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Mineral scale refers to the hard inorganic solids nucleated on substrates or deposited from the aqueous phase. The formation and deposition of barium sulfate and strontium sulfate in various industries, such as water treatment and oilfield operations, can significantly impact facility operations, posing serious threats. Machine learning (ML) approaches have been adopted recently in scale threat predictions to address the limitations of conventional scaling prediction models. However, there are few reports on collecting sulfate mineral scaling data, employing ML methods for data analysis, and evaluating the modeling results to gain deeper insights of sulfate mineral scaling process and to improve the accuracy of sulfate scaling threat prediction. Despite comprehensive experimental studies, the literature does not provide adequate guidance for identifying the influence on the solubility of barium sulfate and strontium sulfate under different aqueous environments and actual operating conditions. To this end, this study collected 1600 experimental datasets of barium/strontium sulfate from the literature to construct and evaluate the reliability and versatility of a ML-based model for sulfate solubility calculations. Single neural networks, hybrid neural networks, and optimization algorithms were employed to build solubility prediction models for barium sulfate and strontium sulfate across a wide range of temperatures, pressures, and different ions. The model's applicability in predicting sulfate scaling threats in various actual operating environments demonstrated its broad usability, consistent with its actual performance. This study marks the first stride towards constructing a reliable model for identifying the scaling trends of barium sulfate and strontium sulfate across various operating conditions, underscoring the importance of developing robust and accurate prediction models to address challenges in various industrial systems. [Display omitted] • Utilize multiple hybrid neural networks to establish sulfate solubility model. • Employ novel optimization algorithms to enhance model performance. • MLP-POA model exhibits the highest accuracy in prediction capabilities. • Impurity ion concentrations have the most significant impact on sulfate solubility. • This model can predict sulfate scaling threats in various operating environments. [ABSTRACT FROM AUTHOR]

The effects of natural organic matter (NOM) types and electrolyte ions are crucial to the aggregation of ferrihydrite nanoparticles (Fh NPs) in the environment. Dynamic light scattering (DLS) was employed for the aggregation kinetics of Fh NPs (10 mg/L as Fe) in the present study. The critical coagulation concentration (CCC) values of Fh NPs aggregation in NaCl were obtained in the presence of 15 mg C/L NOM as SRHA (857.4 mM) > PPHA (752.3 mM) > SRFA > (420.1 mM) > ESHA (141.0 mM) > NOM-free (125.3 mM), indicating Fh NPs aggregation was inhibited as the above order. Comparatively in CaCl 2 , the CCC values were measured in ESHA (0.9 mM), PPHA (2.7 mM), SRFA (3.6 mM), SRHA (5.9 mM), NOM-free (76.6 mM), implying NPs aggregation was enhanced following the order of ESHA > PPHA > SRFA > SRHA. To investigate the dominant mechanisms, the aggregation of Fh NPs was comprehensively studied under the effects of NOM types, concentrations (0–15 mg C/L) and electrolyte ions (NaCl/CaCl 2 beyond CCC). In NaCl/CaCl 2 , the low concentration of NOM (<7.5 mg C/L) could accelerate NPs aggregation mainly due to patch-charge attraction. When NOM concentration was high (> 7.5 mg C/L), the inhibition effect on NPs aggregation occurred in NaCl due to steric repulsion, whereas the enhancement effect in CaCl 2 of aggregation was dominated by the bridging effect. The results indicated that the effects of NOM types, concentration and electrolyte ions should be carefully considered for the environmental behavior of NPs. [Display omitted] • NOM types (SRHA/PPHA/SRFA/ESHA) posed different impacts on Fh NPs aggregation. • Electrolytes (NaCl/CaCl 2) posed different impacts on Fh NPs aggregation. • NOM enhanced NPs aggregation at low conc. Due to patch charge in NaCl/CaCl 2. • NOM at high conc. (15 mg C/L) inhibited aggregation in NaCl by steric repulsion. • NOM enhanced aggregation at high conc. in CaCl 2 by bridging effect. [ABSTRACT FROM AUTHOR]

Silica aerogel, with mesoporous structure and high hydrophobicity, is a promising adsorbent for oil spill clean-up. To make it economic and environmental-friendly, hydrocarbon desorption and silica aerogel regeneration were investigated. After hydrocarbon desorption at 80 °C, silica aerogel maintained its hydrophobicity. After toluene, petrol, and diesel desorption, shrinkage of mesopores (from 19.9 to 16.8, 13.5, and 13.4 nm) of silica aerogels occurred, causing decreased adsorption capacities (from 12.4, 11.2, and 13.6 to 12.0, 6.5, and 2.3 g/g). Low surface tension of petrol caused high stress on mesopores during its desorption, resulting in significant pore shrinkage. For diesel, its incomplete desorption and oxidation further hindered the regeneration. Therefore, diesel desorption was also conducted at 200 °C. Severe diesel oxidation occurred under aerobic condition and destroyed the mesopores. Under anaerobic condition, no diesel oxidation occurred and the decreases in pore size (to 13.2 nm) and adsorption efficiency (to 10.0 g/g) of regenerated silica aerogels were much less, compared with under aerobic condition. This study provided new insights on silica aerogel regeneration for oil spill clean-up. [ABSTRACT FROM AUTHOR]

For safer geologic CO 2 sequestration (GCS), it is important to understand CO 2 -brine-cement interactions, which affect wellbore integrity. However, potential effects of sulfate and magnesium ions on cement degradation under GCS conditions are not well understood. Here Class H Portland cement were reacted in brines containing 0.05 M sulfate and/or magnesium ions under both GCS (50 °C and 100 atm CO 2 ) and control (50 °C and atmospheric pressure) conditions. Using optical microscopy and scanning electron microscope coupled with energy dispersive spectrometry and electron back scattered electron (SEM-EDS/BSE), slower cement carbonation rates were observed in the presence of sulfate under GCS conditions, because of gypsum precipitation on cement surfaces. Calcite rather than gypsum formed in both the inner layers of cement samples reacted under GCS conditions, and on cement surfaces reacted under atmospheric pressure conditions. Under GCS conditions, the dissolved CO 2 lowered the pH of the solution surrounding cement surfaces, thus favoring the formation of gypsum over calcite on cement surfaces; while the high pH condition in pore solution inside cement favors the formation of calcite over gypsum. The presence of magnesium had no significant effect on cement degradation under GCS conditions, as brucite, magnesium carbonates and magnesium calcite did not form, due to the low pH at cement surface and the limited diffusion of Mg into cement inner layers. [ABSTRACT FROM AUTHOR]

The fluorine content of coal has been well documented, while such data of coal spoil are limited. In the present paper, fluorine in coal spoils and its releasing behavior were studied via leaching and combustion tests, as well as field investigation. Fluoride pollution in groundwater and soil occurred in the air depositing areas of coal spoils. The average content of fluorine in coal spoils was 525 mg/kg with the highest value of 1885 mg/kg. The only XRD detectable inorganic fluorine phase was fluorphlogopite. The absence of major fluorine bearing minerals in coal spoils suggested that bulk fluorine, rather than trace phases, resided in the mineral matrix. The major extracted species were water soluble fluorine and exchangeable fluorine in the coal spoils. Batch leaching tests illustrated that the leachable fluoride in coal spoils was widely distributed, ranging from 2.0 to 108.4 mg/kg. Column leaching tests showed a clear pH-dependent leaching behavior of fluorine: lower pH situation led to fluorine release from the mineral matrix; the loosely bound or easily exchangeable fluorine was also flushed out of the column. The higher ion strength or alkaline bicarbonate/carbonate rich leaching solution tended to free more fluorine into the acidic aqueous solution. The leachable fluorine in coal spoils was estimated as ca. 6%, based on the results of leaching tests. Also, our research found that over 90% of fluorine in coal spoils could be released into the atmosphere as a result of spontaneous combustion, accounting for over 40% of the total atmospheric fluorine emissions in northern China. Our investigation suggests that it is urgent to conduct comprehensive studies to assist the management and control of fluorine pollution at coal spoil banks. [ABSTRACT FROM AUTHOR]

• Latest development in mechanism and control of sulfate mineral scaling is presented. • Sulfate molecular interfacial reactions and thermodynamic basis are discussed. • Bridging knowledge in interfacial chemistry with engineering practice is conducted. • New insights in nucleation and growth mechanisms and kinetics are summarized. • Future research on inhibitor design and surface modifications is highlighted. Sulfate scaling, as insoluble inorganic sulfate deposits, can cause serious operational problems in various industries, such as blockage of membrane pores and subsurface media and impairment of equipment functionality. There is limited article to bridge sulfate formation mechanisms with field scaling control practice. This article reviews the molecular-level interfacial reactions and thermodynamic basis controlling homogeneous and heterogeneous sulfate mineral nucleation and growth through classical and non-classical pathways. Common sulfate scaling control strategies were also reviewed, including pretreatment, chemical inhibition and surface modification. Furthermore, efforts were made to link the fundamental theories with industrial scale control practices. Effects of common inhibitors on different steps of sulfate formation pathways (i.e., ion pair and cluster formation, nucleation, and growth) were thoroughly discussed. Surface modifications to industrial facilities and membrane units were clarified as controlling either the deposition of homogeneous precipitates or the heterogeneous nucleation. Future research directions in terms of optimizing sulfate chemical inhibitor design and improving surface modifications are also discussed. This article aims to keep the readers abreast of the latest development in mechanistic understanding and control strategies of sulfate scale formation and to bridge knowledge developed in interfacial chemistry with engineering practice. [Display omitted] [ABSTRACT FROM AUTHOR]

In China, traffic policemen have to stand for several hours a day at the road intersections with high vehicle flows. To assess their exposure to airborne carcinogenic polycyclic aromatic hydrocarbons (PAHs) during their working time, a preliminary study was conducted to measure the personal exposure level to PAHs. And a probabilistic incremental lifetime cancer risk (ILCR) model together with the benzo[a]pyrene (BaP) toxic equivalents (BaPeq) method was used to conduct health risk assessment. Personal exposure monitors (PEM) were carried by traffic policemen to collect PM10 samples during their daily work in Tianjin, China. Meanwhile, PM100 samples were collected at the roadsides and on campus of Nankai University as comparison. PAHs species were quantitatively analyzed by GC/MS. Experimental results showed that the concentrations of total PAHs, BaP and BaPeq were much higher at the road intersections (867.5, 26.2, 82.4 ng m−3), where the traffic policemen stand during their work time, than those at the roadsides (46.6, 1.5, 5.7 ng m−3), and on campus (19.5, 0.7, 2.4 ng m−3). According to the risk assessment results, the occupational risk falls within the range from 10−6 to 10−3. On the basis of sensitivity analysis results, further research should be directed to give better characterization of the yearly concentration distribution of PAHs and the cancer slope factor (CSF) of BaP in order to improve the accuracy of the health risk assessment. [Copyright &y& Elsevier]

Abstract D-amino acid (DAA) an environmentally friendly biofilm inhibitor, has low efficiency for membrane biofouling control due to its instability. To address this challenge, a novel nanocomposite was prepared with DAA adhering to polydopamine (PDA)-coated halloysite nanotube (HNTs) through the interactions of H-bonding and π-π stacking between PDA and DAA. Membrane modified with such nanocomposite was fabricated via blending phase inversion, and the nanocomposite was uniformly distributed in the modified membrane matrix. In comparison with the pristine membrane, the addition of nanocomposites resulted in robust mechanical property for modified membrane with the ultimate stress and strain increased by 23.97% and 35.62%, respectively. Moreover, an excellent tradeoff between water flux (2.5 folds of pristine membrane) and selectivity was achieved, probably due to the improved membrane hydrophilicity. Meanwhile, bovine serum protein (BSA) static adsorption as well as dynamic filtration experiments exhibited excellent antifouling ability of the modified membrane. Most importantly, a superior anti-biofouling stability over a 10-day period was obtained for the membrane modified with nanocomposite, indicating that the activity of DAA to mitigate biofouling was effectively maintained. This study developed a novel and promising strategy for membrane biofouling mitigation. Graphical abstract Image 1 Highlights • A new D-amino acid/polydopamine/halloysite nanotube nanocomposite was synthesized. • A novel nanocomposite-modified membrane was fabricated. • D-amino acid supported on PDA and HNTs effectively mitigated membrane biofouling. • The improved filtration and anti-fouling performances of the modified membrane were obtained. [ABSTRACT FROM AUTHOR]

Abstract: Early stage amorphous precursors provide a low energy pathway for carbonate mineralization. Many natural deposits of carbonate minerals and biogenic calcium carbonate (both amorphous and crystalline) include significant amounts of Mg. To understand the role of magnesium-containing amorphous precursors in carbonate mineralization, we investigated the energetics and structure of synthetic amorphous Ca–Mg carbonates with composition Ca1− x Mg x CO3·nH2O (0⩽ x ⩽1) using isothermal acid solution calorimetry and synchrotron X-ray scattering experiments with pair distribution function (PDF) analysis. Amorphous magnesium carbonate (AMC with x =1) is energetically more metastable than amorphous calcium carbonate (ACC with x =0), but it is more persistent (crystallizing in months rather than days under ambient conditions), probably due to the slow kinetics of Mg2+ dehydration. The Ca1− x Mg x CO3·nH2O (0⩽ x ⩽1) system forms a continuous X-ray amorphous series upon precipitation and all intermediate compositions are energetically more stable than a mixture of ACC and AMC, but metastable with respect to crystalline carbonates. The amorphous system can be divided into two distinct regions. For x =0.00–0.47, thermal analysis is consistent with a homogeneous amorphous phase. The less metastable compositions of this series, with x =0.0–0.2, are frequently found in biogenic carbonates. If not coincidental, this may suggest that organisms take advantage of this single phase low energy amorphous precursor pathway to crystalline biogenic carbonates. For x ⩾0.47, energetic metastability increases and thermal analysis hints at nanoscale heterogeneity, perhaps of a material near x =0.5 coexisting with another phase near pure AMC (x =1). The most hydrated amorphous phases, which occur near x =0.5, are the least metastable, and may be precursors for dolomite formation. [Copyright &y& Elsevier]

Abstract Seawater reverse osmosis (SWRO) is a commonly used desalination technique owing to its lesser environmental and economic impacts as compared to thermal desalination techniques. Antiscalants are used in SWRO to reduce membrane scaling caused by the supersaturation of salts present in feed water. However, to remain effective in reducing membrane scaling, antiscalants should be highly stable and resistant to biological degradation by seawater microorganisms. In this research, several bacteria from Qatar's seawater were isolated and screened for their ability to use antiscalants as a carbon and energy source. The biodiversity of antiscalant degrading seawater bacteria was demonstrated through combining the techniques of MALDI-TOF MS and principle component analysis. It was found that the bacteria isolated from Qatar's seawater such as H. aquamarina, H. elongata, P. fragi, P. stutzeri and others can degrade antiscalants and use them as a carbon and energy source. It was observed that the growth rates varied based on the type of antiscalant and the bacteria used. Among the tested strains, H. aquamarina, which is also known for its potential to cause biofouling, demonstrated the highest growth rates in antiscalants media. Thus, it was concluded that there is wide variety of bacteria in Qatar's seawater that can biodegrade the antiscalants; reducing their efficiency to combat membrane scaling. Since, these antiscalants will be used as a source of carbon and energy, microbial growth will increase resulting in enhanced membrane biofouling in SWRO. Graphical abstract Unlabelled Image Highlights • Antiscalants are commonly used to reduce scaling in seawater reverse osmosis. • The antiscalants are prone to enhance membrane biofouling. • There is a biodiversity of seawater bacteria that can biodegrade antiscalants. • Bacterial biodiversity can be explored through combining MALDI-TOF MS with PCA. • The specific growth rates vary with the type of bacteria and antiscalants. [ABSTRACT FROM AUTHOR]

Calcite precipitation plays a significant role in processes such as geological carbon sequestration and toxic metal sequestration and, yet, the rates and mechanisms of calcite growth under close to equilibrium conditions are far from well understood. In this study, a quartz crystal microbalance with dissipation (QCM-D) was used for the first time to measure macroscopic calcite growth rates. Calcite seed crystals were first nucleated and grown on sensors, then growth rates of calcite seed crystals were measured in real-time under close to equilibrium conditions (saturation index, SI = log ({Ca 2+ }/{CO 3 2− } /K sp ) = 0.01–0.7, where {i} represent ion activities and K sp  = 10 −8.48 is the calcite thermodynamic solubility constant). At the end of the experiments, total masses of calcite crystals on sensors measured by QCM-D and inductively coupled plasma mass spectrometry (ICP-MS) were consistent, validating the QCM-D measurements. Calcite growth rates measured by QCM-D were compared with reported macroscopic growth rates measured with auto-titration, ICP-MS, and microbalance. Calcite growth rates measured by QCM-D were also compared with microscopic growth rates measured by atomic force microscopy (AFM) and with rates predicted by two process-based crystal growth models. The discrepancies in growth rates among AFM measurements and model predictions appear to mainly arise from differences in step densities, and the step velocities were consistent among the AFM measurements as well as with both model predictions. Using the predicted steady-state step velocity and the measured step densities, both models predict well the growth rates measured using QCM-D and AFM. This study provides valuable insights into the effects of reactive site densities on calcite growth rate, which may help design future growth models to predict transient-state step densities. [ABSTRACT FROM AUTHOR]

The poor colloidal stability of magnetite nanoparticles (MNPs) limits their mobility and application, so various organic coatings (OCs) were applied to MNPs. Here, a comparative study on the colloidal stability of MNPs coated with acetic (HAc) and polyacrylic acids (PAA) was conducted under varied pH (5.0–9.0) in the presence of different concentrations of cations and anions, as well as humic acid (HA). Comparing the effects of various cations and anions, the stability of both HAc/PAA-MNPs followed the order: Na+ > Ca2+and PO 4 3− > SO 4 2− > Cl−, which could be explained by their adsorption behaviors onto HAc/PAA-MNPs and the resulting surface charge changes. Under all conditions even with more anion adsorption onto HAc-MNPs (0.14–22.56 mg/g) than onto PAA-MNPs (0.04–18.34 mg/g), PAA-MNPs were more negatively charged than HAc-MNPs, as PAA has a lower pH IEP (2.6 ± 0.1) than that of HAc (3.7 ± 0.1). Neither the HAc nor PAA coatings were displaced by phosphate even at considerably high phosphate concentration. Compared with HAc-MNPs, the stability of PAA-MNPs was greatly improved under all studied conditions, which could be due to both stronger electrostatic and additional steric repulsion forces among PAA-MNPs. Besides, under all conditions, Derjaguin-Landau-Verwey-Overbeek (DLVO) explained well the aggregation kinetic of HAc-MNPs; while extended DLVO (EDLVO) successfully predict that of PAA-MNPs, indicating steric forces among PAA-MNPs. The aggregation of HAc/PAA-MNPs was all inhibited in varied electrolyte solutions by HA (2 mg C/L) addition. This study suggested that carboxyl coatings with higher molecular weights and p K a values could stabilize MNPs better due to stronger electrostatic and additional steric repulsion. However, in the presence of HA, these two forces were mainly controlled by adsorbed HA instead of the organic pre-coatings on MNPs. [Display omitted] • OC-MNPs aggregated faster in Ca2+ than in Na + by stronger charge neutralization. • Anion adsorption onto HAc-MNPs were higher than that onto PAA-MNPs. • Electrostatic and van der Waals forces controlled the stability of HAc-MNPs. • PAA stabilized MNPs more than HAc due to stronger electrostatic and steric forces. • The stabilities of HAc/PAA-MNPs were similar after humic acid adsorption. [ABSTRACT FROM AUTHOR]

• The breakthrough of lead phosphate particles in sand columns was investigated. • Attachment in NaNO 3 was influenced by ripening, straining, and weak deposition. • Low P/Pb ratios enhanced the aggregation and deposition of lead phosphate particles. • Ca2+ promoted the aggregation and deposition of lead phosphate particles. • Humic acid enhanced the mobility of lead phosphate particles in porous media. Phosphate addition is commonly applied as an effective method to remediate lead contaminated sites via formation of low solubility lead phosphate solids. However, subsequent transport of the lead phosphate particles may impact the effectiveness of this remediation strategy. Hence, this study investigates the mechanisms involved in the aggregation of lead phosphate particles and their deposition in sand columns as a function of typical water chemistry parameters. Clean bed filtration theory was evaluated to predict the particle deposition behavior, using Derjaguin–Landau–Verwey–Overbeek (DLVO) theory to estimate particle-substrate interactions. The observed particle deposition was not predictable from the primary energy barrier in clean bed filtration models, even in simple monovalent background electrolyte (NaNO 3), because weak deposition in a secondary energy minimum prevailed even at low ionic strength, and ripening occurred at ionic strengths of 12.5 mM or higher. For aged (aggregated) suspensions, straining also occurred at 12.5 mM or higher. Aggregation and deposition were further enhanced at low total P/Pb ratios (i.e., P/Pb = 1) and in the presence of divalent cations, such as Ca2+ (≥ 0.2 mM), which resulted in less negative particle surface potentials and weaker electrostatic repulsion forces. However, the presence of 5 mg C/L of humic acid induced strong steric or electrosteric repulsion, which hindered particle aggregation and deposition even in the presence of Ca2+. This study demonstrates the importance of myriad mechanisms in lead phosphate deposition and provides useful information for controlling water chemistry in phosphate applications for lead remediation. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: Particle Exposure Assessment for Community Elderly (PEACE) in Tianjin, China was to characterize personal PM10 exposure, and provide data support for an epidemiological study investigating potential health effects of PM pollution on Chinese elderly population. In this study, a total of 80 elderly participants were recruited for a two-consecutive-day personal exposure measurement, and simultaneously residential indoor, residential outdoor and community PM10 were monitored in the summer and winter of 2009. Personal PM10 concentrations were 192.8 ± 100.6 μg m−3 in summer and 154.6 ± 105.4 μg m−3 in winter. Modeled personal exposures were less than measured personal exposures while a high coefficient of determination (R 2) of 0.71 was obtained. Based on measured and modeled exposures, a mean personal cloud of 30.2 μg m−3 was estimated in summer and 16.5 μg m−3 in winter. Moderate correlation emerged between personal and community PM10 concentrations in summer (r = 0.39), and stronger correlation was found in winter (r = 0.82). Analysis of variance (ANOVA) shown that smoking, cooking and cleaning activities did not produce significant effect on personal exposures. Further more, multivariate regression analysis performed in this study revealed that community PM10 level contributed most of personal PM10 exposure, 32% in summer and 64% in winter, respectively. The findings of this study indicated that PM10 personal exposures were considerably influenced by outdoor particulate matter rather than typical indoor sources, and ambient PM10 level measured at community monitoring sites may be used as a surrogate of personal exposure to PM10. [Copyright &y& Elsevier]

Abstract: Volatile Organic Compounds (VOCs) exposure can induce a range of adverse human health effects. To date, however, personal VOCs exposure and residential indoor and outdoor VOCs levels have not been well characterized in the mainland of China, less is known about health risk of personal exposure to VOCs. In this study, personal exposures for 12 participants as well as residential indoor/outdoor, workplace and in vehicle VOCs concentrations were measured simultaneously in Tianjin, China. All VOCs samples were collected using passive samplers for 5days and were analyzed using Thermal Desorption GC-MS method. U.S. Environmental Protect Agency''s Inhalation Unit Risks were used to calculate the inhalation cancer health risk. To assess uncertainty of health risk estimate, Monte Carlo simulation and sensitivity analysis were implemented. Personal exposures were greater than residential indoor exposures as expected with the exception of carbon tetrachloride. Exposure assessment showed modeled and measured concentrations are statistically linearly correlated for all VOCs (P <0.01) except chloroform, confirming that estimated personal exposure using time-weighted model can provide reasonable estimate of personal inhalation exposure to VOCs. Indoor smoking and recent renovation were identified as two major factors influencing personal exposure based on the time-activity pattern and factor analysis. According to the cancer risk analysis of personal exposure, benzene, chloroform, carbon tetrachloride and 1,3-butadiene had median upper-bound lifetime cancer risks that exceeded the U.S. EPA benchmark of 1 per one million, and benzene presented the highest median risks at about 22 per one million population. The median cumulative cancer risk of personal exposure to 5 VOCs was approximately 44 per million, followed by indoor exposure (37 per million) and in vehicle exposure (36 per million). Sensitivity analysis suggested that improving the accuracy of exposure measurement in further research would advance the health risk assessment. [Copyright &y& Elsevier]

Abstract: Nineteen road dust samples were collected during 2005 in different parts of the urban area of Anshan, Liaoning Province, China, and 11 polycyclic aromatic hydrocarbons (PAHs) species were quantitatively analyzed using GC–MS. The results indicated that the total average concentration of PAHs over the investigated sites ranged from 48.73 to 638.26μg/g, with a mean value of 144.25μg/g, higher than the concentrations measured in previous studies. PAHs concentrations were higher with high molecular weight homologues (4–6 rings PAHs), accounting for 83.24–96.98%, showing combustion of petroleum fuels was a potential source. Organic carbon in road dust was considered one of the important factors that influenced the concentrations of PAHs in this study, and it was found that concentrations of total PAHs were correlated with those of organic carbon in road dust. The results of diagnostic ratios analysis showed traffic emission (gasoline or diesel) was one of the most important sources of road dust PAHs. Principal component analysis (PCA) indicated that the major sources of road dust PAHs might be emission from traffic, steel industry, cooking and coal combustion. [Copyright &y& Elsevier]

Reverse osmosis (RO) technology is promising in the sustainable production of fresh water. However, expansion of RO use has been hindered by membrane fouling, mainly inorganic fouling known as scaling. Although membrane mineral scaling by chemical means have been investigated extensively, mineral scaling triggered by microbial activity has been largely neglected. In this study, the simultaneous biomineralization of CaCO 3 and CaSO 4 in the presence of three different microbial communities from fresh water, wastewater, and seawater was investigated. In the presence of either 13 or 79 mM of Ca2+ and SO 4 2- in the media, the fresh water microbial community produced calcite/vaterite and vaterite/gypsum, respectively; the wastewater community produced vaterite and vaterite/gypsum, respectively; and the seawater community produced aragonite in both conditions. The results showed that the concentration of salts and the microbial composition influence the types of precipitates produced. The mechanisms of crystal formation of CaCO 3 and gypsum by these communities were also investigated by determining the need for metabolic active cells, the effect of a calcium channel blocker, and the presence of extracellular polymeric substances (EPS). The results showed that metabolically active cells can lead to production of EPS and formation of Ca2+ gradient along the cells through calcium channels, which will trigger formation of biominerals. The prevention of biomineralization by these consortia was also investigated with two common polymeric RO antiscalants, i.e. polyacrylic acid (PAA) and polymaleic acid (PMA). Results showed that these antiscalants do not prevent the formation of the bio-precipitates suggesting that novel approaches to prevent biomineralization in RO systems still needs to be investigated. Image 1 • Microbial consortia can induce biomineralization in RO conditions. • The types of crystals formed depend on the microbial diversity. • Calcium channels allows Ca2+ accumulation around cell walls and biomineralization. • EPS facilitates biomineralization without cells. • Biomineralization cannot be inhibited in the tested conditions by two antiscalants. [ABSTRACT FROM AUTHOR]