SEARCH · PubMed Health

Results for “Geologic Sediments”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 973 records · Page 54Linked to original sources

PubMed2004

Organochlorine micropollutants in the Jiulong River Estuary and Western Xiamen Sea, China.

Organochlorine contaminants including 12 polychlorinated biphenyl (PCB) congeners and 18 insecticides were determined in water, pore water and sediments of the Jiulong River Estuary and Western Xiamen Sea, China. The results showed that the levels of the total PCBs ranged from non-detectable to 1500 ng l(-1) in water, from 209 to 3870 ng l(-1) in pore water, and from 2.78 to 14.8 ng g(-1) dry weight in sediments. Total organochlorine insecticide concentrations were from below the limit of detection to 2480 ng l(-1) in water, from 267 to 33400 ng l(-1) in pore water, and from 4.22 to 46.3 ng g(-1) dry weight in sediments. Concentrations of PCBs and insecticides in pore water were significantly higher than those in surface water, due to the high affinity of these hydrophobic compounds for sediment phase. The PCB congeners with the highest concentrations were CB153, CB180 and CB194, which together accounted for 68-87% of total PCBs in water, pore water and sediment. Among the hexachlorocyclohexane (HCH) compounds, beta-HCH was found to be a major isomer. Analysis of 1,1,1-trichloro-2,2-bis-chlorophenyl-ethane (DDT) and its metabolites showed that 1,1-dichloro-2[o-chlorophenyl]-2[p-chlorophenyl]-ethylene (DDE) was dominant in the group. In comparison to a 1998 study in the Western Xiamen Sea, levels of organochlorines were enhanced due probably to recent inputs and changes in sediments.

China↗

PubMed2005

Historical and ecological analysis of coral communities in Castle Harbour (Bermuda) after more than a century of environmental perturbation.

The coral reefs in Bermuda's Castle Harbour basin have been subjected to varying anthropogenic stressors for over 100 years. These include restriction of water flow through the construction of a causeway in the late 19th century and an extensive dredging and land reclamation operation during World War II. In the 1970s, disposal of bulk waste commenced at a foreshore reclamation site in Castle Harbour. Since 1996 the waste stream has included blocks of cement-stabilized municipal incinerator ash. This study provides a historical and quantitative ecological review of the Castle Habour reef ecosystem as a case study, assessing the responses of the reef to more than a century of anthropogenic disturbance. Measures of the coral community, flow rates, turbidity and sedimentary regimes suggest the present structure of the coral community largely reflects the impacts of the historic dredge and fill operations prior to the establishment of the foreshore dump site. Recent increases in the abundance of some sediment tolerant, massive reef-building coral species (Diploria strigosa and Montastraea cavernosa) suggest adaptation to chronic sediment stress.

Adaptation, Physiological↗

PubMed2004

Linearity and reversibility of iodide adsorption on sediments from Hanford, Washington under water saturated conditions.

A series of adsorption and desorption experiments were completed to determine the linearity and reversibility of iodide adsorption onto sediment at the Hanford Site in southeastern Washington. Adsorption experiments conducted with Hanford formation sediment and groundwater spiked with dissolved (125)I (as an analog tracer for (129)I) indicated that iodide adsorption was very low (0.2 mL/g) at pH 7.5 and could be represented by a linear isotherm up to a total concentration of 100 mg/L dissolved iodide. The results of desorption experiments revealed that up to 60% of adsorbed iodide was readily desorbed after 14 days by iodide-free groundwater. Because iodide adsorption was considered to be partially reversible, even though small amount of initial iodide is retarded by adsorption at mineral-water interfaces, the weak adsorption affinity results in release of iodide when iodide-free pore waters and uncontaminated groundwaters contact the contaminated sediments in the vadose zone and aquifer systems.

Adsorption↗

PubMed2001

Correlation analyses on binding behavior of heavy metals with sediment matrices.

This article presents the amounts of heavy metals bound to the sediment matrices (carbonates, Fe-oxides, Mn-oxides, and organic matter), the correlations between any two heavy-metal binding fractions, and the correlations between sediment matrices and their heavy-metal binding fractions. Data consisted of 313 sets obtained from five main rivers (located in southern Taiwan) were analyzed by statistical methods. Among six heavy metals analyzed (Zn, Cu. Pb, Ni, Cr, and Co), the statistical results show that Zn is primarily bound to organic matter, and Cr is primarily bound to Fe-oxides. Principal component analysis (PCA) and correlation analysis (CA) result in significant correlations between carbonates bound Ni and carbonates bound Cr, Fe-oxides bound Ni and Fe-oxides bound Cr, and Mn-oxides bound Cu and Mn-oxides bound Cr. From linear regression results, the levels of the six heavy metals bound to either organic matter or Fe-oxides is moderately dependent on the contents of organic matter or Fe-oxides, especially true for Cr and Pb. According to slope values of linear regression, Cu and Cr have the highest specific binding amounts (SBA) to organic matter and Fe-oxides, respectively. A significant correlation between organic matter and organically bound heavy metals implied that organic matter contained in the sediments of the Potzu river and the Yenshui river can be adequately used as a normalizing agent. However, the six heavy metals bound to either carbonates or Mn-oxides do not correlate with carbonates or Mn-oxides. The obtained results also imply that competitions of various sediment phases in association with heavy metals occur, and organic matter and Fe-oxides are more accessible to heavy metals than other sediment phases.

Binding Sites↗

PubMed2002

Sequestration of priority pollutant PAHs from sediment pore water employing semipermeable membrane devices.

Semipermeable membrane devices (SPMDs) were employed to sample sediment pore water in static exposure studies under controlled laboratory conditions using (control pond and formulated) sediments fortified with 15 priority pollutant polycyclic aromatic hydrocarbons (PPPAHs). The sediment fortification level of 750 ng/g was selected on the basis of what might be detected in a sediment sample from a contaminated area. The sampling interval consisted of 0, 4, 7, 14, and 28 days for each study. The analytical methodologies, as well as the extraction and sample cleanup procedures used in the isolation, characterization, and quantitation of 15 PPPAHs at different fortification levels in SPMDs, water, and sediment were reported previously (Williamson, M.S. Thesis, University of Missouri-Columbia, USA; Williamson et al., Chemosphere (This issue--PII: S0045-6535(02)00394-6)) and used for this project. Average (mean) extraction recoveries for each PPPAH congener in each matrix are reported and discussed. No procedural blank extracts (controls) were found to contain any PPPAH residues above the method quantitation limit, therefore, no matrix interferences were detected. The focus of this publication is to demonstrate the ability to sequester environmental contaminants, specifically PPPAHs, from sediment pore water using SPMDs and two different types of fortified sediment.

Chemistry Techniques, Analytical↗

PubMed2004

Method for the determination of organophosphate insecticides in water, sediment and biota.

A procedure for the determination of 13 organophosphate insecticides (OPs) in water, sediment and biota at low ppb levels is described. Samples were extracted with dichloromethane or acetone/hexane and cleaned up with micro-column silica gel chromatography. Measurements were made by dual capillary column gas chromatography using both nitrogen-phosphorus (NPD) and electron capture (ECD) detection. Recoveries from fortified water samples ranged from 76% to 102% for all sample types. Practical detection limits ranged between 0.003 and 0.029 microg/l in natural water samples, 0.0004-0.005 microg/g w.w. for sediments, and 0.001-0.005 microg/g w.w for biota using the NPD and ECD method. Losses in sediments were experienced when sulphur was removed. Precision and accuracy were not affected in sediment samples where sulphur was not removed.

Acetone↗

PubMed2001

Estimates of benthic fluxes of nutrients across the sediment-water interface (Guarapiranga reservoir, São Paulo, Brazil).

Concentration profiles of nutrients (dissolved organic carbon, nitrate, nitrite, ammonium and soluble reactive phosphorus) were determined in pore waters from sediment from the Guarapiranga reservoir (São Paulo, Brazil). Redox potential and acid volatile sulfide measurements on bulk sediment samples were determined in the field and laboratory, respectively. The sediment redox potential ranged from -170 to -220 mV at 0-1 cm and increased to somewhat higher values at 20 cm. The acid volatile sulfide (AVS) profile had a bimodal pattern with concentration peaks at 3 cm (27-55 mg kg(-1)) and 14 cm (70-110 mg kg(-1)). Dissolved organic carbon (DOC) concentrations increased from the surface (4.7-5.6 mg l(-1)) to 20 cm (values up to 12 mg l(-1)). The concentration of ammonium increased significantly with depth, with maximum concentrations occurring at 15 cm; nitrate-nitrite concentrations only increased appreciably at 10 cm. The SRP profiles increased in concentration from the surface to approximately 10-cm depth, with a maximum value of 1200 microg H2PO4- l(-1). Benthic fluxes from the sediment into the pore water ranged from 278 to 339 mg cm(-2) year(-1) for ammonium ions and from 8 to 18 mg cm(-2) year(-1) for SRP. These upward diffusive fluxes correspond to 47-70% and to 10-24% of the total deposition of N and P measured in the reservoir, respectively. The burial rates for N and P in these sediments are 30-54% and 76-89%, respectively.

Brazil↗

PubMed2001

Diagenesis of magnetic minerals in the intertidal sediments of the Yangtze Estuary, China, and its environmental significance.

In this study, diagenesis of iron oxides in intertidal sediments of the Yangtze Estuary, China, has been investigated by combined environmental magnetic and geochemical methods. The results indicated that the magnetic properties of the sediments were dominated by ferrimagnetic magnetite. The content of Fe, DCB- and AOD-extractable iron oxides correlated positively with the concentration of fine grained magnetite near the superparamagnetic/stable single domain (SP/SSD, approximately 0.03 microm) boundary, and with anti-ferromagnetic minerals (hematite/goethite). The magnetic parameters for core SDK indicated a substantial decrease in magnetite concentration from a depth of approximately 20 cm toward the surface, together with a shift in the grain-size distribution of magnetic minerals toward the coarse end, suggesting selective dissolution of fine grained magnetite under reducing conditions. The reduction of iron oxides inferred from magnetic measurements was supported by the similar decrease in the concentration of Fe and Mn and a lower ratio of Mn/Fe. Magnetic measurements on another core from elsewhere also indicated substantial reductive dissolution of iron oxides. In conjunction with the results of heavy metal analysis, it was suggested that the dissolution of iron oxides had a direct effect on the cycling of heavy metals. Therefore, magnetic measurements may provide useful information as to early diagenesis within intertidal sediments, which greatly influences the behavior of heavy metals in coastal environments.

Environmental Monitoring↗

PubMed1998

Heavy metals in sediments from the Paraguay River: a preliminary study.

The first results ever obtained on heavy metal concentrations (Fe, Mn, Cr, Cu, Zn and Pb) in the Paraguay River surface sediments are presented. Samples collected at 11 locations, along a distance of 570 km, between the cities of Bahia Negra and Alberdi in Paraguay, for six different periods between November 1991 and 1993, were analyzed. The Paraguay sediments appeared to have features of an unpolluted river even though significant amounts of domestic and industrial effluents are discharged near the river channel. The relative heavy metal enrichment in sediments between Bella Vista and Asunción, caused by local domestic sewage and industrial outfalls, is less than for the shale standard values. The heavy metal content of the sediments exhibited seasonal variations. Enhanced organic matter content and biochemical oxygen demand of the river load in winter caused most likely a retainment of the heavy metals in a dissolved state. Consequently, the sediments deposited in the winter were relatively depleted in these elements.

Environmental Monitoring↗

PubMed1999

Eutrophication process recorded in dinoflagellate cyst assemblages--a case of Yokohama Port, Tokyo Bay, Japan.

To investigate temporal changes of water quality, a role of dinoflagellate cysts preserved in surface sediments was examined in Yokohama Port in Tokyo Bay, Japan. Two cores were collected, and sedimentation rates and ages of both were dated as approximately 1900 years or slightly older on the basis of 210Pb and 137Cs concentrations. The temporal change in dinoflagellate cyst assemblages in the two cores reflects eutrophication in Yokohama Port in the 1960s. Abrupt increases in the cysts of Gyrodinium instriatum cysts strongly suggests that a red tide was caused by this species around 1985. Dinoflagellate cyst assemblages in surface sediments appear to be good biomarkers of changes in the water quality of enclosed seas.

Animals↗

PubMed2003

Distribution of petroleum hydrocarbon in sediment from coastal area receiving industrial effluents in Kuwait.

Sediment samples from the coastal area facing Shuaiba industrial area (15 x 1.5 km(2)) were examined for contamination with petroleum hydrocarbons. Aliphatic hydrocarbons in sediment extracts were characterized largely by unresolved complex mixture from nC(22)-nC(33). The sediment samples from the upstream area facing Mina Al-Ahmadi refinery to Shuaiba Harbor were heavily polluted with polycyclic aromatic hydrocarbons (PAHs) possibly due to the higher depth in the area created for a navigational channel to the harbor. PAHs at these locations exceeded the probable effect levels with reference to sediment quality guidelines.

Environmental Monitoring↗

PubMed2003

Spectral imaging detection and counting of microbial cells in marine sediment.

Semiautomated detection and counting techniques for microbial cells in soil and marine sediment using microscopic-spectral-imaging analysis were developed. Microbial cells in microscopic fields were selectively detected from other fluorescent particles by their fluorescent spectrum, based on the spectral shift between the conjunction and nonconjunction of DNA fluorochrome (SYBR Green II) with nucleic acids. Using this technique, microbial cells could be easily detected in soil and 30-cm deep sediment samples from Tokyo Bay, both of which contain particles other than microbial cells. Total cell density was semiautomatically estimated at 1-6 x 10(9) cells cm(-3) of sediment sampled at different depths in Tokyo Bay, which corresponded to 65-106% (mean 88%) of visual direct counting. This technique may be useful for detecting microbial cells in soil and sediment samples from the deeper subsurface environment.

Bacteria↗

PubMed2001

Using fluffy layer material to study the fate of particle-bound organic pollutants in the southern Baltic Sea.

This paper examines the utility of fluffy layer material for studying and monitoring the environmental levels, transport, and fate of particle-bound contaminants in coastal ecosystems. Fluffy layer material is the very young and mobile layer of particulate matter that accumulates on the sediment surface under quiescent conditions. We used this material to study the behavior of polycyclic aromatic hydrocarbons (PAHs) that are discharged by the Oder River into the Baltic Sea. With the fluffy layer material, it was possible to (i) do fingerprint analysis to trace the sources of PAHs in the river discharge, (ii) follow the modification of the PAHs from the mouth of the river to the depositional basin and identify the responsible processes, (iii) monitor the seasonal variation in the PAH input, (iv) study the influence of a major flood event on the PAH loading to the coastal ecosystem, and (v) conduct a PAH mass balance to estimate the contribution of the Oder River source to PAH accumulation in the depositional basin. The fluffy layer material integrated the particle-bound contaminant signal over a period ranging from several days to several months, depending on the sampling location. As such, fluffy layer material is a valuable addition to the matrixes commonly used for studying particle-associated chemicals: SPM and sediment, which reflect time scales of hours and years, respectively.

Environmental Monitoring↗

PubMed2002

Sorption of polycyclic aromatic hydrocarbons and polychlorinated biphenyls to soot and soot-like materials in the aqueous environment: mechanistic considerations.

Recent studies have shown that sorption of polycyclic aromatic hydrocarbons (PAHs) in soot-water systems is exceptionally strong. As a consequence, soot may fully control the actual fate of PAHs in the aquatic environment. However, sorption has only been characterized for a limited number of PAHs to diesel soot, and the mechanism is poorly understood. In this paper, we present an extensive data set of sorbent-water distribution coefficients (K(S), n = 236) for a series of PAHs (both native and added) and polychlorinated biphenyls (PCBs) to five different types of soot and five soot-like materials. Both Ks values and physicochemical properties of the sorbents show large variation. In general, sorption is very strong, with K(S) values up to 10(10), showing the highest distribution coefficients on a mass basis ever reported. Sorption of in particular PAHs is often over 1000 times as strong as sorption to amorphous sedimentary organic carbon. The variation in K(S) values cannot be explained by "soot carbon fractions" or specific surface areas of the sorbents. Instead, values for native PAHs are mostly determined by the sorbates' molar volume, and values for added PAHs and PCBs are determined by the sorbents' average pore diameter. From differences in K(S) values between native and added PAH analogues, it can be deduced that generally more than 50% (with values up to 97%) of the native PAH concentration in soot is not available for distribution to the aqueous phase. We conclude that this is caused by physical entrapment of the chemicals within the solid matrix. Furthermore, most sorbents appear to preferentially sorb PCBs with planar configurations, a phenomenon most likely driven by sorption in molecular-sized pores. Pore sorption is also concluded to be the most important sorption mechanism for added PAHs together with pi-pi interaction processes with flat aromatic sorbent surfaces. Frequently observed, slowly desorbing, resistant contaminant fractions in sediments may very well be explained on the basis of these results.

Adsorption↗

PubMed2002

Anaerobic, sulfate-dependent degradation of polycyclic aromatic hydrocarbons in petroleum-contaminated harbor sediment.

It has previously been demonstrated that [14C]-labeled polycyclic aromatic hydrocarbons (PAHs) can be oxidized to 14CO2 in anoxic, PAH-contaminated, marine harbor sediments in which sulfate reduction is the terminal electron-accepting process. However, it has not previously been determined whether this degradation of [14C]-PAHs accurately reflects the degradation of the in situ pools of contaminant PAHs. In coal tar-contaminated sediments from Boston Harbor, [14C]-naphthalene was readily oxidized to 14CO2, but, after 95 d of incubation under anaerobic conditions, there was no significant decrease in the detectable pool of in situ naphthalene in these sediments. Therefore, to better evaluate the anaerobic biodegradation of the in situ PAH pools, the concentrations of these contaminants were monitored for ca. 1 year during which the sediments were incubated under conditions that mimicked those found in situ. There was loss of all of the PAHs that were monitored (2-5 ring congeners), including high molecular weight PAHs, such as benzo[a]pyrene, that have not previously been shown to be degraded under anaerobic conditions. There was no significant change in the PAH levels in the sediments amended with molybdate to inhibit sulfate-reducing bacteria or in sediments in which all microorganisms had been killed with glutaraldehyde. In some instances, over half of the detectable pools of in situ 2-3 ring PAHs were degraded. In general, the smaller PAHs were degraded more rapidly than the larger PAHs. A distinct exception in the Boston Harbor sediment was naphthalene which was degraded very slowly at a rate comparable to the larger PAHs. In a similar in situ-like study of fuel-contaminated sediments from Liepaja Harbor, Latvia, there was no decline in PAH levels in samples that were sulfate-depleted. However, when the Latvia sediments were supplemented with sufficient sodium sulfate or gypsum to elevate pore water levels of sulfate to approximately 14-25 mM there was a 90% decline in the naphthalene and a 60% decline in the 2-methylnaphthalene pool within 90 days. These studies demonstrate for the first time that degradation by anaerobic microorganisms can significantly impact the in situ pools of PAHs in petroleum-contaminated, anoxic, sulfate-reducing harbor sediments and suggest that the self-purification capacity of contaminated harbor sediments is greater than previously considered.

Bacteria, Anaerobic↗

PubMed2005

Diffusion of the synthetic pyrethroid permethrin into bed-sediments.

Bed-sediments are a sink for many micro-organic contaminants in aquatic environments. The impact of toxic contaminants on benthic fauna often depends on their spatial distribution, and the fate of the parent compounds and their metabolites. The distribution of a synthetic pyrethroid, permethrin, a compound known to be toxic to aquatic invertebrates, was studied using river bed-sediments in lotic flume channels. trans/cis-Permethrin diagnostic ratios were used to quantify the photoisomerization of the trans isomer in water. Rates were affected by the presence of sediment particles and colloids when compared to distilled water alone. Two experiments in dark/light conditions with replicate channels were undertaken using natural sediment, previously contaminated with permethrin, to examine the effect of the growth of an algal biofilm at the sediment-water interface on diffusive fluxes of permethrin into the sediment. After 42 days, the bulk water was removed, allowing a fine sectioning of the sediment bed (i.e., every mm down to 5 mm and then 5-10 mm, then every 10 mm down to 50 mm). Permethrin was detected in all cases down to a depth of 5-10 mm, in agreement with estimates by the Millington and Quirk model, and measurements of concentrations in pore water produced a distribution coefficient (Kd) for each section. High Kd's were observed for the top layers, mainly as a result of high organic matter and specific surface area. Concentrations in the algal biofilm measured at the end of the experiment under light conditions, and increases in concentration in the top 1 mm of the sediment, demonstrated that algal/ bacterial biofilm material was responsible for high Kd's at the sediment surface, and for the retardation of permethrin diffusion. This specific partition of permethrin to fine sediment particles and algae may enhance its threat to benthic invertebrates. In addition,the analysis of trans/cis-permethrin isomer ratios in sediment showed greater losses of trans-permethrin in the experiment under light conditions, which may have also resulted from enhanced biological activity at the sediment surface.

Bacteria↗

PubMed2006

PCB congeners and dechlorination in sediments of Lake Hartwell, South Carolina, determined from cores collected in 1987 and 1998.

Four sediment cores were collected from Lake Hartwell, SC, in 1987 and 1998 and analyzed for polychlorinated biphenyl (PCB) congeners. Total PCBs ranged from -0 to 58 microg/ g. Positive matrix factorization (PMF) was applied to the data sets to determine PCB source profiles. Two factors were determined for each data set. One factor resembled the original estimated PCB mixture of 80% Aroclor 1016 and 20% Aroclor 1254 and the other factor was a dechlorinated version of the mixture. Evidence of a dechlorination plateau is apparent from the PMF loading solutions because the dechlorinated congener profiles do not change from 1987 to 1998, butthe contribution to the profile from the dechlorinated factor increases from 73% (1987) to 87% (1998). PMF source contributions and plots of PCB concentration versus congener for individual samples provide evidence of enhanced dechlorination at high concentrations. After source apportionment an anaerobic dechlorination model was applied to the dechlorinated source profiles to quantify possible dechlorination pathways. It was found that dechlorination process M, extended to target biphenyl rings with up to six chlorines, provided the best fit for an individual process, and M + Q provides the best fit for combined processes, although M + LP also provides a similarfit. Process LP targets the higher chlorinated congeners and appears to dechlorinate PCBs in the sediments initially.

Chlorine↗

PubMed2006

Wetland plant uptake of desorption-resistant organic compounds from sediments.

Wetland plant uptake of 14C-labeled phenanthrene and chlorobenzene was investigated in greenhouse studies using sediment prepared to contain only the desorption-resistant fraction of the contaminant. Measurements of contaminant distribution in the plants and root-contaminant partition coefficients were conducted as well as estimates of the transpiration stream concentration of chlorobenzene and phenanthrene. Plant uptake of desorption-resistant phenanthrene and chlorobenzene occurred primarily in the root zone with total uptake ranging from 3.8 to 5.7% of the initial concentration in the sediment. Observed uptake of the compounds was remarkably similar despite wide differences in contaminant properties. A biphasic sorption isotherm was combined with a simple translocation model to predict plant uptake from two processes: root sorption and translocation. The model predicted the observed uptake well and may serve as an important tool for estimating plant uptake in sediments containing a desorption-resistant fraction. The potential implications of the existence of a finite, desorption-resistant pool of contaminants on phytoremediation of sediments are discussed.

Adsorption↗