Non-target screening of volatile organic compounds in spray-type consumer products and their potential health risks.

Widespread use of spray-type consumer products can raise significant concerns regarding their effects on indoor air quality and human health. In this study, we conducted non-target screening using gas chromatography-mass spectrometry (GC-MS) to analyze VOCs in 48 different spray-type consumer products. Using this approach, we tentatively identified a total of 254 VOCs from the spray-type products. Notably, more VOCs were detected in propellant-type products which are mostly solvent-based than in trigger-type ones which are mostly water-based. The VOCs identified encompass various chemical classes including alkanes, cycloalkanes, monoterpenoids, carboxylic acid derivatives, and carbonyl compounds, some of which arouse concerns due to their potential health effects. Alkanes and cycloalkanes are frequently detected in propellant-type products, whereas perfumed monoterpenoids are ubiquitous across all product categories. Among the identified VOCs, 12 compounds were classified into high-risk groups according to detection frequency and signal-to-noise (S/N) ratio, and their concentrations were confirmed using reference standards. Among the identified VOCs, D-limonene was the most frequently detected compound (freq. 21/48), with the highest concentration of 1.80 mg/g. The risk assessment was performed to evaluate the potential health risks associated with exposure to these VOCs. The non-carcinogenic and carcinogenic risks associated with the assessed VOC compounds were relatively low. However, it is important not to overlook the risk faced by occupational exposure to these VOCs, and the risk from simultaneous exposure to various VOCs contained in the products. This study serves as a valuable resource for the identification of unknown compounds in the consumer products, facilitating the evaluation of potential health risks to consumers.

Occurrence and characteristics of microplastics in fish of the Han River, South Korea: Factors affecting microplastic abundance in fish.

This study examined the abundance of microplastics (MPs) in 106 fish from 22 species inhabiting three sites of the Han River, South Korea. In total, 1753 MPs from 106 fish samples were identified with an average abundance of 15.60 ± 13.45 MPs per individual fish (MPs indiv-1) in the North Han River, 16.35 ± 12.32 MPs indiv-1 in the South Han River, and 20.14 ± 10.01 MPs indiv-1 in downstream of the Han River, indicating that the fish in the downstream of the Han River was the most contaminated by MPs. The dominant size of MPs detected in fish ranged between 0.1 and 0.2 mm, and the most common polymer types found in fish were polypropylene (PP) (≥40%) and polyethylene (PE) (≥23%), followed by polytetrafluoroethylene (PTFE) (≥16%) at all sampling locations. A significant correlation was observed between the log-transformed number of MPs with log-transformed fish length (p < 0.01) and with log-transformed fish weight (p < 0.01). The Kruskal-Wallis test disclosed a significant difference in the number of MPs among the feeding habits (p < 0.01), indicating that omnivorous and insectivorous fish contained more MPs than carnivorous and herbivorous fish. In addition, fish habitat result showed that pelagic fish contained a higher level of MPs than demersal fish, but no significant differences in the number of MPs among fish habitats were observed (p > 0.05).

Analysis of semi-volatile organic compounds in indoor dust and organic thin films by house type in South Korea.

In this study, semi-volatile organic compounds (SVOCs) in samples of indoor dust and organic thin films obtained from 100 residential houses in South Korea, were examined, based on both target analysis using gas chromatography-mass spectrometry (GC-MS) and non-target analysis by gas chromatography-quadrupole time-of flight mass spectrometry (GC-QTOF-MS) screening. In the targeted approach, phthalates and polycyclic aromatic hydrocarbons (PAHs) were analyzed in dust and organic film samples, to find that both these classes of SVOCs were detected in dust and organic film samples, with the median concentrations of eight phthalates (Σ8 phthalate) and 16 PAHs (Σ16 PAH) being 1015.93 µg/g and 1824.97 ng/g in the dust samples, and 75.79 µg/m2 and 2252.78 ng/m2 in the organic film samples, respectively. Among the phthalates, in all house types. bis(2-ethylhexyl) phthalate (DEHP) was detected at the highest concentration, followed by dibutyl phthalate (DBP) and diisobuthyl phthalate (DiBP), with DEHP levels found to be highest in dwelling houses. DEHP levels were found to be significantly associated with building age and renovation status. Lower levels of DEHP were detected in houses less than 10 years old or that had undergone renovation in the previous 10 years. Among the assessed PAHs, a significant correlation was detected between benzo(a)pyrene in dust and building age (p < 0.05). These findings imply that the inhabitants of older houses are at a greater risk of exposure to SVOCs originating from indoor dust and organic films. Non-target screening of selected dust and organic film samples using GC-QTOF-MS data revealed the presence of numerous SVOC compounds, including triphenylphosphine oxide, (Z)-9-octadecenamide, and cyclosiloxanes, along with certain organophosphate flame retardants including tris(1-chloro-2-propyl) phosphate (TCPP) and tris(1,3-dichloroisopropyl) phosphate (TDCPP), and plasticizers. These compounds identified in the non-target screening are of emerging concern, and their presence in dust and organic films needs to be estimated.

Occurrence and Fate of Micropollutants in Private Wastewater Treatment Facility (WTF) and Their Impact on Receiving Water.

This study investigated the occurrence and removals of micropollutants in the sewage treatment tank (STT) which is a typical private wastewater treatment facility used in the rural communities in Korea, and their impact on receiving water. STTs were selected in eight provinces to examine the regional difference in the composition of micropollutant occurrence. We measured ten selected micropollutants in influents and effluents of STTs, as well as upstream and downstream of its receiving surface water. The dominant micropollutants in the influent of the STTs were caffeine (13,346 ng/L), acetaminophen (11,331 ng/L), ibuprofen (1440 ng/L), and naproxen (1313 ng/L), in agreement with the amounts produced annually in Korea. In the effluent, caffeine (1912 ng/L), acetaminophen (1586 ng/L), naproxen (475 ng/L), and ibuprofen (389 ng/L) were detected in relatively high concentrations. The composition of micropollutants in STT influents showed little regional variation by provinces, suggesting that the consumption pattern of these micropollutants did not show regional variation. The removal efficiencies of the selected micropollutants at the STTs ranged from 12% (carbamazepine) to 88% (acetaminophen), lower than typical removal by sewage treatment plants (STPs). This result is probably due to the automatic operation systems and simple treatment processes in STTs compared with STPs. The concentrations of selected micropollutants upstream of the receiving water were generally lower compared with those observed downstream, indicating that effluent from STTs was the main source. The per capita discharge loads of STTs and annual emissions rates (kg/year) from private wastewater treatment facilities were estimated for the selected micropollutants.

Nanoscale-Agglomerate-Mediated Heterogeneous Nucleation.

Water vapor condensation on hydrophobic surfaces has received much attention due to its ability to rapidly shed water droplets and enhance heat transfer, anti-icing, water harvesting, energy harvesting, and self-cleaning performance. However, the mechanism of heterogeneous nucleation on hydrophobic surfaces remains poorly understood and is attributed to defects in the hydrophobic coating exposing the high surface energy substrate. Here, we observe the formation of high surface energy nanoscale agglomerates on hydrophobic coatings after condensation/evaporation cycles in ambient conditions. To investigate the deposition dynamics, we studied the nanoscale agglomerates as a function of condensation/evaporation cycles via optical and field emission scanning electron microscopy (FESEM), microgoniometric contact angle measurements, nucleation statistics, and energy dispersive X-ray spectroscopy (EDS). The FESEM and EDS results indicated that the nanoscale agglomerates stem from absorption of sulfuric acid based aerosol particles inside the droplet and adsorption of volatile organic compounds such as methanethiol (CH3SH), dimethyl disulfide (CH3SSCH), and dimethyl trisulfide (CH3SSSCH3) on the liquid-vapor interface during water vapor condensation, which act as preferential sites for heterogeneous nucleation after evaporation. The insights gained from this study elucidate fundamental aspects governing the behavior of both short- and long-term heterogeneous nucleation on hydrophobic surfaces, suggest previously unexplored microfabrication and air purification techniques, and present insights into the challenges facing the development of durable dropwise condensing surfaces.

Emission of greenhouse gases from waste incineration in Korea.

Greenhouse gas (GHG) emission factors previously reported from various waste incineration plants have shown significant variations according to country-specific, plant-specific, and operational conditions. The purpose of this study is to estimate GHG emissions and emission factors at nine incineration facilities in Korea by measuring the GHG concentrations in the flue gas samples. The selected incineration plants had different operation systems (i.e., stoker, fluidized bed, moving grate, rotary kiln, and kiln & stoker), and different nitrogen oxide (NOx) removal systems (i.e., selective catalytic reduction (SCR) and selective non-catalytic reduction (SNCR)) to treat municipal solid waste (MSW), commercial solid waste (CSW), and specified waste (SW). The total mean emission factors for A and B facilities for MSW incineration were found to be 134 ± 17 kg CO2 ton-1, 88 ± 36 g CH4 ton-1, and 69 ± 16 g N2O ton-1, while those for CSW incineration were 22.56 g CH4 ton-1 and 259.76 g N2O ton-1, and for SW incineration emission factors were 2959 kg CO2 ton-1, 43.44 g CH4 ton-1 and 401.21 g N2O ton-1, respectively. Total emissions calculated using annual incineration for MSW were 3587 ton CO2-eq yr-1 for A facility and 11,082 ton CO2-eq yr-1 for B facility, while those of IPCC default values were 13,167 ton CO2-eq yr-1 for A facility and 32,916 ton CO2-eq yr-1, indicating that the emissions of IPCC default values were estimated higher than those of the plant-specific emission factors. The emission of CSW for C facility was 1403 ton CO2-eq yr-1, while those of SW for D to I facilities was 28,830 ton CO2-eq yr-1. The sensitivity analysis using a Monte Carlo simulation for GHG emission factors in MSW showed that the GHG concentrations have a greater impact than the incineration amount and flow rate of flue gas. For MSW incineration plants using the same stoker type in operation, the estimated emissions and emission factors of CH4 showed the opposite trend with those of NO2 when the NOx removal system was used, whereas there was no difference in CO2 emissions.

Enhanced Jumping-Droplet Departure.

Water vapor condensation on superhydrophobic surfaces has received much attention in recent years because of its ability to shed water droplets at length scales 3 decades smaller than the capillary length (∼1 mm) via coalescence-induced droplet jumping. Jumping-droplet condensation has been demonstrated to enhance heat transfer, anti-icing, and self-cleaning efficiency and is governed by the theoretical inertial-capillary scaled jumping speed (U). When two droplets coalesce, the experimentally measured jumping speed (Uexp) is fundamentally limited by the internal fluid dynamics during the coalescence process (Uexp < 0.23U). Here, we theoretically and experimentally demonstrate multidroplet (>2) coalescence as an avenue to break the two-droplet speed limit. Using side-view and top-view high-speed imaging to study more than 1000 jumping events on a copper oxide nanostructured superhydrophobic surface, we verify that droplet jumping occurs as a result of three fundamentally different mechanisms: (1) coalescence between two droplets, (2) coalescence among more than two droplets (multidroplet), and (3) coalescence between one or more droplets on the surface and a returning droplet that has already departed (multihop). We measured droplet-jumping speeds for a wide range of droplet radii (5-50 µm) and demonstrated that while the two-droplet capillary-to-inertial energy conversion mechanism is not identical to that of multidroplet jumping, speeds above the theoretical two-droplet limit (>0.23U) can be achieved. However, we discovered that multihop coalescence resulted in drastically reduced jumping speeds (≪0.23U) due to adverse momentum contributions from returning droplets. To quantify the impact of enhanced jumping speed on heat-transfer performance, we developed a condensation critical heat flux model to show that modest jumping speed enhancements of 50% using multidroplet jumping can enhance performance by up to 40%. Our results provide a starting point for the design of enhanced-performance jumping-droplet surfaces for industrial applications.

Predictive factors for adverse pregnancy outcomes after renal transplantation.

Several predictive factors associated with adverse pregnancy outcomes in female renal recipients have been suggested. Our study aimed to determine the most important factor for prediction of adverse pregnancy outcomes in female renal recipients. We studied 41 pregnancies in 29 female renal recipients retrospectively. We reviewed pregnancy outcomes and possible predictive factors including pre-pregnancy serum creatinine (SCr), pre-pregnancy glomerular filtration rate (GFR), pre-pregnancy hypertension, pre-pregnancy proteinuria, transplantation-pregnancy interval and type of immunosuppressants. We defined an adverse pregnancy-related outcomes index (APOI) that included the following conditions: (i) preeclampsia; (ii) fetal growth restriction (FGR); (iii) prematurity before 34 wk of gestation; (iv) fetal loss (v) graft dysfunction during pregnancy or within three months from delivery. The cutoff of pre-pregnancy serum creatinine and GFR was determined by receiver operating characteristics curves for the prediction of each adverse outcome and APOI. Only pre-pregnancy serum creatinine was associated with adverse pregnancy outcome, and 1 mg/dL was determined to be a useful cutoff for the prediction of each adverse outcomes. Pre-pregnancy SCr ≥ 1 mg/dL was associated with 7.7 times increased risk of preeclampsia and 6.9 times increased risk of APOI. Pre-pregnancy serum creatinine is the most powerful predictive factor for adverse pregnancy outcomes, and <1 mg/dL may be used as a screen for successful pregnancy outcome.

Removal characteristics of 53 micropollutants during ozonation, chlorination, and UV/H2O2 processes used in drinking water treatment plant.

The removal of 53 emerging micropollutants (MPs), including 10 per- and polyfluorinated substances (PFASs), 25 pharmaceuticals and personal care products (PPCPs), 7 pesticides, 5 endocrine disrupters (EDCs), 3 nitrosamines, and 3 taste and odor compounds (T&Os), by chlorination, ozonation, and UV/H2O2 treatment was examined in deionized water and surface waters used as the raw waters in drinking water treatment plants (DWTPs) in South Korea. The UV/H2O2 treatment was effective in the removal of most MPs, whereas chlorination was selectively effective for 19 MPs, including EDCs (>70 %). MPs containing aromatic ring with electron-donating functional group, or primary and secondary amines were effectively removed by chlorination immediately upon reaction initiation. The removal of MPs by ozonation was generally lower than that of the other two processes at a low ozone dose (1 mg L-1), but higher than chlorination at a high ozone dose (3 mg L-1), particularly for 16 MPs, including T&Os. Compared in deionized water, the removals of MPs in the raw water samples were lower in all three processes. The regression models predicting the rate constants (kobs) of 53 MPs showed good agreement between modeled and measured value for UV/H2O2 treatment (R2 = 0.948) and chlorination (R2 = 0.973), despite using only dissolved organic carbon (DOC) and oxidant concentration as variables, whereas the ozonation model showed a variation (R2 = 0.943). Our results can provide the resources for determining which oxidative process is suitable for treating specific MPs present in the raw waters of DWTPs.

Outcome of isolated fetal renal pyelectasis diagnosed during midtrimester screening ultrasound and cut-off value to predict a persistent or progressive pyelectasis in utero.

AIM: To define a better cut-off value of the renal pelvis anteroposterior diameter (RPAPD) to predict persistent or progressive pyelectasis during pregnancy. METHODS: We retrospectively reviewed 8873 women whose fetal RPAPD was measured. Midtrimester pyelectasis was defined as a RPAPD of ≥4 mm. Persistent/progressive pyelectasis was defined as a RPAPD of ≥10 mm before delivery. A RPAPD cut-off value to predict a persistent/progressive pyelectasis was determined by receiver operating characteristic curve analysis. RESULTS: Among 249 isolated cases of pyelectasis, persistent/progressive pyelectasis was found in 6.9% before delivery. The midtrimester RPAPD cut-off value that best predicted persistent/progressive pyelectasis before delivery was ≥6 mm with sensitivity, specificity, positive and negative predictive values of 64.3%, 88.7%, 30.0%, and 97.1%, respectively. CONCLUSIONS: Although most cases of midtrimester fetal pyelectasis regress to normal during pregnancy, those with a RPAPD of ≥6 mm in the midtrimester are at higher risk for persistent or progressive pyelectasis.

Optimization of photolysis of diclofenac using a response surface methodology.

This study investigates the effects of environmental parameters such as UV intensity (X(1), 2.1 ∼ 6.3 mW/cm(2)), Fe(III) (X(2), 0 ∼ 0.94 mg/L), NO(3)(-) (X(3), 0 ∼ 20 mg/L) and humic acid (X(4), 0 ∼ 30 mg/L) on the removal efficiency of diclofenac (DCF, Y), and optimization using a response surface methodology (RSM) based on Box-Behnken design (BBD). According to analysis of variance and t-test results (p < 0.001), the proposed quadratic BBD model based on a total of 29 experimental runs fitted well to the experimental data. Moreover, the determination coefficient (R(2) = 0.990) and adjusted determination coefficient (R(a)(2) = 0.981) indicated that this model is adequate with a high goodness-of-fit. Variables of X(1), X(2) and X(3) had significant positive contributions (p < 0.001), while X(4) had significant negative contribution to the DCF removal (p < 0.001). A Pareto analysis showed that X(4) was the most important factor (57.18%) in DCF photolytic removal. The predicted and observed DCF removal were 94.98 and 94.2% under optimal conditions (X(1) = 6.29 mW/cm(2), X(2) = 0.75 mg/L, X(3) = 15.65 mg/L and X(4) = zero), respectively. The RSM not only gives valuable information on the interactions between these photoreactive species (UV intensity, Fe(III), NO(3)(-), and humic acid) that influence DCF removal, but also identifies the optimal conditions for effective DCF removal in water.

Temporal and spatial distribution of microplastic in the sediment of the Han River, South Korea.

Sediments are sinks for microplastics (MPs) in freshwater environments. It is, therefore, necessary to investigate the occurrence and fate of accumulated MPs in the sediments, which pose a risk to aquatic organisms. We conducted the first comprehensive investigation of MPs in riverine sediment in South Korea to examine the temporal and spatial distribution of MPs in the sediment at the two main branches and downstream of the Han River. The average abundance of MPs over all sites was 0.494 ± 0.280 particles/g. Spatially, the MP abundance at three sites in the North Han River (0.546 ± 0.217 particles/g) was higher than those in the South Han River (0.383 ± 0.145 particles/g) and downstream of the Han River (0.417 ± 0.114 particles/g). The abundances of MPs before dams at two upstream sites were significantly higher than that at other sites because of the slow river flow velocity attributed to the artificial structure. The abundance of MPs after the mosoon season (October, 0.600 ± 0.357 particles/g) was higher than that before the mosoon season (April, 0.389 ± 0.099 particles/g). The most common polymer types observed were polyethylene (>38%) and polypropylene (>24%). Irrespective of the location and season, greater than 93% of MPs identified were fragments, and the remaining were fibers. The concentrations of TOC, TN, and TP in the sediment were positively correlated with MP abundance. MP abundance was also positively correlated with clay and silt fractions of the sediment; however, it was negatively correlated with sand fraction. This study provides a basis for the management of MP pollution by offering findings related to critical factors influencing MP abundance in sediment.

Advanced microplastic monitoring using Raman spectroscopy with a combination of nanostructure-based substrates.

Micro(nano)plastic (MNP) pollutants have not only impacted human health directly, but are also associated with numerous chemical contaminants that increase toxicity in the natural environment. Most recent research about increasing plastic pollutants in natural environments have focused on the toxic effects of MNPs in water, the atmosphere, and soil. The methodologies of MNP identification have been extensively developed for actual applications, but they still require further study, including on-site detection. This review article provides a comprehensive update on the facile detection of MNPs by Raman spectroscopy, which aims at early diagnosis of potential risks and human health impacts. In particular, Raman imaging and nanostructure-enhanced Raman scattering have emerged as effective analytical technologies for identifying MNPs in an environment. Here, the authors give an update on the latest advances in plasmonic nanostructured materials-assisted SERS substrates utilized for the detection of MNP particles present in environmental samples. Moreover, this work describes different plasmonic materials-including pure noble metal nanostructured materials and hybrid nanomaterials-that have been used to fabricate and develop SERS platforms to obtain the identifying MNP particles at low concentrations. Plasmonic nanostructure-enhanced materials consisting of pure noble metals and hybrid nanomaterials can significantly enhance the surface-enhanced Raman scattering (SERS) spectra signals of pollutant analytes due to their localized hot spots. This concise topical review also provides updates on recent developments and trends in MNP detection by means of SERS using a variety of unique materials, along with three-dimensional (3D) SERS substrates, nanopipettes, and microfluidic chips. A novel material-assisted spectral Raman technique and its effective application are also introduced for selective monitoring and trace detection of MNPs in indoor and outdoor environments.

Spectroscopic analysis of microplastic contaminants in an urban wastewater treatment plant from Seoul, South Korea.

In this study, a systematic multi-spectroscopic analysis of microplastics (MPs) sampled from a metropolitan area of Seoul was undertaken to elevate understanding of the role of wastewater treatment plants (WWTPs) in eliminating suspended contaminants including MPs before releasing the effluent water into the environment. We analyzed pollutants in influent and effluent samples from a WWTP in Seoul, South Korea. Spectroscopic and microscopic methods were used to analyze MPs. Fourier-transform infrared (FT-IR) spectroscopy in the wavenumber region between 4000 and 715 cm-1 was employed to estimate the abundance of MPs in wastewater. Stereomicroscope images and Nile red staining were used to facilely identify MPs in both influents and effluents to compare the results with those of FT-IR data. Hyperspectral imaging could identify MPs in the influent sample with the reflection method at 400-900 nm. Our preliminary results indicate that the most observed MPs after the wastewater were filtered by a 45 µm stainless steel mesh filter were polyethylene (PE) and polypropylene (PP). The total number of the prevalent MPs in influent samples decreased significantly. Nanostructure particles could be found by field-emission scanning electron microscopy (FE-SEM). Our combined multi-spectroscopic study should be helpful to provide a guideline for the rapid spectroscopic analysis of freshwater in the Han River, Seoul, South Korea.

Occurrence, Potential Sources, and Risk Assessment of Volatile Organic Compounds in the Han River Basin, South Korea.

Increasing public awareness about the aesthetics and safety of water sources has shifted researchers' attention to the adverse effects of volatile organic compounds (VOCs) on humans and aquatic organisms. A total of 17 VOCs, including 10 volatile halogenated hydrocarbons and seven volatile non-halogenated hydrocarbons, were investigated at 36 sites of the Han River Basin, which is the largest and most important drinking water source for residents of the Seoul metropolitan area and Gyeonggi province in South Korea. The VOC concentrations ranged from below detection limits to 1.813 µg L-1. The most frequently detected VOC was 1,2-dichloropropane, with a detection frequency of 80.56%, as it is used as a soil fumigant, chemical intermediate, and industrial solvent. In terms of geographical trends, the sampling sites that were under the influence of sewage and industrial wastewater treatment plants were more polluted with VOCs than other areas. This observation was also supported by the results of the principal component analysis. In the present study, the detected concentrations of VOCs were much lower than that of the predicted no-effect concentrations, suggesting low ecological risk in the Han River. However, a lack of available ecotoxicity data and limited comparable studies warrants further studies on these compounds.

Nanostructured Raman substrates for the sensitive detection of submicrometer-sized plastic pollutants in water.

We prepared novel Raman substrates for the sensitive detection of submicron-sized plastic spheres in water. Anisotropic nanostar dimer-embedded nanopore substrates were prepared for the efficient identification of submicron-sized plastic spheres by providing internal hot spots of electromagnetic field enhancements at the tips of nanoparticles. Silver-coated gold nanostars (AuNSs@Ag) were inserted into anodized aluminum oxide (AAO) nanopores for enhanced microplastic (MP) detection. We found that surface-enhanced Raman scattering (SERS) substrates of AuNSs@Ag@AAO yielded stronger signals at the same weight percentages for polystyrene MP particles with diameters as small as 0.4 µm, whereas such behaviors could not be observed for larger MPs (diameters of 0.8 µm, 2.3 µm, and 4.8 µm). The detection limit of the submicrometer-sized 0.4 µm in our Raman measurements were estimated to be 0.005% (∼0.05 mg/g =50 ppm) along with a fast detection time of only a few min without any sample pretreatments. Our nano-sized dimensional matching substrates may provide a useful tool for the application of SERS substrates for submicrometer MP pollutants in water.

Greenhouse gas emissions from advanced oxidation processes in the degradation of bisphenol A: a comparative study of the H2O2/UV, TiO2 /UV, and ozonation processes.

To estimate greenhouse gas (GHG) emissions and degradation rate constants (kobs) from H2O2/UV-C, TiO2/UV-C, and ozonation processes in the degradation of bisphenol A (BPA), the laboratory scale experiments were conducted. In the H2O2/UV-C process, the fastest degradation rate constant (kobs = 0.353 min-1) was observed at 4 mM of H2O2, while the minimum GHG emission was achieved at 3 mM of H2O2. In the TiO2/UV-C process, the fastest rate constant (kobs = 0.126 min-1) was achieved at 2000 mg/L of TiO2, while the minimum GHG emission was observed at 400 mg/L of TiO2. In the ozonation process, GHG emissions were minimal at 5 mg/L of O3, but the degradation rate constant kept on increasing as the O3 concentration increased. There were three major types of GHG emissions in the advanced oxidation processes (AOPs). In the ozonation process, most of the GHG emissions were generated by electricity consumption. TiO2/UV-C process accounted for a significant portion of the GHGs generated by the use of chemicals. Finally, the H2O2/UV-C process produced similar GHG emissions from both chemical inputs and electricity consumption. The carbon footprint calculation revealed that for the treatment of 1 m3 of water contaminated with 0.04 mM BPA, the H2O2/UV-C process had the smallest carbon footprint (0.565 kg CO2 eq/m3), followed by the TiO2/UV-C process (3.445 kg CO2 eq/m3) and the ozonation process (3.897 kg CO2 eq/m3). Our results imply that the increase in removal rate constant might not be the optimal parameter for reducing GHG emissions during the application of these processes. Graphical abstract .

Dropwise condensation on solid hydrophilic surfaces.

Droplet nucleation and condensation are ubiquitous phenomena in nature and industry. Over the past century, research has shown dropwise condensation heat transfer on nonwetting surfaces to be an order of magnitude higher than filmwise condensation heat transfer on wetting substrates. However, the necessity for nonwetting to achieve dropwise condensation is unclear. This article reports stable dropwise condensation on a smooth, solid, hydrophilic surface (θa = 38°) having low contact angle hysteresis (<3°). We show that the distribution of nano- to micro- to macroscale droplet sizes (about 100 nm to 1 mm) for coalescing droplets agrees well with the classical distribution on hydrophobic surfaces and elucidate that the wettability-governed dropwise-to-filmwise transition is mediated by the departing droplet Bond number. Our findings demonstrate that achieving stable dropwise condensation is not governed by surface intrinsic wettability, as assumed for the past eight decades, but rather, it is dictated by contact angle hysteresis.

Concentration and distribution of per- and polyfluoroalkyl substances (PFAS) in the Asan Lake area of South Korea.

Seasonal and spatial variations in per- and polyfluoroalkyl substances (PFAS) concentrations in different environmental media in the Asan Lake area of South Korea were investigated by measuring liquid chromatography-tandem mass spectrometry (LC-MS/MS). The mean concentrations of Σ16 PFAS in the different media were in the ranges of 20.7-98.2 pg/m3 in air, 17.7-467 ng/L in water, 0.04-15.0 ng/g dry weight (dw) in sediments, and not detected (n.d.)-12.9 ng/g dw in soils, and the mean concentrations of Σ19 PFAS in fish ranged from n.d. to 197 ng/g wet weight. The most frequently detected PFAS were perfluorooctanoic acid (PFOA) in air and soils, perfluoropentanoic acid (PFPeA) in water, and perfluorooctane sulfonate (PFOS) in sediment and fish. Long-chain PFAS species dominated over short-chain PFAS in most media samples except for the water phase. Sediment-water partition coefficients (log Kd) and bioaccumulation factors (log BAF) of PFAS were calculated using measured concentrations in water, sediments, and fish. Log Kd of PFAS tended to increase with increasing CF2 units of PFAS, and perfluorodecanoic acid (PFDA) and PFOS showed the highest log BAF value (> 3.0) in all fish species. These results indicate that longer-chain PFAS, especially PFOS, can be effectively accumulated in biota such as fish.

Seasonal variation in dissolved gaseous mercury and total mercury concentrations in Juam Reservoir, Korea.

Dissolved gaseous mercury (DGM) and total mercury (TM) concentrations were measured in Juam Reservoir, Korea. DGM concentrations were higher in spring (64+/-13pgL(-1)) and summer (109+/-15pgL(-1)), and lower in fall (20+/-2pgL(-1)) and winter (23+/-6pgL(-1)). In contrast, TM concentrations were higher in fall (3.2+/-0.1ngL(-1)) and winter (3.3+/-0.1ngL(-1)) than in spring (2.3+/-0.1ngL(-1)) and summer (2.2+/-0.4ngL(-1)). DGM concentrations were correlated with water temperature (p<0.0001), ORP (p<0.0001), UV intensity (UV-A: p=0.008; UV-B: p=0.003), and DOC concentration (p=0.0107). DGM concentrations varied diurnally with UV intensity. The average summer DGM (109+/-15pgL(-1)) and TM (2.2+/-0.4ngL(-1)) concentrations in Juam Reservoir were higher than the averages for North American lakes (DGM=38+/-16pgL(-1); TM=1.0+/-1.2ngL(-1)), but lower than levels reported for Baihua Reservoir in China.