Sink For Polycyclic Aromatic Hydrocarbons Research Articles

Risk Assessments of Polycyclic Aromatic Hydrocarbons in the Surface Sediments of Drinking Water Sources in Ifite Ogwari, South-East Nigeria

ABSTRACT Surface water is the main source of drinking water in Ifite Ogwari, Anambra State, South-East Nigeria. In aquatic environments, sediment functions as both a source and a sink of polycyclic aromatic hydrocarbons (PAHs). To determine the level of pollution, health concerns to people and the environment, and potential sources of PAHs in the surface water sediments in Ifite Ogwari, sediment samples were collected from 9 surface water sources used for drinking by Ifite Ogwari people and were analyzed using a Gas Chromatography/Flame Ionization Detector (GC-FID). In all sediment samples, only 11 PAHs out of 16 United States Environmental Protection Agency (USEPA) priority PAHs were detected while 5 were below detectable limits. The concentration of benzo[a]anthracene was high but detected in only 2 sediment samples while fluoranthene has a relatively close concentration across all samples. Benzo[k]fluoranthene has the highest concentration compared to other PAHs in the samples while benzo[a]pyrene has the lowest concentration across all samples. Atammele sediment was analyzed as the most carcinogenic followed by Isiachala with concentrations of 84.23 ng/µL and 51.92 ng/µL respectively. Ube stream sediment has the lowest concentration of PAHs (11.74 ng/µL). Ecological risk of the PAHs revealed a sediment-to-sediment variation in the risk profile. Human health risk assessment depicts that hazard index and total cancer risk for adults and children ranged from 2.3E-07 - 2.57E-05 and 4.85E-07 - 5.43E-05 respectively. Pyrogenic activities are the main source of PAHs in the sediments. The results provide a guide for monitoring PAHs pollution and protecting drinking water sources.

The occurrence characteristics, removal efficiency, and risk assessment of polycyclic aromatic hydrocarbons in sewage sludges from across China

Sewage sludge is considered to be an important sink for polycyclic aromatic hydrocarbons (PAHs) in wastewater treatment plants and the potential risks from sludge contaminated with PAHs during land application has attracted attention. To identify the priority PAHs for control and enhance their removal from sludge, the occurrence characteristics, removal efficiency, and risk assessment of PAHs in sewage sludges from across China were analyzed. Data collection was from 2001 to 2023. Results showed that 16 PAHs were widely detected in Chinese sewage sludge with total amounts (∑16PAHs) between 0.06 and 34.93 mg kg dw−1. Fossil fuel, coal, and biomass combustion are main anthropogenic sources of PAHs in China. In general, phenanthrene (PHE), anthracene (ANT), fluorescein (FL), chrysene (CHR), pyrene (PYR), and benzo[b]fluoranthene (BbF) are regarded as the main components and PAHs with 3–5 rings dominate (84.01%–91.53%) sewage sludge in China. Although aerobic composting and anaerobic treatment significantly improve ∑16PAHs removal, sludge stabilization treatment only reduced the risk by a small amount, especially for high-molecular-weight (HMW) PAHs. The benzo[a]anthracene (BaA), benzo[a]pyrene (BaP), and dibenzo[a,h]anthracene (DahA) are proposed as the priority control contaminants for sewage sludge in China because they have consistently high-risk quotient (RQ) values of 2.42–7.47, 1.28–3.16, 1.06–1.83 before and after sludge stabilization, respectively. More attention should be paid to BaA, BbF, benzo[k]fluoranthene (BkF), BaP, DahA, and indeno[1,2,3-cd]pyrene (IcdP) in Beijing; ANT, BaA, and BaP in Shanghai; and BaA and BaP in Guanghzou. Although the toxic equivalent quotient (TEQ) for PAHs met the limit concentration requirements of the national standard, the potential health risks due to long-term exposure to HMW PAHs cannot be ignored because the incremental lifetime cancer risk (ILCR) was consistently in the risk threshold range (>1 × 10−6). Some suggestions on enhanced treatment approaches and land use standards are proposed to further alleviate the risk from HMW PAHs.

Metatranscriptomic responses and microbial degradation of background polycyclic aromatic hydrocarbons in the coastal Mediterranean and Antarctica

Although microbial degradation is a key sink of polycyclic aromatic hydrocarbons (PAH) in surface seawaters, there is a dearth of field-based evidences of regional divergences in biodegradation and the effects of PAHs on site-specific microbial communities. We compared the magnitude of PAH degradation and its impacts in short-term incubations of coastal Mediterranean and the Maritime Antarctica microbiomes with environmentally relevant concentrations of PAHs. Mediterranean bacteria readily degraded the less hydrophobic PAHs, with rates averaging 4.72 ± 0.5 ng L h−1. Metatranscriptomic responses showed significant enrichments of genes associated to horizontal gene transfer, stress response, and PAH degradation, mainly harbored by Alphaproteobacteria. Community composition changed and increased relative abundances of Bacteroidota and Flavobacteriales. In Antarctic waters, there was no degradation of PAH, and minimal metatranscriptome responses were observed. These results provide evidence for factors such as geographic region, community composition, and pre-exposure history to predict PAH biodegradation in seawater.

Sediment core records and impact factors of polycyclic aromatic hydrocarbons in Chinese lakes

Lake sediment is a natural sink for polycyclic aromatic hydrocarbons (PAHs). PAH sedimentation characteristics and their impact factors of Chinese lakes have mainly been qualitative assessed. However, quantitative impacts of PAH sedimentation from different factors have not been well analyzed. To fill this gap, we screened PAH sedimentation records from the literature, for 51 lakes in China and other regions of the world, to identify historical concentration variation and the impact factors of PAHs in different regions, in lake sediment. The results show that PAH concentrations in the sediment core in the selected Chinese lakes (478 ± 812 ng/g dry weight (dw)) were significantly lower than those in North America (5518 ± 6572 ng/g dw) and Europe (3817 ± 4033 ng/g dw). From 1900 to 2015, most of the lakes in China showed an increasing trend of PAH sedimentation concentrations, with the lakes in Southeastern China showed a decreasing trend of PAH concentration in the period of 2001–2015, which was later than the peak times shown in Western countries (1941–1970). The 2-3-ring PAHs were the main components in the sediment core of Chinese lakes, but the proportion to the total PAHs decreased from 72% in 1900–1940 to 55% in 2001–2015. Generalized additive modeling (GAM) was adopted to simulate the associations between PAH sedimentation records and the impact factors. There are large regional variations of economic and industrial development in China. The impact factors of PAH accumulation in the lake sediments differ in different regions. However, population and the consumption of coal, pesticides, and fertilizer were identified to be the most important impact factors influencing PAH sedimentation. The Chinese government needs to strengthen control measures on pollutant discharge to reduce the anthropogenic impact of PAH sedimentation in lakes.

The characteristics of polycyclic aromatic hydrocarbons and heavy metals in water and sediment of dajiuhu subalpine wetland, shennongjia, central China, 2018–2020: Insights for sources, sediment-water exchange, and ecological risk

Polycyclic aromatic hydrocarbons (PAHs) and heavy metals (HMs) are persistent environmental issues. Secondary emissions are produced as a result of climate change and human activity. To observe spatio-temporal variations of PAHs and HMs and to discuss the sources as well as the source or sink of PAHs for sediment and peat, twelve surface sediment and surface water sites were chosen along the direction of the flow to down hole in the Dajiuhu area, simultaneously, surface peat and water samples were collected in peatland. Samples were continuously taken for three years (Sep. 2018, Sep. 2019, and Sep. 2020, respectively). The results showed that PAHs and HMs are common in sediment and peat. PAHs concentration is generally higher in peat and water, while HMs concentration is relatively higher in water and relatively low in sediment and peat, and the ecological risk of sediment was low. HMs in sediment are mainly affected by rock weathering, while PAHs are mainly affected by atmospheric deposition, biomass and coal combustion and vehicle emission. HMs and PAHs can be used as an indicator of rock weathering and human activity in Dajiuhu area, respectively. A water-sediment fugacity analysis revealed that peat is a sink for PAHs, confirming that it has a high capacity for adsorbing organic contaminants, and that sediments are secondary sources of PAHs that can release them into water. Attention should be paid to the increased fugacity fraction (ff) value in peatland, indicating that peat might be converted from a sink to a source of PAHs.

Spatial and seasonal variations of PAHs in soil, air, and atmospheric bulk deposition along the plain to mountain transect in Hubei province, central China: Air-soil exchange and long-range atmospheric transport

Polycyclic aromatic hydrocarbons (PAHs) are a long-term environmental problem faced by human society. The sources of involuntary PAHs are complex, moreover, secondary emissions of fixed PAHs in the environment occur due to global change and disturbance of human activities. Samples of three environmental media including soil, air, and atmospheric bulk deposition were collected to observe the spatial distribution and seasonal variation, to discuss the source or sink of PAHs and their association with the air mass transport along the plain (Jianghan Plain, JHP) to mountain transect, and explore the geographic scope of the atmospheric transport influence. The results obtained showed that 16 individual PAHs generally existed in all environmental multimedia being studied, and the PAHs concentration in air, soil and deposition flux of atmospheric bulk was higher in JPH than in “Western Hubei Mountains” (WHMs). Considerably high PAHs concentrations were obtained from the soil, air and atmospheric bulk deposition in winter, summer, and both summer and winter, respectively. The air-soil fugacity fraction of PAHs indicated that the soil of Dajiuhu (DJH) is likely to be a sink. Backward air trajectory simulation confirmed that most of the air mass passes over the JHP before reaching DJH, combined with the (transport and persistence level III) TaPL3 model results JHP are acting as sources. However, seasonal changes lead to a shift in the roles of soil sources and sinks. The TaPL3 model calculated that PAHs are transported through water for a wider range of effects and a longer persistence, even up to 10 years.

Sources and sinks evaluation of PAHs in leaves of Cinnamomum camphora in megacity: From the perspective of land-use types

Direct and indirect effects of complex urban land-use types on polycyclic aromatic hydrocarbons (PAHs), including their total amount, composition, sources and sinks, were evaluated from 84 sampling points in the megacity of Shanghai. We measured the content and composition of PAHs adsorbed by the leaves of Cinnamomum camphora and established buffers of different radii at each point. The different land-use types areas were counted therewith to investigate their effects on the sources and sinks of PAHs in leaves. Results showed that the average value of PAHs in the leaves was 3014.06 ± 1879.713 ng g−1. The substance profiles were dominated by medium-molecular-weight (MMW, 54%) and high-molecular-weight (HMW, 45%) PAHs, and these fractions were much higher than that of low-molecular-weight (LMW, 1%) PAHs. Through correlation analysis, the land-use type of industry, road, business, and residential areas were initially assessed as the sources of PAHs, whereas water, farmland, and woodland areas were sinks. Lasso regression proved that road and residential areas have proven to be the main source of PAHs in Shanghai, rather than industry and business areas. Woodland was found to be a better sink for PAHs than water and farmland. Sources and sinks of PAHs with different benzene rings also differed greatly: the main sources of MMW PAHs were industrial emissions and commercial activities, with the main sinks being water and woodland; the primary sources of HMW PAHs were traffic emissions and residential activities, with the main sink being farmland. This study assessed the sources and sinks of PAHs in cities, from the perspective of varied effects of different urban land-use types on PAH composition and spatial distribution, and bridged the gap between urban PAHs alleviation and the land-use planning in megacity, with instructive significance for planning policy development.

Controlling factors for the distribution of typical organic pollutants in the surface sediment of a macrotidal bay.

Marine sediment is the final sink of polycyclic aromatic hydrocarbons (PAHs) from river input and atmospheric deposition. Such kind of pollutant cycles in the marine environment is usually controlled by hydrodynamic conditions. Many previous studies have explored how ocean currents influence pollutant distribution, but very few studies have focused on the relationships between the distribution patterns of pollutant and residual currents or sediment transport. In this study, 16 monomers of PAHs from 135 surface sediment samples collected in the Hangzhou Bay, a typical macrotidal bay, were systematically identified and their sources were analyzed. The sediment characteristics and distribution pattern were also comprehensively analyzed. The results showed the seabed sediments were moderately polluted by PAHs with a level of 38.58-1371.06ng/g (median 186.70ng/g). Most of the PAHs are composed of three to five rings, originated from combustion of coal and firewood. The combustion of oil also contributes to PAHs in seabed sediments for some areas. The PAHs are found to be concentrated within the estuary and the offshore areas, as well in coastal ocean. Fine-grained sediment transport is controlled by residual currents, which leads to PAH accumulation in the bay and the offshore areas, forming a high-value distribution pattern. Hence, we conclude that residual current is the main factors that control the long-term distribution of PAHs in the seabed sediments of the macrotidal bay. Temporal and spatial varying models of PAHs were needed in a further study to explore further the mechanisms how PAHs are transported in coastal areas.

Sources, influencing factors and environmental indications of PAH pollution in urban soil columns of Shanghai, China

The urban environment is an essential source and sink of polycyclic aromatic hydrocarbons (PAHs). However, there is a paucity of knowledge regarding the pollution state of PAHs and their controlling factors in urban soil columns. We therefore quantified PAHs, black carbon (BC), and total organic carbon (TOC) in 24 1-m-deep urban soil columns collected from nearby areas of power plants (P), industrial parks (I) and environmental companies (E) from Shanghai Metropolitan Area, China. The results showed that the total concentrations of USEPA 16 PAHs varied from 91.5 to 46834.5ngg−1, and the average pollution level followed the pattern P>I>E. The vertical migration of PAHs obeyed the exponential decay model in undisturbed soil columns. However, anthropogenic factors (land use and artificial disturbance) and edaphic conditions (BC and TOC contents as well as particle size) were strong influencing factors for the PAHs’ fate in urban soils. Coal combustion and vehicle sources were identified as dominant PAH sources. Risks based on both the total benzo[a]pyrene equivalent (BaPeq) values and the incremental lifetime cancer risk (ILCR) values showed a general trend as P>I>E. For most sites, the ecological risks were below the threshold safe value of 600ng BaPeq g−1, and ILCR values were at the negligible risk level in I and E. However, dermal contact to soils, especially the deep soil layers in P, have potential health risks and should draw enough attention. Our findings thus supplemented knowledge regarding the vertical distribution and migration of PAHs, showed the predictive power of BC and TOC for PAH fate, and revealed the importance of monitoring and managing urban soils in deeper layers not just surface layers.

Fate of polycyclic aromatic hydrocarbons from the North Pacific to the Arctic: Field measurements and fugacity model simulation

Polycyclic aromatic hydrocarbons (PAHs) have accumulated ubiquitously inArctic environments, where re-volatilization of certain organic pollutants as a result of climate change has been observed. To investigate the fate of semivolatile organic compounds in the Arctic, dissolved PAHs in the surface seawaters from the temperate Pacific Ocean to the Arctic Ocean, as well as a water column in the Arctic Ocean, were collected during the 4th Chinese National Arctic Research Expedition in summer 2010. The total concentrations of seven dissolved PAHs in surface water ranged from 1.0 to 5.1 ng L−1, decreasing with increasing latitude. The vertical profile of PAHs in the Arctic Ocean was generally characteristic of surface enrichment and depth depletion, which emphasized the role of vertical water stratification and particle settling processes. A level III fugacity model was developed in the Bering Sea under steady state assumption. Model results quantitatively simulated the transfer processes and fate of PAHs in the air and water compartments, and highlighted a summer air-to-sea flux of PAHs in the Bering Sea, which meant that the ocean served as a sink for PAHs, at least in summer. Acenaphthylene and acenaphthene reached equilibrium in air-water diffusive exchange, and any perturbation, such as a rise in temperature, might lead to disequilibrium and remobilize these compounds from their Arctic reservoirs.

Urban stormwater inputs to an adapted coastal wetland: Role in water treatment and impacts on wetland biota

The Lake Pertobe wetland system is a semi-natural wetland that has been modified primarily for recreational use. However, this lake system receives stormwater from much of the central business district of Warrnambool City (Victoria, Australia) and serves as a buffer zone between the stormwater system and the Merri River and Merri Marine Sanctuary. This work considers the impact of stormwater inputs on Lake Pertobe and the effectiveness of the lake in protecting the associated marine sanctuary. Sediment contaminants (including heavy metals and polycyclic aromatic hydrocarbons (PAHs)) and water quality parameters within the lake, groundwater and stormwater system were measured. Water quality parameters were highly variable between stormwater drains and rain events. Suspended solids rapidly settled along open drains and shortly after entering the lake. Groundwater inputs increased both salinity and dissolved nitrogen in some stormwater drains. Some evidence of bioaccumulation of metals in the food chain was identified and sediment concentrations of several PAHs were very high. The lake acted as a sink for PAHs and some metals and reductions in Escherichia coli, biological oxygen demand and total phosphorus were observed, affording some protection to the associated marine sanctuary. Nutrient retention was inadequate overall and it was identified that managing the lake primarily as a recreational facility impacted on the effectiveness of stormwater treatment in the system.

Polystyrene Plastic: A Source and Sink for Polycyclic Aromatic Hydrocarbons in the Marine Environment

Polycyclic aromatic hydrocarbons (PAHs) on virgin polystyrene (PS) and PS marine debris led us to examine PS as a source and sink for PAHs in the marine environment. At two locations in San Diego Bay, we measured sorption of PAHs to PS pellets, sampling at 0, 1, 3, 6, 9, and 12 months. We detected 25 PAHs using a new analytical method with comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry. Several congeners were detected on samples before deployment. After deployment, some concentrations decreased (1,3-dimethylnaphthalene and 2,6-methylnaphthalene), while most increased [2-methylanthracene and all parent PAHs (PPAHs), except fluorene and fluoranthene], suggesting that PS debris is a source and sink for PAHs. When sorbed concentrations of PPAHs on PS are compared to the five most common polymers [polyethylene terephthalate (PET), high-density polyethylene (HDPE), polyvinyl chloride (PVC), low-density polyethylene (LDPE), and polypropylene (PP)], PS sorbed greater concentrations than PP, PET, and PVC, similar to HDPE and LDPE. Most strikingly, at 0 months, PPAHs on PS ranged from 8 to 200 times greater than on PET, HDPE, PVC, LDPE, and PP. The combination of greater PAHs in virgin pellets and large sorption suggests that PS may pose a greater risk of exposure to PAHs upon ingestion.

Exchange of polycyclic aromatic hydrocarbons among the atmosphere, water, and sediment in coastal embayments of southern California, USA

The present study investigated cross-media transport between both the sediment and the water column and between the water column and the atmosphere, to understand the role of each compartment as a source or a sink of polycyclic aromatic hydrocarbons (PAH) in southern California, USA, coastal waters. Concentrations of PAH were measured in the atmosphere, water column, and sediment at four water-quality-impaired sites in southern California: Ballona Creek Estuary, Los Angeles Harbor, Upper Newport Bay, and San Diego Bay. These concentrations were used to calculate site-specific sediment-water and atmosphere-water exchange fluxes. The net sediment-water exchange of total PAH (t-PAH) was positive, indicating that sediments were a source to the overlying water column. Furthermore, the net atmosphere-water exchange (gas exchange + dry particle deposition) of t-PAH was typically positive also, indicating the water column was a net source of PAH to the surrounding atmosphere through gas exchange. However, in all cases, the magnitude of the diffusive flux of PAH out of the sediments and into the water column far exceeded input or output of PAH through air/water exchange processes. These results demonstrate the potential importance of contaminated sediments as a source of PAH to the water column in coastal waters of southern California.

Contribution of unburned lubricating oil and diesel fuel to particulate emission from passenger cars

In this study we determined particle-bound paraffins in the exhaust of six light-duty diesel vehicles on a chassis dynamometer for different driving cycles and ambient temperatures. The filters containing particulate matter were extracted with dichloromethane in a Soxhlet apparatus, and the paraffin analysis was performed using two-dimensional normal phase high-pressure liquid chromatography (HPLC) coupled on-line to gas chromatography-flame ionization detection (GC–FID). The different molecular mass of lubricant and diesel paraffins facilitated the distinction between diesel and lubricant contribution to the emission. Although all vehicles were certified according to the same emission class, there were considerable variations between vehicles. The study showed that under cold-start conditions the organic mass fraction ranged from 10% to 30% with respect to particle mass and the paraffins from 30% to 60% with respect to the organic mass. With cold engine, falling ambient temperature increased the emission of unburned diesel fuel, whereas that from unburned lubricating oil was less affected. Under warm-start conditions, the ambient temperature had less impact on the emission of paraffins. The emissions were also affected by the operating conditions of the engine: driving cycles with higher mean load tend towards higher emissions of lubricant. The operating conditions also affected the distribution of paraffins: the emission of light paraffins seemed to be lower with higher load in the driving cycle. With an urban and a highway cycle, roughly 40% and 80% w/w, respectively, of unburned paraffins were contributed by the lubricant. Measurements of polycyclic aromatic hydrocarbons (PAH) in lubricating oil showed lubricant to be a sink for PAHs. As lubricant significantly contributes to the organic emission, as shown in this study, it can be assumed that it is also a significant source of PAH emissions.

Towards a complete mass balance and model for PCBs and PAHs in a small rural lake, Cumbria U.K.

This paper summarizes the processes of exchange/fluxes for polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) in a small well‐studied rural lake, Esthwaite Water in northwest England. Measurements of PCB and PAH concentrations have been made in rain, air, water, dated sediment cores, and sediment trap samples over a 2‐yr study period and used to determine fluxes to and from the lake. A steady state mass balance model was used to construct an input‐output budget for the chemicals and to investigate the relative importance of transport into and out of the lake. The hydraulic transport from the lake was the most important loss mechanism for both PCBs and PAHs. Volatilization, not sedimentation, is currently the dominant loss process for PCBs in the water column, whereas, sedimentation exceeds volatilization for PAHs. The data further suggest that the current sediment‐water flux is upward for PCBs and downwards for PAHs, indicating that the sediments might be acting as a secondary source for PCBs but continue to act as a sink for PAHs. Riverine, catchment runoff, or both are believed to be the most important input for PCBs and PAHs to the lake although direct aerial deposition to the lake is also important for PCBs. Differences in the mixtures of compounds in the various compartments suggests significant fractionation of PCBs and PAHs in the air‐water‐sediment system in the lake.