Intertidal Surface Sediments Research Articles

Heavy metal pollution in intertidal sediments from Quanzhou Bay, China

The concentrations of eight heavy metals (Cu, Zn, Pb, Cd, Cr, Ni, Hg, and As) in the intertidal surface sediments from Quanzhou Bay were determined to evaluate their levels and spatial distribution due to urbanization and economic development of Quanzhou region, southeast China. The ranges of the measured concentrations in the sediments are as follows: 24.8-119.7 mg/kg for Cu, 105.5-241.9 mg/kg for Zn, 34.3-100.9 mg/kg for Pb, 0.28-0.89 mg/kg for Cd, 51.1-121.7 mg/kg for Cr, 16.1-45.7 mg/kg for Ni, 0.17-0.74 mg/kg for Hg, and 17.7-30.2 mg/kg for As. The overall average concentrations of above metals exceed the primary standard criteria but meet the secondary standard criteria of the Chinese National Standard of Marine Sediment Quality. Several contents of Cu and Hg exceed the secondary standard criteria at some stations. The results of geoaccumulation index (Igeo) show that Cd causes strong pollution in most of the study area. There are no significant correlations among most of these heavy metals, indicating they have different anthropogenic and natural sources. Some locations present severe pollution by heavy metals depending on the sources, of which sewage outlets, aquatic breeding, and commercial ports are the main sources of contaminants to the area.

An assessment of metal contamination along the Irish coast using the seaweed Ascophyllum nodosum (Fucales, Phaeophyceae)

The relative abundance and variation of Cr, Co, Cd and Pb in Ascophyllum nodosum and intertidal surface sediments from six locations around the coast were assessed over six seasons. Higher Cd and Pb levels in Galway Docks and Cork Harbour were attributed to localised inputs of these metals from municipal and domestic waste, while at a reference site (Ballyconneely), high algal Cr concentrations were considered a function of geological setting rather than anthropogenic loading. Little seasonal variation was observed, with the exception of higher Co levels in plants in winter, associated with growth dynamics and increased fluvial inputs. In comparison with previously published data for metals in A. nodosum from the North Atlantic, with the exception of localised hot spots, the Irish coastline is still a relatively pristine environment. A. nodosum may be successfully and easily used as a biomonitor of metal contamination in coastal waters.

Incorporation of nitrogen from amino acids and urea by benthic microbes: role of bacteria versus algae and coupled incorporation of carbon

We investigated the incorporation of nitrogen from amino acids and urea by the micro- bial community in intertidal surface sediment, focusing on the relative contributions of bacteria ver- sus algae to total microbial nitrogen incorporation and the (un)coupled incorporation of carbon from these organic substrates. Dual-labeled ( 15 N and 13 C) urea and an amino acid mixture were added to surface sediment from 2 intertidal mudflats in the Scheldt Estuary (The Netherlands), and 15 N and 13 C were subsequently traced into bulk sediment, total hydrolysable amino acids (THAAs) and the bac- terial biomarker D-alanine (D-Ala) over a 24 h incubation period. All added 15 N from urea and the amino acids was incorporated into microbial biomass within 24 h, with relatively rapid incorporation of 15 N from the amino acids. The bacterial contribution to total microbial 15 N incorporation (derived from 15 N incorporation into D-Ala) was large during the first 1 to 2 h of incubation, but small to negli- gible after 24 h for both substrates, indicating that total 15 N incorporation was dominated by benthic microalgae (diatoms) that also dominated total microbial biomass in the sediment. Comparison of 15 N versus 13 C incorporation into total microbial biomass (THAAs) after 24 h showed strong preferential incorporation of urea-N over urea-C. Incorporation of nitrogen and carbon from the amino acids was partially uncoupled, indicating that a large fraction (≥50%) of amino acid-N was taken up as NH4 +

Intertidal surface type mapping in the Danish Wadden Sea

A map of the intertidal surface sediment types in the central and northern part of the Danish Wadden Sea has been constructed on the basis of a thematic classification of a Landsat ETM+ scene combined with information from two texture measure images derived from orthophotos and an extensive ground truth collection. The mapped intertidal area covers 397 km 2 in three tidal regions: Grådyb, Knudedyb and Juvre Dyb. The classification of the surface types reveals that tidal flats cover 71% and water permanently covers 29% of the mapped area. Four tidal flat types could be distinguished: mudflat 2%, mixed flat (wet/moist) 12%, low (wet) sand flats 46%, and high (dry) sand flat 11%. The fine-grained tidal flat types (mud and mixed flats) are primarily located in the northern tidal area of Grådyb (8.4%). Their areal coverage decreases towards the south (Knudedyb, 4.6%; Juvre Dyb, 1.1%) which reflects a similar decreasing southern trend in the import of fine-grained material.

Ammonium regeneration in intertidal sediments of the Yangtze estuary during air-exposure

The influences of exposure to the atmosphere on ammonium cycle in the intertidal surface sediments were in situ studied with a geochemical approach at a typical station in the Yangtze Estuary during three tidal cycles in September 2003. During an about 8-h emersion period of each diurnal tide, six high-resolution vertical profiles of adsorbed and dissolved ammonium were measured. It was observed that both adsorbed and dissolved ammonium generally had an increasing trend in sediment cores during the exposure. The rate of ammonium regeneration in sediments was estimated using the accumulation amount of ammonium including adsorbed and soluble fractions during the daytime emersion. The calculation result showed that there was relatively high ammonification rate (˜500 nmol N cm−3 day−1), which reflected that organic nitrogen in sediments was quickly decomposed with a residence time of ˜52.7 days. Due to the dramatic temperature difference observed in sediment profiles, free convection was considered an important mechanism of regulating the efflux of produced ammonium into overlying waters. The total estimated amount of regenerated ammonium was ˜1.35×105 t N year−1 in the intertidal flat of the Yangtze Estuary, which occupied 7.6% of the total inorganic nitrogen annually transported to the estuarine ecosystem.

Mercury concentrations in the surface sediments of the intertidal area along the west coast of Peninsular Malaysia

Total mercury (Hg) levels in the intertidal surface sediments along the west coast of Peninsular Malaysia were analysed by using heat vaporization method. Total Hg levels in these sediments ranged from 3.00 to 201 µg kg−1 dry weight with a mean concentration of 60.0 µg kg−1 dry weight. More than 90% of the samples studied have the total Hg concentrations less than 150 µg kg−1 dry weight. Compare with the regional data and sediment quality guidelines, the Hg contamination in the intertidal area along the west coast of Peninsular Malaysia was not serious, except for a few sites that might have received anthropogenic Hg in the samples collected between 1999 and 2000. It is suggested that a similar study of heavy metals in the sediments of the west coast of Peninsular Malaysia be conducted regularly.

Total metals in intertidal surface sediment of oyster culture areas in Sonora, Mexico.

Total metals in intertidal surface sediment of oyster culture areas in Sonora, Mexico.

Environmental assessment of polycyclic aromatic hydrocarbons (PAHs) in surface sediments of the Santander Bay, Northern Spain

Samples of intertidal surface sediments (0–2 cm) were collected in 17 stations of the Santander Bay, Cantabric Sea, Northern Spain. The concentrations of polycyclic aromatic hydrocarbons (PAHs), 16, were analysed by HPLC and MS detection. Surface sediments show a good linear correlation among the parameters of the experimental organic matter evaluation, where total carbon (TC) and loss on ignition (LOI) are approximately 2.5 and 5 times total organic carbon (TOC). A wide range of TOC from 0.08% to 4.1%, and a broad distribution of the sum of ∑16PAHs, from 0.02 to 344.6 μg/g d.w., which can be correlated by an exponential equation to the TOC, has been identified. A qualitative relationship may be established between the industrial input along the rivers and the concentration of ∑16PAHs in the sediments of the estuaries: Boo estuary (8404–4631 μg/g OC), Solia–San Salvador estuaries (305–113 μg/g OC) and Cubas estuary (31–32 μg/g OC). This work shows a dramatic change in the spatial distribution in the concentration of PAHs of intertidal surface sediments. The left edge of the Bay has the main traffic around the city and the major source of PAHs is from combustion processes and estuarine inputs, leading to medium values of PAHs in the sediments; the right edge of the Bay has much lesser anthropogenic activities leading to lower values of PAHs in sediments. The distribution of individual PAHs in sediments varies widely depending on their structure and molecular weight; the 4–6 ring aromatics predominate in polluted sediments due to their higher persistence. The isomer ratio does not allow any clear identification of the PAHs origin. Environmental evaluation according to Dutch guidelines and consensus sediment quality guidelines based on ecotoxicological data leads to the same conclusion, sediments in the Santander Bay show a very different environmental quality depending on the spatial position from heavily polluted/medium effects to non-polluted/below threshold effects. These results indicate that local sources of PAHs, especially estuary discharges, lead to very different qualities of sediments in coastal zones, where traffic and industrial activities take place.

Community structure and activity of sulfate-reducing bacteria in an intertidal surface sediment: a multi-method approach

The community structure of sulfate-reducing bacteria (SRB) in an intertidal mud flat of the German Wadden Sea (Site Dangast, Jade Bay) was studied and related to sedimentary biogeo-chemical gradients and processes. Below the penetration depths of oxygen (∼3 mm) and nitrate (∼4 mm), the presence of dissolved iron and manganese and the absence of dissolved sulfide indicated suboxic conditions within the top 10 cm of the sediment. Moderate to high bacterial sulfate reduction rates were measured with radiotracers throughout the sediment, and dissimilatory sulfate reduction was also demonstrated by the presence of acid-volatile sulfides (AVS, essentially iron monosulfide). Stable sulfur isotope discrimination between dissolved sulfate and AVS was dominated by sulfate reduction. The diversity of SRB was studied using denaturant gradient gel electrophoresis of 16S rDNA, phospholipid fatty acid analysis and counting viable cells with the most probable number technique. Phylogenetic groups of SRB identified with these techniques were almost evenly distributed throughout the top 20 cm of the sediment. Application of fluorescence in situ hybridization, however, demonstrated a maximum of active members of the Desulfovibrio and Desulfosarcina-Desulfococcus-Desulfofrigus groups between 2 and 3 cm depth. These 2 groups encompass acetate and lactate utilizing SRB. The coincidence of this SRB maximum with a local maximum of sulfate reduction rates and the depletion of acetate and lactate reflects the microbiological processes related to sulfate reduction.

Heavy Metal Contamination and Mixing Processes in Sediments from the Humber Estuary, Eastern England

The geochemical properties of cores collected from mud flat and salt marsh environments in the Humber Estuary were investigated. A total of 10 cores were collected along a shore-normal transect on the northern bank of the estuary, near Skeffling. Major and trace element concentrations were determined for each core. The vertical distributions of210Pb and137Cs were also examined to provide a measure of the rate of sediment accumulation. Surface intertidal sediments show elevated concentrations of a range of trace and major elements, including Pb, Zn, Cu, Al, Mn and Fe. Concentrations were higher in the upper mud flats and salt marsh where sediment grain size is finer. Dating of salt marsh sediments indicated a local sediment accretion rate of 0·4cmyr−1. The early-diagenetic remobilization of heavy metals has apparently been limited, and the salt marsh sediments provide a (time-integrated) record of historical pollutant inputs. Heavy metal fluxes have been calculated from the salt marsh sediments and are broadly comparable with other industrialized and semi-industrialized estuaries. Cu, Pb and Zn inputs to the Skeffling area peaked in the mid-20th century, while Ti, Al and Fe, which are discharged into the Humber from two Tioxide-processing facilities, are only slightly enriched in these sediments. On the mud flats, local mixing, resuspension and erosion has resulted in correlatable sedimentary horizons interspersed with mixed sediment layers. Consequently, the vertical distribution of heavy metals in these mud flats is relatively erratic, and the mud flat sediments are unsuitable for studying historical pollution trends.

Heavy metal contamination of brown seaweed and sediments from the UK coastline between the Wear river and the Tees river

The concentration of Fe, Mn, Zn, Cu, Pb, Ni, Cr, Cd, and Ag were determined in the brown alga Fucus vesiculosus and intertidal surface sediments from coastal locations of northeast England. Levels of heavy metals similar to those of polluted areas of the British coastline were detected. There is evidence of contamination (especially with Zn and Pb) in sediments from sites affected by colliery spoil and from the Wear estuary. The pelitic fraction (<63 μm) is usually more enriched in heavy metals, but it represents a very small percentage of the bulk samples. The fine-grained sand is a very important repository of contaminants especially where particles of colliery spoil, secondary mineral, and amorphous phases are present. Aqua regia-extracted Zn, Cu, and Pb in sediments are significantly correlated with those in seaweed. Despite the closure of all base metal and coal mines, and the cessation of many industrial activities in the region, sediments and brown algae are contaminated with heavy metals. The control site (Holy Island) and the Tees estuary appear to be the least affected.

Denitrification in intertidal black anoxic surface sediments forms rather N2O and nitrite instead of molecular nitrogen

During the “Black Area Event” of June/July 1996 in the Ostfriesian Wadden Sea, many square kilometers of the intertidal zone in the Ostfriesian Wadden Sea (Southern North Sea, Germany) lost the oxic sediment cover and showed a black surface of sulfidic sediment. This and earlier work on smaller “Black Spots” caused reason to examine the effects on crucial ecological functions such as denitrification in the sediments. This was done by examining the denitrification potential defined as a measured microbial denitrification activity which develops in a biologically active sediment sample after a non-limiting addition of nitrate and/or organic electron donors. Four types of sediment samples were examined: Black surface, black sediment from below a black surface, oxic surface sediment from a reference area and black sediment from below this oxic sediment. The oxic sample showed the highest activity. In the presence of added electron donors, added nitrate was completely converted to N2 within about 15 days. Transient N2O did not or only in traces appear which later were reduced to N2. In corresponding experiments with samples from the Black Spot (surface and depth) and black sediments from below the oxic cover nitrate was also converted to gaseous products. After about 7 days nearly 80% of the nitrate-N appeared as N2O and after 45 days the ratio between N2O-N and N2-N was still between 1:1 and 2:1, representing together 100% of the added N. While a change of the temperature from 20 to 30°C mainly resulted in a faster conversion rate and not so much in a different intermediate and product spectrum, a change to 7°C led to an accumulation of nitrite which only in the oxic sediment samples was converted to N2. The main result is that the transition of the surface sediment from oxic to sulfidic means a shift from the denitrification end product N2 to partially reduced ones such as nitrite and N2O.

Heavy Metals in Intertidal Surface Sediments from the Patagonian Coast, Argentina

The Patagonian coastal area of Argentina is nearly 3000 km long. It is a growing, developing region and is a highly biologically productive ecosystem. Human population is distributed among 13 towns, ranging from less than 1,000 inhabitants in Bahia Camarones to nearly 126,000 in Comodoro Rivadavia. The main pollution problems are related to sewage effluents with deficient or without treatment, agricultural runoff from the Negro and Colorado rivers, petroleum extraction and transportation and heavy metals wastes located near ports. Previous studies of metal concentrations in Patagonian marine sediments are scarce and restricted to Nuevo and San Jose Gulfs (Harvey and Gil 1968).The aim of the present work, is to determine the content of total mercury and 0.5 N HCI leachable zinc, copper, lead and cadmium in intertidal surface sediments from 17 stations along Patagonian coast, between Colorado and Gallegos rivers.

Observations on the redistribution of plutonium and americium in the Irish Sea sediments, 1978 to 1996: concentrations and inventories

The distribution of plutonium and americium in the sub-tidal sediments of the Irish Sea is described following major surveys in 1978, 1983, 1988 and 1995. Concentrations in surface sediments have declined near the source at Sellafield since 1988. Time-series of inter-tidal surface sediment concentrations are presented from 1977 onwards, revealing the importance of sediment reworking and transport in controlling the evolution of the environmental signal. The surface and near-surface sediments, in the eastern Irish Sea ‘mud-patch’, are generally well mixed with respect to Pu ( α) and 241Am distributions but show increasing variability with depth –up to 4 orders of magnitude in concentration. The inventories of 239,240Pu and 241Am in the sub-tidal sediments have been estimated and compared with the reported decay-corrected discharges. These amounted to 360 and 545 TBq respectively, in 1995, about 60% of the total decay-corrected discharge. Part of the unaccounted fraction may be due to unrepresentative sampling of the seabed. It is speculated that some tens of TBq of plutonium and 241Am reside undetected in the large volumes of coarse-grained, sub-tidal and inter-tidal sediment which characterise much of the Irish Sea. This has been due to the inability of the available corers to penetrate to the base of contamination in these mobile sediments. Further observations are needed to verify and quantify the missing amount. A budget of plutonium- α and 241Am has been estimated based on published observations in the three main compartments: water column, sub-tidal and inter-tidal sediments. This amounts to 460–540 TBq and 575-586 TBq respectively, or 64–75% and 60–61%, of the decay-corrected reported discharge.

Coprostanol in the Intertidal sediments of Kuwait. case study on urban sewage contamination

The present study was conducted to assess the nature and degree of contamination by urban sewage discharge in the costal zone of Kuwait. Intertidal surface sediments were collected from the vicinity of coastal effluents and bathing beaches. The sediments were characterized for their sterol composition (coprostanol; cholesterol; campesterol; stigmasterol and β‐sitosterol) and total organic carbon content (TOC). The analyses revealed that the fecal biomarker coprostanol is present at levels ranging between 0.55–45.06 μg/g dry weight, which amounted to 9.9–49.45% of the total sedimentary sterols measured. The locus of highest impact is the southwestern edge of Kuwait Bay at Shuwaikh area. This probably resulted from the continuous sewage discharge from effluent, slow speed tidal currents and the nature of sediments. The overall patterns of distribution indicate that the sewage‐derived material discharged from coastal effluent is affected by the physical processes constraining the area. The prevailing tidal currents contribute to fecal contamination of bathing beaches. Significant correlations were found between organic sewage derived materials (coprostanol/total sterol) and TOC. The sterols composition, other than the fecal inputs indicates the contribution of both terrigenous and biogenic inputs to sedimentary organic matter.

Tidal flushing of ammonium from intertidal sediments of Ria Formosa, Portugal

Ammonium concentrations were determined in near-bottom water and intertidal surface sediments collected in February and July 1993 at five stations of Ria Formosa, a shallow meso-tidal coastal lagoon in southern Portugal. At each station, samples were taken a few minutes before tidal inundation, and subsequently 2, 10, 15 and 20 minutes thereafter. Ammonium concentration in near-bottom waters increased dramatically in the first 2 minutes followed by a decrease during the 18 minutes of flooding (maximum range 10.3-2.2 μM). The highest levels in the flooding water were concomitant with a decrease of extractable ammonium recorded in the upper sediment layer (2 cm). Laboratory experiments indicated that ammonium is easily extracted from the sediment solids by physical perturbation, as one would expect when tidal water flushes over the intertidal area. This perturbation results in the export of ammonium from the sediment, by pulse mechanisms of short time intervals. On a daily scale this amount is two orders of magnitude higher than transport resulting from molecular diffusion.

Role of microorganisms in mineralization processes in intertidal surface sediments subject to high temperatures: An incubation experiment

In order to study how N, P, Fe, Mn and S concentrations in pore waters change with time at different temperatures, an incubation experiment was carried out with surficial intertidal sediment. To evaluate the importance of benthic microorganisms, an abiotic control was established by poisoning sediment. The live and poisoned sediments were incubated for ten hours at 10, 21, 30 and 40°C. Dissolved Inorganic Nitrogen (DIN), Dissolved Reactive Phosphorus (DRP), NH4+, total dissolved manganese (Mndiss), total dissolved iron (Fediss) and soluble inorganic sulphide (HS−)t were followed in the pore water samples. Results indicated that high temperature influenced nitrification, allowing accumulation of ammonia and that microorganism activity did not seem important for Mn reduction. Anaerobic nitrification by Mn reduction was advanced as an explanation of the behaviour of DIN during the experiment.

The application of microwave heating in sequential extractions of heavy metals in estuarine sediments

Using a modification of the procedure elaborated by Tessier et al. (1979) the conditions under which microwave heat was applied to perform sequential extractions of metals in estuarine sediments were evaluated. Necessary times were determined for the complete metal extractions and substantial reductions in time were obtained in comparison with the traditional techniques, (from hours to minutes). The techniques were applied to two reference materials: MESS-1 and SEDIMENTO (a secondary standard prepared in our laboratory). The problems of methodology associated with the use of microwaves are discussed, as well as the results obtained regarding the variability of the data of each fraction and the percentages of recovery. The techniques were also applied to intertidal surface sediments of three northwestern Spanish estuaries. Percentages of recovery are discussed as well as the relationship of the results to the physical/chemical variables of the medium.

Sources and distribution of hydrocarbons in Bridgwater Bay (Severn Estuary, U.K.) intertidal surface sediments

Hydrocarbon distributions in two intertidal, surface sediments from Bridgwater Bay were examined by high performance liquid chromatography (HPLC), gas chromatography (GC) and gas chromatography/mass spectrometry (GC-MS) to investigate distributions and sources of hydrocarbons. Two major hydrocarbon sources were identified, pyrogenic polycyclic aromatic hydrocarbons (PAHs) and a chronic petrogenic input. Other probable sources were algal, higher-plant and DDT-related pesticides. It was not possible to detect a contribution to the surface sediments from a nearby Liassic shale. Petrogenic biomarker distributions were broadly similar in the sediment samples, possibly reflecting a degree of resuspension and mixing of sediments within Bridgwater Bay. However, the significance of some slight differences in steroidal hydrocarbon distributions could not be determined. A relatively greater contribution from the petrogenic source(s) than from the pyrogenic source was noted in the finer grained sediment sample. An extended range of PAHs was noted in both sediment samples, with molecular weights of up to 326 detected. A group of compounds, comprising terphenyls, cyclohexylbiphenyls and dicyclohexylbenzenes, was detected, which appeared to have a petrogenic origin.

Plutonium in intertidal coastal and estuarine sediments in the Northern Irish Sea

Surface intertidal sediments from 35 sites in the Irish Sea have been analysed for their 238Pu and 239,240Pu activities, together with an intensive study of plutonium in sediments of the Esk Estuary (NW England). The range of plutonium activities for the whole survey were 0·14–4118 and 1·3–16 026 Bq kg −1 for 238Pu and 239,240Pu, respectively. The levels of Pu activity, derived from the Sellafield nuclear fuel reprocessing effluents, in sediments are controlled by lithological factors and the influence of transport and post-depositional processes. Grain size distribution is particularly important, the major part of plutonium activity being in the mud fraction of all sediments. The data suggest that over the Irish Sea coastline, dynamic mixing of sediment grains by reworking and resuspension and/or by dispersion in tidal currents are important in determining plutonium distributions. The exponential decrease in sediment plutonium activities away from the Sellafield source is attributed to the progressive mixing with older contaminated and uncontaminated sediments.