Heavy metals in sediments from the Athens sewage outfall area

Sediments in the upper Saronikos Gulf have been contaminated by heavy metals from the discharge of untreated industrial and domestic wastewater from the area around Athens. Neutron activation analysis indicates concentrations of antimony, arsenic, chromium, gold, mercury, silver and zinc are 8–200 times greater than in the surrounding uncontaminated sediments. The bottom area affected by increased metal concentrations is at least 13 km² and indicates a nearly radial dispersal pattern from the main outfall with higher concentrations extending to the southeast and southwest.     

The effect of the new Massachusetts Bay sewage outfall on the concentrations of metals and bacterial spores in nearby bottom and suspended sediments

Since the new outfall for Boston's treated sewage effluent began operation on September 6, 2000, no change has been observed in concentrations of silver or Clostridium perfringens spores (an ecologically benign tracer of sewage), in bottom sediments at a site 2.5 km west of the outfall. In suspended sediment samples collected with a time-series sediment trap located 1.3 km south of the outfall, silver and C. perfringens spores increased by 38% and 103%, respectively, in post-outfall samples while chromium, copper, and zinc showed no change. All metal concentrations in sediments are <50% of warning levels established by the Massachusetts Water Resources Authority. An 11-year data set of bottom sediment characteristics collected three times per year prior to outfall startup provides perspective for the interpretation of post-outfall data. A greater than twofold increase in concentrations of sewage tracers (silver and C. perfringens) was observed in muddy sediments following the exceptional storm of December 11-16, 1992 that presumably moved contaminated inshore sediment offshore.     

Sediment disturbance off the Tagus Estuary, Western Portugal: chronic contamination, sewage outfall operation and runoff events

Sediment disturbance patterns in the coastal area off the Tagus Estuary (Portugal) have been assessed using a set of combined techniques. The potential sources of disturbance in the area include chronic contamination of the fine sediments originating from the estuary, a local input from a long-sea sewage outfall and occasional high runoff episodes following torrential rain. The Sediment Quality Triad approach, combining environmental chemistry (namely organic contaminants), macrofaunal benthic communities and laboratory sediment toxicity assays, was performed on sediment samples from 20 sites. The samples were collected before the outfall commenced operation and four years after commissioning, in order to evaluate the relative magnitudes of the three potential sources of disturbance. The sediment contamination created by the estuary was identified as the most important cause of reduced sediment quality, as disturbance in all three components of the Sediment Quality Triad were only found in a site located near the estuary.     

Assessment of organotin contamination in marine sediments and biota from the Gulf and adjacent region

Butyltin species were measured in sediments from coastal locations in the Gulf and Gulf of Oman. Both butyltin and phenyltin species were measured in biota samples from four countries in this region. With tributyltin (TBT) concentrations up to 60 ngSng(-1), some sediments could be classified as contaminated (i.e. TBT>1.3 ngSng(-1)), namely Dukhan (Qatar), the BAPCO industrial complex and Askar (Bahrain), and Hilf and the Raysut Port Area (Oman). Higher concentrations of total butyltins were found in oysters relative to fish, but ranging from 6.5 to 488 ngSng(-1) dry weight they are nonetheless relatively low. Diphenyltin and triphenyltin were found in some fish and bivalves from the Gulf, but not in biota from the Gulf of Oman. The environmental levels of organotin species are comparatively low by global standards and pose no immediate public health problems.     

Monitoring seagrass beds around a sewage sludge outfall in South Australia

Digested sludge from the Port Adelaide Sewage Treatment Works has been discharged to Gulf St. Vincent, a marine embayment in South Australia, since 1978. The outfall is sited in seagrass meadows dominated by Posidonia spp. and Amphibolis spp. By 1982 the discharge had affected an area of approximately 1900 ha, 365 ha of which were completely denuded of these seagrasses. A monitoring programme conducted over summers 1983–1985, inclusive, was based on the above-ground biomass (standing crop) of Posidonia at fourteen sites around the outfall. All sites were surveyed in the first two summers and eight sites were surveyed in the third. The results indicate that there was no ongoing reduction in the standing crop of Posidonia at any of the sites. These data also suggested that excessive growth of epiphytes on the leaves of Posidonia was a likely cause of the observed impact on the seagrass beds.     

Metals in marine sediments near a large California municipal outfall

Elevated concentrations of trace metals in surficial sediments off Palos Verdes Peninsula, site of the Los Angeles County outfall system, clearly reflect the submarine discharge of treated municipal (domestic and industrial) wastewater. The following contamination factors (median outfall/median baseline) were obtained for the eight metals measured in a 45 km² region of the outfall monitoring zone: Ag-27; Cd-36; Cr-12; Cu-20; Hg-23; Ni-5.4; Pb-17; Zn-7.7.     

Effects of the closure of a major sewage outfall on sublittoral, soft sediment benthic communities

The present study examines the benthos within western inner Swansea Bay (Wales, UK), for the period before, during and immediately after the cessation of a major, sewage discharge from Mumbles Head. There have been significant improvements in seawater quality and changes in the species composition of the benthic communities following the cessation of the sewage discharge. There has been an increase in the diversity of deposit feeders, especially the amphipods, and a decrease in the diversity of the filter feeders, especially the polychaetes. Changes are not attributable either to sediment organic matter content or to gross changes in sediment type, but are related to the significant reduction in suspended particulate organic material and sewage contaminants discharged to the Bay. A recovery model has been proposed to describe how soft sediment benthic communities in a shallow, sublittoral, high tidal energy environment respond to the abrupt cessation of a major sewage discharge.     

Box coring artifacts in sediments affected by a waste water outfall

Variations in porosity of surface sediments are often the major cause of sediment loss during gravity and box coring. Sediments with a high content of organic matter usually have higher porosity, and thus, lower resistance (strain) towards mechanical disturbance. Here, we demonstrate that box coring artifacts (i.e. sediment loss and core shortening) can be produced in sediments from the Palos Verdes (PV) shelf, which in the past had received relatively high loads of organic carbon (OC) enriched particulate matter originating from the Whites Point outfall that had created a high porosity layer at depth. This has been overlooked as a possibility for obtaining low estimates of sediment and pollutant accumulation rates. Since any such sediment loss during coring can lead to serious underestimates of sedimentation rates, our results here may have important implications for any attempts at reconstructing pollutant fluxes and histories in these coastal marine sediments.     

Metal contamination of sediments associated with deepwater ocean sewage outfalls, Sydney, Australia

The New South Wales Environment Protection Authority has recently completed a programme to evaluate the impact on near-shore shelf sediments, following the commissioning of three new deepwater sewage outfalls off Sydney, Australia. These outfalls discharge a total of around 1300 ML day⁻¹ of primary treated sewage derived from domestic and industrial sources. The study compared three locations that were close to the outfalls (likely impacted) and three locations far from the outfalls (likely non-impacted). Four zones were sampled within each location to provide estimates of spatial variability. Three samples of surface sediment were collected from each zone at six monthly intervals over a three year period which encompassed the commissioning of the outfalls. The results of the study suggest that, associated with the commissioning of the three deepwater outfalls, there has not been a significant effect on the concentration of trace metals in the sediments surrounding the outfalls. The concentrations of trace metals in the whole sediment generally were close to the world-wide background levels quoted in the literature, and generally reflected the distribution pattern of the sedimentary fines (< 62.5 mm). When compared to a number of sediment quality guidelines, the concentrations of trace metals were found to be below a level considered to have the potential to cause biological effects or (in the case of As, Ni, Cr) at a level that could be tolerated by the majority of benthic organisms.     

Effects of the North Head deep-water sewage outfall on nearshore coastal reef macrobenthic assemblages

The macrobenthos on the coastal reefs near the North Head deep-water outfall were sampled nine times over a 3 year period to determine whether patterns in diversity and abundance were affected by the outfall. The assemblages were sampled using an asymmetrical after control/impact design (ACI). Ten replicate quadrats at each of three sites nested within each of three locations were photographed using a jump camera. These photographs were sampled to provide estimates of the number and abundance of major taxa and abundances of individual species. Significant interactions between outfall vs control through time were detected for the total number of species, bryozoans, cnidarians and the abundances of a silt matrix and two species of bryozoans. Smaller scale interactions among sites through time occurred for the abundances of total fauna, sponges and an ascidian species representing some evidence for the effect of the outfall at these smaller spatial scales. This paper summarizes the correlative evidence of effects from the outfall.     

Heavy metal contamination in coastal sediments and soils near the Brazilian Antarctic Station, King George Island

This paper investigates the natural and anthropogenic processes controlling sediment chemistry in Admiralty Bay, King George Island, Antarctica, emphasizing the area affected by the Brazilian Antarctic Station Comandante Ferraz (Ferraz). Total and bioavailable concentrations of sixteen elements were determined in 32 sediment and 14 soils samples. Factor analysis allowed us to distinguish three groups of samples: (1) Ferraz sediments, with higher content of total trace metals and organic matter; (2) control sediments, with intermediate characteristics; (3) Ferraz soils, with higher bioavailability of most metals due to its oxidizing condition and low organic matter content. Major elements such as Fe, Al, Ca and Ti presented similar levels in all three groups. Enrichment factor calculations showed that paints, sewage and petroleum contamination enhanced metal concentrations in Ferraz surface sediments as follows: B, Mo, and Pb (>90%); V and Zn (70-80%); Ni, Cu, Mg, and Mn (30-40%). Despite evidence of contamination in these sediments, the low bioavailability, probably caused by iron-sulfide, indicates small environmental risks.     

Changes in macroalgal communities in the vicinity of a Mediterranean sewage outfall after the setting up of a treatment plant

Benthic macroalgal communities of the upper rocky sublittoral were studied in 1995-1996 in the vicinity of the Marseille (Mediterranean, France) sewage outfall, 8 years after the setting up of a wastewater treatment plant and compared to a previous study carried out in 1972-1974. The number of taxa has increased, a clear stational and seasonal gradient of differentiation of the vegetation appeared, and a turf of ephemeral species is taking place of Corallina elongata at sites close to the outfall. These changes may be due to a decrease in pollutant load, the discharge of ferric chlorates used in the treatment process. However, the overall change is much less conspicuous than that described for deeper soft bottom communities, in particular the Cystoseira amantacea community is not still restored. Biological traits of this species (short distance dispersal) and the nature of most pollutants removed from the effluent (solids and organic matter) may explain this phenomenon.     

Medium-term responses of rocky bottoms to sewage discharges from a deepwater outfall in the NE Atlantic

An investigation on the effects of deepwater outfall discharges on the status of rocky reef communities was carried out. The sanitation system was found to be an environmentally suitable option for the protection of those habitats situated in high energy coastal environments. Sediments occurring between the predominating rocky substrates showed low values of the fine fraction (<63microm) and organic matter content. In addition, high average concentrations of Cd, Hg and Zn were found in these sediments, though these values were similar to those registered in non-affected sites, far away from the outfall. On the other hand, those assemblages typical of hard substrates that settled near the outfall showed an increase in total richness and abundance of macroinvertebrates. Moreover, the average number of species of each taxonomic group, a good indicator of the maintenance of the previous trophic structure, only varied considerably over time at the rip-rap protection. In a global context, those changes were not directly related to the discharge disturbances, but to the natural variability or the successional processes occurring within those communities. Only communities dwelling in the rip-rap protection area were affected by the proximity of the discharges.     

Subtidal assemblages on rocky reefs at a cliff-face sewage outfall (North Head, Sydney, Australia): What happened when the outfall was turned off?

For many years, sewage was continuously discharged via inshore outfalls into shallow subtidal habitats around Sydney (New South Wales). In 1990, deepwater ocean outfalls were commissioned and inshore discharge ceased. This study examined the assemblage of organisms found on subtidal cliffs at one inshore outfall to examine differences in, or recovery by, the biota when sewage was no longer discharged. This assemblage was primarily composed of filter-feeding animals (sponges, ascidians, bryozoans, anthozoans) and encrusting algae. Differences and changes in the assemblages at a number of different spatial scales, relative to the assemblages at two reference locations, were examined four times over a 20 month period. Although most taxa showed significant changes over the study period, most of these were unpredictable and varied interactively according to the taxon, plot, depth and location. For most measures, however, the location where sewage had been released lay within the natural variability shown by the reference locations. The implications of these findings are discussed with respect to other studies on the effects of sewage on intertidal and shallow subtidal habitats.     

Serious mercury contamination of sediments in a Norwegian semi-enclosed bay

Thirteen surface sediment samples from a shallow, semi-enclosed bay, Gunnekleivfjorden, South-West Norway, were analysed for total mercury. The concentrations ranged between 90 and 350 ppm dried sediment. The median value (250 ppm mercury) is more than twice the median value of sixteen sediment samples collected in Minamata Bay in 1963. The surface area of Gunnekleivfjorden is approximately 1 km², implying that minimum 10 tons of mercury is accumulated in the upper 5 cm of the sediments of the bay. The extensive contamination is caused by discharge of inorganic mercury from a chlor-alkali plant during the last 25 years.     

Nutrient dynamics in seawater column in the vicinity of Piran submarine sewage outfall (North Adriatic)

Variations of nitrogen and phosphorus concentrations in the vicinity of Piran (North Adriatic) submarine sewage outfall were studied as well as the treatment plant operation. On the basis of the data it was concluded that the influence of the outfall to the nutrient level in that area is negligible. In comparison the data from the shallow organically polluted water in the inner part of the Bay of Koper are reported.     

PAH contamination of western Irish Sea sediments

Concentrations of the sum of 15 PAHs in 22 surficial sediment samples from the western Irish Sea ranged from below 100 ng g⁻¹ in sandy sediments to a maximum of 1422 ng g⁻¹ in the centre of the mud basin. The concentrations are typical of coastal shelf sediments, but greater than those observed for aquatic sediments remote from known anthropogenic sources. Organic C and the % sediment <15 μm were positively correlated with ΣPAH. ΣPAH was normalised to organic C and particle size (i.e. expressed as ΣPAH/C^org and ΣPAH/%<15 μm) and significant relationships were still observed with organic C and %<15 μm. The results are discussed in the context of using organic C to normalise concentrations of PAHs to assess contamination levels in sediments.     

Effect of sewage effluent on the sediments of Nordåsvatnet (a land-locked fjord), Norway

Nordåsvatnet is a land-locked anoxic fjord along the west coast of Norway which is used as a natural recipient of untreated domestic sewage. The study of four core sediments collected from the heavily polluted basin of the fjord reflects the enrichment of surface sediments by Fe, Mn, Cu, Zn and organic matter. This surface enrichment is entirely attributed to the anthropogenic input.     

Characterization of phosphorus sorption on the sediments of Yangtze River Estuary and its adjacent areas

This paper studied the kinetics, isotherm and thermodynamics of phosphorus sorption onto the sediments of the Yangtze River estuary and its adjacent waters, as well as the sediments' compositions and physicochemical properties. The process could be described well by a two-compartment first order equation. The sorbed phosphorus mainly consisted of Ex-P and Fe-P, with Ex-P being the dominant. The equilibrium isotherms could be fitted well with a modified Langmuir equation. The calculations of the thermodynamic parameters indicated that the process was spontaneous and exothermic. The CEC and the fractions of clay, calcite and organic matter were correlated with the sorption parameters, while the surface proton charge of the sediments was significantly negatively correlated with them. Considering the kinetics and phosphorus forms changes during the process, the sorption in our study could be considered that the physical process plays an important role.     

Polychlorinated biphenyls in sewage sludge and sediments of the New York Bight

Sediments of the New York Bight were analysed for polychlorinated biphenyls (PCB) and found to be heavily contaminated by such substances. The highest concentrations are adjacent to an offshore sludge dump zone, implying that the primary source of PCBs is sewage sludge in the area under consideration. Widespread transport of PCBs out of the bight is not evident as the area of contamination is limited to areas of mud accumulation. The PCB profile in a core of these mud facies can be historically correlated to the commercial production of PCBs.