Bottom sediments of the Arabian Gulf--III. Trace metal contents as indicators of pollution and implications for the effect and fate of the Kuwait oil slick

The trace metal contents of 71 core samples collected in 1992 from the bottom sediments of the Arabian Gulf are used to determine the regional distribution of concentration and pollution levels of these substances in the region. Chronic contamination was recorded in seven locations: the northwestern area (Fe), the northeastern area (Fe, V and Ni), the north-central area (V and Ni), the central area (Fe, Pb, V and Ni), the south-central area (Cu), the eastern area (Cu) and the southeastern area (Fe, V and Ni). Present-day contamination was identified in three locations only: the north-central area (V), the central area (Pb, V and Ni) and the southeastern area (Fe, V and Ni). Diversified natural and anthropogenic inputs may have provided the sources of this contamination. The V/Ni ratios of recent marine sediments cannot be used in identifying oil spillages or in oil-sediment correlation studies. Positive correlations are found between increasing trace metal concentration and decreasing carbonate content and grain size, verifying that adsorption onto muds is the primary mechanism of trace metal concentration in marine sediments. Correlations with TOC (total organic carbon) contents indicate that organic matter is a significant concentrator only in the case of Pb and Cu. With the exception of the Fe contamination in the northwest area due to river transport, all chronic and present-day trace metal concentrations are within the permissible natural background levels in the western offshore areas, including the two areas thought to be polluted by the Kuwait oil slick, thereby supporting the idea that airborne fallout from oil fires was deposited in a limited coastal area between Kuwait and Bahrain, and verifying that the oil slick had minimal effect on the state of pollution by trace metals in the Arabian Gulf.     

Two years of oil disaster in the Arabian Gulf

In January–February 1991, about 1 million m³ of crude oil were released into the Arabian Gulf as a means of ecological warfare. A stretch of 644 km along the Saudi Arabian coast was heavily polluted over a width between a few meters and more than one kilometer. In four studies performed between March 1991 and April 1993 the state of representative areas of the affected coast was examined with the result that only minor changes were found in those oiled zones which are seldom inundated by the tides. Technical measures up to 1993 did not exceed the test level. A biological regeneration process is in progress which was not recognized as such in analyses of previous coastal oil pollution. Cyanobacterial mats, containing hydrocarbon-degrading bacteria, grow on oiled sediments which are regularly reached by tidal water. Shrinking and fracturing of the stable tar crusts starts a process of loosening and degrading of aged hydrocarbons.     

Petroleum hydrocarbons in the nearshore marine sediments of the United Arab Emirates

The concentrations of total petroleum hydrocarbons (TPH) were determined in nearshore sediment samples collected from 28 sampling sites along the United Arab Emirates shorelines on the Arabian Gulf, the Gulf of Oman and seven major creeks (khors) extending from them. Concentrations were highly variable and ranged between <0.4 and 212 microg g(-1) dry weight, and the highest values obtained were in the top sediment (1 cm) layer near a fuel filling station and port areas. Locally high levels of TPH were found in Dubai, Sharjah and Ajman semi-enclosed creeks where boat activities and land-based wastewater discharges are most common. Data support the premise that port activities, fuel filling stations and land-based wastewater discharges are major sources of pollution in the study area. Correlations with sediment grain size, total organic carbon (TOC) and distance from pollution sources are discussed.     

Oil spill in the Rio de la Plata estuary, Argentina: 1. Biogeochemical assessment of waters, sediments, soils and biota

Aliphatic (ALI) and aromatic (ARO) hydrocarbon concentrations, composition and sources were evaluated in waters, sediments, soils and biota to assess the impact of approximately 1000 tons of oil spilled in Rio de la Plata coastal waters. Total ALI levels ranged from 0.4-262 microg/l in waters, 0.01-87 microg/g in sediments, 5-39 microg/g in bivalves, 12-323 microg/g in macrophytes to 948-5187 microg/g in soils. ARO varied from non-detected 10 microg/l, 0.01-1.3 mug/g, 1.0-16 microg/g, 0.5-6.9 microg/g to 22-67 microg/g, respectively. Offshore (1, 5, 15 km) waters and sediments were little affected and contained low background hydrocarbon levels reflecting an effective wind-driven transport of the slick to the coast. Six months after the spill, coastal waters, sediments, soils and biota still presented very high levels exceeding baseline concentrations by 1-3 orders of magnitude. UCM/resolved aliphatic ratio showed a clear trend of increasing decay: coastal waters (3.3) < macrophytes (6.7) < soils (9.4) < offshore sediments (13) < coastal sediments (17) < clams (52). All environmental compartments consistently indicated that the most impacted area was the central sector close to Magdalena city, specially low-energy stream embouchures and bays which acted as efficient oil traps. The evaluation of hydrocarbon composition by principal component analysis indicated the predominance of biogenic (algae, vascular plant cuticular waxes), background anthropic, pyrogenic and diagenetic hydrocarbons, offshore and in non-impacted coastal sites. In contrast, polluted stations presented petrogenic signatures characterized by the abundance of isoprenoids, low molecular weight n-alkanes and methylated aromatics in different stages of alteration. The petrogenic/biogenic ratio ( n-C23) and petrogenic/pyrogenic relationship (methylated/unsubstitued PAH) discriminated the samples according to the different degree of impact. The following paper present the results of the study of the progress of hydrocarbon disappearance in sediments and soils 13 and 42 months after the spill.     

GC and GC-MS characterization of crude oil transformation in sediments and microbial mat samples after the 1991 oil spill in the Saudi Arabian Gulf coast

The massive oil discharge in the Saudi Arabian coast at the end of the 1991 Gulf War is used here as a natural experiment to study the ability of microbial mats to transform oil residues after major spills. The degree of oil transformation has been evaluated from the analysis of the aliphatic and aromatic hydrocarbons by gas chromatography (GC) and GC coupled to mass spectrometry (GC-MS). The oil-polluted microbial mat samples from coastal environments exhibited an intermediate degree of transformation between that observed in superficial and deep sediments. Evaporation, photo-oxidation and water-washing seemed to lead to more effective and rapid elimination of hydrocarbons than cyanobacteria and its associated microorganisms. Furthermore, comparison of some compounds (e.g. regular isoprenoid hydrocarbons or alkylnaphthalenes) in the oil collected in the area after the spill or in the mixtures retained by cyanobacterial growth gave rise to an apparent effect of hydrocarbon preservation in the microbial mat ecosystems.     

Contamination of River Kymijoki sediments with polychlorinated dibenzo-p-dioxins, dibenzofurans and mercury and their transport to the Gulf of Finland in the Baltic Sea

Kymijoki, the fourth largest river in Finland, has been heavily polluted by pulp mill effluents as well as the chemical industry. Up to 24,000 ton of wood preservative, chlorophenol known as Ky-5, was manufactured in the upper reaches of the river, an unknown amount of which was discharged into the river between 1940 and 1984. Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) occurred as impurities in the final Ky-5 product. The PCDD/F concentrations and burden in the river sediments were studied and the transport of PCDD/Fs from contaminated sites downstream and into the Gulf of Finland in the Baltic Sea was estimated. More than 190 sediment cores were sampled to estimate the volume of contaminated sediments and the total PCDD/F burden. The transport of PCDD/Fs was estimated using sediment traps placed at several sites. The survey revealed that sediments in the river were heavily polluted by PCDD/Fs, the main toxic congener being 1,2,3,4,6,7,8-heptachlorodibenzofuran, a major contaminant in the Ky-5 product. The mean total concentration at the most polluted river site downstream from the main source was 42000 microg kg(-1) d.w. (106 microg I-TEQ kg(-1)). The elevated concentrations in the coastal region and the present estimated transport from the River Kymijoki confirm earlier assessments that the river is a major source of PCDD/F for the Gulf of Finland.     

Oil pollution in Qatari coastal sediments

The present study focuses on the areal distribution of petroleum hydrocarbons in the Qatari coastal-belt sediments. Total petroleum hydrocarbons were quantified by ultra-violet fluorescence spectroscopy (UVF) for eighteen surface-sediment samples collected from six different areas along the Qatari coastline. Petroleum hydrocarbons are ubiquitous in the sediments studied, and their concentrations ranged from 48 microg g(-1) dw Kuwaiti-oil equivalents on the eastern side of the peninsula to 248 microg g(-1) dw Kuwaiti-oil equivalents on the western side. Concentrations of petroleum hydrocarbons in Qatari coastal sediments were very heterogeneous from one area to another and showed a decreasing sequence in the following order: Al-Zubarah (215 microg g(-1) dw) > Dukhan (143 microg g(-1) dw) > Ruwais (108 microg g(-1) dw) > Umm Said (89 microg g(-1) dw) > Fuwairet (81 microg g(-1) dw) > Doha (5 microg g(-1) dw Kuwaiti-crude-oil equivalents). This could indicate that the possible sources of oil on the Qatari coasts are mainly external on the western side and local on the eastern one. No significant correlation was found between organic C (0.6-1.4%) and petroleum-hydrocarbon concentrations.     

Industrial plastic on the southern beaches of the Arabian Gulf and the western beaches of the Gulf of Oman

The increasing production and use of plastic in the Arabian Gulf combined with shipping and waste disposal practices, have increased the concentration of plastic particles on the sea's surface and beaches. The objective of this investigation was to provide an assessment of the abundance, distribution, potential sources and significance of industrial plastic on the western beaches of the United Arab Emirates on the Arabian Gulf and on the eastern beaches on the Gulf of Oman. The abundance of stranded plastic pellets was highly uneven. By early 1992 alarming levels of fresh plastic pellets were noticed on the Arabian Gulf beaches of the UAE. Large numbers of 25 kg sacks of white plastic spherules manufactured by (SABIC) in Jubail, Saudi Arabia were washed ashore. When compared to the west coast on the Arabian Gulf, the east coast on the Gulf of Oman exhibited much lower levels of plastic pellets. When compared to other parts of the world, the beaches of the UAE on the Arabian Gulf are considered to be heavily polluted with industrial plastic.     

Burial,exportation and degradation of acyclic petroleum hydrocarbons following a simulated oil spill in bioturbated Mediterranean coastal sediments

A field study was conducted in a French Mediterranean littoral (Gulf of Fos) in order to determine the role of bioturbation processes during the bioremediation of oil-contaminated sediments. Inert particulate tracers (luminophores) and Arabian light crude oil were deposited at the surface of sediment cores incubated in situ for 2, 6 and 12 months. After incubation, luminophores and hydrocarbons presented roughly similar depth distributions in the sediment, showing a continuous burial of material until 55 mm depth. Short-chain (< or = n-C25) n-alkanes were totally removed from the sedimentary column after 6 months, whereas approximately 20% of heavier n-alkanes (e.g. n-C30) and of isoprenoid hydrocarbons (pristane (Pr) and phytane (Ph)) remained at the end of the experiment. The determination of the degradation constant and the turn-over rate of individual hydrocarbon indicated that C17-25 n-alkanes were degraded two to three times faster than longer homologues and than pristane and phytane. Using the 17alpha,21beta-C30-hopane as an internal inert reference, we could demonstrate that, after 12 months of in situ incubation, 55% of the losses of the n-alkanes < or = C25 and 35% of the losses of the heavier n-alkanes and of Pr and Ph were due to biodegradation processes. These results demonstrate that the activity of benthic organisms can have a significant influence on the qualitative and quantitative fate of acyclic hydrocarbons following a petroleum contamination in marine coastal sediments.     

Toxicity of crude oil to the mayfly, Hexagenia bilineata (Ephemeroptera: Ephemeridae)

Effects of crude oil on survival and behavior of the mayfly Hexagenia bilineata were evaluated in laboratory studies. Mayfly nymphs were exposed to the water soluble and oil residue fractions of crude oil. Mayfly survival was not reduced by a 96-h exposure to either the water soluble fraction or the oil residue mixed with sediment. However, significant mortality did result from a 21-day exposure to oil residue mixed with sediment at concentrations as low as 500 microg g(-1). Survival was also reduced after a 21-day exposure to oil-contaminated sediments (1905 microg g(-1)) collected 6 weeks after a crude oil spill in the Chariton River, Missouri. In a behavioral test measuring habitat exclusion, organisms did not avoid contact with sediment containing oil residue (50-800 microg g(-1)). Collectively, results from these studies indicate that exposure to oil residue in sediment will reduce survival of H. bilineata in the laboratory and may reduce survival in the environment for 6 weeks or more after an oil spill.     

Environmental photooxidation of dibenzothiophenes following the Amoco Cadiz oil spill

Photooxidation products of dibenzothiophenes (sulfur containing petroleum heteroaromatic hydrocarbons) were characterized in an oil slick sample obtained from a field location following the AMOCO CADIZ oil spill. The same oxidation products were formed in the laboratory by the photooxidation of a medium Arabian crude oil which contained the identical precursor hydrocarbons. Analytical techniques included fractionation by liquid/solid chromatography and characterization using high resolution gas chromatography-mass spectrometry. To the best of the author's knowledge, this represents the first reported instance for the formation of photooxidation products following an actual oil spill. A comparison of the quantities of various oxidation products was carried out by quantitative mass spectrometry using extracted ion current profiles of dibenzothiophenes and their corresponding sulfoxides. The geochemical and physiological implications of such photooxidation processes are also discussed.     

Ex situ bioremediation of a soil contaminated by mazut (heavy residual fuel oil)--a field experiment

Mazut (heavy residual fuel oil)-polluted soil was exposed to bioremediation in an ex situ field-scale (600 m(3)) study. Re-inoculation was performed periodically with biomasses of microbial consortia isolated from the mazut-contaminated soil. Biostimulation was conducted by adding nutritional elements (N, P and K). The biopile (depth 0.4m) was comprised of mechanically mixed polluted soil with softwood sawdust and crude river sand. Aeration was improved by systematic mixing. The biopile was protected from direct external influences by a polyethylene cover. Part (10 m(3)) of the material prepared for bioremediation was set aside uninoculated, and maintained as an untreated control pile (CP). Biostimulation and re-inoculation with zymogenous microorganisms increased the number of hydrocarbon degraders after 50 d by more than 20 times in the treated soil. During the 5 months, the total petroleum hydrocarbon (TPH) content of the contaminated soil was reduced to 6% of the initial value, from 5.2 to 0.3 g kg(-1) dry matter, while TPH reduced to only 90% of the initial value in the CP. After 150 d there were 96%, 97% and 83% reductions for the aliphatic, aromatic, and nitrogen-sulphur-oxygen and asphaltene fractions, respectively. The isoprenoids, pristane and phytane, were more than 55% biodegraded, which indicated that they are not suitable biomarkers for following bioremediation. According to the available data, this is the first field-scale study of the bioremediation of mazut and mazut sediment-polluted soil, and the efficiency achieved was far above that described in the literature to date for heavy fuel oil.     

The long-term environmental behaviour of strontium and barium released from former mine workings in the granites of the Sunart region of Scotland, UK

The concentrations of strontium and barium have been measured in water, sediment and the shells of mussels (Mytilus edulis) from a river system in the Sunart region of Scotland, UK. The aim was to establish the fate and mobility of these elements, which are slowly being released from old mine workings on the Strontian granites. Enhanced strontium (1500-2000 microg l(-1) and 250-290 microg l(-1)) and barium concentrations (316 microg l(-1) and 83 microg l(-1)) were found in the waters originating from the two mine drains studied. Both element were also found at significant levels in the river sediments taken from the vicinity of each drainage site (Sr: 225 microg g(-1) and 120-125 microg g(-1); Ba: 1380 microg g(-1) and 126-170 microg g(-1)). The data suggests that the sediments are acting as a reservoir for these group II cations from where they become distributed throughout the river system. Strontium is found to be incorporated into the shells (3.16-3.46 microg g(-1)) and pearls (3.57 microg g(-1)) of the blue mussel, located at the estuarine margin some 10 km downstream, at values close to the maximum expected (3.3% by weight of the calcium content). The study presents a view of the fate of barium and strontium in a river system over a prolonged period of time. As such it provides valuable information for studies that seek to model the impact of the accidental release of barium and strontium (including the important radionuclide 90Sr) into the environment.     

A microbiological study of the self-cleaning potential of oily Arabian Gulf coasts

Background, aim, and scope  

Due to the active production and transport of crude oil in the Arabian Gulf region, the Arabian Gulf coasts are routinely polluted with oil. Therefore, such coasts have been subject of studies aiming at assessing the roles of indigenous microbial consortia in cleaning these environments. In the present study, epilithic microbial communities along Kuwait coasts were studied for their oil degradation potential.     

Bioaccumulation of nickel and vanadium by clams (Meretrix meretrix) living in different salinities along the Saudi coast of the Arabian Gulf

The objective of this study was to investigate bioaccumulation of nickel (Ni) and vanadium (V) in clams living in different salinity regimes along the Saudi coast of the Arabian Gulf. Several hundred clam (Meretrix meretrix), sediment, and seawater samples were collected from 12 locations. Concentrations of Ni and V were determined in these samples using an inductively coupled argon plasma analyzer. Concentrations of Ni and V in the clams varied between 0.35 and 2.61 mg kg(-1) and between 0.13 and 0.35 mg kg(-1) wet tissue, respectively. Analysis of variance of the data revealed significant (P<0.01) inter- and intra-station variations in Ni concentrations in clams. In contrast, the mean concentration of V in clams from all the stations were statistically similar. Correlation between the biometric characteristics of clams and Ni and V concentrations were not statistically significant. Significant (P<0.05) geographical variations in Ni and V concentrations in the sediment samples were found, with relatively higher concentrations in the northern part of the Gulf where there are many oil fields. Ni and V in the sediments were significantly (P<0.05) correlated, suggesting a common contamination source for these elements. Interactions between Ni and V in clams and sediment were poor.     

Large-scale risk assessment of polycyclic aromatic hydrocarbons in shoreline sediments from Saudi Arabia: Environmental legacy after twelve years of the Gulf war oil spill

A large-scale assessment of polycyclic aromatic hydrocarbons (PAHs) from the 1991 Gulf War oil spill was performed for 2002-2003 sediment samples (n = 1679) collected from habitats along the shoreline of Saudi Arabia. Benthic sediment toxicity was characterized using the Equilibrium Partitioning Sediment Benchmark Toxic Unit approach for 43 PAHs (ESBTU_FCV,43). Samples were assigned to risk categories according to ESBTU_FCV,43 values: no-risk (≤1), low (>1-≤2), low-medium (>2-≤3), medium (>3-≤5) and high-risk (>5). Sixty seven percent of samples had ESBTU_FCV,43 > 1 indicating potential adverse ecological effects. Sediments from the 0-30 cm layer from tidal flats, and the >30-<60 cm layer from heavily oiled halophytes and mangroves had high frequency of high-risk samples. No-risk samples were characterized by chrysene enrichment and depletion of lighter molecular weight PAHs, while high-risk samples showed little oil weathering and PAH patterns similar to 1993 samples. North of Safaniya sediments were not likely to pose adverse ecological effects contrary to sediments south of Tanaqib. Landscape and geomorphology has played a role on the distribution and persistence in sediments of oil from the Gulf War.     

Accumulation of polychlorinated biphenyls in sediments of the Venice Lagoon and the industrial area of Porto Marghera

Sediment cores, collected at seven sites in the Venice Lagoon and within the canals of the industrial area were analyzed for polychlorinated biphenyls (PCBs) in order to assess the chronology of pollution and its present trends. The surficial concentration of PCBs is very high (more than 2049 microg kg(-1)) only in the Brentella Canal, probably due to a very recent contaminating episode. Very high values downcore (up to 41,639 microg kg(-1)) can be found in different parts of the industrial area, especially in the canals Lusore-Brentelle and Salso. Lagoon samples are much less contaminated (2.7-123 microg kg(-1)), being influenced only occasionally by polluted sediments resuspended from the canals. Sediment chronology shows that the delivery of contaminants peaked in the 1970s-early 1980s, decreasing since at most sites. Congener profiles distinguish PCBs in two main categories: heavy congeners characterize a baseline pollution, probably due to a large variety of sources within the lagoon system, whereas a mixture of light PCBs was discharged into the canals Brentella and Salso.     

Flux estimates and sedimentation of polychlorinated naphthalenes in the northern part of the Baltic Sea

The concentrations and fluxes of polychlorinated naphthalenes (PCNs) were measured in surface sediments, and settling particulate matter collected in sediment traps, at two coastal and two offshore sampling stations in the Gulf of Bothnia, northern Baltic Sea, Sweden. The PCN concentrations (of tetra- to hepta-chloro congeners) in the surface sediments ranged from 0.27 to 2.8 ng/g dry weight and were of the same order of magnitude as background concentrations reported previously in Europe. The PCN fluxes in the southern basin (0.93 and 0.86 microg/m2/year) of the Gulf of Bothnia were higher than those in the northern basin (0.58 and 0.49 microg/m2/year); they were also higher near the coast than in the open sea. These PCN fluxes are similar to the pre-industrial levels determined from lake sediments in northwest England. The PCN homologue distribution changed from a relatively even distribution in samples collected near the coast, to TeCNs dominating in the samples from the open sea. This indicates that higher chlorinated PCNs are deposited and retained in sediments to a higher degree near the coast. The total annual deposition of PCNs in sediments in the Gulf of Bothnia was estimated to be 91 kg/year.     

Comparing sediment quality in Spanish littoral areas affected by acute (Prestige, 2002) and chronic (Bay of Algeciras) oil spills

The quality of sediments collected from two areas of the Spanish coast affected by different sources of contaminants has been compared in this study. The areas studied are the coast of Galicia affected by the oil spill from the tanker Prestige (November 2002) and the Gulf of Cádiz which suffers continuous inputs of contaminants from industries located in the area and from oil spills. Contamination by several chemicals (metals, PCBs and PAHs) that bind to sediments was analyzed, and two toxicity tests (Microtox) and amphipod 10-day bioassay) were conducted. PAHs were identified as the compounds responsible for the toxic effects. Results show differences between an acute impact related to the sinking of the tanker Prestige and the chronic impact associated with continuous oil spills associated with the maritime and industrial activities in the Bay of Algeciras, this being the most polluted part of the two coastal areas studied in this work.     

Effects of petroleum contamination on soil microbial numbers, metabolic activity and urease activity

The influence of petroleum contamination on soil microbial activities was investigated in 13 soil samples from sites around an injection water well (Iw-1, 2, 3, 4) (total petroleum hydrocarbons (TPH): 7.5-78 mg kg⁻¹), an oil production well (Op-1, 2, 3, 4, 5) (TPH: 149-1110 mg kg⁻¹), and an oil spill accident well (Os-1, 2, 3, 4) (TPH: 4500-34 600 mg kg⁻¹). The growth rate constant (μ) of glucose stimulated organisms, determined by microcalorimetry, was higher in Iw soil samples than in Op and Os samples. Total cultivable bacteria and fungi and urease activity also decreased with increasing concentration of TPH. Total heat produced demonstrated that TPH at concentrations less than about 1 g kg⁻¹ soil stimulated anaerobic respiration. A positive correlation between TPH and soil organic matter (OM) and stimulation of fungi-bacteria-urease at low TPH doses suggested that TPH is bound to soil OM and slowly metabolized in Iw soils during OM consumption. These methods can be used to evaluate the potential of polluted soils to carry out self-bioremediation by metabolizing TPH.