Concentrations Of Semivolatile Organic Compounds Research Articles

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.

Phthalate Concentration Estimation and Exposure Assessment and Health Risk Assessment in Indoor Organic Film

Organic films act as passive air samplers and can be employed to assess the concentration of semivolatile organic compounds (SVOCs), such as phthalates, in the gas phase over a defined period using the kinetic adsorption model. Consequently, indoor organic films have been identified as effective media for evaluating human exposure to SVOCs. This study proposed an organic film-based method for assessing SVOC exposure in the indoor environment. Exposure assessments of various phthalate pathways were conducted on children and adults. Organic films were collected for analysis from 110 residential dwellings in metropolitan areas over a two-month period. The exposure assessments were categorized into inhalation, oral, and dermal exposure pathways. Diethyl phthalate was highest in inhalation exposure, dibutyl phthalate represented the highest dermal exposure, and bis(2-ethylhexyl) phthalate was identified as the highest contributor to oral exposure. For children, the primary exposure pathways included dermal absorption of DBP, DEP, diisobutyl phthalate (DiBP), butylbenzyl phthalate (BBP), and di-n-hexyl phthalate (DNHP); dust ingestion of DEHP and di-n-octyl phthalate (DNOP); and inhalation of dimethyl phthalate (DMP). The ECR and HQ for inhalation, dermal, and ingestion did not exceed the threshold in children and adults at all pollutants, suggesting no potential health impact. In contrast, the primary routes of exposure for adults were dermal absorption of DBP, DMP, DEP, DiBP, BBP, and DNHP, along with dust ingestion of DEHP and DNOP. The findings of this study provide valuable baseline data for future research in health risk and SVOC exposure assessments utilizing indoor organic films.

Participant-collected household dust for assessing microorganisms and semi-volatile organic compounds in urban homes

Dust samples collected by researchers and study participants from 43 U.S. urban homes were analyzed and compared to evaluate the feasibility of using participant-collected samples to assess indoor environmental exposures. The microbial and chemical composition of participant-collected (and shipped) samples were compared to researcher-collected samples from the same household, using dust recovered from each home's heating, ventilation, and air conditioning (HVAC) filter. The bacterial and fungal communities present in all dust samples were determined via MiSeq 16S and ITS sequencing, and the concentrations of 27 semi-volatile organic compounds (7 orthophosphates, 6 phthalates, and 14 brominated flame retardants) were determined via GC–MS. Self-report data on the home environment was collected via an online survey of study participants. While the researcher-collected samples (RCS) yielded greater mass than the participant-collected samples (PCS), the alpha and beta diversities of the bacterial and fungal communities recovered in the RCS and PCS were not significantly different, indicating that PCS is a viable option for indoor microbiome studies of residential homes. The microbial communities recovered in both cases reflected the dominance of human-associated bacterial taxa and outdoor-associated fungal taxa with similar pathogen-associated taxa present in each sample type. In both PCS and RCS, the amount of carpet in the home and the frequency of bleach use had a significant effect on the composition of fungal communities. Semi-volatile organic compounds (SVOCs) of potential human health concern, were commonly detected in the homes. Organophosphates and phthalates were recovered at a similar frequency in both PCS and RCS. Measured SVOC concentration levels were consistent with previous indoor studies although differences were observed between PCS and RCS for several SVOCs. This study demonstrates the potential and challenges associated with participant-collected dust samples for indoor environment studies.

Gas–particle partitioning of semivolatile organic compounds when wildfire smoke comes to town

Abstract. Wildfires have become an increasingly important source of organic gases and particulate matter in the western USA. A large fraction of organic particulate matter emitted in wildfires is semivolatile, and the oxidation of organic gases in smoke can form lower-volatility products that then condense on smoke particulates. In this research, we measured the gas- and particle-phase concentrations of semivolatile organic compounds (SVOCs) during the 2017 northern California wildfires in a downwind urban area, using semivolatile thermal desorption aerosol gas chromatography (SV-TAG), and measured SVOCs in a rural site affected by biomass burning using cTAG (comprehensive thermal desorption aerosol gas chromatography mass spectrometry) in Idaho in 2018. Commonly used biomass burning markers such as levoglucosan, mannosan, and nitrocatechols were found to stay predominantly in the particle phase, even when the ambient organic aerosol (OA) was relatively low. The phase partitioning of SVOCs is observed to be dependent on their saturation vapor pressure, while the equilibrium absorption model underpredicts the particle-phase fraction of most of the compounds measured. Wildfire organic aerosol enhanced the condensation of polar compounds into the particle phase but not some nonpolar compounds, such as polycyclic aromatic hydrocarbons.

Derivation and application of indoor air screening values for inhalation exposure to semi-volatile organic compounds

Semi-volatile organic compounds (SVOCs) are being increasingly studied in indoor air. The absence of health-based inhalation exposure guidelines for most SVOCs impedes the interpretation of indoor air concentrations from a health risk context. To accelerate the derivation of screening values for a large number of SVOCs, a tiered framework was developed to evaluate and adjust published hazard assessments for SVOCs to calculate benchmarks relevant for evaluation of inhalation risk. Inhalation screening values were derived for 43 SVOCs considered in this study, most of which required extrapolation from oral exposure guidelines. The screening values were compared to published SVOC concentrations in homes in Canada to evaluate the potential health risks of chronic exposure to SVOCs in indoor residential environments. SVOCs that could be prioritized for further evaluation were dibutyl phthalates (DBP), di(2-ethylhexyl) phthalate (DEHP) and polybrominated diphenyl ethers (PBDEs). The framework could be applied more broadly in the future to derive screening values for other non-traditional indoor air contaminants with limited inhalation hazard data or assessments.

Impact of smoking and candle burning on air concentrations of PCB in a PCB contaminated indoor environment

Long-lasting elevated indoor air concentrations of semi-volatile organic compounds (SVOCs) can cause contamination of indoor surface materials because these compounds have physical-chemical properties causing them to be sorbed (and desorbed) from various surfaces in the indoor environment. Due to this material-gas partitioning and the extensive area of surface materials, the surfaces have the potential to counteract changes in gaseous air concentrations by re-emitting or absorbing SVOCs. In the air itself a partitioning between the gaseous and particulate bound SVOCs exists, relying on among other things the amount and characteristics of the particles. The aim of this study was to investigate the impact of increased particle matter in a contaminated environment, i.e. whether an increase in particles would increase the total air concentration of SVOC through a displacement from the gaseous to the particle phase and at the same time a re-establishment of the gaseous concentration caused by desorption from the surface materials. The study was conducted by measuring the gas and particle bound concentration of SVOCs among a range of congeners of polychlorinated biphenyls (PCBs) in indoor air and quantify the influence of an increased concentration of particulate matter. The experiments were conducted in a room within a dwelling that had elevated levels of PCBs for the last five decades. The increased amount of particulate matter was generated by burning candles and cigarettes, which was measured as particle number concentration and size fractions. Increased cigarette particle concentration increased the indoor air concentration of the sum of all congeners measured by almost 70% compared to background level. Particles from candle burning did not have a similarly significant effect, even though their number concentration was higher. This was likely due to the chemical composition of the particles; cigarette smoke consists primarily of organic particles, while the steady burning of candles produces smaller, mainly inorganic particles. The concentrations of 15 PCB congeners were determined and it was observed that their sorption to cigarette smoke increased with increasing chlorination. A partitioning model indicates absorptive behaviour of PCB to cigarette particles. The results show that smoking inside a residence with long-lasting, elevated PCB concentrations can further increase the concentration of PCB in the air due to its interaction with particulate matter.

Thermal desorption-based method for quantifying semi-volatile organic compounds in house dust: Method development and evaluation

As an important storage medium of semi-volatile organic compounds (SVOC) in indoor environments, house dust has been extensively used to assess the pollution level of indoor SVOC. SVOC in house dust are commonly quantified using solvent-extraction methods, which are however solvent-consuming, time-consuming and laborious. Thermal desorption (TD, solvent-free and easy-to-use) is a good alternative to solvent extractions, but its performance for analyzing house dust is still unverified. Therefore, we proposed a TD-based method for quantifying SVOC in house dust by incorporating the TD technique with GC-MS. Laboratory experiments (48 samples with high SVOC concentrations) and field-test experiments (12 samples with low SVOC concentrations) were performed to justify the proposed method by comparing its results to those of a traditional solvent-extraction method (Soxhlet extraction). For laboratory dusts, the accuracy (relative deviation < 20%) and repeatability (relative standard deviation < 13%) of the TD-based method were comparable to the solvent-extraction method. For field-test dusts, higher SVOC concentrations were typically obtained by the TD-based method, implying its superior performance. These results gave evident confidence in the performance of the TD-based method, which facilitated the simple, solvent-free and accurate quantification of SVOC in house dust.

Predicting the fate and transport of indoor DEHP considering their interaction with particles under different ventilation modes

Ventilation are widely used in residential buildings to dilute indoor pollutants. While the dynamic partition model of semi-volatile organic compounds (SVOCs) for homes with a central forced-air handling system is still far from adequate. Here we developed a mechanistic model of SVOCs considering dynamic behaviours of size-resolved particles brought by ventilation. In this model, effects of air changes per hour (ACH) and secondary source of particles on mass transfer coefficient of source surfaces (hms) are considered. Three factors, namely ventilation mode, fresh air ratio and filtration efficiency are examined in detail, to figure out the time-varying multi-phase concentration of di-2-ethylhexyl phthalate (DEHP). Results show that with identical ACH (total ventilation rate/volume), the increase of indoor-outdoor air exchange rate (AER_I/O), would decrease the gas-phase concentration of DEHP, and would significantly shorten the time for the multi-phase DEHP to reach equilibrium concentration. The multi-phase (including the gas-phase, particle-phase and dust-phase) equilibrium concentration of DEHP indoors decreases with the increased fresh air ratio, taking into account the combined effect of ventilation dilution and particle-enhanced source emission. With the increase of filtration efficiency, the particle-phase equilibrium concentration of DEHP decreases, while the gas-phase equilibrium concentration of DEHP increases. Overall, the dynamic model is helpful to improve understandings of SVOCs’ interactions with airborne particles caused by ventilation systems, and clarify the key ventilation factors affecting the time-varying multi-phase concentration of SVOCs.

Gas-Particle Partitioning of Semivolatile Organic Compounds in a Residence: Influence of Particles from Candles, Cooking, and Outdoors.

Semivolatile organic compounds (SVOCs) represent an important class of indoor pollutants. The partitioning of SVOCs between airborne particles and the adjacent air influences human exposure and uptake. Presently, little direct experimental evidence exists about the influence of indoor particle pollution on the gas-particle phase partitioning of indoor SVOCs. In this study, we present time-resolved gas- and particle-phase distribution data for indoor SVOCs in a normally occupied residence using semivolatile thermal desorption aerosol gas chromatography. Although SVOCs in indoor air are found mostly in the gas phase, we show that indoor particles from cooking, candle use, and outdoor particle infiltration strongly affect the gas-particle phase distribution of specific indoor SVOCs. From gas- and particle-phase measurements of SVOCs spanning a range of chemical functionalities (alkanes, alcohols, alkanoic acids, and phthalates) and volatilities (vapor pressures from 10-13 to 10-4 atm), we find that the chemical composition of the airborne particles influences the partitioning of individual SVOC species. During candle burning, the enhanced partitioning of gas-phase SVOCs to indoor particles not only affects the particle composition but also enhances surface off-gassing, thereby increasing the total airborne concentration of specific SVOCs, including diethylhexyl phthalate.

Secondary Organic Aerosol Formation from Semi-Volatile and Intermediate Volatility Organic Compounds in the Fall in Beijing

Intermediate volatility organic compounds (IVOCs) and semi-volatile organic compounds (SVOCs) have recently been proposed as important precursors of secondary organic aerosol (SOA). In the present work, 97 volatile organic compounds (VOCs) and 80 intermediate volatility and semi-volatile organic compounds (IVOCs and SVOCs) were measured by online gas chromatography-mass spectrometer/flame ionization detection (GC-MS/FID), and offline thermal desorption gas chromatography-mass spectrometer (TD-GC-MS), respectively. The average concentration of speciated VOCs, IVOCs, and SVOCs were 22.36 ± 9.02 μg m−3, 1.01 ± 0.32 μg m−3, and 0.10 ± 0.17 μg m−3. Alkanes and polycyclic aromatic hydrocarbons (PAHs) are the main compounds of total S/IVOCs. With the increase in molecular weight, the concentrations decreased in the gas phase, while increasing in the particle phase. Vehicular emission is the most significant source according to the carbon preference index (CPI) and the carbon of the most abundant alkane (Cmax). The yield method was used to estimate SOA from the oxidation of VOCs and S/IVOCs. The estimated SOA mass from IVOCs and SVOCs (0.70 ± 0.57 μg m−3) was comparable to that of VOCs (0.62 ± 0.61 μg m−3), and the oxidation of PAHs and alkanes took up 28.70 ± 8.26% and 51.97 ± 20.77% of the total SOA estimation, respectively. Compared to previous work, our study provided detailed molecular information of ambient S/IVOC species and elucidated their importance on SOA formation. Despite their low concentration, S/IVOCs species are important SOA precursors which shared comparable contribution compared with VOCs.

Emissions of VOCs and SVOCs from polyvinyl chloride building materials: Contribution to indoor odor and inhalation health risks

Volatile organic compounds (VOCs) and semi-volatile organic compounds (SVOCs) emitted from indoor building materials may cause indoor air pollution and adverse health effects to residents. However, limited information is available on the odor and health risks of VOCs and SVOCs emissions from polyvinyl chloride (PVC) materials, which are widely used for interior decoration. In this study, the concentration of VOCs and SVOCs emitted from PVC wallpaper and flooring were tested by the emission chamber method and micro-chamber method. Hazards of PVC building materials to people in terms of odor contribution and inhalation health risks were then illustrated. Results showed that 14 VOCs (including four alkanes, one aromatic, and nine oxygenated compounds) and 4 SVOCs (including methyl hexadecanoate, di(2-ethylhexyl) phthalate (DEHP), bis(2-ethylhexyl) adipate (DOA), and di-2-ethylhexyl terephthalate (DOTP)) were detected in the PVC wallpaper and flooring sample emissions. Triethyl phosphate (55.3%) was the main VOC emitted from PVC wallpaper materials, while cyclohexanone (22.4%), n-butyl acetate (21.6%), and 4-methyl-2-pentanone (12.7%) were major VOCs emitted from PVC flooring materials. DOA (1.76 mg/m3) and methyl hexadecanoate (13.0 mg/m3) were the SVOCs with the highest emission concentrations in PVC flooring and wallpaper, respectively. The dominant substances causing odor pollution from PVC wallpaper and flooring were methyl hexadecanoate and cyclohexanone, and cyclohexanone and n-butyl acetate, respectively. The health risk results indicated that the carcinogenic risks (R) of DEHP were below the acceptable level, and the non-carcinogenic effects (HQ) of 2-ethyl-1-hexanol and cyclohexanone were much greater than the acceptable level (HQ = 1) and should be given special attention.

Does Using Corsi-Rosenthal Boxes to Mitigate COVID-19 Transmission Also Reduce Indoor Air Concentrations of PFAS and Phthalates?

The COVID-19 pandemic brought new emphasis on indoor air quality. However, few studies have investigated the impact of air filtration, a COVID-mitigation approach, on indoor air concentrations of semivolatile organic compounds (SVOCs). Using a quasi-experimental design, we quantified the impact of a relatively low-cost "do-it-yourself" air filter (Corsi-Rosenthal Box; CR Box) on indoor air concentrations of 42 PFAS and 24 other SVOCs. We sampled air before (October-November 2021) and during (February-March 2022) deployment of CR Boxes in 17 rooms located in an occupied Providence, Rhode Island office building. We measured sound levels in rooms with CR Boxes operating and not operating. While CR Boxes were deployed, concentrations of seven PFAS (N-EtFOSE, N-EtFOSA, FBSA, PFBS, PFHxS, PFOS, PFNA) were 28-61% lower and concentrations of five phthalates (DMP, DEP, DiBP, BBzP, DCHP) were 29-62% lower. Concentrations of five PFAS and one phthalate increased 23-44% during the intervention period, but the 95% CI of most of these estimates included the null. Daytime sound levels increased 5.0 dB when CR Boxes were operating. These results indicate that CR Boxes reduced exposure to several lower-volatility phthalates and sulfonated PFAS previously reported to be found in office building materials and products, with potentially distracting increases in sound levels.

Accessibility investigation of semi-volatile organic compounds in indoor dust estimated by multi-ratio equilibrium passive sampling

Many semi-volatile organic compounds (SVOCs) accumulate in indoor dust, which serves as a repository for those compounds. The presence of SVOCs in indoor environments is of concern because many of them are suspected to have toxic effects. Total SVOC concentrations in the dust are generally used for exposure assessment to indoor contaminants, assuming that 100% of the SVOCs is accessible for human uptake. However, such an assumption may potentially lead to an overestimated risk related to dust exposure. We applied a multi-ratio equilibrium passive sampling (MR-EPS) for estimation of SVOC accessibility in indoor settled dust using silicone passive samplers and three particle size dust fractions, <0.25 mm, 0.25–0.5 mm, and 1–2 mm in dry and wet conditions. Equilibrations were performed at various sampler–dust mass ratios to achieve different degrees of SVOC depletion, allowing the construction of a desorption isotherm. The desorption isotherms provided accessible fractions (FAS), equivalent air concentrations (CAIR), dust-air partition coefficients (KDUST-AIR) and organic carbon-air partition coefficients (KOC-AIR). The highest FAS were observed in the <0.25 mm dust fraction in wet conditions which is relevant for exposure assessment via oral ingestion. The highest CAIR were estimated for several organophosphorus flame retardants (OPFRs), polycyclic aromatic hydrocarbons (PAHs) and synthetic musks. The logKOC-AIR did not differ between dust particle sizes in dry and wet conditions but within compound groups, different relationships with hydrophobicity were observed. Equivalent lipid-based concentrations (CL⇌DUST) calculated using available lipid-silicone partition coefficients (KLIP-SIL) were compared with lipid-based concentrations (CL) measured in human-related samples collected from Europeans. For hexachlorobenzene (HCB), CL⇌DUST, and CL were similar, indicating equilibrium attainment between environment and human samples. Lipid-based concentrations for persistent legacy contaminants were also similar but lower for PBDEs in human samples. Overall, accessibility estimation using MR-EPS in dust further contributes to human risk assessment.

Measurement methods and impact factors for the key parameters of VOC/SVOC emissions from materials in indoor and vehicular environments: A review.

The emissions of volatile organic compounds (VOCs) and semi-volatile organic compounds (SVOCs) from indoor building and vehicle cabin materials can adversely affect human health. Many mechanistic models to predict the VOC/SVOC emission characteristics have been proposed. Nowadays, the main obstacle to accurate model prediction is the availability and reliability of the physical parameters used in the model, such as the initial emittable concentration, the diffusion coefficient, the partition coefficient, and the gas-phase SVOC concentration adjacent to the material surface. The purpose of this work is to review the existing methods for measuring the key parameters of VOCs/SVOCs from materials in both indoor and vehicular environments. The pros and cons of these methods are analyzed, and the available datasets found in the literature are summarized. Some methods can determine one single key parameter, while other methods can determine two or three key parameters simultaneously. The impacts of multiple factors (temperature, relative humidity, loading ratio, and air change rate) on VOC/SVOC emission behaviors are discussed. The existing measurement methods span very large spatial and time scales: the spatial scale varies from micro to macro dimensions; and the time scale in chamber tests varies from several hours to one month for VOCs, and may even span years for SVOCs. Based on the key parameters, a pre-assessment approach for indoor and vehicular air quality is introduced in this review. The approach uses the key parameters for different material combinations to pre-assess the VOC/SVOC concentrations or human exposure levels during the design stage of buildings or vehicles, which can assist designers to select appropriate materials and achieve effective source control.

Strong temperature influence and indiscernible ventilation effect on dynamics of some semivolatile organic compounds in the indoor air of an office.

Many manmade organic air pollutants are semivolatile and primarily used and exposed indoors. It remains unclear how indoor environmental parameters affect indoor air dynamics of semivolatile organic compounds (SVOCs) in real-world indoor conditions, which directly relates to human exposure. By making time-resolved SVOC measurements over multiple weeks in an office, we characterized the indoor air dynamics of six representative SVOCs which were mainly present in the gas phase and of indoor origins, and investigated the effects of the temperature and ventilation rate. The six species include di-isobutyl phthalate and di-n-butyl phthalate, as well as two n-alkanes and two siloxanes. Airborne concentrations of all six SVOCs responded strongly and quickly to changes in the indoor temperature. The temperature dependence of individual species can be well fitted in the form of the van't Hoff equation, and explained 65-86% of the observed variation in the logarithm-transformed concentrations. In contrast, increasing the ventilation rate by a factor of 3-5 for hours at a constant temperature had no discernible influence on the SVOC concentrations. Further kinetic modeling analysis suggests that the observed fast temperature response and indiscernible ventilation effect are both associated with SVOC sorption onto indoor surfaces, which dramatically slows the response of SVOC concentration to changes in the ventilation rate and speeds up the response to changes in the temperature. These results highlight the importance of sorption reservoirs on regulating indoor SVOC dynamics and also have important implications for controlling and assessing indoor air exposure to SVOCs.

Occurrence, exposure and risk assessment of semi-volatile organic compounds in Chinese homes

Indoor semi-volatile organic compounds (SVOCs) can have a significant impact on human health. Previous studies involved the detection of limited classes of indoor SVOCs in different regions of China. However, overall indoor pollution profiles and the associated health risks via multiple exposure pathways remain unclear. High-throughput screening of SVOCs would help clarify the overall indoor pollution status and identify high-risk pollutants. We collected indoor air and dust samples from 35 Chinese homes and investigated the occurrence of a wide range of SVOCs. Ninety-seven SVOCs including phthalate esters (PAEs), polycyclic aromatic hydrocarbons (PAHs), organophosphate esters, alcohols, fatty acids, phenols, etc., were detected in the air (total concentrations: 0.13–48 μg/m3; median: 3.4 μg/m3) and dust (total concentrations: 120–1500 μg/g; median: 490 μg/g) samples. PAEs were the most abundant, accounting for 55.3 ± 28.6% and 43.4 ± 16.9% of the total SVOC concentrations in the air and dust samples respectively. Human exposure and health risks of 34 SVOCs with detection frequencies >10% were assessed based on inhalation, ingestion and dermal absorption of SVOCs from air and dust by infants and adults. In the case of indoor SVOCs with log Koa < 9, inhalation and dermal contact with air was >90% for adults and >69% for infants. The following five SVOCs in air samples posed significant non-carcinogenic risks and are listed based on their decreasing risk level: dibutyl phthalate > phenanthrene > stearic acid > methyl palmitate > lauryl alcohol. Four PAHs with 2–4 rings posed potential carcinogenic risks, with phenanthrene exceeding the acceptable risk level of 10−4. The high risks posed by SVOCs were due to inhalation exposure. Therefore, keeping the air concentrations of SVOCs, especially that of PAEs and PAHs under check would greatly benefit human health in indoor environments.

Quantitative Analysis of Indoor Gaseous Semi-Volatile Organic Compounds Using Solid-Phase Microextraction: Active Sampling and Calibration

Semi-volatile organic compounds (SVOCs) are important pollutants in indoor environments. Quantification of gaseous SVOC concentrations is essential to assess the pollution levels. Solid-phase microextraction (SPME) is considered to be an attractive sampling technique with merits, including simplicity of use, rapid sampling, and solvent free. However, the applications of SPME for sampling gaseous SVOCs are often limited by the fluctuating velocity of indoor air (leading to an unstable sampling rate) and the uncertainties associated with the traditional calibration of SPME. Therefore, we established an SPME-based active sampler to ensure the stable sampling of SVOCs in fluctuating air and developed a two-step calibration method based on the sampling principle of SPME. The presented method and a traditional method (sorbent tubes packed with Tenax TA) were simultaneously used to measure SVOC concentrations in an airstream generated in experiments. Three typical indoor SVOCs, diisobutyl phthalate (DiBP), tris (1-chloro-2-propyl) phosphate (TCPP), and benzyl butyl phthalate (BBzP) were chosen as the analytes. Mean concentrations measured by SPME agreed well with the sorbent tubes (relative deviations &lt;12%), supporting the feasibility of the presented method. Further studies are expected to facilitate the application of the presented method (especially the problem associated with the sampling-tube loss of low volatile SVOCs).

Semi-volatile organic compounds in fine particulate matter on a tropical island in the South China Sea

Measurements of hazardous semi-volatile organic compounds (SVOCs) in remote tropical regions are rare. In this study, polycyclic aromatic compounds (PACs) [including polycyclic aromatic hydrocarbons (PAHs), nitrated PAHs (NPAHs), and oxygenated PAHs (OPAHs)], organophosphate esters (OPEs), and phthalic acid esters (PAEs) were measured in fine particulate matter (PM2.5) at Yongxing Island in the South China Sea (SCS). The concentrations of PACs (median = 53.5 pg/m3) were substantially low compared with previous measurements. The concentration weighted trajectory (CWT) model showed that the eastern and southern China was the main source region of PAC, occurring largely during the northeast (NE) monsoon. The PM2.5 showed remarkably high concentrations of OPEs (median = 3231 pg/m3) and moderate concentrations of PAEs (13,013 pg/m3). Some Southeast Asian countries were largely responsible for their higher concentrations, driven by the tropical SCS monsoons. We found significant atmospheric loss of the SVOCs, which is an explanation for the low concentrations of PACs. Enhanced formation of N/OPAHs originated from tropical regions was also observed. The positive matrix factorization model was applied to apportion the SVOC sources. The results, as well as correlation analyses of the SVOC concentrations, further indicate insignificant local sources and enhanced atmospheric reactions on this island.

Assessment of gas-phase concentrations of organophosphate flame retardants at the material surface using a midget emission cell coupled to solid-phase microextraction

Actual methods for on-site measurement of gaseous concentrations of Semi-Volatile Organic Compounds (SVOCs) at the material surface (y0) are not yet sufficiently developed mainly due to sampling difficulties. These concentrations are the key data to improve knowledge about indoor sources and human exposure to SVOCs. To the end, a specific emission cell coupled to solid-phase microextraction (SPME) was developed. The main challenge with this method is calibration because of very low volatility of SVOCs and static sampling mode. In this study, a generating system of organophosphate flame retardants (OFRs) using polyurethane foam as source combined with an active sampling method with Tenax tubes was proposed as a novel calibration device for SPME-based method. The generating system delivered stable OFR concentrations after 190 h of operation with a variation not exceeding ±5%. It allowed to obtain robust calibrations for tris-(2-chloropropyl)-phosphate (TCPP) and tri-butyl-phosphate (TBP) measured with the emission cell coupled to SPME-based method, define the optimal sampling requirements and achieve reproducible and accurate measurements of y0 at μg.m−3 level.TCPP and TBP gas-phase concentrations at the polyurethane foam surface (y0) were followed up over more 228 days under controlled temperature conditions. A high stability of these concentrations was observed showing that polyurethane foam acts as a stable and continuous source of organophosphate flame retardants indoors. This novel method should be useful for assessing the dynamic of emissions from indoor sources and potential exposure to SVOCs in indoor environments.

Characterizing the Semi-Volatile Organic Compounds in Runoff from Roads and Other Impervious Surfaces in a Suburban Area of Beijing.

Stormwater runoff samples were collected from five different land use sites (gas station, city road, campus, park, and residential) in a precipitation event on May 22nd, 2017, from a small suburban area (5km × 2km) of the city of Beijing, China. There were 72 types of semi-volatile organic compounds (SVOCs) found in these runoff samples, including 33 types of monocyclic aromatic hydrocarbons (MAHs), 22 types of polycyclic aromatic hydrocarbons (PAHs), 6 types of phthalate esters (PAEs), 9 types of pesticides and 2 types of polychlorinated biphenyls (PCBs). Especially, 26 types of SVOCs (7 MAHs, 9 PAHs, 5 PAEs, and 5 pesticides) were detected in all water samples. SVOCs concentrations were higher in the samples from gas station and city road, and lower in runoff from campus, park and residential sites. The change in the ratio of anthracene to anthracene plus phenanthrene (ANT/(ANT + PHE)) in this study, reflected the importance of PAH source and land use. Di-2-ethylhexyl phthalate (DEHP) and di-n-butyl phthalate, are two of the phthalate esters 100% detected in the runoff samples. The city road runoff DEHP concentrations recorded the highest values (> 6000ng/L), however, were still less than those wastewater DEHP pollutants measured in developed countries (e.g. UK, Canada, Finland, etc.). One-way ANOVA analysis in this study, showed that land use could significantly influence 23 SVOCs in the runoff samples, whereas the runoff SVOCs in different precipitation period showed no statistical changes in the five sites, and presented a general temporal trends "high (beginning)-low (middle period)-little raising (ending)". The findings in this study could be used in municipal management of wastewater collection and treatment.