Heavy Metals In Stream Sediments Research Articles

Assessment of ecological and health risk impact of heavy metals contamination in stream sediments in Itapaji-Ekiti, SW Nigeria

BackgroundHeavy metal contamination in aquatic ecosystems is a major environmental and health concern globally. This study assessed the ecological and health risks associated with heavy metal pollution in stream sediments in Itapaji-Ekiti, Southwest Nigeria. The study contributes collectively to a comprehensive understanding of the geochemical dynamics and contamination factors affecting the studied stream sediments. MethodsHeavy metals study was conducted on stream sediments within the geographical confines of sheet 244, Ado map. Seventeen stream sediment samples were obtained from various sites and subjected to analysis to determine the concentrations of heavy metals such as lead (Pb), copper (Cu), zinc (Zn), chromium (Cr), cadmium (Cd), barium (Ba), arsenic (As), nickel (Ni) and vanadium (V) using X-ray Fluorescence (XRF). The results showed that the concentrations of these metals exceeded permissible levels at most sampling sites, indicating significant contamination of the stream sediments. The concentrations and pollution levels of the heavy metals from selected sampling sites were documented for ecological and health risk evaluations. ResultThe findings revealed that the concentrations of these metals surpassed acceptable thresholds at the majority of sampling locations, indicating significant contamination of the stream sediments. The concentrations of heavy metals, specifically Cr and Cd, exhibit moderate contamination, while Pb and Ba demonstrates a significant contamination factor with moderate to extreme degree of contamination. Several ecological risk indices were calculated to evaluate the potential ecological risks. The results revealed that the stream sediments posed considerable to very high ecological risks at most sites based on the risk quotient, contamination factor and pollution load index. The non-carcinogenic and carcinogenic risk assessments for heavy metals in stream sediments exposed potential health risks, especially for children, indicating the need for protective measures. The cumulative cancer risk, particularly for adults, raised concerns about the overall health implications of prolonged exposure to the heavy metal concentrations in the streams. ConclusionThe study also evaluated ecological and health risks, revealing potential risks from heavy metals. Hazard and cancer risk assessments suggested the increasing potential of heavy metals to pose health risks, particularly for inhabitants of the area.

Contamination, Sources, Distribution and Risk Evaluation of Heavy Metals in Stream Sediments of Mewongo Gold District, Nyong Group, Cameroon

Contamination, Sources, Distribution and Risk Evaluation of Heavy Metals in Stream Sediments of Mewongo Gold District, Nyong Group, Cameroon

Geochemical evaluation and environmental risk assessment of heavy metals: A case study from Ireland using Tellus stream sediment data (2011–2017)

A comprehensive assessment of the distribution, spatial mapping and ecological risk of heavy metals in stream sediments of 17 counties of Ireland based on the Tellus geochemical survey programme in Ireland was carried out. Average trace metal concentrations of chromium (Cr), nickel (Ni), copper (Cu), lead (Pb), zinc (Zn), vanadium (V), cobalt (Co), arsenic (As), and major and minor oxides iron oxide (Fe2O3), manganese oxide (MnO) in the stream sediments were above the background values, but lower than Irish sediment quality guidelines for livestock and Canadian sediment quality guidelines (ISQG); threshold effect level (TEL) and probable effect level (PEL). 69.65% of Ni, 22.13% of Zn, and 96.7% of Pb samples exceeded the low-effect-range (ERL) values, whereas only 21%, 1.80% and 0.69% of the same elements exceeded the median effect range (ERM) values. Hotspots of Zn (>12000 mg kg−1), Pb (>10,000 mg kg−1), Fe2O3 (61.38%), MnO (26%), Cr (>2300 mg kg−1) and Ni (874.2 mg kg−1) were observed at Wicklow, Dublin, Mayo, Galway and Cavan counties. Catchment geochemistry was identified for the presence of heavy metals in the stream sediments. The geo-accumulation index (Igeo) indicated Kildare to be the least contaminated county with Igeo < 0 for Cr, Ni, Cu, Zn, Pb and As for 50% of the samples. The enrichment factor (EF) indicated that some sites located in Mayo and Donegal were highly contaminated. PInemerow followed the trend, Tipperary > Dublin > Waterford > Monaghan > Donegal > Wexford > Galway > Wicklow > Cavan > Meath > Kilkenny > Leitrim > Mayo > Louth > Sligo > Kildare > Carlow. Based on potential ecological risk index (PERI), 83.1% of the sites posed low ecological risk (PERI <150), 11.9% sites posed moderate risk (150 < RI < 300) and high ecological risk was posed by 0.3% (PERI >1200) of the sites. Lithology, topography and anthropogenic factors influenced the distribution and ecological risks of heavy metals. Non-carcinogenic and carcinogenic risk for adults and children were above the recommended value.

Assessing the Environmental Impact of Artisanal Gold Mining Activities on the Waters and Sediments Around Meli, Northwestern Tigray, Ethiopia

The paper presents the environmental impact of artisanal gold mining activities on the waters and sediments around Meli, northwestern Tigray, Ethiopia. Stream sediment, water, and tailing samples were collected in the dry season in January of 2019 and analyzed for heavy metals Cu, Zn, Pb, and As. The physicochemical parameters (pH, EC, major cations, and anions) of a few water samples were also measured. Flame atomic absorption spectrometry was used to determine the level of the metals in stream sediments. The results show that tailing has the highest concentration of metals followed by the stream sediments. The least concentrations are recorded in water for all metals. Pb has the highest mean concentration of all heavy metals in stream sediments, waters, and tailing samples. The mean Geo-accumulation Index (Igeo) and Contamination Factor (CF) suggest that the sediment represents uncontaminated to moderately contaminated classes. Concentrations of Cu and Zn in the water samples are generally within the maximum allowable concentration of the WHO, whereas concentrations of Pb and As are above the limit. Metal Index for surface and groundwater suggests that the area is polluted with heavy metals Pb and As. The main sources of the metals are assumed to be the sulfide ores facilitated by natural weathering processes and artisanal mining activities like excavations, crushing, grinding, and amalgamation processes. The Gibbs and Durov plots show that major hydrogeochemical processes controlling the water chemistry are water-rock interactions with considerable mixing of water types.&#x0D; &#x0D;

ASSESSMENT OF TEMPORAL VARIATION OF HEAVY METALS IN SEDIMENTS OF WARRI RIVER, SOUTHWESTERN NIGERIA

Contaminated sediment poses a serious environmental problem, therefore knowledge of the concentration of heavy metals in stream sediments is very important because of their significance to aquatic life and human health. The concentration of heavy metals (Cd, Pb, Cr, As, Ni, Zn, Fe and Cu), in stream sediments of some parts of Warri River, Southwestern Nigeria were examined during the rainy and dry seasons using Atomic Absorption Spectrophotometer, in order to assess their contamination levels using the environmental contamination indexes; Geoaccumulation Index, Enrichment Factor (EF), and Contamination Factor (CF). For both the rainy and dry seasons, the results revealed average heavy metal concentrations obtained in all samples in the study area in the order As&gt;Cd&gt;Pb&gt;Ni&gt;Cr&gt;Zn&gt;Cu&gt;Fe. The trend in mean Igeo values was as follows: As (-0.66) &gt; Zn (-4.93) &gt; Cu (-5.8) &gt; Fe (-5.31) &gt; Cd (5.76) &gt; Pb (-6.35) &gt; Ni (11.25), showing that River Warri’s sediments were not polluted by heavy metals. Cu= Zn (0.08), Cd (0.34), Pb (0.02), As (0.01), and Ni (0.00) were the mean CF values across all measured locations, indicating a low contamination factor. The average EFs for the sediments were As (1.09) &gt; Cd (1.10) &gt; Cu (1.46) &gt; Zn (1.61) &gt; Pb (1.09) &gt; Ni (1.09) &gt; Fe (0.83), showing low enrichment (&lt;2). Evaluation of enrichment factor, geo-accumulation index and contamination factor values showed that the stream sediments of the study area were unpolluted. Heavy metals in the sediments were found to be linked to anthropogenic activities in the study region, according to the results of the hierarchical cluster analysis (HCA). The metal concentrations in the sediment were found to be elevated at some sampled points, it is therefore recommended that annual monitoring of the stream sediments of the study area is undertaken. Also, sustainable practices should be employed in order to conserve the resources of the Warri River.

Concentration, Spatial Distribution and Potential Ecological Risk of Heavy Metals in Stream Sediments of the Misiones Province, Argentina

One hundred and twenty-eight stream sediment samples were collected in the Misiones province of Argentina by the low-density geochemical mapping project of the China Geological Survey. The analyzed data were used to study the concentration, spatial distribution, local pollution level and potential ecological risk of eight heavy metals (As, Cd, Cr, Cu, Hg, Ni, Pb and Zn) by factor analysis, geoaccumulation index (Igeo), enrichment factor (EF) and the Hakanson’s potential ecological risk index (Eir and RI) methods. Results showed that the background values (median) of those elements were 2.97 ppm, 0.13 ppm, 212.60 ppm, 322.53 ppm, 0.013 ppm, 64.42 ppm, 12.58 ppm, and 198.85 ppm, respectively. Except for Hg, the contents of other elements were higher than the abundance of continental crust. The spatial distribution of Cu and Zn in stream sediments were consistent, while that of other elements were different. The factor analysis results implied that Cd, Cr, Cu, Ni and Zn were mainly affected by geological background and inherited the characteristics of regional parent rocks. Furthermore, Pb was not only controlled by natural conditions but also related to human activities, while As and Hg represented the anthropogenic sources, and their concentrations were affected by human activities. The results of Igeo and EF told us that Cu was heavily polluted in stream sediments; Pb and Zn were largely mildly polluted; As, Cr, Cd, Ni and Hg were mostly nonpolluted. The ecological risks were ordered as As &gt; Cu &gt; Cd &gt; Pb &gt; Hg &gt; Cr &gt; Ni &gt; Zn. In general, the potential ecological risk of heavy metals in the Misiones province was low, but As and Cu also have a high ecological risk at some sampling points, which should be considered.

Heavy Metal Pollution Assessment in Stream Sediments from Urban and Different Types of Industrial Areas in South Korea

ABSTRACT Stream sediments from heavily industrialized areas, including urban areas (SS), industrial complexes (US), petrochemical industries (PS), and the Onsan industrial complex (OS) in Korea, were studied to identify 19 heavy metals pollution status and the metal sources. The concentration of heavy metals, except for Li, Be, and Cs in the stream sediments from the Onsan industrial complex near the largest Cu/Zn/Pb smelting facilities, was 3 to 1,302 times higher than that in urban and other industrial areas. Moreover, owing to the smelting activity in the Onsan area, the degree of pollution by major metal products (e.g., Cu, Zn, Pb, Sn, Cd, Sb, Ag) and raw or additive materials (Cr, Ni, Mo, As, Hg) was significantly higher than that in other areas. Heavy metals in stream sediments near smelters greatly exceeded the screening levels (SEL), which could have adverse effects on the health of biota. These values also exceeded the cleanup screening levels of freshwater sediments in the USA. The highest pollution load index value of 47.8 was observed in the vicinity of the smelter (OS) and decreased in the following order: heavy industry (3.6, US) > petrochemical industry (2.4, PS) > urban streams (1.2, SS). Our results suggest that metal pollution in stream sediments might be caused by atmospheric dust generated during the smelting process, as well as sediment particles that accumulate and are washed off from impervious layers such as industrial facilities, raw material storage yards, and road surfaces.

Distribution, Association, and Ecological Risk Evaluation of Heavy Metals and Influencing Factors in Major Industrial Stream Sediments of Chandrapur District, Central India

The accumulation of heavy metals in stream sediment depends on various influencing factors. Sediments are aggregation of number of species along with organic debris. Accretion of heavy metals on sediment is the outcome of absorption by fine-grain inorganic particles of clays, adsorption of hydrous ferric and clays, and complexation with natural organic matters. These processes are regulated by different influencing factors including TOC and pH. This study reveals the spatial distribution of potentially toxic heavy metals (Cd, Hg, Pb, Co, Cu, Cr, Ni, and Zn) and assessment of contamination levels to find out the role of TOC and pH in distribution of heavy metal contamination in major industrial stream sediment in Chandrapur district, Central India. The pollution indices and multivariate statistical analysis were carried out to identify the correlation between various parameters. The concentration of anthropological derived heavy metals is higher in TOC-rich area. PCA and HCA study reveals that heavy metals are significantly correlated with TOC of the sediments, while Ni is associated with pH. Chromium shows the ambiguous behavior towards association with pH and TOC. The study also reveals that there is urgent need for assessment of Wardha River and Erai River basins because there could be hotpots for heavy metal contamination.

Geochemistry, risk assessment, and Pb isotopic evidence for sources of heavy metals in stream sediments around the Ulukışla Basin, Niğde, southern Turkey

Concentrations of selected elements (Al, Fe, Mn, Mo, As, Cd, Cu, Cr, Ni, Co, Pb, Sb, and Zn) and Pb isotope ratios were determined in 53 sediments from Alihoca, Gümüş, Horoz, and Çakıt streams around the south-central Taurides (Ulukışla Basin), Niğde, which is a known mining province in Turkey. Several pollution and risk assessment indices were used to assess possible heavy metal pollution in the stream sediments and the associated potential ecological risks. Concentrations of As, Cd, Cu, Cr, Ni, Co, Pb, Sb, and Zn were elevated in the streams located near ancient mines, active mines, and slag piles in the area, suggesting an influence from mining activities. The pollution assessment indices indicated that the sediments were significantly polluted by As, Cd, Sb, Zn, and Pb and moderately polluted by Cu, Ni, Cr, and Co. The sediments show very high potential ecological risk with As, Cd, Sb, and Pb as the principal contributors. Ni, Cr, As, Pb, Zn, and Cd exceeded the probable effect concentrations in most of the samples implying that their concentrations may frequently affect sediment-dwelling organisms. Multivariate statistical analyses indicate that the accumulation of heavy metals in the stream sediments is due to an interplay of anthropogenic activities (mining and agrochemical application) and geogenic processes (weathering of bedrocks and supergene alteration of base metal-rich mineralization). Pb isotopic tracing indicates that total Pb in the sediments (206Pb/207Pb = 1.09–1.29) is primarily from weathering and dissolution of ultrapotassic rocks (206Pb/207Pb up to 1.20) and galena (206Pb/207Pb up to 1.21) from the Pb-Zn-Au deposits in the area with some anthropogenic input from mine slag piles (206Pb/207Pb = 1.10).

Evaluation of Heavy Metals in Stream Sediments from Abakaliki Pb – Zn Ore Mining Areas of Ebonyi State, Nigeria

This research is an assessment of toxic metals in stream sediments from the Abakaliki Pb-Zn mine area of Ebonyi state. Heavy metals in stream sediment samples were analysed using Atomic Absorption Spectrometer (AAS). Physicochemical parameters were determined show that pH is generally low (3.65) resulting from the dissolution of the sulphide Ore. The heavy metal mean trend indicates that Fe &gt; Zn &gt;Pb&gt; Cr &gt;Cu &gt; Ni &gt; AS &gt; Cd in the stream sediment samples. Fe, Zn, Cu, Pb and Cr were observed to be high. The variations for the heavy metals suggest that mining operation is responsible for the distribution and redistribution of chemical elements. The values of contamination factor for the stream sediment indicate moderate contamination for Cd, As and Ni while Fe, Zn, Pb, Cu and Cr show very high contamination. The result of enrichment factor (EF) using Fe concentration as normalizing value show that Ni, Cd, Cr, As, and Cu have depletion to mineral enrichment while Pb and Zn show moderate enrichment. The result of the Correlation analysis and principal component analysis ( R- Mode and Q-mode) applied to the data analysis show that Zn, Pb, Cd, Cu, and Cr heavy metals originated from similar sources but may have been influenced by mining operation while Ni and As are attributed to a geogenic source. Proper sewage disposal practice and soil remediation are recommended.

Integrated Characterization of Toxicity Distribution of Selected Heavy Metals in Stream Sediments Around Itakpe Iron Ore Mines, North Central Nigeria

The results of the analysis were subjected to five (5) indices: contamination factor (CF); Ecological risk factor (Eri); Enrichment factor (EF); index of geo-accumulation (Igeo) and anthropogenic factor (AF). The CF results showed that the River PomPom dry and wet season sediments were collected in February and July respectively from 0cm to 10cm depth. Stainless steel spoon was used to collect the samples. The sediment samples were packaged, labeled and refrigerated for onward transportation to the laboratory. All samples were oven-dried (50oC) for about 24 hours, sieved through -80 mesh. About 1.0g of each sample was digested, filtered and the filtrates were ready for heavy metal analysis using Atomic sediments were most contaminated with Fe in both seasons, least contaminated with Cd at dry season and Zn in wet season. The Eri factor revealed pollution hazard level of middle during wet season and tiny in dry season. Pb and Ni showed strong and middle hazard level during wet season and Cu revealed middle level during dry season. The enrichment factor indicated extremely enriched for Fe in all locations in both seasons while most heavy metals showed depletion to minimal enrichment. The Igeo for both seasons showed that Fe was moderately to highly polluted in all locations. During dry season, other heavy metals showed moderately to unpolluted while in wet season Cd, Ni and Pb indicated moderately to very highly polluted. In both seasons, the % AF was very high for Fe, Cu, Pb. The AF% was very high for Ni and Cd in wet season. All sites in both seasons have experienced deterioration but more in the wet season. From these indices, the stream sediments have been significantly contaminated with Fe, Ni, Pb and Ni in most locations in both seasons.

Anthropogenic contamination and risk assessment of heavy metals in stream sediments influenced by acid mine drainage from a northeast coalfield, India

The total concentrations and chemical partitioning of heavy metals in streambed sediments, collected around the Jaintia Hills coal deposit of northeast India, were studied using pollution indices and multivariate techniques to evaluate the risk and contamination levels from heavy metals and their possible origins. Results show that sediments close to mining sites have low pH (<4), high organic carbon, and contain significant amounts of Fe-oxyhydroxide phases (mainly, goethite and schwertmannite), which implies direct impact of coal mine drainage. The average concentrations of Fe, Cu, Co, Cd, Cr, and Zn exceeded the World average, and in some cases, Cd, Cu, Ni, and Cr concentrations exceeded the threshold effects level, which suggests they will be toxic to aquatic biota. Contamination factors (CF) show that the sediments are low to highly contaminated with Cd, Cu, Mn, Pb, Fe, and Zn and low to moderately contaminated with Co, Cr and Ni. The pollution load index (PLI), degree of contamination index (C deg) and Nemerow integrated pollution index (NIPI) show that the sediments are moderately to highly contaminated, with the extent of pollution greatest nearest to the collieries. The potential ecological risk index (RI) shows low to considerable ecological risk from heavy metals in the sediments, with Cd having the high potential of risk, which also agrees with the risk assessment code (RAC). Multivariate statistical analysis suggests that the concentrations of the heavy metals in stream sediments are strongly influenced by Fe-oxyhydroxide phases and organic carbon derived from anthropogenic sources, mainly coal mining activities. Although a significant proportion of the Cd, Mn, and Ni in the sediments are partitioned into exchangeable and organic fractions, a sizable amount of metals are also found in the Fe–Mn fraction, suggesting that Fe-oxyhydroxides play a dominant role in controlling metal mobility in these stream sediments.

삼보광산 수계 하천수질 및 퇴적토의 오염도 평가

BACKGROUND: Mine drainage from metal mining districts is a well-recognized source of environmental contamination. Oxidation of metal sulfides in mines, mine dumps and tailing impoundments produces acidic, metal-rich waters that can contaminate the local surface water and soil. METHODS AND RESULTS: This experiment was carried out to investigate the pollution assessment of heavy metal on the water quality of mine drainage, paddy soils and sediment in lower watershed affected by mine drainage of the Sambo mine. The average concentrations of dissolved Cd (0.018∼0.035 mg/L) in mine drainage discharged from the main waste rock dumps(WRD) was higher than the water quality standards (0.01 mg/L) for agricultural water in Korea. Also, the average concentrations of dissolved Zn, Fe and Mn were higher than those of recommended maximum concentrations (Zn 2.0, Fe 5.0, Mn 0.2 mg/L) of trace metal in irrigation water proposed by FAO (1994). The average contents of Pb and Zn in paddy soils was higher than those of standard level for soil contamination(Pb 200, Zn 300 mg/kg) in agricultural soil by Soil Environmental Conservation Act in Korea. Also, the concentrations of Cd, Pb and Zn in sediment were higher than those of standard level for soil contamination (Cd 10, Pb 400, Zn 600 mg/L) in waterway soil by Soil Environmental Conservation Act in Korea. The enrichment factor (EFc) of heavy metals in stream sediments were in the order as Cd>Pb>Zn> As>Cu>Cr>Ni. Also, the geoaccumulation index (Igeo) of heavy metals in stream sediments were in the order as Zn>Cd>Pb>Cu>As>Cr>Ni, specially, the geoaccumulation index (Igeo) of Zn (Igeo 3.1∼6.2) were relatively higher than that of other metals in sediment. CONCLUSION(s): The results indicate that stream water and sediment were affected by mine drainage discharged from the Sambo mine at least to a distance of 1 km downstream (SN-1, SN-2) of the mine water discharge point.

Distribution and environmental geochemistry of some heavy metals in stream sediments of Wadi Allaqi, South Eastern Desert of Egypt

The study focuses on the lateral distribution and the environmental geochemistry of seven heavy metals: Fe, Mn, Cu, Co, Ni, Pb, and Zn in addition to Al in the stream sediments of Wadi Allaqi. Forty-two samples were collected from the upstream, the midstream, and the downstream of this Wadi. Results of the grain size analysis show that the sediments of Wadi Allaqi are fine to medium sand. The heavy metals content reflects the weathering impact on the hinterland. The highest concentrations of Fe, Al, Mn, Cu, Pb, and Zn are recorded in the midstream that is dominated by clastics of felsic and intermediate composition. Moreover, the downstream, occupied by ultrabasic–basic rocks, shows the highest averages of Co and Ni. These results suggest that the felsic and intermediate rocks are the main source of the former metals, whereas the ultrabasic–basic rocks are the source of later two metals. All the analyzed heavy metals have average concentrations lower than their backgrounds, except for Co and Pb. The pollution level by these heavy metals has been evaluated using enrichment ratio (ER), pollution load index (PLI), and index of geoaccumulation (Igeo). The calculated values of ER, CF, PLI, and Igeo indicate that Wadi Allaqi sediments are almost pristine except occasional feeble pollution level by Co and Pb.

Lead and other heavy metals in stream sediments in the area of Meža valley

In the Meža valley, lead – zinc ore has been exploited and processed for more than 300 years, which has strongly influenced the environment. Previous investigations have shown increased concentrations of lead and some other metals. At the end of the 20th century, the Meža River was considered a stream with the highest concentrations of heavy metals in Slovenia. When the mine and processing plants ceased to operate, the direct transfer of heavy metals into the environment has strongly decreased. However, the deposits of poor ore and wastes from ore processing have remained as an indirect source of heavy metal pollution. From those places heavy metals have been washed out into the nearby streams, and carried into the Meža River and further into the Drava River. Chemical analysis of the Meža River and its tributaries has shown heavy pollution of the upper Meža River sediments with lead, zinc, molybdenum and cadmium, and partly with arsenic. In the lower Meža valley, those concentrations are mildly decreased. Concentrations of cobalt, chrome, copper and nickel are increased in the area around Ravne as a result of the ironworks industry. Mu{enik and Jan~arjev potok, both tributaries of the Meža River, contribute a high portion of heavy metal load to the Meža River. A specific case is Helenski potok, in which the concentrations of heavy metals strongly surpass the concentrations measured at all other locations. Although more than 10 years have passed since the mine and ore processing plant in the upper Meža valley were closed, the production has ceased and the rehabilitation measures have been taken, the environment in the upper Meža valley is still highly polluted.

Geochemical Distribution of Selected Heavy Metals in Stream Sediments Affected by Tannery Activities

This study describes the geochemical distribution and potential mobility of selected heavy metals in sediments affected by tanneries established in the Cadeia-Feitoria River basin, South Brazil. Surficial samples were taken at ten sites, in January 2000, during dry season. Metal contents were determined according to their association with main sediment phases by applying a sequential extraction scheme proposed by the ‘Community Bureau of Reference’ of the European Commission. In order to compare the results, total and partial extractions were performed, following analytical methods used by US EPA and US Geological Survey. Metals were analyzed in the silt/clay fraction, using inductively coupled plasma – optical emission spectrometry. The results indicate the following order of metal mobility: Ti (1%) < Al (5%) < Ni (6%) < Fe (10%) < Cu (20%) < Zn (28%) < Cr (49%) < Mn (76%). Manganese was highly mobile along the sampling sites, and mainly bound to exchangeable and reducible phases. Total Ti, Al, Fe, Cu, and Mn exceeded two or three times the average shale metal concentration, but generally reflected background conditions in the basin, where basalt rocks predominate. Ni and Zn were homogeneously distributed along the rivers, with concentrations comparable to the average shale and local concentration levels. Sediments affected by tanneries were enriched with chromium (geoaccumulation index = 2 and 3), preferentially associated to the oxidizable phase. The potential release of this metal and conversion to toxic forms seems closely related to the prevailing redox conditions. The relationship between data obtained from sequential extraction and from partial and total extractions are briefly discussed.

Heavy Metals in Stream Sediments from the Coquimbo region (Chile): Effects of Sustained Mining and Natural Processes in a Semi-arid Andean Basin

Active sediments from the Elqui River in Chile were sampled 4 times at 10 sites during 2000. Concentrations of Ag, Ba, Cd, Co, Cr, Hg, Mn, Mo, Ni, Pb, Sr, Ti, V, Al, Ca, Fe, K, Mg, Na, P, and S were normal. Zinc levels were clearly high, and those of Cu (hundred to thousands ppm) and As (tens to hundreds ppm) were highly anomalous. Dissolved Cu (0.1-12.7 ppm) and Zn (0.2-2.2 ppm) levels were also very high. The anomalies of the upper tributaries are due to the El Indio–Tambo Au-Cu-As district and large hydrothermal alteration zones at altitudes between 3500–4500 m. Lower on the river, old and active tailing waste deposits and on-going mining operations in the Talcuna Cu (Pb) district are responsible. Partially eroded tailing deposits in the alluvial plain of the Elqui River and its tributaries, and especially in the El Indio-Tambo district, after mine closure in 2000, warrant special attention.

A Role for Geomorphology in Integrated Catchment Management

Catchments (watersheds) are integrated through water movements. Water moves sediments; and the translocation of materials has geomorphic and pedological responses. Fertiliser and pesticide residues and other toxic substances are also transported by water, in solution and attached to sediment particles, affecting various ecological components of catchments. The insertion of pollutants is directly caused by land‐use practices. In turn, land uses are influenced by the pedo‐geomorphology of the catchments (uplands, valley sides, flood plains and terraces, spurs and hollows, convexities and concavities; position in the upper, middle or lower catchment; and by catenary relationships). Therefore catchment management must deal with interrelationships amongst human activities and various geomorphic elements. Several case study examples from southwestern Australia demonstrate the importance of geomorphology in catchment management. They include: rates of hillslope erosion and translocation of P in micro‐catchments within a drainage basin context; stream salinisation; accumulation of heavy metals in stream sediments; geomorphic elements influencing the spread of weeds and the erosion of access tracks; and some relationships between valley‐side land uses and stream morphology. The incorporation of these and other issues in a management strategy is then illustrated. Complex skills are involved in producing and implementing a management strategy, including but extending well beyond those of the geomorphologist.

Heavy metals in stream sediments from copper and gold mining areas in southern Brazil

This work is part of a research effort which is intended to identify natural and anthropogenic sources for metal contamination in gold and copper mining areas of the Camaquã River Basin, located in the shield region of the Rio Grande do Sul state. This particular study area is located in the upper Camaquã River Basin, where gold, copper and marble occurs. Stream bed sediments were collected during four sampling periods, between 1992 and 1994. Total Fe, Mn, Cu, Zn, Pb and Hg concentrations as well as TOC contents were determined in the silt-clay fraction of all collected samples. Sequential extractions were performed in some selected samples to evaluate geochemical phase associations and potential metal mobilities. A general increase in metal concentrations was observed in more recent sampling periods for Mn, Fe and Cu, especially in the copper mining area. Two groups of metals, Cu-Fe and Hg-Pb-Zn-Mn, presented some similarities in spatial distributions, but exhibited different geochemic behaviors in the gold and copper mining areas.

Influence of sampling strategy, lithology, vegetation and rainfall on metal background concentrations in sediment of the tropical Tuy River basin, Venezuela

The Tuy River basin, north-central Venezuela, was selected to study the influence of the sampling strategy and analytical methods, lithology, rainfall and vegetation on the background concentrations of heavy metals in stream sediments. Stream bed sediment samples (105) were collected during four years of the period 1979–1986 at 15 sites. The sediments were air-dried at room temperature and sieved through a − 120 mesh (125 μm) stainless-steel sieve. The concentrations of Fe, Mn, Co, Cu, Cr, Ni, Ph, Zn and Cd were determined by atomic absorption spectrometry after digestion with a hot (80°C) concentrated mixture of HNO 3, HClO 4 and HF. The coefficient of variation (CV) due to analytical methods was <10%, while the CV among tributaries ranged from 13% to 45%. This allows the establishment of background values with a low number of samples (< 10). Tributaries with CV > 60% indicate contamination or mineralized areas. The large difference in average concentration among the tributaries (CV = 29 − 110%) allows distinction between areas with different lithology and vegetation. The northern and southern areas of the Tuy River basin exhibit felsic and mafic lithologies, respectively. The southern area can be further divided in two subunits: the southwestern with savanna vegetation and the southeastern characterized by tropical rainforest. The highest concentrations of metals were found in the southern area (3 times the northern). Especially high values were measured in the southeastern subunit and are likely due to the metavolcanic and mafic bedrock lithologies, and the high weathering intensities associated with this tropical forest area.