Influence of dissolved organic matter from corn straw on Zn andCusorption to Chinese loess

The interaction of Zn and Cu with dissolved organic matter (DOM) is a significant physicochemical process affecting their sorption as well as mobility in soil. The objective of this study was to examine the influence of DOM from corn straw on the sorption of Zn and Cu by loess through batch adsorption technique. The sorption isotherms of Zn and Cu could be well described by the Freundlich equation, and the partition distribution coefficient (k) in the presence of DOM was reduced by 86% for Zn and 58% for Cu, as compared to the control receiving no DOM, suggesting that DOM had a stronger inhibitory effect on Zn sorption than that of Cu. In addition, the sorption of metal increased with an increase in pH for loess, with maximum inhibition on metal sorption observed at pH > 7.6 for Zn and pH > 5.5 for Cu in the absence ofDOM but Cu sorption of DOM was suddenly decreased with an increase of pH at pH > 7.9 in the presence of DOM. At a DOM concentration of <200 mg L^?1, sorption of Zn and Cu was reduced by 46% for Zn and 32% for Cu with an increase in DOM concentration.     

Synthesis,structural characterization and antimicrobial activity of nickel(II) tetrathiocyanato dicuperate(I) complexes with some acyl hydrazones

Heterobimetallic complexes of the type Ni[Cu(SCN)₂]₂ · L (where L = acetophenone benzoylhydrazone, acetophenone isonicotinoyl hydrazone, acetophenone salicyloylhydrazone (ash), acetophenone anthraniloylhydrazone, p-hydroxy acetophenone benzoylhydrazone, p-hydroxy acetophenone isonicotinoyl hydrazone p-hydroxy acetophenone salicyloylhydrazone (phash), p-hydroxy acetophenone anthraniloyl hydrazone), were synthesized and characterized. The complexes are polymeric, insoluble in common organic solvents and are nonelectrolytes. Magnetic moments and electronic spectral studies suggest a spin-free octahedral geometry for the complexes. IR spectra show the bidentate nature of all the ligands bonding through >C=O and >C=N–groups. The SCN group acts as a bridge between two metal centers. X-ray powder diffraction parameters for Ni[Cu(SCN)₂]₂ · ash and Ni[Cu(SCN)₂]₂ · phash correspond to orthorhombic and tetrahedral crystal lattices, respectively, for these complexes. The complexes show a significant antifungal activity against Rizoctonia, Stemphylium and Aspergillus sp. and antibacterial activity against Clostridium and Pseudomonas sp. The metal complexes are more active than the ligands.     

Synthesis,structural elucidation,electro-chemical behaviour and fungitoxic activity of transition metal(II) mixed-ligand complexes with some Schiff bases

The Schiff bases, potassium salt of salicylidene-β-alanine [KHL], bis(benzylidene)ethylenediamine [SB¹] and thiophene-o-carboxaldene-p-toluidine [SB²], and mixed-ligand complexes with Mn(II), Co(II), Ni(II), Cu(II), Zn(II), and Cd(II) have been prepared. They were characterized by elemental analyses, magnetic susceptibility measurements, thermogravimetric analyses (t.g.a.), infrared spectra and electronic spectra. The mixed-ligand complexes were found to have the general composition [M(L)(SB)(H₂O)]. All the mixed-ligand complexes were found to have six-coordinated octahedral geometry. The fungitoxic activity of the ligands, metal salts, control (DMSO), bavistin, emcarb, and mixed-ligand complexes were screened against Aspergillus niger, Fusarium oxysporum and Aspergillus flavus. All the mixed-ligand complexes show higher fungitoxic activity as compared to the Schiff bases, metal nitrate and control (dimethyl sulphoxide, DMSO), and moderate fungitoxic activity as compared to the fungicides (bavistin and emcarb).     

Potential application of sludge produced from coal mine drainage treatment for removing Zn(II) in an aqueous phase

Various analyses of physico-chemical characteristics and batch tests were conducted with the sludge obtained from a full-scale electrolysis facility for treating coal mine drainage in order to find the applicability of sludge as a material for removing Zn(II) in an aqueous phase. The physico-chemical analysis results indicated that coal mine drainage sludge (CMDS) had a high specific surface area and also satisfied the standard of toxicity characteristic leaching procedure (TCLP) because the extracted concentrations of certain toxic elements such as Pb, Cu, As, Hg, Zn, and Ni were much less than their regulatory limits. The results of X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) showed that the CMDS mainly consists of goethite (70%) and calcite (30%) as a weight basis. However, the zeta potential analysis represented that the CMDS had a lower isoelectric point of pH (pH(IEP)) than that of goethite or calcite. This might have been caused by the complexation of negatively charged anions, especially sulfate, which usually exists with a high concentration in coal mine drainage. The results of Fourier transform infrared (FT-IR) spectrometry analysis revealed that Zn(II) was dominantly removed as a form of precipitation by calcite, such as smithsonite [ZnCO?] or hydrozincite [Zn?(CO?)?(OH)?]. Recycling sludge, originally a waste material, for the removal process of Zn(II), as well as other heavy metals, could be beneficial due to its high and speedy removal capability and low economic costs.     

Toxic effect of transition metal complexes on Salmonella typhi,Escherichia coli and Serratia marcescens

The present article describes the synthesis, structural features and toxicological studies of the complexes of the type [M(L)(dipy-amine)(H₂O)] or [M(L)(bendan)(H₂O)] where M?=?Mn(II), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II), H₂L?=?salicylidene-o-aminothiophenol, dipy-amine?=di(2-pyridyal)amine, or bendan?=?bis(benzylidene)1,8-diaminonaphthalene. The complexes have been characterized on the basis of elemental analyses, electronic spectra, magnetic measurement and thermogravimetric analyses. The nature of the bonding has been discussed on the basis of infrared spectral data. A thermal study of the complexes has been carried out to ascertain their thermal stability. Magnetic susceptibility measurements and electronic spectral data suggest a six-coordinated octahedral structure for these complexes. The complexes of Mn(II), Co(II), Ni(II), Cu(II) are paramagnetic, while Zn(II) and Cd(II) are diamagnetic in nature. The toxic effects of the investigated complexes were tested against three Gram-negative bacteria, Salmonella typhi, Escherichia coli and Serratia marcescens by the “Disc Diffusion Method”. It is observed that the complexes show higher toxic effects as compared to the ligands, metal salts and control (DMSO), but moderate toxic effects as compared to the standard drug (tetracycline) and the results are discussed.     

环境中金属生物有效性的预测模型——生物配体模型研究进展

生物配体模型(BLM)是一种用于预测环境中金属生物毒性的机理性模型.模型理论起源于自由离子活度模型(FIAM)和鱼鳃络合模型(GSIM),考虑了自由金属离子的活度以及自然环境存在的其他离子(如Ca2+、Na+、Mg2+、H+)、非生物配体(如可溶性有机质、氯化物、碳酸盐、硫酸盐)和生物配体的竞争.目前,在水生生态系统中,基于鱼鳃络合模型的框架基础,通过生物化学实验手段并结合数学方法,建立了预测铜、锌、银、镍对Rainbowtrout(虹鳟鱼)、Fatheadminnow(黑头呆鱼)和Daphniamagna(水蚤)的急、慢性毒性的BLM版本,并积极探索其在陆地生态系统中的应用.虽然生物配体模型在实验室模拟条件下取得了较为满意的结果,但其中包含着一些假设,在实际应用中还具有一定的局限性,尤其是陆地生态系统生物配体模型的发展还需要做许多研究工作.本文主要论述了生物配体模型的理论基础、实现手段和应用情况,讨论了生物配体模型的优势和局限性并对其未来研究方向进行了展望.     

In situ mapping of growth lines in the calcitic prismatic layers of mollusc shells using X-ray absorption near-edge structure (XANES) spectroscopy at the sulphur K-edge

The microstructure and composition, including chemical speciation of sulphur (S), of two mollusc shells were investigated using a combination of scanning electron microscopy, X-ray absorption near-edge structure spectroscopy (XANES) and electron probe microanalysis (EPMA). The shell of Pinna is composed of monocrystalline, and Pinctada, of polycrystalline, calcite prisms separated by organic-rich walls. Sulphur speciation information from XANES spectra using a scanning X-ray microscope showed that the protein S content of the interprismatic walls is higher than the SO₄ content, whereas the reverse is true for the intraprismatic structures. High-spatial-resolution XANES maps for the different S species across adjacent calcite prisms confirm their distinctive distributions in the molluscan shells and illustrate the presence of narrow, submicron transverse growth features. On a larger scale, a series of wider growth zones, incorporating the submicron zones, are aligned parallel to each other and cross-cut many calcite prisms. EPMA element maps for magnesium (Mg) and S demonstrate that these growth increments are compositionally zoned, comprising alternating layers of high mineral (Mg-rich) and high organic (S-rich) components. Additionally, these maps confirm that the organic interprismatic walls have lower Mg and higher S than the intraprismatic structures.     

High zinc removal from water and soil using struvite-supported diatomite obtained by nitrogen and phosphate recovery from wastewater

Zinc is known as an essential element of human life. However, excessive zinc discharge into water and soil causes water pollution, leading to serious health issues such as septicemia, meningitis and iron-deficiency anemia. Here, a novel material made of struvite-supported diatomite was obtained from eutrophic water treated by mesoporous MgO-modified diatomite. This material was applied for zinc remediation in aqueous solutions and contaminated soils to test the reuse of P-containing products. Struvite-supported diatomite was characterized by field emission scanning electron microscopy and X-ray diffraction. Results show that the maximum removal efficiency of Zn(II) from wastewater streams reached 90.54% at an initial pH of 5 and struvite-supported diatomite dosage of 0.3 g/L. Moreover, the X-ray diffraction patterns of precipitates after Zn(II) sorption show that the combination between zinc and the phosphate group played a key role for zinc removal in solution. For Zn-contaminated soils amended with 10% struvite-supported diatomite, available Zn decreased by 65.38% and acid soluble Zn decreased by 56.9% after 56 days.     

Spectroscopic studies and biological evaluation of some transition metal complexes of a novel Schiff base ligands derived from 5-arylazo-salicyladehyde and o-amino phenol

Synthesis and characterization of Cu(II), Ni(II), and Zn(II) Schiff bases complexes resulted from the condensation of salicylaldehyde derivatives with o-amino phenol were discussed using elemental analysis (carbon, hydrogen, and nitrogen), molar conductance, magnetic measurements, mass spectra, and electronic spectra. The essential bands of infrared, ¹HNMR, and UV-Vis spectra as well as thermogravimetric analysis corresponding to the active groups within the three ligands and their complexes were interpreted. The dehydration and decomposition processes of the [Cu(H₂L₁)(H₂O)](OAc)₂, [Ni(H₂L₁)(H₂O)]SO₄ · H₂O, [Zn(H₂L₁)(H₂O)]SO₄ · H₂O, [Cu(H₂L₂)(H₂O)](OAc)₂, [Ni(H₂L₂)(H₂O)]SO₄ · H₂O, [Zn(H₂L₂)(H₂O)]SO₄ · 2H₂O, [Cu(H₂L₃)(H₂O)](OAc)₂ · H₂O, [Ni(H₂L₃)(H₂O)]SO₄ · 2H₂O, [Zn(H₂L₃)(H₂O)]SO₄ complexes were studied thermodynamically using the integral method applying the Coats–Redfern and Horowitz–Metzger equations and the thermodynamic parameters were calculated. It was found from the elemental analysis and the thermal studies, that the ligand behaves as tridentate ligand forming chelates with 1 : 1 (metal : ligand) stoichiometrically. The molar conductance measurements of the complexes in dimethyl sulfoxide solvent indicate that the complexes have an electrolytic nature. The biological activities of the three ligands in comparison with metal(II) complexes were studied against different Gram positive and Gram negative bacteria.     

Spatio-temporal variations of fluorescence properties of dissolved organic matter along the River Têt (Pyrénées-Orientales,France)

Fluorescence excitation-emission matrices showed the spectral signature of dissolved organic matter (DOM) downstream in the River Têt at all seasons corresponding to humic substances with maximum fluorescence emission λem=420–460 nm for excitations of λex=340–360 nm and the occasional presence of tryptophan, tracer of anthropogenic pressure, spectroscopically identified by λex/λem=310/350 nm. A factorial discriminant analysis, performed using the parameters selected (λex/λem pairs of wavelength), succeeded in a better discrimination of seasons than stations, and clearly showed the presence of two fluorophores. Fluorophore 1, with two absorption bands: λex=260–320 nm and 330–390 nm for λem=440–500 nm, and Fluorophore 2, with one absorption band: λex=300–360 nm for λem=410 nm, which are attributed to humic acid (HA) and fulvic acid (FA), respectively. Variations of DOM relative contents downstream in the River Têt, according to seasons and stations, showed high amounts of DOM (pedogenic character) along the river in the humid period, with the highest value obtained in the mountain section. In contrast, in summer, the DOM contents were low (aquagenic character). Moreover, DOM presents a relatively constant composition with a percentage of FA ranging from 40% at the mountain station to 48% at the mouth river, whatever the season.     

Effects of three low-molecular-weight organic acids (LMWOAs) and pH on the mobilization of arsenic and heavy metals (Cu, Pb, and Zn) from mine tailings

Natural organic acids may play an important role in influencing the mobility of toxic contaminants in the environment. The mobilization of arsenic (As) and heavy metals from an oxidized Pb–Zn mine tailings sample in the presence of three low-molecular-weight organic acids, aspartic acid, cysteine, and succinic acid, was investigated at a mass ratio of 10 mg organic additive/g mine tailings in this study. The effect of pH was also evaluated. The mine tailings sample, containing elevated levels of As (2,180 mg/kg), copper (Cu, 1,100 mg/kg), lead (Pb, 12,860 mg/kg), and zinc (Zn, 5,075 mg/kg), was collected from Bathurst, New Brunswick, Canada. It was found that the organic additives inhibited As and heavy metal mobilization under acidic conditions (at pH 3 or 5), but enhanced it under neutral to alkaline conditions (at pH above 7) through forming aqueous organic complexes. At pH 11, As, Cu, Pb, and Zn were mobilized mostly by the organic additives, 45, 46, 1,660, and 128 mg/kg by aspartic acid, 31, 28, 1,040, and 112 mg/kg by succinic acid, and 53, 38, 2,020, and 150 mg/kg by cysteine, respectively, whereas those by distilled water were 6, 16, 260, and 52 mg/kg, respectively. It was also found that the mobilization of As and the heavy metals was closely correlated, and both were closely correlated to Fe mobilization. Arsenic mobilization by the three LMWOAs was found to be consistent with the order of the stability of Fe–, Cu–, Pb–, and Zn–organic ligand complexes. The organic acids might be used potentially in the natural attenuation and remediation of As and heavy metal–contaminated sites.     

Effects of dissolved organic matter on the desorption of Cd in freeze–thaw treated Cd-contaminated soils

Lab-scale experiments were conducted to investigate the effects of dissolved organic matter (DOM) on the desorption of Cd in freeze–thaw treated Cd-contaminated soils. The results indicated that DOM significantly facilitated the desorption of Cd from freeze–thaw treated soils when comparing with that of non-frozen soils. Effects of DOM on the Cd desorption were highly dependent on the soil type and contamination concentration. The maximum desorption ratios of Cd by DOM generated from straw and sludge were 15.6% and 13.65%, respectively, in brown soils, and the maximum desorption ratios reached 14.7% and 9.3%, respectively, when using black soils through the same treatment. The higher the Cd contamination concentration in soils, the higher the ratio of Cd desorption by DOM. This was because of the integrated effects of the soil properties changed by the freeze–thaw treatment and the species transformation of Cd. The characteristics of DOM, such as its concentration and properties, had shown obvious impacts on the Cd desorption by DOM. The desorption was promoted with the increased DOM concentration and the hydrophilic fraction, and lowered pH and the low-molecular-weight of DOM.     

Potential application of sludge produced from coal mine drainage treatment for removing Zn(II) in an aqueous phase

Various analyses of physico-chemical characteristics and batch tests were conducted with the sludge obtained from a full-scale electrolysis facility for treating coal mine drainage in order to find the applicability of sludge as a material for removing Zn(II) in an aqueous phase. The physico-chemical analysis results indicated that coal mine drainage sludge (CMDS) had a high specific surface area and also satisfied the standard of toxicity characteristic leaching procedure (TCLP) because the extracted concentrations of certain toxic elements such as Pb, Cu, As, Hg, Zn, and Ni were much less than their regulatory limits. The results of X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) showed that the CMDS mainly consists of goethite (70%) and calcite (30%) as a weight basis. However, the zeta potential analysis represented that the CMDS had a lower isoelectric point of pH (pH_IEP) than that of goethite or calcite. This might have been caused by the complexation of negatively charged anions, especially sulfate, which usually exists with a high concentration in coal mine drainage. The results of Fourier transform infrared (FT-IR) spectrometry analysis revealed that Zn(II) was dominantly removed as a form of precipitation by calcite, such as smithsonite [ZnCO₃] or hydrozincite [Zn₅(CO₃)₂(OH)₆]. Recycling sludge, originally a waste material, for the removal process of Zn(II), as well as other heavy metals, could be beneficial due to its high and speedy removal capability and low economic costs.     

Metallsorption an Illit und Metallfreisetzung unter Einwirken der Aminosäuren Glycin und Histidin

The heavy metal ions Zn(II), Pb(II), Cr(III) and Hg(II) were examined in regard of their adsorption behaviour towards Kaolin W from Lohrheim (51% illite, 31% kaolinite and 18% quarz). By means of the Langmuir and Freundlich models the determined adsorption isothermes could be linearized. The ability of glycine and histidine solutions to release heavy metal ions, pre-adsorbed on Kaolin W (36,1–2300 mg kg^?1 Zn, Pb, Cr and Hg), was specified. It was found a low influence of glycine, but an evident influence of histidine to the metal release, expecially of Pb and Cr, depending on the metalcoating, metal-amino acid-ratio, experimental pH and testing period. The highest remobilisation fraction, up to 98%, could be found in the case of Zn. This elucidates an enhancement of the zinc release compared with the blank solution, without containing amino acids, to a factor of maximal 9,3. As far as Pb and Cr were concerned the histidine extraction exeeded the remobilisation in the blank solution by a maximum of 50,8 or 40. As Hg develops strong covalent bondings to illite by OH-bridges, the release of Hg was not affected by the amino acids.     

Rapid degradation of carbon tetrachloride by commercial micro-scale zinc powder assisted by citric acid

We developed an effective method for degradation of carbon tetrachloride (CT) in contaminated water. Zinc metal as a reducing agent for CT in aqueous solutions has been previously studied in some detail, but the rapid corrosion of zinc surface usually reduces its efficiency in removing CT. We assumed that citric acid could enhance the degradation of CT by zinc powder due to the elimination of a passivation layer of Zn(II) (hydr)oxides on the surface of zinc powder through chelating of organic ligands with Zn(II) produced from the reaction and keeping the exposure of active sites to targets. Here the influence of citric acid on the decomposing of CT by commercial micro-scale zinc powder was investigated in a pH range of 3.5–7.5 at 25°C in batch experiments. Reaction mixtures were analysed by gas chromatography/headspace analysis, and Cl⁻ concentration was determined by turbidimetry. The results demonstrate that the degradation of CT by zinc metal alone is very weak, but the addition of citric acid can assist zinc powder to decompose CT more completely and rapidly at all pHs. Degradation of CT took place mainly in the first 10 min of reaction, coupled with 75–95% of CT removal. Maximum dechlorination percentage (82.4%) of CT was obtained at pH 5.5. In that case, chloroform and dichloromethane, as main intermediates, were found at low levels during the whole reaction, suggesting that CT may be sequentially and multiply degraded so quickly that methane is yielded before the intermediates can be desorbed and released to aqueous solution. When compared with the current methods of nano-scale zinc and bimetallic systems, the application of commercial micro-scale zinc particles assisted by organic ligands is of environmental significance since it allows decontamination of aqueous chlorinated organic compounds at low cost and with high efficiency.     

Biosorption of cadmium and nickel ions using marine macrophyte,Cymodocea nodosa

ABSTRACT

Seagrass (Cymodocea nodosa) ability to remove cadmium and nickel ions from single metal solutions was investigated in the present study. Metal ions were measured in the solution using an atomic absorption spectrophotometer. Various operational parameters (initial pH, biomass dose, metal ion concentration, and contact time) were tested and found to affect the uptake capacity of Cd (II) and Ni (II). More than 70% of biosorption capacity occurred in the first few minutes for both metal ions. The pseudo-second-order kinetic model and the Langmuir model were found to best fit the experimental data of Cd (II) and Ni (II) biosorption. The maximum uptake capacity (q_max) was 11.6 and 16.7?mg.g^?1 for Cd (II) and Ni (II), respectively. The biosorbent was characterised using Fourier transform infrared spectrometry (FTIR), scanning electron microscope (SEM), and energy-dispersive X-ray spectroscopy (EDX). The infrared spectrum demonstrated that hydroxyl, carboxyl, and phenolic functional groups are the major binding sites for Cd (II) and Ni (II) metals. The ion exchange mechanism plays an important role during biosorption process as shown in EDX analysis. Our results conclude that marine macrophyte C. nodosa can be used as a low-cost biosorbent for the removal of Cd (II) and Ni (II) in wastewater.     

Lead(II) and cadmium(II) removal from aqueous solution using processed walnut shell: kinetic and equilibrium study

The biosorption potential of processed walnut shell for Pb(II) and Cd(II) ions from aqueous solutions was explored. The effects of pH, contact time, initial ion concentration, and amount of dried adsorbent were studied in batch experiments. The maximum adsorption was achieved within the pH range 4.0–6.0. The equilibrium data were well fitted by the Langmuir isotherm model. The maximum monolayer adsorption capacities were found to be 32?g?kg^?1 and 11.6?g?kg^?1 for Pb(II) and Cd(II) ions, respectively. Kinetic data were best described by the pseudo-second-order model. The structural features of the adsorbent were characterized by Fourier transform infrared spectroscopy, which confirmed the involvement of hydroxyl (–OH), carboxyl (–COO^–), and carbonyl (C=O) groups in metal sorption. This readily available adsorbent is efficient in the uptake of Pb(II) and Cd(II) ions from an aqueous solution and could be used for the treatment of wastewater streams bearing these metal ions.     

Quantitative characterization of Cu binding potential of dissolved organic matter （DOM） in sediment from Taihu Lake using multiple techniques

Dissolved organic matter （DOM） plays an important role in heavy metal speciation and distribution in the aquatic environment especially for eutrophic lakes which have higher DOM concentration. Taihu Lake is the third largest freshwater and a high eutrophic lake in the downstream of the Yangtze River, China. In the lake, frequent breakout of algae blooms greatly increased the concentration of different organic matters in the lake sediment. In this study, sediment samples were collected from various part of Taihu Lake to explore the spatial difference in the binding potential of DOM with Cu. The titration experiment was adopted to quantitatively characterize the interaction between Cu（II） and DOM extracted from Taihu Lake sediments using ion selective electrode （ISE） and fluorescence quenching technology. The ISE results showed that the exogenous DOM had higher binding ability than endogenous DOM, and DOM derived from aquatic macrophytes had a higher binding ability than that derived from algae. The fluorescence quenching results indicated that humic substances played a key role in the complexation between DOM and Cu（II） in the lake. However, because of the frequent breakout of algae blooms, protein-like matters are also main component like hnmic matters in Taihu Lake. Therefore, the metals bound by protein-like substances should be caused concern as protein-like substances in DOM were unstable and they will release bound metal when decomposed.     

Amelioration of free copper by hydrothermal vent microbes as a response to high copper concentrations

We examined the effect of increased copper concentrations (0–10 μM) on hydrothermal vent micro- organisms and the production of copper (Cu)-binding ligands as a response. Hydrothermal vent microbes originated from diffuse fluids at the Lilliput mussel field and the Irina II site in the Logatchev hydrothermal vent field, both on the Mid-Atlantic Ridge. Parallel studies were also conducted with amino acids supplemented to the incubations in order to verify whether dissolved amino acids, present in hydrothermal fluids, can buffer the bioavailable copper and reduce the active production of Cu-binding ligands. In all incubations, ligand concentrations increased with rising copper concentrations, but microbial cell numbers remained constant. This study shows that microbes were able to cope with as much as 10 μM dissolved copper by buffering the free copper concentration. The presence of amino acids had no significant influence on the active ligand production. Our results imply that mediation of chemical speciation by vent microbes may have an important impact on hydrothermal trace metal fluxes into the ocean.     

Watershed land use as a determinant of metal concentrations in freshwater systems

Concentrations of Fe, Mn, Cu, dissolved organic matter (DOM), and pH were synthesized from 30 publications to determine the factors regulating concentrations and behavior of metals in freshwater systems. Results from the review suggest that contrasting watershed land use can directly (erosion and runoff) and indirectly (in-lake processes including metal–DOM–pH interactions) affect the metal concentrations in freshwater systems. Among the watershed land uses considered here, concentrations of Fe, Mn, and Cu were observed in the following order: arctic lakes < forested < agricultural < urbanized < mined. A drastic difference in mean metal concentrations has been observed when undisturbed or low impact watersheds (arctic and forested) were changed by agricultural, urban, and mining developments. Relationships between metal concentrations and pH revealed that metals precipitate at high pH (pH > 5). Additionally, at pH < 5, metal concentrations were significantly correlated with DOM due to metal–DOM complexation. High ratios of metal: DOM occur only at low DOM concentrations. Collectively, two general conclusions can be drawn from this review. First, lakes, rivers, and streams with urbanized watersheds are the most susceptible to increased concentrations of metals. Secondly, these results also suggest that regardless of high or low DOM in the water column, pH would affect metal concentrations in freshwater systems. Nonetheless, free metal ions would be higher in freshwater systems with acidic water and low DOM.