DIFFERENCES IN PAH DESORPTION AND SEDIMENT ORGANIC MATTER COMPOSITION BETWEEN NON-VEGETATED AND RECENTLY VEGETATED FUEL-OILED SEDIMENTS

We assessed the desorption behavior of pyrene, chrysene, phenanthrene, and tri-alkylated (C₃) phenanthrene/anthracenes for non-vegetated and recently vegetated (< 2 yrs) fuel-oiled sediments collected from the Indiana Harbor Canal (IHC), Gary, IN. Bulk sediment and humin were analyzed for PAH concentrations, organic matter composition, and PAH desorption behavior. PAH desorption isotherms and kinetics were determined using batch aqueous extractions and a two compartment, first-order kinetic model. Vegetated sediments contained more plant carbon and were more nonpolar and less oxidized than non-vegetated sediments. Desorption kinetics indicated that PAH desorption was primarily controlled by a slow PAH-desorbing fraction (F₂) of IHC sediments. However, in vegetated sediments, particularly humin, PAH release from a faster PAH-desorbing fraction (F₁) increased as did the rates (k₂) of PAH desorption from the dominant slow PAH-desorbing fraction (F₂). We propose that vegetation provides aliphatic, nonpolar carbon to IHC sediments that facilitates more rapid PAH desorption from bulk sediment and humin.     

Lake sediments as recorders of geomagnetic field variations — applications to dating post-Glacial sediments

Field and laboratory methods, developed to recover the record of past secular variations of geomagnetic declination and inclination carried by the remanent magnetization of some lake sediments, are described. Type curves, delineating these parameters through post-Glacial time, have now been constructed for Europe and east-central N. America. These curves, once established for any region, are useful for dating lake sediments from that region. The principal inclination features exhibited by the European curves can also be identified along the N. American curves with a delay of some 600 years, on average.     

Recent patterns of sediment accumulation in a small closed eutrophic lake revealed by the sediment records

A short-core palaeolimnological investigation was undertaken with the aim ofacquiring knowledge of sediment deposition. Analyses of the lithological composition of sediments from the whole-lake basin were performed on the small eutrophic L. Linajärv (northern Estonia) and the concentrations of mineral and organic matter were measured on 647 sub-samples from 14 sediment cores. The accumulation rate of the sediment sequences was established and C/N ratios of organic matter in some cores were recorded. Results indicate that the water depth, basin slopes and distance to the shore have the most important impact on the physical sediment properties. It was shown that variations in the mineral matter concentrations were influenced by the changes in deposition conditions in the areas with steep slopes. The study indicated that more objective information about the sedimentation mechanisms is obtained using analysis of the concentration ratio of mineral and organic matter since it reduces the implied role of diagenetic compaction.     

On the potential of basing an ecological typology of aquatic sediments on the nematode fauna: An example from the River Rhine

In Dutch river sediments nematodes can occur in high numbers; azoic seediments are as yet unknown. In aseries of samples takenj from the river Rhine and its estuaries, nematode density varied from 5.000 to 1.7 million per square metre, and about 50 genera were identified. Anoxic conditions appear to have less influence on the nematode abundance than the presence of ammonia. Based on nematode genera, an ecological typology of aquatic soils would appear to be feasible. The use of nematodes in environmental studies is discussed.     

Modern bryomol-sediments in a cool-water, high-energy setting: the inner shelf off Northern Brittany

Summary The inner shelf off Roscoff/North Brittany, France situated in the Western English Channel, provides a unique facility for studying modern cold water BRYOMOL-carbonate deposits in the North Atlantic. High tidal gauge with extreme strong tidal currents, which effect the well-mixed water column throughout the year, and strong, seasonal storms characterize the conditions of the area. The shelf is seperated in two carbonate production zones: Boulder fields and sand fields. The main production areas are the sand fields with an intensive epifaunal and infaunal colonization by bivalves and the bryozoan thickets ofCellaria spp. and their associated epifauna. The most beneficial and dominant strategies of the sessile benthos are erect flexible and encrusting growth habits. The study area is partitioned in two zones: (1) the coarse sediment blanket typified by active sediment generation and little accumulation, and (2) the shell dune Trezen ar Skoden, characterized by accumulated sediments. Sediment transport and distribution of facies areas are controlled by the strong semidiurnal tidal current regime and episodically severe storms. As a result of these high energy processes of redeposition the autochthonous sediment particles are physically reworked and redeposited while in calmer periods deposition and biological destruction of the components occur. The Holocene development of the sea level has been of crucial influence to the costal morphology and the establishment of different carbonate production centers. The benthic communities produce with their carbonate skeletons the first biogenic sediment and provide substrates for colonization of epi- and endofauna. Changes in the current patterns and the morphology of the sea bottom resulted in the origin of the shell dune Trezen ar Skoden.     

Seasonal respiratory responses to temperature and hypoxia in relation to burrowing depth in three intertidal bivalves

Respiratory responses to temperature and hypoxia in relation to burrowing depth were determined for winter- (W-C) and summer-conditioned (S-C) individuals of , , and . These bivalves occur sympatrically on sand-flats but display different sediment burrowing depths ( . , <2 cm; . , 3–8 cm; . , 5–20 cm). A range depths over which daily temperature variation and O₂ concentration decline rapidly from surface values. Species thermal tolerance limits were found to decrease and to be more greatly temperature compensated with burrowing depth. Oxygen consumption rate (VO₂ increased with temperature to 25°C in . , but was, thereafter, regulated (Q10 1.0) up to 40°C while VO₂ increased with temperature in . and . until thermally streased at 25° to 30°C. The deposit feeding . does not acclimate VO₂ to temperature while . and . , both suspension feeders, show “reverse” acclimation [VO₂ (W-C) < VO₂ (S-C)] that conserves overwintering energy stores. The shallow burrowing . and deposit feeding . rarely experience hypoxia and are poor to non-regulators of VO₂ in reduced O₂ concentrations. In contrast, when winter-conditioned, . is a moderate regulator of VO₂, the degree of regulation increasing in S-C individuals which are exposed to higher levels of hypoxia.     

A Study on the Macro-Zoobenthos and the Physico-chemical Characteristics of the Bottom of Bakhira Lake,Uttar Pradesh,India

Bakhira Lake is the largest man-made lake of Eastern Uttar Pradesh. It is utilized for Boro (coarse paddy) cultivation, irrigation and fishing by poor village farmers. Hydrographical features, qualitative and quantitative composition of the macro-zoobenthos, and the physico-chemical characteristics of the bottom water and sediment were studied from October 1976 to April 1977. Molluscs, insects, ostracods, annelids, nematodes and crustaceans are the main groups of zoobenthos. Molluscs together with insects dominate the benthic fauna (95.2 to 96.4% of numbers). The benthic density varied from 273 to 517 individuals/m². Average density of macro-zoobenthos is more or less inversely related to the total alkalinity of the bottom water. Molluscs showed a positive correlation to temperature and a negative correlation to insect density.     

Response of Carnian Pluvial Episode evidenced by organic carbon isotopic excursions from western Hubei,South China

We here report a high-resolution organic C-isotope record from terrestrial–marine transitional sediments of the Badong Formation in the Luojiagou section, Zigui Basin of Hubei Province, South China. Our organic carbon isotope (δ¹³C_org) profile, ranging from -21.2‰ to -26.2‰, shows four negative carbon-isotope shifts. We suggest that the sharpest negative carbon isotope excursion in the upper portion of the Badong Formation marks the main phase of the Carnian Pluvial Episode (CPE) in the basin, likely correlated with those in other depositional records of this time. The occurrence of the CPE in the Badong Formation would imply that the stratigraphic coverage of the Badong Formation might be prolonged to incorporate (at least part of) the Late Triassic Carnian stage. This result provides a potential case for understanding the CPE in continental–marine environments in the eastern Tethys realm, and is significant for exploring the palaeoclimate variation across the Late Triassic.     

Trace metal fractionation in water and sediments of an urban river stretch

Abstract

In this study, the fractionation and ecotoxic potential of Cr, Ni, Cu and Pb in water and sediments of the river Yamuna (Delhi stretch) is presented. The river water is used for various purposes such as irrigation, industrial, domestic and drinking. The investigations suggest that the availability of metals in water follows the sequence Ni>Cr>Pb>Cu whereas a different pattern (Pb>Cu>Ni>Cr) is observed in sediments. Statistically significant spatial variations are indicated by two-way ANOVA in different geochemical forms of the metals and physicochemical parameters of water and sediments of the river Yamuna. Principal component analysis (PCA) suggests a similar source for all four metals probably from the sewage from municipal drains. PCA also indicates some independent sources of Cu and Pb. The hot spots were identified using hierarchical cluster analysis considering bioavailable forms of the metals in water and sediments as objects and the sampling sites as variables. Risk assessment code analysis indicates that metals generally pose medium to high risk at different sites. However, at a few locations either Ni or Pb cross the level of very high ecological risk.     

Environmental change and the chemical record in Loch Lomond sediments

The chemical record in Loch Lomond sediments deposited since the end of the last Ice Age provides evidence of the Flandrian marine transgression some 5500–7000 ¹⁴C years B.P., sedimentation rates and the influence of man's local activities, environmental pollution and its sources since the onset of the Industrial Revolution, and of elemental mobility linked with the reduction-diffusion-oxidation cycle of early sedimentary diagenesis. Information derived from vertical profiles of halogen elements bromine and iodine, radionuclides ¹⁴C and ²¹⁰Pb, heavy metals lead, zinc, and cadmium, stable lead isotopes ²⁰⁶Pb and ²⁰⁷Pb, and redox-sensitive elements manganese, iron and arsenic is reviewed and assessed.