Photodegradative fate and potential phototoxic products of bromocarbazoles and chlorocarbazoles in water.

Bromocarbazoles and chlorocarbazoles are emerging environmental contaminants that have been reported to be persistent and possessing dioxin-like toxicity; however, their photodegradative fate in water is unknown. The photodegradation of 3-bromocarbazole, 3-chlorocarbazole, and 3,6-dichlorocarbazole was determined in ultrapure water. They proceeded by direct photolysis and followed first-order kinetics. The rate constants (k) were 0.4838, 0.3454, and 0.4422 h-1 corresponding to half-lives (t 1/2) 1.81, 2.01, and 1.62, while the quantum yields (Ф) were 0.232, 0.180, and 0.295 respectively. The maximum wavelengths of absorption (λ max) were in the near ultraviolet region (295, 296, 299, and 301 nm) implying these compounds are likely to degrade slowly under sunlight in natural aquatic environment. The molar extinction coefficients (ε) determined in acetonitrile were 18,573, 17,028, 13,385, and 14,010 L mol-1 cm-1, respectively, the latter being 3,6-dibromocarbazole. A bathochromic shift was observed with halogen addition on their respective mono-substituted congeners. Bromocarbazoles were observed to degrade faster in water than chlorocarbazoles. In addition, photodegradation was estimated to proceed faster in summer than in winter, in natural water system at 50° N latitude. In the absence of light, hydrolytic degradation occurred but proceeded very slowly. Hexahydroxybenzene and trihydroxycarbazole were positively identified as the likely photoproducts with the former being a known toxic compound. Dehalogenation, oxidative cleavage, hydroxylation, and hydrolysis are suggested as the major photodegradation mechanisms in water, yielding phototoxic products that may be of enhanced toxicity than the parent compounds.

Depth profile of persistent and emerging organic pollutants upstream of the Three Gorges Dam gathered in 2012/2013.

Persistent and emerging organic pollutants were sampled in September 2012 and 2013 at a sampling site in front of the Three Gorges Dam near Maoping (China) in a water depth between 11 and 61 m to generate a depth profile of analytes. A novel compact water sampling system with self-packed glass cartridges was employed for the on-site enrichment of approximately 300 L of water per sample to enable the detection of low analytes levels in the picogram per liter-scale in the large water body. The overall performance of the sampling system was acceptable for the qualitative detection of polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs), perfluoroalkylic acids (PFAAs), pharmaceutical residues and polar pesticides. Strongly particle-associated analytes like PAHs and PCBs resided mainly in the glass wool filter of the sampling system, whereas all other compounds have mainly been enriched on the XAD-resin of the self-packed glass cartridges. The sampling results revealed qualitative information on the presence, depth distribution and origin of the investigated compounds. Although the depth profile of PAHs, PCBs, OCPs, and PFAAs appeared to be homogeneous, pharmaceuticals and polar pesticides were detected in distinct different patterns with water depth. Source analysis with diagnostic ratios for PAHs revealed their origin to be pyrogenic (burning of coal, wood and grass). In contrast, most PCBs and OCPs had to be regarded as legacy pollutants which have been released into the environment in former times and still remain present due to their persistence. The abundance of emerging organic pollutants could be confirmed, and their most abundant compounds could be identified as perfluorooctanoic acid, diclofenac and atrazine among investigated PFAAs, pharmaceuticals and polar pesticides, respectively.

Concentrations and mass fluxes estimation of organochlorine pesticides in Three Gorges Reservoir with virtual organisms using in situ PRC-based sampling rate.

Organochlorine pesticides (OCP) are widely distributed environmental pollutants. Due to their persistence and toxicity, it is important to know their fluxes and spatial and temporal distribution in the environment. In this study, a new procedure to estimate OCP concentration based on a set of performance reference compounds (PRCs) was used. Their occurrence and mass fluxes were assessed on a regional scale ranging from Chonqging to Maoping in Three Gorges Reservoir (TGR) as part of Yangtze River. The results are based on three sampling campaigns in 2009 (twice) and 2011. Due to different factors, the measured concentrations varied from 410 to 1418 pg/L. The highest total OCP concentration was localized in Wanzhou while the lowest was downstream Maoping near the Three Gorges Dam (TGD). The highest load of OCP mass fluxes was observed at Wanhzou with 9.6 mg/s and the lowest load at Maoping with 2.97 mg/s. Studies at Maoping show an increase in OCP water concentration from 2009 to 2012. Comparison between free dissolved OCP water concentration and total OCP water concentration in TGR 2009, 2011 and 2012 show a slight variation, indicating the important role of dilution in the OCP removal process in TGR.

Integrated targeted and non-targeted analysis of water sample extracts with micro-scale UHPLC-MS.

A sensitive method is introduced to detect selected pharmaceutical residues and polar pesticides with UHPLC-MS in water samples of different origin. Active or passive water sampling was combined with a laboratory solid-phase extraction cleanup and stable isotope dilution analysis. Recovery experiments demonstrated that the internal standard correction performed well for the compensation of matrix effects. Besides, the original targeted analysis approach was expanded by non-target analysis of the samples with only one more consecutive injection run needed. The key benefits of this multi-residue analysis are:•Targeted analysis and quantification combined with non-target analysis on a micro-scale UHPLC-MS system usually employed for qualitative analysis only.•The internal standards for targeted analysis were used in non-target runs to calculate the partition coefficient log P of unknown substances employing the retention time index (RTI).•The filtering of database hits for two criteria (exact mass and partition coefficient) significantly reduced the list of suspects and at the same time rendered it possible to perform non-target analysis with lower mass accuracy (no lock-spray) in the range of 20-500 ppm.

PAH distribution and mass fluxes in the Three Gorges Reservoir after impoundment of the Three Gorges Dam.

Mass fluxes of polycyclic aromatic hydrocarbons (PAHs) were calculated for the Three Gorges Reservoir (TGR) in China, based on concentration and discharge data from the Yangtze River. Virtual Organisms (VOs) have been applied during four campaigns in 2008, 2009 (twice) and 2011 at sampling sites distributed from Chongqing to Maoping. The total PAH mass fluxes ranged from 110 to 2,160 mg s(-1). Highest loads were determined at Chongqing with a decreasing trend towards Maoping in all four sampling campaigns. PAH remediation capacity of the TGR was found to be high as the mass flux reduced by more than half from upstream to downstream. Responsible processes are thought to be adsorption of PAH to suspended particles, dilution and degradation. Furthermore, the dependence of PAH concentration upon water depth was investigated at Maoping in front of the Three Gorges Dam. Although considerable differences could be revealed, there was no trend observable. Sampling of water with self-packed filter cartridges confirmed more homogenous PAH depth distribution. Moreover, PAH content of suspended particles was estimated from water concentrations gathered by VOs based on a water-particle separation model and subsequently compared to PAH concentration measured in water and in filter cartridges. It could be shown that the modeled data predicts the concentration caused by particle-bound PAHs to be about 6 times lower than PAHs dissolved in water. Besides, the model estimates the proportions of 5- and 6-ring PAHs being higher than in water phase.