Tidal river sediments in the Washington,D.C. area. II. Distribution and sources of organic contaminants     

Terry L. Wade  David J. Velinsky  Eli Reinharz  Christian E. Schlekat 《Estuaries and Coasts》1994,17(2):321-333

Concentration of aliphatic, aromatic, and chlorinated hydrocarbons were determined from 33 surface-sediment samples taken from the Tidal Basin, Washington Ship Channel, and the Anacostia and Potomac rivers in Washington, D.C. In conjunction with these samples, selected storm sewers and outfalls also were sampled to help elucidate general sources of contamination to the area. All of the sediments contained detectable concentrations of aliphatic and aromatic hydrocarbons, DDT (total dichlorodiphenyltrichloroethane), DDE (dichlorodiphenyldichloroethene), DDD (dichlorodiphenyldichloroethane), PCBs (total polychlorinated biphenyls) and total chlordanes (oxy-, α-, and γ-chlordane and cis + trans-nonachlor). Sediment concentrations of most contaminants were highest in the Anacostia River just downstream of the Washington Navy Yard, except for total chlordane, which appeared to have upstream sources in addition to storm and combined sewer runoff. This area has the highest number of storm and combined sewer outfalls in the river. Potomac River stations had lower concentrations than other stations. Total hydrocarbons (THC), normalized to the fine-grain fraction (clay + silt, < 63 μm), ranged from 120 μg g^?1 to, 1,900 μg g^?1 fine-grain sediment. The hydrocarbons were dominated by the unresolved complex mixture (UCM), with total polycyclic aromatic hydrocarbons (PAHs) concentrations ranging from 4 μg g^?1 to 33 μg g^?1 fine-grain sediment. Alkyl-substituted compounds (e.g., C1 to C4 methyl groups) of naphthalene, fluorene, phenanthrere + anthracene, and chrysene series dominated the polycyclic aromatic hydrocarbons (PAHs). Polycyclic aromatic hydrocarbons, saturated hydrocarbons, and the unresolved complex mixture (UCM) distributions reflect mixtures of combustion products (i.e., pyrogenic sources) and direct discharges of petroleum products. Total PCB concentrations ranged from 0.075 μg g^?1 to 2.6 μg g^?1 fine-grain sediment, with highest concentrations in the Anacostia River. Four to six C1-substituted biphenyls were the most-prevalent PCBs. Variability in the PCB distribution was observed in different sampling areas, reflecting, differing proportion of Arochlor inputs and degradation. The concentration of all contaminants was generally higher in sediments closer to known sewer outfalls, with concentrations of total hydrocarbon, PAHs, and PCBs as high as 6,900 μg g^?1, 620 μg g^?1, and 20 μg g^?1 fine-grain sediment, respectively. Highest PCB concentrations were found in two outfalls that drain into the Tidal Basin. Concentrations of organic contaminants from sewers draining to the Washington Ship Channel and Anacostia River had higher concentrations than sediments of the mid-channel or river. Sources of PCBs appear to be related to specific outfalls, while hydrocarbon inputs, especially PAHs, are diffuse, and may be related to street runoff. Whereas most point-source contaninant inputs have been regulated, the importance of nonpoint source inputs must be assessed for their potential addition of contaminants to aquatic ecosystems. This study indicates that in large urban areas, nonpoint sources deliver substantial amounts of contaminants to ecosystems through storm and combined sewer systems, and control of these inputs must be addressed.  相似文献   

Bivariate conditional sampling of buoyancy flux during an intense cold-air outbreak   总被引：1，自引：0，他引：1  

Shu-Hsien Chou  Jeffrey Zimmerman 《Boundary-Layer Meteorology》1989,46(1-2):93-112

Buoyancy fluxes in the marine atmospheric boundary layer (MABL) for the cloud street regime, observed during the Genesis of Atlantic Lows Experiment (GALE), have been analyzed using the technique of joint frequency distribution. For the lower half of the MABL, the results suggest that the buoyancy flux is mainly generated by the rising thermals and the sinking compensating ambient air, and is mainly consumed by the entrainment and detrainment of thermals, penetrative convection, and the entrainment from the MABL top.The results are compared to those from previous studies of mesoscale cellular convection (Air-Mass Transformation Experiment, AMTEX), the dry convective boundary layer, and the trade-wind MABL. For the lower MABL, the quadrant buoyancy fluxes, fractional coverages, and flux intensities are in good agreement with those of mesoscale cellular convection (AMTEX) and the dry convective boundary layer. The results suggest that, if the buoyancy flux is primarily driven by the temperature flux, the physical processes for generating buoyancy flux mentioned above are about the same for the lower boundary layers over land and ocean, even with different convective regimes. For the trade-wind MABL, the buoyancy flux is mainly driven by the moisture flux; the quadrant flux intensities are stronger than those of the other three studies except for the buoyant updrafts (thermals). These results suggest that the entrainment and detrainment of thermals are more effective in the trade-wind MABL than in the boundary layers driven by the temperature flux.Scale analysis of the buoyancy flux is in good agreement with that of AMTEX. For the lower half of the MABL, the buoyancy flux is mainly generated by the intermediate scale (200 m to 2 km), which includes the dominant convective thermals in the surface layer and the mixed layer. The scale smaller than 200 m is important only in the surface layer. The scale larger than 2 km, which includes the roll vortices, increases its significance upward. While most of the positive and negative fluxes are associated with the updrafts for the intermediate scale, the downdrafts are as important as updrafts for the larger scale.ST Systems Corporation, Lanham, MD, 20706, U.S.A.  相似文献   

Natural concentrations of mercury in Iceland     

Jeffrey A. Coderre  Sigurdur Steinthórsson 《Geochimica et cosmochimica acta》1977,41(3):419-424

The results are presented of a survey of mercury concentrations in various parts of the Icelandic environment. Values for air and gas samples include: <0.03 μg/m³ for Reykjavík, 15–20 km away from a hydrothermal area; 1–3 μg/m³ for air in a hydrothermal area near Lake Mývatn; 12–30 μg/m³ for air in Heimaey during the 1973 eruption; and 16 μg/m³ for a sample of fumarole gas. Values for fresh igneous rocks, of various compositions, extrusive (subaerial), subaqueous (up to 3000 m depth), and intrusive, range between 2 and 9 ppb. Highest values obtained for uncontaminated samples are 37 ppb for a pyrite-bearing zone in a hydrothermal drill hole, and 125 ppb for a volcanic sublimate. The sources of the mercury levels observed are briefly discussed.  相似文献   

Petrology and chemistry of two “large” granite clasts from the moon     

Paul H. Warren  G. Jeffrey Taylor  Klaus Keil  David N. Shirley  John T. Wasson 《Earth and Planetary Science Letters》1983,64(2):175-185

Pristine granite clasts in Apollo-14 breccias 14321 and 14303 have estimated masses of 1.8 and 0.17 g, respectively. The 14321 clast is ～ 60% K-feldspar and 40% quartz, with traces of extremely Mg-poor mafic silicates and ilmenite. The 14303 clast is roughly 33% plagioclase, 32% K-feldspar, 23% quartz, 11% pyroxene, and 1% ilmenite; pyroxene and ilmenite are moderately Mg-rich; plagioclase and pyroxene are strongly zoned. Both clasts are severely brecciated, but monomict (pristine). Both have abundant graphic intergrowths of K-feldspar with quartz. Unlike the majority of similar Earth rocks, both clasts are devoid of hydrous phases. The bulk composition of the 14321 clast is similar to those of several other lunar granitic samples, but the 14303 clast is unique: it bears as close a resemblance to KREEP as it does to other lunar granites. Silicate liquid immiscibility may explain why the granites are low in REE relative to KREEP.  相似文献   

The opening of the Woodlark Basin, subduction of the Woodlark spreading system, and the evolution of Northern Melanesia since mid-pliocene time   总被引：1，自引：0，他引：1  

Jeffrey K. Weissel  Brian Taylor  Garry D. Karner 《Tectonophysics》1982,87(1-4)

Magnetic anomaly and seismological data define segments of active seafloor spreading and associated magnetic lineations trending ENE in the Woodlark Basin. The total opening rate has been approximately 6 cm/yr for the last 1 m.y. Spreading rates diminish by over 10% from east to west along the Woodlark spreading system implying a pole of current opening 15°–20° to the west. Commencement of seafloor spreading in the basin has apparently been time-transgressive, beginning prior to 3.5 m.y. in the east, and at successively later times to the west. Earthquake focal mechanisms and geological evidence suggest that the land areas bounding the western end of the Woodlark Basin are undergoing tensional deformation. We believe that eventually the Woodlark Basin plate boundary will propagate westward through the d'Entrecasteaux Islands into the Papuan peninsula. Hitherto unreported shallow seismicity associated with the northern margin of the NE-trending section of the Woodlark Rise probably reflects partial decoupling of the Woodlark and Solomon basins, possibly due to mechanical difficulties in subducting the young Woodlark lithosphere.Analysis of the relative motions between the Solomon, Indo-Australian, and Pacific plates shows that the Woodlark spreading system has been subducted at high rates (> 10 cm/yr) beneath the Solomon Islands during the opening of the Woodlark Basin. Several tectonic and geological features limited to the region of interaction of the Woodlark Basin with the Solomon Trench and arc may be symptomatic of ridge subduction. These features include high heat flow in the Solomon Trench, which shoals to 4 km; low levels of seismicity and only shallow hypocenters; and voluminous eruptions of high olivine basalts and basaltic andesites extremely close to the trench axis. This close association in space and time of an unusual volcanic suite with ridge subduction implies a strong dependence of the petrogenesis on the tectonic regime.A combination of this study of the Woodlark Basin and the previous study of the Bismarck Basin (Taylor, 1979) provides a reconstruction of the positions of the continents, ocean basins, and island chains in northern Melanesia for mid-Pliocene time. In accepting the existence of a Solomon plate, we can explain the trench-like structure off the Trobriand margin of New Guinea, the occurrence of Late Cenozoic calc-alkaline volcanism along the Papuan peninsula, and the presence of intermediate depth seismicity beneath the north Papuan peninsula. The rapid changes in relative motions along or across the New Ireland-Solomons chain over the past 3.5 m.y. may explain the spatial and temporal changes in igneous activity observed on these islands.  相似文献   

Pressures and temperatures in Precambrian metamorphic rocks     

Jeffrey A. Grambling 《Earth and Planetary Science Letters》1981,53(1):63-68

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Low molecular weight α-hydroxy carboxylic and dicarboxylic acids in reducing marine sediments     

Edward T. Peltzer  Jeffrey L. Bada 《Geochimica et cosmochimica acta》1981,45(10):1847-1854

The occurrence and distribution of low molecular weight α-hydroxy carboxylic and dicarboxylic acids was studied in reducing marine sediments collected in the Santa Barbara Basin and the Cariaco Trench. Four compounds were found to occur in both basin sediments: glycolic, lactic, oxalic and succinic acids. In general concentrations were low (? 1 μmol/g for the hydroxy acids and ? 100μmol/g for the dicarboxylic acids), and generally decreased with depth. Subsurface maxima were observed for lactate and succinate in the Santa Barbara Basin. Both the vertical profiles and lactate enantiomer ratios suggested microbial origin and control for the distribution of these compounds. A preliminary model for the microbial mediation of the early diagenesis of organic compounds in reducing marine sediments is presented.  相似文献   

Combined amino acids in Pacific Ocean waters     

Jeffrey L. Bada  Edward Hoopes  Ming-shan Ho 《Earth and Planetary Science Letters》1982,58(2):276-284

Filtration and extraction indicate that the bulk of the combined amino acids in Pacific Ocean waters are a constituent of a dissolved component, and that they cannot be efficiently extracted from seawater by the macroreticular XAD-2 resin. In deep waters of the Pacific Ocean, alanine accounts for～60–70% of the combined amino acids, while in surface waters alanine makes up only～30% of the combined amino acid fraction. Serine is present in the combined fraction in surface waters, but is essentially absent in deep waters. These differences in the serine and alanine abundances between surface and deep waters are possibly the result of the dehydration of serine, which produces racemic alanine. Threonine can also undergo dehydration producing racemicα-amino-n-butyric acid, a non-biological amino acid which has been detected in deep waters of the Pacific Ocean. Estimates of the rate of serine and threonine dehydration in the oceans suggest that these reactions may have half-lives at 0°C of less than 100 years. As a consequence of dehydration, the dissolved organic material in which this diagenetic reaction has occurred may have reduced biological degradability.  相似文献   

Soviets fine poachers     

Terry L. Wade  James G. Quinn 《Marine pollution bulletin》1975,6(4):54-57

Small particles of weathered pelagic tar are suggested as a major source of hydrocarbons found in surface microlayer and subsurface water samples collected in the Sargasso Sea.  相似文献   

Breakup between Australia and Antarctica: A brief review in the light of new data     

John C. Mutter  Kerry A. Hegarty  Steven C. Cande  Jeffrey K. Weissel 《Tectonophysics》1985,114(1-4)

The arguments justifying the revised timing of breakup between Australia and Antarctica (Cande and Mutter, 1982) and the reconstruction of Broken Ridge and Kerguelen Plateau (Mutter and Cande, 1983) are reviewed and considered with respect to new subsidence data. The age of breakup was revised from anomaly 22 time (55 My B.P.) to anomaly 34 time (85 My B.P.). The rough topography of the Diamantina Zone can be attributed to very slow spreading (−5 mm/yr.) beginning between the times of anomaly 34 and anomaly 19. The reconstruction of Broken Ridge and Kerguelen Plateau at anomaly 34 time shows overlap of these two features, but the overlap problem is nearly resolved by anomaly 18 time ( ~ 42 My B.P.). Normal seafloor spreading rates (22 mm/yr.) commenced at anomaly 19 time ( ~ 43 My B.P.). Subsidence patterns calculated from biostratigraphic data from wells drilled along Australia's southern margin are interpreted as more consistent with the revised age of Australia-Antarctic breakup. Subsidence curves systematically show rapid subsidence associated with the rift phase of margin development followed by much slower thermally-controlled subsidence during the drift phase. The timing of the rift-to-drift transition is believed to coincide with the age of breakup ( ~ 60 to 110 My B.P.). In addition, the subsidence curves indicate a west-to-east propagation of breakup along the southern margin. Magnetic anomaly patterns and stratigraphie observations are consistent with this hypothesis.  相似文献