Contamination of the biological compartment in the Seine estuary by Cd, Cu, Pb, and Zn

A study of contamination of the biological compartment of the Seine estuary was carried out by measuring the concentrations of cadmium (Cd), copper (Cu), lead (Pb), and zinc (Zn) in 29 estuarine and marine species belonging to 6 phyla. Species came from three main biological zones of the estuary: the Seine channel (copepods, mysids, shrimps, and fish), the intertidal mudflats (Macoma balthica community), and the subtidal mudflats (Abra alba community). Two fish species, the bass (Dicentrarchus labrax) and the flounder (Platichthys flesus), were also selected for analyses. A comparison of metal concentrations in estuarine species of the Seine with those found in the same species collected on contaminated and non-contaminated sites showed a contamination of the estuary by Cu, Zn, and Pb. For Cd, the contamination is mainly observed in bivalves, although the concentrations observed were low and less than 2 μg g^?1 d.w. High concentrations of Cu were found in copepods, shrimps, and fish. Pb contamination was mainly found in species living in the Seine channel where the copepodEurytemora affinis shows an average concentration of 22 μg g^?1 d.w. High concentrations of Pb (>10 μg g^?1 d.w.) were found in deposit-feeders benthic invertebrates. Elevated levels of Zn were seen in all species collected in the Seine estuary, including fish and in particular small flounder. The concentrations of Cd, Cu, Pb, and Zn found in edible estuarine species (shrimp and fish) were in the same order of magnitude than those found in fish and shrimps fished along the French coast.     

Heavy metal pollution of coastal river sediments, north-eastern New South Wales, Australia: lead isotope and chemical evidence

 Heavy metal and metalloid concentrations within stream-estuary sediments (<180-μm size fraction) in north-eastern New South Wales largely represent natural background values. However, element concentrations (Ag, As, Cd, Cr, Cu, Hg, Ni, Pb, Sb, Zn) of Hunter River sediments within the heavily industrialized and urbanized Newcastle region exceed upstream background values by up to one order of magnitude. High element concentrations have been found within sediments of the Newcastle Harbour and Throsby Creek which drains into urbanized and light industry areas. Observed Pb enrichments and low ²⁰⁸Pb/²⁰⁴Pb, ²⁰⁷Pb/²⁰⁴Pb and ²⁰⁶Pb/²⁰⁴Pb ratios are likely caused by atmospheric deposition of Pb additives from petrol and subsequent Pb transport by road run-off waters into the local drainage system. Sediments of the Richmond River and lower Manning, Macleay, Clarence, Brunswick and Tweed River generally display no evidence for anthropogenic heavy metal and metalloid contamination (Ag, As, Cd, Cr, Cu, Hg, Ni, Pb, Sb, Zn). However, the rivers and their tributaries possess localized sedimentary traps with elevated heavy metal concentrations (Cu, Pb, Zn). Lead isotope data indicate that anthropogenic Pb provides a detectable contribution to investigated sediments. Such contributions are evident at sample sites close to sewage outlets and in the vicinity of the Pacific Highway. In addition, As concentrations of Richmond River sediments gradually increase downstream. This geochemical trend may be the result of As mobilization from numerous cattle-dip sites within the region into the drainage system and subsequent accumulation of As in downstream river and estuary sediments. Received: 5 September 1997 · Accepted: 4 November 1997     

Heavy metal distribution and accumulation in two Spartina sp.-dominated macrotidal salt marshes from the Seine estuary (France) and the Medway estuary (UK)

The upper intertidal zone, and salt marshes in particular, have been shown by numerous authors to be effective medium to long-term storage areas for a range of contaminants discharged or transported into the estuarine environment. A detailed understanding of the specific controls on the trapping and storage of contaminants, however, is absent for many estuarine systems. This paper examines heavy metal distribution and accumulation in two contrasting Spartina sp.-dominated macrotidal salt marsh systems – a rapidly prograding, relatively young marsh system at the Vasiere Nord, near the mouth of the Seine estuary, France, and a more mature, less extensive marsh system in the Medway estuary, UK. The spatial distribution of the heavy metals Zn, Cu, Pb, Ni and Co is assessed and compared in both systems via detailed surface sampling and analysis, while the longer-term accumulation of these metals and its temporal variability is compared via analysis of dated sediment cores. Of the two sites studied, the more extensive marsh system at the Vasiere Nord in the Seine estuary shows a clear differentiation of heavy metals across the marsh and fronting mudflat, with highest metal concentrations found in surface sediments from the more elevated, interior marsh areas. At Horrid Hill in the Medway estuary, the spatial distribution of heavy metals in surface sediments is more irregular, and there is no clear relationship between heavy metal concentration and site elevation, with average concentrations similar in the marsh and fronting mudflats. Sediment core data indicate that the more recent near-surface sediments at Horrid Hill are clearly more contaminated than those at greater depth, with most heavy metal contamination confined to the upper 20 cm of the sediment column (with peak metal input in the late 1960s/early 1970s). In contrast, due to extremely rapid sediment accretion at the mouth of the Seine, heavy metal distribution with depth at the Vasiere Nord site is relatively erratic, with metal concentrations showing a general increase with depth. These sediments provide little information on temporal trends in heavy metal loading to the Seine estuary. Overall, heavy metal concentrations at both sites are within typical ranges reported for other industrialised estuaries in NW Europe.     

Heavy metal distribution in surface sediments of the Tirumalairajan river estuary and the surrounding coastal area, east coast of India

Surface sediments collected at the Tirumalairajan river estuary and their surrounding coastal areas were analyzed for the bulk metal concentration. The sediments were collected from post- and premonsoon seasons. Dominances of heavy metals are in the following order: Fe > Mn > Zn > Pb > Cu in both seasons from estuary and coastal area. The results reveal that Fe, Mn, Cu, Pb, and Zn demonstrated an increased pattern from the estuary when compared to the coastal area. The heavy metal pattern of the sediments of the Tirumalairajan river estuary and its surrounding coastal area offered strong evidence that the coastal area was a major source of heavy metals to the estuarine region. For various metals, the contamination factor and geoaccumulation index (I _geo) have been calculated to assess the degree of pollution in sediments. The contamination factor and geoaccumulation index show that Zn, Pb, and Cu unpolluted to moderately pollute the sediments in estuarine part. This study shows the major sources of metal contamination in catchment and anthropogenic ones, such as agriculture runoff, discharge of industrial wastewater, and municipal sewage through the estuary and adjoining coastal area.     

Influence of anthropogenic activity on the lead isotope signature of Thau Lake sediments (southern France): origin and temporal evolution

Lead concentrations and isotopic compositions were determined on both bulk sediments deposited in the Thau lake in southern France during the last 200 years, and leachates derived from a series of sequential leachings of the sediments, making it possible to identify the sources, natural (i.e. indigenous lithologic) or anthropogenic, and to quantify the different inputs of Pb.Two distinct inputs of Pb could be distinguished. One of these corresponds to the terrigenous material entering the basin, representative of the local natural Pb ‘background’. Its supply remained steady most of the time with ²⁰⁶Pb/²⁰⁷Pb ratios of 1.200±0.003, except at the time of heavy storms producing voluminous and sudden depositions, such as that of September 1875. This Pb supply is mainly hosted by the detrital silicate fraction of the sediments. The second Pb input is a direct consequence of anthropogenic activities of various industrial and domestic emissions in the region, particularly due to the city of Sète and, to a lesser extent, to the villages in the watershed. The ²⁰⁶Pb/²⁰⁷Pb ratios of this input are of 1.142–1.162. The Pb added to gasoline could also be identified in the uppermost sediments, because of its specific ²⁰⁶Pb/²⁰⁷Pb ratios of 1.069–1.094. The leaching experiments also showed that the anthropogenic Pb is mainly hosted by the oxi-hydroxides of the sediments and to a lesser extent by the carbonates. It may also be adsorbed on particle surfaces, while only limited amounts are bound to organic matter.     

Lead in sediments and suspended particulate matter of the German Bight: natural versus anthropogenic origin

Sediments (568) and suspended particulate matter (SPM, 302 samples) of the southern German Bight and the adjacent tidal flat areas were analysed for selected major elements (Al, Fe, K), trace metals (Mn, Pb), and ²⁰⁶Pb/²⁰⁷Pb ratios using XRF, ICP–OES, ICP–MS. For selected samples a leaching procedure with 1 M HCl was used to estimate the Pb fraction associated with labile phases (e.g. Mn/Fe-oxihydroxide coatings) in contrast to the resistant mineral matrix. Enrichment factors versus average shale (EFS) reveal elevated Pb contents for all investigated sediments and SPM in the following order: Holocene tidal flat sediments (HTF, human-unaffected) <recent tidal flat sediments (RTF) <Helgoland Island mud hole sediments (MH) <nearshore SPM (SPM concentration>5 mg l⁻¹) < offhore SPM (<5 mg l⁻¹). Besides pollution, RTF contain elevated amounts of natural Pb-rich materials (K-feldspars and heavy minerals) due to a man-made high-energy environment (dike building) in comparison to HTF. ²⁰⁶Pb/²⁰⁷Pb ratios of RTF (1.192±0.019) are similar to the local geogenic background, determined from HTF (1.207±0.008). In contrast, Pb isotope ratios of nearshore SPM (1.172±0.007) and offshore SPM (1.166±0.012) show a distinct shift towards the anthropogenic/atmospheric signal of 1.11–1.14. This difference between RTF and SPM supports the assumption of low deposition rates of fine material in the intertidal systems. As the ²⁰⁶Pb/²⁰⁷Pb ratios of SPM do not reach the pure anthropogenic signal, the adsorbed Pb fraction was examined (leaching). However, the leachates also contained large amounts of geogenic Pb (SPM ≈40%, recent sediments ≈60%). The authors assume that the uptake of natural Pb occurs in nearshore waters, presumably in the turbid intertidal systems. Possible sources for dissolved Pb are mobilisation during weathering (geogenic signal) and dissolution of oxihydroxide coatings with subsequent release from porewaters, and unspecific riverine input. Comparatively small parts of SPM leave the coastal water mass and reach the open North Sea. This process therefore leads to a decontamination of the tidal flat sediments. Due to more pronounced atmospheric input, the offshore SPM becomes enriched in anthropogenic Pb as indicated by decreasing ²⁰⁶Pb/²⁰⁷Pb ratios with increasing distance from the coast.     

Comparative study of As,Cd, Cu,Cr, Mg,Mn, Ni,Pb and Zn concentrations between sediment and water from estuary and port

The contents of As, Cd, Cu, Cr, Mg, Mn, Ni, Pb and Zn have been determined in sediment and water samples from Valle de las Garzas estuary and Port Manzanillo (Colima, Mexico) using ICP-AES. The concentrations of these elements were used for a comparative study to determine the distribution of heavy metals and to evaluate which elements reflect natural or anthropogenic backgrounds. For this purpose, seven sampling points were selected: Four of them correspond to the lagoon, and three were situated in the port. Statistical analysis of the mineral content was assessed. Initially, data comparison was assessed by statistical tests for each variable. Principal component analysis was then applied considering the influence of all variables at the same time by obtaining the distribution of samples according to their scores in the principal component space. In this way, four studies were carried out: (1) study of sediments collected during the dry season; (2) study of sediments collected during the rainy season; (3) comparative study between sediments from rainy and dry season; and (4) study of water composition collected during rainy season. From the results of the performed analyses, it can be concluded that metals distribution pattern reflected natural and anthropogenic backgrounds (e.g., sediments from the lagoon, situated at the beginning of the rain channel, presented high contents of Zn and Cu, perhaps related to anthropogenic activities or the influence of igneous sediments).     

Heavy metal distribution in sediment profiles of the Pearl River estuary,South China

The Pearl River estuary is created by the inflow of freshwater from the largest river system that drains into the South China Sea. In recent years, massive economic growth and development in the region has led to excessive release of waste into the environment. The accumulation of contaminants in sediments is likely to pose serious environmental problems in surrounding areas. The study of sediment profiles can provide much information on the metal contamination history and long term potential environmental impacts. In this project, 21 core samples (up to 3.65 m deep) were collected in the Pearl River estuary. About 15 subsamples from each core were analysed for moisture content, total organic matter (L.O.I.), particle size and heavy metal and major element concentrations. The results show that Pb and Zn contents are elevated in the sediments at most of the sampling sites. Compared with historical monitoring results, the sediment metal contents have increased over the last 20 a, particularly for Pb. The west side of the Pearl River estuary tends to be more contaminated than the east side due to the contaminants inputs from the major tributaries and different sedimentation conditions. There are close associations between Fe, Co, Ni and Cu concentrations in the sediments. Zinc and Pb contents in the sediment profiles reflect a combination of the natural geochemical background, anthropogenic influences and the mixing effects within the estuary. The distribution of Pb in the sediments shows strong influences of atmospheric inputs, probably from the coal burning activities in the region.     

Depositional environment of mudflats and mangroves and bioavailability of selected metals within mudflats in a tropical estuary

Four sediment cores representing adjacent mudflat and mangrove sub-environments of middle estuary (Shastri) were analyzed for sand, silt, clay, and organic carbon. Total metal concentration of iron (Fe), manganese (Mn), nickel (Ni), zinc (Zn), chromium (Cr), copper (Cu), cobalt (Co), and lead (Pb) and chemical speciation of Fe, Mn, and Co on selected samples was also carried out on mudflat cores. The sediments in the upper middle estuary were found to be deposited under highly varying hydrodynamic energy conditions; whereas lower middle estuary experienced relatively stable hydrodynamic energy conditions with time. The tributary joining the river near the upper middle estuary is found to be responsible for the addition of enhanced organic carbon and metal concentrations. Speciation study indicated Fe and Co are from natural lithogenic origin while Mn is derived from anthropogenic sources. Higher Mn and Co than apparent effects threshold can pose a high risk of toxicity to organisms associated with these sediments.     

Isotopic evidence of lead sources in Loire River sediment

Sediments along the Loire River (central France) were investigated by means of Pb isotopes determined on the labile sediment fraction, or acid-extractable matter (AEM). The combination of trace elements and Pb isotopes allows deciphering the origin of the elements (i.e. natural or anthropogenic) and their history, in the sediment from two small watersheds (one draining basalt, the other one granite–gneiss), both in present-day suspended matter in Loire River water, and in sediment from the Loire estuary. Crustal weathering, as confirmed by the Pb-isotope ratios for most sample points, is the main source of Pb in the upstream part of the Loire River, as well as that transported in the middle part of the basin and in the estuary. Among anthropogenic sources, the use of Pb-isotopic compositions shows an influence of agriculturally-derived Pb inputs and a major input of Pb derived from gasoline, particularly in the estuary due to harbor activities.     

Distribution and assessment of sediment toxicity in Tamaki Estuary,Auckland, New Zealand

Heavy metal levels in surface sediments from Tamaki Estuary demonstrate significant up estuary increases in Cu, Pb, Zn, Cd and mud concentrations. Increased metal levels towards the head of the estuary are linked to local catchment sources reflecting the historical development, industrialisation and urbanisation of catchment areas surrounding the upper estuary. The relatively narrow constriction in the middle estuary (Panmure area), makes it susceptible to accumulation of upper estuary pollutants, since the constriction reduces circulation and extends the time required for fine waterborne sediments in the upper estuary to exchange with fresh coastal water. As a result fine fraction sediments trapped in the upper estuary facilitate capture and retention of pollutants at the head of the estuary. The increase in sandy mud poor sediments towards the mouth of the estuary is associated with generally low metal concentrations. The estuary’s geomorphic shape with a mid estuary constriction, sediment texture and mineralogy and catchment history are significant factors in understanding the overall spatial distribution of contaminants in the estuary. Bulk concentration values for Cu, Pb, Zn, and Cd in all the studied surface samples occur below ANZECC ISQG-H toxicity values. Cd and Cu concentrations are also below the ISQG-L toxicity levels for these elements. However, Pb and Zn concentrations do exceed the ISQG-L values in some of the surface bulk samples in the upper estuary proximal to long established sources of catchment pollution.     

Heavy metal history from cores in Wellington Harbour,New Zealand

Analysis of ten heavy metals (Ag, Cd, Cr, Cu, Fe, Mn, Ni, Pb, Sb, Zn) in six sediment cores from Wellington Harbour show both anthropogenic enrichments and diagenetic modifications. Absolute concentrations determined by two methods, x-ray fluorescence and acid leaching for bioavailability, are not comparable. However, vertical trends in concentrations of the cored sediment are comparable. To assess levels of anthropogenic pollution, enrichment factors (enriched concentrations in upper core divided by background levels in lower core) are preferred over index of accumulation (I _geo) values because preindustrial or background levels of heavy metals are well constrained. The ten metals are placed into three groups: (1) Cu, Pb, and Zn, which show the most anthropogenic enrichment; (2) As, Cd, Cr, Ni, and Sb, which are often associated with anthropogenic pollution but show only minor enrichment; and (3) Fe and Mn, which are diagenetically enriched. Assuming harbor waters are well mixed, anthropogenic enrichments of Cu, Pb, and Zn, are time correlative, but the degree of enrichment depends on the method of analysis and core location. Levels of As, Cd, Pb, and Zn show small variations in preindustrial sediments that are not related to changes in grain size and probably result from changes in the oxidation-reduction potential of the sediments and salinity of the pore waters.     

Regional variations in atmospheric deposition and sources of anthropogenic lead in lake sediments across the Canadian Arctic

Stable Pb isotope profiles in dated lake sediment cores were used to gauge the relative amounts and possible sources of anthropogenic Pb deposited from the atmosphere in different regions of the Canadian Arctic. A distinct north-south difference was found. In four High Arctic lakes (i.e., north of 66°N) in this study, recent Pb isotopic shifts or concentration increases attributable to anthropogenic Pb were negligible. The maximum possible contribution from anthropogenic Pb was 0 to 19% of acid-leachable Pb in the 1980s or 1990s. In contrast, two lakes in the Hudson Bay region displayed significantly lower Pb isotope ratios and threefold to fivefold increases of Pb concentrations in modern sediments, corresponding to anthropogenic Pb inputs of at least 72 to 91% of leachable Pb. Eurasian urban and industrial Pb is known to dominate the High Arctic atmosphere. A possible explanation for its negligible influence on northern lake sediments is that atmospheric Pb deposition at northern latitudes is reduced compared with southern regions and is small compared to local geological inputs. ²¹⁰Pb deposition declines with increasing latitude, apparently because of declining precipitation rates; stable Pb deposition may be similarly affected. Meteorological considerations and variations in the post-1900 Pb isotopic trajectories indicated that the predominant anthropogenic Pb source region in NW Hudson Bay was Eurasia, while in SE Hudson Bay, it was Canada and the United States, with a minor Eurasian component.     

Distribution and origin of lead in stream sediments from small agricultural catchments draining Miocene molassic deposits (SW France)

Total Pb concentrations and isotopic composition were determined in stream-bed sediments and bedrock from 29 small agricultural or forested catchments in the Gascogne area (SW France). The contribution of Pb from various natural and anthropogenic sources was investigated in this rural area which is very weakly impacted by industrial or urban emissions. Environmental parameters in catchments (importance of forest cover, organic matter and oxide content in sediments) were considered. A combination of geochemical (enrichment calculation, sequential extraction) and isotopic investigations was performed to constrain the origin of Pb and the distribution of anthropogenic Pb in sediments. Most of the sediments have low total Pb content compared to other agricultural regions more impacted by industrial or urban emissions. The results indicated a moderate but significant Pb enrichment, particularly for catchments draining forested areas. This enrichment was positively related to organic C content in sediment and catchment forest cover, whereas in entirely cultivated catchments it was related to Fe-oxide content.     

Source of sediments and metal fractionation in two Chinese estuarine marshes

The Changjiang and the Jiulong Estuaries, located in eastern and southeastern China, respectively, have different geomorphologic and tidal processes as well as anthropogenic development in their associated watersheds. Sediments in the Changjiang estuary mostly consist of SiO₂, CaO and MgO (mean percentages of 63.9, 4.34 and 2.35%), whereas sediments from the Jiulong estuary mostly consist of Al₂O₃, Fe₂O₃ and organic matter (mean percentages 19.2, 6.82 and 4.14%). The Jiulong estuarine sediments contain more than twice the concentrations of Pb, Zn, Cu, than those from the Changjiang estuary. In the Jiulong estuary, these heavy metals are associated with carbonates and organic matter, whereas in the Changjiang estuary, they are associated with residual fractions or clay. Sediments from the Changjiang estuary, mostly sediments with little organic matter, do not efficiently sequester anthropogenic-derived trace metals. In contrast, sediments from the Jiulong estuary consist of a mixture of fluvial and marine matter which can sequester heavy metals contributed by larger landscapes with industrial and municipal wastewater.     

Geochemical Control of Heavy Metal Concentrations and Distribution Within Bahia Blanca Estuary (Argentina)

Chromium and lead concentrations and distribution have been fully studied within Bahía Blanca estuary inner area, which is strongly influenced by urban and industrial stress. Not only metals dissolved in estuarine water but also those included in sediments and suspended particulate matters (SPM) were measured. In all cases, internationally standardized protocols were applied to metal measurements, including analytical quality check test through analysis of certified reference materials. Total metal contents from surface sediments and SPM were compared with those from a historical database of the area, as well as with values representing the natural geochemical baseline within the system. Results showed that heavy metal pollution is mainly localized in the areas close to both industrial effluents discharge system and urban sewage outfall discharge. Data from sequential extractions indicate that metals from anthropogenic sources (i.e., Pb) are potentially more mobile than those inherited from geological parent material (i.e., Cr). The influences of other potential sources of metals (i.e., streams, runoff) were also considered. SPM was clearly identified as the main carrier of the studied heavy metals within the system, and its significance to metals input into sediments and/or biota was verified. Finally, the normalization of measured metal concentrations against background reference elements (i.e., Al or Fe) has allowed to identify that most of the measured Cr was lithogenic, while a significant percentage of Pb was from anthropogenic origin within Bahía Blanca estuary.     

Geogenic and anthropogenic lead isotope signatures in the urban environment of Natal (NE-Brazil)

In this study the effect of anthropogenic emissions on the lead isotopic composition of sediments from the Potengi-Jundiai river system near the fast growing city of Natal, NE-Brazil, is investigated. The lead isotope signatures of sediments from the region of Natal were measured by ICP QMS and can be discussed in terms of three different end members of lead. Two geogenic lead endmembers can be distinguished and also be spatially separated, as higher lead isotope ratios occur in the vicinity of the town of Macaiba while the lead isotope ratios decrease towards the city of Natal and the mouth of the estuary. Proterozoic rocks of different age are potential lead sources as Paleoproterozoic rocks occur in the catchment of Jundiai river and younger, Neoproterozoic rocks predominate towards the mouth of the river. The lead isotope signatures of the anthropogenically affected samples deviate from the signatures of the unaffected samples indicating the existence of a third, anthropogenic source of lead. This source represents the lead isotope signature of anthropogenic emitters like waste- and coal-combustion which is also revealed by other geochemical studies conducted in Brazil.     

Composition and source identification of polycyclic aromatic hydrocarbons in mangrove sediments of Peninsular Malaysia: indication of anthropogenic input

This is a comprehensive study of the composition, origin and sources of specific polycyclic aromatic hydrocarbons (PAHs) in sediments of mangrove estuary in the western part of Peninsular Malaysia. Mangrove sediments were analyzed for 17 PAHs by gas chromatography–mass spectrometry. Total PAH concentrations in the sediments ranged from 20 to 112 ng/g on a dry-weight basis. High molecular weight PAHs were abundant in the sediments. Parent PAH ratios revealed that pyrogenic input has important contribution to the sedimentary PAHs. Ratios of alkylated PAHs indicate that the sedimentary PAHs were influenced by petrogenic PAHs, which implies that petrogenic input has contribution to the sedimentary PAHs but that it is not a major factor in distribution of PAHs within the estuary. Combustion-derived PAHs show a positive and very strong correlation with total PAHs (R ² = 0.926, p < 0.05). Total methylphenanthrenes show very weak correlation with total PAHs (R ² = 0.0928, p < 0.05). The PAH concentrations were found to increase with distance from the upstream of the estuary to the coastal area of the Straits of Malacca. For the assessment of sediment contamination using biological thresholds, none of the individual studied PAH compounds exceeded the values of the effect range low–effect range median guideline and the threshold effects level–probable effects level guideline. This study demonstrates that the sediments of the mangrove ecosystem facing the Straits of Malacca and Sumatra are influenced by anthropogenic PAH inputs as a result of human activities such as biomass burning, vehicle emissions and boating activities.     

Distribution and speciation of heavy metals in surface sediments from the Yangtze estuary and coastal areas

The concentrations and speciation of heavy metals (As, Cd, Cr, Cu, Hg, Ni, Pb and Zn) in the sediments of the nearshore area, river channel and coastal zones of the Yangtze estuary, China, were systematically investigated in this study. The concentrations of all heavy metals except Ni in the sediments of the nearshore area were higher than those of the river channel and coastal zones. In the nearshore area, the concentrations of most heavy metals except Hg in the sediments of the southern branch were higher than those of the northern branch because of the import of pollutants from the urban and industrial activities around. When compared with the threshold effect level (TEL) and geochemical background levels, Cr, Ni and As accumulated and posed potential adverse biological effects. The speciation analysis suggested that Cd, Pb and Zn in the sediments of the three zones showed higher bioavailability than the other heavy metals, and thus posed ecological risk. Significant correlations were observed among Cr, Cu, Ni and Zn (r > 0.77) in the nearshore area, Ni, Cu, Zn and Pb (r > 0.85) in the river channel and Ni, Cu, Cr, Pb and Zn (r > 0.75) in the coastal zone. Principal component analysis (PCA) indicated that the discharge of unban and industrial sewage, shipping pollution and the properties of the sediments (contents of Fe, Mn, Al, TOC, clay and silt) dominated the distribution of heavy metal in the nearshore area, river channel and coastal zones of the Yangtze estuary.     

Assessment of heavy metals in sediments near Hazira industrial zone at Tapti River estuary, Surat, India

Heavy metal accumulation due to industrial activities has become a very sensitive issue for the survival of the aquatic life. Therefore, distributions of several heavy metals have been studied in the surface sediments of Tapti–Hazira estuary, Surat, to assess the impact of anthropogenic and industrial activities near estuary. Totally 60 sediment samples were collected from four different sites at Tapti–Hazira estuary, Surat from January 2011 to May 2011 and examined for metal contents. The average heavy metal load in the study area are found to be 43.28–77.74 mg/kg for Pb, 48.26–72.40 mg/kg for Cr, 117.47–178.80 mg/kg for Zn, 71.13–107.82 mg/kg for Ni, 123.17–170.52 mg/kg for Cu, 0.74–1.25 mg/kg for Cd, 14.73–21.69 mg/kg for Co. Calculated enrichment factors (EF) reveal that enrichment of Pb and Cd is moderate at all sites, whereas other metals Cr, Ni, Zn, Co, and Cu show significant to very high enrichment. Geo-accumulation index (I _geo) results revealed that the study area is nil to moderately contaminated with respect to Cd, moderately to highly polluted with respect to Pb, Zn, and Cu and high to very highly polluted with respect to Co and Cr.