Metals In Surficial Sediments Research Articles

Contamination and ecological risk assessment of trace elements in sediments of the Anzali Wetland, Northern Iran.

In this paper, concentrations of some heavy metals in surficial sediments of the International Anzali Wetland were measured, this wetland is located in the northern part of Iran. Sediment pollution levels were examined and analyzed using reliable pollution indices including Pollution Load Index (PLI), Geoaccumulation Index (Igeo) and Enrichment Factor (CF), and finally it was revealed that heavy metal pollution ranged from low to moderate loads in the wetland. According to Sediment Quality Guidelines (SQGs) and Ecological Risk Index (ERI), it was concluded that As and Ni may have significant toxic impacts on aquatic organisms and also according to Effect Range Median (ERM), the toxicity probability of sediments in the Anzali wetland was estimated at 21%.

Chemo speciation of metals in surficial sediments of Nile delta coastal zone ecosystem, Egypt

River Nile, Egyp’s most important watercourse, flows into the Mediterranean Sea by two estuaries forming a large Delta, within which lie three lagoons of varying morphological and hydrodynamic characteristics. Most estuaries receive a large quantity of wastewater input from different sources and also domestic due to the densely populated highly industrialized, leading to severe pollution of the coastal areas. Surface sediment samples were collected from six sectors and were examined for grain size and concentrations of heavy metals As, Cd, Mo, and Sn using a sequential extraction method and ecological risk assessment method. The results indicated: (1) the total concentrations of these heavy metals were influenced by runoff, industrial wastewater, and sewage, and were all higher in the coastal area (2) sequential extractions suggested that As and Mo were mainly composed with residual, Cd was bound to exchangeable and Sn was dominated by iron and manganese oxides fractions; The Contamination Factor (CF) for As, Cd, and Sn showed a very high degree of contamination while Mo showed low contamination in all study areas. The pollution load index (PLI) values were above one (> 1) indicates an advanced decline of the sediment quality. The average of the Igeo values for the studied metals indicated heavily polluted. The largest bioavailability factors were measured in all studied areas for Cd and Sn, and for As in El-Tina area, reflecting a potential risk to aquatic life. The ICF results showed the highest ability of Cd and Sn to be released from the sediments to the overlying water.

Distribution, contamination status and bioavailability of trace metals in surface sediments along the southwest coast of India

This study investigates the influence of upwelling induced seasonal hypoxia in the sediment-water interface on the distribution, bioavailability and geochemical partitioning of selected trace metals in surficial sediments along the southwest coast of India based on two successive cruises. The first cruise was during the southwest monsoon (SWM) season when coastal waters exhibited intermittent bottom hypoxia due to upwelling. The second cruise during the northeast monsoon (NEM) season was characterised by a uniformly warm and well-oxygenated water column in the study region. The results showed that grain size, organic carbon and Fe are the major factors influencing the distribution of trace metals in the surface sediments. Based on the geochemical indices (contamination factor, enrichment factor and geo-accumulation factor), the study region appears to be moderately contaminated by Ni, Cr, and Pb. Based on the ecological risk assessment criteria, the enrichment of Pb, Cr and Ni may cause adverse effects on the benthic organisms. The fractionation studies demonstrated that the major pathway of metal deposition in the sediment is lithogenic. The data also showed that labile and organic fractions are the second dominant forms, while other fractions (exchangeable and carbonate) are insignificant. The consistency in the reactive Fe concentrations during SWM and NEM could be due to the absence of Fe dissolution in sediments under mild reducing condition (intermittent hypoxia). In addition to the above, an enrichment of organic matter also leads to increased deposition of trace metals in sediments. Conversely, the secondary phase enrichment factor and risk assessment code calculated based on the metal fractionation data indicated low risk and contamination along the southwest coast of India except for Zn that showed moderate contamination in some transects. The study provides the need for regular geochemical assessment to control metal pollution in the coastal environment, which is a major resource of the fishery.

Metal contamination in surficial sediments of Edremit Bay (Aegean Sea): Spatial distribution, source identification and ecological risk assessment

Seasonal and spatial distributions of metals in surficial sediments of Edremit Bay (Aegean Sea, Turkey) were investigated to determine contamination status, possible sources and ecological risks in the study area. Seasonal (autumn and spring) surface sediment samples were collected in 2015 with a box-corer from 14 stations. Metal concentrations (Hg, Cd, Pb, Cr, Cu, Mn, Zn, Fe, Al), grain size distributions and organic carbon levels were determined in samples. Metal levels were analyzed with flame (Pb, Cr, Cu, Mn, Zn, Fe, Al), cold-vapor (for Hg) and graphite furnace (for Cd) atomic absorption spectrometer after microwave digestion. Ranges of metal concentrations in Edremit Bay sediments were Hg: 0.03–017, Cd: 0.10–0.27, Pb: 5.32–47, Cr: 66–219, Cu: 13–57, Mn: 382–729, Zn: 66–154, Fe: 18685–50539 and Al: 10244–82819 mg/kg dry weight. Enrichment factor, geo-accumulation index, and contamination factor values were calculated, and the results indicated the presence of moderate Pb, Cr and Zn pollution in the sediments. According to sediment quality guidelines (threshold and probable effect levels), sediments were moderately to heavily polluted with Cr and Mn, and no potential harmful effects of Cd, Hg, Zn, Pb and Cu were found for aquatic organisms. Statistical analyses and risk assessments suggested that natural processes (i.e. streams, springs and rain run-offs) and anthropogenic inputs (i.e. mines, agricultural activities and domestic effluents) may have contributed to the metal levels in surficial sediments of Edremit Bay.

Concentrations, spatial distribution, and pollution assessment of heavy metals in surficial sediments from upstream of Yellow River, China.

Surface sediments were collected from 122 sites in the upstream of the Yellow River, China. The concentration of Fe, Mn, Cu, Ni, Zn, Cr, Pb, and Cd in sediments was investigated to explore the spatial distribution based on statistics and interpolation method. The results suggested that the concentrations of heavy metals were lower than potential effect levels (PEL). The samples above threshold effect level (TEL) for Pb and Zn were less than 10%, while almost 50% of samples for Ni exceeded PEL. Pb and Zn in sediments performed little or no adverse effects on the aquatic ecosystems. Higher concentrations of all heavy metals occurred in Qinghai and Gansu sections; the concentrations of Cu, Ni, and Zn were significantly higher than the Inner Mongolia section. Lower concentration of Fe, Mn, Cu, Ni, and Zn appeared in Qinghai section; the concentrations of Fe, Mn, Cr, and Pb manifested relatively steady and similar distributions and approximately decreasing tendency along the upstream of Yellow River.

Effects of a century of mining and industrial production on metal contamination of a model saline ecosystem, Great Salt Lake, Utah

Effects of mining and metals production have been reported in freshwater lake sediments from around the world but are rarely quantified in saline lake sediments, despite the importance of these lake ecosystems. Here we used dated sediment cores from Great Salt Lake, Utah, USA, a large saline lake adjacent to one of the world’s largest copper mines, to measure historical changes in the deposition of 22 metals. Metal concentrations were low prior to the onset of mining in the catchment in 1860 CE. Concentrations of copper, lead, zinc, cadmium, mercury, and other metals began increasing in the late 1800s, with peaks in the 1950s, concomitant with enhanced mining and smelting activities. Sedimentary metal concentrations in the 1950s were 20-40-fold above background levels for copper, lead, silver, and molybdenum. Concentrations of most metals in surficial sediments have decreased 2-5-fold, reflecting: 1) storage and mineralization of sedimenting materials in a deep brine layer, thereby reducing metal transport to the sediments; 2) improved pollution control technologies, and; 3) reduction in mining activity beginning in the 1970s and 1980s. Despite reductions, concentrations of many metals in surficial sediments remain above acceptable contamination thresholds for aquatic ecosystems with migratory birds, and consumption advisories for mercury have been placed on three waterfowl species. The research also highlights that metal deposition in saline lakes is complicated by effects of hypersaline brines and deep-water anoxia in regulating sediment redox and release of metals to surface waters. Given the importance of saline lakes to migratory birds, metals contamination from mining and metals production should be a focus of saline lake remediation.

Environmental radioactivity and trace metals in surficial sediments from estuarine systems in Ghana (Equatorial Africa), impacted by artisanal gold-mining

This paper reports concentrations of γ-emitter radionuclides (40K, 137Cs, 210Pb, 226Ra, 228Ra, 228Th and 234Th) and some metals (Al, Cr, Fe, Co, Ni, Cu, Zn, As, Sr, Cd, Sb, Cs, Pb, Th and U) in surficial sediments from the Ankobra, Pra and Volta estuaries, in Ghana. Artisanal gold-mining in the Ankobra and Pra basins promoted moderate enrichments of As, Sb, Cu, Cs and Cr in their estuarine sediments, with respect to the reference background of the Volta Estuary. Radionuclide concentrations were in the range found in the Earth's crust. Present data do not support any conclusion on their potential enrichments due to gold-mining activities. Radionuclide isotopic ratios revealed a transfer of 228Ra from sediments to the water column. Pearson correlation coefficient matrices showed different patterns, which were reasonably understood after novel approaches: i) inter-estuaries comparison of slopes in the linear regressions of element-concentrations vs Al, Fe and Cs; ii) study of Al-normalized concentrations of elements; iii) excess 210Pb informing on local sedimentary conditions. The metal enrichments observed in the Ankobra and Pra estuaries are associated with the Fe-rich compounds in sulphide ores (such as FeAsS) transported along the river course and deposited in the estuary.

Distribution, sources and ecological risks of metals in surficial sediments of the Forcados River and its Estuary, Niger Delta, Nigeria

The concentrations of eleven metals (Cd, Pb, Cr, Ni, Cu, Co, Ba, Mn, Zn, Fe and Al) were measured in surficial sediments of the Forcados River and its estuary situated in the Niger Delta, Nigeria. The aim of the study was to provide information on the influence of seasonal changes on the distribution patterns and sources of these metals and the ecological risks associated with exposure to metals in the river sediment system. Samples from nine locations were collected monthly for a period of 6 months covering both the wet and dry seasons. The sediment samples were digested with aqua regia, and the metal concentrations in the digests were quantified by means of inductively coupled plasma-atomic emission spectrometry (ICP-AES). The concentration ranges of metals in the sediments were: Cd 0.78–2.16, Pb 11.5–72.0, Cr 21.9–49.6, Ni 4.75–11.7, Cu 4.48–13.7, Co 5.03–11.7, Ba 2.04–3.34, Mn 153–545, Zn 11.7–35.1, Fe 9350–18,400 and Al 9560–25,000 mg kg−1. The results showed significant spatial and seasonal variations (p < 0.05) in the metal distribution patterns. The ecological risk indices indicate that low ecological risks are associated with exposure to these metals but with significant impact from Cd. The enrichment factors, and geoaccumulation and contamination/pollution indices, suggested that Cd is the main metal contaminant in the riverbed. Principal component analysis found that the sources of metals in the sediments include natural inputs, vehicular emissions and discharges from oil industries, waste dumps and riparian farmlands.

Heavy metals in surficial sediments of the central Bohai Sea: their distribution, speciation and sources

The semi-enclosed Bohai Sea has received large amount of pollutants from surrounding rivers and sewage channels along the densely populated and industrializing Bohai coasts, as well as the offshore oil exploration in the sea. The concentrations of heavy metals copper, cobalt, nickel, zinc, lead, chromium and cadmium in 25 surface sediment samples from the central Bohai Sea are obtained by ICP-MS analysis. The speciation of these heavy metals is extracted and their distribution, fractionation, pollution status and sources are presented. High concentrations of copper, cobalt, nickel, zinc and chromium are found in the sediments off the coastal area of the Bohai Bay and the central Bohai Sea mud, while high concentrations of cadmium and lead are found in the sediments in the whole study area. The residual fraction is the dominant form of copper, cobalt, nickel, zinc and chromium in the surface sediments, while cadmium and lead have large proportions in the nonresidual fractions. The ecological risk assessment shows that the sediments in the study area are unpolluted with respect to the heavy metals of cobalt, nickel and chromium and unpolluted to moderately polluted with respect to copper, zinc, cadmium and lead. Cobalt, nickel and chromium mainly have natural origin and their concentrations significantly vary with the composition of the sediments. The contents of copper, zinc, lead and especially cadmium in sediments are suggested to be influenced by pollutants of human activities. The heavy metals in the surface sediments at most sampling stations are mainly come from the Huanghe River; the heavy metals in the sediments in the northernmost part of the study area are significantly affected by the sediment from the Luanhe River; while in the Bohai Bay and the central region they were affected by the sediment from the Haihe River and aerosol deposition.

Sedimentology, geochemistry, pollution status and ecological risk assessment of some heavy metals in surficial sediments of an Egyptian lagoon connecting to the Mediterranean Sea

Spatial distribution of heavy metals (Co, Cu, Ni, Cr, Mn, Zn and Fe) was studied on Lake Edku's surface sediments in relation to sedimentology and geochemistry characteristics and their contamination status on the ecological system. Lake Edku's sediments were dominated by sandy silt and silty sand textures and were enriched with carbonate content (9.83–58.46%). Iron and manganese were the most abundant heavy metals with ranges of 1.69 to 8.06 mg g−1 and 0.88 to 3.27 mg g−1, respectively. Cobalt and nickel showed a harmonic distribution along the studied sediments. The results were interpreted by the statistical means. The heavy metal pollution status and their ecological risk in Lake Edku was evaluated using the sediment quality guidelines and the contamination assessment methods (geoaccumulation, pollution load and potential ecological risk indices, enrichment factor, contamination degree as well as effect range median (ERM) and probable effect level (PEL) quotients). Amongst the determined heavy metals, zinc had the most ecological risk. Overall, the heavy metals in surface sediments showed ecological effect range from moderate to considerable risk, specially, in the stations in front of the seawater and in drain sources that had the highest toxic priority.

Spatial variability of heavy metals in surficial sediments: Tajan River Watershed, Iran

In this paper, we assessed the spatial distribution of heavy metal concentrations (Al, As, Cd, Co, Cr, Cs, Fe, Ni, Sn and Zn) in the sediments of the Tajan River Watershed, an inflow to the Caspian Sea in the Northern Iran. Comparison of four interpolation techniques (ordinary kriging, simple kriging, inverse distance weighted and local polynomial interpolation) via cross validation suggested that kriging was the most accurate spatial analysis technique for the majority of the elements. Variogram models obtained by geostatistical procedures indicate existence of spatial correlation between samples, with the exceptions for Al, Cd and Zn. The mapped spatial distributions are showing a clear coincidence of variation pattern for different groups of the heavy metals. This indicates similar origin and affecting factors for these analyzed metals. Possible anthropogenic and natural sources of heavy metals were discussed based on the distribution maps and correlation analysis with other elements and geologic units. The results have shown that the accurate spatial pattern of heavy metals could improve our understanding of possible sources, controlling factors and involving processes. This is essential for monitoring and remediation of the contaminant sites in the watershed.

Metal Contamination and Their Distribution in Different Grain Size Fractions of Sediments in an Industrial Development Area

Assessment of metal contamination and their distribution in different grain size fractions of the surface sediments of a lake in Kazipalli industrial development area has been investigated. Since the persistent toxic metals pose serious health risks, this research concentrated on investigating the concentrations and spatial distribution of metals in and around the Kazipalli Lake. Ten sampling points were selected and approximately 500 g of surface sediments were obtained from 1ft depth. Samples were sieved and four grain size fractions (>250, 110-250, 61-110, <61 μm) from each sample were selected for the analysis of metals. The average concentration of ten points for individual metals (As, Co, Cr, Cu, Ni, Pb and Zn) revealed data ranging from 9.6 to 131.4 mg/kg for As, 3.0-20.8 mg/kg for Co, 15.3-196 mg/kg for Cr, 13-40 mg/kg for Cu, 18-74 mg/kg for Ni, 51-328 mg/kg for Pb and 27-335.1 mg/kg for Zn. Enrichment factor and correlation analysis were also applied to the data set. The overall results indicate that sediment grain size played important role in controlling the distribution of heavy metals in surficial sediments of Kazipalli Lake.

Biomonitoring of Cd, Cr, Hg and Pb in the Baluarte River basin associated to a mining area (NW Mexico)

With the purpose of knowing seasonal variations of Cd, Cr, Hg and Pb in a river basin with past and present mining activities, elemental concentrations were measured in six fish species and four crustacean species in Baluarte River, from some of the mining sites to the mouth of the river in the Pacific Ocean between May 2005 and March 2006. In fish, highest levels of Cd (0.06μgg−1 dry weight) and Cr (0.01μgg−1) were detected during the dry season in Gobiesox fluviatilis and Agonostomus monticola, respectively; the highest levels of Hg (0.56μgg−1) were detected during the dry season in Guavina guavina and Mugil curema. In relation to Pb, the highest level (1.65μgg−1) was detected in A. monticola during the dry season. In crustaceans, highest levels of Cd (0.05μgg−1) occurred in Macrobrachium occidentale during both seasons; highest concentration of Cr (0.09μgg−1) was also detected in M. occidentale during the dry season. With respect to Hg, highest level (0.20μgg−1) was detected during the rainy season in Macrobrachium americanum; for Pb, the highest concentration (2.4μgg−1) corresponded to Macrobrachium digueti collected in the dry season. Considering average concentrations of trace metals in surficial sediments from all sites, Cd (p<0.025), Cr (p<0.10) and Hg (p<0.15) were significantly higher during the rainy season. Biota sediment accumulation factors above unity were detected mostly in the case of Hg in fish during both seasons. On the basis of the metal levels in fish and crustacean and the provisional tolerable weekly intake of studied elements, people can eat up to 13.99, 0.79 and 2.34kg of fish in relation to Cd, Hg and Pb, respectively; regarding crustaceans, maximum amounts were 11.33, 2.49 and 2.68kg of prawns relative to levels of Cd, Hg and Pb, respectively.

Diagenesis and anthropogenesis of metals in the recent Holocene sedimentary record of the Ría de Vigo (NW Spain)

To contribute to establishing a historical baseline for future evaluations of the environmental quality of the Ría de Vigo (NW Spain), we report metal contents determined in eight gravity cores obtained at representative locations in 1990 – before the installation of any wastewater treatment plants – and in fractions thereof that were obtained by the BCR sequential extraction method. The results suggest that early diagenesis had been influenced by both hydrodynamic conditions and organic matter input (the latter especially in areas devoted to mariculture), and that anthropogenic inputs had also affected the concentrations and between-fraction distribution of Cu, Pb, Zn and other metals in surficial sediments.

Spatial distribution of heavy metals in surficial sediments from Guanabara Bay: Rio de Janeiro, Brazil

Ninety-two surface sediment samples were collected in Guanabara Bay, one of the most prominent urban bays in SE Brazil, to investigate the spatial distribution of anthropogenic pollutants. The concentrations of heavy metals, organic carbon and particle size were examined in all samples. Large spatial variations of heavy metals and particle size were observed. The highest concentrations of heavy metals were found in the muddy sediments from the north western region of the bay near the main outlets of the most polluted rivers, municipal waste drainage systems and one of the major oil refineries. Another anomalous concentration of metals was found adjacent to Rio de Janeiro Harbour. The heavy metal concentrations decrease to the northeast, due to intact rivers and the mangrove systems in this area, and to the south where the sand fraction and open-marine processes dominate. The geochemical normalization of metal data to Li or Al has also demonstrated that the anthropogenic input of heavy metals have altered the natural sediment heavy metal distribution.

TRACE METALS BINDING TO HUMIC AND FULVIC ACIDS FROM SURFACIAL SEDIMENTS OF LAKE MANZALAH, EGYPT.

Twelve sediment samples were collected from Lake Manzalah during summer, 2004 to examine the influence of dissolved humic and fulvic acids on the distribution of trace metals in surficial sediments of the Lake. Trace metal concentrations in the humic acid extracted from the Lake sediments showed considerably high contents of iron (1046-3069 ng/g); copper (234-1498 jig/g) and zinc (110-394 jig/g) . The other trace metals (Co, Cd, Cr, Ni and Mn) revealed low concentrations, ranging from 11.3 to 156 ixgJg. The metal concentrations in fulvic acid were in the following order; Fe (465-2767 ^Lg/g); Cu (49.6-250.6 jag/g); Zn (49.3-186.6 ng/g); Cd (39.6-80.8 pg/g); Ni (20.4-153.4 jxg/g); Co (12.5-78.0 jxg/g); Mn (11.8-55.9 ^ig/g) and Cr (9.1-39.6 ng/g). The values of Cu and Cd percentage associated with the humic acid were high comparing with that reported in the other metals. This relative percentage was decreased for the same metals in association with fiilvic acid. In general, the results indicated that the amounts of trace metals in humic acids decreased as follows: Fe > Cu >Zn > Ni > Co > Cd > Mn > Cr. While in fulvic acid the order was: Fe > Cu >Zn > Cd > Ni > Co > Mn > Cr.

Background levels of heavy metals in surficial sediments of the Gulf of Lions (NW Mediterranean): An approach based on 133Cs normalization and lead isotope measurements

This paper presents an attempt to reach natural background levels of heavy metals in surficial sediments of the Gulf of Lions (NW Mediterranean). To correct for the grain-size effect, normalization procedures based on a clay mineral indicator element are commonly used, after a first grain size separation by sieving. In our study, we tested the applicability of this method with respect to commonly used normalizer elements, and found that stable Cs shows the best ability to reflect the fine sediment fraction. Background levels were successfully reached for Co, Cr, Cu, Ni and Pb, compared to various literature references. Nevertheless, in the case of lead, the normalized data depicted a general enrichment in all samples, and the natural levels could only be reached when concentrations were corrected for the atmospheric contribution by analysing lead isotope ratios. Also for Zn, a general enrichment was found in our samples, although less important.

Evaluation of distribution, mobility and binding behaviour of heavy metals in surficial sediments of Louro River (Galicia, Spain) using chemometric analysis: a case study

Contents of total and extractable heavy metals, carbonates, MnO and Fe 2O 3, organic matter, and matrix components such as SiO 2, Al 2O 3, CaO, Na 2O, MgO, TiO 2, K 2O and P 2O 5 are used along with principal component analysis (PCA) for studying distribution, mobility and binding behaviour of Cd, Cr, Cu, Ni and Pb in the Louro River (Galicia, Spain). Eleven surficial sediment samples were taken along the beds of the river course. Total metal concentrations were obtained after microwave-assisted digestion whilst extractable metal contents were obtained following a three-stage sequential extraction scheme (i.e. soluble, reducible and oxidisable fractions). Loading plots of heavy metals bound to carbonates, Fe–Mn oxides, organic matter and aluminosilicates allowed determination of binding behaviour. Correlations found indicate that Pb and Cu are mainly discharged from urban wastes, whereas Cr and Ni are from electroplating and galvanizing industries. The occurrence of diffuse pollution sources along the river can account for the binding behaviour of Cd. Metal mobility decreased in the order: Cd>Pb>Cu>Ni>Cr. Despite total contents indicating moderate-to-high heavy metal pollution in this river, metals are mostly distributed in the residual fraction, hence showing a low risk of mobility.

Geographical and seasonal variation of trace metal bioavailabilities in the Gulf of Gdansk, Baltic Sea using mussels ( Mytilus trossulus ) and barnacles ( Balanus improvisus ) as biomonitors

The barnacle Balanus improvisus and the mussel Mytilus trossulus have been used as biomonitors of the trace metals Cu, Zn, Cd, Fe, Pb, Mn and Ni at five sublittoral sites in the Gulf of Gdansk (Baltic Sea) between February 2000 and September 2001. The study has established a benchmark against which future biomonitoring programmes will be able to establish changes in local metal pollution, particularly if metal loadings in the river Vistula (draining into the Gulf) alter in the future. The study highlighted differences in trace metal bioavailabilities to both barnacles and mussels, geographically and over time. Accumulated metal concentrations of Cu, Zn, Fe, Pb and Ni, but not Cd or Mn, were correlated in the barnacles and mussels, suggesting that the bioavailabilities of the former metals to the two biomonitors were similar. The barnacles showed greater discriminatory power than the mussels as trace metal biomonitors. Concentrations of trace metals in surficial sediments (<63 μm) did not correlate significantly with accumulated metal concentrations in either barnacles or mussels, indicating that sediment metal concentrations are not necessarily good proxy measures of ambient trace metal bioavailabilities to the local coastal filter feeders.

Heavy Metals in Sediments of the Upper Hawkesbury‐Nepean River

There is little published information on heavy metals in surficial sediments of the upper Hawkesbury‐Nepean River in central New South Wales, Australia. In the current investigation, the fine fraction (&lt;62.5 µm) of 90 sediment samples taken from this section of the river was analysed by flame‐Atomic Absorption Spectroscopy for nine heavy metals (Ag, Cd, Pb, Zn, Cu Co, Fe, Ni and Mn) to determine background and enrichment. Sediment in the upper Hawkesbury‐Nepean River is not heavily polluted by heavy metals. Maximum enrichment over background for Ni and Ag, Cd, Pb, Zn, Cu and Mn is 3x, 5.7x, 6x, 6.7x, 12x and 13.6x, respectively. Mean heavy metal concentrations for this, the upper section of the river, are about half the mean values for the Hawkesbury River between Windsor and Broken Bay in the lower, estuarine section of the river. The highest Cu, Pb and Zn concentrations (214, 108 and 334 mg kg−1, respectively) occur in surficial sediments in Peachtree Creek at Penrith and the Nepean River near Jacksons Lane, Castlereagh. These metal concentrations are possibly associated with industrial activity at Penrith. Two of the six sewage treatment plants on the upper Hawkesbury‐Nepean River are associated with high metal concentrations (Cu, Zn, Fe and Mn) in sediments, that is, the West Camden and Penrith sewage treatment plants. Other possible sources of heavy metals are coal mining and washing which occurs at several places in the upper catchment. The highest Cd, Co and Fe concentrations (1.7, 27.6 mg kg−1 and 4.81%, respectively) were found in sediments 400 m downstream of the Nepean Dam and the highest concentrations of Ni and Mn (54 and 790 mg kg−1, respectively) were located in sediment from the Nepean River at Moresby Hill Road Bridge, near Robertson and at the Avon Dam Road Bridge. The source of these metals is unknown.