Concentrations, phase exchanges and source apportionment of polycyclic aromatic hydrocarbons (PAHs) In Bursa-Turkey.

The present study aimed to determine the pollution levels derived from polycyclic aromatic hydrocarbons (PAHs) in air, plant and soil samples and to reveal the PAH exchange at the soil-air, soil-plant and plant-air interfaces. In this context, air and soil samples were collected in approximately 10-day periods between June 2021 and February 2022 from a semi-urban area in Bursa, an industrial city with a dense population. Also, plant branch samples were collected for the last three months. Total PAH concentrations in the atmosphere (∑16PAH) and soil (∑14PAH) ranged from 4.03 to 64.6 ng/m3 and 13-189.4 ng/g DM, respectively. PAH levels in the tree branches varied between 256.6 and 419.75 ng/g DM. In all air and soil samples, PAH levels were low in the summer and reached higher values in the winter. 3-ring PAHs were the dominant compounds, and their distribution in air and soil samples varied between 28.9%-71.9% and 22.8%-57.7%, respectively. According to the results of diagnostic ratios (DRs) and principal component analysis (PCA), both pyrolytic and petrogenic sources were found to be effective in PAH pollution in the sampling region. The fugacity fraction (ff) ratio and net flux (Fnet) values indicated that the direction of movement of PAHs was from soil to air. In order to better understand the PAH movement in the environment, soil-plant exchange calculations were also achieved. The ratio of ∑14PAH values measured to modeled concentrations (1.19

PAHs, PCBs and OCPs in olive oil during the fruit ripening period of olive fruits.

Because of their possible carcinogenic effects, it is crucial to determine levels of polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) in olive oils. However, there are a few studies about these pollutants' levels in olive oils and no other studies reported PAHs, PCBs and OCPs at the same time and during the ripening period of olives in olive oils. A modified clean-up technique was successfully applied for eliminating lipidic components. Additionally, this study does not just report the concentrations of these pollutants but also inspects the sources depending on the actual sampling site. Also, PCBs and OCPs carcinogenic risks in olive oil were reported for the first time in the literature. This study aims to present levels, carcinogenic risks, sources and concentration changes during the ripening period of these pollutants in olive oil. For this purpose, fruit samples for oil extraction were collected between the beginning of the fruit ripening and harvest period. Obtained olive oils from the fruits were extracted and cleaned up using the QuEChERS method. GC-MS and GC-ECD were used for the quantitative analysis of the targeted pollutants. The average concentrations for ∑16PAHs, ∑37PCBs and ∑10OCPs were 222.48 ± 133.76 µg/kg, 58.26 ± 21.64 µg/kg and 25.48 ± 19.55 µg/kg, respectively. During the harvest period, the concentrations were in a decreasing trend. Calculated carcinogenic risks were above acceptable limits for all groups and traffic, wood-coal burning, atmospheric transport and previous uses were the main sources. Results of the source determination indicated that some possible sources could be prevented with regulations and precautions.

Accumulations and temporal trends of polychlorinated biphenyls (PCBs) in olive tree components.

In this study, ambient air samples, olive tree branches (1- and 2-year-old) and their leaves (particulate and dissolved phase) were collected simultaneously between January and December months at a suburban site of Bursa-Turkey. Total polychlorinated biphenyl (PCB) concentrations, sampled by employing passive air samplers, ranged from 0.03 to 0.08 ng/m3 in the atmosphere. The average annual total PCB concentrations belonging to the tree components were 1.14 ± 0.32 ng/g DM in dissolved phase in leaves, 0.71 ± 0.32 ng/g DM in particle phase on leaves, 1.06 ± 0.25 ng/g DM in 1-year-old branches, and 0.93 ± 0.23 ng/g DM in 2-year-old branches. It was determined that the correlation between PCB concentrations in olive tree components and the air was low. This result indicated that besides the tree-air exchange, other possible factors (such as soil-to-tree transitions, wind effect, etc.) affect the levels of PCB concentrations in the tree components. Total PCB concentrations decreased from summer to winter in all samples. The percentage ratio of PCB in the dissolved phase in the leaves was generally higher than other tree components in seasons. PCB homologous distributions indicated 5-CBs were dominant in the tree components and 3-CBs were dominant in the air samples. Highly chlorinated PCB congeners (8-CBs and 9-CBs) were found at low concentrations in both air and tree components samples. The samples indicated that the ratio of PCBs in tree components to the total (tree component+ambient air) PCBs slightly increased with increasing the chlorine number.

Characterization, source apportionment, air/plant partitioning and cancer risk assessment of atmospheric PAHs measured with tree components and passive air sampler.

In this study, ambient air and olive tree components (leaf and branch) were simultaneously collected and analyzed for polycyclic aromatic hydrocarbons (PAHs) to investigate their levels and accumulations, temporal variations, possible sources, air-plant partitioning and cancer risks for 12 months. During the sampling period, total of 14 PAH (∑14PAH) concentrations measured in the olive leaves (dissolved and particle phase) and braches (1- and 2-year-old) were 593 ± 472, 81 ± 67, 558 ± 273 and 316 ± 213 ng/g dry weight (DW), respectively. Similarly, the average ∑14PAH concentrations measured in the ambient air was found to be 15 ± 16 ng/m3. Generally, 4-, 5- and 6- ring PAHs were the dominant groups for all tree components, while 2- and 3-ring PAHs were predominant in the air samples. Ring distributions and molecular diagnosis ratios were employed to determine PAH sources in the sampling site. Petroleum and combustion-related sources were found to be important. The Pearson correlation coefficient was allowed to figure out the affinity between PAH levels in the sampling materials and meteorological factors. Temperature and mixing layer height were found to be effective factors on the concentrations. Atmospheric PAH levels were also predicted to employ a bark-air exchange model for determining the PAH movement direction. The predicted/measured ratios were above 1.0. This was probably due to utilizing the branch values rather than bark values in the model. Finally, the risk of cancer has been evaluated. The calculated cancer risks via inhalation were at low levels for adults and children.

Levels, distributions, and seasonal variations of polycyclic aromatic hydrocarbons (PAHs) in ambient air and pine components.

Pine tree (Pinus pinea) components have been used as passive air samples for determining atmospheric polycyclic aromatic hydrocarbon (PAH) concentrations. Our results indicated that pine needles and branches were found to be statistically successful in describing the ambient air. Monthly pine needles, branches (1- and 2-year-old) and ambient air samples were collected for 1 year to identify molecular distributions and temporal concentrations of PAHs in a suburban-industrial area. Annual average Σ14PAH concentrations for pine needles, 1- and 2-year-old branches, and ambient air were 756 ± 232 ng/g DW, 685 ± 350 ng/g DW, 587 ± 361 ng/g DW, and 28.29 ± 32.33 ng/m3, respectively. The order of average Σ14PAH concentrations in the pine tree components was determined as needle > 1-year-old branch > 2-year-old branch. In general, concentrations increased with the rise in the surface area of tree components. In the samples, 3- and 4-ring PAHs were dominant compounds in the ambient air, pine needles, and branches. The annual total fraction of 3- and 4-ring PAHs in the air was 98.5%, while the fraction of 5- and 6-ring PAHs was 1.5%. On the other hand, 3- and 4-ring PAHs in pine needles and branches were 30% or more. The fraction and level of PAHs change with the season. Although needle samples did not show any seasonal trend, PAH levels in other tree components changed with the air temperature. Generally, lower values were observed in warmer seasons in the branch samples. Similarly, ambient air PAH concentrations were higher in the winter season due to heating and adverse meteorological conditions.

Biomonitoring and Source Identification of Polycyclic Aromatic Hydrocarbons (PAHs) Using Pine Tree Components from Three Different Sites in Bursa, Turkey.

Pine trees are used as biomonitoring agents to evaluate atmospheric polycyclic aromatic hydrocarbons (PAHs). Due to industrialization, urban construction, and rapid population growth, the city of Bursa is experiencing air pollution. In this study, PAHs were measured in pine tree branches and needles at a wastewater treatment plant site, an industrial site, and semirural site in Bursa for 12 months. The concentrations fluctuated depending on the characteristics of the areas. The lowest concentration value was measured in the semirural site while the highest value was determined in the wastewater treatment plant site. The PAH concentrations in pine needles ranged from 24 to 2565 ng/g dry weight (DW) and in pine branches from 163 to 2871 ng/g DW for 16 PAHs. Naphthalene, phenanthrene, fluorene, and fluoranthene were determined as dominant species in both tree components. Diagnostic ratios, ring profile, principal component analysis, the coefficient of divergence, and the Pearson correlation coefficient methods were used in the definition of sources of PAHs in the sampling sites, although all source identification methods have advantages and disadvantages. According to the results, the PAHs mainly originated from biomass and coal burning, traffic, and mixed sources. It also was concluded that three sampling sites showed higher PAH concentrations during winter, and the main PAH sources were similar.

Atmospheric concentration, source identification, and health risk assessment of persistent organic pollutants (POPs) in two countries: Peru and Turkey.

It is known that some persistent organic pollutants (POPs) are used worldwide, and these pollutants are dangerous for human health. However, there are still countries where measurements of these pollutants have not been adequately measured. Although many studies have been published for determining the concentrations of POPs in Turkey, there are limited studies in Latin American countries like Peru. For this reason, it is essential both to conduct a study in Peru and to compare the study with another country. This study is aimed at determining the atmospheric POPs such as polycyclic aromatic hydrocarbon (PAH), organochlorine pesticide (OCP), and polychlorinated biphenyl (PCB) concentrations using passive air samplers in Yurimaguas (Peru) and Bursa (Turkey). Molecular diagnosis ratios and ring distribution methods were used to determine the sources of PAHs. According to these methods, coal and biomass combustions were among the primary sources of PAHs in Peru, while petrogenic and petroleum were the primary sources of PAHs in Turkey. Then, α-HCH/γ-HCH and ß-/(α+γ)-HCH ratios were used to determine the sources of OCPs. According to the α-HCH/γ-HCH ratios, the primary sources of OCPs in both countries were lindane. Similarly, according to ß-/(α+γ)-HCH ratios, the HCHs have been historically used in Peru while they were recently utilized in Turkey. Finally, homologous group distributions were used to determine the sources of PCBs. Similar distributions of homologous groups were observed in the sampling sites in both countries. Also, the homologous group distributions obtained have been determined that industrial activities could be effective in the sampling areas in both countries. When the cancer risks that could occur via inhalation were evaluated, no significant cancer risk has been determined in both countries.

Assessments of seasonal trend, gas-particle partitioning and deposition flux of polycyclic aromatic hydrocarbons at a semi-rural site.

Air samples were collected at a semi-rural area between February 2013 and February 2014 to determine the concentrations and gas/particle partitionings of polycyclic aromatic hydrocarbons (PAHs). The sampling was done with a high volume air sampler to cover four seasons and 40 samples were taken. Each sample period was about 24 h. The gas-particle partition coefficients (Kp) of PAHs were calculated and correlated with their subcooled liquid vapor pressures ( PL0 ). The determined slopes (mL) varying from -0.59 to -0.28 were far from the theoretical value (-1) due to the absorption, the dominant mechanism. Experimentally determined Kp values were compared with the results obtained using the octanol-air and soot-octanol partitioning models. An octanol-based absorptive partitioning model resulted in a better prediction than the soot-octanol based partitioning model. The total (gas + particle) PAH concentrations changed between 6 and 798 ng m-3 with an average of 205 ± 236 ng m-3. According to Clausius-Clapeyron equation, the local PAH sources were effective. The diagnostic ratios indicated that coal and wood-burning, and traffic emissions were the dominant PAH sources. Dry deposition fluxes for gas and particle phase were also estimated using documented dry deposition velocities and mass transfer coefficients in the literature and concentrations measured in this study.

Atmospheric Deposition of Organochlorine Pesticides (OCPs): Species, Levels, Diurnal and Seasonal Fluctuations, Transfer Velocities.

Organochlorine pesticides (OCPs) in the persistent organic pollutants class are pollutants that can enter water reservoirs, soils, and sediments by atmospheric deposition. The aim of the present study was to determine the total atmospheric deposition fluxes of OCPs in a semi-rural area in Bursa, Turkey. Total deposition fluxes, phase distributions, dry deposition velocities and mass transfer coefficients were calculated in the samples collected during day and night periods. Ambient air OCP samples were also taken simultaneously. Samples were analyzed for 9 OCP compounds (alpha-, beta-, and gamma-hexachlorocyclohexane; heptachlor epoxide; endrin; endosulfan beta; endrin aldehyde; and methoxychlor). OCPs were found predominantly in gas and dissolved phases in all seasons for the ambient air and deposition samples, respectively. The annual maximum averages of deposition fluxes for dissolved and particulate phases for the beta-HCH compound were 200.2 ng/m2-day and 28.6 ng/m2-day, respectively. The average dry deposition velocity and mass transfer coefficient values calculated for OCPs were 4.6 ± 5.5 cm/s and 0.46 ± 0.37 cm/s, respectively, and these values were in line with the values in the literature. In the nighttime and daytime samples, the average deposition fluxes of OCP compounds in the dissolved phase were 1.5-10 times higher than those in the particulate phase. Although there were no great differences in daytime and nighttime samples, it was found that the flux values during daytime periods were sometimes higher.

Effects of sampling interval on the passive air sampling of atmospheric PCBs levels.

In this study, we collected Polychlorinated biphenyls (PCBs) using passive air samplers (PASs), between February 4, 2013 and February 2, 2014, with the sampling periods ranging from 10 to 60 days. The samples were collected with PASs that contained polyurethane foam (PUF). With these samples, 87 PCB congeners were analyzed. Sampling coefficient (R) values for the four seasons were calculated using both the high volume air sampler (HVAS) and PAS samples collected with the same time interval. The average of the annual concentrations of 87 PCB congeners, calculated using the R values specific to this study, was 234 ± 175 pg/m3. PCB congeners with 3- and 4- chlorines were dominant. The samples were collected at the same time interval but at different times to represent accumulation in the PASs. The linear regression coefficients (r) of the PCB mass accumulated in PASs against time ranged from 0.89 and 0.97 indicating that accumulation was linear. Moreover, the concentrations of the PCB congeners were statistically correlated with atmospheric conditions.

Evaluation and application of a passive air sampler for polycylic aromatic hydrocarbons (PAHs).

Sampling of 15 PAHs by the use of both passive air sampler developed (D-PAS) in our research group and PAS (C-PAS) having widespread use in the literature was conducted to compare the performances of the samplers. Sampling was carried out for 1-year period (February 2013-February 2014), in different sampling periods by employing D-PAS and C-PAS. D-PAS and C-PAS were run in parallel for 10, 20, 30, 40 and 60 days. Sampling rates were calculated for both PASs by the use of concentration values obtained from a high-volume air sampler (HVAS). It was determined that calculated sampling values are different from each other by definition of design of C-PAS and D-PAS and difference in environment as velocity of wind and temperature are having different effects upon sampling rates. Collected σ15PAHs amounts of 10-day periods in spring, summer, autumn and winter were obtained as 576 ± 333, 209 ± 29, 2402 ± 910 and 664 ± 246 ng for D-PAS and 1070 ± 522, 318 ± 292, 6062 ± 1501 and 6089 ± 4018 ng for C-PAS, respectively. In addition, according to seasons, when collected PAHs in two different samplers were considered, similar results were obtained for the summer time in which no combustion takes place with the aim of domestic heating, while there were differences determined for the seasons with combustion in need of domestic heating. Gas-phase σ15PAHs' concentrations were reported depending on seasons in the spring, summer, autumn and winter sequences as 46 ± 32, 9 ± 3, 367 ± 207 and 127 ± 93 ng m-3 for HVAS, respectively.

Determination of Atmospheric PCB Level Variations in Continuously Collected Samples.

Polychlorinated biphenyls (PCBs) were measured in ambient air samples (n = 48) that were collected for a 2- to 3-day period in each season (winter, spring, summer, fall) of 2013. The samples were collected on the Campus of Uludag University, which is in a semirural region. The samples were collected using a high-volume air sampler. The gas and particle phase concentrations of 87 PCB congeners (Σ87PCB) were measured in these samples. The average gas and particle phase concentrations of the Σ87PCB were calculated to be 293 ± 257 and 52 ± 56 ng/m(3), respectively. However, the results of short-term measurements showed that the variation among the measurements in the gas phase was up to 39-fold and up to 84-fold in the particle phase. These results demonstrated that the ambient air PCB concentrations were not stable and changed dramatically on a daily basis. Therefore, it was clear that a small number of samples could not be representative of the entire region. Furthermore, the obtained concentrations showed differences that depended on the meteorological conditions and long distance transportation. The sampling indicated that PCB homologues with 3 or 4 chlorines were dominant.

Monitoring of Long-Term Outdoor Concentrations of PAHs with Passive Air Samplers and Comparison with Meteorological Data.

The passive air sampler (PAS) is a common and useful tool for the sampling of semivolatile organic compounds in the ambient air. In a study performed in a semirural area of Bursa, sampling of polycyclic aromatic hydrocarbons (PAHs), was completed between February 4, 2013, and February 3, 2014, during 10-, 20-, 30-, 40- and 60 day periods for 1 year. To determine polycyclic aromatic compounds (PAH) concentrations, 3 PASs and 1 high-volume air sampler were run simultaneously, and sampling rates (R [m(3)/d]) were calculated seasonally and according to the ring numbers of the PAHs. R values varied from 0.66 to 22.41 m(3)/d. The relationship of these values with meteorological conditions was examined statistically, and the regressions performed were found to be consistent. This study identified 15 PAH compounds [Formula: see text]. Concentration values of 10 day samples fluctuated from 6.4 to 1100 ng/m(3). Seasonal averages of the concentrations of ∑15PAHs were detected to be 141 ± 72.5 ng/m(3) for winter, 74 ± 59 ng/m(3) for spring, 7 ± 0.6 ng/m(3) for summer and 840 ± 170 ng/m(3) for autumn. In this study, the toxicity equivalents of seasonal PAH concentrations obtained were determined to be 0.5, 0.3, 0.1, and 1.8 ng/m(3) in winter, spring, summer and fall, respectively. The type posing a cancer risk has been identified as BaA.

Concentrations, gas-particle partitioning, and seasonal variations of polycyclic aromatic hydrocarbons at four sites in Turkey.

Ambient air polycyclic aromatic hydrocarbon (PAH) samples were collected at traffic, residential, coastal, and semiurban sites in Bursa, Turkey, between June 2008 and June 2009. For the traffic, residential, coastal, and semiurban sites, the average gas phase total PAH (∑12PAH) concentrations were 113 ± 131, 142 ± 204, 53 ± 73, and 19 ± 34 ng/m(3), respectively, whereas the average particle phase total PAH concentrations were 28 ± 36, 56 ± 85, 24 ± 40, and 11 ± 23 ng/m(3), respectively. Phenanthrene and fluoranthene had the highest concentrations of all of the sampling sites in the gas phase. The PAH concentrations in the heating period were 5-7 times greater than the nonheating period concentrations. Principal component analysis (PCA) was used to investigate the relationship between the levels of PAHs determined in ambient samples and their possible sources. The PCA model shows that coal combustion and vehicle emissions affected PAH emissions. Moreover, the molecular diagnostic ratios indicated that coal-burning and traffic emissions were the dominant PAH sources. The multiple linear regression analysis indicated that the meteorological parameters also affected the ambient PAH concentrations. The sampling site characteristics, meteorological conditions, dispersion, and local sources all affected the concentration levels.

Migration of polycyclic aromatic hydrocarbons (PAHs) in urban treatment sludge to the air during PAH removal applications.

In the present study, the amounts of polycylic aromatic hydrocarbons (PAHs) penetrating into air during PAH removal applications from the urban treatment sludge were investigated. The effects of the temperature, photocatalyst type, and dose on the PAH removal efficiencies and PAH evaporation were explained. The sludge samples were taken from an urban wastewater treatment plant located in the city of Bursa, with 585,000 equivalent population. The ultraviolet C (UV-C) light of 254 nm wavelength was used within the UV applications performed on a specially designed setup. Internal air of the setup was vacuumed through polyurethane foam (PUF) columns in order to collect the evaporated PAHs from the sludge during the PAH removal applications. All experiments were performed with three repetitions. The PAH concentrations were measured by gas chromatography-mass spectrometry (GC-MS). It was observed that the amounts of PAHs penetrating into the air were increased with increase of temperature, and more than 80% of PAHs migrated to the air consisted of 3-ring compounds during the UV and UV-diethylamine (DEA) experiments at 38 and 53 degrees C. It was determined that 40% decrease was ensured in sigma12 (total of 12) PAH amounts with UV application and 13% of PAHs in sludge penetrated into the air. In the UV-TiO2 applications, a maximum 80% of sigma12 PAH removal was obtained by adding 0.5% TiO2 of dry weight of sludge. The quantity of PAH penetrating into air did not exceed 15%. UV-TiO2 applications ensured high levels of PAH removal in the sludge and also reduced the quantity of PAH penetrating into the air. Within the scope of the samples added with DEA, there was no increase in PAH removal efficiencies and the penetration of PAHs into air was not decreased. In light of these data, it was concluded that UV-TiO2 application is the most suitable PAH removal alternative that restricts the convection of PAH pollution.

Temporal and spatial variations in PAH concentrations in the sediment from the Nilufer Creek in Bursa, Turkey.

The objective of this study was to identify the temporal variations in PAH concentrations in the sediment at different locations on the Nilufer Creek moving along an industrial city. The distribution of various PAH species and their possible sources were determined. Sediment samples were taken from at eight different locations on the Nilufer Creek for a one-year period. Temporal concentration profiles were in the range of 15-9600 ng g(-1) dry matter (dm). PAH concentrations reached their maximum values in the winter (9600 ng g(-1) dm). Molecular diagnostic ratios of PAHs showed that the pollution in the Nilufer Creek in the fall, winter and summer seasons was mostly pyrolytic. It was observed that 3-4 ring species predominated in all seasons in the Nilufer Creek sediment.

Application of various methods for removal of polycyclic aromatic hydrocarbons from synthetic solid matrices.

In the present study, removal of polycyclic aromatic hydrocarbons (PAHs) from synthetic solid matrices with various methods was investigated. PAH removal experiments were conducted in a specifically designed UV apparatus for this study. Polyurethane foams (PUF) cartridges were used to remove PAHs from the incoming air and to capture PAHs from the evaporated gases. Sodium sulphate (Na2SO4) was used as a synthetic solid matrices. The effects of temperature, UV radiation, titanium dioxide (TiO2) and diethylamine (DEA) dose on the PAH removal were determined. TiO2and DEA were added to the Na2SO4 sample at the rate of 5% and 20% of dry weight of samples. PAHs' removal from the Na2SO4 enhanced with increasing temperature. Sigma12 PAH content in the Na2SO4 reduced up to 95% during UV light application. Moreover, the Sigma12 PAH removal ratio was calculated as 95% with using 5% of TiO2, and increasing of TiO2 dose negatively affected PAH removal. PAH concentration in the samples decreased by 93% and 99% with addition of 5% and 20% DEA, respectively. Especially, 3- and 4-ring PAH compounds evaporated during the PAH removal applications. As expected, evaporation mechanism became more effective at high temperature for light PAH compounds. It was concluded that PAHs can successfully be removed from synthetic solid matrices such as Na2 SO4 with the applications of UV light and UV-photocatalysts.

Urban air PCDD/Fs: Atmospheric concentrations, temporal changes, gas/particle partitioning, possible sources and cancer risks.

Polychlorinated dibenzo-p-dioxins/furans (PCDD/Fs) are pollutants of concern due to their toxic effects. No active sampling study on PCDD/Fs has been conducted in Bursa. This study aimed to fill this gap by measuring PCDD/F levels in the region. Accordingly, the samples were collected from an urban area in Bursa, covering four seasons between June 2022 and April 2023. The total (gas+particulate) ambient air concentrations were between 312.23 and 829.80 fg/m3 (mean: 555.05 ± 173.62 fg/m3). In terms of toxic equivalents (TEQ), the average concentration was 43.29 ± 9.18 fg WHOTEQ/m3. Based on the concentration values obtained, cancer and non-carcinogenic risk values of PCDD/Fs were calculated for three different age groups. The results indicated negligible health risks for all age groups. In addition, a seasonal assessment was also made and it was observed that PCDD/F concentration values varied with the ambient air temperatures. In general, higher values were measured in colder months compared to warmer months. This was probably due to the additional sources and adverse meteorological conditions. Moreover, the gas/particle partitioning of PCDD/Fs was investigated in detail. The average gas and particulate phase concentrations for PCDD/Fs were 101.81 ± 20.77 and 453.24 ± 172.50, respectively. It was found that an equilibrium state was not reached in the gas/particle partitioning. Two different gas/particle partition models based on adsorption and absorption mechanisms were compared, and the absorption model gave more consistent predictions. The Principal Component Analysis (PCA) was employed to identify the possible PCDD/F sources. The results indicated that the region was influenced by vehicle emissions, residential heating, organized industrial zones and metal recycling facilities. In addition, 72-hour backward air mass trajectory analyses were performed to understand the long-range transported air masses. However, it was found that the transported air masses did not significantly affect the concentration values measured in the sampling site.

Urban air PCDD/Fs: Dry deposition fluxes and mass transfer coefficients determined using a water surface sampler.

Polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) cause significant environmental concerns. Atmospheric PCDD/Fs permeate water bodies and other ecosystems through wet and dry deposition. In an urban site, dry deposition flux samples of gaseous phase PCDD/Fs were collected by a water surface sampler (WSS) operated between June 2022 and June 2023. There is a conspicuous absence of literature on the direct measurement of dry deposition flux levels in the gaseous phase of PCDD/Fs. In the study, PCDD/Fs in the gas phase reaching the WSS dissolved in the water according to Henry's Law. The PCDD/Fs in the water were transferred to an XAD-2 resin column, sorbing the dissolved PCDD/Fs. The average monthly gas phase dry deposition flux was 34.07 ± 9.35 pg/m2-day (7.35 ± 2.16 pg I-TEQ/m2-day). The highest flux was measured in March (49.53 pg/m2-day), and the lowest was in August (18.64 pg/m2-day). These values indicated the direct flux from air to water. The atmospheric concentration of the gas-phase ranged from 68.38 to 126.88 fg/m3 (13.22-25.01 fg I-TEQ/m3). Dry deposition fluxes and concentrations of atmospheric PCDD/Fs were bigger in the colder months than in the warmer months. This was probably due to a significant increase in residential heating during the colder months, decreased photochemical reactions, and lower mixing heights. Regarding congeners in the dry deposition flux and concentration values in I-TEQ units, 2,3,7,8-TCDD compound predominated with the proportions of 31.61 ± 7.76% and 29.09 ± 12.34%, respectively. Concurrently measured dry deposition flux (Fg) and ambient air concentration (Cg) of PCDD/Fs were considered in the determination of mass transfer coefficient (MTC = Fg/Cg) calculation for each PCDD/F congener. The average MTC for targeted 17 PCDD/Fs was 0.45 ± 0.15 cm/s, and it fluctuated between 0.89 ± 0.30 cm/s for 2,3,7,8-TCDF and 0.2 ± 0.16 cm/s for OCDD.

Gas/particle partitioning of PCDD/Fs: Distributions and implications for available models.

Polychlorinated dibenzo-p-dioxins/furans (PCDD/Fs) are semi-volatile organic compounds (SVOCs) existing in the atmosphere in the gas and particulate phase, remain persistent for a long time and pose a high risk to the environment and human health. In this study, PCDD/F measurements were made in an urban area between June 2022 and April 2023. In order to understand the fate of PCDD/Fs, the gas/particle (G/P) partitioning was studied. Although various models have been developed to determine the G/P partitioning of SVOCs, only logKp-logPL0, Junge-Pankow and Harner-Bidleman models are generally used for PCDD/Fs. In this study, nine different models (Junge-Pankow, Harner-Bidleman, Dachs-Eisenreich, Li-Ma-Yang, pp-LFER, mp-pp-LFER, QSPR, logKp-logPL0, logKp-logKOA) were employed to determine the G/P partitioning. To the best of our knowledge, pp-LFER, mp-pp-LFER and QSPR models were evaluated for PCDD/Fs for the first time in this study. In addition, the performance of the models within the equilibrium (EQ), non-equilibrium (NE) and maximum partitioning (MP) domain was investigated for PCDD/Fs for the first time in this study. Accordingly, models based on absorption in the EQ domain, adsorption in the NE domain and adsorption and absorption mechanisms in the MP domain were found to be effective in explaining the G/P transitions. It was determined that there is no equilibrium situation in the G/P partitioning. The Junge-Pankow, pp-LFER, Li-Ma-Yang and QSPR models under-predicted the particle fraction values while the other models showed a high prediction profile. The Li-Ma-Yang model showed the closest results to the measured particle fraction values, and it determined that deposition mechanisms are of non-negligible importance in the G/P partitioning of PCDD/Fs. One of the new models, the pp-LFER model, has shown remarkable success at high logKOA values. The mp-pp-LFER model, which overestimated the contribution of the adsorption mechanism, showed a very high prediction profile compared to the measured values.