Multiscale Spatial and Small-Scale Temporal Variation in the Composition of Riverine Fish Communities

We studied the multiscale (sites, river reaches and rivers) and short-term temporal (monthly) variability in a freshwater fish assemblage. We found that small-scale spatial variation and short-term temporal variability significantly influenced fish community structure in the Macquarie and Namoi Rivers. However, larger scale spatial differences between rivers were the largest source of variation in the data. The interaction between temporal change and spatial variation in fish community structure, whilst statistically significant, was smaller than the variation between rivers. This suggests that although the fish communities within each river changed between sampling occasions, the underlying differences between rivers were maintained. In contrast, the strongest interaction between temporal and spatial effects occurred at the smallest spatial scale, at the level of individual sites. This means whilst the composition of the fish assemblage at a given site may fluctuate, the magnitude of these changes is unlikely to affect larger scale differences between reaches within rivers or between rivers. These results suggest that sampling at any time within a single season will be sufficient to show spatial differences that occur over large spatial scales, such as comparisons between rivers or between biogeographical regions.     

The role and distribution of total suspended solids in the macrotidal coastal waters of Korea

Spatial and temporal distribution patterns of total suspended solids (TSS) in the shallow and macrotidal regions of the Korean peninsula indicated there were significant changes in TSS concentrations. These were seasonally influenced by the wind, river input and tidal cycle. There were high TSS values at estuarine and river mouth stations and during low tide due to the re-suspension of bottom sediment by strong wind action during winter months, in addition the land input through rivers and strong tidal current during ebbing. Monthly mean values of TSS significantly correlated with wind speed and nitrate concentration (p < 0.01). This indicated that the resuspension of surface sediment was a more important source of TSS than the river input, and that nitrate was introduced into the water column during the resuspension process. TSS were seven times higher at low tide than in high tide. Light penetration was significantly inhibited by TSS; as >98% of incident light was absorbed within 2 m and zero photosynthetically active radiation (PAR) under 2 m in the estuarine stations during winter. Removal of heavy metals and nutrients by TSS in the water column was evident. Over 80% of the initial concentration of nutrients was removed within 10 min under various concentrations of TSS and also TSS contained significantly higher concentration of heavy metals than surface sediment. The concentration levels of nutrients and chemical oxygen demand in the west coast were comparable with the East and South Sea, even the major rivers in the Korean peninsula flow into the West Sea with major pollutant loadings into the coastal areas. High concentration of TSS is likely to contribute to the removal process of these pollutants, resulting in relatively lower levels of nutrients and organic materials in these coastal waters.     

Preliminary assessment of total dissolved trace metal concentrations in Sava River water

This study provides the preliminary data set for total dissolved trace metal concentrations in the surface water of the Sava River in Croatia and the assessment of Sava River water quality status. The highest levels of total dissolved metals were observed for Fe, Mn, and Zn (12.6 +/- 7.8 mirog L(-1), 3.44 +/- 3.95 mirog L(-1), and 2.27 +/- 1.53 mirog L(-1), respectively), the intermediate concentrations for Ni, Cu, and Cr (0.59 +/- 0.14 mirog L(-1), 0.54 +/- 0.14 mirog L(-1), and 0.32 +/- 0.06 mirog L(-1), respectively), and the lowest levels for Co, Pb, and Cd (0.064 +/- 0.022 mirog L(-1), 0.055 +/- 0.051 mirog L(-1), and 0.011 +/- 0.004 mirog L(-1), respectively). The results refer to the grab water samples taken at five sites in the period from March to June, 2006. For four trace metals (Mn, Pb, Zn, and Fe), the high temporal variability within one season was observed. It can present a problem for reliable evaluation of total dissolved concentrations of these metals in the river water, if the assessment is based on the occasional grab water sampling. The comparison of results obtained in this study with previously reported data for several unpolluted rivers indicated that Sava River water reflects a certain anthropogenic impact. However, according to the levels proposed by European regulations, it still can be classified as water containing total dissolved trace metals in concentrations not significantly above the natural level.     

Spatial and temporal variation of metal concentrations in adult honeybees (Apis mellifera L.)

Honeybees (Apis mellifera L.) have great potential for detecting and monitoring environmental pollution, given their wide-ranging foraging behaviour. Previous studies have demonstrated that concentrations of metals in adult honeybees were significantly higher at polluted than at control locations. These studies focused at a limited range of heavy metals and highly contrasting locations, and sampling was rarely repeated over a prolonged period. In our study, the potential of honeybees to detect and monitor metal pollution was further explored by measuring the concentration in adult honeybees of a wide range of trace metals, nine of which were not studied before, at three locations in the Netherlands over a 3-month period. The specific objective of the study was to assess the spatial and temporal variation in concentration in adult honeybees of Al, As, Cd, Co, Cr, Cu, Li, Mn, Mo, Ni, Pb, Sb, Se, Sn, Sr, Ti, V and Zn. In the period of July-September 2006, replicated samples were taken at 2-week intervals from commercial-type bee hives. The metal concentration in micrograms per gram honeybee was determined by inductive coupled plasma-atomic emission spectrometry. Significant differences in concentration between sampling dates per location were found for Al, Cd, Co, Cr, Cu, Mn Sr, Ti and V, and significant differences in average concentration between locations were found for Co, Sr and V. The results indicate that honeybees can serve to detect temporal and spatial patterns in environmental metal concentrations, even at relatively low levels of pollution.     

Effects of northeast monsoon on trace metal distribution in the South China Sea off Peninsular Malaysia

Concentrations of trace metals in the South China Sea (SCS) were determined off the coast of Terengganu during the months of May and November 2007. The concentrations of dissolved and particulate metals were in the range of 0.019–0.194 μg/L and 50–365 μg/g, respectively, for cadmium (Cd), 0.05–0.45 μg/L and 38–3,570 μg/g for chromium (Cr), 0.05–3.54 μg/L and 21–1,947 μg/g for manganese (Mn), and 0.03–0.49 μg/L and 2–56,982 μg/g for lead (Pb). The order of mean log K _D found was Cd?>?Cr?>?Pb?>?Mn. The study suggests that the primary sources of these metals are discharges from the rivers which drain into the SCS, in particular the Dungun River, which flows in close proximity to agricultural areas and petrochemical industries. During the northeast monsoon, levels of particulate metals in the bottom water samples near the shore were found to be much higher than during the dry season, the probable result of re-suspension of the metals from the bottom sediments.     

Natural attenuation of coal combustion waste in river sediments

The weathering of coal combustion products (CCPs) in a lotic environment was assessed following the Tennessee Valley Authority (Kingston, TN) fly ash release of 2008 into surrounding rivers. Sampled materials included stockpiled ash and sediment collected from 180 to 880 days following the release. Total recoverable concentrations of heavy metals and metalloids in sediment were measured, and percent ash was estimated visually or quantified by particle counts. Arsenic and selenium in sediment were positively correlated with percent ash. For samples collected 180 days after the release, total concentrations of trace elements downstream of the release were greater than reference levels but less than concentrations measured in stockpiled ash. Total concentrations of trace elements remained elevated in ash-laden sediment after almost 2.5 years. A sequential extraction procedure (SEP) was used to speciate selected fractions of arsenic, copper, lead, nickel, and selenium in decreasing order of bioavailability. Concentrations of trace elements in sequentially extracted fractions were one to two orders of magnitude lower than total recoverable trace elements. The bulk of sequentially extractable trace elements was associated with iron-manganese oxides, the least bioavailable fraction of those measured. By 780 days, trace element concentrations in the SEP fractions approached reference concentrations in the more bioavailable water soluble, ion exchangeable, and carbonate-bound fractions. For each trace element, the percentage composition of the bioavailable fractions relative to the total concentration was calculated. These SEP indices were summed and shown to significantly decrease over time. These results document the natural attenuation of leachable trace elements in CCPs in river sediment as a result of the loss of bioavailable trace elements over time.     

Characterization and source identification of airborne trace metals in Singapore

Airborne particulate trace metals have important health implications. As a consequence, their concentrations are increasingly monitored in many urban locations worldwide. In this study, fine atmospheric particles (PM(2.5)) were collected in Singapore over a period of 83 consecutive days during 2000, and analysed to determine the concentration of trace elements using ICP-MS. Altogether, eighteen airborne trace metals were quantified: Al, Ag, Ba, Cd, Cr, Co, Cu, Fe, Ga, Li, Mn, Ni, Pb, Sr, Zn, V, Si, and Ti. While Li was the least abundant trace metal with a mean concentration of 0.2 ng m(-3), Zn showed the maximum mean concentration of 279.1 ng m(-3). Calculation of enrichment factors indicated that the elements Pb, Zn, Cd, V, Ni, Cr, and Cu were enriched by factors of 30 to 5000 relative to their natural abundance in crustal soil. The extent of metal pollution in the study area was assessed by comparing the measured concentrations to those reported in the literature for a selected number of urban sites in other parts of the world. Factor analysis was used to identify the major sources affecting particulate air pollution in Singapore. The sources that contribute to the loading of trace metal-bearing aerosols in the Singapore urban atmosphere include fuel oil-fired power plants, metal processing industry, land reclamation and construction activities, municipal solid waste incinerators, and traffic emissions.     

Dynamic regression modeling of daily nitrate-nitrogen concentrations in a large agricultural watershed

Nitrate-nitrogen concentrations in rivers represent challenges for water supplies that use surface water sources. Nitrate concentrations are often modeled using time-series approaches, but previous efforts have typically relied on monthly time steps. In this study, we developed a dynamic regression model of daily nitrate concentrations in the Raccoon River, Iowa, that incorporated contemporaneous and lags of precipitation and discharge occurring at several locations around the basin. Results suggested that 95 % of the variation in daily nitrate concentrations measured at the outlet of a large agricultural watershed can be explained by time-series patterns of precipitation and discharge occurring in the basin. Discharge was found to be a more important regression variable than precipitation in our model but both regression parameters were strongly correlated with nitrate concentrations. The time-series model was consistent with known patterns of nitrate behavior in the watershed, successfully identifying contemporaneous dilution mechanisms from higher relief and urban areas of the basin while incorporating the delayed contribution of nitrate from tile-drained regions in a lagged response. The first difference of the model errors were modeled as an AR(16) process and suggest that daily nitrate concentration changes remain temporally correlated for more than 2 weeks although temporal correlation was stronger in the first few days before tapering off. Consequently, daily nitrate concentrations are non-stationary, i.e. of strong memory. Using time-series models to reliably forecast daily nitrate concentrations in a river based on patterns of precipitation and discharge occurring in its basin may be of great interest to water suppliers.     

Small-scale temporal variation and the effect of urbanisation on extracellular enzyme activity in streams

The activity of six extracellular enzymes involved in the degradation of dissolved organic carbon compounds was measured in two highly urbanised and two minimally impacted streams east of Melbourne, Australia, using 4-methylumbelliferyl-substrates. Small-scale temporal variation in enzyme activity was determined by repeatedly sampling the same point in the water column, while the effect of flow was determined by sampling in regions of higher and lower flow in both stream types. Replicate samples showed that enzyme activity was not significantly different over small (minutes) time scales. On five of six sampling occasions the enzyme activity was unaffected by flow. On one sampling occasion in a minimally disturbed stream, the difference between the high- and low-flow regions was statistically significant (ANOSIM, Global R= 0.78, P= 0.03). Enzyme activity profiles (activities of the suite of enzymes) of the streams in urbanised catchments were different to those in minimally disturbed catchments. The measurements made in four different streams showed high reproducibility over short time periods (minutes) which lends greater credibility to analogous spatial studies. Although these results determined that small-scale temporal variability was not significant, and that the effects of flow were generally minimal, it is recommended that spatial and temporal variability in the stream be at least considered before any studies measuring extracellular enzyme activity in stream waters are carried out. Such an approach will lead to conclusions from measurements that are not likely to be confounded by variables such as flow rate or time.     

Source identification and assessment of sediment contamination of trace metals in Kogarah Bay,NSW, Australia

The distribution of trace metals (spatial and temporal) and sedimentary fractions were investigated to identify the concentrations and sources of trace metals within Kogarah Bay, NSW, Australia. A total of 59 surface sediments and six subsurface samples from core of the sediment were collected. The contamination factor and pollution load index indices used to evaluate environmental effects of trace metals. The study area was found to be uncontaminated with Cr and Ni, moderately contaminated with As and considerably contaminated with Cu, Zn and Pb. The concentrations of Cr and Ni were below both effect range low and effect range median, while As, Cu, Zn and Pb were slightly above effect range low. The highest concentrations of these trace metals such as Cu, Zn and Pb were found in the north, northwest and southeast of the bay, close to discharge points, stormwater outlets and around boatyards and watercrafts. The spatial distributions of metals were strongly related to muddy particles and organic matter. The temporal sediments of metals declined with increased sediment depth, which reflects accumulation of trace metals since European settlement in this area. Furthermore, the source of the trace metals was found to be stormwater outlets, gasoline fumes, boatyards and other human activities.     

Staggered nested designs to assess scales of variability: the advantages of a spatially explicit analysis

A staggered nested sampling design was used to identify spatial scales of variation in the abundance of an intertidal clam Austrovenus stutchburyi. A georeferenced sampling design permitted assessment of abundance at spatial lags between 0.1 and 87 m. An analysis of variance approach produced imprecise estimates of variability, whereas spatially explicit analyses improved the resolution greatly. A geostatistical model identified the spatial scale of residual variance as 13 m and that of the asymptote of spatial dependence as 17 m. It also permitted mapping of bivalve abundance. Staggered nested designs are highly efficient for comparing hierarchies of scale, but in this study analysis of detailed positional information was required to tease out useful spatial information.     

Sampling over time: developing a cost effective and precise exposure assessment program

Studies requiring ambient exposure assessments invariably ask: How often should measurements be taken? Answer to such questions is dictated by budgetary considerations as well as spatial and temporal variability in the data. For example, do we obtain measurements during all seasons, all months within seasons, weeks within months and days within weeks? On one hand, we can obtain a one-time snapshot sample and regard it as representing the "true" mean exposure. On the other hand, we may obtain a large number of measurements over time and then average these in order to represent this "true" mean exposure. The former estimate is the least expensive but may also be the least precise while the latter, may be very precise but prohibitively costly. In this paper, we demonstrate how a pilot study can be undertaken with a potentially promising and feasible sampling plan for the full-scale study. By applying the statistical methodology of variance component analysis (VCA) to the pilot study data and exploiting mathematical relationship between the variance of the overall mean exposure and posited variance components, we can develop a sampling design with decreased sampling costs and/or increased precision of the mean exposure. Our approach was applied to determine sampling design choices for an on-going study that aimed at assessing ambient particulate matter exposure. We conclude that a pilot study followed by the VCA analysis may often lead to sampling design choices that offer considerable cost savings and, at the same time, promise to provide relatively precise estimates of the mean exposure for the subsequent full-scale study.     

Spatio-temporal variability of solid, total dissolved and labile metal: passive vs. discrete sampling evaluation in river metal monitoring

In order to obtain representative dissolved and solid samples from the aquatic environment, a spectrum of sampling methods are available, each one with different advantages and drawbacks. This article evaluates the use of discrete sampling and time-integrated sampling in illustrating medium-term spatial and temporal variation. Discrete concentration index (CI) calculated as the ratio between dissolved and solid metal concentrations in grab samples are compared with time-integrated concentration index (CI) calculated from suspended particulate matter (SPM) collected in sediment traps and labile metals measured by the diffusive gel in thin films (DGT) method, collected once a month during one year at the Seine River, upstream and downstream of the Greater Paris Region. Discrete CI at Bougival was found to be significantly higher than at Triel for Co, Cu, Mn, Ni and Zn, while discrete metal partitioning at Marnay was found to be similar to Bougival and Triel. However, when using time-integrated CI, not only was Bougival CI significantly higher than Triel CI, CI at Marnay was also found to be significantly higher than CI at Triel which was not observed for discrete CI values. Since values are time-averaged, dramatic fluctuations were smoothed out and significant medium-term trends were enhanced. As a result, time-integrated concentration index (CI) was able to better illustrate urbanization impact between sites when compared to discrete CI. The impact of significant seasonal phenomenon such as winter flood, low flow and redox cycles was also, to a certain extent, visible in time-integrated CI values at the upstream site. The use of time-integrated concentration index may be useful for medium- to long-term metal studies in the aquatic environment.     

The use of the oyster Saccostrea glomerata as a biomonitor of trace metal contamination: intra-sample, local scale and temporal variability and its implications for biomonitoring

Cu, Cd, Zn, Pb and Se concentrations were measured in the bivalve mollusc Saccostrea glomerata(Iredale and Roughly) from two uncontaminated locations, Clyde River Estuary, Batemans Bay and Moona Moona Creek, Jervis Bay, to determine natural variability of metals associated with mass, gender, age, tissue type and site within location. Trace metals were also measured in the Clyde River Estuary over an 11 year period and in five other NSW estuaries (Hastings River, Hunter River, Georges River, Tillgerry Creek and Lake Pambula) over a 13-month period to determine temporal variability and if diploid and triploid oysters accumulate trace metals differently. There were few significant relationships between trace metal concentrations and mass and no significant differences in trace metal concentrations between female and male oysters. Younger oysters (1.3 years) had significantly higher copper concentrations and higher trace metal variability than mature oysters (3 years). Different tissues have different trace metal concentrations with muscle tissues having lower concentrations. Considerable inherent variability occurs in oyster cohorts. Analysing specific tissues did not reduce variability of trace metal concentrations. Comparison of trace metal concentrations at two sites within the Clyde Estuary showed a significant difference in zinc concentrations. Cu, Cd, Zn and Se concentrations were generally higher and less variable in triploids than diploids. Pb had a variable pattern of accumulation with no consistent elevation in diploids or triploids. Inter annual variability of trace metal concentrations was considerable and trace metal concentrations also fluctuated throughout an annual cycle with no clear seasonal trends. Measurement of trace metals at known contaminated locations showed that Saccostrea glomerata accumulates metals in response to contamination. Saccostrea glomerata meet most of the requirements to be a biomonitor of trace metal contamination as they are abundant, sessile/sedentary, easy to identify, provide sufficient tissue for analysis, and accumulate trace metals in response to contamination. However, as trace metal concentrations can vary with mass, age, estuary position, ploidy type and temporally, care must be taken to collect individual organisms of similar mass, age and ploidy type to minimise variability, and from similar consistent positions and times to allow for seasonal changes in environmental conditions. Trace metal concentration variability is higher in young animals, thus to reduce variability, older mature animals could be selected. However, with immature oysters there are no complications because of the effects of spawning i.e. sudden loss of trace metals or body mass.     

Improving suspended sediment measurements by automatic samplers

Suspended solids either as total suspended solids (TSS) or suspended sediment concentration (SSC) is an integral particulate water quality parameter that is important in assessing particle-bound contaminants. At present, nearly all stormwater runoff quality monitoring is performed with automatic samplers in which the sampling intake is typically installed at the bottom of a storm sewer or channel. This method of sampling often results in a less accurate measurement of suspended sediment and associated pollutants due to the vertical variation in particle concentration caused by particle settling. In this study, the inaccuracies associated with sampling by conventional intakes for automatic samplers have been verified by testing with known suspended sediment concentrations and known particle sizes ranging from approximately 20 μm to 355 μm under various flow rates. Experimental results show that, for samples collected at a typical automatic sampler intake position, the ratio of sampled to feed suspended sediment concentration is up to 6600% without an intake strainer and up to 300% with a strainer. When the sampling intake is modified with multiple sampling tubes and fitted with a wing to provide lift (winged arm sampler intake), the accuracy of sampling improves substantially. With this modification, the differences between sampled and feed suspended sediment concentration were more consistent and the sampled to feed concentration ratio was accurate to within 10% for particle sizes up to 250 μm.     

Monitoring trace metal contamination in salt marshes of the Westerschelde estuary

A survey is given of the possibilities and restrictions of (bio)monitoring trace metals in the salt marsh as exemplified for the Scheldt estuary. The objectives for monitoring in the salt marsh are enumerated as well as the requirements they should meet. Previous studies on monitoring trace metals in the salt marsh are reviewed.Problems in monitoring trace metals in the soil subsystem are due to variations in the input of these metals, the type of esturine circulation and the distribution of physical and chemical conditions in the salt-marsh deposits. The degree of metal enrichment and the spectrum of chemical speciation of the metals by means of a sequential extraction procedure is shortly discussed.Problems in monitoring trace metals in salt-marsh plants are discussed with respect to the bioavailability of these metals from soil and inundation water as sources of contamination, the allocation and seasonal variation in metal accumulations, and the role of adhesive particulate matter carried on the shoots by the floods. Aster tripolium seems to be a good species for biomonitoring trace metals in the vegetational component of the salt-marsh ecosystem.Communication Nr. 346.     

Investigating Jacaranda mimosifolia tree as biomonitor of atmospheric trace metals

Studies on the use of tree bark as biomonitors for environmental pollutants are still very scarce. We evaluated the reliability of using Jacaranda mimosifolia, a common tree in Tshwane City of South Africa, as a suitable biomonitor of atmospheric trace metals. Bark samples were collected from ten different locations during two sampling periods. The concentrations of the metals were determined by inductively coupled plasma mass spectrometry. The concentrations of the metals were 33.2–1,795 μg/g (Pb), 21.4–210 μg/g (Cu), 68.4–490 μg/g (Zn), 30.6–2,916 μg/g (Cr), 0.12–1.34 μg/g (Cd), and 6.04–68.0 μg/g (V), respectively. The differences obtained for the results from different sites were significant (p?< 0.05). A significant difference was also observed between the two sampling periods. The trace metals concentrations suggested that automobile emissions are a major source of these metals. The study also confirms the suitability of J. mimosifolia as a biomonitor of atmospheric deposition of these metals.     

Chemical compositions and sources of atmospheric PM10 in heating, non-heating and sand periods at a coal-based city in northeastern China

Mass concentrations and chemical components (18 elements, 9 ions, organic carbon [OC] and elemental carbon [EC]) in atmospheric PM(10) were measured at five sites in Fushun during heating, non-heating and sand periods in 2006-2007. PM(10) mass concentrations varied from 62.0 to 226.3 μg m(-3), with 21% of the total samples' mass concentrations exceeding the Chinese national secondary standard value of 150 μg m(-3), mainly concentrated in heating and sand periods. Crustal elements, trace elements, water-soluble ions, OC and EC represented 20-47%, 2-9%, 13-34%, 15-34% and 13-25% of the particulate matter mass concentrations, respectively. OC and crustal elements exhibited the highest mass percentages, at 27-34% and 30-47% during heating and sand period. Local agricultural residuals burning may contribute to EC and ion concentrations, as shown by ion temporal variation and OC and EC correlation analysis. Heavy metals (Cr, Ni, Zn, Cu and Mn) from coal combustion and industrial processes should be paid attention to in heating and sand periods. The anion/cation ratios exhibited their highest values for the background site with the influence of stationary sources on its upper wind direction during the sand period. Secondary organic carbon were 1.6-21.7, 1.5-23.0, 0.4-17.0, 0.2-33.0 and 0.2-21.1 μg m(-3), accounting for 20-77%, 44-88%, 4-77%, 8-69% and 4-73% of OC for the five sampling sites ZQ, DZ, XH, WH and SK, respectively. From the temporal and spatial variation analysis of major species, coal combustion, agricultural residual burning and industrial emission including dust re-suspended from raw material storage piles were important sources for atmospheric PM(10) in Fushun at heating, non-heating and sand periods, respectively. It was confirmed by principal component analysis that coal combustion, vehicle emission, industrial activities, soil dust, cement and construction dust and biomass burning were the main sources for PM(10) in this coal-based city.     

Ecological interpretation of metal contents and contaminant source characterisation of sediments from a megatidal estuary

Sediments and the associated biota constitute an important compartment in the biogeochemical cycle of trace metals in soft substrate megatidal estuaries. The relationship between physicochemical, ecological properties, metal concentrations determined in megatidal estuary sediments from the French coast of the English Channel, the Baie des Veys and the macrobenthic organisms, are analysed, interpreted and reported. Total concentrations of zinc, cadmium, lead and copper were measured in mudflats and saltmarsh sediments using Differential Pulse Voltammetry. Sediment characteristics were obtained by measurement of particle size, water content, total organic carbon and carbonate content, using AFNOR standards. A semi-quantitative scale was used for assessing the density of the macrobenthic flora and fauna at each sampling site. Analysis of data obtained from this study showed a correlation between the concentrations of monitored trace metals and species of the macrobenthic fauna. The results of this study show that the physico-chemical characteristics of the sediments affect the retention of metals in the sediment and this in turn affects the biota.     

Distribution and partitioning of trace metals in sediments of the lower reaches of the New Calabar River,Port Harcourt,Nigeria

The distribution of trace metals in sediments of the lower reaches of the New Calabar River, Nigeria was evaluated togetherwith the partitioning of their chemical species between fivegeochemical phases. Samplings were made in five zones at the lower reaches of the New Calaber River. All the trace metals were determined by AAS after selective chemical extractions andconcentrations given in g gm^-1 (dry weight basis). The average totalconcentrations found for trace metals in the sediment were (mean ± rsd.) Pb: 41.6 ± 0.29, Zn: 31.60 ± 0.42, Cd: 12.80 ± 0.92, Co: 92 ± 0.25, Cu: 25.5 ± 0.65 and Ni: 3.2 ± 0.25. Maxima and minima concentrations are inconsistent with previous studies in other rivers of this region. Spatial distribution revealed that the sources of trace metals into theriver appeared to be of non-point. Five contamination indices were applied in studying the partitioning of the trace metals inthe sediment. These indices provided bases for ascertaining the potential environmental risk of trace metals in the river system.The results denote high partition levels in the more mobile andmore dangerous phases.