow 5-8. Greater concentrations of PAHs and SOs were also found in those fractions. On the basis of GC-QTOFMS and GC-MSD analyses, 16 candidates for AhR agonists were identified in extracts of sediments. Of these, seven compounds, including 1-methylchrysene, benzo[j]fluoranthene, 3-methylchrysene, 5-methylbenz[a]anthracene, 11H-benzo[b]fluorene, benzo[b]naphtho[2,3-d]furan, and benzo[b]naphtho[2,1-d]thiophene, exhibited significant AhR activity. Relative potency values of newly identified AhR agonists were found to be greater than or comparable to that of benzo[a]pyrene (BaP). The potency balance analysis showed that newly identified AhR agonists explained 0.07-16% of bioassay-derived BaP-EQs. These chemicals were widely distributed in industrial sediments; thus, it is of immediate importance to conduct studies on sources and potential effects of those chemicals.

Fate of Triclocarban (TCC) in aquatic and terrestrial systems and human exposure

Triclocarban (TCC) is considered as contaminant of emerging concern (CEC), and ranked in the top 10 CEC occurrence. TCC is a high production volume synthetic chemical used extensively in various personal care products. This chemical will be released into the environment via incomplete wastewater treatment and untreated wastewater discharge. TCC and its transformation products (4,4'-dichlorocarbilide (DCC),1-(3-chlorophenyl)-3-phenylurea (MCC) and carbanilide (NCC),2'OH-TCC, 3'OH-TCC) were detected in the environmental matrices. Sediment organic carbon will influence TCC concentrations in suspended and bed sediments. TCC is an antimicrobial agent and also emerging endocrine disruptor that can cause immune dysfunction and affect human reproductive outcomes. Furthermore, TCC alters the expression of proteins related to binding and metabolism, skeletal muscle development and function, nervous system development and immune response. TCC has potential health risks in wildlife and humans. Several animal studies illustrate that it can cause various adverse effects, which can be monitored by antioxidant biomarkers (CAT, GST and LPO). Accumulation of TCC in organisms depends on the lipophilicity and bioavailability of TCC in sediment and water. TCC was continuously detected in aquatic system. TCC is a lipophilic compound, which can efficiently bind with lipid content. Women are more vulnerable to TCC due to substantially higher frequency and extended exposure to TCC. This review provides basic information of occurrence of TCC and the exposure levels in aquatic organisms. Several literature have shown the higher usage and human exposure levels of TCC, which provides useful information for the chemical management approaches.

Occurrence, seasonal variation and risk evaluation of selected endocrine disrupting compounds and their transformation products in Jiulong river and estuary, China

In the present study, 13 endocrine disrupting compounds (EDCs) and their transformation products (TPs) were monitored in Jiulong River and its estuary, China in different seasons. The analytes included antimicrobials [triclosan (TCS) and triclocarbon (TCC)]; estrogens [estrone (E1), estradiol (E2), estriol (E3) and ethinylestradiol (EE2)]; alkylphenol ethoxylates [4-n-nonylphenol (NP) and 4-n-octylphenol (OP)] and the TPs [methyl triclosan (MeTCS), carbanilide (NCC), dichlorocarbanilide, 4-hydroxy estrone (4-OH E1) and 4-hydroxy estradiol (4-OH E2)]. A significant seasonal variation was observed for most EDCs. Approximately, 79% of the total E2 residues were detected in the normal season in comparison with the wet season to indicate recalcitrant behavior of E2 during the normal season. Risk assessment revealed that E2 was most potent among the EDCs to cause highest risk to both vertebrate and invertebrate aquatic species, whereas, E1, EE2, MeTCS and TCS also showed relatively high risk for some surface water aquatic species.

Nationwide reconnaissance of five parabens, triclosan, triclocarban and its transformation products in sewage sludge from China

China's rapid growth of both population size and sanitation infrastructure have created a heightened need for responsible management of sewage sludge. We applied liquid chromatography in conjunction with isotope dilution tandem mass spectrometry to measure multiple endocrine disrupting antimicrobials and their transformation products in 100 sewage sludge samples collected across 21 Chinese provinces/districts. Occurrences (detection frequencies) and concentrations (ng/g dry weight) were as follows: triclosan (99%; <4-4870), triclocarban (95%; <3-43,300), 2'-hydroxy-triclocarban (94%; <1-2340), 3'-hydroxy-triclocarban (91%; <1-1250), 3,3',4,4'-tetrachlorocarbanilide (100%; 22-580), dichlorocarbanilide (94%; <2-23,890), monocarbanilide (92%; <2-120), carbanilide (90%; <3-1,340), and five parabens: methyl- (98%; <2-630), ethyl- (96%; <2-170), propyl- (99%; <2-27), butyl- (89%; <2-11) and benzyl-paraben (7%; <2-12). The transformation products of triclocarban were measured for the first time in Chinese wastewater system, and ratios of transformation products to parental triclocarban indicate ongoing triclocarban dechlorination during wastewater treatment. Contaminant profiles and concentrations differed by region, treatment capacity, and wastewater type. Extrapolation of collected data yielded an estimate for the total mass of 13 analytes sequestered in Chinese sewage sludge of 68 t/y with an upper bound of 400 t/y. This China-wide survey established baseline levels of selected antimicrobials in sludges whose current disposal is performed with little regulatory oversight and enforcement.

Occurrence of triclocarban and benzotriazole ultraviolet stabilizers in water, sediment, and fish from Indian rivers

Triclocarban and benzotriazole ultraviolet stabilizers (BUVSs) are listed as high production volume synthetic chemicals, used extensively in personal care products. Many of these chemicals persist in the aquatic environment as micropollutants. Knowledge on their fate in freshwater ecosystems is still lacking, especially in the Indian Rivers. Our intention is to study the seasonal distribution, hazard quotient, risk assessment, and bioaccumulation of triclocarban and BUVSs (UV-9, UV-P, UV-326, UV-327, UV-328, and UV-329) during wet and dry seasons in water, sediment and fish from the Kaveri, Vellar, and Thamiraparani rivers in Tamil Nadu State, India. Triclocarban and BUVSs were identified in all matrices analysed. Triclocarban was found in water, sediment, and fish up to 1119ng/L, 26.3ng/g (dry wt.), and 692ng/g (wet wt.), respectively. Among BUVSs, UV-329 was found up to 31.3ng/L (water samples), UV-327 up to 7.3ng/g (sediment samples), and UV-9 up to 79.4ng/g (fish samples). The hazard quotient (HQ_env.) for triclocarban in surface water was found to be at risk level (HQ_env. >1) in the Kaveri, and Thamiraparani rivers during dry season. Bioaccumulation factors indicate that target compounds (triclocarban and BUVSs) could bio-accumulate in organisms.

Transformation, Conjugation, and Sequestration Following the Uptake of Triclocarban by Jalapeno Pepper Plants

Plant uptake and metabolism of emerging organic contaminants, such as personal-care products, pose potential risks to human health. In this study, jalapeno pepper ( Capsicum annuum) plants cultured in hydroponic media were exposed to both ¹⁴C-labeled and unlabeled triclocarban (TCC) to investigate the accumulation, distribution, and metabolism of TCC following plant uptake. The results revealed that TCC was detected in all plant tissues; after 12 weeks, the TCC concentrations in root, stem, leaf, and fruit tissues were 19.74 ± 2.26, 0.26 ± 0.04, 0.11 ± 0.01, and 0.03 ± 0.01 mg/kg dry weight, respectively. More importantly, a substantial portion of the TCC taken up by plants was metabolized, especially in the stems, leaves, and fruits. Hydroxylated TCC (e.g., 2'-OH TCC and 6-OH TCC) and glycosylated OH-TCC were the main phase I and phase II metabolites in plant tissues, respectively. Bound (or nonextractable) residues of TCC accounted for approximately 44.6, 85.6, 69.0, and 47.5% of all TCC species that accumulated in roots, stems, leaves, and fruits, respectively. The concentrations of TCC metabolites were more than 20 times greater than the concentrations of TCC in the above-ground tissues of the jalapeno pepper plants after 12 weeks; crucially, approximately 95.6% of the TCC was present as metabolites in the fruits. Consequently, human exposure to TCC through the consumption of pepper fruits is expected to be substantially higher when phytometabolism is considered.

Triclocarban enhances short-chain fatty acids production from anaerobic fermentation of waste activated sludge

Triclocarban (TCC), one typical antibacterial agent being widely used in various applications, was found to be present in waste activated sludge at significant levels. To date, however, its effect on anaerobic fermentation of sludge has not been investigated. This work therefore aims to fill this knowledge gap. Experimental results showed that when TCC content in sludge increased from 26.7 ± 5.3 to 520.5 ± 12.6 mg per kilogram total suspended solids, the maximum concentration of short-chain fatty acids (SCFA) increased from 32.6 ± 2.5 to 228.2 ± 3.6 (without pH control) and from 211.7 ± 2.4 to 378.3 ± 3.2 mg COD/g VSS (initial pH 10), respectively. The large promotion of acetic acid was found to be the major reason for the enhancement of total SCFA production. Although a significant level of TCC was degraded in the fermentation process, SCFA was neither produced from TCC nor affected by its major intermediates at the relevant levels. It was found that TCC facilitated solubilization, acidogenesis, acetogenesis, and homoacetogenesis processes but inhibited methanogenesis process. Microbial analysis revealed that the increase of TCC increased the microbial community diversity, the abundances of SCFA (especially acetic acid) producers, and the activities of key enzymes relevant to acetic acid production.

Functional Characterization of a Novel Amidase Involved in Biotransformation of Triclocarban and its Dehalogenated Congeners in Ochrobactrum sp. TCC-2

Haloaromatic antimicrobial triclocarban (3,4,4'-trichlorocarbanilide, TCC) is a refractory contaminant which is frequently detected in various aquatic and sediment environments globally. However, few TCC-degrading communities or pure cultures have been documented, and functional enzymes involved in TCC biodegradation hitherto have not yet been characterized. In this study, a bacterial strain, Ochrobactrum sp. TCC-2, capable of degrading TCC under both aerobic and anaerobic conditions was isolated from a sediment sample. A novel amidase gene (tccA), responsible for the hydrolysis of the two amide bonds of TCC and its dehalogenated congeners 4,4'-dichlorocarbanilide (DCC) and carbanilide (NCC) to more biodegradable chloroaniline or aniline products, was cloned and characterized. TccA shares low amino acid sequence identity (27 to 38%) with other biochemically characterized amidases and contains the conserved catalytic triad (Ser-Ser-Lys) of the amidase signature enzyme family. TccA was stable over a pH range of 5.0 to 10.0 and at temperatures lower than 60 °C, and it was constitutively expressed in strain TCC-2. In contrast to the halogenated TCC and DCC, the nonchlorinated NCC was the preferred substrate for TccA. TccA also had hydrolysis activity to a broad spectrum of amide bonds in herbicides, insecticides, and chemical intermediates. The constitutive expression and broad substrate spectrum of TccA suggested strain TCC-2 may be potentially useful for bioremediation applications.

Flume experiments to investigate the environmental fate of pharmaceuticals and their transformation products in streams

The hyporheic zone—the transition region beneath and alongside the stream bed—is a central compartment for attenuation of organic micropollutants in rivers. It provides abundant sorption sites and excellent conditions for biotransformation. We used a bench-scale flume to study the fate of 19 parent pharmaceuticals (PPs) and the formation of 11 characteristic transformation products (TPs) under boundary conditions similar to those in hyporheic zones. The persistence of PPs ranged from readily degradable with a dissipation half-life (DT50) as short as 1.8 days (acetaminophen, ibuprofen) to not degradable (chlorthalidone, fluconazole). The temporal and spatial patterns of PP and TP concentrations in pore water were heterogeneous, reflecting the complex hydraulic and biogeochemical conditions in hyporheic zones. Four TPs (carbamazepine-10,11-epoxide, metoprolol acid, 1-naphthol, and saluamine) were exclusively formed in the sediment compartment and released to surface water, highlighting their potential to be used as indicators for characterizing hyporheic transformation of micropollutants in streams. The accumulation of certain TPs over the experimental period illustrates that we might face a peak of secondary contamination by TPs far from the point of release of the original contaminants into a stream. Such TPs should be considered as priority candidates for a higher-tier environmental risk assessment.