Levels and toxicity of polycyclic aromatic hydrocarbons in marine sediments

Genetic redundancy in the naphthalene-degradation pathway of Cycloclasticus pugetii strain PS-1 enables response to varying substrate concentrations

Polycyclic aromatic hydrocarbon (PAH) contamination in marine environments range from low-diffusive inputs to high loads. The influence of PAH concentration on the expression of functional genes [e.g. those encoding ring-hydroxylating dioxygenases (RHDs)] has been overlooked in PAH biodegradation studies. However, understanding marker-gene expression under different PAH loads can help to monitor and predict bioremediation efficiency. Here, we followed the expression (via RNA sequencing) of Cycloclasticus pugetii strain PS-1 in cell suspension experiments under different naphthalene (100 and 30 mg L-1) concentrations. We identified genes encoding previously uncharacterized RHD subunits, termed rhdPS1α and rhdPS1β, that were highly transcribed in response to naphthalene-degradation activity. Additionally, we identified six RHD subunit-encoding genes that responded to naphthalene exposure. By contrast, four RHD subunit genes were PAH-independently expressed and three other RHD subunit genes responded to naphthalene starvation. Cycloclasticus spp. could, therefore, use genetic redundancy in key PAH-degradation genes to react to varying PAH loads. This genetic redundancy may restrict the monitoring of environmental hydrocarbon-degradation activity using single-gene expression. For Cycloclasticus pugetii strain PS-1, however, the newly identified rhdPS1α and rhdPS1β genes might be potential target genes to monitor its environmental naphthalene-degradation activity.

Multimedia distribution, dynamics, and seasonal variation of PAHs in Songhua wetland: Implications for ice-influenced conditions

The knowledge of polycyclic aromatic hydrocarbons (PAHs) in wetlands remains limited. There is a research need for the dynamics between interfaces of multimedia when ice is present in this fragile ecosystem. In this study, sediment, open-water, sub-ice water, and ice samples were collected from the Songhua wetland to study the behaviors of PAHs with and without influences from ice. The concentration of all individual PAHs in sub-ice water (370-1100 ng/L) were higher than the open-water collected from non-ice-covered seasons (50-250 ng/L). Enrichment of PAHs in the ice of wetland was found, particularly for high-molecular-weight PAHs (HMW). This could be attributed to the relatively lower polarity of hydrocarbons compounds, making them more likely to remain in the ice layer during freezing. Source assessments reveal common sources for sub-ice water and ice, which differ from those in the open water in non-ice-covered seasons. This difference is primarily attributed to heating activities in the Harbin during winter. The average percentage contributions were 79% for sub-ice water and 36% for ice related to vehicle exhausts and coal combustion. Additionally, wood burning contributed 25% to sub-ice water and 62% to ice. Sediment in the wetland was found to serve as a final deposit particularly for heavier PAHs, especially those with 6 rings. Sediment also has the potential to act as a source for the secondary emission of low-molecular-weight PAHs (LMW) congeners into the water. PAHs in wetland displayed low ecological risk, while HMW PAHs with relative higher ecological risk is recommended to be further monitored.

Finding microbial composition and biological processes as predictive signature to access the ongoing status of mangrove preservation

Mangroves are complex land-sea transition ecosystems whose microbiota are essential for their nutrient recycling and conservation. Brazil is the third-largest estuarine area in the world and "Baía de Todos os Santos" (BTS) is one of the largest bays of the country, with wide anthropogenic exploration. Using a metagenomic approach, we investigated composition and functional adaptability as signatures of the microbiome of pristine and anthropized areas of BTS, including those under petroleum refinery influence. The taxonomic analysis showed dominance of sulfate-reducing Desulfobacteraceae, Rhodobacteraceae, and Flavobacteriaceae. Taxa were significantly diverse between pristine and disturbed areas. Disturbed mangroves showed a notary increase in abundance of halophilic, sulfur-related, and hydrocarbon-degrading genera and a decrease in diatoms compared to pristine area. The metabolic profile of BTS mangroves was correlated with the differentially abundant microbiota. Two ecological scenarios were observed: one marked by functions of central metabolism associated with biomass degradation and another by mechanisms of microbial adaptability to pollution conditions and environmental degradation. Part of the microbiome was distinct and not abundant in Brazilian estuarine soils. The microbiome signature observed in each BTS mangrove reflects how human actions impact the diversity of these ecosystems and also emphasize their role in attempting to restore disturbed mangroves. The microbiome may act as a potential biological indicator of the preservation status of these soils, despite the limitation of soil property conditions. Additionally, our data pointed to metagenomics as an additional tool for environmental assessment and reinforced the need for protective measures for the mangroves under study.

Substrate-independent expression of key functional genes in Cycloclasticus pugetii strain PS-1 limits their use as markers for PAH biodegradation

Microbial degradation of petroleum hydrocarbons is a crucial process for the clean-up of oil-contaminated environments. Cycloclasticus spp. are well-known polycyclic aromatic hydrocarbon (PAH) degraders that possess PAH-degradation marker genes including rhd3α, rhd2α, and pahE. However, it remains unknown if the expression of these genes can serve as an indicator for active PAH degradation. Here, we determined transcript-to-gene (TtG) ratios with (reverse transcription) qPCR in cultures of Cycloclasticus pugetii strain PS-1 grown with naphthalene, phenanthrene, a mixture of these PAHs, or alternate substrates (i.e., no PAHs). Mean TtG ratios of 1.99 × 10^-2, 1.80 × 10^-3, and 3.20 × 10^-3 for rhd3α, rhd2α, and pahE, respectively, were measured in the presence or absence of PAHs. The TtG values suggested that marker-gene expression is independent of PAH degradation. Measurement of TtG ratios in Arctic seawater microcosms amended with water-accommodated crude oil fractions, and incubated under in situ temperature conditions (i.e., 1.5°C), only detected Cycloclasticus spp. rhd2α genes and transcripts (mean TtG ratio of 4.15 × 10^-1). The other marker genes-rhd3α and pahE-were not detected, suggesting that not all Cycloclasticus spp. carry these genes and a broader yet-to-be-identified repertoire of PAH-degradation genes exists. The results indicate that the expression of PAH marker genes may not correlate with PAH-degradation activity, and transcription data should be interpreted cautiously.

Application of sulfur-coated magnetic carbon nanotubes for extraction of some polycyclic aromatic hydrocarbons from water resources

In the present work, novel sulfur-coated magnetic carbon nanotubes (MCNTs-S) material was fabricated by S coating on the MCNTs using a simple heating procedure. TGA, EDX, XRD, TEM, and VSM were employed to characterize the as-prepared composite. Using HPLC-UV system, the produced superparamagnetic sorbent was employed for the extraction and measurement of trace levels of five polycyclic aromatic hydrocarbons (PAHs) in environmental waters. The synergistic effect of the sulfur layer and CNTs substrate is primarily responsible for the remarkable extraction efficiency of the MCNTs-S sorbent towards PAHs. The experimental factors including MCNTs-S dosage, sorption time, elution solvent, ionic strength and solution pH were explored and optimized. Considering that the ionic strength and pH do not have any impact on the PAHs extraction, as a result, there is no need the unnecessary adjustment of the water samples. The linear dynamic ranges and detection limits under optimal conditions were in the range of 0.05-0.11 ng mL^-1 and 0.2-150 ng mL^-1, respectively. The analysis of PAHs in the real samples (sea water and river water) using this approach was successfully assessed with appropriate recovery values (94.6%-99.0%).

Occurrence, distribution, sources, and bioaccumulation of polycyclic aromatic hydrocarbons (PAHs) in multi environmental media in estuaries and the coast of the Beibu Gulf, China: a health risk assessment through seafood consumption

The coastal zone is a crucial transitional area between land and ocean, which is facing enormous pressure due to global climate change and anthropogenic activities. It is essential to pay close attention to the pollution caused by polycyclic aromatic hydrocarbons (PAHs) in the coastal environment and their effect on human health. The pollution status of PAHs was investigated in the Beibu Gulf, taking into consideration various environmental media. The results showed that the total concentration of 16 PAHs (Σ₁₆PAHs) was significantly higher in winter than in summer. Compared to the coastal area, the status of PAHs in the estuarine areas was found to be more severe in summer, while the regional difference was insignificant in winter. In summer, the Σ₁₆PAHs in estuarine waters (71.4 ± 9.58 ng/L) > coastal waters (50.4 ± 9.65 ng/L); estuarine sediment (146 ± 116 ng/g) > coastal zone (76.9 ± 108 ng/g). The source apportionment indicated that spilled oil, biomass, and coal burning were the primary sources of PAHs in the water. The predominant sources of pollution in the sediments were spilled oil, fossil fuel burning, and vehicle emissions. With regard to the status of PAHs in marine organisms in the coastal area of the Beibu Gulf, the highest average concentration of PAHs was indicated in shellfishes (183 ± 165 ng/g), followed by fishes (73.7 ± 57.2 ng/g), shrimps (42.7 ± 19.2 ng/g), and crabs (42.7 ± 19.2 ng/g) in Beibu Gulf coastal area. The calculated bioaccumulation factor indicates a low bioaccumulation capacity of PAHs in various seafood considering the ambient environment. The human health risk assessment considering multiple age groups indicates minimal health risk on accidental ingestion of PAHs through seafood. However, it is suggested that the intake of shellfish in children be controlled.

PAHs and PCBs Affect Functionally Intercorrelated Genes in the Sea Urchin Paracentrotus lividus Embryos

Polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) represent the most common pollutants in the marine sediments. Previous investigations demonstrated short-term sublethal effects of sediments polluted with both contaminants on the sea urchin Paracentrotus lividus after 2 months of exposure in mesocosms. In particular, morphological malformations observed in P. lividus embryos deriving from adults exposed to PAHs and PCBs were explained at molecular levels by de novo transcriptome assembly and real-time qPCR, leading to the identification of several differentially expressed genes involved in key physiological processes. Here, we extensively explored the genes involved in the response of the sea urchin P. lividus to PAHs and PCBs. Firstly, 25 new genes were identified and interactomic analysis revealed that they were functionally connected among them and to several genes previously defined as molecular targets of response to the two pollutants under analysis. The expression levels of these 25 genes were followed by Real Time qPCR, showing that almost all genes analyzed were affected by PAHs and PCBs. These findings represent an important further step in defining the impacts of slight concentrations of such contaminants on sea urchins and, more in general, on marine biota, increasing our knowledge of molecular targets involved in responses to environmental stressors.

Sediment contamination and toxicity of Marine Protected Areas in southeastern Brazilian coast: A baseline for management planning

Recent studies have shown that the effectiveness of establishing Marine Protected Areas (MPAs) is threatened by toxic effects of contaminants. São Paulo is the most economically developed state of Brazil, and its coast is protected by a system of MPAs, including the North Shore Marine Protected Area (NSMPA). The present study provides a first assessment of sediment quality in NSMPA and two reference sites. Concentrations of arsenic (As), metals (Al, Fe, Cd, Cr, Cu, Ni, Pb, and Zn) and polycyclic aromatic hydrocarbons (PAHs) and its sources were determined. Comparisons with sediment quality guidelines indicated low contamination, as confirmed by the Geoaccumulation Index, which classified the results as background levels. Whole-sediment exposures of the amphipod Tiburonella viscana were performed to estimate possible acute effects, but samples exhibited no toxicity. The results presented in this study represent a baseline for further monitoring programs of MPAs, supporting conservation actions of management plans.

Effects of pyrene and benzo[a]pyrene on the reproduction and newborn morphology and behavior of the freshwater planarian Girardia tigrina

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous pollutants of aquatic ecosystems. Because they are persistent, there is great potential for chronic toxicity to aquatic species, and the evaluation of reproductive effects is fundamental. In this context, planarians are interesting experimental animals, since they can be sensitive to environmental pollutants, and a wide range of reproductive-related endpoints can be assessed. In this work we evaluated fecundity (number of cocoons), fertility (number of newborns), newborn anomalies, adult weight, regenerative abilities and PAH-residues in tissues of the freshwater planarian Girardia tigrina, exposed to either pyrene or benzo[a]pyrene (B[a]P). Pyrene reduced planarian fecundity and fertility at 18.75 μg L^-1 and 75.00 μg L^-1, while B[a]P reduced planarian fecundity at the 37.50 μg L^-1 treatment, which was accompanied by a 33.7% reduction in fertility. Cocoons were kept in clean media and newborns were evaluated for behavioral and morphological anomalies. Many of the newborns resulting from the B[a]P experiment revealed behavioral anomalies, such as spasms and uncoordinated movements. These behavioral anomalies were observed in 12.9% and 38.2% of newborns resulting from the exposure of adult planarians to 9.38 μg L^-1 and 37.50 μg L^-1 of B[a]P, respectively. This study is the first report on the effects of PAHs in freshwater planarians' sexual reproduction and a decreased reproductive output was evidenced. Moreover, the exposure of adults to B[a]P lead to defects in newborns, raising concern on the possible long-term consequences of these compounds for natural planarian populations.

The legacy of industrial pollution in estuarine sediments: spatial and temporal variability implications for ecosystem stress

The direct impacts of anthropogenic pollution are widely known public and environmental health concerns, and details on the indirect impact of these are starting to emerge, for example affecting the environmental microbiome. Anthropogenic activities throughout history with associated pollution burdens are notable contributors. Focusing on the historically heavily industrialised River Clyde, Scotland, we investigate spatial and temporal contributions to stressful/hostile environments using a geochemical framework, e.g. pH, EC, total organic carbon and potentially toxic elements: As, Co, Cr, Cu, Ni, Pb and Zn and enrichment indicators. With regular breaches of the sediment quality standards in the estuarine system we focused on PTE correlations instead. Multivariate statistical analysis (principle component analysis) identifies two dominant components, PC1: As, Cr, Cu, Pb and Zn, as well as PC2: Ni, Co and total organic carbon. Our assessment confirms hot spots in the Clyde Estuary indicative of localised inputs. In addition, there are sites with high variability indicative of excessive mixing. We demonstrate that industrialised areas are dynamic environmental sites dependant on historical anthropogenic activity with short-scale variation. This work supports the development of 'contamination' mapping to enable an assessment of the impact of historical anthropogenic pollution, identifying specific 'stressors' that can impact the microbiome, neglecting in estuarine recovery dynamics and potentially supporting the emergence of antimicrobial resistance in the environment.

Marine sediment toxicity: A focus on micro- and mesocosms towards remediation

Micro- and/or mesocosms are experimental tools bringing ecologically relevant components of the natural environment under controlled conditions closest to the real world, without losing the advantage of reliable reference conditions and replications, providing a link between laboratory studies and filed studies in natural environments. Here, for the first time, a formal comparison of different types of mesocosm applied to the study of marine contaminants is offered, considering that pollution of coastal areas represented a major concern in the last decades because of the abundance of discharged toxic substances. In particular, the structural characteristics of micro- and mesocosms (m-cosms) used to study marine contaminated sediments were reviewed, focusing on their advantages/disadvantages. Their potentiality to investigate sediment remediation have been discussed, offering new perspective on how the use of m-cosms can be useful for the development of practical application in the development of solutions for contaminated sediment management in the contaminated marine environment.

Polyaromatic hydrocarbons in biochars and human health risks of food crops grown in biochar-amended soils: A synthesis study

Soil amendment with biochars is currently being studied worldwide as a sustainable agricultural practice to improve soil and water quality, increase crop productivity, and augment soil carbon storage. However, the formation of polyaromatic hydrocarbons (PAHs) during biochar production is inevitable. Therefore, it is crucial to assess the risks in food safety and human health of crops grown in biochar-amended soils. This paper performed a synthesis study of PAH concentrations in biochars and estimated the risks of soils amended with biochars, based on refereed articles published between 2012 and 2018. The PAH concentrations in biochars ranged greatly, with the dominant proportion being 2-3 ringed PAHs (40%-71%). Biochar application increased the PAH levels in soils at drastically varying extents (0.02-3574 μg/kg), which led to a broad range of PAH concentrations in food crops grown in biochar-amended soils. A five-step method was then introduced to assess the toxicity of biochar-borne PAHs to human health. The total mean incremental lifetime cancer risk for adults was estimated to range between 2.0 × 10^-6-1.9 × 10^-5 via direct contact with and ingestion (inhalation) of contaminated soils or consumption of tainted crops. These results indicated that biochar amendment in soils might pose potential risks to food safety and human health, but the overall cancer risks through exposure to biochar-borne PAHs in soils and food crops were low. Higher application rates (e.g. ≥20 t/ha) of biochars with high PAH contents can be avoided to minimize human cancer risks. Although biochar application in arable farmlands has many environmental and agronomic benefits, holistic and systematic approaches are required to fully assess the benefits and risks before their large-scale adoption. PAHs in biochar may be reduced by improving the biochar production process and developing a cost-effective post-manufacturing treatment.

Comparative analysis of the Polycyclic Aromatic Hydrocarbon (PAH) content and proximate composition of unripe Musa paradisiaca (plantain) fruit exposed to varying methods of roasting

This comparative study was carried out to ascertain the relative effect of smoking and non-smoking methods of food preparation on the concentration of PAHs in unripe plantain sample. The fruit samples were subjected to different smoking methods such as roasting with firewood, charcoal and charcoal augmented with polythene materials as well as non-smoking method such as frying and oven drying process, and compared with the fresh fruits. Gas chromatography-mass spectroscopy (GC-MS) method was used to determine the concentrations of sixteen priority PAHs content of each sample and the results were subjected to statistical analysis. The percentage compositions of crude fibre in the raw, smoked roasted (charcoal, firewood and augmented charcoal) and non-smoked (oven dried and fried) samples were; 4.4% 3.2%, 3.1%, 3.0%, 3.5% and 4.1% respectively. Percentage composition of protein and carbohydrate of the raw food samples were found to be 3.62% and 34.5% respectively which were higher than the dried food samples. The total PAHs concentration of the fresh plantain sample (control) was (8.0 ± 0.1 mg/L). The Charcoal, firewood and augmented roasted sample had total PAHs concentration of (19.3 ± 0.2 mg/L), (19.6 ± 0.1 mg/L) and (20.1 ± 0.1 mg/L) respectively, whereas the total PAHs concentration in the fried and oven dried samples were (9.8 ± 0.1 mg/L) and (15.3 ± 0.2 mg/L) respectively. From the result, it was observed that the total PAHs concentration of the smoke roasted sample were significantly higher (p < 0.05) than the non-smoke roasted sample which indicates that roasting and grilling over open fire or smoke do increase the level of Polycyclic aromatic hydrocarbons (PAHs) in food. Although the concentration of PAHs in the fried sample was significantly (p < 0.05) lower than the oven dried sample, however, it predisposes one to increased risk of atherosclerosis and related lipidemia due to its increased fat concentration. Hence smoking method of food preparation should be substituted with other non-smoking methods such as oven drying.

Levels and trends of polycyclic aromatic hydrocarbons in the Indo-Pacific humpback dolphins from the Pearl River Estuary (2012-2017)

We investigated the levels and trends of the 16 USEPA priority PAHs in the blubber of 37 Indo-Pacific humpback dolphins sampled during the period 2012-2017 from the Pearl River Estuary (PRE), China. Σ₁₆PAHs concentrations (17.6-6080 ng g^-1 wet weight) were at median level compared to dolphin species worldwide. Humpback dolphins affiliated with the hotspots of PAHs, had significantly higher levels of Σ₁₆PAHs than individuals from the other areas in the PRE. Moreover, dolphins stranded on the coast of Lingdingyang are significantly more contaminated by Σ₁₆PAHs than those in the West-four region of the PRE, which appears to reflect the heterogeneous distribution of PAHs in the environment. A marked decline in blubber Σ₁₆PAHs levels is observed over the studied period, with the control of a range of confounding factors. The trend is strongly and statistically significant (p < 0.0001), indicating that the loading of PAHs are gradually being reduced.

Bio-accumulation of Polycyclic Aromatic Hydrocarbons in the Grey Mangrove (Avicennia marina) along Arabian Gulf, Saudi Coast

The Arabian Gulf is considered as one of the most important sources for the crude oil all over the world. Due to the vast oil exploration and exploitation, huge amounts of organic pollutants infiltrate to the gulf. An important class of organic pollutants is polycyclic aromatic hydrocarbons (PAHs). One of the marine habitats in Arabian Gulf area is the mangrove stands, that are undoubtedly impacted by all anthropogenic factors like oil industries and sewage discharge. In the monitoring framework for mangrove ecosystem along Saudi coasts, nine mangrove stands were examined for the accumulation of PAHs in the Arabian Gulf coast. PAHs were measured using Gas Chromatography-Mass Spectrometry. The mean values detected for total PAHs in mangrove sediments, roots and leaf were 105.39, 680.0 and 282.4 ng/g, respectively. The trend of total PAHs concentrations in all sites showed the descending order: roots > leaf > sediments. Despite the sandy nature and low organic carbon contents of the mangrove sediments, moderate values of PAHs were detected in the major sites. PAH bio-accumulation factors for roots are higher than that in leaf. The diagnostic ratios revealed that the sources of PAHs are mainly pyrogenic, except for Damam and Damam Port that were found to be petrogenic.

Toxicity assessment within the application of in situ contaminated sediment remediation technologies: A review

Polluted sediment represents a great problem for aquantic environments with potential direct acute and chronic effects for the biota and can be tackled with both in situ and ex situ treatments. Once dredging activities are not compulsory, sediment can be kept in place and managed with techniques involving the use of amendment and/or capping. Before their application, the assessment of their potential impact to the target environment cannot ignore the safe-by-design approach. The role of toxicity in in situ sediment remediation was reviewed discussing about how it can be used for the selection of amendments and the monitoring of treatment technologies. Results evidenced that capping technology coupled to activated carbon (AC) is the most frequently applied approach with effects varying according to the rate of contamination in treated sediment, the amount of AC used (% v/v), and target biological models considered. Little data are available for zerovalent iron as well as other minor amending agents such as hematite, natural zeolite, biopolymers and organoclays. Current (eco-)toxicological information for in situ sediment remediation technologies is fragmentary and incomplete or entirely missing, making also the interpretation of existing data quite challenging. In situ sediment remediation represents an interesting potentially effective approach for polluted sediment recovering. As its application in some lab-based and field studies reported to induce negative effects for target organisms, amendments and capping agents must be attentively evaluated for short- and long-term environmental effects, also in the perspective of the remediated site monitoring and maintenance.

Toxicity profile of organic extracts from Magdalena River sediments

The Magdalena River, the main river of Colombia, receives contaminated effluents from different anthropogenic activities along its path. However, the Magdalena River is used as drinking water source for approximately 30 million inhabitants, as well as a major source of fish for human consumption. Only a few studies have been conducted to evaluate the environmental and toxicological quality of the Magdalena River. To evaluate sediment toxicity, wild-type and GFP transgenic Caenorhabditis elegans were exposed to methanolic extracts, and effects on lethality, locomotion, growth, and gene expression were determined based on fluorescence spectroscopy. These biological and biochemical parameters were correlated with measured pollutant concentrations (PAHs and trace elements), identifying patterns of toxicity along the course of the river. Effects on lethality, growth, and locomotion were observed in areas influenced by industrial, gold mining, and petrochemical activities. Changes in gene expression were evident for cyp-34A9, especially in the sampling site located near an oil refinery, and at the seaport, in Barranquilla City. Body bend movements were moderately correlated with Cr and As concentrations. The expression of mtl-1, mtl-2, hsp-6, and hsp-70 were significantly associated with Pb/U, Pb, Sr, and As/Sr/Pb/U, respectively. Interestingly, toxicity of methanolic as well as aqueous extracts were more prone to be dependent on Cd, Zn, and Th. In general, ecological risk assessment showed sediments display low environmental impact in terms of evaluated metals and PAHs. Different types of waste disposal on the Magdalena River, as a result of mining, domestic, agricultural, and industrial activities, incorporate toxic pollutants in sediments, which are capable of generating a toxic response in C. elegans.

Appraisement, source apportionment and health risk of polycyclic aromatic hydrocarbons (PAHs) in vehicle-wash wastewater, Pakistan

Vehicle-wash wastewater (VWW) contains elevated concentrations of different petrochemicals including polycyclic aromatic hydrocarbons (PAHs), a carcinogenic group of organic compounds. This study investigates the discharge of PAHs present in the untreated wastewater of vehicle-wash stations (VWS) located in district Peshawar, Pakistan. The data obtained was being novel with the detection of 16 USEPA PAHs (both individuals and total) and compared with earlier studies and international standards. The ∑16PAHs in wastewater from light vehicle-wash stations (LVWS) and heavy vehicle-wash stations (HVWS) ranged from 245-429μg/l and 957-1582μg/l, respectively. A significant difference (p<0.01) was observed in PAHs discharged from LVWS and HVWS. The projected ∑16PAHs discharge from both HVWS (92% of total generated PAHs) and LVWS (8%) was about 5109.9 g per annum. According to PAH diagnostic ratios, PAHs were both petrogenic (chrysene/benz(a)anthracene, low molecular weight/high molecular weight) and pyrogenic (phenanthrene/anthracene, fluoranthene/pyrene, fluoranthene/fluoranthene+pyrene) in origin. The highest toxic equivalent quotient (TEQ) value was shown by benzo(a)pyrene (21.6μg/l) followed by dibenz(ah)anthracene (9.81μg/l) in wastewater from HVWS. However, in LVWS the case was reversed with highest value (7.54μg/l) for dibenz(ah)anthracene followed by benzo(a)pyrene (3.54μg/l). The lowest TEQ value was indicated for phenanthrene (0.007μg/l) in wastewater of LVWS, while pyrene showed the lowest value (0.007μg/l) in wastewater of HVWS. The results indicated that VWS contribute significant amount of PAHs each year, which is of great concern regarding water quality, ecological and human health risk. This is the first systematic and comprehensive research related with generation of PAHs load per day, week, month and annum from VWS, their source apportionment and health effects in Pakistan.

Spatial variation in polycyclic aromatic hydrocarbon exposure in Barrow's goldeneye (Bucephala islandica) in coastal British Columbia

Barrow's goldeneyes are sea ducks that winter throughout coastal British Columbia (BC). Their diet consists primarily of intertidal blue mussels, which can accumulate PAHs; accordingly, goldeneyes may be susceptible to exposure through contaminated prey. In 2014/15, we examined total PAH concentrations in mussels from undeveloped and developed coastal areas of BC. At those same sites, we used EROD to measure hepatic CYP1A induction in goldeneyes. We found higher mussel PAH concentrations at developed coastal sites. Regionally, goldeneyes from southern BC, which has relatively higher coastal development, had higher EROD activity compared to birds from northern BC. Our results suggest goldeneyes wintering in coastal BC were exposed to PAHs through diet, with higher exposure among birds wintering in coastal areas with greater anthropogenic influence. These results suggest the mussel-goldeneye system is suitable as a natural, multi-trophic-level indicator of contemporary hydrocarbon contamination occurrence and exposure useful for establishing oil spill recovery endpoints.

In situ remediation of contaminated marinesediment: an overview

Sediment tends to accumulate inorganic and persistent hydrophobic organic contaminants representing one of the main sinks and sources of pollution. Generally, contaminated sediment poses medium- and long-term risks to humans and ecosystem health; dredging activities or natural resuspension phenomena (i.e., strongly adverse weather conditions) can remobilize pollution releasing it into the water column. Thus, ex situ traditional remediation activities (i.e., dredging) can be hazardous compared to in situ techniques that try to keep to a minimum sediment mobilization, unless dredging is compulsory to reach a desired bathymetric level. We reviewed in situ physico-chemical (i.e., active mixing and thin capping, solidification/stabilization, chemical oxidation, dechlorination, electrokinetic separation, and sediment flushing) and bio-assisted treatments, including hybrid solutions (i.e., nanocomposite reactive capping, bioreactive capping, microbial electrochemical technologies). We found that significant gaps still remain into the knowledge about the application of in situ contaminated sediment remediation techniques from the technical and the practical viewpoint. Only activated carbon-based technologies are well developed and currently applied with several available case studies. The environmental implication of in situ remediation technologies was only shortly investigated on a long-term basis after its application, so it is not clear how they can really perform.

The relative abundance and seasonal distribution correspond with the sources of polycyclic aromatic hydrocarbons (PAHs) in the surface sediments of Chenab River, Pakistan

Chenab River is one of the most important rivers of Punjab Province (Pakistan) that receives huge input of industrial effluents and municipal sewage from major cities in the Central Punjab, Pakistan. The current study was designed to evaluate the concentration levels and associated ecological risks of USEPA priority polycyclic aromatic hydrocarbons (PAHs) in the surface sediments of Chenab River. Sampling was performed from eight (n = 24) sampling stations of Chenab River and its tributaries. We observed a relatively high abundance of ∑16PAHs during the summer season (i.e. 554 ng g(-1)) versus that in the winter season (i.e. 361 ng g(-1)), with an overall abundance of two-, five- and six-ring PAH congeners. Results also revealed that the nitrate and phosphate contents in the sediments were closely associated with low molecular weight (LMW) and high molecular weight (HMW) PAHs, respectively. Source apportionment results showed that the combustion of fossil fuels appears to be the key source of PAHs in the study area. The risk quotient (RQ) values indicated that seven PAH congeners (i.e. phenanthrene, anthracene, fluoranthene, pyrene, benzo(a)pyrene, chrysene and benzo(a)anthracene) could pose serious threats to the aquatic life of the riverine ecosystem in Pakistan.

Metals and tributyltin sediment contamination along the Southeastern Tyrrhenian Sea coast

Anthropogenic pressures can adversely affect the quality of coastal sediment posing at risk human health and the ecosystem. The Southeastern Tyrrhenian Sea (STS) coast (Italy) is still largely unexplored under this point of view. This study investigated for the first time in the area the seasonal variation and potential impact of selected metals (Cd, Cr, Cu, Ni, and Pb) and tributyltin (TBT) from sediment samples collected along the STS coast (Casalvelino Marina, Casalvelino Bay, Acciaroli Marina and Acciaroli Bay) in the perspective of Water Framework Directive and Marine Strategy Framework Directive. Data were compared to the contamination background levels of Punta Licosa reference site considering elemental enrichment factors (EFs) and single substance- and mixture-based risk characterisation ratios. Further, data were discussed considering the review of Southern Tyrrhenian Sea sediment quality. Results evidenced an increase of contamination levels from March to October showing that marinas are more impacted than bays. Sediment EFs highlighted that contamination levels were always greater than the reference site like risk characterisation ratios, suggesting the presence of potential threats. The sediment quality database generated after literature review revealed a similar situation for the whole Southern Tyrrhenian Sea.

Proteomics studies on stress responses in diatoms

Diatoms are a highly diverse group of eukaryotic phytoplankton that are distributed throughout marine and freshwater environments and are believed to be responsible for approximately 40% of the total marine primary productivity. The ecological success of diatoms suggests that they have developed a range of strategies to cope with various biotic and abiotic stress factors. It is of great interest to understand the adaptive responses of diatoms to different stresses in the marine environment. Proteomic technologies have been applied to the adaptive responses of marine diatoms under different growth conditions in recent years such as nitrogen starvation, iron limitation and phosphorus deficiency. These studies have provided clues to elucidate the sophisticated sensing mechanisms that control their adaptive responses. Although only a very limited number of proteomic studies were conducted in diatoms, the obtained data have led to a better understanding of the biochemical processes that contribute to their ecological success. This review presents the current status of proteomic studies of diatom stress responses and discusses the novel developments and applications for the analysis of protein post-translational modification in diatoms. The potential future application of proteomics could contribute to a better understanding of the physiological mechanisms underlying diatom acclimation to a given stress and the acquisition of an enhanced diatom stress tolerance. Future challenges and research opportunities in the proteomics studies of diatoms are also discussed.

Dynamics of bacterial assemblages and removal of polycyclic aromatic hydrocarbons in oil-contaminated coastal marine sediments subjected to contrasted oxygen regimes

To study the impact of oxygen regimes on the removal of polycylic aromatic hydrocarbons (PAHs) in oil-spill-affected coastal marine sediments, we used a thin-layer incubation method to ensure that the incubated sediment was fully oxic, anoxic, or was influenced by oxic-anoxic switches without sediment stirring. Hydrocarbon content and microbial assemblages were followed during 60 days to determine PAH degradation kinetics and microbial community dynamics according to the oxygenation regimes. The highest PAH removal, with 69 % reduction, was obtained at the end of the experiment under oxic conditions, whereas weaker removals were obtained under oscillating and anoxic conditions (18 and 12 %, respectively). Bacterial community structure during the experiment was determined using a dual 16S rRNA genes/16S rRNA transcripts approach, allowing the characterization of metabolically active bacteria responsible for the functioning of the bacterial community in the contaminated sediment. The shift of the metabolically active bacterial communities showed that the selection of first responders belonged to Pseudomonas spp. and Labrenzia sp. and included an unidentified Deltaproteobacteria-irrespective of the oxygen regime-followed by the selection of late responders adapted to the oxygen regime. A novel unaffiliated phylotype (B38) was highly active during the last stage of the experiment, at which time, the low-molecular-weight (LMW) PAH biodegradation rates were significant for permanent oxic- and oxygen-oscillating conditions, suggesting that this novel phylotype plays an active role during the restoration phase of the studied ecosystem.

Metagenomics reveals the high polycyclic aromatic hydrocarbon-degradation potential of abundant uncultured bacteria from chronically polluted subantarctic and temperate coastal marine environments

AIMS

To investigate the potential to degrade polycyclic aromatic hydrocarbons (PAHs) of yet-to-be-cultured bacterial populations from chronically polluted intertidal sediments.

METHODS AND RESULTS

A gene variant encoding the alpha subunit of the catalytic component of an aromatic-ring-hydroxylating oxygenase (RHO) was abundant in intertidal sediments from chronically polluted subantarctic and temperate coastal environments, and its abundance increased after PAH amendment. Conversely, this marker gene was not detected in sediments from a nonimpacted site, even after a short-term PAH exposure. A metagenomic fragment carrying this gene variant was identified in a fosmid library of subantarctic sediments. This fragment contained five pairs of alpha and beta subunit genes and a lone alpha subunit gene of oxygenases, classified as belonging to three different RHO functional classes. In silico structural analysis suggested that two of these oxygenases contain large substrate-binding pockets, capable of accepting high molecular weight PAHs.

CONCLUSIONS

The identified uncultured micro-organism presents the potential to degrade aromatic hydrocarbons with various chemical structures, and could represent an important member of the PAH-degrading community in these polluted coastal environments.

SIGNIFICANCE AND IMPACT OF THE STUDY

This work provides valuable information for the design of environmental molecular diagnostic tools and for the biotechnological application of RHO enzymes.

Organic pollution in surficial sediments of Tripoli harbour, Lebanon

Tripoli harbour is among the most important ports on the Mediterranean Sea eastern basin. The persistent organic pollutants (POPs) were monitored (28 PCBs, 16 PAHs and 18 Me-PAHs) in 15 stations of Tripoli harbour basins, which are influenced by anthropogenic activities. Total PAHs concentrations ranged from 243 to 2965 μg kg(-1)dw, total Me-PAH concentrations ranged from 54 to 1638 μg kg(-1)dw, while total PCB levels ranged from 18 to 302 μg kg(-1)dw. PCBs profiles were dominated by four and six-chlorinated congeners while the PAHs were dominated by four and five rings. For identifying pollution emission sources of PAHs, different ratios were used. The results show that the pollution origin was predominated by pyrogenic process related to the deposition of coal dust and the combustion of biomass and coal. Based on Sediments Quality Guidelines the biological adverse effects on aquatic ecosystems were expected rarely to occasionally for PAHs and PCBs contamination.

Spatial and temporal distribution and risk assessment of polycyclic aromatic hydrocarbons in surface seawater from the Haikou Bay, China

Spatial and temporal distributions of 14 polycyclic aromatic hydrocarbons (PAHs) were investigated in surface waters of Haikou Bay, China from October 2013 to September 2014. The total PAHs concentrations ranged from 420.2 to 2539.1 ng L(-1) with the average value of 1016.3±455.8 ng L(-1), which were predominated by low molecular weight PAHs (2- and 3-ring PAHs). Moreover, PAHs displayed spatial and temporal variations in the concentration and composition pattern. Source analysis based on isomer ratios indicated that the PAHs mostly originated from petroleum and combustion processes. An eco-toxicological risk assessment showed that the potential risk of individual PAHs had reached moderate to high levels and the total concentrations of PAHs had also reached a relatively high level compared with previous studies. This study offers important information on the pollution levels of 14 PAHs in the surface waters of Haikou Bay and recommends that prevention and control of PAHs pollution should be implemented in the region.

A national reconnaissance for selected organic micropollutants in sediments on French territory

To collect a large data set regarding the occurrence of organic substances in sediment, this study presents the examination of 20 micropollutants, as a national survey. The list of target compounds contains two alkylphenols, three polycyclic aromatic hydrocarbons (PAHs) not commonly included in monitoring programmes, six pesticides or metabolites, five pharmaceutical compounds, two hormones, one UV filter and bisphenol A. The selective and sensitive analytical methods, based on quick, easy, cheap, effective, rugged, and safe (QuEChERS) sample preparation followed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) or gas chromatography-time-of-flight mass spectrometry (GC-ToF-MS), allow the quantification at limits comprised between 0.5 and 23 ng/g, depending on the compound. The paper summarizes the analytical results from 154 sampling points. Of the 20 target compounds, 9 were determined at least once, and the sediments contained a maximum of 7 substances. The most frequently detected were PAHs (frequency, 77 %; max., 1,400 ng/g). The pharmaceutical compounds, hormones and pesticides were rarely detected in the samples; the most frequently detected was carbamazepine (frequency, 6 %; max., 31 ng/g). In some cases, the levels of PAHs and bisphenol A exceed the predicted no-effect concentration (PNEC) values.

Concentration, composition and sources of PAHs in the coastal sediments of the exclusive economic zone (EEZ) of Qatar, Arabian Gulf

Surface sediments were collected from sixteen locations in order to assess levels and sources of polycyclic aromatic hydrocarbons (PAHs) in sediments of Qatar exclusive economic zone (EEZ). Samples were analyzed for 16 parent PAHs, 18 alkyl homologs and for dibenzothiophenes. Total PAHs concentration (∑PAHs) ranged from 2.6 ng g(-1) to 1025 ng g(-1). The highest PAHs concentrations were in sediments in and adjacent to harbors. Alkylated PAHs predominated most of the sampling locations reaching up to 80% in offshore locations. Parent PAHs and parent high molecular weight PAHs dominated location adjacent to industrial activities and urban areas. The origin of PAHs sources to the sediments was elucidated using ternary plot, indices, and molecular ratios of specific compounds such as (Ant/Phe+Ant), (Flt/Flt+Pyr). PAHs inputs to most coastal sites consisted of mixture of petroleum and combustion derived sources. However, inputs to the offshore sediments were mainly of petroleum origin.

Evaluation of the potential bioaccumulation ability of the blood cockle (Anadara granosa L.) for assessment of environmental matrices of mudflats

The spatial distribution of 19 polycyclic aromatic hydrocarbons (tPAHs) was quantified in aquacultures located in intertidal mudflats of the west coast of Peninsular Malaysia in order to investigate bioaccumulation of PAH in blood cockles, Anadara granosa (A. granosa). Fifty-four samples from environmental matrices and A. granosa were collected. The sampling locations were representative of a remote area as well as PAH-polluted areas. The relationship of increased background levels of PAH to anthropogenic PAH sources in the environment and their effects on bioaccumulation levels of A. granosa are investigated in this study. The levels of PAH in the most polluted station were found to be up to ten-fold higher than in remote areas in blood cockle. These high concentrations of PAHs reflected background contamination, which originates from distant airborne and waterborne transportation of contaminated particles. The fraction and source identification of PAHs, based on fate and transport considerations, showed a mix of petrogenic and pyrogenic sources. The relative biota-sediment accumulation factors (RBSAF), relative bioaccumulation factors from filtered water (RBAFw), and from suspended particulate matter (SPM) (RBAFSP) showed higher bioaccumulations of the lower molecular weight of PAHs (LMWs) in all stations, except Kuala Juru, which showed higher bioaccumulation of the higher molecular weight of PAHs (HMWs). Calculations of bioaccumulation factors showed that blood cockle can accumulate PAHs from sediment as well as water samples, based on the physico-chemical characteristics of habitat and behaviour of blood cockles. Correlations among concentrations of PAHs in water, SPM, sediment and A. granosa at the same sites were also found. Identification of PAH levels in different matrices showed that A. granosa can be used as a good biomonitor for LMW of PAHs and tPAHs in mudflats. Considering the toxicity and carcinogenicity of PAHs, the bioaccumulation by blood cockles are a potential hazard for both blood cockles and their consumers.

PAHs in surface sediments from coastal and estuarine areas of the northern Bohai and Yellow Seas, China

Polycyclic aromatic hydrocarbon (PAH) concentrations and their risks in surface sediments (n = 35) collected from coastal and estuarine areas of the northern Bohai and Yellow Seas, China, were investigated in 2008. Total concentrations of PAHs ranged from 52.3 to 1,870.6 ng/g dry weight. The greatest concentrations were observed in the Dou River of Tangshan where waste water from small factories is discharged into the river without treatment. At other locations, municipal sewage was the primary contributor of PAHs. Regional differences in concentrations of PAHs in sediments are related to human activities. Concentrations of PAHs were significantly correlated with concentrations of organic carbon in sediments. The patterns of relative concentrations and types of PAHs observed and knowledge of the potential sources, as well as the results of a principal component analysis, are consistent with the primary sources of PAHs in sediments of the northern Bohai Sea and Yellow Sea, being derived from the high-temperature pyrolytic processes such as combustion of fossil fuel. While concentrations of PAHs at most locations did not exceed the effects range median stated by the numerical effect-based sediment quality guidelines of the United States, concentrations of PAHs at some locations were similar to or greater than the effects range low.

Enhanced dissipation of polycyclic aromatic hydrocarbons in the presence of fresh plant residues and their extracts

The feasibility of using fresh plant residues and their extracts to stimulate the bio-dissipation of polycyclic aromatic hydrocarbons (PAHs) were highlighted. Wood chip, bamboo leave, orange peel and their water-extractable organic matter (WEOM) were chosen as amendment materials. Effect of WEOM on bio-dissipation (bioaccumulation and biodegradation) of phenanthrene and pyrene from water by two bacteria were investigated. Orange peel extract demonstrated the highest efficiency for stimulating PAHs removal by bacterium B1 (Pseudomonas putida), while bamboo leave extract was the best one to enhance PAHs bio-dissipation by bacterium B2 (unidentified bacterium isolated from PAHs-contaminated soil). Amended the actual contaminated soil with 1% plant residues, PAHs dissipation were increased by 15-20%, 20-39%, 14-24%, 12-23% and 17-26%, respectively, for 2-, 3-, 4-, 5- and 6-ring PAHs via stimulating indigenous microbial degradation activity. Bamboo leave exhibited the most effective one to stimulate dissipation of PAHs in contaminated soil.

Abundance, dynamics, and biogeographic distribution of seven polycyclic aromatic hydrocarbon dioxygenase gene variants in coastal sediments of Patagonia

Novel polycyclic aromatic hydrocarbon dioxygenase gene variants were present in abundances similar to or higher than those of phnA1 from Cycloclasticus spp. at a chronically polluted subantarctic coastal marine environment in Patagonia. These novel gene variants were detected over a 6-year time span and were also present in sediments from temperate Patagonian sites.

Proteomic analysis of the marine diatom Thalassiosira pseudonana upon exposure to benzo(a)pyrene

Background

Polycyclic aromatic hydrocarbons (PAHs) are environmental pollutants ubiquitously distributed. They are generated by incomplete combustion of organic materials such as wood or fossil fuels. Due to their carcinogenic, mutagenic effects and to their wide distribution in the environment, these pollutants pose many concerns to researchers and regulators. In our laboratories we investigated the effect of benzo(a)pyrene (BaP) exposure in the marine diatom Thalassiosira pseudonana, which has become an important model organism in aquatic toxicology studies.

Results

In order to investigate the mechanism of action of PAHs, we exposed the diatoms for 24 h to 36.45 μg/L of BaP which inhibits the growth by about 30%, and analysed the relative protein expression profile by a quantitative proteomics approach based on iTRAQ labels. The proteomics profile analysis showed that around 10% of the identified proteins were regulated and one fourth of them confirmed the gene expression changes seen by DNA microarray. Particularly interesting was the down regulation of the Silicon transporter 1 (SIT1), an enzyme that is responsible for the uptake of silicon from the media into the diatom cells. Regulation of SIT1 upon BaP treatment was also confirmed at the gene expression level.

Conclusions

The potential use of the regulated proteins found in this study as early indicators of environmental exposure to PAHs is discussed. In particular, SIT1 is considered a promising biomarker and SIT1 expression changes were confirmed also when the diatoms were exposed to field samples, e.g. marine surface sediments contaminated by PAHs.

Risk assessment for the daily intake of polycyclic aromatic hydrocarbons from the ingestion of cockle (Anadara granosa) and exposure to contaminated water and sediments along the west coast of Peninsular Malaysia

The concentration of carcinogenic polycyclic aromatic hydrocarbons (c-PAHs) present in the sediment and water of Peninsular Malaysia as well as in the cockle Anadara granosa was investigated. Samples were extracted and analysed with gas chromatography-mass spectrometry. The concentrations of total carcinogenic polycyclic aromatic hydrocarbons (t-PAHs) were measured between 0.80 +/- 0.04 to 162.96 +/- 14.74 ng/g wet weight (ww) in sediment, between 21.85 +/- 2.18 to 76.2 +/- 10.82 ng/L in water samples and between 3.34 +/- 0.77 to 46.85 +/- 5.50 ng/g ww in the cockle tissue. The risk assessment of probable human carcinogens in the Group B2 PAHs was calculated and assessed in accordance with the standards of the United States Environmental Protection Agency (US EPA). Case I in the toxicity assessment analysed the cancer risk to consumers of Malaysian blood cockle. Case II assessed the risk of cancer from exposure to PAHs from multiple pathways. The average cancer risk of case I and case II were found to be classifiable as unsafe according to the US EPA standard. The cancer risk due to c-PAHs acquired by the ingestion of blood cockle was (8.82 +/- 0.54) x 10-6 to (2.67 +/- 0.06) x 10(-2), higher than the US EPA risk management criterion. The non-cancer risks associated with multiple pathways in Kuala Gula, Kuala Juru and Kuala Perlis were higher than the U.S. EPA safe level, but the non-cancer risk for eating blood cockle was below the level of U.S. EPA concern.

Emission of polycyclic aromatic hydrocarbons from selected processes in steelworks

The emission of polycyclic aromatic hydrocarbons from selected processes in steelworks in southern Poland was investigated. Size-segregated samples of air particulate matter (<0.25, 0.25-0.5, 0.5-1.0, 1.0-2.5 and 2.5-10 μm) were collected at the electric arc furnace and rolling mill. The PAHs were sampled with the personal cascade impactor and identified by HPLC with fluorescence detector. The obtained results showed that collected PAH contents were significantly higher at the electric arc furnace. The highest content of total PAHs (93 ng m(-3)) was present in the smallest particles of 0.5 μm aerodynamic diameter or less, indicating that the ultrafine particles have a high contribution in the overall PM(2.5) fine fraction. Concentrations of Py, CH, BbF, BaP and BghiP came to 76% of total PAHs content in <0.25 μm fraction. The five- and six-ring compounds (BbF, BkF, BaP, DBA, BghiP) with 4-ring chrysene presented typical unimodal size distribution with one predominant peak for this particles' diameter. Phenanthrene and fluoranthene exhibited highest concentrations on coarse particles in the range of 10-2.5 μm, decreasing with decrease of a particle size fraction. Using the toxic equivalent factor (TEF), the mean contributions of the carcinogenic potency of BaP to the air samples collected at the arc furnace and rolling mill (fraction below 0.25 μm) were determined to be 66.3% and 50.3%, respectively.