World's largest known Precambrian fossil black smoker chimneys and associated microbial vent communities, North China: Implications for early life

Black smoker chimneys and biological vent communities have been identified at many sites on the deep seafloor, particularly along oceanic spreading centers. We report the largest and oldest known, microbe-rich sub-meter-sized black smoker chimneys and mounds from a 1.43 billion-year old sulfide deposit in a continental graben in northern China. These chimneys are especially well preserved, with characteristic morphology, internal textures and internal cylindrical mineralogical zonation. Four main types of chimneys are distinguished on textural and mineralogical criteria, exhibiting either Zn–Fe-sulfide or Pb–Zn–Fe-sulfide internal cylindrical mineralogical zones. The chimneys mark vent sites in submarine grabens indicating focused flow-venting processes. The fossil chimneys have mineralogical and geological evolutionary features similar to their counterparts on the modern seafloor and other submarine hydrothermal vents. Black smoker vent fluids and seafloor tectonism played important roles for formation of the massive sulfide deposits in the Mesoproterozoic.We also report the first known, remarkably diverse assemblage of fossil microbialites from around and inside Precambrian vent chimneys, demonstrating that Proterozoic life flourished around submarine hot vents and deep within the chimney vent passages. Filamentous, spherical, rod, and coccus-shaped fossil microbes are preserved preferentially on sulfide precipitates. Based on the depth and setting of the fossil biota, the organisms that produced the microbialites were likely sulfate-reducing chemosynthetic and thermophyllic microbes. Textural and mineralogical evidence shows that biomineralization processes enhanced chimney growth and sulfide precipitation.Close association of microorganisms with sulfide chimneys in modern deep-sea hydrothermal vents and younger ophiolites has sparked speculation about whether life may have originated at similar vents. However, little is known about fossil equivalents of vent microfossils and black smoker chimneys from Earth's early evolution. The fossilized microorganisms from the Gaobanhe black smoker chimney sulfide deposits include thread-like filaments with branching and twisted forms and preserved organic carbon, representing fossilized remnants of microbial mats metabolized at high temperatures characteristic of venting fluids. The preservation of fossil microorganisms provides evidence that microbial populations were closely associated with black smoker chimneys in Earth's early history. The microbial population clearly constitutes the site for mediating mineral formation. These ancient microbial fossils lead to a much better understanding of early life on the deep seafloor. The discovery of the Mesoproterozoic microfossils within black-smoker hydrothermal chimneys indicates that hydrothermal activity around sea-floor vents supported dense microbial communities, and supports speculation that vent sites may have hosted the origin of life.     

Deep-sea smokers: windows to a subsurface biosphere?

Since the discovery of hyperthermophilic microbial activity in hydrothermal fluids recovered from "smoker" vents on the East Pacific Rise, the widely accepted upper temperature limit for life (based on pure culture data) has risen from below the boiling point of water at atmospheric pressure to approximately 115 degrees C. Many microbiologists seem willing to speculate that the maximum may be closer to 150 degrees C. We have postulated not only higher temperatures than these (under deep-sea hydrostatic pressures), but also the existence of a biosphere subsurface to accessible seafloor vents. New geochemical information from the Endeavour Segment of the Juan de Fuca Ridge indicative of subsurface organic material caused us to re-examine both the literature on hyperthermophilic microorganisms cultured from deep-sea smoker environments and recent results of microbial sampling efforts at actively discharging smokers on the Endeavour Segment. Here we offer the case for a subsurface biosphere based on an interdisciplinary view of microbial and geochemical analyses of Endeavour smoker fluids, a case in keeping with rapidly evolving geophysical understanding of organic stability under deep-sea hydrothermal conditions.     

Characteristics of alkenone distributions in suspended and sinking particles in the northwestern North Pacific

We investigated alkenones recorded in suspended particles and a settling particle time series collected at three stations, 40N (40°N, 165°E), KNOT (44°N, 155°E), and 50N (50°N, 165°E), in the northwestern North Pacific from December 1997 to May 1999. Emiliania huxleyi, the most abundant alkenone producer in this area, is present in surface to subsurface (to ∼50 m depth) waters. The alkenone concentrations recorded in the suspended particles indicated that the seasonal alkenone particle distribution differed significantly interannually. Alkenone export fluxes at the three sediment-trap stations ranged from 0.16 to 49.3 μg m⁻² day⁻¹, and the maximum export flux, which occurred in summer to fall (July-November), was associated with a high organic carbon export flux. The amount of alkenone produced during the maximum export season accounted for 60-80% of the total annual amount of alkenone, and the alkenones accumulated in the sediment below the traps had characteristics corresponding to subsurface waters during the summer-autumn season. Alkenone-derived temperatures recorded in suspended particles corresponded to the in situ temperature within ∼2 °C. Although alkenone-derived temperatures corresponded approximately to the temperatures observed in the stratified subsurface waters at the three trap stations during the high-export season, large differences were observed during the low-export (winter-spring) period. For example, the alkenone-derived temperatures observed at stations KNOT and 50N were much higher than the in situ subsurface temperatures reported in the World Ocean Atlas 2001. Relatively large differences between alkenone-derived temperatures and in situ temperatures in the subarctic might be due to (1) a low-light limitation or (2) contributions of allochthonous alkenones in particulate material transported from subtropical areas within a warm-core ring.     

Influence of Mussel Culture on the Vertical Export of Phytoplankton Carbon in a Coastal Upwelling Embayment (Ría de Vigo,NW Iberia)

The goal of this paper is to find out whether suspended mussel culture affects the vertical fluxes of biogenic particles in the Ría de Vigo on a seasonal scale. With this aim, vertical fluxes of particulate organic carbon (POC) and the magnitude and composition of vertical export of phytoplankton carbon (Cphyto) collected in sediment traps were examined by comparing data obtained inside a mussel farming area (RaS) with those found at a reference station (ReS) not affected by mussels. Our results indicate that mussel farming has a strong impact on sedimentation fluxes under the rafts, not only increasing POC flux but also altering the magnitude and composition of Cphyto fluxes. Average POC flux at RaS (2564?±?1936 mg m^?2 day^?1) was four times higher than at ReS (731?±?276 mg m^?2 day^?1), and much of this increase was due to biodeposit fluxes (Cbiodep) which accounted for large proportion of POC flux (35–60 %). Indeed, because of this high Cbiodep flux, only a small proportion of the POC flux was due to Cphyto flux (3–12 %). At the same time, we observed an increased sedimentation of phytoplankton cells at RaS that could be explained by a combination of mechanisms: less energetic hydrodynamic conditions under mussel rafts, ballast effect by sinking mussel feces, and diatom aggregates. Moreover, mussel farming also altered the quality of the Cphyto flux by removing part of the predatory pressure of zooplankton and thus matching diatom composition in water column and sediment traps.     

相-势-源复合控油气成藏机制物理模拟实验研究*

含油气盆地的地质相、流体势、烃源灶是影响圈闭含油气性的决定性因素, 三者缺一不可。在各要素满足控藏临界条件下, 优相-低势-近源复合指数(FPSI) 越高, 圈闭含油气性越好。基于相-势-源复合控油气成藏机制开展物理模拟实验研究, 结果表明:“源”控制着油气成藏的物质来源, “相”控制着油气成藏的孔隙空间、“势”控制着油气成藏的运移动力, 当三者联合作用时能够形成油气藏。实验结果还表明, 圈闭外部(盖层)岩相和圈闭内部(储集层)岩相粒径差别越大, 越有利于油气在毛细管力作用下从细粒低孔渗的围岩之中进入到粗粒高孔渗的储集层之内聚集成藏, 临界条件是：圈闭外部围岩颗粒粒径较圈闭内部储集层颗粒粒径小2倍以上, 或外部毛细管力较之内部大2倍以上, 也即外部界面势能较内部高2倍以上;圈闭外部烃源岩含油气饱和度越高, 越有利油气进入圈闭内部储集层中聚集成藏, 临界条件是外部源岩的含油气饱和度达到和超过5％。     

http://www.sciencedirect.com/science/article/pii/S1674987113001114

The Deccan Syneclise is considered to have significant hydrocarbon potential.However,significant hydrocarbon discoveries,particularly for Mesozoic sequences,have not been established through conventional exploration due to the thick basalt cover over Mesozoic sedimentary rocks.In this study,near-surface geochemical data are used to understand the petroleum system and also investigate type of source for hydrocarbons generation of the study area.Soil samples were collected from favorable areas identified by integrated geophysical studies.The compositional and isotopic signatures of adsorbed gaseous hydrocarbons(methane through butane) were used as surface indicators of petroleum micro-seepages.An analysis of 75 near-surface soil-gas samples was carried out for light hydrocarbons(C1-C4) and their carbon isotopes from the western part of Tapti graben,Deccan Syneclise,India.The geochemical results reveal sites or clusters of sites containing anomalously high concentrations of light hydrocarbon gases.High concentrations of adsorbed thermogenic methane(C_1 = 518 ppb) and ethane plus higher hydrocarbons(ΣC_(2+) = 977 ppb) were observed.Statistical analysis shows that samples from 13% of the samples contain anomalously high concentrations of light hydrocarbons in the soil-gas constituents.This seepage suggests largest magnitude of soil gas anomalies might be generated/source from Mesozoic sedimentary rocks,beneath Deccan Traps.The carbon isotopic composition of methane,ethane and propane ranges are from-22.5‰ to-30.2‰ PDB,-18.0‰to 27.1‰ PDB and 16.9‰-32.1‰ PDB respectively,which are in thermogenic source.Surface soil sample represents the intersection of a migration conduit from the deep subsurface to the surface connected to sub-trappean Mesozoic sedimentary rocks.Prominent hydrocarbon concentrations were associated with dykes,lineaments and presented on thinner basaltic cover in the study area,which probably acts as channel for the micro-seepage of hydrocarbons.     

Holocene Methane Emissions in the Southwestern Sea of Okhotsk: Evidence from Carbon Isotopes in Benthic Foraminifera Shells

Doklady Earth Sciences - Several negative stable carbon isotope excursions are revealed in benthic foraminifera from the LV50-05 gas-bearing core collected from an area of active methane venting on...     

Lipid composition of the pelagic crab Pleuroncodes planipes, its feces, and sinking particulate organic matter in the Equatorial North Pacific Ocean

Fecal pellets from the pelagic crab Pleuroncodes planipes were a substantial portion of the particulate organic matter in a sediment trap deployed at the bottom of the mixed layer in the eastern tropical North Pacific Ocean. The lipids of fresh P. planipes feces were compared to lipids of the sediment trap material, of mixed zooplankton which may comprise part of the diet of the crab, and of the crab itself in order to elucidate the source of organic compounds found in the trap. Hydrocarbons, wax esters, triacylglycerols, steroidal alcohols, steroidal ketones, and fatty acids were determined by capillary gas chromatography and gas chromatography/mass spectrometry. Significant input of lipids via sedimentation of crab fecal material is indicated, and modification of dietary lipid within the gut of the crab is inferred. Labile dietary fatty acids are depleted and sterols enriched in the fecal pellets and trap material relative to the zooplankton and crab. Nuclear saturated and unsaturated 3-ketosteroids and unsaturated steroidal hydrocarbons were detected in the crab, its feces, and in the sediment trap particulate material.     

Sedimentary geochemistry of hydrothermal vents in Guaymas Basin,Gulf of California,Mexico

Surface sediments from 4 contrasting environmental settings in the Southern Trough of Guaymas Basin were analysed to determine their texture, total organic matter (TOM), P (TP), and N (TN) content as well as the spatial variation in their C:N:P atomic ratios in hydrothermally altered sediments. Particle size analysis revealed a marked spatial heterogeneity among sites. Cores taken at Beggiatoa bacterial mats and at clam fields contained significant silt and clay content, while those obtained near venting sites had sand and gravel as the main components because no fine sedimentary materials are deposited at these sites. Fine grain sediments were common farther away from vents. High levels of organic C (3.4 to 12.4%) were recorded in the upper 8 cm but no clear trends of decreasing TOC with depth were noted. The presence of hydrothermally generated petroleum in some cores increased the organic C content between 8 and 12 cm. TN was generally high (456.3–4356 μg/g) and sustained a significant correlation with TOM (r=0.834, P<0.005). TP is essentially of lithogenic origin and reached concentrations greater than those normally reported in productive coastal areas (1165 μg/g) in the Gulf of California. A marked increase with depth was noted for this parameter. High C:N:P atomic ratios were estimated. These had vertical and horizontal gradients decreasing in the upper 4 cm, and then slightly increasing in intermediate strata. Organic matter enrichment at venting sites results in high C:N:P ratios (2130:25:1–2692:57:1) which are 5-fold greater than the values estimated at sedimentary environments where Beggiatoa or vesicomyd clams are predominant.     

Chemical evidence of differential particle dispersal in the southern washington coastal environment

Aliphatic hydrocarbons, cupric oxide oxidation products of lignin and polycyclic aromatic hydrocarbons (PAH) were analyzed by capillary gas chromatography in sediments from the southern Washington continental shelf and slope. The concentration of diploptene relative to plantwax $\text{n-}\text{alkanes}$ increased systematically in surface sediments with distance offshore along east-west transects of the study area and remained constant in surface sediments along the midshelf silt deposit. Analogous trends were also observed for the concentration of cinnamyl phenols relative to vanillyl phenols and total methylphenanthrenes relative to phenanthrene. These changes in sedimentary composition are evidence that diploptene from some terrestrial source, lignin characteristic of non-woody vascular plant tissue and a fossil organic material contained within weathered rock debris disperse across the Washington continental shelf and slope in geographic patterns distinct from that for other river-derived, chemically related materials. The compositional variations are explained by the particulate associations of the land-derived chemicals and differential hydraulic dispersion of their respective carrier particles after discharge at the mouth of the Columbia River.     

Geochemistry of fluid phases and sediments: relevance to hydrothermal circulation in Middle Valley,ODP Legs 139 and 169

Geochemical and isotopic studies of pore fluids and solid phases recovered from the Dead Dog and Bent Hill hydrothermal sites in Middle Valley (Ocean Drilling Program Leg 169) have been compared with similar data obtained previously from these sites during Ocean Drilling Program Leg 139. Although generally the hydrothermal systems reflect non-steady state conditions, the data allow an assessment of the history of the hydrothermal processes. Sediment K/Al ratios as well as the distribution of anhydrite in the sediments suggest that the Dead Dog hydrothermal field has been, and still is, active. In contrast, similar data in the Bent Hill hydrothermal field indicate a waning of hydrothermal activity. Pore fluid and hydrothermal vent data in the Dead Dog hydrothermal field are similar in nature to the data collected during ODP Leg 139. In the area of the Bent Hill sulfide deposit, however, the pore water data indicate that recent wholesale flushing of the sediment column with relatively unaltered seawater has obliterated a previous record of hydrothermal activity in the pore fluids. Data from the deepest part of Hole 1035A in the Bent Hill locality show the presence of hydrothermal fluids at greater depths in this area. This suggests the origin of the hydrothermal fluids found to be emanating from Hole 1035F, which constitutes one of the first man made hydrothermal vents in the Middle Valley hydrothermal system. Similarly, CORKed Hole 858G, because of seal failures, has acted as a hydrothermal vent, with sulfide deposits forming inside the CORK.     

Geochemistry of suspended matter and sinking material in the eastern Norwegian Sea

This paper reports the results of a geochemical study of suspended particulate matter and particle fluxes in the Norwegian Sea above the Bear Island slope. The concentrations of suspended particles and the main components of suspended matter were determined in the euphotic, intermediate (“clean water”), and bottom nepheloid layers. It was shown that biogenic components are predominant in the water above the nepheloid layer, whereas the suspended matter of the nepheloid layer is formed by the resuspension of the lithogenic components of bottom sediments. The chemical compositions of suspended matter and material collected in sediment traps are identical.     

Velocity and Structural Modeling of Mesozoic Chiltan Limestone and Goru Formation for Hydrocarbon Evaluation in the Bitrisim Area, Lower Indus Basin, Pakistan

The present study focuses on building a workflow for structural interpretation and velocity modeling and implementing to Jurassic-Cretaceous succession (Chiltan Limestone and Massive sand of the Lower Goru Formation). 2D-Migrated seismic sections of the area are used as data set and in order to confirm the presence of hydrocarbons in the study area, P and S-wave seismic velocities are estimated from single-component seismic data. Some specific issues in the use of seismic data for modeling and hydrocarbon evaluation need to deal with including distinguishing the reservoir and cap rocks, and the effects of faults, folds and presence of hydrocarbons on these rocks. This study has carried out the structural interpretation and modeling of the seismic data for the identification of traps. The results demonstrate existence of appropriate structural traps in the form of horst and grabens in the area. 2D and 3D velocity modeling of the horizons indicates the presence of high velocity zones in the eastern half of the study while relatively low velocity zones are encountered in the western half of the area. Two wells were drilled in the study area (i.e. Fateh-01 and Ichhri-01) and both are dry. Immature hydrocarbons migration is considered as a failure reason for Fateh-01 and Ichhri-01 well.     

Separation of He and CH4 signals on the Mid-Atlantic Ridge at 5°N and 51°N

Abiogenic methane may be produced in submarine hydrothermal systems by degassing of basalts or serpentinization of ultramafic outcrops. The latter process presumably releases little primordial helium and is therefore implicated by high CH₄/³He ratios in vent fluids from the ultramafic-hosted Rainbow field and in methane plumes near ultramafic outcrops. In two segments of the Mid-Atlantic Ridge, at 5.4°N and 51°N, we have observed depth-separated CH₄ and ³He plumes. In both cases, the helium plume was deeper, near the valley floor. It may be that the plumes issue from separate vents, where the helium is discharged near the volcanic axis and the methane is generated by serpentinization on the valley wall. However, at the present time the locations of the vents that produce these plumes are not known. Using a one-pass model, we investigated whether separate venting could arise from heat conduction from a primary, helium-carrying, hydrothermal circulation to a second, shallower fracture loop intersecting ultramafic rock. The model results indicate that the flow rate through the secondary loop would have to be relatively low in order for it to stay warm enough for serpentinization to proceed. In this case, some of the exothermic heat production is lost by conduction, and the temperature increase in the circulating fluid is only a fraction of that expected from a water/rock ratio of 1:1.     

Factors affecting pore water hydrocarbon concentrations in Puget Sound sediments

Polycyclic aromatic hydrocarbon (PAH) and aliphatic hydrocarbon concentrations have been determined for sediments and associated pore waters collected at 2 sites (11 stations) in Puget Sound, Washington (northwest U.S.A.). These sediments have been contaminated to varying degrees by hydrocarbons from a creosote plant and from various combustion sources. PAH were not detected in pore waters of sediments whose PAH were primarily derived from combustion and natural sources, even though pore water concentrations predicted from sediment concentrations and two-phase equilibrium partitioning models were above detection limits from most PAH. Equilibrium partition coefficients calculated from field aqueous and solid phase data from an area contaminated with creosote agreed with laboratory-derived coefficients to within a factor of ± 4. Pore water concentrations of creosote-derived aliphatic hydrocarbons increase with increasing concentration in bulk sediments. However, pore water concentrations of natural and contaminant aliphatic hydrocarbons are much higher than predicted by solubility data, possibly due to association with nonfilterable dissolved organic matter and colloids. Other major factors controlling hydrocarbon pore water concentrations include differential hydrocarbon sources, specific particle associations and solubility.     

Effects of mesoscale physical processes on thin zooplankton layers at four sites along the west coast of the U.S.

Within the coastal marine environment, populations of phytoplankton, zooplankton, bacteria, viruses, and aggregations of marine snow are frequently concentrated beneath the surface in discrete, vertically thin layers. Thin layers range in vertical dimension from a few centimeters to three meters, and have been observed to extend horizontally for kilometers. They appear in the water column episodically and can persist for days. We present some of the results of an investigation of four coastal sites along the west coast of the United States to assess frequency of occurrence of thin layers of zooplankton. Our study sites included coastal sites near East Sound, Washington; Cape Perpetua, Oregon; Monterey Bay, California; and Santa Barbara, California. At each site, we collected several, weeks-long time series of hydrography, current velocity, and acoustic backscatter due to mesozooplankton. Our results show that thin layers were common features at all four sites. Across all study sites, a change in the predominant physical regime, usually precipitated by a change in the wind pattern, corresponded with an absence of thin Zooplankton layers. In order to make a first-order prediction about when thin layers have the possibility of occurring in a coastal environment, we found it useful to examine regional wind and circulation patterns and to determine how they affect stratification in each local environment.     

Geochemistry of low-molecular weight hydrocarbons in hydrothermal fluids from Middle Valley, northern Juan de Fuca Ridge

Hydrothermal vent fluids from Middle Valley, a sediment-covered vent field located on the northern Juan de Fuca Ridge, were sampled in July, 2000. Eight different vents with exit temperatures of 186-281 °C were sampled from two areas of venting: the Dead Dog and ODP Mound fields. Fluids from the Dead Dog field are characterized by higher concentrations of ΣNH₃ and organic compounds (C₁-C₄ alkanes, ethene, propene, benzene and toluene) compared with fluids from the ODP Mound field. The ODP Mound fluids, however, are characterized by higher C₁/(C₂ + C₃) and benzene:toluene ratios than those from the Dead Dog field. The aqueous organic compounds in these fluids have been derived from both bacterial processes (methanogenesis in low temperature regions during recharge) as well as from thermogenic processes in higher temperature portions of the subsurface reaction zone. As the sediments undergo hydrothermal alteration, carbon dioxide and hydrocarbons are released to solution as organic matter degrades via a stepwise oxidation process. Compositional and isotopic differences in the aqueous hydrocarbons indicate that maximum subsurface temperatures at the ODP Mound are greater than those at the Dead Dog field. Maximum subsurface temperatures were calculated assuming that thermodynamic equilibrium is attained between alkenes and alkanes, benzene and toluene, and carbon dioxide and methane. The calculated temperatures for alkene-alkane equilibrium are consistent with differences in the dissolved Cl concentrations in fluids from the two fields, and confirm that subsurface temperatures at the ODP Mound are hotter than those at the Dead Dog field. Temperatures calculated assuming benzene-toluene equilibrium and carbon dioxide-methane equilibrium are similar to observed exit temperatures, and do not record the hottest subsurface conditions. The difference in subsurface temperatures estimated using organic geochemical thermometers reflects subsurface cooling processes via mixing of a hot, low salinity vapor with a cooler, seawater salinity fluid. Because of the disparate temperature dependence of alkene-alkane and benzene-toluene equilibria, the mixed fluid records both the high and low temperature equilibrium conditions. These calculations indicate that vapor-rich fluids are presently being formed in the crust beneath the ODP Mound, yet do not reach the surface due to mixing with the lower temperature fluids.     

Mineralization of organic material and bacterial dynamics in Mississippi River plume water

Net remineralization rates of organic matter and bacterial growth rates were observed in dark-bottle incubation experiments conducted in July–August and February with water samples collected from sites in the Mississippi River plume of the Gulf of Mexico. Our objectives were to measure site-specific degradation rates of labile dissolved and particulate organic matter, quantify the potential importance of bacteria in these processes, and examine the kinetics of degradation over time. Unfiltered samples, and samples treated to remove (or dilute out) particles larger than bacteria, were enclosed in 9-1 bottles and incubated in the dark for 3–5 d. Respiration rates and inorganic compound accumulation rates were higher in summer than in winter and were highest in unfiltered surface samples at sites of intermediate salinities where phytoplankton were most abundant. The ratio of ammonium accumulation to oxygen removal in summer experiments suggested that the mineralized organic material resembled “Redfield” stoichiometry. Chemical fluxes were greater in bottles containing large (>1–3 μm) particles than in the bottles with these particles removed, but bacterial activities were generally similar in both treatments. These results suggest that particle consumers were an important component of total organic matter degradation. However, these experiments may have underestimated natural bacterial degradation rates because the absence of light could affect the production of labile organic substrates by phytoplankton. In agreement, with this hypothesis, bacterial growth rates tended to decrease over time in summer in surface plume waters where phytoplankton were abundant. In conjunction with other data, our results indicate that heterotrophic processes in the water column are spatially and temporally dependent on phytoplankton production.     

Suspended material in Narragansett Bay: fatty acid and hydrocarbon composition

Suspended material collected at various stations in Narragansett Bay was analyzed for fatty acids and hydrocarbons. The qualitative and quantitative distributions of these compounds indicated that the influence of sewage and other pollutants was greatest in the river areas. Based on concentrations of polyunsaturated fatty acids, the highest densities of phytoplankton were interpreted to occur at the mid and lower Bay stations, and the percentage of phytoplankton in suspended material was estimated from the concentration of heneicosahexaene. The concentrations of fatty acids and hydrocarbons in the suspended material decreased from the river stations to the mid and lower Bay stations, closely following a similar trend observed in the sediment. Possible sources of the suspended material and the influence of these sources on this material in various areas of the Bay are discussed, and attempts are made to interrelate the suspended material, resuspended sediment, phytoplankton, and sewage effluent with chemical and biochemical diagenetic changes.     

Particle associated polycyclic aromatic hydrocarbons in the atmospheric environment of urban and suburban residential area

Ten polycyclic aromatic hydrocarbons associated with suspended particulate matter in the ambient air were collected at two sampling sites: urban and suburban residential areas of Yokohama, Japan from 1999 to 2005. The concentrations of target compounds were determined using gas chromatography-mass spectrometry. The total concentrations were higher in urban residential area than suburban residential area. They ranged from 0.31 to 6.16 ng/m3 withameanof2.07ng/m3 and 0.33 to2.87ng/m3 with a mean of 1.02 ng/m3 in the urban and suburban residential areas, respectively. The predominant compounds determined both in the urban and suburban residential areas were benzo[b]fluoranthene, benzo[ghi]perylene, indeno[1,2,3-cd]pyrene and benzo[e]pyrene. The concentrations of 5- and 6-ring polycyclic aromatic hydrocarbons were higher in the urban than the suburban residential area, accounting for 77.3 % and 72.1 % of total polycyclic aromatic hydrocarbons, respectively. Source identification was performed by principal component analysis. Two principal components were identified for each study area and these accounted for 95.9 % and 83.3 % of total variance, respectively. The results revealed that stationary source and vehicle emissions were the major pollution sources in the studied areas. The impact of emission regulations for automobiles in large Japanese cities, which were enacted during 2002 and 2003, was also studied. Based on the average total concentration, emission reduction was 47.8 % and 18.6 % in urban residential and suburban residential areas, respectively.