Metal partitioning in sediment pore water from the Ondo coastal region,Nigeria

Distribution and equilibrium partitioning of metals (Cd, Cu, Cr, Fe, Ni, Pb, Mn, and Zn) between pore water and surface sediments at the Ilaje coast of Ondo State, Nigeria, were studied. The Ilaje River can be one of the interesting research locations because of its economic nature and history of oil pollution. Seasonal variations were observed to investigate possible variations in the availability of metals for organisms throughout the year. The concentrations in both sediments and pore water during the dry and wet seasons were as follows: Cu?>?Fe???Mn?>?Pb?>?Ni?>?Cr?>?Cd?>?Zn. The pore water–sediment partition coefficient (K _p) showed that Zn and Cd were highly mobile while Fe and Cu have restricted mobility. Dissolved organic carbon (DOC) in pore water had a strong influence on mobility and bioavailability of all the metals (p?K _oc), increased levels of Fe and Cu were linked to lithological origin. Concentrations of Pb and Ni were associated with petroleum-related sources. The significance of the field-based techniques for ecotoxicological purposes is discussed.     

Trace metals in fish,sediment and water from the south west coast of the Arabian sea,Pakistan

Concentrations of ten metals (As, Cd, Cr, Cu, Fe, Mn, Ni, Pb, Zn and Hg) in the edible muscle of Arius maculatus captured from eight different near‐shore and off‐shore sites off the south west coast of the Arabian Sea, Pakistan, were determined by atomic absorption spectrophotometry. Relevant water and sediment samples from the sites were also analysed for the metals. Zinc showed the highest metal concentration (6.763 μg/g, wet weight) in the muscle of the fish, while Mn and Hg showed lowest level (0.019 μg/g, wet weight). Of all the metals investigated, largest scatter (measured as σ) was observed for Zn (σ = 2.058 /μg/g) in fish muscle, for Fe and Mn in sediment (σ = 27481 and 44.50 μg/g) and for As in water (σ = 0.270 μg/L). The metal distribution data pertaining to water, fish and sediment were examined on the basis of simple metal correlations. The statistical study revealed that Ni, Cr, Pb and Cu had significant positive correlations (r > 0.830 at ρ = 0.01). The finding substantiated a trace metal concentration gradient in the area, thereby indicating that the local marine environment is contaminated by anthropogenic sources.     

Heavy metal concentration in water,sediment, and tissues of fish species (Heteropneustis fossilis and Puntius ticto) from Kali River,India

The river Kali has been one of the major recipients of industrial effluents in the Muzaffarnagar district of western Uttar Pradesh. The present studies revealed the occurrence and bioaccumulation of heavy metals (Cd, Cr, Pb, Zn, Mn) in riverine water, sediment, and muscles of two fish species, Heteropneustis fossilis and Puntius ticto. Data showed that the order of occurrence of heavy metals was Pb > Zn > Mn > Cr > Cd in river water, Mn > Zn > Pb > Cr > Cd in sediment, Zn > Mn > Cr > Cd > Pb in Puntius ticto and Cr > Zn > Mn > Cd > Pb in Heteropneustis fossilis. Results indicate that the concentrations of Cd, Pb, and Zn in river water, Pb, Zn, and Mn in sediment, Cd, Cr, Pb, and Zn concentration in muscles of Puntius ticto and Cr, Pb, and Zn concentration in in muscles of Heteropneustis fossilis are higher than the permissible standard limits. The presence of heavy metals contributed to toxicity in different organs of fish in River Kali. The bioaccumulation of heavy metals in different biotic organisms in river ecosystem may have adverse consequences on humans and livestock.     

Physicochemical characteristics and distribution of some metals in the ecosystem of Lake Nasser,Egypt

To know the interrelationship between some metals in different ecosystem components (water, sediment, aquatic plant and fish), many samples from these components were collected from four bights at the Nasser Lake, Egypt, and analyzed for Fe, Mn, Zn, Ca, Mg, Pb, Cd, Ni, Co, Cu and Cr using atomic absorption spectrophotometer. Different distribution factors (bioaccumulation factor – BF, discrimination factor – DF and enrichment factor – EF) were applied on the results of analysis. Data showed that the relatively high concentration of measured metals in water samples are derived from fish farms, and discharge of tourism and trade ships. Applying single leaching sequential technique on sediment samples, using different extracting solutions, revealed a strong ability of trace metals to adsorb on or co-precipitate with amorphous Fe/Mn oxides. High concentrations of Fe, Mn, Co and Ni were measured in the intestine while high Cd and Cr concentrations were recorded in the stomach in both Tilapia (nilotica and galilea). Tilapia galilea accumulated high Pb, Cu and Zn concentrations in their stomach, while in nilotica high concentrations of Pb, Cu and Zn were measured in the intestine, liver and muscles, respectively. Myriophyllum spicatum (an aquatic plant) in the lake recorded high concentrations of Fe, Mn and Zn. Bioaccumulation factors of studied elements in the different bights components indicate that the elevated concentration of measured elements in the aquatic plant and Tilapia (nilotica and galilea) are derived from water, reflecting the increase of human activities in Nasser Lake in recent years. However, the present study concluded that all the elements studied were still below the natural back-ground levels, except Zn and Cu.     

Assessment of heavy metals in water,sediment, Anabas testudineus and Eichhornia crassipes in a former mining pond in Perak,Malaysia

The concentrations of Al, As, Cd, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Sn and Zn were analysed in water, sediment, muscle of climbing perch fish (Anabas testudineus), and tissue of water hyacinth plants (Eichhornia crassipes) collected from a former tin-mining pond in Perak, Malaysia. The monitoring was performed during the minimum and maximum rainfall periods. The concentrations of As, Cr, Fe, Ni, Pb and Zn in water exceeded the permissible limits set by the Interim National Water Quality Standards for Malaysia (INWQS). The risk index (RI) values determined for As, Cd, Cr, Cu, Hg, Pb and Zn in sediment presented a low degree of ecological risk. The order of the top three heavy metals measured in fish muscle was Zn?>?Fe?>?Al. The estimated daily intake (EDI) of As and Cr exceeded the allowable limits in both rainfall periods. The bioconcentration factor (BCF) and translocation factor (TF) values of Zn in water hyacinth were 24.865 and 3.214, respectively. The concentrations of Cu and Zn in the plant tissue were significantly correlated (p?<?.05) with the concentrations of heavy metals in water. Overall, climbing perch and water hyacinth are excellent bioindicators of environmental impacts on water bodies.     

宝鸡城市街尘、土壤及河流沉积物重金属形态迁移特征

在宝鸡城市街尘、土壤及河流沉积物基本理化性质和重金属元素含量分析的基础上,重点研究了重金属元素在街尘、土壤及河流沉积物中的赋存形态和迁移特征.结果表明:在街尘中Cu主要以可氧化态和残余态形式存在,Pb主要以可还原态和可氧化态形式存在,Zn和Cd主要以乙酸可提取态形式存在,Mn、Fe、Co、Ni和Cr主要以残余态形式存在...     

Heavy metals in water of the rivers Hooghly and Haldi at Haldia and their impact on fish

The paper deals with the measurement of five heavy metals viz., Cd, Cu, Mn, Pb and Zn in water of the rivers Hooghly and Haldi at Haldia during June 1999 to October 2002. The industrial effluent out fall (OF) at Patikhali, Haldia was also taken as sampling site along with above out fall (AOF) and below out fall (BOF) sites. Most of the metals exhibited their least concentration at the sampling site above the Haldia industrial area of river Hooghly. The average concentrations of the studied metals were Cd 2-14, Cu 5-19, Mn 8-88, Pb 17-41 and Zn 22-37 microg l(-1). Comparison of the data with the Criterion Continuous Concentration (CCC) of USA revealed that Cd, Cu and Pb were the pollutants present at alarming level to disturb the aquatic life process in the zone. The effect was found to reflect on the tissue level aberrations in the residential fishes. The other two metals viz., Mn and Zn were probably less harmful to the aquatic ecosystem. In India, necessity is felt to develop the CCC values, which will be more appropriate for protection of aquatic environment than comparing with drinking water standards.     

Trace metals in fish of economic interest from the west of Alexandria,Egypt

The concentration of some heavy metals (Cd, Cu, Fe, Mn, Ni, Pb, and Zn) in the muscle, liver, and gills in eight fish species, Caranx crysos, Euthynnus alleferatus, Scomberomorus commerson, Sphyraena viridensis, Sargus sargus, Siganus rivulatus, Mugil species, and Sardinella aurita were collected seasonally from the Mediterranean Sea in the region of Alexandria. The highest concentrations of Cd, Cu, Fe, and Zn were measured in liver tissue, while gill tissue yielded the highest concentrations of Mn, Ni, and Pb. Muscle is the organ of poor accumulation factor for all metals under investigation. Concentration of cadmium in muscle in Mugil species exceeds the permissible limit in summer, while Siganus rivulatus exceeds it in the summer and autumn seasons. On the other hand, copper, nickel, lead, and zinc are still much lower than the permissible levels. The metal pollution index (MPI) for metals was studied, revealing that Siganus rivulatus, Mugil species and Sardinella aurita had the highest MPI. Provisional tolerable daily intake (PTDI) indicates that the concentration levels of Cd, Cu, Fe, Mn, Ni, Pb, and Zn in the muscle of all fish species under investigation are much lower than recommended PTDI values, and accordingly there is no risk for the human consumption of these fish species.     

Assessment of nutrients and heavy metals enrichment in surface sediments from Taihu Lake,a eutrophic shallow lake in China

Concentrations of the nutrients (TN and TP), phosphorus fractions and heavy metals (Co, Cr, Cu, Mn, Ni, Pb, Sr, Ti, V, Zn and Hg) in 40 surface sediment samples collected from Taihu Lake, a eutrophic shallow lake in China, were determined. The results showed that the northwest region of the lake possessed higher concentrations of TN and TP, as well as the similar spatial distribution trend in the water column. This should be related to excessive anthropogenic input from industrial effluents and domestic sewage in surrounding areas. Similarly, the concentrations of P fractions exhibited significant regularity. In addition, except for Sr showing low concentration, the rest of the heavy metals in the surface sediments had two- to four-folds of magnitude of the concentrations compared with the reference values in earth's crust. In the past decade, concentrations of heavy metals had undergone different levels of variations. Principal component analysis (PCA) and enrichment factors (EFs) of the compositional data aiming at heavy metals showed that Taihu Lake was slightly exposing to heavy metal contamination except Sr. High concentrations of heavy metals were ascribed to the discharge of untreated and partially treated industrial waste water via rivers. Co, Cr, Cu, Mn, Ni, Pb, V and Zn positively correlated with each other (R = 0.78–0.92), that indicated they had analogous sources and/or kindred geochemistry characteristics. Differing from nutrients, randomness in the space indicated that heavy metals had a complex distribution.     

Accumulation of heavy metals in soil and paddy crop (Oryza sativa), irrigated with water of Ramgarh Lake,Gorakhpur, UP,India

Heavy metals, a highly polluting group of constituents known to exert adverse effects, tend to accumulate in living organisms. The objective of this study was to determine the accumulation and translocation of heavy metals in soil and in paddy crop irrigated with lake water compared to soil and paddy crop irrigated with bore-well water. The quantities of heavy metals (Cd, Cr, Cu, Pb, Zn, As, Mn, and Hg) were determined in different parts of rice plants (Oryza sativa). Results revealed that the mean levels of soil Cd, Cr, Pb, Zn, As, Mn, and Hg in experimental soil and in different parts of rice plant (root, straw, and grain) were higher than the control except for Cu. The content of eight toxic metals was significantly higher in root than in aerial parts of the rice (straw and grains). Rice roots were enriched in Cd, As, Hg, and Pb from the soil, while Cr, Cu, Zn, and Mn were hardly taken by the roots. Bioaccumulation factor for Hg was significantly higher than other heavy metals. Metal transfer factors from soil to rice plants were significant for Cd, Cr, Cu, Pb, Zn, As, Mn, and Hg. The concentrations of metals in lake water were found to be within the permissible limit of Indian standard prescribed by Central Pollution Control Board (2000), except for Hg and As, which were higher than the limit of Indian standard. However, the concentrations of heavy metals in soil and rice grains were still below the maximal levels, as stipulated by Indian Prevention of Food Adulteration Act (PFA, 1954) and World Health Organization (WHO, 1993) guidelines.     

Metal accumulation in sediment,water, and freshwater fish in a Dam Lake

Metal concentrations were determined in water, sediment, and freshwater fish samples (Squalus cephalus, Barbus esocinus, and Barbus xanthopterus) collected from Karakaya Dam Lake, Turkey, to estimate the risk of human consumption and pollution. Metal concentrations differed between the species (p??Zn?=?Cu in water and Fe?>?Zn?>?Mn?>?Ni?>?Cu in sediment. In general, the accumulation order of elements in the tissues all of the species sampled were found as Fe?>?Zn?>?Se?>?Mn?>?Cu?>?Ni?>?Cd in muscle, Zn?>?Fe?>?Mn?>?Se?>?Cu?>?Ni?>?Cd in gills, Fe?>?Zn?>?Se?>?Mn?>?Cu?>?Ni?>?Cd in liver and gonad, and Zn?>?Fe?>?Cu?>?Mn?>?Se?>?Ni?>?Cd in kidney. It was concluded that the fish from the dam lake are not heavily burdened with metals, but they should be controlled periodically to avoid excessive intake of trace metals by humans, and to monitoring the pollution of aquatic environment.     

凡口铅锌矿湿地系统沉积物中重金属的分布

研究了用于处理凡口铅锌矿选矿废水的宽叶香蒲(Typha latifolia)人工湿地系统沉积物中重金属Pb、Zn、Cu和Cd的分布。沉积物略呈碱性,在各层沉积物中,DTPA-Zn质量分数高于DTPA-Pb质量分数。冬季(11~12月)湿地系统中3个处理池进水口的沉积物结合水中的Pb、Zn、Cu和Cd质量分数与春季(1~3月)的相比较,有显著的差异。湿地处理系统中Pb、Zn、Cu和Cd主要沉积在表层土壤中;但3个处理池入水口和出水口不同深度的沉积物pH值没有显著差异(p<0.05),表明pH值与重金属含量并不存在相关性。     

电子废物不当处置的重金属污染及其环境风险评价 Ⅳ. 电子废物不当回收地区流域水体沉积物的重金属污染

为了解电子废物不当处置活动对小流域内水体沉积物金属污染的影响,采集了位于广东省清远市龙塘镇和石角镇的电子废物焚烧和酸解活动核心区内水塘和水库的0～40cm沉积物以及附近河流大燕河表层(0～5cm)沉积物样本,分析了样本中的金属(水塘、水库:Zn、Cu、Pb、Cd、Cr;大燕河:Zn、Cu、Pb、Cd、Cr、Ni、Mg、Mn)含量.作为对照,对珠江口伶仃洋沉积物中的5种重金属(Zn、Cu、Pb、Cd、Cr)含量也进行了分析.结果表明,1)在核心区内,5种重金属的平均含量在接近酸解作坊的水塘沉积物中呈Cu(766.16mg·kg-1)>Zn(181.12mg·kg-1)>Pb(129.56mg·kg-1)>Cr(1.89mg·kg-1)≈Cd(1.12mg·kg-1),在其下游的水库沉积物中呈现相同的规律,但水塘沉积物的Cu、Zn、Pb含量均高于水库.水塘、水库沉积物重金属含量分布规律明显不同于伶仃洋沉积物,与伶仃洋沉积物相比,核心区水体沉积物Cu含量特别高,是伶仃洋沉积物的7～17倍,Pb和Cd则分别是伶仃洋的2.3～3.0倍和1.9～2.4倍,Zn、Cr含量与伶仃洋沉积物相近.2)Zn含量在核心区水体沉积物中均呈现出在20.0～30.0cm深度最高的趋势,Cu、Pb含量在水库沉积物中也有类似的表现,说明该深度的沉积物可能是电子废物回收处置活动最频繁的时期形成的,近年来随着政府取缔工作的加强,电子废物非法处置活动的减少,Zn、Cu、Pb含量有明显的下降.3)大燕河沉积物中6种重金属(Zn、Cu、Pb、Cr、Cd、Ni)的总含量表现为中游下段(1261.3mg·kg-1)>中游中段(1049.2mg·kg-1)>中游上段(401.8mg·kg-1)>上游(364.6mg·kg-1)>下游(215.4mg·kg-1).Cu、Zn、Pb和Cr含量均在中游下段的沉积物中出现最大值,次大值出现在中游中段,Ni、Cd在中游中段出现最大值,次大值出现在中游下段.中游中、下段沉积物中金属含量最大值和其上游(或中游上段)河段含量最低值的比值呈现Cu(10.1)>Cr(7.8)>Zn(3.8)>Cd(2.0)>Pb(1.9)>Ni(1.8),显示这些重金属主要从中游中、下段进入大燕河沉积物,其中Cu污染最为严重,而Cr污染可能与水土流失或当地其他活动释放的Cr有关.4)比较流域内土壤和各种沉积物以及伶仃洋沉积物中重金属的构成比例发现,核心区土壤和沉积物以及大燕河沉积物中的重金属具有明显的同源性.随着离源区距离的增加,重金属的构成比例中最明显的变化是Cu的比例下降以及Zn的比例上升。     

Levels and distribution of trace metals in surface sediments from Kongsfjorden, Svalbard, Norwegian Arctic

Trace metal contents (Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb and Zn) have been measured in 27 surface sediment samples collected from Kongsfjorden, Svalbard, Norwegian Arctic. The analyses yielded concentration values (in mg kg^?1) of 0.13–0.63 for Cd, 11.89–21.90 for Co, 48.65–81.84 for Cr, 21.26–36.60 for Cu, 299.59–683.48 for Mn, 22.43–35.39 for Ni, 10.68–36.59 for Pb, 50.28–199.07 for Zn and 8.09–65.34 for Hg (in ng g^?1), respectively. Relative cumulative frequency method has been used to define the baseline values of these metals, which (in mg kg^?1) were 0.14 for Cd, 13.56 for Co, 57.86 for Cr, 25.14 for Cu, 364.08 for Mn, 26.22 for Ni, 17.46 for Pb, 70.49 for Zn and 9.76 for Hg (in ng g^?1), respectively. The enrichment factor analysis indicated that Hg showed some extent of anthropogenic pollution, while Pb, Zn and Cd showed limited anthropogenic contamination in the study areas.     

Speciation of Heavy Metals in Floodplain and Flood Sediments: a Reconnaissance Survey of the Aire Valley, West Yorkshire, Great Britain

A five-step sequential extraction technique was used to determine the chemical association of heavy metals (Pb, Zn, Cu and Cd), with major sedimentary phases (exchangeable, surface oxide and carbonate, Fe and Mn oxides, organic and residual metal ions), in samples from floodplain and recent flood sediments of the River Aire, West Yorkshire. Analysis indicates that metals Pb and Zn are primarily associated with the Fe and Mn oxides, Cu with the organic fraction and Cd with exchangeable and surface oxide and carbonate metal ions. Knowledge of the chemical speciation of heavy metals in river sediment, despite the procedure's inherent limitations, facilitates an understanding of their bioavailability, storage and remobilisation in floodplain and river channel environments.     

Geochemical distribution of trace element concentrations in the vicinity of Boroo gold mine, Selenge Province, Mongolia

The environmental impacts of Boroo gold mine project in Mongolia was evaluated by chemical characterization of trace element concentrations in water, soils and tailing dam sediment samples. The results showed that concentrations of B, Cd, Ni and Se in the water samples were within the accepted levels of the Mongolia water quality standard (MNS4586: 1998). However, the concentrations of Al, As, Cu, Mn, Fe, Pb, U and Zn were higher than the maximum allowable concentration especially in the monitoring and heap leach wells. The average concentrations of As, Cd, Cu, Ni, Pb and Zn in the tailing dam sediment were 4419, 58.5, 56.0, 4.8, 20.6 and 25.7 mg/kg, respectively. Generally, arsenic and heavy metals in the soil samples were within the acceptable concentrations of the soil standard of Mongolia (MNS 5850: 2008). The chemical characterization of As solid phase in tailing dam sediment showed that the majority of As were found in the residual fraction comprising about 74% of total As. Assessing the potential risk to humans, simple bioavailability extraction test was used to estimate bioavailability of arsenic and heavy metals, and the concentrations extracted from tailing dam sediment were; 288.2 mg/kg As, 7.2 mg/kg Cd, 41.1 mg/kg Cu, 13.5 mg/kg Pb, 4.7 mg/kg Ni and 23.5 mg/kg Zn, respectively. From these results, the Boroo gold mine project has presently not significantly impacted the environment, but there is a high probability that it may act as a source of future contamination.     

Toxicity of metals to tadpoles of the common Sunda toad,Duttaphrynus melanostictus

Tadpoles of the common freshwater Sunda toad, Duttaphrynus melanostictus (Amphibia, Bufonidae), were exposed for a 4-day period under laboratory conditions to copper (Cu), cadmium (Cd), zinc (Zn), lead (Pb), nickel (Ni), iron (Fe), aluminum (Al), and manganese (Mn) at various concentrations. Mortality was assessed and median times of death (LT₅₀) and lethal concentrations (LC₅₀) were calculated. LT₅₀ and LC₅₀ increased with the decrease in mean exposure times and concentrations for all metals. LC₅₀ (96?h) for Cu, Cd, Zn, Pb, Ni, Fe, Al, and Mn were 0.03, 0.3, 4.2, 1.5, 8.8, 0.4, 1.9, and 39?mg?L^?1, respectively. Cu was the most toxic to D. melanostictus, followed by Cd, Fe, Al, Pb, Zn, Ni, and Mn (Cu?>?Cd?>?Fe?>?Al?>?Pb?>?Zn?>?Ni?>?Mn). Duttaphrynus melanostictus is similarly sensitive to these metals as other amphibian tadpoles.     

Temporal variation of metals in the seagrass Posidonia australis and its potential as a sentinel accumulator near a lead smelter

Temporal variation in the concentrations of Cd, Cu, Mn, Ni, Pb and Zn in leaves of the seagrass Posidonia australis was studied at three sites near a lead smelter on the shore of Spencer Gulf, a large hypersaline marine embayment in South Australia, on four occasions from October 1980 to September 1981. Concentrations of Cd, Mn, Pb and Zn of up to 541, 537, 379 and 4241 g g^-1, respectively, were found in leaves collected from the site nearest to the smelter. A substantial temporal variation in the concentrations of these metals in samples from all sites resulted from the combined effect of leaf age and collection strategy. Concentrations of Cd, Cu and Zn in the leaf epibiota were lower than those in the leaves, but the reverse was true for Mn and Ni. The use of seagrass leaves as sentinel accumulators for Cd, Pb and Zn must be based on collections made at the same time of year, or otherwise account for the effect of leaf age on concentrations of the metals in the samples.     

Trace metal pollution in a Le'an River tributary affected by non-ferrous metal mining activities in Jiangxi Province,China

Sediment and water samples from the Jishui River were tested to determine the concentrations of As, Cd, Cu, Mn, Pb and Zn. The concentrations of Cu, Mn and Zn in the surface water close to the Fujiawu copper mine greatly exceeded the criteria maximum concentrations (CMC) of the Environmental Protection Agency. The concentration of Zn at a site near the small smelters also exceeded the CMC. Cd concentrations in surface water samples from 69% of the sampling sites were significantly higher than the CMC. Heavy Cd pollution of surface water resulted from the Shuanghua Smelter, the lead smelter, the lead–zinc mine and the small smelters downstream. The total metal concentrations in the majority of the sediment samples substantially exceeded the probable effect levels (PEL). Levels of As, Cd, Cu and Zn in surface sediment of the site close to the Shuanghua Smelter were 20 times higher than the PELs. The levels of Pb in sediment of the downstream sites near the small smelters and the lead–zinc mine were also elevated. Based on the results of the BCR sequential extract procedures and the risk assessment code, the levels of Cd, Cu, Mn and Zn in the sediment posed high risk.     

Seasonal Variations of Trace Metal Chemical Forms in Bed Sediments of a Karstic River in Lebanon: Implications for Self-purification

Although Lebanon has abundant water, its rivers are polluted and aquifer water mismanaged. Effective river water usage requires an understanding of the geochemistry of polluting metals in catchments. Climate is “Mediterranean”: wet winters and dry summers. Active sediment flushing is restricted to winter high discharge episodes. Except in winter, water column pollutants are removed by precipitation or sorption to the surface of static bed sediments. Hence (1) does winter flushing of contaminated sediment and replacement by clean sediment favour self purification? (2) does the distribution of metals between extractable fractions change seasonally and thereby affect metal bioavailability ? Results on the distribution of metals are reported for Fe, Pb, Zn, Cu and Cd in bed sediments from Nahr Ibrahim (a karstic river) for summer and winter. A Tessier-like sequential extraction scheme was applied to samples (< 75 μm) for five locations along a 13 km stretch to the sea. Water pH was above 8.2 at all locations implying a very low solubility for Fe. Sediment was derived from catchment soils and limestone. Total sediment Fe increased in winter at all sites following deposition of eroded soil from upstream. Cadmium, Cu and Pb derived from polluting sources; the sources of Zn were more complex. Dilution by clean sediment explained winter reductions in total Cd, Cu and Pb; Zn changes were less consistent. Iron occurred mostly (> 77 sum of fractions) in the residual fraction compared with 6– 31 for pollutants; residual Cu and Zn showed a small increase in winter whereas Cd and Pb did not change. All readily exchangeable metals decreased in winter and the carbonate bound forms predominated in both seasons. Nahr Ibrahim has a high capacity for self purification and metal resolubilisation from sediment will be limited by the solubility of carbonate forms.