Anthropogenic contribution, transport, and accumulation of Polycyclic Aromatic Hydrocarbons in sediments of the continental shelf and slope in the Mediterranean Sea

A multidisciplinary approach, involving geochemical, sedimentological and oceanographic analyses, was employed to examine the distribution of Polycyclic Aromatic Hydrocarbons (PAHs) in a strongly anthropized area of the marginal Adriatic Sea (Mediterranean basin). The investigation into PAH distribution considered the grain size and biogeochemical properties of the sediments, as well as in relation to the main oceanographic processes and river inputs. Both biogeochemical and hydrographical inputs regulated the sedimentation of organic particles, influencing the distribution of PAHs. The results indicated PAH levels in 116 marine surface sediments ranging from 4 to 235 ng g-1 (average 55 ng g-1). The distribution of PAHs in Adriatic Sea surface sediments aligned with a higher clayey sedimentation in the deeper basin areas of the Middle Adriatic Depression.

On the triad of air PM pollution, pathogenic bioaerosols, and lower respiratory infection

Airborne particulate matter (PM) pollution, as a leading environmental health risk, causes millions of premature deaths globally every year. Lower respiratory infection (LRI) is a sensitive response to short-term exposure to outdoor PM pollution. The airborne transmission of etiological agents of LRI, as an important pathway for infection and morbidity, bridges the public health issues of air quality and pathogen infectivity, virulence, resistance, and others. Enormous efforts are underway to identify common pathogens and substances that are etiological agents for LRI and to understand the underlying toxicological and clinical basis of health effects by identifying mechanistic pathways. Seasonal variations and geographical disparities in the survival and infectivity of LRI pathogens are unsolved mysteries. Weather conditions in geographical areas may have a key effect, but also potentially connect LRI with short-term increases in ambient air PM pollution. Statistical associations show that short-term elevations in fine and coarse PM lead to increases in respiratory infections, but the causative agents could be chemical or microbiological and be present individually or in mixtures, and the interactions between chemical and microbiological agents remain undefined. Further investigations on high-resolution monitoring of airborne pathogens in relation to PM pollution for an integrated exposure-response assessment and mechanistic study are warranted. Improving our understanding of the spatiotemporal features of pathogenic bioaerosols and air pollutants and translating scientific evidence into effective policies is vital to reducing the health risks and devastating death toll from PM pollution.

Occurrence, spatial patterns, air-seawater exchange, and atmospheric deposition of polycyclic aromatic hydrocarbons (PAHs) from the Northwest Pacific to Arctic Ocean

Numerous studies have elucidated the characteristics of polycyclic aromatic hydrocarbons (PAHs) in the Arctic; however, their behavior in different environments has not been studied at a large scale. To investigate the occurrence, spatial trends, air-seawater exchange and atmospheric deposition of 16 polycyclic aromatic hydrocarbons (PAHs), this study takes sample from the Northwest Pacific Ocean. to the Arctic Ocean.The concentrations of 16 PAHs in air and seawater ranged from 27 to 5658 pg/m³ and 34-338 ng/L, respectively. The air-seawater exchange flux of the region was calculated with a Whitman two-film model to be -82681-24613 ng/m²/day. Meanwhile, low-ring PAHs were transported from seawater to the air, while high-ring PAHs were transported from air to seawater. A correlation analysis between multiple environmental factors and particle phase ratio suggested that temperature might be the major driving factor for PAHs in the long-range atmospheric transport (LRAT) process. Moreover, the dry atmospheric deposition fluxes in the region were analyzed by considering environmental factors and the physicochemical properties of each PAHs monomer, these fluxes ranged from 0.001 to 696 ng/m²/day and were greater inshore than offshore and at higher latitudes. This study highlights that PAHs are affected by LRAT during their transport from Asia to Northwest Pacific and further to the Arctic Ocean, while emphasizing that air-seawater exchange plays an important role in air-sea interactions in the open ocean.

Dissolved PAHs impacted by air-sea interactions: Net volatilization and strong surface current transport in the Eastern Indian Ocean

In the Indian Ocean, the marine fate of polycyclic aromatic hydrocarbons (PAHs) is impacted by the unique air-sea interactions with great monsoon characters. By collecting water-column samples during the monsoon transition period, we found PAHs (∑₈PAH: 1.1-27 ng L^-1) showed significantly different distributions from the Bay of Bengal, Equatorial Indian Ocean, Eastern Indian Ocean, and the South China Sea (p < 0.001). Their vertical profiles showed natural logarithm relationships with depth in the Bay of Bengal and Equatorial Indian Ocean. PAHs were mainly from wood/coal combustion and vehicle emission. The estimation of PAHs' air-seawater exchange flux revealed net volatilizations from seawater except in the Eastern Indian Ocean. The Wyrtki Jet, a surface current driven by the westerly wind, was observed in the equatorial area. This swift current could transport PAHs eastward efficiently with a mass flux of 636 ± 188 g s^-1. The subsurface current, Equatorial Undercurrent, played a less crucial role in PAHs' lateral transport with a flux of 115 ± 31.3 g s^-1. This study preliminarily revealed the role of air-sea interactions on PAHs' transport and fate in the open ocean. The coupled air-sea interactions with biogeochemical processes should be considered in future work.

Polycyclic Aromatic Hydrocarbons in the Marine Atmosphere from the Western Pacific to the Southern Ocean: Spatial Variability, Gas/Particle Partitioning, and Source Apportionment

The spatial variability of polycyclic aromatic hydrocarbons (PAHs) in the marine atmosphere contributes to the understanding of the global sources, fate, and impact of this contaminant. Few studies conducted to measure PAHs in the oceanic atmosphere have covered a large scale, especially in the Southern Ocean. In this study, high-volume air samples were taken along a cross-section from China to Antarctica and analyzed for gaseous and particulate PAHs. The data revealed the spatial distribution, gas-particle partitioning, and source contributions of PAHs in the Pacific, Indian, and Southern Oceans. The median concentration (gaseous + particulate) of ∑₂₄PAHs was 3900 pg/m³ in the Pacific Ocean, 2000 pg/m³ in the Indian Ocean, and 1200 pg/m³ in the Southern Ocean. A clear latitudinal gradient was observed for airborne PAHs from the western Pacific to the Southern Ocean. Back trajectories (BTs) analysis showed that air masses predominantly originated from populated land had significantly higher concentrations of PAHs than those from the oceans or Antarctic continents/islands. The air mass origins and temperature have significant influences on the gas-particle partitioning of PAHs. Source analysis by positive matrix factorization (PMF) showed that the highest contribution to PAHs was from coal combustion emissions (52%), followed by engine combustion emissions (27%) and wood combustion emissions (21%). A higher contribution of PAHs from wood combustion was found in the eastern coastal region of Australia. In contrast, engine combustion emissions primarily influenced the sites in Southeast Asia.

The impact of national energy structure on the concentrations, environmental behavior, and sources of polycyclic aromatic hydrocarbons in riverine and coastal sediments of the Beibu Gulf, China

In this study, polycyclic aromatic hydrocarbons (PAHs) were measured in sediments of the Beibu Gulf in 2017 to investigate sources and a risk assessment. The results showed the total PAH concentration (∑₁₆PAHs) in sediments of the Beibu Gulf in 2017 (17.6 ± 16.7 ng g^-1) was significantly lower than that in 2010 (47.8 ± 27.4 ng g^-1). The ∑₁₆PAHs concentrations varied spatially within the Beibu Gulf, impacted by point source pollution. The results of adsorption/desorption and water-air partitioning suggest that the environmental behavior of PAHs in the Beibu Gulf is affected by atmospheric deposition and sediment-water partitioning. A risk assessment showed that the PAHs in sediments were within a safety threshold. Three source apportionment methods show that oil spills and oil and biomass burning were the most important (>83.8%) sources of PAHs in sediments of the Beibu Gulf.

Distribution, fate and sources of polycyclic aromatic hydrocarbons (PAHs) in atmosphere and surface water of multiple coral reef regions from the South China Sea: A case study in spring-summer

Our previous study revealed PAHs' wide occurrence in corals from multiple coral reef regions (CRRs) in the South China Sea. However, little is known about their occurrence, distribution, fate, and sources in the ambient environment of these CRRs. This study aimed to resolve these research gaps. The results showed ∑₁₅PAHs (total concentrations of 15 US EPA priority controlled PAHs exclude naphthalene) in the atmosphere (gas-phase: 0.31-49.6 ng m^-3; particle-phase: 2.6-649 pg m^-3) were mainly influenced by air mass origins. Southwesterly wind caused higher ∑₁₅PAHs than the southeasterly wind. The ∑₁₅PAHs in seawater from the nearshore (462 ± 244 ng L^-1) was higher than that from offshore Zhongsha Islands (80.5 ± 72.1 ng L^-1) because of the effect of terrigenous pollution and ocean current. Source apportionment indicated that the mixed sources of spilled oil and combustion from neighboring countries were the main contributors to PAHs in these CRRs. The total deposition fluxes showed that PAHs tended to migrate from the atmosphere to seawater. Global warming may inhibit this process, but PAHs still have a migration pattern of atmosphere-ocean-corals, which will further increase the environmental pressure on coral reef ecology.

Distribution and gas-particle partitioning of polycyclic aromatic hydrocarbons over the East China Sea and Yellow Sea in spring: Role of atmospheric transport transition

To elucidate the variations in the East Asian monsoon system during seasonal changes and their impacts on continental outflow of polycyclic aromatic hydrocarbons (PAHs), sixteen integrated air samples were collected during a research cruise covering the Yellow Sea (YS) and East China Sea (ECS) in mid-spring of 2017. The concentrations of total suspended particle (TSP), aerosol-phase PAH fractions, ratios of organic to elemental carbon (OC/EC) and gas-particle partitioning of atmospheric PAHs exhibited clear regional differences associated with variations in the monsoon regime. The total concentrations of 16 USEPA priority PAHs (Σ₁₆PAHs) varied from 3.11 to 13.4 ng/m³ throughout the cruise, with medium-to-high molecular weight (MW) PAHs more enriched over the YS and north ECS than the south ECS. Together with the relatively low gaseous PAH fraction over the YS and north ECS (78 ± 4%) relative to the south ECS (95 ± 13%), this result indicates the pattern of regional atmospheric transport. The ratio of organic to elemental carbon varied significantly between the south ECS (lower than 4) and the YS and north ECS (greater than 4), indicating contributions from vehicle emissions and coal combustion or biomass burning, respectively, following different atmospheric input pathways of carbonaceous aerosols, as supported by backward trajectory analysis. Considering the gas-particle partitioning of PAHs, soot adsorption was the main partitioning mechanism in the study region; while high-MW PAHs in the YS and north ECS were influenced by both absorption and adsorption. The K_oa absorption model provided better predictions for high-MW PAHs when continental air masses prevailed, despite underestimating the partition coefficients (k_p) of low-MW PAHs. Meanwhile, predicted k_p for medium MW PAHs was better estimated over the YS and ECS when K_sa was included.

Source Apportionment and Toxic Potency of Polycyclic Aromatic Hydrocarbons (PAHs) in the Air of Harbin, a Cold City in Northern China

A total of 68 PUF samples were collected seasonally from 17 sampling sites in Harbin, China from May 2016 to April 2017 for analyzing 15 congeners of gaseous polycyclic aromatic hydrocarbons (Σ15PAHs). An improved non-negative matrix (NMF) model and a positive matrix factorization (PMF) model were used to apportion the sources of PAHs. The carcinogenic risk due to exposure to PAHs was estimated by the toxicity equivalent of BaP (BaPeq). The results showed that the average concentration of Σ15PAHs was 68.3 ± 22.3 ng/m3, and the proportions of 3-ring, 4-ring, 5-ring, and 6-ring PAHs were 64.4%, 32.6%, 2.10%, and 0.89%, respectively. Among the six typical functional areas in Harbin, the Σ15PAHs concentrations were 98.1 ± 76.7 ng/m3, 91.2 ± 76.2 ng/m3, 71.4 ± 75.6 ng/m3, 67.9 ± 65.6 ng/m3, 42.6 ± 34.7 ng/m3, and 38.5 ± 38.0 ng/m3 in the wastewater treatment plant, industrial zone, business district, residential area, school, and suburb, respectively. During the sampling period, the highest concentration of Σ15PAHs was in winter. The improved NMF model and PMF model apportioned the PAHs into three sources including coal combustion, biomass burning, and vehicle exhaust. The contributions of coal combustion, biomass burning, and vehicle exhausts were 34.6 ± 3.22%, 48.6 ± 4.03%, and 16.8 ± 5.06%, respectively. Biomass burning was the largest contributor of Σ15PAHs concentrations in winter and coal combustion contributed significantly to the concentrations in summer. The average ΣBaPeq concentration was 0.54 ± 0.23 ng/m3 during the sampling period, high concentrations occurred in the cold season and low levels presented in the warm period. Vehicle exhaust was the largest contributor to the ΣBaPeq concentration of PAHs in Harbin.

Volatilization of polycyclic aromatic hydrocarbons (PAHs) over the North Pacific and adjacent Arctic Ocean: The impact of offshore oil drilling

Air and seawater samples were collected in 2016 over the North Pacific Ocean (NPO) and adjacent Arctic Ocean (AO), and Polycyclic Aromatic Hydrocarbons (PAHs) were quantified in them. Atmospheric concentrations of ∑₁₅ PAHs (gas + particle phase) were 0.44-7.0 ng m^-3 (mean = 2.3 ng m^-3), and concentrations of aqueous ∑₁₅ PAHs (dissolved phase) were 0.82-3.7 ng L^-1 (mean = 1.9 ng L^-1). Decreasing latitudinal trends were observed for atmospheric and aqueous PAHs. Results of diagnostic ratios suggested that gaseous and aqueous PAHs were most likely to be related to the pyrogenic and petrogenic sources, respectively. Three sources, volatilization, coal and fuel oil combustion, and biomass burning, were determined by the PMF model for gaseous PAHs, with percent contributions of 10%, 44%, and 46%, respectively. The 4- ring PAHs underwent net deposition during the cruise, while some 3- ring PAHs were strongly dominated by net volatilization, even in the high latitude Arctic region. Offshore oil/gas production activities might result in the sustained input of low molecular weight 3- ring PAHs to the survey region, and further lead to the volatilization of them. Compared to the gaseous exchange fluxes, fluxes of atmospheric dry deposition and gaseous degradation were negligible. According to the extrapolated results, the gaseous exchange of semivolatile aromatic-like compounds (SALCs) may have a significant influence on the carbon cycling in the low latitude oceans, but not for the high latitude oceans.

Polycyclic aromatic hydrocarbons (PAHs) in corals of the South China Sea: Occurrence, distribution, bioaccumulation, and considerable role of coral mucus

Coral reefs have suffered degradation from climate change and water quality deterioration. Studies have shown that PAHs are present widely in some coastal seawater and coral tissues. However, no studies have focused on the PAHs in coastal coral mucus and offshore coral tissues. Targeting the South China Sea, this study for the first time investigated the occurrence, tissue-mucus partitioning, and bioaccumulation of PAHs in coastal and offshore corals. The tissue and mucus of the corals were processed separately. The results indicated that the total concentration of 15 of the 16 PAHs that are prioritized by U.S. EPA (excluding naphthalene) (∑₁₅PAHs) was significantly higher in the coastal tissues (173 ± 314 ng g^-1 dw) than in the offshore tissues (71 ± 109 ng g^-1 dw), as well as in coastal seawater (196 ± 96 ng L^-1) than in the offshore water (54 ± 9 ng L^-1). ∑₁₅PAHs is two orders of magnitude higher in the mucus (3200 ± 6470 ng g^-1 dw) than in the tissues (128 ± 43 ng g^-1 dw). By average, 29% of ∑₁₅PAHs were accumulated in the mucus. The results suggest that mucus plays an important role in the bioaccumulation of PAHs by corals from ambient seawater.

Organic molecular markers in marine aerosols over the Western Mediterranean Sea

A scientific campaign was undertaken along the Western sector of the Mediterranean Sea in the summer 2015 (26th Jun to 13th Jul), with the goal of gathering information about organic contaminants affecting marine aerosol over the Italian seas and with a special focus on changes in composition due to sources. 24 PM₁₀ atmospheric samples in total were chemically characterized, including polycyclic aromatic hydrocarbons (PAHs), aliphatic hydrocarbons (n-alkanes) and phthalate esters. Contemporarily, regulated gaseous toxicants (i.e. ozone, nitrogen oxides and sulfur dioxide) and meteorological parameters were recorded. Samplings were carried out inshore in front of harbors (N = 7) and along the cruise, both during the vessel shipping (N = 11, transects) and at its stops offshore (N = 6). Total PAH concentrations ranged from 0.03 to 1.94 ng/m³ and raised close to harbors and coastal sites, confirming that continental sources were responsible for the strong increase of pollution levels there compared to offshore. The percent composition and diagnostic ratio rates of PAHs were different for harbors, while transects were in agreement with offshore stops, possibly due to the different impact of pollution sources. n-Alkanes (C₂₁C₃₈) and the corresponding carbon preference index rates (CPI) were assessed; their values ranged 8.7-90 ng/m³ and 1.1-2.9 respectively, which suggested that fossil fuel combustion was the dominant source, though biogenic emission could contribute. Alkyl phthalates revealed wide variability in concentrations among aerosol samples. Moreover, long-range atmospheric transport and particle ageing effect induced by photo-oxidants were important factors controlling the composition of organic aerosols in the Mediterranean Sea air.

Assessing on toxic potency of PM2.5-bound polycyclic aromatic hydrocarbons at a national atmospheric background site in North China

A total of 76PM_2.5 samples collected at Tuoji Island from November 2011 to January 2013 were used to analyze 15 congeners of polycyclic aromatic hydrocarbons (∑₁₅PAHs) and assess their toxic potency. The average ∑₁₅PAHs was 15.34±8.87ngm^-3, ranging from 4.24 to 40.62ngm^-3 over the sampling period. BkF, BbF, Phe and BaP were dominant PAH congeners, contributing together 60.64% of the ∑₁₅PAH concentration. The highest monthly ∑₁₅PAHs concentration was in January 2012, followed by the next January, which was closely four times greater than the lowest level occurred in July 2012. Wheat straw burning was responsible for the high PAH concentrations in June 2012. The averaged BaP toxicity equivalent (TEQ-BaP) concentration was 2.70±1.88ngm^-3 over the sampling period. BaP and DaA were the largest contributors, which contributed 58.5% and 14.7% of totals, respectively. The high TEQ-BaP and TEQ-BaP value per unit of ∑₁₅PAHs concentration (TEQ-BaP(U)) values occurred in the cold season and the low levels presented in the warm period. The heaviest monthly TEQ-BaP was 5.28±2.84ngm^-3, which appeared in January 2012; the lowest value was 0.86±0.33ngm^-3, which occurred in July 2012. The potential source contribution function (PSCF) showed the occurrence of the high health risk associated with PAHs in the middle of Liaoning and the south of Shandong Peninsula.

Air-sea exchange and gas-particle partitioning of polycyclic aromatic hydrocarbons over the northwestern Pacific Ocean: Role of East Asian continental outflow

We measured 15 parent polycyclic aromatic hydrocarbons (PAHs) in atmosphere and water during a research cruise from the East China Sea (ECS) to the northwestern Pacific Ocean (NWP) in the spring of 2015 to investigate the occurrence, air-sea gas exchange, and gas-particle partitioning of PAHs with a particular focus on the influence of East Asian continental outflow. The gaseous PAH composition and identification of sources were consistent with PAHs from the upwind area, indicating that the gaseous PAHs (three-to five-ring PAHs) were influenced by upwind land pollution. In addition, air-sea exchange fluxes of gaseous PAHs were estimated to be -54.2-107.4 ng m^-2 d^-1, and was indicative of variations of land-based PAH inputs. The logarithmic gas-particle partition coefficient (logK_p) of PAHs regressed linearly against the logarithmic subcooled liquid vapor pressure (logP_L⁰), with a slope of -0.25. This was significantly larger than the theoretical value (-1), implying disequilibrium between the gaseous and particulate PAHs over the NWP. The non-equilibrium of PAH gas-particle partitioning was shielded from the volatilization of three-ring gaseous PAHs from seawater and lower soot concentrations in particular when the oceanic air masses prevailed. Modeling PAH absorption into organic matter and adsorption onto soot carbon revealed that the status of PAH gas-particle partitioning deviated more from the modeling K_p for oceanic air masses than those for continental air masses, which coincided with higher volatilization of three-ring PAHs and confirmed the influence of air-sea exchange. Meanwhile, significant linear regressions between logK_p and logK_oa (logK_sa) for PAHs were observed for continental air masses, suggesting the dominant effect of East Asian continental outflow on atmospheric PAHs over the NWP during the sampling campaign.

Sources and mass inventory of sedimentary polycyclic aromatic hydrocarbons in the Gulf of Thailand: Implications for pathways and energy structure in SE Asia

Surface sediments obtained from a matrix of 92 sample sites in the Gulf of Thailand (GOT) were analyzed for a comprehensive study of the distribution, sources, and mass inventory of polycyclic aromatic hydrocarbons (PAHs) to assess their input pathways and impacts of the regional land-based energy structure on the deposition of PAHs on the adjacent continental margins. The concentration of 16 PAHs in the GOT ranged from 2.6 to 78.1ng/g (dry weight), and the mean concentration was 19.4±15.1ng/g. The spatial distribution pattern of 16 PAH was generally consistent with that of sediment grain size, suggesting the influence of regional hydrodynamic conditions. Correlation and principal component analysis of the PAHs indicated that direct land-based inputs were dominantly responsible for the occurrence of PAHs in the upper GOT and the low molecular weight (LMW) PAHs in the coastal region could be from petrogenic sources. A positive matrix factorization (PMF) model apportioned five contributors: petroleum residues (~44%), biomass burning (~13%), vehicular emissions (~11%), coal combustion (~6%), and air-water exchange (~25%). Gas absorption may be a significant external input pathway for the volatile PAHs in the open GOT, which further implies that atmospheric loading could be important for the sink of PAHs in the open sea of the Southeast Asia (SE Asia). The different PAH source patterns obtained and a significant disparity of PAH mass inventory in the sediments along the East and Southeast Asia continental margins can be ascribed mainly to different land-based PAH emission features under the varied regional energy structure in addition to the depositional environment and climatic conditions.

Particulate PAHs and n-alkanes in the air over Southern and Eastern Mediterranean Sea

Particulate polycyclic aromatic hydrocarbons, n-alkanes and polar organic compounds were investigated in the marine atmosphere of Southern and Eastern Mediterranean Sea, in the frame of the scientific cruise of Urania ship between 27 July and 11 August 2013. The PM10 fraction of aerosol to which most organic substances are associated, were collected daily; contemporarily, gaseous regulated toxicants (ozone, nitrogen oxides and carbon oxide) and carbonyls were recorded. Samplings were carried out in front of Palermo and Messina, respectively the start and end harbors, and along the cruise, both in movement (transects, N = 14) and at stops (N = 11). Total PAHs ranged from 0.06 ng/m(3) up to 1.8 ng/m(3), with the maximums observed close to harbors. Unlike total concentrations that were in general comparable, the percent composition of PAHs was distinct for harbors, transects and stops, which allowed to draw insights about the pollution sources impact. Concentrations of n-alkanes (C18-C35) ranging from 6.7 to 43 ng/m(3) were quantified. The carbonyls evaluation revealed relatively high concentrations of formaldehyde (∼4-24 μg/m(3)) and acetone (∼5-35 μg/m(3)) near harbors, and of acrolein (up to 12 μg/m(3)) offshore, while benzaldehyde was quite independent of the site type (≈0.5 μg/m(3)). Nicotine and caffeine were detected, at different extents (0.0-2.2 ng/m(3) and 0.01-0.17 ng/m(3), respectively), in ca. 70% and 100% of samples. Alkyl phthalates ranged from 2.7 to 67 ng/m(3) and showed variable percentages in the samples. Finally, traces of N,N-diethyl-meta-toluene amide (up to 0.4 ng/m(3)) were found at all sites.