Geochemical characteristics of inorganic sulfur in Shijing River, South China

Different inorganic sulfur species distributed in overlying water, pore water and sediment in a heavily polluted river were determined. The concentrations of S(2-) and SO(4)(2-) in the overlying water were much more than those in the pore water. This result perhaps indicates the S(2-) was mainly from discharged wastewater, not from sediment resuspension. In the sediments, acid-volatile sulfide, chromium(ii)-reducible sulfide, and elemental sulfur were determined by a modified diffusion method. The results indicate that acid-volatile sulfide was the dominant component of the reduced inorganic sulfur, making up about 62% of the total reduced inorganic sulfur.     

Evolution of water chemistry in natural acidic environments in Yangmingshan,Taiwan

In Yangmingshan National Park, located in the northern part of the Taiwan Island, there is a very rare area where fish (Channa asiatica) live in spite of acid environments. The origin of the acid in local acid ponds and rivers and the evolution of the water chemistry are discussed on the basis of sulfur stable isotope ratios and chemical equilibria. One of the sources of the acid is sulfuric acid, which is derived from the oxidation of hydrogen sulfide in volcanic gas gushing out from fumaroles around the area and from acid deposition supplied from Taipei City. It is also derived from the oxidation of pyrite: the sulfur stable isotope ratios of delta 34S of +1@1000 to +4@1000 (relative to CDT) of sulfate in acid pond waters (pH 3-4) could be related to those of hydrogen sulfide in volcanic gas, pyrite in local pond sediments and soils, and sulfate in rain water. One acid source is sulfuric and hydrochloric acids arising in springs from geothermal activity: the delta 34S values were characterised by +13@1000 to +17@1000 sulfate-S, which was provided by a disproportionation reaction of sulfur dioxide in the depths. Another acid source could be the oxidation of iron(II). Under acidic conditions, the water-rock reaction gives rise to high concentrations of aluminium and iron. While flowing down surface streams, iron(II) is oxidised to iron(III) and then hydrolysed to cause further acidification under oxic conditions. The concentrations of iron and aluminium are controlled by redox and dissolution equilibria.     

Remote in situ voltammetric techniques to characterize the biogeochemical cycling of trace metals in aquatic systems

The contamination of aquatic ecosystems by natural and anthropogenic metals has lead to a need to better characterize their impact in the environment. To a large extent, the fate and the (eco)toxicity of these elements in aquatic systems are related to their chemical speciation, which may vary continuously in space and time. Detailed measurements of the fraction of specific metal species or groups of homologous metal species and their variation as a function of the bio-physicochemical conditions of the natural media are thus of prime importance. To determine these metal fractions as well as redox chemical species regulating their distribution (dissolved oxygen, sulfides, iron and manganese oxides), new analytical tools capable of performing in situ, real-time monitoring in both water columns and sediments with minimum perturbation of the media are required. This paper reviews the challenges associated with metal speciation studies, and the progress made with state of the art voltammetric techniques to measure the speciation of metals in situ. More specifically, it summarizes the specific conceptual, analytical, and technical criteria that must be considered and/or fulfilled to develop rugged, field deployable, non-perturbing sensors and probes. Strategies used to satisfy these criteria are presented by describing the up-to-date most advanced voltammetric sensors, mini-/micro-integrated analytical systems, and submersible equipments developed for in situ measurements of trace metals and main redox species in aquatic systems. The spatial and temporal resolutions achieved by these news tools represent a significant advantage over traditional laboratory techniques, while simultaneously remaining cost effective. The application of these tools to aquatic systems is illustrated by several examples of unattended and remote in situ monitoring and/or profiling in water columns and sediments.     

Speciation and preservation of inorganic arsenic in drinking water sources using EDTA with IC separation and ICP-MS detection

The native distribution of As(III) and As(v) in drinking water supplies can influence the treatment removal strategy. The stability of As(III) and As(v) in iron-rich drinking waters can be affected by the formation of Fe precipitates (Fe oxides and/or hydroxides designated by "FeOOH"). These precipitates (ppts) can form during the transport of the sample to the laboratory for arsenic speciation analysis. The analysis of the ppt indicates considerable loss of the aqueous arsenic species (As(aq)) to the solid phase "FeOOH" ppt. Studies of laboratory reagent water containing both As(III) and Fe(III) indicate that the resulting "FeOOH" ppt contained a mixture of As(III) and As(v) with near quantitative removal of the As(aq) in 18 hr. The corresponding aqueous fraction after filtration through a 0.45 microm filter was composed primarily of As(v). The formation of "FeOOH" ppt and the loss of As(aq) to the ppt can be virtually eliminated by the use of EDTA, which sequesters the FeIII). Reagent water fortified with Fe(III), As(III) and EDTA produced less than a 1 ppb change in the As(III)aq concentration over 16 d. The EDTA treatment was also tested on three well waters with different native As(III )/As(v) ratios. The native distribution of As(III)/As(v) was stabilized over a period of 10 d with a worst case conversion of As(III) to As(v) of 2 ppb over a 30 d period. All well waters not treated with EDTA had dramatic losses (a factor of 2-5) of As(aq) in less than 1 d. These results indicated that EDTA preservation treatment can be used to preserve As(aq) in waters where the predominant species is the reduced form [As(III)] or in waters which the predominant species is the oxidized form [As(v)]. This preliminary investigation of EDTA to preserve As species in Fe-rich waters indicates stability can be achieved for greater than 14 d.     

Arsenic Speciation Analysis in Water Samples: A Review of The Hyphenated Techniques

Interests in the determination of different arsenic species in natural waters is caused by the fact that toxic effects of arsenic are connected with its chemical forms and oxidation states. In determinations of water samples inorganic arsenate (As(III), As(V)), methylated metabolities (MMAA, DMAA) and other organic forms such as AsB, AsC, arsenosugars or arsenic containing lipids have the most importance. This article provides information about occurrence of the dominant arsenic forms in various water environments. The main factors controlling arsenic speciation in water are described. The quantification of species is difficult because the concentrations of different forms in water samples are relatively lowcompared to the detection limits of the available analytical techniques. Several hyphenated methods used in arsenic speciation analysis are described. Specific advantages and disadvantages of methods can define their application for a particular sample analysis. Insufficient selectivity and sensitivity of arsenic speciation methods cause searching for a new or modifications already existing techniques. Some aspects of improvement and modifications of the methods are highlighted.     

Phosphorous speciation in surface sediments of the Cochin estuary

Sequential chemical extraction using chelating agents were used to study the P dynamics and its bioavailability along the surface sediments of the Cochin estuary (southwest coast of India). Sediments were analyzed for major P species (iron bound P, calcium bound P, acid soluble organic P, alkali soluble organic P and residual organic P), Fe, Ca, total carbon, organic carbon, total nitrogen and total sulfur contents. An abrupt increase in the concentration of dissolved inorganic P with increasing salinity was observed in the study region. Iron-bound P exhibited a distinct seasonal pattern with maximum values in the monsoon season when fresh water condition was prevailed in the estuary. As salinity increased, the percentage of iron-bound P decreased, while that of calcium-bound P and total sedimentary sulfur increased. C/P and N/P ratios were low which indicate that large amounts of organic matter enriched with P tend to accumulate in surface sediments. The high organic P contribution in the sedimentary P pool may indicate high organic matter load with incomplete mineralization, as well as comparatively greater percentage of humic substance and resistant organic compounds. Principal component analysis is employed to find the possible processes influencing the speciation of P in the study region and indicate the following processes: (1) the spatial and seasonal variations of calcium bound P and acid soluble organic P was mainly controlled by sediment texture and organic carbon content, (2) sediment redox conditions control the distribution of iron bound P and (3) the terrigenous input of organic P is a significant processes controlling total P content in surface sediments. The bioavailable P was very high in the surface sediments which on an average accounts for 59 % in the pre-monsoon, 65 % in the monsoon and 53 % in the post-monsoon seasons. The surface sediments act as a potential internal source of P in the Cochin estuary.     

Chromium speciation in a contaminated groundwater: redox processes and temporal variability

Chromium species (Cr(III), Cr(VI), and Cr(III)-organic) in groundwater of a tannery contaminated area were monitored during pre- and post-monsoon seasons for a period of 3 years (May 2004 to January 2007). The objectives of the study were (1) to investigate the temporal variation of chromium species and other matrix constituents and (2) to study the redox processes associated with the temporal variation of chromium species. Samples were collected from 15 dug wells and analyzed for chromium species and other constituents. The results showed that the groundwater was relatively more oxidizing during post-monsoon periods than the pre-monsoon periods. Except one sample, the concentration of chromium species were found in the order of Cr(VI)>Cr(III)>Cr(III)-organic complexes during all the pre- and post-monsoon periods. In most of the wells, the concentrations of Cr(III), Cr(VI), and Cr(III)-organic decreased during post-monsoon periods compared to their pre-monsoon concentrations. However, the Cr(VI)/Cr_Total ratio still increased and the Cr(III)/Cr_Total ratio decreased during post-monsoon periods in most of the samples. The possible mechanisms for the temporal variation of chromium species were (1) Fe(II) reduction of Cr(VI) vs oxidation of Fe(II) by dissolved oxygen and (2) oxidation of Cr(III) by Mn(IV).     

Investigation of arsenic speciation on drinking water treatment media utilizing automated sequential continuous flow extraction with IC-ICP-MS detection

Three treatment media, used for the removal of arsenic from drinking water, were sequentially extracted using 10 mM MgCl2(pH 8), 10 mM NaH2PO4(pH 7) followed by 10 mM (NH4)2C2O4(pH 3). The media were extracted using an on-line automated continuous extraction system which allowed the arsenic in each of the extraction fluids to be speciated on-line using IC-ICP-MS. The 10 mM MgCl2 preferentially extracted As(III) from each of the media. The percentage of the arsenic extracted by the MgCl2, relative to a HNO3/H2O2 digestion of the media, ranged from 0.1-2.3% for the three solids. The next sequential extraction fluid, 10 mM NaH2PO4, extracted some of the residual As(III) remaining on each of the media but the predominant species extracted was As(V). The 10 mM NaH2PO4 extracted 15.3 to 42.8% of the total arsenic relative to a total digested concentration for each of the media. The As(III) and As(V) stability studies conducted in these two extraction fluids indicated that conversion between As(III) and As(V) was not significant for the short extraction fluid sample contact time associated with the on-line continuous flow extraction cell. Finally, the 10 mM (NH4)2C2O4 extraction fluid was utilized in an off-line analysis mode because the Fe and As concentrations extracted from the media were not compatible with direct ICP-MS detection. The (NH4)2C2O4 extracted 2.9-29% As(III) for all three media and caused an oxidation of As(III) to As(V) during the extraction period for one of the three media. The sum of the arsenic from each of the three extraction fluids represented 92%, 44% and 53% of the available total arsenic for the three media, respectively. The speciation results for each media were obtained by adding all the speciation results from all three extraction fluids together and the resulting distribution of As(III)/As(V) compared well with the speciation results obtained via XANES.     

Geochemistry and pH control of seepage from Ni-Cu rich mine tailings at Selebi Phikwe,Botswana

Acid mine drainage from mine tailings at Selebi Phikwe, eastern Botswana, has been investigated using a combination of total decomposition, sequential extraction, X-ray diffraction, Mössbauer spectroscopy, and SEM analyses of solid phase samples, water analyses, isotopic analyses, and geochemical modeling. The principal ferric phases in the seepage stream sediments are jarosite and goethite, which incorporate Ni and Cu. The Mössbauer spectroscopy (MS) indicated exclusively 3+ oxidation state of iron with typical features of ferric hydroxides/sulfates. A fraction of dissolved sulfate is also sequestered in gypsum which precipitates further downstream. Significant portions of Fe, Ni, and Cu are transported in suspension. Values of pH decreased downstream due to H⁺ generated by the precipitation of jarosite. Values of δ²H and δ¹⁸O indicate evaporation of pore water in the mine tailings before seepage. Values of δ³⁴S(SO₄) are consistent with the oxidation of sulfides, but sample from the seepage face is affected by dissolution of gypsum. No minerals of Ni and Cu were detected and the principal attenuation processes seem to be adsorption and co-precipitation with jarosite. Higher contents of Cu are sequestered in solid phases compared to Ni, in spite of much higher dissolved Ni concentrations. Based on the speciation calculations, seepage water is undersaturated with respect to all Ni and Cu phases and adsorption and co-precipitation with jarosite seems to be the principal attenuation processes. Direct geochemical modeling was able to reproduce downstream pH trends, thus confirming the precipitation of jarosite as the principal pH-controlling process.     

Arsenic-speciation in arsenate-resistant and non-resistant populations of the earthworm,Lumbricus rubellus

Arsenic speciation was determined in Lumbricus rubellus Hoffmeister from arsenic-contaminated mine spoil sites and an uncontaminated site using HPLC-MS, HPLC-ICP-MS and XAS. It was previously demonstrated that L. rubellus from mine soils were more arsenate resistant than from the uncontaminated site and we wished to investigate if arsenic speciation had a role in this resistance. Earthworms from contaminated sites had considerably higher arsenic body burdens (maximum 1,358 mg As kg-1) compared to the uncontaminated site (maximum 13 mg As kg-1). The only organo-arsenic species found in methanol/water extracts for all earthworm populations was arsenobetaine, quantified using both HPLC-MS and HPLC-ICP-MS. Arsenobetaine concentrations were high in L. rubellus from the uncontaminated site when concentrations were expressed as a percentage of the total arsenic burden (23% mean), but earthworms from the contaminated sites with relatively low arsenic burdens also had these high levels of arsenobetaine (17% mean). As arsenic body burden increased, the percentage of arsenobetaine present decreased in a dose dependent manner, although its absolute concentration rose with increasing arsenic burden. The origin of this arsenobetaine is discussed. XAS analysis of arsenic mine L. rubellus showed that arsenic was primarily present as As(III) co-ordinated with sulfur (30% approx.), with some As(v) with oxygen (5%). Spectra for As(III) complexed with glutathione gave a very good fit to the spectra obtained for the earthworms, suggesting a role for sulfur co-ordination in arsenic metabolism at higher earthworm arsenic burdens. It is also possible that the disintegration of As(III)-S complexes may have taken place due to (a) processing of the sample, (b) storage of the extract or (c) HPLC anion exchange. HPLC-ICP-MS analysis of methanol extracts showed the presence of arsenite and arsenate, suggesting that these sulfur complexes disintegrate on extraction. The role of arsenic speciation in the resistance of L. rubellus to arsenate is considered.     

Speciation of iron in river water using a specific catalytic determination and size fractionation

A comprehensive speciation scheme was proposed for the speciation of iron in river water (0.45 microm filtrate). The speciation was based on the catalytic determination of reactive iron as Fe3+ and Fe(III)Li/(3 -in)+, where i = 1 or 2 for a unidentate and i = 1 for a bidentate ligand, Ln-. The scheme incudes size fractionation and acid decomposition of the sample and determination of the coexisting species. The proposed scheme was applied to natural and artificial samples and acidified preparations of these. Resulting fractionation patterns of reactive and unreactive iron and of coexisting humic acid were useful for the characterization of iron species in the natural samples. The reactive iron in the molecular weight (Mr) > or = 10(4) fraction was associated with humic iron aggregates and estimated as iron complexed with them. The unreactive iron in this fraction dissociated in 0.1 M HCI and was estimated as iron in the aggregates of iron(III) hydroxide (s) and humic iron. From the fractionation results of the artificial sample, the reactive and unreactive iron in the Mr < 10(3) fraction may be formed by complexing simple anions like F- and C2O4(2-) at their naturally-occurring concentration levels. The fractionation results also suggested that humic acid and Si contributed to the formation of reactive and unreactive iron in the Mr > or = 10(4) fraction.     

Tuning the surfaces of palladium nanoparticles for the catalytic conversion of Cr(VI) to Cr(III)

This work reports the feasibility of using Pd nanoparticles as innovative catalysts in the conversion of reducible contaminants from toxic to benign forms. Cr(VI) is a known carcinogen while the trivalent chromium salts are believed to be non-toxic. The ability of Pd nanoparticles to catalyze the rapid reduction of Cr(VI) to Cr(III) using reactive sulfur intermediates produced in situ was therefore studied. Using a microchamber set at 130 degrees C, the reduction mixture consists of palladium nanoparticles and sulfur (PdNPs/S), which generated highly reducing sulfur intermediates that effected the reduction of Cr(VI) to Cr(III) by 1st order reaction kinetics. UV-visible spectroscopy and cyclic voltammetry were employed to monitor the reduction process. The results showed that 99.8% of 400 microM Cr(VI) was reduced to Cr(III) by PdNPs/S in one hour compared to 2.1% by a control experiment consisting of sulfur only. The rate of Cr(VI) reduction was found to be dependent on temperature and pH and was greatly enhanced by the addition of PdNPs. Subsequent application of this approach in the reduction of Cr(VI) in soil and aqueous media was conducted. In contrast to the control experiments with and without PdNPs or sulfur, greater than 92% conversion rate was obtained in the presence of PdNPs/S within 1 hour. This represents over a 500-fold improvement in conversion rate compared to current microbial approaches. XPS analysis provided the confirmation regarding the oxidation states of Cr(VI), Cr(III) and the nature of the reactive intermediates. This work offers PdNPs/S as a new interface for the reduction of high oxidation state heavy metal pollutants.     

Iron and sulfur geochemistry in semi-arid mangrove soils (Ceará, Brazil) in relation to seasonal changes and shrimp farming effluents

Iron and sulfur are key elements in the biogeochemistry of estuarine soils, in which Fe and sulfate reduction (SR) pathways are important for organic matter decomposition. In the semi-arid coast of NE Brazil, mangroves are characterized by large seasonal variations in weather and the presence of numerous shrimp farms. The objective was to determine the impacts of shrimp farm effluents on iron and sulfur geochemistry in mangrove soils under the semi-arid climate of NE Brazil. A seasonal study was made of two mangrove forest soils (SF, a mangrove forest that directly receives wastewater from shrimp ponds and CS, a control site). Pyrite Fe, oxyhydroxides Fe, acid volatile sulfide, degree of pyritization (DOP), pH, Eh, total organic carbon (TOC) and total S were determined. There was a clear decrease in pyritic Fe and DOP in the SF soils, which may be related to the anaerobic oxidation of pyrite coupled with nitrate reduction, or to the dominance of denitrification over SR. Lower TOC contents in the SF site suggest that below ground decomposition increased in response to eutrophication. The seasonal variations led to important changes in the semi-arid mangrove soils. During the dry period, both soils experienced oxidizing conditions with remarkable loss of reduced and oxidized forms of Fe, which may have important environmental implications as Fe is biolimiting for marine primary production. The data show that both factors (seasonal weather variations and shrimp effluents) play important roles in the geochemical processes that occur in these soils and, thus, may affect their functioning and maintenance.     

Speciation of metals in bed sediments and water of Qaraaoun Reservoir, Lebanon

Determination of only total element in sediments does not give an accurate estimate of the likely environmental impacts. Speciation study of metals in sediment provides information on the potential availability of metals (toxic) to biota under various environmental conditions. In water, the toxic metal specie is the free hydrated metal ion. The toxicity of metals depends especially on their chemical forms rather than their total metal content. The present study focuses on Qaraaoun Reservoir, Lebanon. Earlier studies focused only on total metal concentrations in sediment and water. The objective of this study was to determine metal speciation (Fe, Cr, Ni, Zn, Cu, Pb, Cd) in the (operationally defined) sediment chemical fractions and metal speciation in reservoir water. This would reflect on metal bioavailability and toxicity. Water samples and bed sediments were collected from nine sites during the dry season and a sequential chemical fraction scheme was applied to the <75-??m sieve sediment fraction. Metal content in each fraction was determined by the FAAS technique. The data showed that the highest percentages of total metal content in sediment fractions were for: Fe in residual followed by reducible, Cr and Ni in residual and in reducible, Cu in organic followed by exchangeable, Zn in residual and in organic, Pb in organic and carbonate, Cd was mainly in carbonate. Total metal content in water was determined by ICP-MS technique and aqueous metal speciation was predicted using AQUACHEM software interfaced to PHREEQC geochemical computer model. The water speciation data predicted that a high percentage of Pb and Ni were present as carbonate complex species and low percentages as free hydrated ions, highest percentage of Zn as carbonate complex species followed by free hydrated ion, highest percentage of Cd as free hydrated ion followed by carbonate complex species. The sensitivity attempt of free hydrated ion of Ni, Zn, Pb, and Cd in reservoir water revealed dependence of Zn and Cd on pH and alkalinity, while Ni and Pb were only dependent on pH.     

Chemical speciation of inorganic pollutants in river–estuary–sea water systems

Monitoring studies and thermodynamic modeling were used to reveal the changes of inorganic chemical species of some water pollutants (nutrients and trace metals such as Fe, Mn, Zn, Cu, Cd and Pb) inthe river-estuary-sea water system. The case studies were two rivers, Kamchiya and Ropotamo, representing part of the Bulgarian Black Sea water catchment area, and having different flow characteristics. There were no major differences in inorganic chemical species of the two river systems. NO3(-) and NO2(-) chemical species showed no changes along the river-estuary-sea water system. Concerning phosphates six different species were calculated and differences between the three parts of the systems were established. The HPO4(2-) and H2PO4(-) species were found to be dominant in river waters. The H2PO4(-) species quickly decreased at the expense of HPO4(2-) and Ca, Mg and Na phosphate complexes in estuary and seawater. Trace metals showed a great variety of chemical species. Fe(OH)2(+) species prevailed in river waters, and Fe(OH)3(0) species--in sea waters. Me2+ and MeCO3(0) (Me = Cu, Pb) and PbHCO3(+) were dominant in river waters, while Cu(CO3)2(2-) and PbCl(-) species appear also in sea waters. Cd2+ species prevailed in river and estuary waters, and CdCln(2-n) (n = 1-3) species, in seawater. Free Zn2+ species predominated in all systems but downstream their percentage decreased at the expense of Zn phosphates, carbonates,sulfates and chlorides complexes. Only free Mn2+ species were dominant along the systems.     

Chromium speciation in groundwater of a tannery polluted area of Chennai City, India

Chromium speciation in groundwater of a tannery polluted area was investigated for the distribution of chromium species and the influence of redox couples such as Fe(III)/Fe(II) and Mn(IV)/Mn(II). Speciation analysis was carried out by ammonium pyrolidinedithiocarbamate (APDC)–methylisobutylketone (MIBK) procedure. The groundwater samples were analyzed for Cr(III), Cr(VI), and Cr(III)-organic complexes. The APDC could not extract the Cr(III)-organic complexes, but HNO₃ digestion of the groundwater samples released the Cr(III)-organic complexes. The groundwater of the area is relatively oxidizing with redox potential (E _h) and dissolved oxygen (DO) ranged between 65 and 299 mV and 0.25 and 4.65 mg L^???1, respectively. The Fe(II) reduction of Cr(VI) was observed in some wells, but several wells that had Fe(II)/Cr(VI) concentrations more than the stoichiometric ratio (3:1) of the reduction reaction also had appreciable concentration of Cr(VI). This could partly be due to the oxidation of Fe(II) to Fe(III) by DO. It appears that the occurrence of Mn more than the Fe(II) concentration was also responsible for the presence of Cr(VI). Other reasons could be the Fe(II) complexation by organic ligands and the loss of reducing capacity of Fe(II) due to aquifer materials, but could not be established in this study.     

Field cryofocussing hydride generation applied to the simultaneous multi-elemental determination of alkyl-metal(loid) species in natural waters using ICP-MS detection

Two hydride generation manifold systems, utilizing flow injection and cryotrapping techniques for alkyl-metal(loid) speciation analysis in natural waters, are described in this paper. They provide shipboard capacity for simultaneous derivatization of analytes with NaBH4 and cryotrapping of the generated products in a field packed column at -196 degrees C. The first system is a large-volume hydride generator, using a reagent-injection flow technique as a flow batch type, that has been fully optimized and applied to the simultaneous detection of alkylated species in estuarine waters. The technique permits the analysis of a large volume sample (0.5-11) at a sampling rate of 3 h-1. The second is an online continuous flow hydride generator. A sampling rate of 3-12 h-1 can be achieved with samples of 0.1-0.51. In addition, shipboard operation eliminates major problems related to sample pretreatment, transport and storage. Ultra-trace multi-element determination is finally performed in the laboratory by cryogenic GC hyphenated with ICP-MS. Routine detection limits of 0.5-10 pg (as metal) for 0.51 water samples were achieved for the selected alkyl-metal(loid) species of arsenic, germanium, mercury and tin. Concentrations of various species, obtained from water samples taken from the Rhine estuary, are also presented. These species include alkylated arsenic compounds, other than methyl derivatives, that have been tentatively identified and are reported here for the first time.     

An appraisal of changes in seasonal water quality during passage through a shallow reservoir in Western Poland

Following restoration changes in Antoninek Reservoir physico-chemical and biological processes in the water column and bottom sediments were measured to outline mechanisms of changes in nitrogen, phosphorus and organic matter concentrations during water flow through this reservoir. Intensive mineralisation of organic matter in the shallow sediments stimulated primary production and influenced increasing ammonia and nitrite nitrogen concentrations. Two main factors affected concentrations of phosphorus: (1) its presence in the external loads of river waters entering the reservoir, more important in the colder seasons as the water discharge was higher and (2) from the internal loads coming from bottom sediments. The quality of the river water during its flow through this reservoir improved for most parameters and seasons. However, concentrations of nutrients were still high in waters flowing out from the reservoir and in some months they were higher in the outflow than in waters entering the reservoir.     

Speciation of arsenic using solid phase extraction cartridges

Various solid phase extraction (SPE) cartridges were investigated for speciation of arsenite [As(III)], arsenate [As(v)], monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA). Cartridges containing different types of sorbent materials were tested for arsenic retention and elution characteristics. Alumina cartridges were found to completely retain all the four target arsenic species, and are suitable for removal and preconcentration purposes. For speciation analysis, different arsenic species were separated on the basis of their selective retention on and elution from specific cartridges. DMA was retained on a resin-based strong cation exchange cartridge and eluted with 1.0 M HCl. MMA and As(v) were both retained on a silica-based strong anion exchange cartridge and sequentially eluted with 60 mM acetic acid (for MMA) and 1.0 M HCl [for As(v)]. As(III) was not retained on either cartridge and remained in solution. Arsenic species in solution and those eluted from the cartridges were subsequently quantified by using flow injection with hydride generation atomic fluorescence spectrometry (FI-HGAFS) and hydride generation atomic absorption spectrometry (FI-HGAAS). A detection limit of 0.05 microg L(-1) arsenic in water sample was achieved using HGAFS. An application of the method was demonstrated at a drinking water treatment facility. As(III) and As(v) species were determined in water at various stages of treatment. The method is suitable for routine determination of trace levels of arsenic in drinking water to comply with more stringent environmental regulations.     

Relationships Between Toxicity and Concentrations of Chemical Contaminants in Sediments from Sydney Harbour, Australia, and Vicinity

Correlation analyses between measures of toxicity and concentrations of chemical contaminants were conducted for 103 surficial sediments from Sydney Harbour, Australia, and vicinity. Toxicity tests consisted of amphipod survival and reburial tests of whole sediments (Corophium colo), sea urchin fertilisation and larval development tests of pore waters (Heliocidaris tuberculata) and microbial bioluminescence (Microtox) tests of solvent extracts and pore waters. Toxicity in most tests correlated with concentrations of metallic contaminants, in particular, zinc, lead and copper. Organic contaminants did not correlate as significantly with toxicity. However, Heliocidaris tuberculata showed relationships with organochlorine compounds in samples with low to moderate metals contamination. Toxicity in the Microtox solvent extract test appeared to be primarily influenced by the presence of sulfur. This study has no precedent in Australia and the results support the validity of using local indigenous species in toxicity tests of field-collected sediments. This toxicity/chemistry dataset may be used in evaluations of sediment quality guidelines recently introduced to Australia.