Historical record of effects of human activities on absolute and relative concentrations of Polycyclic aromatic hydrocarbons (PAHs) in Lake Chao, China

Seasonal variation and concentration of PAHs in Lake Balaton sediment: A study on molecular weight distribution and sources of pollution

The temporal and spatial variations of 16 Polycyclic Aromatic Hydrocarbons (PAHs) were examined at multiple sites around Lake Balaton from February 2023 to January 2024. The results indicated that the concentrations of PAHs in sediment were high during the winter months, 448.35 to 619.77 ng/g dry weight, and low during the summer months, 257.21 to 465.49 ng/g dry weight. The concentration of high molecular weight PAHs (HMWPAHs), consisting of 5-6 rings, was greater than that of low molecular weight PAHs (LMWPAHs), which had 2-3 rings. The total incremental lifetime cancer risk (ILCR) for both dermal and ingestion pathways was high for both adults and children during the four seasons, with the highest records as the following: winter > spring > summer > autumn. The ecological effects of the 16 PAHs were negligible except for acenaphthylene (Acy) and fluorene (Fl), which displayed slightly higher concentrations during the autumn and spring, respectively.

Characterization, Behavior, and Risk Assessment of Polycyclic Aromatic Hydrocarbons (PAHs) in the Estuary Sediments

Polycyclic aromatic hydrocarbons (PAHs) are persistent toxic substances that have ubiquitous presence in water, air, soil, and sediment environments. The growth of PAH toxicities and related ecotoxicology risk in estuary sediment has a serious concern. Present study examined the PAHs concentration, sources, and ecological risk from selected sites in Subarnarekha River estuary (SRE) sediment deposits. The sum of toxic 16 PAHs was ranged from 36.8 to 670.8 ng/g (mean = 223.46 ± 196.35 ng/g). The total PAH concentration varied significantly among the sampling sites (range 511.3 ng/g to 233.8 ng/g) based on allochthonous contaminant loads. Among the 16 compounds, Phen had the highest concentration (40.18 ng/g), followed by Pye (31.86 ng/g), Flur (29.36 ng/g), and NA (19.33 ng/g). Most of the sampling sites contained abundant 3-ring and 4-5-ring PAHs. Based on diagnostic ratios and PCA analysis petroleum combustion, biomass, and coal-burning have been identified as the major sources. The PAHs had high mutagenic equivalent factor and toxic equivalent factor values posing great ecological threats and health risks.

Size distribution of particulate polycyclic aromatic hydrocarbons in fresh combustion smoke and ambient air: A review

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous in the atmosphere and they mostly stem from the imperfect combustion of fossil fuels and biofuels. PAHs are inherently associated with homogenous fine particles or distributed to different-sized particles during the aging of air masses. PAHs carried by fine particles undergo a long-range transport to remote areas while those adsorbed on coarse particles have a shorter lifetime in ambient air. More importantly, PAHs with higher molecular weights tend to be bound with finer particles and can deeply enter the lungs, posing severe health risks to humans. Thus, the environmental fate and health effects of particulate PAHs are strongly size-dependent. This review summarizes the size distributions of particulate PAHs freshly emitted from combustion sources as well as the distribution patterns of PAHs in ambient particles. It was found that PAHs from stationary sources are primarily bound to fine particles, which are slightly larger than particles to which PAHs from mobile sources are bound. In ambient air, particulate PAHs are distributed in larger size modes than those in the combustion fume, and the particle size decreases with PAH molecular weight increasing. The relevant mechanisms and influencing factors of particle size distribution changes are illustrated in this article, which are essentially attributed to combustion and ambient temperature as well as the physical and chemical properties of PAHs. Overall, the study on the particle size distribution of PAHs will contribute for a full understanding of the origin, atmospheric behaviors and health effects of particulate PAHs.

Polycyclic aromatic hydrocarbons (PAHs) in water and sediment of Hoor Al-Azim wetland, Iran: a focus on source apportionment, environmental risk assessment, and sediment-water partitioning

The concentration, source, and ecological risk of 16 polycyclic aromatic hydrocarbons (PAHs) in water and sediment samples in Hoor Al-Azim wetland, a significant freshwater wetland in Lower Mesopotamia, were evaluated. Total PAHs concentrations varied from 15.3 to 160.15 ng/L, and 15.78 to 410.2 μg/Kg in water and sediment, respectively. PAHs pollution levels in sediments compared with sediment quality guidelines (SQG) were found to be moderate in two stations and low in water and the rest of sediment stations. Based on the diagnostic ratio analysis, cluster analysis (CA), and principal component analysis-multiple linear regression (PCA-MLR), the mean percentage contributions were 62.62% for mixed pyrogenic and petrogenic sources (e.g., unburned and combusted fossil fuels from fishing boats and vehicle engines, incomplete combustion, oil leakage), 20.68% for auto emission, and 16.7% for pyrogenic sources (fossil fuels and biomass combustion). According to the sediment risk assessment indices such as mean effects range-median quotient (M-ERM-Q), the ecological risk of multiple PAHs was low. Risk quotient (RQ) calculation of water samples suggested high ecological risk level for Benzo[a]anthracene (BaA), and low to moderate for other individual PAHs and ΣPAHs. The result of PAHs partitioning between sediment and water phases revealed that most PAHs prefer to accumulate in sediment. Sediments probably act as a secondary source for some PAHs in the oil collection and pumping station.

A review on occurrence and risk of polycyclic aromatic hydrocarbons (PAHs) in lakes of China

Polycyclic aromatic hydrocarbons (PAHs) residues have attracted attention worldwide. This study summarizes the current levels of PAH exposure in the water environments of lakes. In addition, the risk levels from individual PAHs and ΣPAHs in the water environments of lakes in China were evaluated by incremental lifetime cancer risk (ILCR) assessment, the toxic equivalent concentration (TEQ_BaP), the risk quotient (RQ), the effects range-low (ERL) and the effects range-median (ERM). The results showed that the concentrations of ∑PAHs in water and sediment ranged from 4.0 to 12,970.8 ng L^-1 and 6.52 to 7935.21 ng g^-1, respectively, and the highest concentrations of individual PAHs were of naphthalene (Nap) (6525 ng L^-1), followed by indeno(1,2,3‑cd)pyrene (IcdP) (3452.6 ng g^-1). Concentrations in the Great Lakes region in China showed spatial difference, with the Qinghai-Tibet Plateau Lakes District and Mongolia-Xinjiang Lakes District being less polluted. However, the pollution level of PAHs in lakes is relatively high at the global scale. The ecological risk assessment found a moderate level of ∑PAHs in water, but benz(a)anthracene (BaA) and phenanthrene (Phe) had high RQ values, which might pose a significant risk to aquatic organisms in lakes. Although the contents of ∑PAHs in sediments are low, most individual PAHs pose potential risks, especially acenaphthene (Ace), fluorene (Flu) and dibenz(a,h)anthracene (DahA). This study revealed the pollution levels of PAHs across China and provided a scientific basis for PAH pollution control and environmental protection.

Anthropogenic PAHs in lake sediments: a literature review (2002-2018)

Lake sediments are an important reservoir for toxic and hydrophobic polycyclic aromatic hydrocarbons (PAHs). Monitoring of PAHs in sediment is helpful to understand pollution mechanisms and anthropogenic activities. This study reviews studies of PAHs in lake sediments published during 2002-2018. The studies' findings are analyzed, distributions of PAHs in lake sediments are summarized, and the applicability of lake sediments for tracking changes in PAH emission sources is emphasized. Lake sediments heavily polluted with PAHs are distributed in China, Egypt, the USA, and some urban lakes in Africa. The high levels of PAHs are predominantly associated with human activities such as anthropogenic combustion, petroleum industries, road traffic, and socioeconomic factors. However, the concentrations of sedimentary PAHs in most lakes were below the international guideline values.

Integrated ecological and chemical food web accumulation modeling explains PAH temporal trends during regime shifts in a shallow lake

Shallow lakes can switch suddenly from a turbid situation with high concentrations of phytoplankton and other suspended solids to a vegetated state with clear water, and vice versa. These alternative stable states may have a substantial impact on the fate of hydrophobic organic compounds (HOCs). Models that are fit to simulate impacts from these complex interactions are scarce. We developed a contaminant fate model which is linked to an ecosystem model (PCLake) for shallow lakes. This integrated model was successful in simulating long-term dynamics (1953-2012) of representative polycyclic aromatic hydrocarbons (PAHs) in the main biotic and abiotic components in a large shallow lake (Chaohu in China), which has undergone regime shifts in this period. Historical records from sediment cores were used to evaluate the model. The model revealed that regime shifts in shallow lakes had a strong impact on the fate of less hydrophobic compounds due to the large storage capacity of macrophytes, which accumulated up to 55.6% of phenanthrene in the clear state. The abrupt disappearance of macrophytes after the regime shift resulted in a sudden change in phenanthrene distribution, as the sediment became the major sink. For more hydrophobic compounds such as benzo(a)pyrene, the modeled impact of the regime shift was negligible for the whole environment, yet large for biotic compartments. This study is the first to provide a full mechanistic analysis of the impact of regime shifts on the fate of PAHs in a real lake ecosystem.