Occurrence and seasonal variations of antibiotic micro-pollutants in the Wei River, China.

In this study, a systematic monitoring campaign of 30 antibiotics belonging to tetracyclines (TCs), macrolides (MLs), fluoroquinolones (FQs) and sulfonamides (SAs) was performed in the Xi'an section of the Wei River during three sampling events (December 2021, June 2022, and September 2022). The total concentrations of antibiotics in water ranged from 297 to 461 ng/L with high detection frequencies ranging from 45% to 100% for the various antibiotics. A marked seasonal variation in concentrations was found with total antibiotic concentrations in winter being 1.5 and 2 times higher than those in the summer and autumn seasons, respectively. The main contaminants in both winter and summer seasons were FQs, but in the autumn SAs were more abundant, suggesting different seasonal sources or more effective runoff for certain antibiotics during periods of rainfall. Combined analysis using redundancy and clustering analysis indicated that the distribution of antibiotics in the Wei River was affected by the confluence with dilution of tributaries and outlet of domestic sewage. Ecological risk assessment based on risk quotient (RQ) showed that most antibiotics in water samples posed insignificant risk to fish and green algae, as well as insignificant to low risk to Daphnia. The water-sediment distribution coefficients of SAs were higher than those of other antibiotics, indicating that particle-bound runoff could be a significant source for this class of antibiotics.

Comparing the photodegradation of typical antibiotics in ice and in water: Degradation kinetics, mechanisms, and effects of dissolved substances.

New antibiotic contaminants have been detected in both surface waters and natural ice across cold regions. However, few studies have revealed distinctions between their ice and aqueous photochemistry. In this study, the photodegradation and effects of the main dissolved substances on the photolytic kinetics were investigated for sulfonamides (SAs) and fluoroquinolones (FQs) in ice/water under simulated sunlight. The results showed that the photolysis of sulfamethizole (SMT), sulfachloropyridazine (SCP), enrofloxacin (ENR) and difloxacin (DIF) in ice/water followed the pseudo-first-order kinetics with their quantum yields ranging from 4.93 × 10-3 to 11.15 × 10-2. The individual antibiotics experienced disparate photodegradation rates in ice and in water. This divergence was attributed to the concentration-enhancing effect and the solvent cage effect that occurred in the freezing process. Moreover, the main constituents (Cl-, HASS, NO3- and Fe(III)) exhibited varying degrees of promotion or inhibition on the photodegradation of SAs and FQs in the two phases (p < 0.05), and these effects were dependent on the individual antibiotics and the matrix. Extrapolation of the laboratory data to the field conditions provided a reasonable estimate of environmental photolytic half-lives (t1/2,E) during midsummer and midwinter in cold regions. The estimated t1/2,E values ranged from 0.02 h for ENR to 14 h for SCP, which depended on the reaction phases, latitudes and seasons. These results revealed the similarities and differences between the ice and aqueous photochemistry of antibiotics, which is important for the accurate assessment of the fate and risk of these new pollutants in cold environments.

Insight into typical photo-assisted AOPs for the degradation of antibiotic micropollutants: Mechanisms and research gaps.

Due to the incomplete elimination by traditional wastewater treatment, antibiotics are becoming emerging contaminants, which are proved to be ubiquitous and promote bacterial resistance in the aquatic systems. Antibiotic pollution has raised particular concerns, calling for improved methods to clean wastewater and water. Photo-assisted advanced oxidation processes (AOPs) have attracted increasing attention because of the fast reaction rate, high oxidation capacity and low selectivity to remove antibiotics from wastewater. On the basis of latest literature, we found some new breakthroughs in the degradation mechanisms of antibiotic micropollutants with respect to the AOPs. Therefore, this paper summarizes and highlights the degradation kinetics, pathways and mechanisms of antibiotics degraded by the photo-assisted AOPs, including the UV/O3 process, photo-Fenton technology, and photocatalysis. In the processes, functional groups are attacked by hydroxyl radicals, and major structures are destroyed subsequently, which depends on the classes of antibiotics. Meanwhile, their basic principles, current applications and influencing factors are briefly discussed. The main challenges, prospects, and recommendations for the improvement of photo-assisted AOPs are proposed to better remove antibiotics from wastewater.

[Critical Review on Environmental Occurrence and Photochemical Behavior of Substituted Polycyclic Aromatic Hydrocarbons].

Substituted polycyclic aromatic hydrocarbons (SPAHs) are a type of emerging pollutant that widely exist in the environment, which also exhibit carcinogenicity, mutagenicity, and teratogenicity. These pollutants belong to toxic pollutants because of their similar structures to polycyclic aromatic hydrocarbons (PAHs). Their environmental behavior and ecological risk have attracted increasing attention. Based on a literature review, we found a new breakthrough in the source, distribution, behavior, and risk of SPAHs with comparison to traditional pollutants PAHs. This paper reviewed the current research progress on the environmental occurrence and photochemical behavior of SPAHs. Their sources, formation mechanisms, and distribution characteristics in the multimedia environment were highlighted, and the photochemical transformation kinetics, pathways, and affecting factors of SPAHs in water, ice, and other media were discussed. Furthermore, the research prospects about the environmental behavior and risk of SPAHs were proposed.

Organophosphate esters in the seawater of the Bohai Sea: Environmental occurrence, sources and ecological risks.

Organophosphate esters (OPEs) are widely distributed in surface water systems, but limited information was available on the spatial occurrence and ecological risks of OPEs in the Bohai Sea. In this study, 89 water samples in the Bohai Sea and the five surrounding rivers were investigated for the determination of 15 OPEs. The concentration of ∑15OPEs ranged from 373.20 to 2931.27 ng·L-1 in the river water and 137.81 to 2641.30 ng·L-1 in the seawater, with high levels of OPEs in Liaodong Bay. Tris(2-chloroethyl) phosphate (TCEP, 10- 92 %) and triethyl phosphate (TEP, 5- 64 %) were dominant for OPEs. The correlation analysis, principal component analysis and hierarchical cluster analysis suggested the conjunction of municipal wastewater via river input and maritime shipping was the main source of OPEs in the Bohai Sea. The ecological risk assessment indicated that the individual OPEs arise low ecological risks in the Bohai Sea, while medium ecological risks of ∑15OPEs are in minority river samples.

Photodegradation of hydroxyfluorenes in ice and water: A comparison of kinetics, effects of water constituents, and phototransformation by-products.

The photochemical behavior of organic pollutants in ice is poorly studied in comparison to aqueous photochemistry. Here we report a detailed comparison of ice and aqueous photodegradation of two representative OH-PAHs, 2-hydroxyfluorene (2-OHFL) and 9-hydroxyfluorene (9-OHFL), which are newly recognized contaminants in the wider environment including colder regions. Interestingly, their photodegradation kinetics were clearly influenced by whether they reside in ice or water. Under the same simulated solar irradiation (λ > 290 nm), OHFLs photodegraded faster in ice than in equivalent aqueous solutions and this was attributed to the specific concentration effect caused by freezing. Furthermore, the presence of dissolved constituents in ice also influenced photodegradation with 2-OHFL phototransforming the fastest in 'seawater' ice (k = (11.4 ± 1.0) × 10-2 min-1) followed by 'pure-water' ice ((8.7 ± 0.4) × 10-2 min-1) and 'freshwater' ice ((8.0 ± 0.7) × 10-2 min-1). The presence of dissolved constituents (specifically Cl-, NO3-, Fe(III) and humic acid) influences the phototransformation kinetics, either enhancing or suppressing phototransformation, but this is based on the quantity of the constituent present in the matrixes, the specific OHFL isomer and the matrix type (e.g., ice or aqueous solution). Careful derivation of key photointermediates was undertaken in both ice and water samples using tandem mass spectrometry. Ice phototransformation exhibited fewer by-products and 'simpler' pathways giving rise to a range of hydroxylated fluorenes and hydroxylated fluorenones in ice. These results are of importance when considering the fate of PAHs and OH-PAHs in cold regions and their persistence in sunlit ice.

Occurrence, spatial distributions, and ecological risk of pyrethroids in coastal regions of South Yellow and East China Seas.

Pyrethroids are increasingly receiving attention as aqueous micropollutants, but their presence has been reported only in a few small coastal areas. In this study, we investigated the distribution, sources, and risks of nine pyrethroids in large marine zones. The 40 seawater samples were collected from the South Yellow Sea (SYS) and East China Sea (ECS) in China, during the spring of 2020, using a high-volume, solid-phase extraction method. The total pyrethroid concentrations ranged from 0.72 to 1.82 ng L-1 in the SYS and from 0.02 to 11.0 ng L-1 in the ECS. We used cluster analysis to classify pollutant sources into five categories, and discussed the influence of sources on the transport and distribution of pyrethroids in each group. Ecological risk assessment indicated that pyrethroids pose a high risk to crustaceans and a negligible risk to others. These results are important for understanding the behavior of pyrethroids in marine environments.

Exploring the influence of concentration fluctuation and matrix effects on a passive sampler of triolein-embedded cellulose acetate membrane measuring polychlorinated biphenyls in water.

A membrane of triolein-embedded cellulose acetate membrane (TECAM), as an integrative passive sampler, was applied to adsorb 28 polychlorinated biphenyls (PCBs) from pure water and sea water in order to probe into the influence of concentration fluctuation and water matrix. The results demonstrated the temporal variations of PCBs concentrations in TECAM followed the first-order kinetics model. The periodic refreshment of solution and matrix effects of sea water significantly prolonged the time that PCBs reached equilibrium stage. The refreshment facilitated the uptake mass in TECAM. On the contrary, the matrix effects of sea water and dissolved organic matter (DOM) declined the PCBs absorption to TECAM. The average logKP values of PCBs in pure water were about 1.2 log unit higher than those in sea water in the experiments that the solution was not refreshed, while the difference of average logKP values narrowed to 0.3 log unit if the PCBs solutions were periodically refreshed. The correlation between logKP and logKOW values fitted the quadratic curve well, which was similar to semi-permeable membrane device (SPMD). The appropriate sampling times (t94%) ranged from 98.8 to 819 h (mean 500 h) for pure water with refreshment, much longer than those in sea water with refreshment (80.1~410 h, mean 189 h). The t94% values in the solution with high DOM content increased significantly, up to 409 h. Furthermore,  comparing the two experiments that the spiked pure water and sea water solution were refreshed frequently, the estimated sampling rates (Rs) in pure water (0.154~2.06 L/day with a mean value of 0.605 L/day) were slightly lower than those in sea water (0.292~3.84 L/day with a mean value of 1.69 L/day). However, the Rs values in sea water with DOM declined sharply to 0.042 L/day. Therefore, concentration fluctuation, matrix effect, and DOM contents of sea water evidently posed significant influence on dynamic parameters of TECAM absorption, which would be screened and probed detailed in future.

Selective diffusive gradients in thin-films with molecularly imprinted polymer for measuring fluoroquinolone antibiotics in waters.

Fluoroquinolones (FQs) have raised significant concerns due to their ubiquitous occurrence and promoting of antimicrobial resistance (AMR). In this study, a molecularly imprinted polymer-diffusive gradient in thin-films (MIP-DGT) sampler is developed for selective measurement of FQs in waters by using a commercial available MIP material as the binding agent. The MIP-DGT shows selective adsorption of the FQs and linearly accumulates the FQs over the deployment time. MIP-DGT measurement is independent of pH (6-8) and ionic strength (IS) (0.01-0.5 M) but is affected by DOM at higher concentrations (~10 mg•L-1), which is due to the altered diffusion coefficients and reduced adsorption on the MIP binding gel. Significant interaction effects of DOM with pH or IS indicate that this is the predominant influence on the MIP-DGT performance, which results in a lower measurement by the MIP-DGT but this is curtailed to some extend with increasing IS or pH. The MIP-DGT measurements, however, correlate well with those by grab sampling in a wastewater treatment plant, suggesting it is reliable for measuring FQs in waters. For the first time, we demonstrate that key water chemistry parameters do have interaction effects on the DGT measurements, which should be considered for the data interpretation. The MIP-DGT is a promising tool to understand the interaction effects of the environmental parameters on the fate, behaviours and bioavailability/toxicity of organic contaminants and improve environmental risk assessments in the environment and modelling.

Distribution and sources of polycyclic aromatic hydrocarbons in the water column of Kongsfjorden, Arctic.

Kongsfjorden is known for its characteristic multi-layer water mass formed by the convergence of freshwaters from nearby glaciers and rivers and saline water from the Atlantic and Arctic. The distribution of polycyclic aromatic hydrocarbons (PAHs) in the water column of Kongsfjorden was investigated and their potential sources were analyzed. The total concentrations of 16 PAHs in the surface seawater and river water were in the range of 33.4-79.8 ng/L (mean 48.5 ng/L) and 2.3-201.4 ng/L (mean 126.1 ng/L), respectively. Horizontally, PAHs were mainly concentrated around river estuaries and the glacier front in the dissolved phase. Vertically, the PAHs in the particulate phase followed surface-enrichment and depth-depletion patterns in most stations, with the maximum concentration found at 50 m depth in the central area of Kongsfjorden. The compositions of PAHs in seawater and rivers were similar, with two-ring and tricyclic PAHs comprising the majority of the dissolved and particulate phases. PAHs found in Kongsfjorden waters appeared to be derived from multiple sources such as petroleum and coal combustion. PAHs in the bay mouth of Kongsfjorden were mainly introduced by the West Spitsbergen Current and the Arctic waters, while in the inner bay, atmospheric deposition and local sources were the major contributors. The distribution of PAHs was mainly attributed to the suspended particulate distribution.

The importance of reactive oxygen species on the aqueous phototransformation of sulfonamide antibiotics: kinetics, pathways, and comparisons with direct photolysis.

Sulfonamide antibiotics (SAs) are increasingly detected as aquatic contaminants and exist as different dissociated species depending on the pH of the water. Their removal in sunlit surface waters is governed by photochemical transformation. Here we report a detailed examination of the hydroxyl radical (•OH) and singlet oxygen (1O2) mediated photooxidation of nine SAs: sulfamethoxazole, sulfisoxazole, sulfamethizole, sulfathiazole, sulfamethazine, sulfamerazine, sulfadiazine, sulfachloropyridazine and sulfadimethoxine. Both •OH and 1O2 oxidation kinetics varied depending on the dominant protonated states of the SA in question (H2SAs+, HSAs0 and SAs-) as a function of pH. Based on competition kinetic experiments and matrix deconvolution calculations, HSAs0 or SAs- (pH ∼5-8) were observed to be more highly reactive towards •OH, while SAs- (pH ∼8) react the fastest with 1O2 for most of the SAs tested. Using the empirically derived rates of reaction for the speciated forms at different pHs, the environmental half-lives were determined using typical 1O2 and •OH concentrations observed in the environment. This approach suggests that photochemical 1O2 oxidation contributes more than •OH oxidation and direct photolysis to the overall phototransformation of SAs in sunlit waters. Based on the identification of key photointermediates using tandem mass spectrometry, 1O2 oxidation generally occurred at the amino moiety on the molecule, whereas •OH reaction experienced multi-site hydroxylation. Both these reactions preserve the basic parent structure of the compounds and raise concerns that the routes of phototransformation give rise to intermediates with similar antimicrobial potency as the parent SAs. We therefore recommend that these phototransformation pathways are included in risk assessments concerning the presence and fate of SAs in waste and surface waters.

The legacy of organochlorinated pesticides (OCPs), polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) in Chinese coastal seawater monitored by semi-permeable membrane devices (SPMDs).

Semi-permeable membrane devices (SPMDs) were applied to sample some Organochlorinated Pesticides (OCPs), Polycyclic Aromatic Hydrocarbons (PAHs) and Polychlorinated Biphenyls (PCBs) from the seawater of 14 Chinese coastal areas. The total concentrations of OCPs (∑16OCPs), PAHs (∑15PAHs) and PCBs (∑35PCBs) were in the ranges of 489.2-2174, 589.4-53,160, and 133.2-3658 ng/g lipid, respectively. The ∑15PAHs varied significantly with the sampling locations, which were far higher in north Chinese coastal areas than in south areas, whereas ∑16OCPs and ∑35PCBs only slightly fluctuated along the entire coast line. Comparing SPMD to grab sampler, it was found that the distribution patterns of the PCBs and OCPs in seawater were generally similar. However, the compositional profiles of the PAHs, PCBs, DDTs and HCHs in SPMDs were slightly different to grab samplers and organisms. The SPMDs accumulated less lipotropic compounds, which are inclined to dissolve in water rather than in organisms.

Fate and deposition of polycyclic aromatic hydrocarbons in the Bransfield Strait, Antarctica.

Fifteen polycyclic aromatic hydrocarbons (PAHs) were detected in seawater and atmosphere of Bransfield Strait. The concentration of ∑15[PAH] in the atmosphere ranged from 3.75 to 8.53 ng m-3, and three-ring PAHs were the most abundant compounds. Dissolved ∑15[PAH] in seawater ranged from 5.42 to 34.37 ng L-1, and the level of PAHs was markedly different on each side of the strait. The air-sea gas exchange process and molecular diagnostic ratios were calculated, results showed that the environmental behavior of PAHs was net deposition along this cruise. Given the changes in global transport routes of pollutants under global warming, the role of long-range transport (LRT) may be enhanced. Taking the Antarctic as a sink of PAHs due to the LRT and net deposition, PAHs will continue to load into the seawater of this area via atmospheric deposition, which contributes to improving our understanding of the environmental behavior of PAHs.

Exploring the aquatic photodegradation of two ionisable fluoroquinolone antibiotics - Gatifloxacin and balofloxacin: Degradation kinetics, photobyproducts and risk to the aquatic environment.

Fluoroquinolone antibiotics (FQs) are ubiquitous and ionisable in surface waters. Here we investigate gatifloxacin (GAT) and balofloxacin (BAL), two widely used FQs, and determine the photochemical reactivity of their respective dissociation species that arise at different pH to understand the relevance and pathways of phototransformation reactions. Simulated-sunlight experiments and matrix calculations showed that neutral forms (HFQs0) of the two antibiotics had the highest apparent photolytic efficiency and hydroxyl-radical oxidation reactivity. Based on the pH-dependent photochemical reactivities, the solar apparent photodegradation half-lives (t1/2) in sunlit surface waters ranged from 14.5-169min and was 1-2 orders of magnitude faster than hydroxyl-radical induced oxidation (t1/2=20.9-29.8h). The corresponding pathways were proposed based on the identification of key intermediates using HPLC-ESI-MS/MS. The apparent photodegradation induced defluorination, decarboxylation, and piperazinyl oxidation and rearrangement, whereas hydroxyl-radical oxidation caused hydroxylated defluorination and piperazinyl hydroxylation. The photomodified toxicity of GAT and BAL was examined using an Escherichia coli activity assay. E. coli activity was not affected by BAL, but was significantly affected by the photo-modified solutions of GAT, indicating that primary photo-degradates have a comparable or higher antibacterial activity than the parent GAT. In fresh water and seawater this antibacterial activity remained high for up to 24h, even after GAT had undergone significant photodegradation (>1 half-life), indicating the potential impact of this chemical on microbial communities in aquatic systems.

Aqueous multivariate phototransformation kinetics of dissociated tetracycline: implications for the photochemical fate in surface waters.

Antibiotics are ubiquitous pollutants in aquatic systems and can exist as different dissociated species depending on the water pH. New knowledge of their multivariate photochemical behavior (i.e., the photobehavior of different ionized forms) is needed to improve our understanding on the fate and possible remediation of these pharmaceuticals in surface and waste waters. In this study, the photochemical degradation of aqueous tetracycline (TC) and its dissociated forms (TCH20, TCH-, and TC2-) was investigated. Simulated sunlight experiments and matrix calculations indicated that the three dissociated species had dissimilar photolytic kinetics and photooxidation reactivities. TC2- photodegraded the fastest due to apparent photolysis with a kinetic constant of 0.938 ± 0.021 min-1, followed by TCH- (0.020 ± 0.005 min-1) and TCH20 (0.012 ± 0.001 min-1), whereas TCH- was found to be the most highly reactive toward •OH (105.78 ± 3.40 M-1 s-1), and TC2- reacted the fastest with 1O2 (344.96 ± 45.07 M-1 s-1). Water with relatively high pH (e.g., ~ 8-9) favors the dissociated forms of TCH- and TC2- which are most susceptible to photochemical loss processes compared to neutral TC. The calculated corresponding environmental half-lives (t1/2,E) in sunlit surface waters ranged from 0.05 h for pH = 9 in midsummer to 3.68 h for pH = 6 in midwinter at 45° N latitude. The process was dominated by apparent photolysis (especially in summer, 62-91%), followed by 1O2 and •OH oxidation. Adjusting the pH to slightly alkaline conditions prior to UV or solar UV light treatment may be an effective way of enhancing the photochemical removal of TC from contaminated water. Graphical abstract Aqueous multiple photochemical behavior of dissociated tetracycline (TCH20, TCH-, and TC2-) is first comprehensively reported on revealing the phototransformation kinetics and implications for the fate in surface waters.

Occurrence and distribution of perfluoroalkyl substances (PFASs) in the water dissolved phase and suspended particulate matter of the Dalian Bay, China.

In the present study, the contamination level and spatial distribution of PFASs in the water dissolved phase and suspended particulate matter (SPM) phase of the Dalian Bay, and the SPM-water partition behavior were investigated. The total concentrations of PFASs (∑PFASs) in the water dissolved phase ranged from 6.9 to 17.1 ng L-1, with perfluorooctanoic acid (PFOA), perfluorobutanoic acid, and perfluorobutane sulfonate (PFBS) as the predominant PFASs, while ∑PFASs in SPM ranged from 1.7 to 27.5 ng g-1 dw with higher contributions from PFBS, perfluorooctane sulfonic acid and PFOA. As for the pollution distribution, the concentrations of PFASs inside the Dalian Bay were higher than those outside the bay. For perfluoroalkyl carboxylic acid (PFCAs) and perfluoroalkane sulfonic acids (PFSAs), the suspended particulate matter-water partition coefficient (log Kd) values ranged from 2.62 to 3.76, and from 3.39 to 3.56, respectively. The log Kd values of PFASs generally increased with the increasing perfluorinated carbon chain length. Short-chain PFCAs were mostly detected in the water dissolved phase, while long-chain PFCAs and PFSAs appeared to bind more strongly to SPM phase. The contamination level of long-chain PFCAs and PFSAs could be underestimated if only the water dissolved phase were measured. Therefore, further investigations should consider the role of SPM on the environmental behavior and fate of PFASs in the aquatic environment.

Trophic magnification of Dechlorane Plus in the marine food webs of Fildes Peninsula in Antarctica.

The food web composition, assimilation efficiency of Dechlorane Plus (DP) in food web components, and even extrinsic conditions can affect the trophic biomagnification potentials of DP isomers in food webs. Antarctica ecological system is characterized by the presence of few consumers and simple trophic levels (TLs), which are crucial in discussing the behavior of contaminants. To assess the biomagnification potential of DP in the Antarctic food web, nine representative species were sampled and analyzed from the Fildes Peninsula. Results showed the DP concentrations ranged from 0.25ngg-1 to 6.81ngg-1 lipid weight in Antarctic biota and the concentrations of anti-DP and syn-DP showed significantly positive correlations with TLs (p<0.05, ra=0.85; rs=0.81, respectively), suggesting that syn-DP and anti-DP underwent biomagnification and the biomagnification ability of anti-DP was higher than that of syn-DP. The anti-DP fraction (anti-DP/∑DP) (ƒanti=0.23-0.53) of the organisms was lower than that of commercial products (ƒanti=0.68), demonstrating ƒanti was changed during long-range atmospheric transport or stereoselection enrichment through the food web. Furthermore, based on food web magnification factors (FWMF) comparison between DP and polychlorinated biphenyls (PCBs), the biomagnification potential of DP was found to be similar to that of highly chlorinated PCBs.

Using Monte Carlo simulation to assess uncertainty and variability of methamphetamine use and prevalence from wastewater analysis.

BACKGROUND: In recent years, methamphetamine (METH) has increased dramatically in China. However, little is known regarding the prevalence of METH use among the general population in China. METHODS: We provided a method to estimate the consumption and prevalence of METH in a city based on wastewater analysis. Monte Carlo simulations were employed to assess the uncertainty and variability of the consumption and prevalence rate in Beijing. RESULTS: METH consumption in Beijing based on Monte Carlo simulation varied between 1.3 and 5.2kg per day with a median of 2.6kg per day. In 2013, the 12-month prevalence of METH use was 0.58% (95% confidential interval 0.08-3.16) among the general population aged 15-64 years. A population-weight consumption map displayed the geographical differences in Beijing. CONCLUSIONS: The proposed method dramatically improved the accuracy and reliability and can be used as a useful complementary tool to official methodologies for drug use monitoring. This report describes the first comprehensive study concerning the prevalence of METH among the general population in mainland China.

Photochemical degradation of hydroxy PAHs in ice: Implications for the polar areas.

Hydroxyl polycyclic aromatic hydrocarbons (OH-PAHs) are derived from hydroxylated PAHs as contaminants of emerging concern. They are ubiquitous in the aqueous and atmospheric environments and may exist in the polar snow and ice, which urges new insights into their environmental transformation, especially in ice. In present study the simulated-solar (λ > 290 nm) photodegradation kinetics, products and pathways of four OH-PAHs (9-Hydroxyfluorene, 2-Hydroxyfluorene, 1-Hydroxypyrene and 9-Hydroxyphenanthrene) in ice were investigated, and the corresponding implications for the polar areas were explored. It was found that the kinetics followed the pseudo-first-order kinetics with the photolysis quantum yields (Φs) ranging from 7.48 × 10(-3) (1-Hydroxypyrene) to 4.16 × 10(-2) (2-Hydroxyfluorene). These 4 OH-PAHs were proposed to undergo photoinduced hydroxylation, resulting in multiple hydroxylated intermediates, particularly for 9-Hydroxyfluorene. Extrapolation of the lab data to the real environment is expected to provide a reasonable estimate of OH-PAH photolytic half-lives (t1/2,E) in mid-summer of the polar areas. The estimated t1/2,E values ranged from 0.08 h for 1-OHPyr in the Arctic to 54.27 h for 9-OHFl in the Antarctic. In consideration of the lower temperature and less microorganisms in polar areas, the photodegradation can be a key factor in determining the fate of OH-PAHs in sunlit surface snow/ice. To the best of our knowledge, this is the first report on the photodegradation of OH-PAHs in polar areas.

Illicit drugs and their metabolites in 36 rivers that drain into the Bohai Sea and north Yellow Sea, north China.

Illicit drugs and their metabolites have recently been recognized as an emerging group of contaminants due to their potential ecotoxicological impact in aquatic ecosystems. To date, information on the occurrence of these compounds in the aquatic environment of China remains limited. In this study, we collected surface water samples from 36 rivers in north China that discharge into the Bohai Sea and north Yellow Sea and measured the concentrations of amphetamine-like compounds, ketamines, cocainics, and opioids. The occurrence and spatial patterns of these substances show significant differences between the rivers and regions. Two designer drugs, methamphetamine (METH) and ketamine (KET), were the most abundant compounds detected in the entire set of samples (detection frequency of 92 and 69 %). The concentrations of METH and KET ranged from <0.1 to 42.0 ng L(-1) (mean = 4.53 ng L(-1)) and <0.05 to 4.50 ng L(-1) (mean = 0.49 ng L(-1)), respectively. The high detection frequencies of METH and KET are consistent with the fact that they are the main illicit drugs consumed in China. The high concentrations of these illicit drugs and their metabolites were found in areas that have a high population density. The riverine input of total illicit drugs into the Bohai Sea and north Yellow Sea was estimated to be in the range of 684 to 1160 kg per year.