Seasonal and height dynamics of volatile organic compounds in rubber plantation: Impacts on ozone and secondary organic aerosol formation.

Rubber trees emit a range of volatile organic compounds (VOCs), including isoprene, monoterpenes, and sesquiterpenes, as part of their natural metabolism. These VOCs can significantly influence air quality through photochemical reactions that produce ozone and secondary organic aerosols (SOAs). This study examines the impact of VOCs detected in a rubber tree plantation in Northeastern Thailand on air quality, highlighting their role in atmospheric reactions that lead to the formation of ozone and SOAs. VOCs were collected at varying heights and seasons using Tenax-TA tubes paired with an atmospheric sampler pump and identified by gas chromatography-mass spectrometry. In total, 100 VOCs were identified, including alkanes, alkenes, terpenes, aromatics, and oxygenated VOCs. Principal Coordinate Analysis (PCoA) revealed distinct seasonal VOC profiles, with hydrocarbons, peaking in summer and terpenes in the rainy season. The Linear Mixed-Effects (LME) model indicates that VOC concentrations are more influenced by seasonal changes than by sampling heights. Secondary organic aerosol potential (SOAP) and ozone formation potential (OFP) of selected VOC species were also determined. The total SOAP ranged from 67.24 µg/m3 in summer to 17.87 µg/m3 in winter, while the total OFP ranged from 377.87 µg/m3 in summer to 139.39 µg/m3 in winter. Additionally, positive matrix factorization (PMF) analysis identified four main VOC sources: gasoline combustion (18.3 %), microbial activity (38.6 %), monoterpene emissions during latex production (15.0 %), and industrial sources (28.1 %). These findings provide essential information for managing air pollution in rubber tree plantations. By adopting focused air quality management strategies, plantation operators can mitigate the adverse effects of VOCs, promoting a healthier and more sustainable future.

Correction: Combined use of principal component analysis/multiple linear regression analysis and artificial neural network to assess the impact of meteorological parameters on fluctuation of selected PM2.5-bound elements.

[This corrects the article DOI: 10.1371/journal.pone.0287187.].

Combined use of principal component analysis/multiple linear regression analysis and artificial neural network to assess the impact of meteorological parameters on fluctuation of selected PM2.5-bound elements.

Based on the data of the State of Global Air (2020), air quality deterioration in Thailand has caused ~32,000 premature deaths, while the World Health Organization evaluated that air pollutants can decrease the life expectancy in the country by two years. PM2.5 was collected at three air quality observatory sites in Chiang-Mai, Bangkok, and Phuket, Thailand, from July 2020 to June 2021. The concentrations of 25 elements (Na, Mg, Al, Si, S, Cl, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, As, Se, Br, Sr, Ba, and Pb) were quantitatively characterised using energy-dispersive X-ray fluorescence spectrometry. Potential adverse health impacts of some element exposures from inhaling PM2.5 were estimated by employing the hazard quotient and excess lifetime cancer risk. Higher cancer risks were detected in PM2.5 samples collected at the sampling site in Bangkok, indicating that vehicle exhaust adversely impacts human health. Principal component analysis suggests that traffic emissions, crustal inputs coupled with maritime aerosols, and construction dust were the three main potential sources of PM2.5. Artificial neural networks underlined agricultural waste burning and relative humidity as two major factors controlling the air quality of Thailand.

Applying synchrotron radiation-based attenuated total reflection-fourier transform infrared to chemically characterise organic functional groups in terrestrial soils of King George Island, Antarctica.

Anthropogenic activities, especially associated with fossil fuel combustion, are raising concerns worldwide, but remote areas with extreme climate conditions, such as Antarctica, are isolated from the adverse influence of human civilisation. Antarctica is considered as the most untouched place on Earth. Such pristine areas, which have extremely low chemical pollutant concentrations owing to restricted anthropogenic impacts, exemplify plausible model environments to test the reliability and sensitivity of advanced analytical techniques employed to chemically characterise and evaluate the spatial distribution of chemical pollutants. Here, synchrotron radiation-based attenuated total reflection-Fourier transform infrared (SR-ATR-FTIR) spectroscopy was employed to evaluate the variations in the organic functional groups (OFGs) of terrestrial soils of King George Island, Antarctica. Second-derivative SR-ATR-FTIR spectroscopy coupled with several multivariate statistical techniques highlighted the influence of anthropogenic activities on the alterations of OFGs in terrestrial soils collected near airports. Moreover, the daily activities of penguins could also have caused fluctuations in some OFGs of the samples the close to the Tombolo area and Ardley Island. The findings proved the effectiveness of SR-ATR-FTIR in evaluating the potential sources of variations in the chemical constituents, especially OFGs, in Antarctic terrestrial soils.

Source appointment and health risk assessment of polycyclic aromatic hydrocarbons in paddy grain from Thailand and Laos.

Rice is a staple meal for the majority of Asians. However, human exposure to polycyclic aromatic hydrocarbons from paddy grain is largely unknown in Thailand and Laos. Therefore, information on the quantitative measurement and assessment of the health problems caused by PAHs was analyzed. The results showed that the concentrations of total PAHs in paddy grain in Thailand and Laos were 38.86 ± 5.13 and 11.35 ± 1.96 ng g-1, respectively. The highest concentration of PAHs in Thailand was B[k]F, whereas D[a,h]A was found to be the highest in Laos. A p-value less than 0.05 was defined, which showed B[b]F and B[k]F from Thailand and Laos were significant, which indicated that they could be from a different pollutant source. The main finding of this study, which was supported by the diagnostic ratios of PAHs and HCA, was that the primary source of PAHs was assumed to be incomplete combustion of petroleum products, which was caused by the burning of industrial fuels or vehicle exhausts, as well as open burning. The findings suggest that these two nations have similar PAH origins. Agricultural waste burning and transportation emissions are well-known sources of PAHs in Thailand and Laos. The cancer risk assessment method was based on the accumulation of PAHs from paddy grains. An ILCR of 1.0E-06 to 1.0E-04 was considered a tolerable limit of cancer risk, while a risk > 1.0E-04 was considered a concern in terms of cancer risk. The findings indicated that while PAH emissions exist, their contribution to global toxicity may be anticipated to be low in inhalation exposure. The higher values of ingestion and dermal risk estimated were regarded as the tolerable limit of cancer risk in children and adults from both countries, indicating that cancer risk in both nations falls within the "acceptable level" range.

Concentrations and source identification of priority polycyclic aromatic hydrocarbons in sediment cores from south and northeast Thailand.

In this study, the environmental fate of carcinogenic polycyclic aromatic hydrocarbons (PAHs) in tropical lake sediments and their potential sources have been discussed. 15 PAHs (i.e. ΣPAH) have been investigated in two lakes, namely Songkhla Lake (SKL) and Nong Han Kumphawapi Lake (NHL), which are located at the southern and north-eastern parts of Thailand, respectively. Since these two lakes are registered as important wetlands under the Ramsar convention (United Nations Educational, Scientific and Cultural Organization: UNESCO), the quantitative identification of potential contributors of PAHs is an inevitable analytical tool for launching an evidence-based policy. The ΣPAH concentrations observed in SKL and NHL sediments (n = 135) were in the range of 19.4-1,218 ng g-1 and 94.5-1,112 ng g-1, respectively. While the exponential decline of ΣPAH contents were detected in SKL sediments, NHL showed a trend of enhancing PAH contents with depth. The averaged benzo [a]pyrene (B [a]P) contents of surface sediments in both lakes were much below the value stipulated by the United States Environmental Protection Agency (US-EPA) guidelines for carcinogen risk assessment. Based on numerous multivariate statistical techniques coupled with source apportionment analysis, "biomass burning" and "anthropogenic activities" are two potential contributors of the PAHs detected in the study areas. To achieve the long-term conservation of nature with related ecosystem services and cultural values, it is therefore important to promote decision-making based on ecotoxicological studies of carcinogenic substances.

Discrimination of the geographical origins of rice based on polycyclic aromatic hydrocarbons.

Over the past few decades, several techniques have been applied to identify the geographical origins of rice products. In this study, the chemical characterization of polycyclic aromatic hydrocarbons (PAHs) was carefully conducted by analysing PAHs in rice samples collected from private sector planting areas located in Bali and Yogyakarta, Indonesia (i.e. ID; n = 20), west sides of Malaysia (i.e. MY; n = 20), Mandalay, Legend, Myingyan, Myanmar (i.e. MM; n = 20), northern parts of Lao PDR (i.e. LA; n = 20), central parts of Cambodia (i.e. KH; n = 20), northern parts of Vietnam (i.e. VN; n = 20), and Thailand (i.e. TH; n = 22). Percentage contributions show the exceedingly high abundance of 5-6 ring PAH congeners in rice samples collected from Indonesia, Malaysia, Thailand, Myanmar, Cambodia and Vietnam. Lao PDR rice samples were overwhelmed by 4-ring PAH congeners with the percentage contribution of 46% followed by 5-6 ring PAHs (33%) and 3-ring PAHs (21%). In addition, hierarchical cluster analysis and principal component analysis can successfully categorize some rice samples based on its geographical origins.

An application of aromatic compounds as alternative tracers of tsunami backwash deposits.

This manuscript provides some comprehensive technical insights regarding the application of polycyclic aromatic hydrocarbons (PAHs) characterized by using Gas-Chromatography Mass Spectrometry. Although numerous chemical species such as water soluble ionic species (e.g. Na+, K+, Cl-, Ca2+, Mg2+) and acid leachable heavy metal fractions (e.g. Fe, Cd, Al, Mo, Sb, As, Cu, Zn, Pb, and Mn) can be used to characterize tsunami deposits, the knowledge of PAH congeners as alternative chemical species for identifying tsunami backwash deposits is strictly limited. This manuscript is exclusive because it aims to find some alternative chemical proxies in order to distinguish tsunami backwash deposits from typical marine sediments. A wide range of diagnostic binary ratios of PAH congeners have been selected in order to characterize Typical Marine Sediments (TMS), Tsunami backwash deposits (TBD), Onshore Tsunami Deposits (OTD) and Coastal Zone Soils (CZS). The state of the art and future perspectives coupled with both advantages and disadvantages of above mentioned chemical tracers will be critically reviewed and further discussed.

Spatial distribution, sources and quantitative human health risk assessments of polycyclic aromatic hydrocarbons in urban and suburban soils of Chile.

This work investigated the concentrations and health risks of polycyclic aromatic hydrocarbons (PAHs) found in Chilean soils for the first time. The urban and suburban soils were collected from 28 sampling sites in three regions of Chile: Magallanes (in Punta Arenas commune), Valparaíso and the Santiago metropolitan area. The PAH concentrations, fractions and their potential sources were studied. Statistical analyses using t tests (p < 0.01) showed that (a) PAH concentrations in the urban sites were higher than those in the suburban sites; (b) the presence of anthracene and chrysene was significantly greater in the urban sites than the suburban sites; and (c) the fraction of four-ring PAHs to total PAHs was larger in the urban sites than the suburban sites. The primary PAH source in urban soils was determined to be the combustion of gasoline, grass, wood and coal. In contrast, PAHs in suburban soils were possibly derived from pyrogenic sources (e.g. incomplete combustions). The total cancer risks (TCRs) and the total hazard index (HI) were quantified from 12 PAHs in both urban and suburban soils in terms of cancer and non-cancer risks, respectively. The average TCR of all sites was within an acceptable level (TCR < 10-6), and none of the HIs from any locations were deemed harmful (HI < 1).

A 150-year record of black carbon (soot and char) and polycyclic aromatic compounds deposition in Lake Phayao, north Thailand.

An improved understanding of the historical variation in the emissions and sources (biomass burning, BB vs. fossil fuel, FF combustion) of soot and char, the two components of black carbon (BC), and polycyclic aromatic compounds (PACs) may help in assessing the environmental effects of the Atmospheric Brown Cloud (ABC) in SE Asia. We therefore determined historical variations of the fluxes of soot, char, and PACs (24 polycyclic aromatic hydrocarbons (PAHs), 12 oxygenated PAHs (OPAHs), and 4 azaarenes) in a dated sediment core (covering the past ∼150 years) of Phayao Lake in Thailand. The soot fluxes have been increasing in recent times, but at a far lower rate than previously estimated based on BC emission inventories. This may be associated with a decreasing BB contribution as indicated by the decreasing char fluxes from old to young sediments. The fluxes of high- and low-molecular-weight (HMW and LMW) PAHs, OPAHs, and azaarenes all sharply increased after ∼1980, while the ΣLMW-/ΣHMW-PAHs ratios decreased, further supporting the reduction in BB contribution at the expense of increasing FF combustion emissions. We also suggest that the separate record of char and soot, which has up to now not been done in aerosol studies, is useful to assess the environmental effects of ABC because of the different light-absorbing properties of these two BC components. Our results suggest that besides the establishment of improved FF combustion technology, BB must be further reduced in the SE Asian region in order to weaken the ABC haze.

Quantifying the contributions of local emissions and regional transport to elemental carbon in Thailand.

We used the Weather Research and Forecasting Model coupled with Chemistry (WRF-Chem) to simulate elemental carbon (EC) concentrations in Thailand in 2017. The goals were to quantify the respective contributions of local emissions and regional transport outside Thailand to EC pollution in Thailand, and to identify the most effective emission control strategy for decreasing EC pollution. The simulated EC concentrations in Chiang Mai, Bangkok, and Phuket were comparable with the observation data. The correlation coefficient between the simulated and observed EC concentrations was 0.84, providing a good basis for evaluating EC sources in Thailand. The simulated mean EC concentration over the whole country was the highest (1.38 µg m-3) in spring, and the lowest (0.51 µg m-3) in summer. We conducted several sensitivity simulations to evaluate EC sources. Local emissions (including anthropogenic and biomass burning emissions) and regional transport outside Thailand contributed 81.2% and 18.8% to the annual mean EC concentrations, respectively, indicating that local sources played the dominant role for EC pollution in Thailand. Among the local sources, anthropogenic emissions (including the industry, power plant, residential, and transportation sectors) and biomass burning contributed 75.1% and 6.1% to the annual mean EC concentrations, respectively. As the anthropogenic emissions dominated the EC pollution, we performed four sensitivity simulations by reducing 30% of the emissions from each of the industry, power plant, residential, and transportation sectors in Thailand. The results indicated that controlling transportation emissions in Thailand was the most effective way in reducing the EC pollution. The 30% reduction of transportation emissions decreased the annual mean EC concentrations by 12.1%. In contrast, 30% reductions of the residential, industry, and power plant emissions caused 8.4%, 6.4%, and 4.0% decreases in the annual mean EC concentrations, respectively. The model results could potentially provide useful information for air pollution control strategies in Thailand.

Health risk assessment of polycyclic aromatic hydrocarbons in coastal soils of Koh Samed Island (Thailand) after the oil spill incident in 2013.

Health risks of human exposures to 12 Polycyclic aromatic hydrocarbons (PAHs) in coastal soils of Koh Samed Island (KSI), Thailand, were evaluated after the coastal areas were cleaned up of the 2013 oil-spill contamination. The risk assessment quantified both total cancer and non-cancer risks for four groups of receptors using average PAHs concentrations. Two exposure pathways (incidental ingestion and dermal contact) were selected to evaluate the risks, and three methods were used to calculate the total cancer risks to determine an appropriate assessment method. The non-cancer risk was represented by the total Hazard Index (HI). The contributions of each PAH to the total cancer risk and total HI were also investigated. The total cancer risk (3.53×10-10 to 9.12×10-8) and total HI (4.35×10-6 to 2.13×10-3) from this work were relatively lower than the USEPA baselines (10-6 for the cancer risk and 1 for the HI) and were quite low when compared with other works in the literature. Benzo(a)pyrene made the highest contribution to the total cancer risk (61.82%), while benzo[g,h,i]perylene made the highest contribution to the total HI (62.41%). In regard to the contributions of the two exposure routes, dermal contact contributed the most to the total cancer risk, while incidental ingestion contributed the most to the total HI.

Data relating to spatial distribution of polycyclic aromatic hydrocarbons in terrestrial soils of Pakistan and King George Island, Antarctica.

Over the past few decades, polycyclic aromatic hydrocarbons (PAHs) have been analysed in various environmental compartments, however, only limited information is available associated with their terrestrial concentrations in Pakistan and Antarctica. All terrestrial soils from Pakistan (n = 120) were collected from 14th to 2nd April 2017 at Islamabad (n = 30), Abbotabad (n = 10), Taxilla (n = 5), and other places from north to south (n = 75). All Antarctic terrestrial soils (n = 11) were collected from 1st to 25th February 2018 in the southwestern part of King George Island. It is crucial to underline that all samples were both qualitatively and quantitatively identified by using a Shimadzu GCMS-QP2010 Ultra system coupled with a high-speed performance system with ASSP function (i.e., achieving maximum scan speed of 20,000 u sec-1) and having ultra-fast data acquisition speed for comprehensive two-dimensional gas chromatography (GC × GC). Analytical results implicate the influences of vehicle exhausts as a major contributor of PAHs in terrestrial soils of Pakistan. It seems rationale to conclude that 3-ring PAHs display the majority of PAH congeners in terrestrial soils of King George Island.

Cr(VI) reduction by an extracellular polymeric substance (EPS) produced from a strain of Pseudochrobactrum saccharolyticum.

A better understanding of the Cr(VI) reduction position and mechanisms by a Cr(VI)-reducing strain is important for the bioremediation of Cr pollution in the environment. In the present study, we were interested in figuring out the role of extracellular polymeric substances (EPS) as the main area for Cr(VI) reduction in the newly reported strain of Pseudochrobactrum saccharolyticum LY10. We investigated the subcellular distribution and reduction capability of each cellular component as the main area of Cr(VI) reduction by scanning electron microscopy and soft X-ray spectromicroscopy. The results suggested that most of Cr was presented in the supernatants as Cr(III) after reduction. In the cells, Cr was mostly distributed in the EPS and cell wall, while the EPS had the maximum Cr(VI) reduction rate (81.5%) as compared with the cell wall (30.1%). Soft X-ray spectromicroscopy analysis indicated that Cr accumulated more in the EPS. Therefore, the results suggested that the EPS were the main area for Cr(VI) reduction in the bacteria of P. saccharolyticum LY10.

Data relating to carbonaceous components in Songkhla Lake sediments, Thailand.

The focus of this research was to present a data article associated with organic carbon (OC) and elemental carbon (EC) preserved in lake sediments. Descriptive statistics were applied in this dataset. Sediment cores were sliced immediately at the following layers: 0-20; 20-40; 40-60; 60-80; 80-100; 100-120; 120-140; 140-160; 160-180; 180-200; 200-220; 220-240; 240-260; 260-280; 280-300; 300-320; 320-340; 340-360; 360-380; 380-400; 440-460; 460-480; 480-500; 500-520; 520-540; 540-560 and 560-580 mm of depth. Chemical analysis of OC (i.e. OC1, OC2, OC3, OC4), EC (i.e. EC1, EC2, EC3), and the pyrolyzed organic carbon (OP) (i.e. OP1, OP2, OP3, OP4, OP5, OP6, Char, Soot) contents was conducted by using a DRI Model 2001 Thermal/Optical Carbon Analyzer. The chemical characterization coupled with statistical analysis reveal that vehicle exhausts are the most prominent factor governing OC/EC data detected in core sediments. These data underline some noticeable concerns associated with ecotoxicology and environmental safety of residents surrounding the Songkhla Lake.

Data relating to emissions of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) from industrial boilers.

Polychlorinated-dibenzo-para-dioxins (PCDDs) and Polychlorinated-dibenzofurans (PCDFs) contamination in ecosystems has been a major concern, however, no information is available about the atmospheric contents and emission profiles in different types of fuels from industrial boilers in Thailand, Lao PDR, and Cambodia. Nine air and bottom ash samples (n = 18) were collected from three industrial boilers using U.S.EPA Method 23 and U.S.EPA Method 8290, respectively. All samples were successfully quantified by two High Resolution Chromatography-High Resolution Mass Spectrometry (HRGC-HRMS) namely Waters Autospec Premier and Waters Autospec Ultima. This investigation elucidates the impacts of fuel type on the emissions of PCDDs and PCDFs from three different industrial boilers. It appears plausible to affirm that fuel types play an important role on PCDD/PCDF emission levels from industrial boilers. The results of PCDD/PCDF concentrations should be considered as baseline data for promoting Best Available Technique (BAT) and Best Environmental Practise (BEP) in order to reduce dioxin emissions from industrial boilers in Southeast Asian countries.

Variation in Day-of-Week and Seasonal Concentrations of Atmospheric PM2.5-Bound Metals and Associated Health Risks in Bangkok, Thailand.

While effective analytical techniques to promote the long-term intensive monitoring campaign of particulate heavy metals have been well established, efforts to interpret these toxic chemical contents into policy are lagging behind. In order to ameliorate the interpretation of evidence into policies, environmental scientists and public health practitioners need innovative methods to emphasize messages concerning adverse health effects to state and local policymakers. In this study, three different types of health risk assessment models categorized by exposure pathways. Namely, ingestion, dermal contact, and inhalation were quantitatively evaluated using intensive monitoring data of 51 PM2.5-bound metals that were collected on three consecutive days, from 17 November 2010 to 30 April 2011 in the heart of Bangkok. Although different exposure pathways possess different magnitudes of risk for each PM2.5-bound metal, it can be concluded that ingestion of dust causes more extensive risk to residents compared with inhalation and dermal contact. The investigation of enrichment factors reveals the overwhelming influences of vehicular exhausts on 44 selected metal concentrations in Bangkok. These findings are in agreement with previous studies that highlight the role of public transportation and urban planning in air pollution control.

Assessment of selected metals in the ambient air PM10 in urban sites of Bangkok (Thailand).

Estimating the atmospheric concentrations of PM10-bounded selected metals in urban air is crucial for evaluating adverse health impacts. In the current study, a combination of measurements and multivariate statistical tools was used to investigate the influence of anthropogenic activities on variations in the contents of 18 metals (i.e., Al, Sc, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Cd, Sb, Ba, La, Ce and Pb) in ambient air. The concentrations of PM10-bounded metals were measured simultaneously at eight air quality observatory sites during a half-year period at heavily trafficked roads and in urban residential zones in Bangkok, Thailand. Although the daily average concentrations of Al, V, Cr, Mn and Fe were almost equivalent to those of other urban cities around the world, the contents of the majority of the selected metals were much lower than the existing ambient air quality guidelines and standard limit values. The sequence of average values of selected metals followed the order of Al > Fe > Zn > Cu > Pb > Mn > Ba > V > Sb > Ni > As > Cr > Cd > Se > Ce > La > Co > Sc. The probability distribution function (PDF) plots showed sharp symmetrical bell-shaped curves in V and Cr, indicating that crustal emissions are the predominant sources of these two elements in PM10. The comparatively low coefficients of divergence (COD) that were found in the majority of samples highlight that site-specific effects are of minor importance. A principal component analysis (PCA) revealed that 37.74, 13.51 and 11.32 % of the total variances represent crustal emissions, vehicular exhausts and the wear and tear of brakes and tires, respectively.

Effects of day-of-week trends and vehicle types on PM2.5-bounded carbonaceous compositions.

Carbonaceous compositions of PM2.5 were measured in the heart of Bangkok from 17th November 2010 to 19th January 2012, and a data set of 94 samples was constructed. Effects of day-of-week trends and vehicle types on PM2.5-bound TC, OC, and EC were carefully investigated. In this study, OC was the most important contributor to the total PM2.5 mass concentration. The average PM2.5-bound OC content measured at CHAOS (18.8 ± 9.18 µg m(-3)) was approximately 11 times higher than at Chaumont, Switzerland (1.7 µg m(-3)), but approximately five times lower than at Xi'an, China (93.0 µg m(-3)). The application of diagnostic binary ratios of OC/EC and estimations of secondary organic carbon (SOC) coupled with autocorrelation plots (Box and Jenkins) highlight the enhanced impacts of traffic emissions, especially from diesel vehicles, on PM2.5-bound carbonaceous compositions on weekdays relative to weekends. Hierarchical cluster analysis (HCA) coupled with principal component analysis (PCA) underline the importance of diesel emissions as the primary contributors of carbonaceous aerosols, particularly during weekdays.

Assessment of Reliability when Using Diagnostic Binary Ratios of Polycyclic Aromatic Hydrocarbons in Ambient Air PM10.

The reliability of using diagnostic binary ratios of particulate carcinogenic polycyclic aromatic hydrocarbons (PAHs) as chemical tracers for source characterisation was assessed by collecting PM10 samples from various air quality observatory sites in Thailand. The major objectives of this research were to evaluate the effects of day and night on the alterations of six different PAH diagnostic binary ratios: An/(An + Phe), Fluo/(Fluo + Pyr), B[a]A/(B[a]A + Chry), B[a]P/(B[a]P + B[e]P), Ind/(Ind + B[g,h,i]P), and B[k]F/Ind, and to investigate the impacts of site-specific conditions on the alterations of PAH diagnostic binary ratios by applying the concept of the coefficient of divergence (COD). No significant differences between day and night were found for any of the diagnostic binary ratios of PAHs, which indicates that the photodecomposition process is of minor importance in terms of PAH reduction. Interestingly, comparatively high values of COD for An/(An + Phe) in PM10 collected from sites with heavy traffic and in residential zones underline the influence of heterogeneous reactions triggered by oxidising gaseous species from vehicular exhausts. Therefore, special attention must be paid when interpreting the data of these diagnostic binary ratios, particularly for cases of low-molecular-weight PAHs.