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Abstract: This study aims at the remediation of heavily PAH-contaminated soil containing 375mg of total PAHs per kilogram dry soil. Pilot scale bioremediation experiments were carried out by three approaches with contaminated soil from abandoned sites of Beijing Coking Plant using outdoor pot trials. The first approach was bioaugmentation with a bacterial strain which degrades PAH and produces bioemulsifier, the second approach comprised of biostimulation of indigenous microorganisms with supplementing nutrients and the last approach involved the combination of both biostimulation and bioaugmentation. An on-site land farming group was set as a control in which the total PAHs and 4–6 ring-PAHs were reduced by 23.4% and 10.1%, respectively after 175 days. Meanwhile, in the first approach group, the total PAHs and 4–6 ring-PAHs were reduced by 26.82% and 35.36%, respectively; in the second approach group both percentages were 33.9% and 11.0%, respectively; while in the third approach group, these pollutants were reduced by 43.9% and 55.0%, respectively. The results obtained suggested that biostimulation and bioaugmentation combined could significantly enhance the removal of PAHs in the contaminated soil. [Copyright &y& Elsevier]

Environmentally persistent free radicals (EPFRs) are a type of emerging contaminants. The EPFR species in airborne particulate matter are similar to carcinogenic tar paramagnetic species in cigarettes that can cause DNA damage. However, understanding on daily EPFR exposure levels and risks are lacking currently. We used personal aerosol exposure monitors worn by volunteers to assess EPFR exposure in a spatio-temporal, non-static manner. Daily individual exposure to EPFRs for urban residents in Beijing, China ranged from 1.11 × 1017 to 7.42 × 1017 spins/m3 during the heating period (winter) and from 4.79 × 1014 to 7.76 × 1016 spins/m3 during the non-heating period (summer). Carbon-centered radicals were dominant in winter, while oxygen-centered radicals were dominant in summer because of higher atmospheric oxidizing capacity contributing to oxidation reactions. Coal combustion in winter is a key influencing factor in EPFR exposure levels. An intuitional assessment was used to evaluate the inhalation risks of EPFRs by converting their concentrations in inhaled particulate matter to equivalents in cigarettes smoked. The assessment concluded that one urban resident may, on average, inhale the equivalent of 46 cigarettes per day in EPFRs. The health risks of these free radicals, especially during winter, should be researched in depth. ga1 • Personal aerosol exposure monitors were applied to mimic human inhalation. • Chemical characteristics of inhaled EPFRs were clarified. • Influencing factors of EPFRs in particulate matter were clarified. • An intuitional assessment method of EPFRs exposure risks was established. [ABSTRACT FROM AUTHOR]

The spatial interactions in a city help us understand how the city spaces are structured. Human needs change constantly throughout the day, leading to changing functions of urban space and spatial interactions. Most existing studies on spatial interaction are confined to static interaction, which does not reflect the dynamic spatial interactions and urban space functions. Taxies are an important means of urban transportation, and their trajectories are time sensitive. The clusters of pick-up and drop-off points of taxies directly reflect the spatiotemporal human mobility pattern in a city, and their implicit semantic information can be used to infer the passengers' activities. Using Beijing as a case study, this paper employs taxi origin and destination trajectory data to explore the dynamic spatial and functional interaction patterns. First, we apply tensor decomposition to obtain the spatial and temporal patterns of human mobility. Second, geotagged Weibo texts are incorporated to extract the dynamic urban functional areas. Then, we obtain the spatial and functional interactions by trajectory clustering and visualization. The results reveal two daily patterns and four hourly patterns of human mobility. The spatial interactions and the functional interaction reveal the spatial patterns and semantics of human taxi travel behaviors in different time periods. • Explore dynamic spatial and functional interactions in a city with crowdsourced data. • Find spatiotemporal patterns in OD trajectories with a tensor decomposition method. • Use geotagged texts to extract dynamic urban functional areas with topic model. • Cluster trajectories based on their spatial adjacency and semantics. • Identify spatial and functional interactions in Beijing city. [ABSTRACT FROM AUTHOR]

Profiles, sources and potential exposures of chlorinated and brominated polycyclic aromatic hydrocarbons (ClPAHs and BrPAHs) in haze associated atmosphere remain unclear. Haze events happened frequently during heating period in Beijing provided a typical urban context to investigate the concentrations, profiles, sources and potential exposures of ClPAHs, BrPAHs and their non-halogenated parent compounds (PAHs) in air samples. Average concentrations of PAHs, ClPAHs and BrPAHs during heating periods (with more frequent haze events) were about 3–9 times higher than during non-heating periods. Concentrations of particulate matter (PM)-associated ClPAHs and BrPAHs were higher in heating period than in non-heating period, while for gas-associated ClPAHs and BrPAHs, this distinction was not significant. Congener patterns and congener profiles indicated that with increasing coal combustion during the heating period, concentrations of PAHs and ClPAHs in air were elevated in comparison to the non-heating period. Inhalation of PM-associated PAHs, ClPAHs and BrPAHs accounted for higher exposure than inhalation of gas phase and dermal contact of both gas phase and particulate phase. In this study we found that the particulate phase is the dominant exposure pathway of atmospheric PAHs, ClPAHs and BrPAHs during haze days, which is different from previous studies. [ABSTRACT FROM AUTHOR]