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PubMed2004

Elevated levels of arsenic in the sediments of an urban pond: sources, distribution and water quality impacts.

The discovery of significantly elevated levels of arsenic (As) in the sediments of Spy Pond motivated us to identify the principal As source and to investigate the extent of contamination within the pond. Spy Pond is located in Arlington (MA, USA), a residential and commercial town with no known history of As use by industry or agriculture. Spy Pond is a kettle-hole pond composed of two basins (north and south) separated by a shallow sill. Sediment cores from the two basins were analyzed for As content by instrumental neutron activation analysis and dated by measuring 210Pb activity. The As concentration profiles for the north and south basins had maxima that dated to approximately 1962 and approximately 1956, respectively. These dates are consistent with records of arsenical herbicide use, which indicate that between 1960-1968 sodium arsenite (NaAsO2) and arsenic oxide (As2O3) were applied to the pond to control aquatic macrophytes. Estimates of As loadings to the two basins-- approximately 410 kg ( approximately 32 kg ha(-1)) to the north and approximately 5800 kg ( approximately 580 kg ha(-1)) to the south--are consistent with the range of application rates reported for other lakes treated with arsenical herbicides. To determine the extent of As contamination in the pond, 68 surface sediment samples were analyzed by energy dispersive X-ray fluorescence. Arsenic levels ranged from 1 to 2600 ppm in the north basin (n = 49) and from 120 to 1100 ppm in the south basin (n = 19). Background sediment-As levels for the area are 10-40 ppm. The highest concentrations of As in the sediments of Spy Pond are comparable to levels measured in lakes contaminated with chemical manufacturing and mining wastes. These results are discussed with respect to As remobilization and sediment treatment measures planned for the pond.

Arsenic↗

PubMed2005

The sequestration of PCBs in Lake Hartwell sediment with activated carbon.

Recent laboratory studies with a marine sediment from a tidal mudflat in San Francisco Bay demonstrated that a low dose of activated carbon enhances the sequestration of PCBs and PAHs under well-mixed conditions. Here we compare activated carbon treatment for a freshwater sediment from a rural site, using PCB-contaminated sediment from Lake Hartwell, SC. An activated carbon dose of 2% of the dry sediment mass lowered total aqueous PCB concentrations by more than 95% after 1 month of treatment and more than 98% after 6 months. Aqueous PCB concentrations remained below detection limits following 18 months of sediment-carbon contact in slowly mixed systems. Uptake of PCBs into semipermeable membrane devices was reduced by 78%, 91% and 97% over 1, 6 and 18 months, respectively. These tests show that PCB sequestration with activated carbon improves with contact time and is not diminished by prolonged mixing with sediment. Desorption studies confirmed the sequestration, in which 74% of the total PCB mass could be desorbed from untreated Lake Hartwell sediment within 30 days as compared to only 7% after activated carbon treatment for 6 months. We compare these observations with marine sediment from San Francisco Bay and propose a conceptual model to rationalize how sediment properties relate to the reduction in aqueous PCB concentrations during activated carbon treatment.

Carbon↗

PubMed2005

Sources and growth dynamics of fecal indicator bacteria in a coastal wetland system and potential impacts to adjacent waters.

Coastal wetlands are receiving increased attention as a putative source of fecal indicator bacteria (FIB) in Southern California coastal waters. We examined temporal trends of water and sediment-associated FIB after rain events along with spatial sediment characteristics at two sites within the Santa Ana River wetlands and made comparisons to FIB levels observed in adjacent surf zone waters. During the first two rain events, total coliforms (TC), Escherichia coli (EC) and enterococci (ENT) in wetland water and sediment samples peaked either on the same day or within several days of the rain event, while the third resulted in elevated wetlands sediment TC levels only. TC in adjacent coastal waters consistently peaked on the same day as the rain event and decreased quickly thereafter (within 1 day). The TC/EC ratios of surf zone samples consistently fell below 10, indicating an increased probability of human fecal contamination whereas wetland TC/EC ratios were higher, averaging approximately 60 and 14 at each site. These results suggest sediment-associated FIB populations may be distinct from those found in the water samples, or at least have internal dynamics independent of water-borne populations. Increases in sediment-associated FIB may be due to in situ population growth and/or increased survival due to changes in environmental parameters (salinity, moisture and nutrient input) resulting from the rain events. Spatial differences in between the two sites may be due to sediment differences such as organic content and finer grain size and/or discrete sources of FIB.

Ecosystem↗

PubMed2006

Persistence of fecal indicator bacteria in Santa Monica Bay beach sediments.

Monitoring the water quality of recreational beaches is only one step toward understanding microbial contamination -- the primary cause of beach closings. The surf zone sediment reservoir is typically overlooked and may also be important. This study involved monitoring the fecal indicator bacteria (FIB) levels in water and sediment at three ocean beaches (two exposed and one enclosed) during a storm event, conducting laboratory microcosm experiments with sediment from these beaches, and surveying sediment FIB levels at 13 beaches (some exposed and some enclosed). Peaks in Escherichia coli and enterococci concentrations in water and sediment coincided with storm activity at the two exposed beaches, while levels of both FIB were consistently high and irregular at the enclosed beach. Results from microcosm experiments showing similar, dramatic growth of FIB in both overlying water and sediment from all beaches, as well as results from the beach survey, support the hypothesis that the quiescent environment rather than sediment characteristics can explain the elevated sediment FIB levels observed at enclosed beaches. This work has implications for the predictive value of FIB measurements, and points to the importance of the sediment reservoir.

Bathing Beaches↗

PubMed2003

Methods for selective determination of persistent organochlorine pesticide residues in water and sediments by capillary gas chromatography and electron-capture detection.

Different extraction methods were evaluated for the determination of fifteen organochlorine pesticides (OCPs) in water and sediments. Liquid-liquid extraction (LLE) was evaluated for the pesticides analyses in water while Soxhlet extraction (SE) and microwave assisted extraction (MAE) methods were compared in sediment. Of all the extracting solvents used, dichloromethane gave the best results. Percentage recoveries ranged from 71.03 +/- 8.15 (dieldrin) to 101.25 +/- 2.17% [a-benzenehexachloride (alpha-BHC)] in water with LLE. In sediments the percentage recoveries with Soxhlet extraction method varied between 88.22 +/- 7.85 (endrin) and 109.63 +/- 5.10% (beta-BHC) and ranged from 74.11 +/- 9.82 (2,4 DDT) to 97.50 +/- 4.56% (alpha-BHC) with MAE. The limits of detection for the OCPs ranged from 5.5 to 20.6 ng/l and between 0.6 and 2.1 ng/g. respectively. The LLE and the SE methods were applied to water and sediments samples, respectively, from marine and freshwater sources in the Eastern Cape Province of South Africa that receive runoffs from agricultural lands and effluents from industries. The levels of OCPs ranged from 5.5 (2,4-DDD) to 450 +/- 0.10 ng/l (beta-BHC) in water samples and from 0.6 (aldrin and 2,4-DDD) to 184 +/- 0.12 ng/g (beta-BHC) in sediments for triplicate analyses. Some endocrine disrupting OCPs such as DDT, DDE, heptachlor, endosulphan and the chlordanes were detected.

Chromatography, Gas↗

PubMed2001

Developing a method to track oil and gas produced water discharges in estuarine systems using salinity as a conservative tracer.

Produced water is a high salinity by-product resulting from oil and gas production. Disposal methods include surface water discharge from a point source. The current field method used for fate and effect determinations in open water estuarine systems involves extending a compass oriented transect (COT) from the point source discharge--a method designed for a uniform offshore environment that might be inappropriate for the hydrologic and geomorphologic complexities found in estuarine systems. Research was conducted in a canal and a small, semi-enclosed bay to observe effluent behaviour and to determine if salinity could be used to track the effluent. A salinity/conductivity/temperature (SCT) probe measured water properties within 1 cm of the sediment surface and identified a thin, bottom salinity plume that would have gone undetected by conventional instruments. The plume flowed across the sediment surface and towards greater depths. Plume-affected sampling stations exhibited higher levels of sediment contaminant indicators (SCIs) and indicated that station location could affect impact conclusions.

Environmental Monitoring↗

PubMed2001

Aeolian flux of metals in Taiwan in the past 2600 years.

To identify anthropogenic sources of pollution, it is useful to compare recent and historical data, yet unfortunately such data are lacking in Taiwan. Thus, we studied the sediments deposited in the remote anoxic, subalpine Great Ghost Lake over a time span of 2600 yrs. Not only could a baseline be established, but also natural variations could be identified. Aeolian Asian dust particles seem to have played a significant role in the flux of 26 elements (Al, As, Ba, Br, Ca, Cd, Ce, Cl, Cr, Cs, Cu, Fe, Ga, K, Mg, Mn, Na, Ni, Pb, Rb, Si, Sr, Ti, V, Zn and Zr) in Great Ghost Lake. The fluxes have generally been higher during dry periods, especially since 1350 AD. On the other hand, local pollution from lead seems to have gained importance since 1945 AD. Recent aeolian fluxes were also calculated based on sediment data, and those results agree with direct measurements obtained in the region.

Climate↗

PubMed2001

Aerobic and anaerobic abiotic oxidation of squalene in the presence of hydroperoxides.

Abiotic oxidation of squalene in the presence of hydroperoxysterols was studied in seawater under aerobic and anaerobic conditions. This ubiquitous isoprenoid alkene is quickly degraded in the presence of oxygen and its oxidation results mainly in the production of tertiary alcohols and to a lesser extent of epoxides and secondary alcohols. Although the degradation of squalene logically slows down under anaerobic conditions, a significant oxidation affording similar products than in the case of aerobic degradation has been observed. These results show that hydroperoxysterols, which seem to be well preserved in Recent sediments, could contribute to the oxidation of unsaturated lipids (such as squalene) in sedimentary environments under oxic and anoxic conditions.

Geologic Sediments↗

PubMed2001

Nonylphenols, nonylphenol-ethoxylates, linear alkylbenzenesulfonates (LAS) and bis (4-chlorophenyl)-sulfone in the German Bight of the North Sea.

Nonylphenols and nonylphenol-ethoxylates were detected in the water and sediment samples from the German Bight of the North Sea. Additionally bis (4-chlorophenyl)-sulfone and linear alkylbenzenesulfonates (LAS) were detected in marine waters. Proof of identification is given by comparison of spectral and chromatographic data from the compounds in sample extracts to those obtained from pure standards. In extracts obtained from water samples taken in 1990 and 1995 the concentrations of nonylphenols and bis-(4-chlorophenyl)-sulfone were compared for each year. The concentrations of nonylphenols in seawater varied from 0.7 to 4.4 ng/l while in the Elbe estuary about 33 ng/l were found. In water samples taken in 1998 nonylphenol-polyethoxylates could not be determined, whereas LAS concentrations of 30 ng/l were confirmed by HPLC-MS/MS. The concentrations of bis (4-chlorophenyl)-sulfone ranged from 0.18 to 2.2 ng/l. In sediment samples LAS concentrations of 39-109 ng/g dry weight were determined.

Alkanesulfonic Acids↗

PubMed2002

PCB removal from contaminated dredged material.

The purpose of this study was to evaluate the feasibility of decontaminating PCB contaminated sediment using land treatment technology. Five glass aquariums were set up to test the disappearance of polychlorinated biphenyls (PCBs) in dredged sediment under laboratory conditions that simulated photodegradation, biological transformation, and volatilization in dredged material confined disposal facilities (CDFs). A 40% decline in PCB concentration was achieved over a period of 5 months. Analysis of the variance in the data showed that periodic tilling produced a tangible effect on the disappearance of PCBs. However, the process or processes responsible for PCB disappearance could not be determined. PCB disappearance from the sediment was most likely caused by a combination of photolysis, volatilization, and biodegradation mechanisms rather than by any single process.

Decontamination↗

PubMed2001

Characterization of organic matter in pristine and contaminated coastal marine sediments using solid-state 13C NMR, pyrolytic and thermochemolytic methods: a case study in the San Diego harbor area.

Chemical composition of coastal marine sedimentary organic matter (SDOM) is a function of natural and anthropogenic inputs to the system. In this study a combination of analytical techniques: 13C nuclear magnetic resonance (NMR), pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) and tetramethylammonium hydroxide thermochemolysis-gas chromatography/mass spectrometry (TMAH thermochemolysis-GC/MS) were used to study the contribution of hydrophobic organic contaminants and terrestrial OM to the SDOM. Sediments were collected from two sites in the San Diego Bay: Paleta Creek, which is contaminated, and Coronado Cayes, which is relatively pristine. Concentrations of polycyclic aromatic hydrocarbons (PAHs) at both sites, as determined by ultrasonically assisted lipid extraction are found to be higher in the surface layer, to generally decrease with depth, and to be present at about two orders of magnitude higher concentration at the contaminated site as compared to the pristine site. The sediment samples were partially deashed with HF/HCI treatment before further analysis. 13C-NMR spectra of the Paleta Creek samples show a higher aromatic carbon content and a distinct phenolic carbon peak. This suggests a large input from terrestrial carbon (lignin). Data from both Py-GC/MS and TMAH thermochemolysis-GC/MS support this and indicate the presence of lignin-derived residues, primarily of the guaiacyl type at the contaminated site. In contrast, SDOM at the Coronado Cayes site exhibits less terrestrial input. In general, the SDOM resembles soil OM rather than typical marine SDOM. Chemical analyses of the lipid-extracted, partially deashed sediments, does not reveal the presence of any PAHs.

California↗

PubMed2000

Mercury contamination in the Yatsushiro Sea, south-western Japan: spatial variations of mercury in sediment.

Mercury-contaminated effluent was discharged into Minamata Bay from a chemical plant over a 20-year period until 1965 (from 1958 to 1959, effluent was discharged into Minamata River), causing Minamata disease. In an effort to characterize the extent of the contamination in the Yatsushiro Sea, the vertical and horizontal distributions of mercury in sediment were investigated. Sediment was sampled at 62 locations in the southern part of the sea from 4 to 6 March 1996. In the lower layers of the long cores of sediment, the total amount of mercury was at a relatively uniform low concentration. We interpret these low values to represent the background concentration absent of anthropogenic influence. The background value thus estimated for the Yatsushiro Sea was 0.059 +/- 0.013 mg kg(-1) (mean +/- S.D., n = 51). The highest concentration in each sample ranged from 0.086 to 3.46 mg kg(-1) (mean, 0.57 mg kg(-1)). The higher values were obtained at stations near Minamata Bay and the Minamata River (the sources of the pollution). Concentrations decreased with distance from the source. An inspection of the vertical profiles of mercury concentration in cores suggested that the deposited mercury had not been fixed in sediment but had been transported, despite 30 years having past since the last discharge of contaminated effluent. At nine stations, extractable inorganic and organic mercury concentrations were determined differentially. Inorganic mercury is the predominant species in sediment and organic mercury comprising approximately 1% of the total.

Chemical Industry↗

PubMed2002

On modelling the impacts of phosphorus stripping at sewage works on in-stream phosphorus and macrophyte/epiphyte dynamics: a case study for the River Kennet.

A new model of in-stream phosphorus and macrophyte dynamics, 'The Kennet model', was applied to a reach of the River Kennet, southern England. The reach, which is 1.5 km long, is immediately downstream of Marlborough sewage treatment works, where phosphorus reduction by tertiary effluent treatment began in September 1997. The model is used to simulate the flow, water chemistry and macrophyte biomass within the reach, both before and after phosphorus removal from the effluent. Monte Carlo experiments coupled with a general sensitivity analysis indicate that the model offers a feasible explanation for the salient aspects of the system behaviour. Model simulations indicate that epiphyte smothering is an important limitation to macrophyte growth, and that higher stream and pore water soluble reactive phosphorus (SRP) concentrations allow the earlier onset of growth for the epiphytes and macrophytes, respectively. Higher flow conditions are shown to reduce the simulated peak epiphyte biomass; though at present, the effect of flow on the macrophyte biomass is unclear. Another simulation result suggests that phosphorus will not be released from the bed sediments in this reach following phosphorus removal from the effluent.

Biomass↗

PubMed2002

Metal bioavailability and toxicity through a sediment core.

Sediment cores from Richard Lake near Sudbury, Ontario, were sectioned and analyzed for total metal content, plus metal bioavailability and toxicity to Hyalella azteca (after equilibration with oxygenated overlying water). Strong and similar sediment profiles were observed for Cd, Co, Cu and Ni in the sediment. However, these differed from metal bioavailability profiles (bioaccumulation by Hyalella and metals in overlying water). Bioavailability profiles for Cu also differed from those for Cd, Co or Ni. The deepest sediment layers, deposited prior to industrial development, were non-toxic. Sediment toxicity was attributed to Ni dissolution into overlying water. Moreover, differential bioavailability of Ni in surface and deeper sediment layers was observed. This can affect the interpretation of toxicity data for sediments collected by different methods (e.g. core vs. grab samples). Based on Pb-210 dating and trends in Ni in the core, chronic toxicity of surface sediments from Richard Lake might approach non-toxic levels in about 15 years.

Animals↗

PubMed2002

Escherichia coli and total coliforms in water and sediments at lake marinas.

Escherichia coli, a fecal coliform, and total coliforms were monitored between September 1999 and October 2001 in five marinas at Lake Texoma, located on the Oklahoma and Texas border. The general trend was that densities of E. coli were lower in the summer season due to the lower loading of fecal material into Lake Texoma and the ecological conditions of the lake, such as more vigorous grazing by protozoa and less viability of E. coli at an elevated temperature. The densities of total coliforms greatly increased in the summer. E. coli levels increased with depth, and the bottom water samples had higher densities of E. coli mainly due to their association with particles. There was a direct relationship between amount of gasoline sold, which was related to recreational boating activity, and the resuspension of E. coli. This indicated that recreational boating activity in lake marinas may have resuspended bottom sediments with bound E. coli, and the presence of E. coli in marinas was not an indication of recent fecal contamination. E. coli were detected in the largest densities at the boat dock points, followed by the gasoline filling station, and marina entrance. In addition, enumeration of bacteria in bottom sediment showed that the densities of E. coli and total coliforms in sediment were much higher compared to those in lake water.

Enterobacteriaceae↗

PubMed2001

Toxic potency assessment of non- and mono-ortho PCBs, PCDDs, PCDFs, and PAHs in northwest Mediterranean sediments (Catalonia, Spain).

Forty-five marine sediments from the Catalonian coast were analyzed for non-ortho and mono-ortho chlorine substituted PCB congeners, PCDDs and PCDFs, and 16 PAHs. Concentrations of total PCBs ranged from 1.1 to 311 ng/g dry weight (d.w.), and the levels of the sum of the 16 PAHs analyzed ranged between 13.4 ng/g d.w. and 16.7 microg/g d.w. The PCB and PAH contamination was greater near the sites of urban and industrial impact. Total toxicity equivalent (TEQ) values were calculated using the toxicity equivalent factors (TEFs) proposed by WHO for dioxin-like PCBs, PCDDs, and PCDFs. These levels ranged between 0.03 and 24.8 pg WHO-TEQ/g d.w. for PCBs and from 0.4 to 39.2 pg WHO-TEQ/g d.w. for PCDDs/PCDFs. Therefore, the suggested sediment quality guideline was sometimes exceeded. Moreover, TEA values were calculated for PAH concentrations, applying different TEFs proposed by the literature. The results obtained were between 0.3 pg TEQ/g d.w. and 18.4 ng TEQ/g d.w. and showed that the TEQ(PCDD/F) and TEQ(PCB) values were several times lower than the TEQ(PAH) values in the marine sediment samples investigated.

Benzofurans↗

PubMed2003

Assessing long-term pH change in an Australian river catchment using monitoring and palaeolimnological data.

Reviews of stream monitoring data suggest that there has been significant acidification (>1.0 pH unit at some sites) of Victorian streamwaters over the past 3 decades. To assess whether these declines are within the range of natural variability, we developed a diatom model for inferring past pH and applied it to a ca. 3500-yr diatom record from a flood plain lake, Callemondah 1 Billabong, on the Goulburn River, which has among the most substantial observed pH declines. The model has a jackkniffed r2 between diatom inferred and measured pH of 0.77 and a root mean square error of prediction of 0.35 pH units. In the pre-European period, pH was stable (range 6.5-6.7) for approximately 3000 yr. Since European settlement around 160 yr ago, diatom-inferred billabong pH has increased significantly by >0.5 units. We hypothesize that this increase in pH is related to processes associated with land clearance (e.g., increased base cation load and decreased organic acid load). There is no evidence of the recent monitored declines in the Callemondah record, which may indicate that that flood plain lakes and the main stream are experiencing divergent pH trends or that the temporal resolution in the billabong sediment record is insufficient to register recent declines.

Acid Rain↗

PubMed2005

Isomer-selective adsorption of amino acids by components of natural sediments.

We present evidence that under circumstances of low pH and organic-free surfaces an ordinary estuarine sediment can exhibit strong optical isomer selectivity in its absorption of a number of amino acids. This selectivity can also be seen to a lesser degree in the minerals quartz, montmorillonite, and kaolin. Adsorption reactions were performed with racemic amino acid mixtures, and after equilibrium, deviations from a D/L ratio of 1 were measured and in many cases were found to be significant. This was particularly pronounced at pH 4.0, where selective removal of the L isomers by adsorption onto sedimentfractions was almosttotal. Changes in both the nature and degree of selectivity were also observable in different sediment size fractions. While we are at this stage unable to identify the mode of primary selectivity, adsorption experiments with these candidate sediment components, quartz, kaolin, and montmorillonite do exhibit some selective behavior. We believe that the existence of natural chirally selective components in sediment may indicate a new approach to the development of chiral catalysis and synthesis.

Adsorption↗