Characterization,sources and ecological risk assessment of polycyclic aromatic hydrocarbons in surface sediments from the mangroves of China

We characterized 16 polycyclic aromatic hydrocarbons (PAHs) in surface sediments of natural mangrove habitats in China, as well as assessed their sources and the risks they pose. Our results indicate that the total concentrations of the 16 PAHs ranged from 3.16 to 464.05 ng g^?1 dw (mean value of 72.80 ng g^?1 dw), which were generally lower than those in other coastal environments in China and in other countries. The compositional patterns were dominated by four-ring PAHs, including fluoranthene, pyrene, benzo[a]anthracene and chrysene. Petrogenic sources, specifically, petroleum spills, were the dominant sources of PAHs in the surficial sediments of mangroves in China. Selected ratios of PAHs from two-tailed Pearson correlation analysis and principal-component analysis for different sites also indicate pyrolytic sources of PAHs. Results of the ecological risk assessment show little negative effect of most of the PAHs in the surface sediments. Overall, the data obtained in this study reveal relative low PAHs pollution in the mangrove swamps of China.     

Polycyclic aromatic hydrocarbons (PAHs) concentration levels,pattern, source identification,and human risk assessment in foliar dust from urban to rural areas in Nanjing,China

Environmental health is an essential component of quality of life in modern societies. Foliar dust contains polycyclic aromatic hydrocarbons (PAHs) that may have harmful effects on human health. The PAHs concentration of foliar dust is useful to assess environmental air pollution. Our results indicate that: (1) the highest levels of PAHs were distributed in urban areas, with a mean of 3430.23 ng·g^?1, lower mean concentrations were found in suburban (2282.12 ng·g^?1), and rural areas (1671.06 ng·g^?1). (2) Diagnostic ratios and principal component analysis were used to identify the sources of PAHs: Gasoline vehicle traffic emissions were the predominant source in urban areas, along with coal and coke combustion. In suburban areas, the main sources were petroleum combustion (especially liquid fossil fuels) and coal combustion. Coal and wood combustion were the primary source of PAHs in foliar dust in rural areas. (3) The incremental lifetime cancer risk (ILCR), estimated based on the results of this study indicate that urban residents were potentially exposed to high cancer risk via both dust ingestion and dermal contact. We conclude that urbanization has significant effects on the PAH concentrations of foliar dust, illustrating the importance of trees in improving air quality in urban areas.     

Distribution characteristics,sources, and ecological risk assessment of polycyclic aromatic hydrocarbons in sediments from Haizhou Bay,China

Sixteen USEPA priority polycyclic aromatic hydrocarbons (PAHs) were analyzed by gas chromatography–mass spectrometry. Twenty samples were collected from the surface sediments of Haizhou Bay in this survey. This research aimed to identify the PAHs' contamination level, composition pattern, pollution sources, and assess the ecological risk of PAHs. The results showed that the sum of PAH concentrations ranged from 116.6 ng g^?1 to 2414.9 ng g^?1 (mean: 662.42 ng g^?1), which is higher than the reported values for different wetlands worldwide. Three- and four-ring PAHs (accounts for more than 70% of the total PAH content) were predominant in the wetland sediment. The PAHs source distribution in the surface sediments were determined using diagnostic ratio and PCA/MLR. Consequently, multiple PAHs sources were found. Of the total PAH, 79.25% was derived from vehicular emission, 20.75% from coal combustion. The effect range low/effect range median (ERL/ERM) values indicated a low toxicity risk level. However, the fluoranthene concentrations exceeded the ERL level, and even the ERM level, in some stations. The mean effects range–median quotient (M-ERM-Q) suggests a low ecological risk for the PAHs in the sediments.     

Identification of the highest potential human health and environmental hazard in contaminated sediment near the point sources in the northwest Persian Gulf

Abstract

The overall goal of this work was to determine the concentration levels and the potential ecological risks of 30 polycyclic aromatic hydrocarbons in the Persian Gulf sediments, Iran. The study also predicted the bioaccumulation of PAHs using the Monte Carlo simulation. For these goals, 68 surface sediment samples were collected from the Persian Gulf in January 2017. Then, the experiments were performed with Soxhlet system, chromatographic column and GC-MS instrument. According to the Canadian Sediment Quality Guidelines, 35.29% of sampling sites exhibited high potential adverse biological effects and 79.41% of samples have a low probability of toxicity. The mean bioaccumulated concentrations of carcinogenic PAHs in the Persian Gulf were predicted as 207.78?±?262.23, 116.06?±?146.47 and 69.26?±?87.41?ng g^–1 for mollusks, shrimps and crabs, respectively. The mean Toxic Equivalency and Mutagenic Equivalent Quotient for sediments was 702.06?±?1012.37 and 500.37?±?665.71?ng g^?1, respectively. The 95th percentile carcinogenic and non-carcinogenic risks calculated for children and adults were lower than the threshold values of 10^?6 and 1.0, respectively, revealing no potential health risk. The highest potential risks for toxicity were observed at sampling sites close to the Nowruz oil field and Mahshahr petrochemical economic zone based on the highest TEQcarc and MEQcarc values in this area.     

Characterization,source apportionment,and human health risk assessment of polycyclic aromatic hydrocarbons (PAHs) in road dust of a small island state in the Caribbean

Sixty-four and fifty-six road dust samples were collected over two seasons from various locations throughout the island of Trinidad and analyzed for the 16 priority PAHs. Total PAH concentrations ranged from 21 ng g^?1 to 4723 ng g^?1 (d.w.) for the rainy season and 36 ng g^?1 to 2428 ng g^?1 (d.w.) for the dry season. The Σ4–6 ring PAHs accounted for 88% and 63% of the 16 PAHs in road dust samples for the rainy and dry seasons, respectively. PAH diagnostic ratios, principal component analysis, and cluster analysis revealed both pyrogenic and petrogenic sources in road dust for the two seasons, with major contributions from vehicular emissions. Contributions from incomplete combustion and petroleum sources were also identified. The estimated Incremental Lifetime Cancer Risk (ILCR) associated with exposure to road dust PAHs in Trinidad for the rainy and dry seasons indicated no potential risk for both children and adults, as denoted by ILCR values lower than 10^?6.     

Distribution of surface soil mercury of Wuda old mining area,Inner Mongolia,China

In this study, mercury (Hg) concentrations in dustfall and topsoil were investigated. Three hundred forty-four samples were collected, including dustfall and topsoil samples, across an area of ～180 km² in Wuda, China. Dustfall Hg concentration in Wuda ranged from 10 to 6453 ng·g^?1_, with an average of 305 ng·g^?1, and topsoil Hg concentration ranged from 3 to 1537 ng·g^?1, with an average value of 135 ng·g^?1. The average dustfall Hg concentrations in the coalfield, industrial park, and urban areas were 289 ng·g^?1, 809 ng·g^?1, and 160 ng·g^?1, respectively, and the corresponding average topsoil Hg concentrations were 216 ng·g^?1, 242 ng·g^?1, and 91 ng·g^?1. Hg concentrations were significantly higher in the coalfield, industrial park, and urban areas compared with background values for Wuda and China tide soil. The coal Hg concentrations ranged from 273 to 346 ng·g^?1, with an average value of 317 ng·g^?1. Comparison of the Hg concentrations of Wuda coal with other regions and countries, indicated that Hg concentrations were significantly enriched in coal, highlighting that coal is the primary Hg source for Wuda District. While coal fires provided the primary source of Hg, some higher Hg values were caused by factors such as gangue hills and coalfield topography, the use of activated carbon with HgCl₂ as a catalyst in the industrial park, and several coal washeries in wasteland areas. In addition to atmospheric Hg, underground coal seam emissions served as another potential Hg source in the coalfield. The surface soil Hg in the coalfield and industrial park areas should be given closer attention in the future.     

Polycyclic Aromatic Hydrocarbon (PAH) Contamination in the Urban Topsoils of Shenyang,China

Polycyclic aromatic hydrocarbons (PAHs) in the surface urban soils of Shenyang in Northeastern China were investigated. The total concentration of the PAHs ranged from 0.09 to 8.35 mg kg^?1, with an average value of 1.51 ± 1.64 mg kg^?1. 3–5-ring PAHs accounted for 90% of total PAHs. The functional areas, such as the industrial regions (4.95 mg kg^?1) and main roads (1.56 mg kg^?1), as well as the administrative divisions, including the districts of Shenhe (1.49 mg kg^?1), Heping (2.08 mg kg^?1), and Tiexi (2.14 mg kg^?1), were heavily polluted by PAHs. The diagnostic ratios and principal component analysis (PCA) for PAHs indicate that the pollutants probably originated primarily from coal combustion and petroleum sources. The Nemerow composite index, used to assess environmental quality, shows that the soil samples were heavily polluted with PAHs, and although 52.8% of the soil sampling sites were safe, 47.2% of the soil sampling sites registered different grades of PAH pollution. The PAH contamination in Shenyang emphasizes the need for controlling fossil fuel combustion and traffic exhaust.     

High variability in iron-bound organic carbon among five boreal lake sediments

Being both stable carbon sinks and greenhouse gas sources, boreal lake sediments represent significant players in carbon (C) cycling. The release of dissolved organic carbon (DOC) into anoxic water is a widespread phenomenon in boreal lakes with impact on sediment C budgets. The association of OC with iron (Fe) is assumed to play an important role for this anoxic OC release via the dissimilatory reduction of Fe, but also to influence the stabilization of OC in sediments. To investigate the role of Fe–OC association for OC dynamics in different boreal lake sediments, we compared the content of Fe-bound OC [Fe–OC, defined as citrate bicarbonate dithionite (CBD) extractable OC] and the extent of reductive dissolution of solid-phase Fe and OC at anoxia. We found high among-lake variability in Fe–OC content, and while the amount of Fe–OC was high in three of the lakes (980–1920 µmol g^?1), the overall contribution of Fe–OC to the sediment OC pool in all study lakes was not higher than 11%. No linkages between the amount of the Fe–OC pool and lake or sediment characteristics (e.g., pH, DOC concentration, sediment OC content, C:N ratio) could be identified. The observed release of OC from anoxic sediment may be derived from dissolution of Fe–OC in the lake sediments with high Fe–OC, but in other lake sediments, OC release during anoxia exceeded the sediment Fe–OC pool, indicating low contribution of reductive Fe dissolution to OC release from these lake sediments. The range of the investigated boreal lakes reflects the high variability in the size of the sediment Fe–OC pool (0–1920 µmol g^?1) and CBD-extractable Fe (123–4050 µmol g^?1), which was not mirrored in the extent of reductive dissolution of Fe (18.9–84.6 µmol g^?1) and OC (1080–1700 µmol g^?1) during anoxia, suggesting that Fe-bound OC may play a minor role for sediment OC release in boreal lakes. However, studies of redox-related OC cycling in boreal lake sediments should consider that the amount of Fe–OC can be high in some lakes.     

Pollution assessment of organochlorine pesticides in urban agricultural soils of Jilin City,China

The content, source, and pollution level of organochlorine pesticides (OCPs) in soils are necessary to assess potential risks to eco-environment and human health, and to target environment-friendly policies. A total of 50 surface soil samples were collected from urban vegetable fields of Jilin City and thirteen OCPs were analyzed. The concentrations were in the ranges of 3.16–48.35 ng·g^?1 for Dichloro-Diphenyl-Tricgloroethanes (DDTs, sum of o, p′-DDT, p, p′-DDT, p, p′-DDD, and p, p′-DDE), 4.37–44.77 ng·g^?1 for Hexachlorocyclohexanes (HCHs, sum of α-HCH, β-HCH, γ-HCH, and δ-HCH), 1.19–13.17 ng·g^?1 for Chlordanes (sum of heptachlor, t-chlordane, and c-chlordane), 0.24–2.60 ng·g^?1 for aldrin, and nd–3.43 ng·g^?1 for dieldrin, respectively. The different compositions indicated that the residues of DDTs and HCHs originated mainly from the historical application, while chlordanes were mostly from recent input. On the basis of soil quality standards of China and the Netherlands, DDTs and chlordanes in this study were categorized as light pollution, and HCHs were classified as no pollution for the majority of soil samples. There are a variety of OCPs residues in urban vegetable soils of Jilin City, but it is still safe and suitable for agricultural production.     

Bioaccessibility-Based Risk Assessment of PAHs in Soils from Sites of Different Anthropogenic Activities in Lagos,Nigeria Using the Fed Organic Estimation Human Simulation Test Method

The aim of this study was to carry out a bioaccessibility-based risk assessment of polycyclic aromatic hydrocarbons (PAHs) in soils from sites of different anthropogenic activities in Lagos, Nigeria. Using an in vitro gastrointestinal model—Fed Organic Estimation Human Simulation Test method (FOREShT), the concentration of bioaccessible 16 priority US Environmental Protection Agency (USEPA) PAHs in soils were determined. Total concentration of 16 priority USEPA PAHs was also determined. The concentration range was 702–253,922 ng g^?1 and 92–760 ng g^?1 for total and bioaccessible PAHs, respectively. For persons involved with activities at these sites no health risks were observed, based on bioaccessibility values of PAHs. Mean daily intake of PAHs from these soils were below the oral mean daily intake threshold for PAHs in food. Also, overall estimated theoretical cancer risk (2.5 × 10^?09, 6.5 × 10^?07, 5.5 × 10^?10, 2.7 × 10^?09, 6.5 × 10^?10, 9.5 × 10^?10, 2.0 × 10^?09, and 4.1 × 10^?07 for the eight sites based on their bioaccessible concentration) for exposure to PAHs in surface soils were below the health guidelines for extreme (1 × 10^?04) and normal (1 × 10^?06) exposures.     

Potential nitrogen and carbon processing in a landscape rich in milldam legacy sediments

Recent identification of the widespread distribution of legacy sediments deposited in historic mill ponds has increased concern regarding their role in controlling land–water nutrient transfers in the mid-Atlantic region of the US. At Big Spring Run in Lancaster, Pennsylvania, legacy sediments now overlay a buried relict hydric soil (a former wetland soil). We compared C and N processing in legacy sediment to upland soils to identify soil zones that may be sources or sinks for N transported toward streams. We hypothesized that legacy sediments would have high nitrification rates (due to recent agricultural N inputs), while relict hydric soils buried beneath the legacy sediments would be N sinks revealed via negative net nitrification and/or positive denitrification (because the buried former wetland soils are C rich but low in O₂). Potential net nitrification ranged from 9.2 to 77.9 g m^?2 year^?1 and potential C mineralization ranged from 223 to 1,737 g m^?2 year^?1, with the highest rates in surface soils for both legacy sediments and uplands. Potential denitrification ranged from 0.37 to 21.72 g m^?2 year^?1, with the buried relict hydric soils denitrifying an average of 6.2 g m^?2 year^?1. Contrary to our hypothesis, relict hydric layers did not have negative potential nitrification or high positive potential denitrification rates, in part because microbial activity was low relative to surface soils, as indicated by low nitrifier population activity, low substrate induced respiration, and low exoenzyme activity. Despite high soil C concentrations, buried relict hydric soils do not provide the ecological services expected from a wetland soil. Thus, legacy sediments may dampen N removal pathways in buried relict hydric soils, while also acting as substantial sources of NO₃ ^? to waterways.     

Ecotoxicological Risk Assessment of Polychlorinated Biphenyls (PCBs) in Bank Sediments from along the Yamuna River in Delhi,India

The River Yamuna originates from the Yamunotri glacier of the Himalayas and travels 22 km in the Delhi region. The river is used for various purposes in Delhi including drinking water supply. Twenty-eight polychlorinated biphenyls (PCBs) congeners were measured in bank sediments along the river, and their ecotoxicological risk was evaluated. Concentrations of ∑28PCBs varied from 0.20–21.16 ng g^?1 (dry wt.) with mean and median values of 6.63 ng g^?1 and 5.84 ng g^?1 (±0.69 ng g^?1), respectively. The concentration of 12 dl-PCBs concentrations varied from 0.04–2.86 ng g^?1 with a mean of 1.04 ± 0.11 ng g^?1, and their toxic equivalency ranged between <0.01–28.67 pg WHO-TEQ g^?1 with a mean of 10.77 ± 1.06 pg WHO-TEQ g^?1. CB-37, CB-44, CB-114, and CB-118 congeners were dominant among all PCBs congeners. The tri-PCBs (49%) were the main contributors to the PCB homolog followed by tetra-PCBs (35%), and penta-PCB (14%). Because there are no environmental guidelines in India for PCBs in river and marine sediments, concentrations of PCBs and their toxic equivalents were compared in a screening-level assessment with established freshwater sediment quality guidelines and found lower than those guideline values, which suggests no adverse ecotoxicological effect.     

Levels of the fungal allergen Asp f 1 in dust from two sawmills in Croatia: a pilot study

Asp f 1 (ribotoxin) is the main allergen of Aspergillus fumigatus and a critical factor in provoking allergic responses and bronchopulmonary aspergillosis. This study investigated the prevalence of allergen Asp f 1 in dust samples collected at two Croatian sawmills from different working sites (sawmilling, parquetry and sorting). A total of thirty-five floor dust samples were collected, extracted, and the mass fraction of Asp f 1 was determined using a commercially available enzyme-linked immunosorbent assay. More than 91 % of the collected dust samples had detectable levels of Asp f 1 (limit detection 3.6 ng g^?1). The median Asp f 1 mass fractions in Sawmill 1 and Sawmill 2 were 49.4 ng g^?1 (range <3.6–120 ng g^?1) and 35.5 ng g^?1 (range 15.1–77.2 ng g^?1), respectively. At both sawmills, higher median Asp f 1 values were found in the dust from sawmilling than from parquetry sites. These preliminary findings suggest the abundance of allergen Asp f 1 in reservoir dust in the woodworking environments of both sawmills. Assessment of Asp f 1 in future studies will provide further insight into the role of this allergen in eliciting respiratory morbidity.     

PAH contamination in road dust from a moderate city in North China: The significant role of traffic emission

To investigate the contamination level, distribution, possible source, and human exposure risk of polycyclic aromatic hydrocarbons (PAHs) in the urban traffic environment, 15 PAHs were measured in 34 road dust samples (particle size < 25 μm) collected from three grades of roads and park paths in Xinxiang, China. ΣPAHs concentrations ranged from 311 to 21200 ng g^?1, with a mean of 5890 ng g^?1 and decreased in the following order: main roads (7650 ng g^?1) > collector streets (7410 ng g^?1) > bypasses (2970 ng g^?1) > park paths (1570 ng g^?1), indicating that significant positive correlation existed between PAH contamination and traffic density. PAHs in all samples were dominantly composed of 4-ring PAHs, accounting for 44.8% of the total. Pyrene, fluoranthene, and chrysene were the predominant individual components and accounted for 14.7% (1.2–19.2%), 12.9% (3.3–20.3%), and 11.0% (2.5–18.6%) of ΣPAHs, respectively. The specific isomer ratios indicated that traffic emission was the dominant source of PAHs in road dust. The incremental lifetime cancer risk values showed that cancer risk from exposure to road dust–borne PAHs was acceptable for local residents in Xinxiang.     

Concentration,Distribution, Source,and Risk Assessment of PAHs and Heavy Metals in Surface Water from the Three Gorges Reservoir,China

Fifteen polycyclic aromatic hydrocarbons (PAHs) and heavy metals (Cr, Ni, As, Cd, Pb, and Hg) were quantified in 19 surface water sites of the Three Gorges Reservoir, China. The total concentrations of 15 PAHs and six heavy metals in the 19 sample sites ranged from 130.8 ng L^?1 to 227.5 ng L^?1 and 3.2 μg L^?1 to 6.0 μg L^?1, respectively. The mean concentration of As was the highest among the six heavy metals (2.1 ± 0.3 μg L^?1), followed by Cr (0.5 ± 0.3 μg L^?1), Ni (1.3 ± 0.1 μg L^?1), Cd (0.2 ± 0.01 μg L^?1), Pb (0.07 ± 0.08 μ g L^?1) and Hg (0.05 ± 0.08 μg L^?1). The isomer ratio results suggest that PAHs at most sites were mainly from petroleum combustion, while coal and biomass combustion was the main source at sites 1, 2, 6, 7, 9, 14, and 17. Based on principal component analysis, the main source of heavy metals was anthropogenic activities and weathering of bedrocks. Depending on characteristic of RQ_(NCs) ≥ 1 and RQ_(MPCs) < 1, BaA showed higher potential ecological risk than other PAHs, therefore, all sampling site needed to be paid much more attention, included some remedial actions. Meanwhile, after assessing human health risk of heavy metal, it was unlikely to experience adverse health effects, even exposing through more pathways and six kinds of heavy metals simultaneously.     

Sediment microstructure and resuspension behavior depend on each other

The critical shear stress of resuspension and rates of erosion for cohesive and loosely structured sediments must be obtained by direct measurements since there is no theoretical calculation. An in situ experiment on sediment resuspension was performed in a shallow lake (Langer See, NE Germany; area = 1.27 km², z_max = 3.8 m) in summer 2006 using a hydrodynamically calibrated erosion chamber (Ø 20 cm). Shear velocity (u*) was incrementally increased in 11 steps (0–2.19 cm s^?1) to initiate resuspension events. Entrainment rates (E) of suspended particulate matter (E_SPM), total P (E_TP), chlorophyll a (E_Chl a), and soluble reactive P (E_SRP) were determined by mass balance. Two subsequent critical u* (0.53 cm s^?1 and 1.48 cm s^?1) support the ‘two-layered bed’ model of a fluffy surface aggregate layer (freshly deposited phytodetritus prone to resuspension) and an underlying more consolidated biostabilised layer. Patterns in E_SPM (2–106 g m^?2 h^?1), E_TP (11–532 mg m^?2 h^?1), and E_Chl a (3–24 μg m^?2 h^?1) revealed a sediment surface maximum of TP and Chl a and their theoretical vertical logarithmic decrease within 4 mm sediment depth, the maximum thickness of sediment layer entrained. The advective E_SRP flux (17 mg m^?2 h^?1) was 43 times higher than the diffusive SRP flux (0.4 mg m^?2 h^?1). The TP and Chl a micro-profiles suggest that cohesive sediment bed formation is a function of both settling (fluff) and consolidation (biostabilisation). Thus, sediment microstructure and resuspension behavior depend on each other.     

Distribution of Metals (Cu,Zn, Pb,and Cd) in Sediments of the Anzali Lagoon,North Iran

Concentrations of four metals (Cu, Zn, Pb, and Cd) in the sediments of the Anzali Lagoon in the northern part of Iran were determined to evaluate the level of contamination and spatial distribution. The sediments were collected from 21 locations in the lagoon. At each lagoon site a core, 60 cm long, was taken. The ranges of the measured concentrations in the sediments are as follows: 17–140 mg kg^?1 for Cu, 20–113 mg kg^?1 for Zn, 1–37 mg kg^?1 for Pb and 0.1–3.5 mg kg^?1 for Cd in surficial (0-20 cm) and 16–87 mg kg^?1 for Cu, 28.5–118 mg kg^?1 for Zn, 3–20 mg kg^?1 for Pb and 0.1–3.5 mg kg^?1 for Cd in deep (40–60 cm) sediments. The results of the geoaccumulation index (I_geo) show that Cd causes moderate to heavy pollution in most of the study area. Environmental risk evaluation showed that the pollution in the Anzali Lagoon is moderate to considerable and the ranking of the contaminants followed the order: Cd > Cu > Pb > Zn. Some locations present severe pollution by metals depending on the sources, of which sewage outlets and phosphate fertilizers are the main sources of contaminants to the area.     

Dimethylsulphopropionate (DMSP) and proline from the surface of the brown alga Fucus vesiculosus inhibit bacterial attachment

It was demonstrated previously that polar and non-polar surface extracts of the brown alga Fucus vesiculosus collected during winter from the Kiel Bight (Germany) inhibited bacterial attachment at natural concentrations. The present study describes the bioassay-guided identification of the active metabolites from the polar fraction. Chromatographic separation on a size-exclusion liquid chromatography column and bioassays identified an active fraction that was further investigated using nuclear magnetic resonance spectroscopy and mass spectrometry. This fraction contained the metabolites dimethylsulphopropionate (DMSP), proline and alanine. DMSP and proline caused the anti-attachment activity. The metabolites were further quantified on the algal surface together with its associated boundary layer. DMSP and proline were detected in the range 0.12–1.08 ng cm^?2 and 0.09–0.59 ng cm^?2, respectively. These metabolites were tested in the concentration range from 0.1 to 1000 ng cm^?2 against the attachment of five bacterial strains isolated from algae and sediment co-occurring with F. vesiculosus. The surface concentrations for 50% inhibition of attachment of these strains were always <0.38 ng cm^?2 for DMSP and in four cases <0.1 ng cm^?2 for proline, while one strain required 1.66 ng cm^?2 of proline for 50% inhibition. Two further bacterial strains that had been directly isolated from F. vesiculosus were also tested, but proved to be the least sensitive. This study shows that DMSP and proline have an ecologically relevant role as surface inhibitors against bacterial attachment on F. vesiculosus.     

Elucidation of polycyclic aromatic hydrocarbon sources in the sinking particles in Lake Biwa, Japan

We examined monthly changes in polycyclic aromatic hydrocarbons (PAHs) in sediment trap samples collected from the northern basin of Lake Biwa, Japan, from September 2003 to July 2004 to elucidate the sources of PAHs in the lake. The most abundant concentrations were those of pyrene and fluoranthene, at μg g⁻¹ levels throughout the sampling period, with a strong positive relationship (r = 0.996, n = 10, P < 0.01). From the monthly changes in each PAH concentration and their ratios, we suspected two different sources: petroleum sources of lighter PAHs and combustion sources of middle to heavier PAHs. Because pyrene and fluoranthene decreased significantly with time during the sampling period (P < 0.05) and an abnormally high ratio of phenanthrene to anthracene was reported in September 2003, it appears that petroleum was accidentally spilled in September 2003. Although perylene was commonly found at μg g⁻¹ levels in the sediment, its concentration was comparable with those of the other PAHs in sediment trap samples. As perylene showed no significant relationship with other PAHs or other indicator molecules, we suspect that the source of perylene was different from those of other PAHs, and the perylene was mainly formed from its precursors after deposition.