Pyrene In Sediments Research Articles

Degradation of pyrene in sediments based on the activation of peroxymonosulfate with nitrogen-doped magnetic biochar: Synergistic effect and mechanism

Pyrene (PYR) is a typical high molecular weight polycyclic aromatic hydrocarbon (HMW-PAH) with potential biotoxicity and resistance to biodegradation, and the accumulation of PYR in sediments increases the risk to ecosystems. Therefore, this study evaluated the catalytic performance of nitrogen-doped magnetic biochar-activated peroxymonosulfate system (NMBC/PMS) on PYR in sediments and elucidated its mechanism. The results showed that the degradation rate of PYR in sediments by the NMBC/PMS system reached 87% at PMS= 1 × 10−4 M, NMBC= 3.0 g/L and pH= 9, which conformed to the pseudo-first-order rate law, and the rate constant(Kobs) was 7.3 × 10−2 h−1. The high adsorption performance of NMBC was attributed to π-π electron donor-acceptor interactions (π-π EDA). The high degradation performance of NMBC/PMS system was attributed to the active sites generated by graphitization, magnetism, and electronegativity of NMBC, which were the key to activate PMS to degrade PYR. The results of X-ray photoelectron spectroscopy (XPS), quenching experiments and electron paramagnetic resonance (EPR) analysis indicated that N-doping and Fe3O4-loading on NMBC synergistically promoted the degradation of PYR. In addition, the mechanism of PYR degradation by NMBC/PMS system was investigated, indicating that SO4·-, HO·and 1O2 were the main reactive oxygen species. The excellent recoverability of NMBC showed its application potential. The NMBC/PMS system developed in this study provided a theoretical basis for a future multi-pathway synergistic degradation mechanism of PYR in sediments.

Microbial carriers promote and guide pyrene migration in sediments

Microbial carriers may co-transport polycyclic aromatic hydrocarbons (PAHs), but lack substantial experimental evidence. Cable bacteria use gliding or twitching motility to access sulfide; hence, they could be important microbial carriers in co-transporting PAHs from the sediment-water interface into suboxic zones. In this study, the effect of cable bacteria on pyrene migration was investigated by connecting or blocking the paths of cable bacteria to the suboxic zones. The results showed that downward migration of pyrene in the connecting groups were significantly higher (17.3–49.2%, p < 0.01) than those in the control groups. Meanwhile, significant downward migration of microbial communities in the connecting groups were also observed, including abundant filamentous-motile microorganisms, especially cable bacteria. The adsorption of surrounding particles by cable bacteria were morphologically evidenced. The biomechanical model based on the Peclet number indicated that filamentous-motile microorganisms demonstrated stronger adsorption ability for pyrene than other microorganisms. Supposedly, the downward migration of microbial communities, especially cable bacteria, significantly enhanced pyrene migration, thus influencing the distribution and ecological risk of pyrene in sediments. This study provides new insights into the important roles of motile microorganisms in the migration of PAHs in sediments, shedding lights on guidance for ecological risk assessment of PAHs.

微生物微电解质体系降解压裂返排液沉降底泥中苯并(a)芘的应用研究

微生物微电解质体系降解压裂返排液沉降底泥中苯并(a)芘的应用研究

Phytoremediation of PAH-contaminated sediments with different organic matter contents by Potamogeton crispus L.

In this study, phytoremediation of polycyclic aromatic hydrocarbon (PAH)-contaminated sediments with different contents of sediment organic matter (SOM) by Potamogeton crispus L. was investigated to find out the key factor controlling PAH dissipation enhancements. After a 36-day experiment, dissipation ratios of phenanthrene and pyrene in sediments were improved by P. crispus but decreased with increasing SOM content, no matter with or without P. crispus. Furthermore, the results of polyphenol oxidase activity and PAH bioavailability showed that they were both higher in planted treatments than in unplanted treatments. Finally, the enhancements of rapidly desorbing fraction (i.e., the main portion to be readily biodegradable) in sediments with SOM contents of 1.20%, 3.14%, and 5.08% by plants were 20.0%, 40.7%, and 66.7% for phenanthrene, 22.2%, 36.8%, and 58.8% for pyrene, respectively, which is consistent with the change trends of dissipation enhancements of the contaminants in sediments. However, there was no significant correlation between the enhancement of polyphenol oxidase activity and the dissipation enhancement. These results suggested that the improved bioavailability by P. crispus should be the key factor leading to the dissipation enhancements of the contaminants in sediments with different SOM contents, which provides essential information for phytoremediation of PAH-contaminated sediments.

Dissipation characteristics of pyrene and ecological contribution of submerged macrophytes and their biofilms-leaves in constructed wetland

The dissipation characteristics of pyrene and ecological contribution of submerged macrophytes (Vallisneria natans, Hydrilla verticillata and artificial plant) and their biofilms-leaves in constructed wetland system were investigated by high-throughput sequencing. Results showed a non-negligible ecological contribution of submerged macrophytes and their biofilms-leaves in dissipating pyrene in planted sediments (33.25–43.00%) in contrast with unplanted system (23.25–26.50%). Alpha and Beta diversity analysis indicated that bacterial community structures were influenced in order of attached surface > incubation time > spiking concentration of pyrene in sediment. Difference analysis suggested that attached surface tended to affect the rare genera up to significant level compared with incubation time. In addition, RDA analysis showed that PAH-degrading bacteria in biofilms-leaves of submerged macrophytes were positively correlated with the dissipation ratios of pyrene. Interestingly, nitrogen transforming microorganisms were also influenced in the presence of pyrene, while submerged macrophytes contributed to alleviate the impact.

Dissipation gradient of pyrene in the rhizosphere of Potamogeton crispus L.

In this study, a self-designed laminar rhizobox divided into six separate compartments was used to investigate the degradation gradient of pyrene in the rhizosphere of submerged aquatic plant Potamogeton crispus L. (P. crispus). At the end of a 30-day experiment, P. crispus significantly increased the dissipation of pyrene by 16.7-24.5% within the distance of 4mm from root surface. Concentrations of 1-OH-pyrene, a hydroxylated metabolite of pyrene, were 1.4-15.5 times higher in unplanted treatment than in planted treatment and were positively correlated to pyrene concentrations. At the same time, aerobic bacterial biomass indicated by phospholipid fatty acid content and polycyclic aromatic hydrocarbon (PAH)-degrading bacterial population were both significantly enhanced by P. crispus within the distance of 8mm from root surface. Sediment redox potential within the distance of 5mm from root surface was also obviously improved. Pearson analysis indicated that dissipation ratios of pyrene were positively correlated to PAH-degrading bacterial populations and aerobic bacterial biomasses. Based on the rhizosphere gradient zones of different parameters influenced by P. crispus as well as the correlation analysis, it could be concluded that oxygen is the limiting factor in remediating pyrene in sediments.

Importance of the structure and nanoporosity of organic matter on the desorption kinetics of benzo[a]pyrene in sediments

The desorption kinetics and mechanism were investigated using a Tenax extraction technique on different sediments spiked with radiocarbon-labeled benzo[a]pyrene (BaP). Five sedimentary fractions were sequentially fractionated, and the only nonhydrolyzable organic carbon fractions (NHC) were characterized using advanced solid-state 13C nuclear magnetic resonance spectroscopy (NMR), improved six end-member model, and a CO2 gas adsorption technique. The sediments contained high percentages of algaenan and/or sporopollenin but low percentages of black carbon and lignin. A first-order, two-compartment kinetics model described the desorption process very well (R2 > 0.990). Although some of the organic carbon fractions were significantly related to the desorption kinetics parameters, the NHC fractions showed the highly significant correlation. Moreover, the nanoporosity or specific surface area (SSA) of the NHC fractions was highly related to their OC contents and aliphatic C (R2 = 0.960, p < 0.01). The multiple regression equations among the desorption kinetics parameters, structural parameters, and nanoporosity were well established (R2=>0.999). Nanoporosity and aromatic C were the dominant contributors. Furthermore, the enhanced percentages of desorbed BaP at elevated temperatures significantly showed a linear regression with the structure and nanoporosity. To our knowledge, the above evidence demonstrates for the first time that the transfer (or diffusion) of BaP in the nanopores of condensed aromatic components is the dominant mechanism of the desorption kinetics of BaP at organic matter particle scale.

Effects of biochars derived from different pyrolysis temperatures on growth of Vallisneria spiralis and dissipation of polycyclic aromatic hydrocarbons in sediments

Wheat straw biochars produced at 400 and 700 °C (BC400 and BC700) were used to investigate their effects on the growth of Vallisneria spiralis and the dissipation of phenanthrene and pyrene in sediments. Biochar amendment inhibited the growth of V. spiralis to some extent at the end of 54-day experiment, and the inhibition was stronger by BC700 than by BC400. In unplanted sediments, PAH dissipation was significantly retarded by BC400 but slightly increased by BC700 although bioavailable fraction of the contaminants extracted by butanol was more significantly reduced by the addition of BC700. It is possible that the contaminants sorbed to BC700 are still bioavailable to bacteria. Planting V. spiralis significantly enhanced the dissipation of phenanthrene and pyrene in biochar-unamended sediments, but showed only small effect on the dissipation in biochar-amended sediments. Moreover, redox potential was much higher in planted sediments than in unplanted sediments no matter whether the biochars were amended or not, suggesting that oxygen is not the limiting factor for the degradation in biochar-amended sediments.

Phytoremediation of PAH-contaminated sediments by Potamogeton crispus L. with four plant densities

In order to investigate the effect of plant density of Potamogeton crispus L. on the remediation of sediments contaminated by polycyclic aromatic hydrocarbons, a 54-day experiment with four plant densities(642, 1,604, 2,567 and 3,530 plants/m2)was conducted. The results showed higher plant density with slower plant growth rate. Surface area per plant was the most sensitive root parameter to plant density. At the end of the 54-day experiment, planting P. crispus enhanced the dissipation ratios of phenanthrene and pyrene in sediments by 6.5%—26.2% and 0.95%—13.6%, respectively. The dissipation increment increased with increasing plant density. Plant uptake accounted for only a small portion of the dissipation increments. Furthermore, P. crispus could evidently improve sediment redox potentials, and strong positive correlations between root surface area and the redox potential as well as between the redox potentials and the dissipation ratios of phenanthrene and pyrene were obtained, indicating that the oxygen released by the roots of P. crispus might be the main mechanism by which P. crispus enhanced the dissipation of PAHs in sediments.

Presence of PAHs in water and sediments of the Colombian Cauca River during heavy rain episodes, and implications for risk assessment

In Colombia little attention has been paid to river pollution with Polycyclic Aromatic Hydrocarbons (PAHs). Low environmental control and legislation in such emerging region could significantly contribute to high PAHs releases. In this study, we report the presence of PAHs in water and sediments of the Cauca River (Colombia). Three sampling campaigns were carried out between May 2010 and June 2011, and the samples were collected at eight relevant sites. The sampling time included measuring before, during, and after a season of heavy rains, which were influenced by the global coupled ocean-atmospheric phenomenon, which affected tropical countries with huge flooding, commonly called “La Niña”, and/or “El Niño” Southern Oscillation (ENSO). The highest mean ∑PAH concentrations were 4476.5ng/l and 1582.7ng/g in water and sediments, respectively. The PAHs most detected were Benzo[b]fluoranthene, Benzo[k]fluoranthene, and Pyrene in sediments; and Fluorene, Acenaphtylene, and Anthracene in water. After the season of rains statistically significant higher PAH concentrations were detected. The results of the study were compared to other rivers worldwide at both environmental compartments, and did not show concentrations of special concern. In some sites, concentrations detected of PAHs were higher than screening benchmarks for ecological protection. Estimation of human health risks was carried out, and the results suggested some likely carcinogenic effects due to PAHs especially in children exposed during current recreational swimming and adults working in low technology sand extraction.

Interactions between Potamogeton crispus L. and phenanthrene and pyrene in sediments

Information on the interaction between submerged macrophytes and organic contaminants in sediments is important for successful phytoremediation. In this study, the growth response and remedial function of Potamogeton crispus L. (P. crispus) to phenanthrene and pyrene in sediments were investigated. P. crispus was obtained by a tissue culture technique. Surface sediments (top 0–15 cm) were collected from the Haihe River, Tianjin, China. Six different concentrations of phenanthrene and pyrene (8–180 mg kg−1 dry sediment) were spiked in the sediments. At the end of the 54-day experiment, chlorophyll content, plant length and fresh weight, and root morphology were measured. Concentrations of phenanthrene and pyrene in P. crispus and sediments, as well as the activities of polyphenol oxidase in sediments, were analyzed. P. crispus growth was promoted by polycyclic aromatic hydrocarbons (PAHs) in sediments (range of 8–80 mg kg−1) and was not inhibited until the PAH concentration was increased to 180 mg kg−1. Root tip number was the most sensitive parameter. The presence of P. crispus evidently enhanced the removal of phenanthrene and pyrene from sediments by 18.3 − 34.1 and 14.1 − 27.8 %, respectively. The dissipation increments increased with increasing PAH concentration and showed similar values when PAH concentration was >48 mg kg−1. Plant accumulation of phenanthrene and pyrene counted for less than 1.05 and 2.46 % of the total increments, respectively. Moreover, the presence of P. crispus could improve the activities of polyphenol oxidase. A positive correlation between the dissipation increments of PAHs and the differences of polyphenol oxidase activities between planted and unplanted sediments was obtained. P. crispus could tolerate high doses of PAHs. The growth of P. crispus was stimulated by phenanthrene and pyrene in sediments over a large concentration range. Moreover, the presence of P. crispus enhanced the removal of PAHs, which was closely related to polyphenol oxidase activities as a result of plant growth stimulation. Therefore, P. crispus should be a suitable choice for phytoremediation of PAH-contaminated sediments.

Effect of plant density on phytoremediation of polycyclic aromatic hydrocarbons contaminated sediments with Vallisneria spiralis

A 54-day-long study was conducted to investigate the effect of plant density (260, 780, 1300 and 2080 plants m−2) of Vallisneria spiralis on the remediation of sediments contaminated by polycyclic aromatic hydrocarbons (PAHs). Dissipation ratios of phenanthrene and pyrene in sediments were initially the highest in treatment of 2080 plants m−2. However, after a 54-day incubation, no statistical difference was observed in the dissipation ratios under different planting density treatments (p > 0.05) except lower dissipation ratio of phenanthrene in treatment of 780 plants m−2. Compared with the unplanted sediments, the dissipation ratios of phenanthrene and pyrene in planted sediments increased by 15.2–21.5% and 9.1–12.7%. Considering the sustainability of the ecosystem, lower plant density (e.g., 260 plants m−2) should be a better selection for phytoremediation of PAHs. Mass balance calculation indicated that plant accumulation accounted for less than 0.39% of the dissipation increment. Furthermore, dissipation ratio of PAHs was positively related to PAH-degrading bacterial population, suggesting that microbial degradation played a major role in the V. spiralis-promoted remediation. The redox potential, a signal of oxygen in sediments, was measured. Positive redox potentials were found in sediments with V. spiralis as a result of oxygen released by roots. Moreover, sediment redox potential positively correlated with PAH-degrading bacterial population. Considering high oxygen demand of PAHs catabolism and reduced conditions in unplanted sediments, it can be concluded that the enhanced dissipation of PAHs is mainly related to oxygen released by roots.

Rhizodegradation gradients of phenanthrene and pyrene in sediment of mangrove ( Kandelia candel (L.) Druce)

A greenhouse experiment was conducted to evaluate degradation gradient of spiked phenanthrene (Ph, 10 mg kg −1) and pyrene (Py, 10 mg kg −1) in rhizosphere of mangrove Kandelia candel (L.) Druce. Rhizosphere model system was set up using a self-design laminar rhizoboxes which divided into eight separate compartments at various distances from the root surface. After 60 days of plant growth, presence of the plant significantly enhanced the dissipation of Ph (47.7%) and Py (37.6%) from contaminated sediment. Higher degradation rates of the PAHs were observed at 3 mm from the root zone (56.8% Ph and 47.7% Py). The degradation gradient followed the order: near rhizosphere > root compartment > far-rhizosphere soil zones for both contaminants where mangrove was grown. Contribution of direct plant uptake and accumulation of Ph and Py were very low compared to the plant enhanced dissipation. By contrast, plant-promoted biodegradation was the predominant contribution to the remediation enhancement. The correlation analysis indicates a negative relation between biological activities (microbial biomass carbon, dehydrogenase, urease, and phosphatase activity) and residual concentrations of Ph and Py in planted soils. Our results suggested that mangrove rhizosphere was effective in promoting the depletion of aromatic hydrocarbons in contaminated sediments.

Anionic Surfactant-Based Extraction of Polycyclic Aromatic Hydrocarbons from Sediment

Polycyclic aromatic hydrocarbons (PAHs) including phenathrene, fluoranthene, and pyrene in sediment were extracted with aqueous micellar solutions of anionic surfactants. The surfactants examined were sodium dodecyl sulfate, sodium oleate, and sodium di(2-ethylhexyl) sulfosuccinate. The extraction yields of PAHs increased with increasing the surfactant concentration and the extraction time. They reached constant values (ca. 30%), which agreed with results obtained by the 1-butanol extraction method. The present results suggest the usefulness of surfactant-based extraction for evaluating the bioavailability of organic pollutants in sediments.

Modeling the fate of benzo[a]pyrene in the wastewater-irrigated areas of Tianjin with a fugacity model.

A Level III fugacity model was applied to characterize the transfer processes and environmental fate of benzo[a]pyrene in wastewater-irrigated areas of Tianjin, China. The physical-chemical properties and transfer parameters of benzo[a]pyrene were used in the model and the concentration distribution of benzo[a]pyrene in sediment, soil, water, air, fish, and crop compartments, as well as transfer fluxes across the compartments, were then derived under steady-state assumptions. The calculated results were compared with monitoring data for air, soil, water, and sediment collected from the literature. The results indicate that there was generally good agreement and the differences were within an order of magnitude for air, soil, and sediment. The concentration of benzo[a]pyrene in the ambient air in the area was very low with a majority present sorbed to aerosol. In the water compartment, approximately 70% of benzo[a]pyrene dissolved in water phase. Relatively high concentrations of the compound were found in the soil and sediment, with the soil serving as the dominant sink in the area. Benzo[a]pyrene, with a slow metabolic rate, was found to accumulate in fish in the area.

Effects of the polychaetes Nereis diversicolor and Arenicola marina on the fate and distribution of pyrene in sediments

Effects of the polychaetes Nereis diversicolor and Arenicola marina on the distribution, metabolism and removal of [ 14 C-4,5, 9 ,10]-pyrene in sediment microcosms were studied over 42 and 53 d, respectively. Unmetabolized pyrene, water- and organic-soluble pyrene metabolites were quantified in sediment, interstitial water and overlying water, and 14 CO 2 production was also assessed. Both N. diversicolor and A. marina enhanced fluxes of sediment-associated pyrene and metabolites into overlying water but to different extents. The major pathway of pyrene removal from sediments with N. diversicolor was release of water-soluble metabolites, probably formed by metabolism in N. diversicolor. In contrast, flushing of unmetabolized pyrene due to bioturbation was the major removal route from sediments with A. marina. Additionally, increased 14 CO 2 production and concentrations of water-soluble metabolites were also observed in overlying water indicating that A. marina also stimulated the metabolism of pyrene. The high production of water-soluble metabolites was probably due to endogenous metabolism in the lugworm itself, whereas the increased 14 CO 2 production indicated a stimulation of microbial metabolism. After 42 d, only 75 % of the originally added amount of pyrene remained associated to sediment particles in microcosms inhabited by N. diversicolor, whereas no significant reduction was observed in microcosms with A. marina due to the necessity of using large amounts of sediment in the lugworm experiment. The actual flux of pyrene and metabolites to overlying water was higher in microcosms with A. marina than with N. diversicolor. Both A. marina and N. diversicolor significantly enhanced the removal pyrene from the sediment, but differences in feeding and life strategies resulted in different removal paths and extents.

Modeling the Fate of Benzo[]pyrene in the Wastewater-Irrigated Areas of Tianjin with a Fugacity Model

A Level III fugacity model was applied to characterize the transfer processes and environmental fate of benzo[a]pyrene in wastewater-irrigated areas of Tianjin, China. The physical–chemical properties and transfer parameters of benzo[a]pyrene were used in the model and the concentration distribution of benzo[a]pyrene in sediment, soil, water, air, fish, and crop compartments, as well as transfer fluxes across the compartments, were then derived under steady-state assumptions. The calculated results were compared with monitoring data for air, soil, water, and sediment collected from the literature. The results indicate that there was generally good agreement and the differences were within an order of magnitude for air, soil, and sediment. The concentration of benzo[a]pyrene in the ambient air in the area was very low with a majority present sorbed to aerosol. In the water compartment, approximately 70% of benzo[a]pyrene dissolved in water phase. Relatively high concentrations of the compound were found in the soil and sediment, with the soil serving as the dominant sink in the area. Benzo[a]pyrene, with a slow metabolic rate, was found to accumulate in fish in the area.

Petroleum hydrocarbons and trace metals in nearshore Gulf sediments and biota before and after the 1991 war: An assessment of temporal and spatial trends

Immediately following the 1991 Gulf War, a survey was organized to determine the extent and degree of contamination by petroleum hydrocarbons and trace metals that entered the Gulf from the massive oil spill and oil field fires in Kuwait. Between June–October 1991 samples of nearshore sediments, bivalves and fish were collected from Kuwait, Saudi Arabia, Bahrain, UAE and Oman. Analyses revealed that the highest levels of contamination were along the heavily-impacted coast of Saudi Arabia between Ras Al Khafji and Ras Al Ghar, where concentrations of total petroleum hydrocarbons (expressed as Kuwait crude oil equivalents) ranged from 62–1400 μg g −1 dry wt in surface sediments, 570–2600 μg g −1 dry wt in clams and 9.6–31 μg g −1 dry wt in fish muscle. Gas chromatographic analyses indicated that much of the oil in the intertidal zone had substantially degraded within a few months of the spill. Concentrations of the oil-related metals Ni and V were slightly elevated in oil-contaminated sediments from Saudi Arabia but elsewhere in the Gulf were similar to levels measured in earlier years at those sites. This initial regional survey demonstrated that hydrocarbon contamination originating from the war-related pollution events was restricted to approximately 400 km from the source, that levels of combustion derived PAHs in the marine environment at that time (e.g. 1–450 ng g −1 dry wt for pyrene in sediments) were of the same order as those which have been measured in several coastal areas of the eastern United States and northern Europe, and that outside the immediate area of impact, petroleum hydrocarbon and trace metal levels in sediment and bivalves were generally as low as, or lower than, those concentrations measured at the same sites before the war.

Benz(a)pyrene input and occurrence in a marine area affected by refinery effluent

The load of benz(a)pyrene in a marine coastal area in the vicinity of a town and an oil refinery has been estimated. The levels of benz(a)pyrene in refinery effluent, municipal waste water, urban run-off, rivers, and atmospheric fall-out have been determined. In the study area the major source was atmospheric fall-out. The levels of benz(a)pyrene in sediments and in mussels,Mytilus edilus have been determined. The possible removal of benz(a)pyrene from the study area has been evaluated. This includes sedimentation, degradation, and advective water transport.

The Carcinogenic Load of the Environment: Benzo(a)Pyrene in Sediments of Arctic Waters

Baseline levels of the chemical carcinogen benzo(a)pyrene were measured in arctic sediments. Levels were highest in samples from the Mackenzie River delta and adjacent areas of the Beaufort Sea. The distribution of carcinogen did not correspond to the location of inhabited areas - a natural rather than a man-made source for polycyclic aromatic hydrocarbons in arctic sediments is indicated.