Dissolved Metal Concentrations Research Articles

Bioremediation of Acidic and Metalliferous Drainage (AMD) through organic carbon amendment by municipal sewage and green waste

Pit lakes (abandoned flooded mine pits) represent a potentially valuable water resource in hot arid regions. However, pit lake water is often characterised by low pH with high dissolved metal concentrations resulting from Acidic and Metalliferous Drainage (AMD). Addition of organic matter to pit lakes to enhance microbial sulphate reduction is a potential cost effective remediation strategy. However, cost and availability of suitable organic substrates are often limiting. Nevertheless, large quantities of sewage and green waste (organic garden waste) are often available at mine sites from nearby service towns.We treated AMD pit lake water (pH 2.4) from tropical, North Queensland, Australia, with primary-treated sewage sludge, green waste, and a mixture of sewage and green waste (1:1) in a controlled microcosm experiment (4.5 L). Treatments were assessed at two different rates of organic loading of 16:1 and 32:1 pit water:organic matter by mass. Combined green waste and sewage treatment was the optimal treatment with water pH increased to 5.5 in only 145 days with decreases of dissolved metal concentrations. Results indicated that green waste was a key component in the pH increase and concomitant heavy metal removal. Water quality remediation was primarily due to microbially-mediated sulphate reduction. The net result of this process was removal of sulphate and metal solutes to sediment mainly as monosulfides. During the treatment process NH3 and H2S gases were produced, albeit at below concentrations of concern. Total coliforms were abundant in all green waste-treatments, however, faecal coliforms were absent from all treatments. This study demonstrates addition of low-grade organic materials has promise for bioremediation of acidic waters and warrants further experimental investigation into feasibility at higher scales of application such as pit lakes.

Chitosan membranes as sorbents for trace elements determination in surface waters

Chitosan membranes (non-crosslinked, crosslinked, and modified with L-cysteine) were evaluated as sorbents prior to electrothermal atomic absorption spectrometry (ETAAS) determination of total dissolved metal content in surface water samples. Different types of chitosan membranes were prepared in the presence or absence of L-cysteine. Chemical parameters for quantitative sorption/desorption of trace analytes have been optimized. The optimal pH for Cd(II), Cu(II), Ni(II), and Pb(II) sorption using L-cysteine-modified membrane is between 7 and 8.5 and coincides with typical surface water pH, allowing in situ preconcentration of analytes without any additional water sample pretreatments. Non-crosslinked chitosan membrane could be used for simultaneous sampling, transportation, and laboratory determination of Hg(II). Determination limits (calculated as 10σ) achieved for total dissolved metal contents are: Cd 0.001 μg/L, Cu 0.02 μg/L, Ni and Pb 0.05 μg/L, and relative standard deviations were 10-15% for all elements at concentration level of 0.05-2 μg/L. The determination limit achieved for Hg(II) was 0.012 μg/L and relative standard deviations at concentration levels 0.015-2 μg/L were within 9% and 15%. Non-crosslinked chitosan membrane was proposed as an efficient sorbent for Hg(II) preconcentration and determination in river and lake waters; L: -cysteine modified chitosan membrane was recommended for solid phase extraction of Cd(II), Cu(II), Ni(II), and Pb(II) from surface (lake, river, and sea) waters. The application of chitosan membranes as adsorbents for in situ field preconcentration of the analytes and their subsequent determination by CVAAS and ETAAS in water samples has been demonstrated.

Temporal variability in dynamic and colloidal metal fractions determined by high resolution in situ measurements in a UK estuary

In recent environmental legislation, such as the Water Framework Directive in the European Union (WFD, 2000/60/EC), the importance of metal speciation and biological availability is acknowledged, although analytical challenges remain. In this study, the Voltammetric In situ Profiler (VIP) was used for high temporal resolution in situ metal speciation measurements in estuarine waters. This instrument simultaneously determines Cd, Cu and Pb species within a size range (ca. <4 nm) that is highly relevant for uptake by organisms. The colloidal metal fraction can be quantified through a combination of VIP measurements and analyses of total dissolved metal concentrations. VIP systems were deployed over tidal cycles in a seasonal study of metal speciation in the Fal Estuary, southwest England. Total dissolved concentrations were 4.97–315 nM Cu, 0.13–8.53 nM Cd and 0.35–5.75 nM Pb. High proportions of Pb (77 ± 17%) and Cu (60 ± 25%) were present as colloids, which constituted a less important fraction for Cd (37 ± 30%). The study elucidated variations in the potentially toxic metal fraction related to river flow, complexation by organic ligands and exchanges between dissolved and colloidal phases and the sediment. Based on published toxicity data, the bioavailable Cu concentrations (1.7–190 nM) in this estuary are likely to severely compromise the ecosystem structure and functioning with respect to species diversity and recruitment of juveniles. The study illustrates the importance of in situ speciation studies at high resolution in pursuit of a better understanding of metal (bio)geochemistry in dynamic coastal systems.

How does storage affect the quality and quantity of organic carbon in sewage for use in the bioremediation of acidic mine waters?

Pit lakes (abandoned flooded mine pits) represent a potentially valuable water resource. However, acid mine drainage (AMD) generation due to mining activities often results in pit lake waters with low pH, high sulphate and dissolved metal concentrations. Sulphate reduction-based bioremediation offers tremendous scope for removal of acidity and metals from pit lake water. In this study, the effect of storing sewage on its carbon quality for bioremediation of acidic pit lake water was studied. In addition, the effectiveness of labile organic carbon (lactic acid and ethanol) on SRB activity was tested. Bioremediation experiments were performed in controlled and replicated microcosms with acidic (pH 2.2) water from a pit lake by addition of stored (3 years at 4°C) sewage for stimulation of sulphate reducing bacteria (SRB) activity. This sewage had been previously used successfully in remediating to pH 7 water from this pit lake. The initial aim was to test the sewage at lower doses (18 and 28g/L) and in a pulsed addition (over 5 weeks). Bioremediation efficacy was evaluated by measuring pit lake water pH increase, redox potential decrease, and acidity and sulphate removal. Though the stored sewage had retained a very similar high total organic carbon (TOC) equivalent to prior to storage, it failed to increase dissolved organic carbon (DOC) levels in pit lake water. Microcosms amended with doubled doses of sewage and an extended remediation time still failed to demonstrate any substantial improvement in water quality, other than a small amount of sulphate reduction and direct neutralisation by the sewage. In order to determine if low DOC concentrations in sewage were the cause of the bioremediation failure, labile organic carbon (LOC), consisting of 50:50 (w/w) lactic acid and ethanol, was added to all microcosm treatments at concentrations of 3000, 6000 and 9000mg/L. After LOC addition, water quality improved with effective removal of acidity, sulphate and metals in the lowest carbon concentration (3000mg/L). However, 6000 and 9000mg/L LOC concentrations showed a delay in response due to the increased acidity associated with the lactic acid addition. The experiments showed that pulsed dosing of carbon simply slowed the commencement of remediation but it was ultimately able to reach the same effectiveness as the equivalent quantity added all at once. Prolonged storage of sewage leads to loss of LOC. In situ pit lake remediations which aim to make use of sewage as the main carbon source will need to factor in the storage time required to obtain sufficient sewage for the treatment into the design. Pulsing may help reduce issues with storage or supplementation with LOC may need to be considered. Results highlight that LOC is a more useful indicator of material effectiveness compared to a simple measures of TOC.

Homogeneous Catalysis of Liquid-Phase Hydroperoxide Decomposition in Hydrocarbons

The autoxidation of jet fuel takes place via a complex free radical reaction mechanism that involves the decomposition of hydroperoxides.The liquid-phase, unimolecular decomposition of hydroperoxide has been isolated for experimental study. Three hydroperoxides relevant to jet fuel autoxidation, including cumene hydroperoxide (CHP), dodecane hydroperoxide (DHP), and ethylbenzene hydroperoxide (EBHP), were thermally decomposed separately and found to closely fit first-order behavior with respect to hydroperoxide concentration. The activation energy for liquid-phase thermolysis of these hydroperoxides was found to be significantly less than typical gas-phase values. Parameters affecting the rate of hydroperoxide decomposition, such as dissolved metal content, organic acids, and metal deactivator additive (MDA) were explored. Metal type was shown to be a significant factor affecting hydroperoxide decomposition rate, while naphthenic acids (NA) were shown to have little effect on the rate. However, when disso...

Influence of the Amazon River on dissolved and intra-cellular metal concentrations in &amp;lt;i&amp;gt;Trichodesmium&amp;lt;/i&amp;gt; colonies along the western boundary of the sub-tropical North Atlantic Ocean

Abstract. Despite the ecological importance of Trichodesmium spp. for the global oceanic nitrogen budget, there is limited information on their trace metal composition in field samples. We report dissolved (&lt;0.22 μm) metal concentrations measured in surface waters (Ag, Cd, Co, Cu, Fe, Mo, Ni, P, Pb and V) and in the total and the intracellular pool (Ag, Al, Cd, Co, Cu, Fe, Mn, Mo, Ni, P, Pb, V) of Trichodesmium populations collected in the western subtropical North Atlantic Ocean (April–May 2003) within the influence of the Amazon River plume. Dissolved element distributions were strongly influenced by the River discharge, with concentrations of some elements varying directly (i.e. Cd, Mo and V) or inversely (Ag, Co, Cu, Fe, Ni, P and Pb) with surface salinity. Intracellular metal values to phosphorous ratios (mol:mol) for Cd, Co, Cu, Fe, Mn, Mo, Ni and V ranged from 9.0 × 10−6 for Cd to 4.4 × 10−2 for Fe. Although total metal composition was significantly correlated with the intracellular content in the Trichodesmium colonies for some elements (e.g., Co, Cu, V), metal pools in the phytoplankton did not co-vary with the dissolved metal concentrations, suggesting that water column measurements may not be good predictors of the intracellular metal concentrations. The impact of physical parameters and bioactive elements on biological processes such as nitrogen fixation, carbon drawdown and biomass production in Trichodesmium colonies was explored by using a principal component analysis test (PCA). The analysis indicated that the biological drawdown of dissolved inorganic carbon (DIC) by Trichodesmium seems to be influenced by the internal content of Fe, Co, Cd, and Cu, while nitrogen fixation seems more influenced by mixed layer depth and dissolved Fe and Ni concentrations.

Sources of Cu, Zn, Cd and Pb in rainwater at a subtropical islet offshore northern Taiwan

Abstract Pollutants derived from long-range transport and local emission impact significantly of heavy metal compositions in rainwater and aerosols. To identify their sources and relative contributions in rainwater, 47 monthly rainwater samples from January 1998 to December 2001, collected at Peng Chia Yu (PCY), a non-residential islet offshore Taiwan, were analyzed for heavy metals (i.e. Cu, Zn, Cd, and Pb) and Pb isotopic compositions. The dissolved metals concentrations of Al, Mn, Fe, Cu, Zn, Rb, Ba, and Pb in PCY rains are high in spring and winter, but low in summer. This can be understood in terms of pollutant source changes due to wind direction shifted seasonally. The average EFcrust and EFseawater values calculated for Cu, Zn, Cd and Pb are far greater than 1500, suggesting their strong anthropogenic sources, also supported by the PCA results. The pollutants derived from long-range transport are the predominated heavy metals sources during the winter monsoon season, whereas local traffic emissions play the most important role during the summer monsoon period. Unique Pb isotopic fingerprints, similar to those of iron ore sinter dusts and oil combustion dusts from Shanghai and the traffic emissions from Taiwan were identified in PCY rainwater. A mixing model based on three typical end-member Pb isotopic compositions derived from Taiwan and China was applied to evaluate the pollutant sources variations.

Solid phase extraction and diffusive gradients in thin films techniques for determination of total and labile concentrations of Cd(II), Cu(II), Ni(II) and Pb(II) in Black Sea water

Total dissolved and labile concentrations of Cd(II), Cu(II), Ni(II) and Pb(II) were determined at six locations of the Bourgas Gulf of the Bulgarian Black Sea coast. Solid phase extraction procedure based on monodisperse, submicrometer silica spheres modified with 3-aminopropyltrimethoxysilane followed by the electrothermal atomic absorption spectrometry (ETAAS) was developed and applied to quantify the total dissolved metal concentrations in sea water. Quantitative sorption of Cd, Cu, Ni and Pb was achieved in the pH range 7.5–8, for 30 min, adsorbed elements were easily eluted with 2 mL 2 mol L−1 HNO3. Since the optimal pH for quantitative sorption coincides with typical pH of Black Sea water (7.9–8.2), on-site pre-concentration of the analytes without any additional treatment was possible. Detection limits achieved for total dissolved metal quantification were: Cd 0.002 µg L−1, Cu 0.005 µg L−1, Ni 0.03 µg L−1, Pb 0.02 µg L−1 and relative standard deviations varied from 5–13% for all studied elements (for typical Cd, Cu, Ni and Pb concentrations in Black Sea water). Open pore diffusive gradients in thin films (DGT) technique was employed for in-situ sampling and pre-concentration of the sea water and in combination with ETAAS was used to determine the proportion of dynamic (mobile and kinetically labile) species of Cd(II), Cu(II), Ni(II) and Pb(II) in the sea water. Obtained results showed strong complexation for Cu and Pb with sea water dissolved organic matter. The ratios between DGT-labile and total dissolved concentrations found for Cu(II) and Pb(II) were in the range 0.2–0.4. For Cd and Ni, these ratios varied from 0.6 to 0.8, suggesting higher degree of free and kinetically labile species of these metals in sea water.

Chemical speciation and partitioning of trace metals (Cd, Co, Cu, Ni, Pb) in the lower Athabasca river and its tributaries (Alberta, Canada)

Concentrations of Cd, Co, Cu, Ni and Pb were measured in particulate and dissolved phases at 11 sites located upstream and near Athabasca oil sands development. The in situ discrimination between non-labile and labile dissolved metals was done using diffusive gradients in thin-films (DGT) devices. The DGT-labile fraction of Co and Ni was 30% lower near development sites whereas Cu, Cd and Pb showed minor changes spatially. It was found that an 8-fold increase in dissolved organic matter (DOM) near development induced a rapid decrease in DGT-labile metals. Dissolved metal concentrations were used along with DOM, major ions, nutrients, pH and conductivity to calculate the distribution of dissolved metal species using the speciation model WHAM. Labile-DGT metal concentrations agreed well with WHAM-predicted concentrations. It was also found that a significant amount of metals were associated with the non-DGT labile fraction (i.e. colloidal DOM) and colloid abundance was more important than suspended particulate matter abundance in influencing metal mobility near Athabasca oil soils development. Since changes in colloidal DOM levels are likely to be the result of surface mining activities, this confirms the serious effects of oil sands activities on metal biogeochemical cycles in the lower Athabasca River.

Application of artificial mussels (AMs) under South African marine conditions: A validation study

Over the last three decades there has been a significant decline in the number of marine pollution monitoring-related studies in South Africa. Thus, the current study was conducted to assess the current state of metal contamination within the South African marine environment through the validation of the artificial mussel (AM). Indigenous reference mussels (Perna perna) were deployed alongside the passive device within the South African marine environment for a 6week exposure period. Analysis of metal uptake (Cd, Cr, Cu, Pb and Zn) was determined by filtration and elution of the AM chelex resins, microwave digestion of the transplanted mussels, and determination of their metal concentrations by ICP-MS and ICP-OES analysis. Uptake patterns between the AM and transplanted mussels showed significant temporal and spatial correlation for the majority of the elements analysed. While the AM provided relevant and complementary information on the dissolved metal concentrations, limitations were also observed.

Mechanisms of enhanced mobilisation of trace metals by anionic surfactants in soil

Long-term applications of small concentrations of surfactants in soil via wastewater irrigation or pesticide application may enhance trace metal solubility. Mechanisms by which anionic surfactants (Aerosol 22, SDS and Biopower) affect trace metal solubility were assessed using batch, incubation and column experiments. In batch experiments on seven soils, the concentrations of Cu, Cd, Ni and Zn in the dissolved fraction of soils increased up to 100-fold at the high application rates, but increased less than 1.5-fold below the critical micelle concentration. Dissolved metal concentrations were less than 20% affected by surfactants in long-term incubations (70 days) up to the largest dose of 200 mg C kg −1 soil. Leaching soil columns with A22 (100–1000 mg C L −1) under unsaturated conditions increased trace metal concentrations in the leachates 2–4 fold over the control. Correlation analysis and speciation modelling showed that the increased solubility of metals upon surfactant application was more related to the solubilisation of soil organic matter from soil than to complexation of the metals with the surfactant. Organic matter from soil was solubilised in response to a decrease of solution Ca 2+ as a result of Ca–surfactant precipitation. At environmentally relevant concentrations, surfactant application is unlikely to have a significant effect on trace metal mobility.

Zinc and nickel removal in simulated limestone treatment of mining influenced water

Mining influenced water (MIW) is often characterized by low pH (acid mine drainage) and high dissolved metal concentrations. Treatment of MIW is often required to mitigate these two characteristics. One option, which has traditionally been used only for pH neutralization, is limestone based treatment systems. However, there is field evidence that limestone systems are also effective at removing metals such as Zn and Ni. These field systems are often too complex to examine specific removal hypotheses, while certain modes of laboratory examination are too simplistic to be applied to field settings. Instead, the batch reactors used here were intentionally more complex to allow for the examination of how certain variables (pH, alkalinity, and primary metal concentrations) interact to affect Zn and Ni removal. The data herein suggest that one possible removal process for Zn and Ni is through surface interactions on the precipitated primary metals Fe and Al. The specific processes are complex and conditional, and were found to depend on pH, alkalinity, and total amount of primary metal present. Indeed the complex interplay between these variables led to an observed local maximum in Zn removal that would not be predicted from traditional surface complexation theory or observed from simpler experimental systems.

Estuary-ria exchange of cadmium, lead and zinc in the coastal system of the Ria of Vigo (NW Iberian Peninsula)

Little research has been done on the land-sea exchange of trace elements, which is particularly applicable to ria coasts. In particular, trace metal enrichment in the inner part of the Ria of Vigo (the San Simon Inlet) has been observed from sediment studies but there is no information about Cd, Pb and Zn fluxes through the Rande Strait, which is the natural boundary of the estuary-ria water exchange. In order to assess metal exchanges in a ria-type system, six sampling cruises on board the R/V Mytilus (IIM-CSIC) were carried out. Water column profiles of salinity, temperature and tidal currents were obtained every 30 min. The water column for dissolved and particulate metals was sampled every two hours over a complete tidal cycle. Dissolved metal concentrations were 0.01–0.18 nM for Cd, 0.5-1.9 nM for Pb and 4-44 nM for Zn. Compared with Zn (16±12%) and especially with Cd (5.4±5.0%), particulate metal represented a significant fraction of the total concentration for Pb (41±21%). Net fluxes of dissolved Cd and Zn are higher than in the particulate phase, whereas for Pb an inverse situation was observed. The net metal exchange in the Vigo estuary-ria environment was not seasonally controlled. Dissolved Cd and Pb were driven by tidal ranges and particulate Pb by the Oitaven River flow. On the other hand, Zn did not show a defined trend. The budgets obtained for the Ria of Vigo, with the exception of Pb, were one or two orders of magnitude lower than those measured in other large European estuaries.

Dissolved and particulate metals in water from Sonora Coast: a pristine zone of Gulf of California

The purpose of this study was to investigate the distribution of metals (Cd, Pb, Hg, Cu, Fe, Mn, and Zn) in dissolved and particulate fractions in seawater from Bacochibampo Bay, Northern part of Mexico. Water samples were collected from November 2004 to October 2005. Metal analysis was done by graphite furnace atomic absorption spectroscopy. Results indicated highest concentrations of dissolved Cd and Zn in the sites localized at the mouth and center of the bay. During summer and spring, the highest levels of Cd, Mn, and Fe were detected, Zn in fall, and Pb and Cu in winter and spring. Mercury was the only metal that was not found in this fraction. In particulate fraction, Fe, Hg, and Mn were the most abundant elements in all the sampling sites, followed by Zn, Cu, Pb, and Cd. The highest levels of the majority of the metals were observed in the coastline, suggesting a continental and/or urban source for these chemicals. The highest level of Cd was detected during the summer and the rest of the metals in the fall. Statistically significant correlations were observed between dissolved and particulate forms of Pb:Mn, Cu:Fe, and Cu:Mn. The mean partition coefficient values were as follows: Fe>Mn>Cu>Pb>Cd>Zn. All dissolved metal concentrations found, except Pb, were lower than EPA-recommended water quality values. The levels of dissolved metals in this study reveal low bioavailability and toxic potential. However, further toxicological and sediment chemistry studies in this area are needed for a full risk assessment.

Variability of Stockton Coal Mine drainage chemistry and its treatment potential with biogeochemical reactors

Thirteen acid mine drainage seeps emanating from waste rock dumps and associated sediment ponds were monitored at Stockton Coal Mine near Westport, New Zealand to identify and quantify metal loads and delineate their spatial and temporal variability. Dissolved metal concentrations ranged from 0.05–1430 mg/L Fe, 0.200–627 mg/L Al, 0.0024–0.594 mg/L Cu, 0.0052–4.21 mg/L Ni, 0.019–18.8 mg/L Zn, <0.00005–0.0232 mg/L Cd, 0.0007–0.0028 mg/L Pb, <0.001–0.154 mg/L As and 0.103–29.3 mg/L Mn and the pH ranged from 2.04–4.31. Currently this acid mine drainage is treated further downstream by a number of water treatment plants employing a combination of ultra fine limestone and Ca(OH)2. However, in the interest of assessing more cost-effective technologies, biogeochemical reactors were assessed in the laboratory as potential cost-effective passive treatment options. Results of mesocosm-scale treatability tests showed that biogeochemical reactors incorporating mussel shells, pine bark, wood fragments (post peel) and compost increased pH to >6.7 and sequestered ≥98.2% of the metal load from the Manchester Seep located within the Mangatini Catchment. Laboratory results demonstrated that the maximum loading rate was 0.8 mol total metals/m3 substrate, and an average of 20.0 kg/day (7.30 tonnes/year) of metals could be removed by appropriately sized biogeochemical reactors.

Heavy metals: confounding factors in the response of New Zealand freshwater fish assemblages to natural and anthropogenic acidity

Acidification of freshwaters is a global phenomenon, occurring both through natural leaching of organic acids and through human activities from industrial emissions and mining. The West Coast of the South Island, New Zealand, has both naturally acidic and acid mine drainage (AMD) streams enabling us to investigate the response of fish communities to a gradient of acidity in the presence and absence of additional stressors such as elevated concentrations of heavy metals. We surveyed a total of 42 streams ranging from highly acidic (pH 3.1) and high in heavy metals (10 mg L − 1 Fe; 38 mg L − 1 Al) to circum-neutral (pH 8.1) and low in metals (0.02 mg L − 1 Fe; 0.05 mg L − 1 Al). Marked differences in pH and metal tolerances were observed among the 15 species that we recorded. Five Galaxias species, Anguilla dieffenbachii and A nguilla australis were found in more acidic waters (pH< 5), while bluegill bullies ( Gobiomorphus hubbsi) and torrentfish ( Cheimarrichthys fosteri) were least tolerant of low pH (minimum pH 6.2 and 5.5, respectively). Surprisingly, the strongest physicochemical predictor of fish diversity, density and biomass was dissolved metal concentrations (Fe, Al, Zn, Mn and Ni) rather than pH. No fish were detected in streams with dissolved metal concentrations > 2.7 mg L − 1 and nine taxa were only found in streams with metal concentrations < 1 mg L − 1. The importance of heavy metals as critical drivers of fish communities has not been previously reported in New Zealand, although the mechanism of the metal effects warrants further study. Our findings indicate that any remediation of AMD streams which seeks to enable fish recolonisation should aim to improve water quality by raising pH above ≈ 4.5 and reducing concentrations of dissolved Al and Fe to < 1.0 mg L − 1.

Metals Removal from Stormwater by Commercial and Non‐Commercial Granular Activated Carbons

Removing dissolved metals from urban storMwater may be required to protect aquatic species in particular watersheds. This research examined the adsorption of zinc and copper on 12 granular activated carbons, of which six were obtained commercially and six were produced by thermal activation of agricultural byproducts in the laboratory. Batch studies were used to obtain single solute distribution coefficients at pH 7. Copper distribution coefficients were higher than those for zinc on each of the 12 adsorbents. Granular activated carbon (GAC) produced from nutshells was less effective than that produced from rice materials (straw and hulls). The rice-derived GACs had the highest zinc distribution coefficients, and the commercial GACs typically exhibited higher copper distribution coefficients. Distribution coefficients for zinc and copper typically were higher for the materials tested in this study than in previous research, possibly because of the lower dissolved metal concentrations used, which were chosen to represent highway stormwater. Adsorption isotherms were obtained for zinc and copper adsorption on one commercial GAC and on activated rice hulls in buffered laboratory water and in highway stormwater. The constituents in stormwater caused a reduction in sorption of zinc and copper of up to 80%. The results suggest that 1 kg of activated rice hulls could treat up to 7 m3 of stormwater for zinc or 46 m3 of copper before exhaustion at the 90th percentile dissolved concentrations in California highway stormwater. The higher stormwater concentration and lower GAC affinity of zinc means that this constituent typically will limit adsorption system design for removal of multiple metals from stormwater.

Suitability of Daphnia similis as an alternative organism in ecotoxicological tests: implications for metal toxicity

The acute toxicity of metals to Daphnia similis was determined and compared to other daphnid species to evaluate the suitability of this organism in ecotoxicology bioassays. To verify the performance D. similis in toxicity tests, we also investigated the effect of Pseudokirchneriella subcapitata at 1 x 10(5) and 1 x 10(6) cells ml(-1) on Cd and Cr acute toxicity to the cladoceran. Daphnid neonates were exposed to a range of chromium and cadmium concentrations in the absence and presence of the algal cells. Metal speciation calculations using MINEQL(+) showed that total dissolved metal concentrations in zooplankton culture corresponded to 96.2% free Cd and 100% free Cr concentrations. Initial total dissolved metal concentrations were used for 48 h-LC(50) determination. LC(50) for D. similis was 5.15 x 10(-7) mol l(-1) dissolved Cd without algal cells, whereas with 1 x 10(5) cells ml(-1), it was significantly higher (7.15 x 10(-7) mol l(-1) dissolved Cd). For Cr, the 48 h-LC(50) value of 9.17 x 10(-7) mol l(-1) obtained for the cladoceran in tests with 1 x 10(6) cells ml(-1) of P. subcapitata was also significantly higher than that obtained in tests without algal cells (5.28 x 10(-7) mol l(-1) dissolved Cr). The presence of algal cells reduced the toxicity of metals to D. similis, as observed in other studies that investigated the effects of food on metal toxicity to standard cladocerans. Comparing our results to those of literature, we observed that D. similis is as sensitive to metals as other standardized Daphnia species and may serve as a potential test species in ecotoxicological evaluations.

Metal and metallothionein content in bullfrogs: Study of a whole watershed impacted by agricultural activities

Among the various anthropogenic activities potentially affecting amphibian populations, agriculture has often been evoked. Fertilizers used in agriculture are documented sources of metals that may contaminate nearby rivers. Bullfrogs ( Rana catesbeiana) were collected within the Yamaska River basin (Quebec, Canada) along a gradient of agricultural land use intensity. Hepatic, renal and intestinal metal content, along with hepatic metallothionein content, were determined. In general, dissolved metal concentrations and accumulated metal concentrations in bullfrogs varied little among sites. Hepatic Cu and Zn concentrations were significantly different among subwatersheds and were in accordance with the gradient in agricultural activities in at least one of the three years studied. Liver metallothionein content did not vary significantly among the subwatersheds, but they were correlated with Cu content within two sites and Cd content at one site. We conclude that R. catesbeiana could be used as a biomonitor for Cu contamination and potentially for other metals.

Spatial variability of cadmium, copper, manganese, nickel and zinc in the Port Curtis Estuary, Queensland, Australia

Port Curtis is a rapidly growing industrialised and urbanised harbour in Central Queensland, Australia. The spatial variability of trace metals in waters and suspended particulates was determined along axial transects within the harbour and in oceanic waters adjacent to Port Curtis. Dissolved metal concentrations were significantly elevated in Port Curtis compared with the concentrations measured in the adjacent coastal waters. Dissolved copper and zinc concentrations ranged from &lt;19 to 800 and &lt;31 to 580 ng L–1, respectively, and maxima were observed in inner harbour waters adjacent to the southern entrance to the Narrows and in close proximity to anthropogenic sources. Dissolved nickel concentrations were measured in the range of 110 to 900 ng L–1, and exhibited a maximum concentration in the central to northern Narrows, in an area that was not adjacent to anthropogenic sources. Dissolved manganese concentration maxima were measured in close proximity to the dissolved nickel maxima. It appears likely that the elevated dissolved metal concentrations in Port Curtis and the Narrows were not caused by a single point source, and are the result of several factors, including industrial activity around the foreshore, fluxes from sediment-porewater, low flushing durations, lower water pH and possibly episodic inputs from adjacent rivers.