The role of atmospheric deposition in an eastern U.S. deciduous forest

Atmospheric sources contributed significantly to the annual flux of trace metals and sulfate to the forest floor of Walker Branch Watershed, a forested catchment in the southeastern United States. Atmospheric deposition supplied from 14% (Mn) to≈40% (Zn, Cd, So ₄ ⁼ ) to 99% (Pb) of the annual flux to the forest floor; the remainder was attributable to internal element cycling. The measured water solubility of these metals in suspended and deposited particles indicates that they may be readily mobilized following deposition. Dry deposition constituted a major fraction of the total annual atmospheric input of Cd and Zn (≈20%), SO=(≈35%), Pb(≈55%), and Mn (≈90%); however, wet deposition rates for single events exceeded dry deposition rates by one to four orders of magnitude. Interception of rain by the canopy resulted in loss of Cd, Mn, Pb, Zn, and SO⁼ from the canopy, but uptake of H⁺ which increased with increasing free acidity of the incoming rain, and with increasing residence time of the rain on the leaf surface.     

Atmospheric Deposition of Trace Metals at Three Sites Near the Great Lakes

The concentrations of vanadium (V), chromium (Cr), manganese (Mn), nickel (Ni), copper (Cu), zinc (Zn), arsenic (As), selenium (Se), cadmium (Cd), and lead (Pb) in precipitation and on airborne particles were measured at three Integrated Atmospheric Deposition Network (IADN) monitoring stations on Lakes Superior, Michigan and Erie during 1993 and 1994. These data were used to estimate annual wet and dry deposition fluxes at these sites. In most cases, both wet and dry deposition make an important contribution to the total atmospheric flux of trace metals. Total (wet + dry) annual loadings of Zn and Cr are higher at the Lake Erie site than at the Lake Michigan and Lake Superior sites. Atmospheric loadings of the other metals are similar at all three sites. Wet deposition of metals is more closely related to precipitation amount than to the concentration of metals in the precipitation. Dry deposition fluxes are controlled by the concentration of trace metals on large particles. Total particle mass concentrations are higher during the summer and fall at the Lake Erie site, however no seasonal trends in total particle mass at the other sites or trace metals at any of the sites were detected. The total atmospheric loadings calculated in this work are in agreement with other estimates of metals deposition to the Great Lakes.     

Estimation method of residual alkylating agents in water treated with chloring-containing oxidant

Concentrations of trace metals in mosses Hylocomium splendens (Hs) and Pleurozium schreberi (Ps) are compared along with wet deposition at 8 sites in Sweden. Cd, Mn, Zn and Cr concentrations were similar in both mosses, while Cu, Fe, Pb, Ni and V levels were 14 to 24% higher in Hs than in Ps. The comparison to wet deposition estimates indicates that concentrations in mosses are also influenced by other factors than the adsorption of precipitation. No correlation was observed between the wet deposition of Mn, Cr and Ni and moss concentrations.     

Resuspension of Trace Metals in Belgrade Under Conditions of Drastically Reduced Emission Levels

Deposition rates of trace metals (Pb, Cu, Zn, Cd) were determined at the Meteorological Station in New Belgrade (H _s =74 m; φ=44°49′N and λ=20°24′E) in the hydrological year 1992/93 (1 November-31 October). The dominant characteristics of the observation period were strong drought and drastically reduced pollutant emissions. Traffic and local sources operated at 0–10% of their capacities. Samples of dry and wet precipitation were taken by an automatic collector at a height of 2 m at weekly intervals. Two petri polycarbonate dishes of 93.5 mm diameter, facing upward, and one, facing downward, were used for dry precipitation sampling. Determination in a ‘clean room’ by differential pulse stripping voltammetry provided the low detection thresholds of 0.1, 1.0, 0.5 and 2.0 ng mL^-1,i.e. the measurement of minimal dry deposition rates of 0.02, 0.2, 0.1 and 0.4 μg m^-2d^-1 for Cd, Pb, Cu and Zn, respectively. The mean annual deposition rates, expressed in μg m^-2d^-1, were found to be as follows: 4.5 (down), 26 (up) and 37 (wet) for Pb, 2.1 (down), 13 (up) and 36 (wet) for Cu, and 3.1 (down), 26 (up) and 95 (wet) for Zn. No values above 0.2 μg m^-2d^-1 were found for the Cd dry deposition rate and no Cd concentration higher than 1 ng mL^-1 for precipitation with an amount >0.5 mm at the weekly interval was detected. Using the XREDS method with a scanning electron microscope, Si, Al, Fe matrix elements and Mg, Ca, S, K, P, Cu, Zn. W were identified as minor constituents of the single spherical particles and of the agglomerates present. Pb could not be categorized as a minor constituent of the coarse particles suspended in the air of New Belgrade on the basis of the previous analysis. Analysis of meteorological data showed road dust transport by outgoing SE-ESE wind from the old city of Belgrade (H _s =100–250 m) as a possible Pb source at the chosen site, which was located in a park. A comparative measurement of Pb deposition on linden leaves was carried out in the vegetation period (1 April–31 October) of 1993 and 1994. The Pb distribution on leaves differed in the two growing seasons, while the sum of Pb deposition rates on the downward and upward oriented petri dishes remained practically equal. The Pb accumulation on linden leaves was higher in 1994, first because of an intensive soil supply by rain water. Besides, ‘yellow’ rain was reported during the night 15/16 April, on 16 and 17 April 1994. A Fe concentration of 2.3 μg mL^-1 and a Pb concentration of 312 ng mL^-1 with a total precipitation of 12.6 mm were found in the weekly wet sample of 13–20 April. Dry deposition rates of 17 and 84 μg m^-2d^-1 for Cd and Pb, respectively, were measured on the upward facing dishes two weeks later (27 April–4 May). The synoptic analysis confirmed the development of the Saharan cyclogenesis and its influence on the Balkan peninsula in the period of 14 to 17 April 1994. In this region the impact of dustfall originating from the Saharan storm was evident either during wet deposition or through resuspension processes.     

Wet Deposition of Trace Metals in Singapore

The concentrations of 12 trace metals (Al, Cd, Cr, Cu, Co, Fe,Mn, Ni, Pb, Zn, V, and Ti) in wet depositions are reported. Eighty four rainwater samples were collected using an automated wet-only sampler in Singapore for one year (2000) and subjected to chemical analysis using ICP-MS. Based on the volume-weighted meanconcentrations measured, the trace metals were classified into three groups: Al and Fe with an average concentration of largerthan 15 μg L^-1, Cr, Cu, Mn, Ni, Pb, Zn, V, and Ti withconcentrations between 1 and 10 μg L^-1, and finally Co and Cd with concentrations lower than 1 μg L^-1. Elementenrichment factors were calculated to distinguish between naturaland anthropogenic sources. The calculation of crustal enrichmentfactors with Al as the reference element indicated that while Ti,Fe and Mn originated from crustal sources, the remaining trace metals (Cd, Cr, Co, Cu, Ni, Pb, Zn and V) were mainly derived from anthropogenic sources. The removal of the trace metals from the atmosphere by precipitation was influenced by the rainfall amount as well as pH. The magnitude of the measured average annual wet deposition fluxes of Al, Fe, and combustion-generatedelements such as V, Ni, and Cu is higher than that reportedfor other sites outside Singapore, owing to abundant rainfallthroughout the year in this region.     

Atmospheric deposition of heavy metals in central Ontario

As part of a study to determine the magnitude of atmospheric inputs of materials into the lakes of central Ontario, a four-station network of bulk deposition and wet-only precipitation samplers was established in the Muskoka-Haliburton and Sudbury regions to determine the deposition (mg m^2? yr^?1) and volume weighted concentration (μg 1^?1) of Ph, Cu, Ni, Zn, Al, Mn and Fe in precipitation. Large temporal variations in the monthly deposition of all metals were observed. The variations for Cu and Ni exhibited seasonal patterns which could be attributed to a combination of source and wind direction factors. Concentration and deposition of all metals at Muskoka-Haliburton were generally as low or lower than median North American values from the literature. At Sudbury, the large local smelting industry contributed to the elevated Cu, Ni, Zn, and Fe deposition measured in the region (up to two orders of magnitude larger than Muskoka-Haliburton); Al and Mn values were not elevated. Deposition of Cu. Ni and Fe was inversely related to distance from the largest point source at Sudbury. The importance of dry deposition is greatest at Sudbury where dry inputs of Cu, Zn, Al, and Fe generally exceed wet inputs. In contrast, wet deposition of metals at Muskoka-Haliburton predominates over dry. Calculation of an enrichment factor (normalized against Mn) showed that the levels of Pb, Cu, Ni and Zn observed in the precipitation of central Ontario require an additional non-crustal source (either natural or anthropogenic) for explanation.     

Behavior of Metals Under Different Seasonal Conditions: Effects on the Quality of a Mexico–USA Border River

Spatial and seasonal mobilization trends of metals in surface water were evaluated in the US–Mexico San Pedro River (SPR). Water samples were collected at five sampling stations for the analysis of dissolved oxygen, pH, electric conductivity, sulfates, and metals (Cd, Cu, Fe, Mn, Pb, and Zn). Quality of the water was characterized through Ecological Criteria of Water Quality (ECWQ) established in Mexico and Water Quality Criteria (Environmental Protection Agency (EPA)). High total metal concentrations were detected as follows: Fe?>?Cu?>?Mn?>?Zn?>?Pb?>?Cd. Metal concentrations were slightly higher in dry season than in rainy season: Cd (below detection limit (BDL)–0.21 mg L^?1), Cu (BDL–13 mg L^?1), Fe (0.16–345 mg L^?1), Mn (0.12–52 mg L^?1), Pb (BDL–0.48 mg L^?1), and Zn (0.03–17.8 mg L^?1). Low pH and dissolved oxygen values as well as high sulfate content were detected in both seasons. High values of metals (Cd, Cu, Fe, Mn, Pb, Zn) were detected at station E1 representing pollution source, as well as at stations E2 (Cd, Cu, Fe, Mn), E3 (Fe, Mn, Pb), and E4 and E5 (Fe, Mn). Detected concentrations exceeded maximum permissible established in ECWQ and Water Quality Criteria (EPA). Efflorescence salts on sediments in the dry season could increase levels of metals in water column. This study provides valuable information on the potential mobility of metals in surface water of SPR located in an arid environment where transport processes are strongly linked to climate. The information derived from this study should help the regional and national authorities to address present environmental regulations.     

Factors influencing atmospheric deposition,stream export,and landscape accumulation of trace metals in forested watersheds

Wet and dry deposition inputs and streamflow output of Cd, Mn, Pb, Zn, and Al were measured intermittently at four deciduous forested watersheds in the southeastern United States between 1976 and 1982. Atmospheric inputs to each site were similar, varying by factors of 1.1 to 2.2 for the different metals. Metal levels in precipitation indicate that these sites are representative of rural, continental areas. Metals in rain exhibit significant temporal and spatial trends, with concentrations generally higher during summer than winter at all sites and generally lowest at the more remote site. The concentrations of Cd and Pb in both wet and dry deposition decreased between the period 1976 to 1977 and 1981 to 1982. Ion ratios and enrichment factors suggest that Mn is largely soil derived in atmospheric samples while Cd, Pb, and Zn are enriched over typical soil levels. Factor analysis indicates that soil components influence both Al and Mn while fine aerosol components influence Cd in wet and dry deposition. Both components influence the behavior of Pb. Dry deposition dominated the input of Mn and Al to each site, while wet deposition was the major input process for the other metals (54 to 85% of total). On an annual basis, deposited Cd, Pb, and Zn are strongly retained in each watershed: 2% of the Pb, 8 to 29% of the Cd, and 8 to 34% of the Zn inputs were transported in stream flow. Deposited Mn and Al are retained to a lesser degree and show a net loss from two sites. Metal export is controlled by stream pH, organic carbon, bedrock geology, and hydrologic characteristics of each site.     

Trace element loading of southern Lake Michigan by dry deposition of atmospheric aerosol

Aerosol samples and meteorological data were collected at a mid-southern Lake Michigan site (87° 00′ W, 42° 00′ N) from May through September 1977. Hi-volume samplers with cellulose fiber filters and a digital meteorological data recording system were operated on board the U.S. EPA's R/VRoger R. Simons during four intensive sampling periods. Aerosol samples were analyzed by atomic absorption spectroscopy for seventeen trace elements. A diabatic drag coefficient method was used to determine aerosol deposition velocity (v _d ) overlake. A meanv _d of 0.5 cm s^?1 was found for the 0.1v _d to a long-term climatological record, annual dry deposition loadings to the southern basin for nine elements were estimated. For four elements, Fe, Mn, Pb, and Zn, dry deposition loadings to the southern basin alone of at least 500, 30, 250, and 100 (×10³ kg yr^?1) were found. For Fe and Mn, these loadings represent about 15% of the total of all inputs to Lake Michigan. for Zn and Pb, about one-third to one-half of the annual loading from all sources is from dry deposition of atmospheric aerosol.     

Dissolved and particulate trace metals in a wetland of international importance: Lake Mikri Prespa,Greece

This paper reports the dissolved and particulate trace metal distributions in Lake Mikri Prespa, wetland of NW Greece. The concentrations of Cu, Pb, Zn, Cd, Al, Fe, Mn, Ni and Cr were determined in surface and hypolimnetic waters as well as in the inputs and the outflow. Trace metals were connected with two major populations of suspended particles, identified by using the recovery ratio for two different leaching reagents, namely 0.5 N HCl and 1:1 hot aqueous HNO₃. The first group is land derived entering the lake through runoff and plays a rather restricted role in its geochemistry. The second group which is more important includes authigenic carbonates, Fe and Mn hydroxides and oxides and organic rich particulates.     

Sediment trace metal contamination in the Ivory Coast,West Africa

To help expand our global perspective on trace metal contamination, concentrations of Cu, Fe, Hg, Mn, Ni, Pb, and Zn were determined for sediments from the Ebrie Lagoon in the Ivory Coast, a developing West African nation. Excess loading of several metals, especially Hg, Pb, and Zn was found at several sites. The maximum concentration of Hg measured in sediments from the Ebrie Lagoon (2250 ng g^?1) is about 30 times greater than natural levels. Similarly, Pb and Zn concentrations for the Ivorian lagoonal sediments are as high as 250 and 560 μg g^?1, respectively, showing sizeable anthropogenic inputs. Trace metal sources to the Ebrie Lagoon include untreated sewage and industrial wastes.     

Regional patterns of contaminants (PAH,pesticides and trace metals) in snow of Northeast Bavaria and their relationship to human influence and orographic effects

In January 1978, 31 snow samples were collected throughout NE-Bavaria and were analyzed for trace metals (Zn, Pb, Cd, Cu), pesticides (α-BHC, Lindane, Aldrin, Dieldrin) and polycyclic aromatic hydrocarbons (PAH) (3,4-benzopyrene, 1,12-benzoperylene, fluoranthene and 3,4-(o-phenylene)-pyrene). The regional pattern of PAH-concentrations can be explained as follows: above urban areas and through orographic uplifting of the air, PAH's are scavenged from the atmosphere by snow. The trace metals and specific conductance show similar regional patterns, although the pattern for Pb is influenced by automobile traffic as well as by glass and ceramic industries. The pesticides show less distinct patterns relative to the other two groups of contaminants. Using multivariate statistics it was shown that the trace metals with the exception of Pb and the PAH's had regional patterns similar to each other but distinct from the pesticides. Although orography, urbanization and industries are shown to affect the regional patterns of PAH's and the trace metals, this is not the case for pesticides. They originate from diffuse sources in agricultural and f forested lands.     

A baseline study on trace metal elution from diverse soil types

Ten soils were leached with a dilute solution of AICI₃, and FeCl₂ adjusted with HCl to pH 3.0. The effluents were analyzed for eight trace metals as well as pH, to determine the maximum contribution of the soils to the trace metal burden of the soil solution. This contribution was correlated with various soil properties to evaluate the controlling factors on the elution of certain metals. Measurable quantities of Mn, Co, Zn, Ni, Cu, and Cr were found in the soil leachates; Cd and Pb were infrequently detected. The important soil properties describing the amounts of the elements leached were the total metal originally present, the total amount of Mn, and the percentage of free iron oxides.     

Enrichment of trace elements from long-range aerosol transport in sandy podzolic soils of southwest France

Total content of trace elements (Cd, Co, Cr, Cu, Mn, Ni, Pb, and Zn), was determined to a depth of about 1 m in the horizons of three representative podzolic soils (i.e., wet moor, dry moor, and dune soil) developed on the coarse sands of the Atlantic face of southwest France. In the aged soils (wet moor and dry moor), Cr, Cu, Ni, Pb and Zn, were highly concentrated in the B horizons whereas Cd accumulated in the litter. An estimate of metal balance was made in the soil profiles, comparing the total amount of metal recovered in the A-B horizons to the amount of indigenous metal determined in a rock matter (C) layer of a similar depth as the A-B horizons. Substantial long-term enrichment of the whole upper part of the profile (A-B horizons) of three representative sites was found for Cd (0.1–0.6 kg ha^?1), Cu (3–12 kg ha^?1), Ni (1–7 kg ha^?1), Pb (20–26 kg ha^?1), and, to a lesser extent, for Co, Mn, and Zn. Since the experimental site was remote from industrial, urban and agricultural activities, the increase in soil metal content was apparently caused by the deposition of metallic aerosols via long-range transport. Total long-term inputs are estimated for average values of Cd (0.6 kg ha^?1), Cr (5 kg ha^?1), Cu (12 kg ha^?1), Ni (7 kg ha^?1), Pb (25 kg ha^?1) and Zn (6 kg ha^?1) for the 1 m depth. Several Atlantic areas of Europe are probably affected by a similar metal input.     

Atmospheric bulk deposition of trace metals to the Seine river Basin, France: concentrations, sources and evolution from 1988 to 2001 in Paris

Concentrations of Cd, Cu, Ni, Pb and Zn were determined in bulk atmospheric deposition collected at five stations in the Seine River basin (France), to evaluate sources and fluxes of atmospheric trace metals. Bulk deposition (wet + dry) was sampled weekly from March 2001 to February 2002 for 4 sites and from March to December 2001 for the last one. The concentrations of the elements in bulk deposition (dissolved + particulate form) followed the order: Zn > Pb > Cu > Ni > Cd. Concentrations of Zn, Pb and Ni were highly correlated with one another, suggesting a common source, related to the combustion of coal and heavy fuel. Metal concentrations in bulk deposition did not exhibit a high degree of temporal variability over the annual cycle and were not obviously related to meteorological parameters (rainfall, wind). Estimates of the total annual direct atmospheric deposition of metals to the Seine Estuary ranged from 16 kg yr^{? 1} for Cd to 5600 kg yr^{? 1} for Zn. Loadings of Cd, Cu and Ni from direct atmospheric inputs were less than 1% of those contributed by the Seine River and loadings of Pb and Zn represented 1.27% and 1.56% of the Seine contribution. Direct atmospheric inputs are negligible compared to fluvial inputs, but the indirect atmospheric deposition to the estuary was not estimated. Based on these results, trace metal concentrations in Paris have decreased by a factor of 4.6 for Zn and by a factor of 50 for Ni from 1988 to 2001. Of particular interest is the continued decrease in bulk deposition of Pb during this period, underlining the impact of policy initiatives concerning the reduction of lead on emissions in France.     

Determination of Mn and Pb in atmospheric deposition at a remote coastal site

The electrothermal atomic absorption spectrophotometric determination of Mn and Pb in wet, dry and total deposition collected at American Samoa is hindered by interferences due to the dilute sea-spray matrix. Matrix modification procedures permit direct analysis below 1 ng ml^?1 for each trace metal. The median monthly deposition of Mn is 5.8, 5.0, and 10.0 ng cm^?2, and for Pb 9.5, 1.4, and 10.6 ng cm^?2 for wet, dry and total collections, respectively. Preliminary data suggest effective sampling using these methods at this remote site.     

Distribution of Trace Metals in Channel Sediment: a Case Study in South Atlantic Coast of Spain

Recently, Sancti Petri channel on the southwestern (SW) part of Iberian Peninsula has been experiencing urban, industrial, and vehicular expansion. Until recently, there have been only few published reports documenting the pattern of metal accumulation in this estuarine sediment. In the present study, trace metals such as Cu, Zn, Ni, Mn, Pb, Co, Cd, As, and Hg concentrations were analyzed from 69 sediment samples collected from 23 sampling sites of the Santi Petri channel. The magnitude of trace metal accumulation found as the following trend: Mn > Zn > Cu > Pb > Ni > Co > As > Cd > Hg. Spatial distribution pattern demonstrated overall decreasing trend of trace metal from Cadiz Bay mouth to the open ocean mouth, clearly correlative to the presence of anthropogenic inputs. Results of the principle component analysis (PCA) revealed that sediment metal chemistry of Sancti Petri channel is mainly regulated by the concentrations of Pb, Cu, Zn, and Ni; possible sources of those were from vehicular-related emissions. Pollution load index (PLI) and geo-accumulation index (I _geo ) indicated overall low values. The study will stimulate improvement of our understanding regarding the pattern of accumulation of metals in the coastal sediments, and the recorded values of metals in the present study can be used as suitable reference for future studies.     

Aerial inputs of cadmium,copper, lead,and manganese into a freshwater pond in the vicinity of a coal-fired power plant

Cadmium, Cu, Mn, and Pb were analyzed in bulk precipitation for 21 mo at a 2 ha pond, located 5.5 km northwest of an 83 MW coal-fired power plant in South Carolina. No significant changes in mean concentrations of the four metals in bulk precipitation were observed after installation of modern electrostatic precipitators on the stacks of the power plant, which had previously been equipped with mechanical cyclone collectors for removal of fly ash. Hence, fly ash from stack emissions was apparently not a major source of aerially deposited trace metals at the pond site. Annual inputs of the four metals in bulk precipitation at the pond were similar to values reported for other rural areas in North America. Enrichment factors, with Mn as a reference element, indicated that Cd, Cu, and Pb in bulk precipitation were not derived from soil or crustal material. Cadmium, Cu, and Pb were enriched in all samples of bulk precipitation relative to their abundances in local soils, and were most enriched during autumn and winter. A multiple regression procedure suggested that wetfall was the primary mode of aerial deposition of Cd and Cu, whereas both wetfall and dryfall were important modes of aerial deposition of Pb.     

Urbanization effects on sediment and trace metals distribution in an urban winter pond (Netanya,Israel)

Purpose

This paper aims to elucidate urban development-induced processes affecting the sediment and the distribution of contaminating metals in a seasonal pond located in the highly populated Israeli Coastal Plain. The paper demonstrates how an integrated approach, including geochemical, sedimentological, geochronological, mathematical, historical, and geographical analyses, may decipher a complicated and dynamic metal pollution history in a sedimentary environment controlled by anthropogenic activity.

Materials and methods

Three short sediment cores were collected from the margins and center of a small urban pond (Dora, Netanya), located within the Israeli Coastal Plain. Profiles of grain size, organic matter (OM), trace metals (Pb, Zn, V, Ni, Cu, Cr and Co), Pb isotopic ratios, and ²¹⁰Pb activities (center and southern cores) were determined and a geochemical mixing model was employed (southern core). The watershed contour was calculated, and aerial photos and satellite images were examined.

Results and discussion

Construction activities in the watershed were chronologically associated with coarse sediment transport and deposition in the margins of the pond. The upper sandy layers were superimposed on layers rich in fine particles and OM, high concentrations of trace metals, and with Pb isotopic composition of more recent petrol. In the ²¹⁰Pb-dated southern core, deep metal-rich layers with petrol-related Pb isotopic ratios were inconsistent with metal emissions history. These findings point to mobility and migration of recent contamination metals through the coarse upper sediment layers and into deeper denser layers, confirmed also by a geochemical mixing model. Conversely, in the center of the pond, homogeneous fine particles were deposited with metal profiles consistent with regional emissions.

Conclusions

A small urban pond was found to provide an important case study for understanding heavy metal pollution records in highly populated regions. The margins of the pond depicted the surrounding urban development and the induced coarse sediment erosion, accompanied with post-depositional metal mobility. Due to the proximate developing residential areas, high metal concentrations accumulated in the margins, overshadowing regional atmospheric pollution levels recorded by sediment at the center of the pond.

     

Assessment of Heavy Metal Pollution in the Sediments of the River Pra and Its Tributaries

An investigative study was conducted to determine the heavy metal pollution in the sediment in the Pra Basin of Ghana from 27 sampling points during the dry and wet seasons using the geo-accumulation index (Igeo), enrichment factor (EF), and pollution load index (PLI). Sediments were acid digested and analyzed for the following selected metals: arsenic (As), lead (Pb), cadmium (Cd), zinc (Zn), manganese (Mn), total chromium (Cr), nickel (Ni), and iron (Fe) using the dual atomizer and hydride generator atomic absorption spectrophotometer (model ASC-7000 No A309654, Shimadzu, Japan). The metal concentrations (mg kg^?1) in the sediments were as follows: As (0.175)?<?Cd (3.206)?<?Ni (79.927)?<?Zn (118.323)?<?Cr (216.708)?<?Mn (234.742)?<?Pb (335.381)?<?Fe (1354.513) in the dry season and As (0.002)?<?Cd (7.279)?<?Ni (72.663)?<?Zn (35.622)?<?Pb (135.863)?<?Cr (167.604)?<?Mn (183.904)?<?Fe (1138.551) for the wet season. The EF which is an indication of whether metal concentrations are due to anthropogenic activities shows enrichment at all site for the metals Cr, Pb, and Cd in the wet seasons. However, only 4 out of the 27 sites showed Ni enrichment in the wet season. Contrary to the wet season, only Pb and Cr recorded enrichment at all sites during the dry season. Fifteen out of the 27 sites recorded Cd enrichment and 24 out of the 27 sites recorded Ni enriched during the dry season. None of the sites were enriched with Fe, As, Zn, and Mn in either the dry or wet seasons. For both dry and wet seasons, the pollution load index for all the sites except one was at the background levels which is a sign of non-deterioration of the sites studied. In the wet season, the calculated Igeo reveals that the study area is not contaminated with respect to As, Zn, Fe, and Mn; uncontaminated to moderately contaminated with Cd; moderately contaminated with Cr; uncontaminated to moderately to heavily contaminated with Ni; and moderately to heavily contaminated with Pb. The dry season Igeo results reveal non-contamination of the study area with respect to As, Fe, and Mn; uncontaminated to moderately contaminated with Zn; moderately contaminated with Cr; uncontaminated to heavily contaminated with Cd; uncontaminated to extremely contaminated with Ni; and moderately to extremely contaminated with Pb. The high levels of Cd, Pb, and Cr in all the sites are due to unregulated illegal mining activities occurring in and around the study area. It is hoped that this study will prompt the basin management board to improve their management strategies in controlling unregulated illegal mining in the basin sediments.