Modelling the dynamic gas/particle partitioning process of semi-volatile organic compounds emitted from point sources: Quantitative analysis and impact assessment.

The deleterious impact of pollution point sources on the surrounding environment and human has long been a focal point of environmental research. When considering the local atmospheric dispersion of semi-volatile organic compounds (SVOCs) around the emission sites, it is essential to account the dynamic process for the gas/particle (G/P) partitioning, which involves the transition from an initial state to a steady state. In this study, we have developed a model that enables the prediction of the dynamic process for G/P partitioning of SVOCs, particularly considering the influence from emission. It is important to note that the dynamic processes of the concentrations of SVOCs in particle phase (CP) and in gas phase (CG) differ significantly. These differences arise due to the influence of two critical factors: particulate proportion of SVOCs in the emissions (ϕ0) and octanol-air partitioning coefficient (KOA). The validity of our model was assessed by comparing its predictions of the extremum value of the G/P partitioning quotient (KP) with the results obtained from the steady-state model. Remarkably, the characteristic time (tC), used to evaluate the timescale required for SVOCs to reach steady state, demonstrated different variations with KOA for CP and CG. Additionally, the values of tC were quite different for CP and CG, which were markedly influenced by ϕ0. For some SVOCs with high KOA values, it took approximately 35 h to reach steady state. Furthermore, it was found that the time to achieve 95 % of steady state (t95 ≈ 3tC) could reach approximately 105 h. This duration is sufficient for chemicals to disperse from their emission site to the surrounding areas. Therefore, it is crucial to consider the dynamic process of G/P partitioning in local atmospheric transport studies. Moreover, the influence of ϕ0 should be incorporated into future investigations examining the dynamic process of G/P partitioning.

Pollution characteristics, source apportionment and absorption spectra of size-resolved PAHs in atmospheric particles in a cold megacity of China.

Polycyclic aromatic hydrocarbons (PAHs) have the capability for solar radiation absorption related to climate forcing. Herein, pollution characteristics and absorption spectra of size-resolved PAHs in atmospheric particles in a cold megacity were comprehensively investigated. The mean concentrations of Σ18PAHs in all the 11 particle size ranges were 3.95 ± 4.77 × 104 pg/m3 and 2.17 ± 1.54 × 103 pg/m3 in heating period (HP) and non-heating period (NHP), respectively. Except for most PAHs with 2 and 3 benzene rings in NHP, most other PAHs showed a unimodal distribution pattern with the peak at 0.56-1.0 µm in both periods, which was caused by PAH emission sources. The PAH-related climate forcing was mainly caused by the solar radiation absorptions at ∼325 (∼330) nm and ∼365 nm. In general, the absorption intensities were higher in HP than NHP. The absorption intensity in the particle size range of 0.56-1.0 µm was the highest, and benzo[e]pyrene was the dominant contributor. In colder periods in HP, higher PAH concentrations caused more intensive PAH-related climate forcing. This study provided new insights for pollution characteristics and absorption spectra of size-resolved PAHs in atmospheric particles, which will be useful for better understanding PAH-related climate forcing.

Efficient low-concentration phosphate removal from sub-healthy surface water by adsorbent prepared based on functional complementary strategy.

The remediation of low-concentration phosphorus polluted surface water (LP-SW) is one of most challenging environmental issues worldwide. Adsorption is more suitable for LP-SW remediation due to its low cost and operability. Based on the strategy of functional complementation among industrial solid wastes (ISWs), ISW-based phosphate absorbent material (PAM) was prepared from coal ash (CA, binder), rich­calcium (Ca) carbide slag (CS, active component) and iron salt (functional reagent) by optimizing materials ratios and roasting conditions. PAM prepared under optimal conditions (Fe/CC-2opt) had good phosphate adsorption efficiency. Notably, Fe/CC-2opt not only ensured that the effluent met Environmental Quality Standards for Surface Water (pH = 6.0-9.0), but also facilitated the formation of brushite instead of hydroxyapatite due to FeSO4 addition. Compared with hydroxyapatite, brushite had greater potential application value as fertilizer due to its solubility and high P/Ca ratio. The possible mechanisms of phosphate adsorption by PAM included surface precipitation, surface complexation, electrostatic adsorption and release of Ca2+/OH-. Preparation cost of PAM was 80 US$/ton, and treatment cost was 0.07 US$/g P. Regeneration efficiency of PAM was still above 80 % after five cycles. The design idea and result of this study provide theoretical basis and technical support for the preparation of PAM with low cost, commercial production and great adsorption capacity.

Health Risk Assessment of Organophosphate Flame Retardants in Soil Across China Based on Monte Carlo Simulation.

Health risks from exposure to contaminants are generally estimated by evaluating concentrations of the contaminants in environmental matrixes. However, accurate health risk assessment is difficult because of uncertainties regarding exposures. This study aims to utilize data on the concentrations of organophosphate flame retardants (OPFRs) in surface soil across China coupled with Monte Carlo simulations to compensate for uncertainties in exposure to evaluate the health risks associated with contamination of soil with this class of flame retardants. Results revealed that concentrations of ∑OPFRs were 0.793-406 ng/g dry weight (dw) with an average of 23.2 ng/g dw. In terms of spatial distribution, higher OPFRs concentrations were found in economically developed regions. Although the values of health risk of OPFRs in soil across China were below the threshold, the high concentrations of OPFRs in soil in some regions should attract more attentions in future. Sensitivity analysis revealed that concentrations of OPFRs in soil, skin adherence factor, and exposure duration were the most sensitive parameters in health risk assessment. In summary, the study indicated that the national scale soil measurement could provide unique information on OPFRs exposure and health risk assessment, which was useful for the management of soil in China and for better understanding of the environmental fate of OPFRs in the global perspective.

Effectively removing gaseous polycyclic aromatic hydrocarbons (PAHs) by willow catkins: Do you still dislike the catkins floating?

The floating catkins generated by willow and poplar trees have been criticized for spreading germ and causing fire for decades. It has been found that catkins are with a hollow tubular structure, which made us wonder if the floating catkins can adsorb atmospheric pollutions. Thus, we conducted a project in Harbin, China to investigate whether and how willow catkins could adsorb atmospheric polycyclic aromatic hydrocarbons (PAHs). The results suggest that both the catkins floating in the air and on the ground preferred to adsorb gaseous PAHs rather than particulate PAHs. Moreover, 3- and 4-ring PAHs were the dominating compositions adsorbed by catkins, which significantly increased with exposure time. The gas/catkins partition (KCG) was defined, which explained why 3-ring PAHs are more easily adsorbed by catkins than by airborne particles when their subcooled liquid vapor pressure is high (log PL > -1.73). The removal loading of atmospheric PAHs by catkins were estimated as 1.03 kg/year in the center city of Harbin, which may well explain the phenomenon that levels of gaseous and total (particle + gas) PAHs are relatively low in the months with catkins floating reported in peer-reviewed papers.

Influence on the levels of PAHs and methylated PAHs in surface soil from pollution control in China: Evidence in 2019 data compared with 2005 and 2012 data.

To comprehensively clarify the pollution characteristics of persistent toxic substances, the Soil and Air Monitoring Program Phase III (SAMP-III) was conducted in 2019 in China. In total, 154 surface soil samples were collected across China, and 30 unsubstituted polycyclic aromatic hydrocarbons (U-PAHs) and 49 methylated PAHs (Me-PAHs) were analyzed in this study. The mean concentrations of total U-PAHs and Me-PAHs were 540 ± 778 and 82.0 ± 132 ng/g dw, respectively. Northeastern China and Eastern China are the two regions of concern with high PAH and BaP equivalency levels. Compared with SAMP-I (2005) and SAMP-II (2012), an obvious upward temporal trend followed by a downward trend of PAH levels was observed in the past 14 years for the first time. The mean concentrations of 16 U-PAHs were 377 ± 716, 780 ± 1010, and 419 ± 611 ng/g dw in surface soil across China for the three phases, respectively. Considering rapid economic growth and energy consumption, an increasing trend from 2005 to 2012 was expected. From 2012 to 2019, the PAH levels in soils across China decreased by 50 %, which was consistent with the decline in PAH emissions. The period of reduction of PAHs in surface soil coincided with the implementation of Air and Soil Pollution Control Actions in China after 2013 and 2016, respectively. Along with the pollution control actions in China, the pollution control of PAHs and the increase in soil quality can be expected in the near future.

National-scale monitoring of historic used organochlorine pesticides (OCPs) and current used pesticides (CUPs) in Chinese surface soil: Old topic and new story.

Along with the restriction and prohibition of historic used organochlorine pesticides (OCPs), current used pesticides (CUPs) were widely used as alternatives. In order to investigate the pollution characteristics of pesticides, the levels and spatial distributions of OCPs and CUPs in 154 surface soil across China were comprehensively compared. Totally, 107 target pesticides were screened, and 20 OCPs and 34 CUPs were detected. The numbers of co-occurred pesticides in single soil sample were from 17 to 36 indicating the diversity and complexity of pesticides pollution. The concentrations of OCPs in urban soils were higher than rural soils, while rural > urban for CUPs. Furthermore, obviously different spatial distribution patterns were found for OCPs and CUPs. For OCPs, the secondary distribution pattern was dominant. For CUPs, the primary distribution pattern was obviously observed due to their current extensive usage. In addition, higher concentrations of both CUPs and OCPs were accumulated in the Northeast China Plain due to long-range atmospheric transport and deposition. Along with the old topic of OCPs, the study pointed out the preliminary understanding of CUPs pollution characteristic in surface soil of China, which provided a new story with the deep understanding of their environmental fate in both China and the world.

Polycyclic Aromatic Hydrocarbons in the Marine Atmosphere from the Western Pacific to the Southern Ocean: Spatial Variability, Gas/Particle Partitioning, and Source Apportionment.

The spatial variability of polycyclic aromatic hydrocarbons (PAHs) in the marine atmosphere contributes to the understanding of the global sources, fate, and impact of this contaminant. Few studies conducted to measure PAHs in the oceanic atmosphere have covered a large scale, especially in the Southern Ocean. In this study, high-volume air samples were taken along a cross-section from China to Antarctica and analyzed for gaseous and particulate PAHs. The data revealed the spatial distribution, gas-particle partitioning, and source contributions of PAHs in the Pacific, Indian, and Southern Oceans. The median concentration (gaseous + particulate) of ∑24PAHs was 3900 pg/m3 in the Pacific Ocean, 2000 pg/m3 in the Indian Ocean, and 1200 pg/m3 in the Southern Ocean. A clear latitudinal gradient was observed for airborne PAHs from the western Pacific to the Southern Ocean. Back trajectories (BTs) analysis showed that air masses predominantly originated from populated land had significantly higher concentrations of PAHs than those from the oceans or Antarctic continents/islands. The air mass origins and temperature have significant influences on the gas-particle partitioning of PAHs. Source analysis by positive matrix factorization (PMF) showed that the highest contribution to PAHs was from coal combustion emissions (52%), followed by engine combustion emissions (27%) and wood combustion emissions (21%). A higher contribution of PAHs from wood combustion was found in the eastern coastal region of Australia. In contrast, engine combustion emissions primarily influenced the sites in Southeast Asia.

Temporal Trend of Polycyclic Aromatic Hydrocarbons in Atmosphere: A Case Study within 24 h after Snowfall.

Based on air samples within 24 h after snowfall, gaseous and particulate concentrations of 16 priority PAHs were obtained, which provided a good opportunity to study the temporal trend of atmospheric PAHs. An obvious temporal trend with atmospheric concentration was observed, which was mainly influenced by emission sources. It was found that the maximum concentration (Σ16PAHs) was 272.8 ng/m3, appeared in the rush hour of traffic. To the contrary, the minimum concentration was 82.39 ng/m3 at the period with the least anthropogenic activities. The values of particle-phase fraction[Formula: see text]) and G/P partitioning quotient (log K P) were increased along with molecular weight of PAHs. However, for individual PAHs, the differences with [Formula: see text] and log K P were not obvious within 24 h. Furthermore, similar statistically significant positive correlations were found between log K P and log K OA among different periods. According to the short sampling program, chemical properties should be the major influencing factor for the temporal trend of G/P partitioning. The results of the case study provided new insights into the research field of G/P partitioning of PAHs.

Non-equilibrium influence on G/P partitioning of PAHs: Evidence from the diurnal and nocturnal variation.

Gas/particle (G/P) partitioning is an important behavior for the atmospheric transport of polycyclic aromatic hydrocarbons (PAHs). In this study, paired daytime and nighttime air samples were collected for one year in order to study the diurnal and nocturnal variations of concentration and G/P partitioning of PAHs. Higher PAHs concentrations in total phase were observed in nighttime. The geomean (GM) concentrations of Σ15PAHs in total phase were 69.6 and 52.8 ng/m3 in nighttime and daytime, respectively. More obviously diurnal and nocturnal variations were observed in non-heating season, with the GM ratios of Σ15PAHs in nighttime to daytime of 1.65 and 1.06 in non-heating season and heating season, respectively. The results could be attributed to emission sources and meteorological conditions. The values of particulate phase fraction (ϕP) and G/P partitioning quotient (log KP) were used to quantify the phase distribution of PAHs. For most high molecular weight PAHs, the values of ϕP and log KP in nighttime were higher than those in daytime, which could be mainly attributed to the lower temperature in nighttime. However, for the three light molecular weight PAHs (Acy, Ace and Flu), higher values of ϕP and log KP were observed in daytime. The regression of log KP against log KOA for the three PAHs in daytime differed from those in nighttime. The chemical losses of PAHs in different phases might be responsible for the result. These findings suggested that the chemical loss of PAHs in gas phase should be considered for the G/P partitioning process.

Recent advances and trends of trichloroethylene biodegradation: A critical review.

Trichloroethylene (TCE) is a ubiquitous chlorinated aliphatic hydrocarbon (CAH) in the environment, which is a Group 1 carcinogen with negative impacts on human health and ecosystems. Based on a series of recent advances, the environmental behavior and biodegradation process on TCE biodegradation need to be reviewed systematically. Four main biodegradation processes leading to TCE biodegradation by isolated bacteria and mixed cultures are anaerobic reductive dechlorination, anaerobic cometabolic reductive dichlorination, aerobic co-metabolism, and aerobic direct oxidation. More attention has been paid to the aerobic co-metabolism of TCE. Laboratory and field studies have demonstrated that bacterial isolates or mixed cultures containing Dehalococcoides or Dehalogenimonas can catalyze reductive dechlorination of TCE to ethene. The mechanisms, pathways, and enzymes of TCE biodegradation were reviewed, and the factors affecting the biodegradation process were discussed. Besides, the research progress on material-mediated enhanced biodegradation technologies of TCE through the combination of zero-valent iron (ZVI) or biochar with microorganisms was introduced. Furthermore, we reviewed the current research on TCE biodegradation in field applications, and finally provided the development prospects of TCE biodegradation based on the existing challenges. We hope that this review will provide guidance and specific recommendations for future studies on CAHs biodegradation in laboratory and field applications.

Prediction of the gas/particle partitioning quotient of PAHs based on ambient temperature.

Gas/particle (G/P) partitioning is an important influencing factor for the environmental fate of semi-volatile organic compounds (SVOCs). The G/P partitioning of polycyclic aromatic hydrocarbons (PAHs) is an integrated complex process due to its formation and growth concurrently with particles. Based on the large dataset of gaseous and particulate samples in a wide ambient temperature range of 50 °C, the simple empirical equations based on ambient temperature were established to predict the G/P partitioning quotient (KP) of PAHs at the temperature range from 252 K to 307 K (-21 °C to 34 °C). The performance of the empirical equations was validated by comparison with the monitoring KP of PAHs worldwide. The empirical equations exhibited good performance for the prediction of KP of PAHs based on ambient temperature. Two deviations with the prediction lines of the previous G/P partitioning models from the monitoring data of KP were observed. It was found that the deviations might be attributed to some non-considered influencing factors with the previous G/P partitioning prediction models. Therefore, further research should be conducted to study the mechanism of the G/P partitioning of PAHs, and more influencing factors should be introduced into the establishment of G/P partitioning models of PAHs. In summary, the result of the present study provided a convenient method for the prediction of KP of PAHs, which should be useful for the study of environmental fate of PAHs in atmosphere.

[Temporal Trend of Polycyclic Aromatic Hydrocarbons in Atmosphere Within 24 Hours After Snowfall].

The atmosphere is a significant medium for the transportation and diffusion of volatile and semi-volatile pollutants. Furthermore, the atmosphere is the primary exposure route for pollutants to enter the human body. Therefore, the study of the environmental fate of pollutants in the atmosphere is essential. In this study, 16 polycyclic aromatic hydrocarbons (PAHs) were analyzed in snow samples and air samples within 24 hours after a snowfall, and the temporal trend of PAHs in the atmosphere was comprehensively studied. The results indicated that the detection rate of the 16 PAHs in snow was 100%, and the concentration of phenanthrene (538.3 ng·L-1) was the highest, followed by naphthalene (509.1 ng·L-1) and fluoranthene (429.9 ng·L-1), indicating that snowfall can remove PAHs from the atmosphere. After the snowfall, a falling-rising-falling temporal trend of the concentrations of PAHs in the atmosphere was observed. Higher concentrations appeared during rush hour, with the largest automobile exhaust emissions, while lower concentrations appeared during periods with the lowest human activity. The results indicated that the atmospheric concentrations of PAHs were predominantly influenced by human activities. Within 24 hours after snowfall, the ratio of PAHs between the gas phase and particle phase, which depends primarily on the physical and chemical properties of PAHs, had not changed substantially. The diagnostic ratios indicated that within 24 hours after snowfall, the PAHs in the atmosphere originated mostly from the emissions of solid fuel and liquid fuel combustion.

PAHs in Chinese atmosphere Part II: Health risk assessment.

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous pollutants in atmosphere, which attracted more attentions due to their influence on human health. In this study, a national scale cancer risk (CR) assessment with atmospheric PAHs were conducted based on one year monitoring program at 11 cities across China. The annual mean concentrations of benzo[a]pyrene (BaP) and BaP equivalency (BaPeq) were 4.56 ± 7.78 ng/m3 and 8.45 ± 14.1 ng/m3, respectively, which were both higher than the new ambient air quality standards of China (GB 3095-2012, 1 ng/m3). Concentrations of BaP and BaPeq in northern Chinese cities were almost 2 times higher than those in southern Chinese cities. The CR values induced by the dermal contact exposure were two orders of magnitude higher than that by the inhalation exposure. Children and adults were the most sensitive age groups with the dermal contact exposure and the inhalation exposure to atmospheric PAHs, respectively. For the total CR values, 99.7% of its values were higher than the reference level of 10-6. No significant difference of the total CR values was observed between northern Chinese and southern Chinese cities for children and adults. In order to quantify the uncertainties of CR assessment, Monte Carlo Simulation was applied based on the specific distributions of the exposure factors cited from the Exposure Factors Handbook of Chinese Population. The results indicated that almost 90% probability of the total CR values were higher than 10-6, indicating potential cancer risk. Sensitive analysis indicated that atmospheric concentration, outdoor exposure fraction, particle amount adhered to skin, and cancer slope factor should be carefully considered in order to increase the accuracy of CR assessment with PAHs in atmosphere.

Gas/particle partitioning of PAHs based on equilibrium-state model and steady-state model.

The gas/particle (G/P) partitioning (KP) behavior is an important factor for the environmental fate of PAHs in atmosphere. Based on large database of log KP, equilibrium-state and steady-state models were applied for the comprehensive study with the G/P partitioning of PAHs, including the Harner-Bidleman (H-B) model, the Dachs-Eisenreich (D-E) model, and the Li-Ma-Yang (L-M-Y) model. For different sites, the trend of regression between log KP and log KOA was same, however, the slopes and intercepts were different. No obvious difference was observed between northern Chinese cities and southern Chinese cities. For congeners and aromatic rings of PAHs, the difference was much more obvious for the regressions, slopes and intercepts. The prediction of the D-E model and the H-B model matched well for the regression of the 4-rings and 5-rings PAHs, with >80% of monitoring data points in the range of ±1 log unit. The L-M-Y model only predicted well with the measurement for 4-rings PAHs with special values of log KOA. For different ranges of log KOA, the difference with the regression between log KP and log KOA was also obvious. Compared with our measurement, if 1 order of magnitude difference with log KP values between prediction and measurement was considered, the H-B model, the D-E model and the L-M-Y model can be only used when the log KOA in the ranges from 7.65 to 13.7, 6.88 to 13.5, and 7.65 to 11.7, respectively. Therefore, further studies with prediction models should be conducted for the G/P partitioning of PAHs. The results of this study provided new insights into the research field of the G/P partitioning of SVOCs.

PAHs in Chinese atmosphere: Gas/particle partitioning.

The gas/particle (G/P) partitioning behavior is an important factor for the environmental fate of polycyclic aromatic hydrocarbons (PAHs) in atmosphere. Based on one year monitoring program at 11 urban sites across China, 7647 pairs of gaseous and particulate concentrations were obtained for 16 priority PAHs, which provided a good opportunity to study the G/P partitioning behavior of PAHs. The concentrations of PAHs in both gas and particle phases were not in the same level among the 11 sites with a difference of more than one orders of magnitude. Along with the increase of molar weight of PAHs, the proportion of concentration in particle phase was increasing. In particle phase, the concentrations of ∑16PAHs in northern Chinese cities were significantly (p < 0.05) higher than those in southern Chinese cities with the average concentrations of 83.4 ±â€¯151 ng/m3 and 33.4 ±â€¯45.5 ng/m3, respectively. However, non-significant difference was found with ∑16PAHs in gas phase. The values of log KP (the G/P partitioning coefficient/quotient) ranged from -5.65 m3/µg to 2.34 m3/µg, with the mean value of -2.01 ±â€¯1.65 m3/µg for the 16 PAHs. The values of log KP for individual PAHs at the 11 sites were not in the same level. Furthermore, significant difference (p < 0.05) with log KP of the 16 PAHs was found between northern Chinese cities and southern Chinese cities except for Acy, Flu and DahA. More than one orders of magnitude difference with KP were observed for different congeners and different rings PAHs, which are mainly caused by their physical-chemical properties. The results of this study provided large database of KP, which is necessary and important to the research field of the G/P partitioning of PAHs.

Concentrations and fate of parabens and their metabolites in two typical wastewater treatment plants in northeastern China.

Parabens are widely used in food, pharmaceuticals, and personal care products because they are excellent preservatives. Recently, the environmental fate of parabens has attracted attention owing to their similarity to some endocrine disrupters. Wastewater treatment plants (WWTPs) are both important sinks of parabens discharged from our daily activities and key pollution sources for the environment if the parabens are not completely removed. However, research in this area is scarce, especially in Asia. In this study, 6 commonly used parabens and 4 metabolites were analyzed in wastewater and sludge samples from two typical WWTPs with different treatment processes (the anaerobic-oxic (A/O) and cyclic activated sludge technology (CAST) treatment processes). The average concentrations of parabens in the A/O and CAST treatment processes were 1510 ng/L and 2180 ng/L, respectively, in the influent, and 70.5 ng/L and 19.7 ng/L, respectively, in the effluent. The paraben removal efficiencies in the A/O treatment process were between 56.8% and 100%, which is lower than the efficiencies for the CAST treatment process (97.7% to 100%). The average concentrations of metabolites in the A/O treatment process, which were much higher than paraben concentrations, were 35,200 ng/L in the influent, 334 ng/L in the effluent, and 146 ng/g in the sludge samples. The removal efficiencies for the 4 metabolites were >92% for the A/O treatment process. In total, for the A/O treatment process, 5.07 kg and 16.8 kg of parabens, and 24.4 kg and 16.0 kg of metabolites, were discharged into the environment annually via effluent and sludge, respectively. Overall, the results of this study indicate that the A/O and CAST treatment processes are both effective at removing parabens and their metabolites.

[Pollution Characteristics of Parabens in Typical Sewage Wastewater].

Parabens are widely used in foodstuffs, cosmetics, and pharmaceuticals as preservatives, fungicides, and bactericides. Recent studies showed that these compounds could be detected in surface water and are a potential hazard to the aquatic ecological environment. In this study, 24-hour influent samples were collected from a typical sewage wastewater treatment plant in Harbin in autumn and winter in 2016. The concentrations of six parabens and four normal water quality parameters were analyzed. The results indicated that parabens were frequently detected in the influent, and MeP, EtP, and PrP were the predominant compounds. Significant correlations were found between TOC, TDS, pH, and the concentration of parabens. The concentration of parabens in the influent of the sewage wastewater treatment plant have obvious daily variations rather than seasonal variations. The results provide an important theoretical basis for further research and pollution control of parabens in sewage wastewater treatment system.

Removal characteristic of surfactants in typical industrial and domestic wastewater treatment plants in Northeast China.

Surfactants are widely used in household and industrial products for cleaning and/or solubilization in our daily life. Therefore, they are finally discharged into wastewater treatment plants (WWTPs), which may be the major point pollution source for environment if they were not completely removed during wastewater treatment. In this study, two typical industrial and domestic WWTPs with different wastewater treatment technologies were considered for the topic. Totally, two types of surfactants were analyzed in 24 h influent and each processing unit effluent. Four linear alkylbenzene sulfonates (LASs) with the alkyl chain from C10 to C13, and two benzalkonium chlorides (BACs) with the alkyl chain of C12 and C14 were selected as target compounds. The total concentrations of LASs in influent varied from 19.2 to 1889 µg/L and LAS-C11 and LAS-C12 were the predominant compounds with the concentration from 6.01 to 641 µg/L and 8.02-674 µg/L, respectively. The total concentrations of BACs were much lower than those of LASs, with the concentration ranging from 0.00935 to 1.85 µg/L. Significant positive correlations were observed between concentrations of LASs and BACs in influent, indicating their same and/or similar sources. Compared with the concentration of influent, the concentration of effluent was much lower, indicating the high removal efficiency by the two wastewater treatment processes. Biological treatment unit and cyclic activated sludge system were the main treatment units for the removing of surfactants, which suggested that these two types of surfactants can be easily degraded under aerobic condition. Seasonal variation indicated that the removal efficiencies of surfactants in autumn were a little higher than those in winter. The results of this study provided new insights into the environmental fate of surfactants in wastewater treatment system.

Occurrence and fate of benzotriazoles UV filters in a typical residential wastewater treatment plant in Harbin, China.

Benzotriazoles (BTs) UV filters are widely used as ultraviolet absorbents for our daily products, which received increasing attention in the past decades. Residential wastewater treatment plant (WWTP) is both an important sink for wastewater and a key pollution source for receiving water for these chemicals. In this study, pretreatment and gas chromatography-tandem mass spectrometry analysis method were developed to determine the occurrence and fate of 9 BTs UV filters in wastewater and sludge from the WWTP with anaerobic-oxic treatment process (A/O) and biological aerated filter treatment process (BAF). Totally, 81 wastewater samples and 11 sludge samples were collected in four seasons. In wastewater, UV-326 and UV-329 were frequently detected, while the highest mean concentrations were detected for UV-234 and UV-329. The concentrations were in the range of 85% in A/O process and 60-77% in BAF process except for UV-350, which was more difficult to remove with lower removal efficiencies of 33.3% for both A/O and BAF. All the target chemicals except for UV-320 were detected in sludge samples with the mean concentration ranging from 0.90 ng/g to 303.39 ng/g. There was no significant difference with concentrations and removal efficiency among different seasons. Higher detection frequency and concentration of BTs UV filters in downstream of the receiving water system indicated the contribution of effluent of the WWTP. Compared with other rivers, the lower concentrations in surface water in the Songhua River indicated light pollution status with of BTs UV filters.