Metals In Natural Waters Research Articles

Toxicity of Heavy Metals to the Marine DiatomDitylum Brightwellii(West) Grunow: Correlation between Toxicity and Metal Speciation

The possibility of dissolved organic compounds acting as complexing or chelating agents in natural waters has received considerable attention in the last two to three decades. Stumm & Morgan (1970) have expressed doubts about the existence of humicmetal ion complexes in natural waters. Strickland (1972) has also stated that although the addition of chelating agents to sea water often improved the growth of phytoplankton, there was little evidence that the function of dissolved organic matter in oceans and lakes was to complex metals so as to increase or decrease their availability to phytoplankton. Strickland argued that even if all dissolved organic carbon were present as a compound of strong complexing ability it would not be able to compete for most metals with inorganic ligands such as chloride, sulphate and hydroxide. However, there is an increasing amount of data indicating that metals in natural waters may exist in chelated forms with dissolved organic matter (see, for example, Davey, Morgan & Erickson, 1973; Chau & Lum-Shue-Chan, 1974).

The significance of natural environmental factors in the distribution of copper in potable waters of Sri Lanka

A survey carried out on the copper content in drinking water wells in Sri Lanka shows that the island could be divided into four main zones based on the copper content. Among the natural factors that are of relevance in the distribution are the geologic, topographic, climatic, paedologic and structural factors. It is shown that the geochemical status of an element in a particular area must necessarily influence its uptake through food and drinking water. The understanding of the controls on the concentration of metals in natural waters and soil solutions apart from helping in the study of a real incidence of certain diseases of man and animals, greatly facilitates the treatment of water for domestic and industrial use.

Comparison of preconcentration procedures for trace metals in natural waters

The relative merits of eight procedures for preconcentrations of trace metal ions from natural water samples and synthetic solutions are evaluated. Spikes (100 μg l −1 ) of Mn, Co, Zn, Eu, Cs and Ba and the corresponding radioactive tracers were added to batches of drinking water, estuarine water, sea water, ground water, twice-distilled water and ahumic material solution. After equilibration for 2–5 months, the following techniques were applied: passage through columns of Dowex Al chelating resin and ofsilylated silica gel, filtration through laminate membrane filters and chelating diethylenetriamine cellulose filters, precipitation with sodium diethyldithiocarbamate and l-(2-pyridylazo)-2-naphthol, extraction with ammonium pyrrolidinedithiocarbamate, and chelation by 8-quinolinol (oxine) followed by adsorption on activated carbon. The quantitative characteristics of these techniques and the influence of the water matrix effects are discussed, as well as the applicability for x-ray fluorescence analysis.

Evidence for organically associated iron in nearshore pore fluids

The role of dissolved organic matter (DOM) in the speciation of trace metals in natural waters is poorly understood1–3. Although dissolved organic matter–iron associations have been observed in freshwater systems4–6, it has been thought that DOM–iron species are not significant in saline waters7. Yet recent studies have suggested that iron–DOM interactions in the pore waters of anoxic marine sediments may be important8,9. The possibility of organically associated trace metals in anoxic water has been used to explain why metal concentrations are higher than those predicted by sulphide-mineral equilibria10,11. We present here data that indicate that strong iron–DOM associations do occur in the anoxic pore waters of nearshore marine sediments and that both the total dissolved iron and organically associated iron change seasonally.

Irradiation techniques for the release of bound heavy metals in natural waters and blood

Irradiation techniques are compared with conventional acid digestion procedures for the release of bound heavy metals in natural waters and in blood, before their determination by anodic stripping voltammetry. Ultra-violet irradiation of acidified water with a 550-W mercury vapour lamp releases bound zinc, cadmium, lead and copper after 4 h. The same results can be achieved with a 30-Mrad dose of high-energy γ-irradiation. These techniques are also effective for the release of metals in whole blood and blood plasma, where sample volumes as small as 200 μl are adequate in analyses for zinc, copper and lead. By comparison with acid digestion and solvent extraction methods, irradiation treatments offer the advantages of minimum sample manipulation and negligible reagent blanks.

The rotating disc electrode in flowing systems : Part I. an anodic stripping monitoring system for trace metals in natural waters

The rotating disc electrode has been adapted for flow-through cell anodic stripping voltammetry in a flow-through cell. The enhanced sensitivity (compared with that obtained with the solution flowing past a stationary electrode) is the result of higher plating efficiency. During the plating period, mass transfer to the electrode is governed by electrode rotation; peak currents are unaffected by solution flow rate. A continuous deaeration system for solution flow rates up to 100 ml min -1 is described. The method is characterized by extreme simplicity, stability and precision, and is suitable for in situ monitoring of heavy metals in aqueous samples.

A batch method for the determination of ion-exchangeable trace metals in natural waters

A batch method for the determination of ion-exchangeable trace metals in natural waters is reported. The technique employs the resin Chelex 100 and has been tested for Cd, Cu, Pb, Zn and Fe using both synthetic and natural water samples. Quantitative recovery of ionic spikes was achieved and uptake was found to occur rapidly, being virtually completed within 1 h. Evidence is provided for the presence in the natural water samples of stable bound trace metal species. This batch method should prove particularly useful for field studies of the physicochemical forms of trace metals in aquatic environments.

Organic complexes of iron and aluminium in natural waters

IN natural waters throughout the world1, iron concentrations are commonly several orders of magnitude greater than the equilibrium solubility of iron hydroxide2. Highly coloured waters (which have relatively high concentrations of organic matter) commonly have even greater iron concentrations. Two of the chemical species postulated to account for this phenomenon are: (1) fine colloidal particles of iron hydroxide (possibly associated with colloidal organic matter) and (2) dissolved complexes of iron with naturally occurring organic substances. While the existence of colloidal iron hydroxide in natural waters is widely accepted3, there is little conclusive evidence for or against the existence of dissolved organic complexes of iron. We wish to present evidence which suggests that dissolved organic matter forms complexes not only with iron but also with aluminium, with competition between Fe and Al for available complexing sites determining the relative abundances of the two metals in natural waters.

Trace metal analysis by anodic stripping voltammetry: effect of sorption by natural and model organic compounds

A variety of model organic compounds representative of the types of organic substances occurring in natural waters were found to sorb onto hanging mercury drop electrodes in the anodic stripping voltammetric analysis of trace metals. Sorption effects on the ASV diagnostic parameters E p and i p (peak current and peak potential) were pH dependent, with greater effect under acidic conditions in some cases, and were significant at organic concentrations in the ppm range. Compounds tested included gelatin and alkaline phosphatase as representatives of soluble proteins. Triton X100 (a nonionic surfactant), and a variety of polysaccharides, including agar, alginic acid and starch. Effects of sorption included depressed i p values, shifts in E p to more positive values, and broader peaks. Implications of these effects on the interpretation of ASV measurements in terms of analysis and speciation of trace metals in natural waters are discussed.

A Comparison of Energy Dispersive XRF To AA for Specific Metals in Natural Waters

The growing need for multielement analytical capability is currently being emphasized by the ever broadening governmental regulations on metallic pollutants in water sources. These new regulations cover more elements and are more restrictive in the type and amounts allowable in waste water and natural sources. For example, the California Public Health Law of 1970 states that 0.01 ppm arsenic, 1.0 ppm barium, 0.01 cadmium, 0.05 ppm manganese and 5.0 ppm zinc are the limiting concentrations of these elements in drinking water. Monitoring programs, both for compliance-enforcement and general survey work, have become a greater burden on both governmental agencies and private inductries. While trace analysis in solutions presents certain difficulties to the analytical chemist, regardless of the technique used, the results of this study indicate that x-ray analysis provides a more useful analytical tool for routine work and offers multielement capability with minimal sample preparation.

Complexing Capacity of Natural Water--Its Significance and Measurement

Most of the trace metals in natural waters are believed to exist in complexed or chelated forms with the miscellaneous organic ligands of both natural and pollutants origin which regulate the availability of these metals in the system (1–5). Such a mechanism maintains a reservoir of metals ready for biological uses. The abundance of complexing ligands in a body of water thus determines the complexing capacity of the water and hence its regulating capability. The measurement of complexing capacity will add a new parameter to the chemistry of trace metals in the aquatic environment, especially in areas of biological uptake and toxicological studies (6,7). Such information is also pertinent in bioassay work where the knowledge of the possible forms of the metals after being added to a system is important. The measurement of complexing capacity of a water sample is based on the amount of copper ion being complexed by the organic ligands through direct complexation and/or displacement reaction. It is done by spiking several aliquots of a sample with increasing amounts of a copper solution. Then the uncomplexed copper is measured by a differential pulse anodic stripping voltammetric technique (8,9). After the complexing ligands in the sample have been saturated with copper, the peak current of free copper will increase linearly with the amount of the copper spikes. By extrapolating this linear curve back to zero peak current, the intercept on the X-axis represents the complexing capacity of the water expressed as equivalents of μ mole Cu/l. As the differential pulse anodic stripping voltammetry measurement of “free” copper is carried out in a system containing excess of copper ions, the peak current thus obtained represents the concentration of “free” copper. The amount of copper plated out from the labile complexes, if any, becomes insignificant (8). Table I illustrates some complexing capacity values of natural waters. Preliminary work on the chemical characterization of the complexing substances in lake water, using ultra-filtration techniques, indicated that these complexing compounds fall in an arbitrary molecular range of 1,000–10,000. Further investigations are being carried out to isolate and to characterize this fraction (9). The significance of complexing capacity of water on the effect and toxicity of copper ion on algal photosynthesis has also been investigated (10) using the 14C uptake technique with lake waters of different complexing capacity and with the original plankton species. It was observed that complexing capacity of a water body does not imply that the equivalent amount of copper can be taken up (masked) by the water without affecting the plankton growth, although it has been a recognized fact that chelating agents such as NTA, EDTA can mask up the toxicity of copper. Further studies are being carried out to find out the quantitative biological meaning of complexing capacity. The chemical and biological aspects of the problem must go hand in hand.

Device for field determination of selected heavy metals in natural waters

Device for field determination of selected heavy metals in natural waters

The role of calcium and magnesium ions in invasiveness of schistosome cercariae.

SummaryVital staining of pre-acetabular gland contents of Schistosoma mansoni cercariae by Alizarin Red S, the reversal or inhibition of this staining by Versene (EDTA), and selective staining of these glands with Glyoxal-bis (2 hydroxyanil) (or GBHA), is evidence of the presence of calcium ions therein. Whereas the GBHA technique employed is highly specific for Ca++, Versene and Alizarin Red S are not. The purplish color of ARS-stained glands indicates that their contents are at an alkaline pH before extrusion into the more neutral or acidic surrounding medium. This correlates with previous findings that the cercariae enzymes are most active in an alkaline range. Similar evidence of calcium in pre-acetabular gland contents of Schistosomatium douthitti cercariae is also presented.The decrease in cercarial invasiveness noted as a consequence of metal chelation correlated well with earlier reports of an inhibiting effect of chelating agents on penetration by S. mansoni cercariae, and on the activity of cercarial enzymes. A similar direct correlation between previously described effects of various ions on in vitro activity of extracted cercarial enzymes, and effects of these ions on penetration of S. mansoni cercariae—notably the potentiation of enzyme activity and penetrating ability by Ca++ and Mg++—has also been noted. Addition of Ca++ or Mg++ partially restored the penetrating ability of S. mansoni cercariae exposed to a chelating agent. Calcium chelation by Versene and Alizarin Red S similarly reduced invasiveness of S. douthitti cercariae.These data suggest first, that calcium ions in the pre-acetabular glands of S. mansoni cercariae function in a manner similar to that of a coenzyme or activator to lytic apo-enzymes contained therein, and also that in this capacity, calcium and/or magnesium ions are essential for successful invasion of the definitive host.It is suggested that differences in quality and quantity of heavy metal ions in natural waters may explain some of the variability found in schistosome infections from different laboratories as well as differences in intensities of infection in different endemic areas.

Di-β-Naphthylthiocarbazone (Dinaphthizone) Compared with Dithizone as an Analytical Reagent for the Determination of Trace Metals in Natural Waters. A Preliminary Investigation.

Di-β-Naphthylthiocarbazone (Dinaphthizone) Compared with Dithizone as an Analytical Reagent for the Determination of Trace Metals in Natural Waters. A Preliminary Investigation.

IMPROVED DITHIZONE FIELD TEST FOR HEAVY METALS IN WATER

In many areas of the Pacific Northwest, heavy run oft from rain, melting snow, and ice fields causes extreme dilution of the heavy metal content of natural waters. Actual field work has shown that in many areas it is only practical to apply geochemical methods in the search for copper and zinc if it is feasible to detect as little as 0.001 p.p.m. of these metals in natural waters. A modification of the dithizone methods which have already been described has been developed. This modified method is simple, as accurate as is necessary for field work, and can readily detect heavy metals in concentrations as low as 0.001 p.p.m. Under favourable conditions, even lower concentrations can be detected by an experienced field man. During the 1950 field season, we have started to refer to this modification in the use of dithizone as the “emulsion” technique, in contrast to the “classical” dithizone methods employed by earlier writers.

A sensitive field test for heavy metals in water

A semiquantitative colorimetric analytical method using dithizone to detect traces of heavy metals in natural water is described. Although reagents of exceptional purity are required, only simple equipment is needed and the test can be made in a few minutes in the field. A combined mixed color and mono color technique makes the test suitable for a wide range of concentrations. The test is very sensitive; as little as 0.01 part per million of either copper, lead, zinc or any combination of the three metals can be detected readily.The dithizone test permits rapid field identification of drainage elements which contain significant concentrations of heavy metals. An example is given showing how the test can be used to trace the heavy metal content of a drainage system back to its source. It is possible that, under favorable conditions, the field test may facilitate prospecting by detecting metals discharged by the weathering of hidden ore bodies. However, until the method receives further investigation, it would be premature to predict its value.