Solid phase extraction of Cu(II), Ni(II), Pb(II), Cd(II) and Mn(II) ions with 1-(2-thiazolylazo)-2-naphthol loaded Amberlite XAD-1180

A new method for separation and preconcentration of trace amounts of Cu(II), Ni(II), Pb(II), Cd(II) and Mn(II) ions in various matrices was proposed. The method is based on the adsorption and chelation of the metal ions on a column containing Amberlite XAD-1180 resin impregnated with 1-(2-thiazolylazo)-2-naphthol (TAN) reagent prior to their determination by flame atomic absorption spectrometry (FAAS). The effect of pH, type, concentration and volume of eluent, sample volume, flow rates of sample and elution solutions, and interfering ions have been investigated. The optimum pH for simultaneous retention of all the metal ions was 9. Eluent for quantitative elution was 20 ml of 2 mol l(-1) HNO(3). The optimum sample and eluent flow rates were found as 4 ml min(-1), and also sample volume was 500 ml, except for Mn (87% recovery). The sorption capacity of the resin was found to be 0.77, 0.41, 0.57, and 0.30 mg g(-1) for Cu(II), Ni(II), Cd(II), and Mn(II), respectively. The preconcentration factor of the method was 200 for Cu(II), 150 for Pb(II), 100 for Cd(II) and Ni(II), and 50 for Mn(II). The recovery values for all of the metal ions were > or = 95% and relative standard deviations (RSDs) were < or = 5.1%. The detection limit values were in the range of 0.03 and 1.19 microg l(-1). The accuracy of the method was confirmed by analysing the certified reference materials (TMDA 54.4 fortified lake water and GBW 07605 tea samples) and the recovery studies. This procedure was applied to the determination of Cu(II), Ni(II), Pb(II), Cd(II) and Mn(II) in waste water and lake water samples.     

The efficiency of Amberlite XAD-4 resin loaded with 1-(2-pyridylazo)-2-naphthol in preconcentration and separation of some toxic metal ions by flame atomic absorption spectrometry

A selective method has been developed for the determination of trace amount of metal ions after preconcentration on 1-(2-pyridylazo)-2-naphthol loaded Amberlite XAD-4 resin. The chelating resin was characterized on the basis of infra red spectra, thermal and chemical stability, and hydrogen ion capacity. High preconcentration factor of 160?C400 up to a low preconcentration limit of 10 ??g L^???1 has been achieved for almost all the metals. The chelating resin was highly selective even in the presence of large concentrations of alkali and alkaline earth metals and various matrix components. Chromatographic separation of metal ions in binary mixtures has been accomplished. The analytical utility of the resin for metal ions was explored by analyzing natural water and standard reference materials.     

Solid phase extraction of Cd,Pb, Ni,Cu, and Zn in environmental samples on multiwalled carbon nanotubes

A simple and sensitive solid phase extraction (SPE) method on multiwalled carbon nanotubes (MWCNTs) is presented for the determination of cadmium, lead, nickel, copper, and zinc at trace levels combined with flame atomic absorption spectrometry. The effects of parameters like pH, sample volume, sample and eluent flow rates, eluent concentration, and volume and type of eluent on the recovery of trace elements was examined. The metals retained on the nanotube at pH 6.5 as α-benzoin oxime complexes were eluted by 10 mL 2 M HNO₃ in acetone. The influence of matrix ions on the developed method was also evaluated. The preconcentration factor of the method was found to be 50. The detection limits for Cd(II), Pb(II), Ni(II), Cu(II), and Zn(II) were found as 1.7, 5.5, 6.0, 2.3, and 2.4 μg L^?1, respectively. To test the accuracy of the method, the method was applied to TMDA-70 fortified lake water and Spinach 1570A standard reference materials. Addition recovery studies were applied to tap water and cracked wheat samples, and determination of the analyte elements was carried out in some food samples with good results.     

Solid phase extraction and determination of Cr(III) by spectrophotometry using cefaclor as a complexing reagent and FAAS

The present study reports on the application of modified groundnut shell as a new, easily prepared, and stable sorbent for the extraction of trace amount of Cr(III) in aqueous solution. 2-Hydroxybenzaldiminoglycine was immobilized on groundnut shells in alkaline medium and then used as a solid phase for the column preconcentration of Cr(III). The elution was carried out with 3 mL of 2 mol?L^?1 HCl. The amount of eluted Cr(III) was determined by spectrophotometry using cefaclor as a complexing reagent and by flame atomic absorption spectrometry (FAAS). Different experimental variables such as pH, amount of solid sorbent, volume and concentration of eluent, sample and eluent flow rate, and interference of other metal ions on the retention of Cr(III) were studied. Under the optimized conditions, the calibration curves were found to be linear over the concentration range of 13–104 and 10–75 μg?L^?1 with a detection limit of 3.64 and 1.24 μg?L^?1 for spectrophotometric method and FAAS, respectively. An enrichment factor of 200 and RSD of ±1.19–1.49 % for five successive determinations of 25 μg?L^?1 were achieved. The column preconcentration was successfully applied to the analysis of tap water and underground water samples.     

Risk assessment of trace metals in an extreme environment sediment: shallow,hypersaline, alkaline,and industrial Lake Acıgöl,Denizli, Turkey

The major and trace element component of 48 recent sediment samples in three distinct intervals (0–10, 10–20, and 20–30 cm) from Lake Ac?göl is described to present the current contamination levels and grift structure of detrital and evaporate mineral patterns of these sediments in this extreme saline environment. The spatial and vertical concentrations of major oxides were not uniform in the each subsurface interval. However, similar spatial distribution patterns were observed for some major element couples, due mainly to the detrital and evaporate origin of these elements. A sequential extraction procedure including five distinct steps was also performed to determine the different bonds of trace elements in the <?60-μ particulate size of recent sediments. Eleven trace elements (Ni, Fe, Cd, Pb, Cu, Zn, As, Co, Cr, Al and Mn) in nine surface and subsurface sediment samples were analyzed with chemical partitioning procedures to determine the trace element percentage loads in these different sequential extraction phases. The obtained accuracy values via comparison of the bulk trace metal loads with the total loads of five extraction steps were satisfying for the Ni, Fe, Cd, Zn, and Co. While, bulk analysis results of the Cu, Ni, and V elements have good correlation with total organic matter, organic fraction of sequential extraction characterized by Cu, As, Cd, and Pb. Shallow Lake Ac?göl sediment is characteristic with two different redox layer a) oxic upper level sediments, where trace metals are mobilized, b) reduced subsurface level, where the trace metals are precipitated.     

Comparison of leaching tests for the study of trace metals remobilisation in soils and sediments

Several leaching tests were applied and compared to study metal remobilisation on various unpolluted and contaminated soils and on several contaminated sediments. The trace elements considered were Cd, Cr, Cu, Ni, Pb and Zn, and leaching tests consisted of the application of reagents with contrasting characteristics and strengths in order to assess the information provided. An extraction with aqua regia permitted the estimation of the pseudo-total metal content in the sample. Mild extractants such as H2O, CaCl2 and NaNO3 showed low and similar leaching capacities. Acid (CH3COOH) and complexing (EDTA) agents were more effective in remobilising trace metals from soils and sediments. Cd and Zn showed similar extraction characteristics under both extractant solutions, whereas Cu and Pb were more sensitive to complexation, and Ni and Cr to acidification processes. Sequential chemical extractions provided additional information on the association of the trace elements with the different soil and sediment phases. Cd and Zn showed the highest mobility, Pb was associated to reducible solid phases, Cu and Ni to oxidisable phases, and Cr remained mostly in the residual fraction. The results obtained in this paper provided valuable information for choosing a leaching test, which is an instrument of environmental analysis for the estimation of trace metal mobility.     

Preconcentration technique for the determination of trace elements in natural water samples by ICP-AES

A procedure was developed for the determination of Cd, Cu, Zn, Co, Ni, Mn, Pb and Mo in water samples by inductively coupled plasma atomic emission spectrometry (ICP-AES) after preconcentration on a morpholine dithiocarbamate (mor-DTC) supported by bagasse (Saccharam aphisinaram). The sorbed elements were subsequently eluted with 4,M HNO₃ and the acid eluates were analysed by ICP–AES. The influence of various parameters such as pH, flow rate of sample, eluent concentration, volume of the sample and volume of eluent were investigated to enhance the sensitivity of the present method. A 20,mL disposable syringe served as preconcentration column. Under the optimal conditions Cd, Cu, Zn, Co, Ni, Mn, Pb and Mo in aqueous sample was concentrated about 100-fold. The sorption recoveries of elements were higher than 99.6%. The method is also applied for the analysis of natural and spiked water samples.     

Novel solid-phase extractor based on functionalization of multi-walled carbon nano tubes with 5-aminosalicylic acid for preconcentration of Pb(II) in water samples prior to determination by ICP-OES

New solid-phase extractor (MWCNTs-5-ASA) was synthesized via covalent immobilization of 5-aminsalicylic acid onto multi-walled carbon nanotubes (MWCNs). The success of the functionalization process was confirmed using Fourier transform infrared spectroscopy, scanning electron microscope, and surface coverage determination. Batch experiments were conducted as a function of pH to explore MWCNTs-5-ASA efficiency to extract several metal ions viz., Cr(III), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Pb(II). It was found that Pb(II) exhibits the highest extraction percentage with maximum adsorption capacity 32.75 mg g^?1. Its binding performance was well fitted with Langmuir sorption isotherm. On the other hand, the selective separation and preconcentration of trace Pb(II) under dynamic conditions prior to determination by inductively coupled plasma-optical emission spectrometry was investigated under different parameters. These included the rate of flow and volume of sample solution, in addition to the type of the eluate, its volume and concentration. The effect of a variety of foreign ions on the recovery percentage was also evaluated. Trace Pb(II) ions present in 500 mL aqueous solution adjusted to pH 4.0 were retained on 50 mg of MWCNTs-5-ASA and completely eluted using 4.0 mL of 2 M HNO₃. The limit of detection and the precision of the method were 0.25 ng mL^?1 and 2.8 %, respectively (N?=?5). This methodology has been applied for the determination of Pb(II) in water samples with good results.     

Chemical speciation in natural and brine sea waters

A combined approach consisting of monitoring and thermodynamic modeling was used in order to calculate the concentration of trace element species in water samples of a broad salinity range and to explain their chemical behaviour. The study was performed on water samples (fresh, marine, hyper-saline) taken from the area of Burgas Bay, Bulgaria. The ion association model based on Debye-Hückel theory using the sst2008.dat database and the ion interaction model based on Pitzer theory using a new pit2010.dat database were compared and combined for the purposes of this study. The new pit2010.dat database combines the sst2008.dat database and the pitzer.dat database of the PHREEQCI computer program as well as the thermodynamic data for the elements Fe, Mn, Cu, Zn, Cd and Pb and their Pitzer ion interaction parameters. The results showed that: (1) the predominant species in fresh waters were free ions of Mn(2+) (73.6%), Zn(2+) (58.0%) and Cd(2+) ions (78.3%) as well as carbonate species CuCO?? (81.8%), PbCO?? (77.2%) and hydroxy species Fe(OH) ??(55.2%) and Fe(OH)+?(35.6%); (2) an increase in chloride species MeCl2(n)-(n)(n = 1-4, Me = Mn, Zn, Cu, Pb and Cd) and of the hydroxy species Fe(OH)?? for Fe was calculated for sea and hyper-saline water.     

Speciation of Trace Metals in Coastal Sediments of El-Mex Bay South Mediterranean Sea–West of Alexandria (Egypt)

Sediments of El-Mex Bay estuary on the southern Mediterranean Sea have been analyzed for trace metals after sediment fractionation by sequential leaching. A sequential extraction procedure was applied to identify forms of Mn, Cu, Cd, Cr, Zn and Fe. The five steps of the sequential extraction procedure partitioned metals into: CH₃COONH₄ extractable (F1); NaOAC carbonate extractable (F2); NH₂OH.HCl/CH₃COOH reducible extractable (F3); H₂O₂–HNO₃ organic extractable (F4) and NHO₃/HClO₄/HF acid soluble residue (F5). Extracted concentrations of trace metals analyzed after all five steps, were found to be (μg/g) for Mn: 1930.2, Cu: 165.3, Cd: 60.9, Cr: 386.3, Zn: 2351.3 and Fe: 10895. Most of elements were found in reducible fraction except Fe found in acid soluble residue, characterizing stable compounds in sediments. Labile (non-residual) fractions of trace elements (sum of the first four fractions) were analyzed because they are more bioavailable than the residual amount. Correlation analysis was used to understand and visualize the associations between the labile fractions of trace metals and certain forms, since Fe-and Mn-oxides play an important role in trace metals sorption within aquatic systems, especially within El-Mex Bay sediments that characterized by varying metal bioavailability.     

Atmospheric deposition of major ions and trace metals near an industrial area,Jordan

Al, Cd, Cr, Cu, Fe, Mn, Pb, Zn, NH4+, Mg2+, Ca2+, Na+, K+, Cl-, NO3- and SO4(2-), along with pH were determined in wet and dry deposition samples collected at Al-Hashimya, Jordan. Mean trace metal concentrations were similar or less than those reported for other urban regions worldwide, while concentrations of Ca2+ and SO4(2-) were the highest. The high Ca2+ concentrations were attributed to the calcareous nature of the local soil and to the influence of the Saharan dust, while the high concentrations of SO4(2-) were attributed to the influence of anthropogenic sources and Saharan dust soil. Except for SO4(2-), NO3-, and Ca2+, dry deposition fluxes of measured metals and ions were higher than their corresponding wet deposition fluxes. The high annual average pH values recorded for wet and dry deposition samples were attributed to the neutralization of acidity by alkaline species. Cd, Cr, Cu, Pb, Zn, NO3- and SO4(2-) were enriched in wet and dry deposition samples relative to crustal material, and a significant anthropogenic contribution to these elements and ions is tentatively suggested. Finally, the possible sources and the main factors affecting the concentrations of the measured species are discussed.     

Preconcentration of metal ions through chelation on a synthesized resin containing O, O donor atoms for quantitative analysis of environmental and biological samples

Nascent Amberlite XAD-4 has been used as the polymeric support for the synthesis of a stable extractor of metal ions, by incorporating phthalic acid through azo bridging. Elemental analyses and infra-red spectral and thermal studies were carried out for its characterization. The water regain value and hydrogen ion capacity were found to be 12.50 and 5.75 mmol g^?1, respectively. The optimum pH range for the maximum sorption of Ni(II), Mn(II), Cu(II), Zn(II), Cd(II), Cr(III), and Co(II) was observed at pH 5.5–8.0 with the corresponding half-loading time (t _1/2) of 9, 5, 9, 9, 3, 9, and 5 min, respectively. The preconcentration factor for Ni(II), Mn(II), Cu(II), Zn(II), Cd(II), Cr(III), and Co(II) are 190, 190, 190, 180, 180, 160, and 160, with the corresponding limit of preconcentration in the range of 5.25–6.25 μg L^?1. The detection limits, for flame atomic absorption spectrophotometry, were found to be 0.62, 0.60, 0.65, 0.75, 0.72, 0.84, and 0.85 μg L^?1, respectively. Method has been successfully applied to the analysis of water samples, multivitamin formulations, infant food substitutes, hydrogenated oil, and fishes.     

Goose barnacle Pollicipes pollicipes as biomonitor of metal contamination in the northwest coast of Portugal

The main objective of this work was to assess the potential use of goose barnacle Pollicipes pollicipes as biomonitor of metal contamination in northwest (NW) coast of Portugal. The concentrations of Cd, Cr, Cu, Fe, Mn, Ni and Zn were determined in coastal seawaters and tissues of P. pollicipes, which allowed establishing correlations between metals in coastal seawaters and P. pollicipes and calculating metal bioaccumulation factors (BAFs). The results of this study showed that P. pollicipes soft tissues can be used for monitoring metal contamination in these coastal seawaters: (1) there were significant correlations (p??0.05); (2) soft tissues were sensitive to spatial variations of metal bioavailabilities and their concentrations ranged 0.70-2.22?mg?Cd?kg(-1), 0.49-1.40?mg?Cr?kg(-1), 1.37-2.07?mg?Ni?kg(-1), 2.4-3.3?mg?Cu?kg(-1), 5-59?mg?Mn?kg(-1), 134-578?mg?Fe?kg(-1)and 728-1,854?mg?Zn?kg(-1); (3) mean logarithmic bioaccumulation factors (log BAF) of Fe, Cd and Zn were higher, 5.57, 5.47 and 4.41, respectively, than mean log BAFs of Cr, Mn, Cu and Ni, 4.18, 4.14, 3.98 and 3.51, respectively. In contrary, P. pollicipes shell plates were not considered ideal material to monitor metal bioavailabilities in these coastal seawaters. Regarding the very high concentrations of Zn obtained in the coastal seawaters and P. pollicipes soft tissues, the NW coast of Portugal should be classified as "Class III/IV - Remarkably/Highly Polluted".     

Levels and speciation of heavy metals in soils of industrial Southern Nigeria

A knowledge of the total content of trace metals is not enoughto fully assess the environmental impact of polluted soils. Forthis reason, the determination of metal species in solution isimportant to evaluate their behaviour in the environment andtheir mobilization capacity. Sequential extraction procedure wasused to speciate five heavy metals (Cd, Pb, Cu, Ni and Zn) fromfour contaminated soils of Southern Nigeria into sixoperationally defined geochemical species: water soluble,enchangeable, carbonates, Fe-Mn oxide, organic and residual.Metal recoveries were within ± 10% of the independentlydetermined total Cd, Pb, Cu, Ni and Zn concentrations. The highest amount of Cd (avg. 30%) in the nonresidual fractionswas found in the exchangeable fraction, while Cu and Zn weresignificantly associated with the organic fraction. Thecarbonate fraction contained on average 14, 18.6, 12.6, 13 and11% and the residual fraction contained on average 47, 18, 33,50 and 25% of Cd, Pb, Cu, Ni and Zn respectively. Assuming thatmobility and bioavailability of these metals are related to thesolubility of the geochemical form of the metals, and that theydecrease in the order of extraction sequence, the apparentmobility and potential bioavailability for these five metals inthe soil were: Pb > Zn > Cu > Ni > Cd. The mobility indexes ofcopper and nickel correlated positively and significantly withthe total content of metals, while mobility indexes of cadmiumand zinc correlated negatively and significantly with the totalcontent of metals.     

Determination of traces of copper and zinc in honeys by the solid phase extraction pre-concentration followed by the flame atomic absorption spectrometry detection

A simple and fast solid phase extraction procedure was developed to pre-concentrate traces of Cu and Zn prior to their determination in honey samples by flame atomic absorption spectrometry. The sample preparation included dissolution of honey samples and the passage (at 20 ml/min) of resulting 10 % m/v solutions (100 ml) through Dowex 50W?×?8-400 resin beds in order to quantitatively retain Cu and Zn and separate them from the glucose and fructose matrix. Enriched Cu and Zn traces were recovered with 5.0 ml of a 3.0 mol/l HCl solution and quantified by flame atomic absorption spectrometry. The procedure proposed was used to analyze sixty nine commercially available and freshly ripened honey samples coming from the Lower Silesia region (Poland). It enabled to measure Cu and Zn within the range of 0.01–1.42 and 0.03–15.38 μg/g, respectively, with precision better than 4 %. Accuracy, assessed on the basis of the recovery test and the comparison of results with those obtained using wet digestion and inductively coupled plasma optical emission spectrometry, was ranged from ?4 % to +6 %. Detection limits of Cu and Zn achieved with this method were 5 and 7 ng/g, respectively.     

Study of Geochemical Association of Some Trace Metals in the Sediments of Chilika Lake: A Multivariate Statistical Approach

In order to establish the natural processes and geochemical factors responsible for enrichment of trace metal ions (Cu, Co, Ni, Zn and Cr) with respect to textural parameters (sand, silt and clay weight percentages) along with depth, multivariate statistical approach has been carried out for sediments in different water zones of Chilika lake, the largest brackish water lagoon in Asia. The rotated varimax factor results reveal that Cobalt enrichment is controlled by both textural parameters as well as adsorption mechanism. In fresh and saline water region, textural parameters and in mixed water, adsorption phenomenon predominates. Zn in fresh water is related to clay, whereas it is in adsorbed state in mixed water. Cu in fresh water sediments is in absorbed state and in mixed water it is related to depth and Co concentration. Cr does not show any specific association in fresh water, but in both mixed and saline water it is associated with clay minerals. Although both textural parameters and adsorption mechanism play an important role for the enrichment of trace metal ions in these lagoonal sediments, their relative importance varies with specific metal ions as well as the water quality. Sequential extraction technique was used to characterize the various forms of metals in the < 63μ size sediments of Chilika lake. The concentrations determined indicated selective accumulation of the various metals in the different phases with spatial variability in different water zones. Slightly higher availability of Co and Zn near Balugaon township in exchangeable phase may be related to anthropogenic activities. Among the non-lithogenous (NL) phases, reducible phase associated with higher concentration of Ni, Cu and Cr. Organic bound Zn and Co contributed highest percentages among NL fractions. Residual fraction contributed more than 50% in most of the cases, reflected the predominance of physical weathering, high erosion rate along the drainage basin.     

Determination of metal-humic complexes, free metal ions and total concentrations in natural waters

A comparison of two systems for the quantitation of metal-humic complexes and free metal ions, consisting of the separation by coupled ion exchange columns followed by detection by inductively coupled plasma mass spectrometry or cold vapour atomic fluorescence spectrometry, is presented. The systems evaluated comprised the serially coupled anion and cation exchangers, Sephadex A-25/Chelex 100 and Dowex 1X8/Chelamine Metalfix. Separation and preconcentration of the species studied were accomplished with both systems, elution being carried out using 2 M HNO3. Total concentrations, metal-humic complex fractions and free metal ion fractions of Al, Ba, Cd, Co, Cu, Fe, Hg, Mn, Pb, Sr, U and Zn in nine natural waters were determined. Statistical evaluation of the data from the two cation exchange materials, including results for additional elements, showed better precision (for Al, Ba, Cr, Cu and Mo) and higher recoveries (Al, Ba, Cd, Fe, Sr and Zn) for Chelex 100 than Chelamine Metalfix for free metal ions. On the other hand, Chelamine Metalfix recovered a significantly greater amount of Ni. The amounts of metal-humic complexes were compared with modelled distributions of these species, and one advantage of the preferred Sephadex A-25/Chelex 100 system is that the elements studied are all correctly classified with respect to their binding strengths to humic substances, which is not the case with the Dowex 1X8/Chelamine Metalfix pair. With the preferred system, metal-humic complexes can be reliably determined, as indicated by the results of equilibrium speciation modelling. However, comparison with the total concentrations showed statistically significant, non-quantitative recoveries of Al, Cu, Hg, Mn, U and Zn from some samples. Thus a combination of speciation and total concentration measurements is required to obtain a complete representation of the distribution of trace elements in natural waters.     

Chthamalus montagui as biomonitor of metal contamination in the northwest coast of Portugal

The concentrations of seven metals (Cd, Cr, Cu, Fe, Mn, Ni and Zn) were determined in coastal seawaters and soft and hard tissues of the barnacle Chthamalus montagui from the northwest coast of Portugal to assess the potential use of C. montagui as biomonitor of metal contamination. The results of this study showed that C. montagui soft tissues can be used for monitoring metal bioavailabilities in these coastal seawaters: (1) there were significant correlations (p?相似文献   

A preconcentration procedure for the determination of cadmium in biological material after on-line cloud point extraction

In this paper, a method involving on-line preconcentration with cloud point extraction for the determination of cadmium in biological samples is presented. The procedure is based on the sorption of micelles containing Cd(II) ions and the reagent 4-(5'-bromo-2'-thiazolylazo)orcinol (Br-TAO) in a minicolumn packed with polyester. The surfactant Triton X-114 was used in the formation of micelles. After sorption, the Cd(II) ions were desorbed from the minicolumn with acid eluent and determined by flame atomic absorption spectrometry. Parameters influencing the cloud point extraction were studied. The method showed a detection limit of 0.5 μg l(-1) and an enhancement factor of 27. The accuracy was tested by determination of cadmium in certified reference materials (spinach leaves 1570a and tomato leaves 1573a) from the National Institute of Standards and Technology.     

Fractionation and ecological risk of metals in urban river sediments in Zhongshan City, Pearl River Delta

Surface sediments collected from nine urban rivers located in Zhongshan City, Pearl River Delta, were analyzed for total concentration of metals with digestion and chemical fractionation adopting the modified European Community Bureau of Reference (BCR) sequential extraction procedure. The results showed that concentration and fractionation of metals varied significantly among the rivers. The total concentration of eight metals in most rivers did not exceed the China Environmental Quality Standard for Soil, Grade III. The potential ecological risk of metals to rivers were related to the land use patterns, in the order of manufacturing areas > residential areas > agriculture areas. The concentration of Pb in the reducible fraction was relatively high (60.0-84.3%). The dominant proportions of Cd, Zn and Cu were primary in the non-residual fraction (67.0%, 71.8% and 81.4% on average respectively), while the percentages of the residual fractions of Cr and Ni varied over a wide range (43-85% and 24-71% respectively). The approaches of the H?kanson ecological risk index and Secondary Phase Enrichment Factor were applied for ecological risk assessment and metal enrichment calculation. The results indicated Hg and Cd had posed high potential ecological risk to urban rivers in this region. Meanwhile, there was widespread pollution and high enrichment of Cu in river sediments in this region. Multiple regression analysis showed that five water quality parameters (pH, DO, COD(Mn), NH(4)(+)-N, TP) had little influence on the distribution of metal fractionation. This result revealed that the ecological risk of metals was not eliminated along with the improvement in water quality. Correlation studies showed that among the metals, Group A (Cd, As, Pb, Zn Hg, r = 0.730-0.924) and Group B (Cr, Cu, Ni, r = 0.815-0.948) were obtained, and the metal contaminations were from industrial activities rather than residential.