Bioaccumulation of heavy metals in two wet retention ponds

Metal accumulation in stormwater ponds may contaminate the inhabiting fauna, thus jeopardizing their ecosystem servicing function. We evaluated bioaccumulation of metals in natural fauna and caged mussel indicator organisms in two wet retention ponds. Mussel cages were distributed throughout the ponds to detect bioaccumulation gradients and obtain a time-integrated measure of metal bioavailability. We further investigated if sediment metal concentrations correlate with those in the fauna and mussels. Metal concentrations in the fauna tended to be higher in the ponds than in a reference lake, but statistical significance was only shown for Cu. Positive correlations were found for some metals in fauna and sediment. Sediment metal concentrations in one pond decreased from inlet to outlet while no gradients were observed in the mussels in either pond. These findings indicate that metal accumulation in the examined ponds currently does not pose a threat to their habitat function.     

Modification, calibration and verification of the IWA River Water Quality Model to simulate a pilot-scale high rate algal pond

We implemented the IWA River Water Quality Model No. 1 (Reichert et al., 2001. River Water Quality Model No. 1, IWA Scientific & Technical Report No. 12) to simulate water-quality characteristics in two pilot-scale High Rate Algal Ponds. Simulation results were compared with two years' of data from the ponds. The first year's data from one pond were used for model calibration; the remaining data were used for validation. As originally formulated and parameterized, the model consistently yielded summer-time algal biomass concentrations which were too low - with consequent failures in its reproduction of dissolved oxygen, pH and nutrient dynamics. We experimented with various structural/parametric changes to improve the model's performance. The most effective strategy was to greatly increase the respiratory losses suffered by the heterotrophic osmotrophs (thereby giving the algae access to a larger fraction of the incoming dissolved organic carbon and nitrogen). This suggests that CO₂-bubbling alone cannot entirely preclude resource-limitation of algal production. We doubt that our parameterization of heterotrophic osmotrophs is correct and infer that the algae derive a large fraction of their nutrition by direct osmotrophic uptake of dissolved organic matter. This inference is supported by the literature concerning the physiology of the dominant algal species in our ponds.     

The character of the suspended and dissolved phases in the water cover of the flooded mine tailings at Stekenjokk, northern Sweden

Studies of the suspended and dissolved phases of the pond water, material collected from sediment traps, and surficial sediments/tailings from the flooded tailings pond at Stekenjokk have been performed. The aim was to characterise the material, to study the seasonal variations and to quantify possible resuspension of the tailings in the pond. The element concentrations in the pond at Stekenjokk seem to be largely controlled by processes controlling the precipitation and dissolution of Mn- and Fe-oxyhydroxides in both the water column and in the surficial tailings. Physiochemical processes such as weathering of silicates on the surrounding mountain slopes or dykes contributes both dissolved elements and detrital particles. The suspended phase consists of detrital silicate material as well as Fe- and Mn-oxyhydroxides. The average heavy metal concentrations are high, e.g. 0.42% Cu, 0.15% Pb and 3.1% Zn, which is probably due to sorption onto Fe- and Mn-oxyhydroxides. The suspended phase is richer in Fe, and particularly Mn, during the winter. The suspended phase resembles the material collected in sediment traps and the material in the surficial sediments. The pond water is well mixed during the ice-free season. The dissolved heavy metal concentrations are generally rather low with, e.g. maximum concentrations of 2.03 micrograms/l Cu, 0.23 microgram/l Pb and 268 micrograms/l Zn during the winter. Higher dissolved concentrations are found below the ice-cover above the sediment surface during the winter, caused by diffusion of elements from the sediment-water interface up into the pond water. Most of the metals occurring in the pond are dissolved and resuspension of tailings is negligible.     

Influence of acid volatile sulfides and simultaneously extracted metals on the bioavailability and toxicity of a mixture of sediment-associated Cd, Ni, and Zn to polychaetes Neanthes arenaceodentata

Laboratory microcosm experiments were conducted to investigate the influence of acid volatile sulfides (AVS) and simultaneously extracted metals (SEM) in sediments on the bioavailability and toxicity of Cd, Ni, and Zn in sediments to polychaete worms Neanthes arenaceodentata. Cohorts of juvenile N. arenaceodentata were exposed to sediments spiked with metal mixtures containing Cd, Ni, and Zn (0.5-15 micromol x g(-1) of total SEM) with Low- (approximately 1 micromol x g(-1)), Medium- (approximately 5 micromol x g(-1)), and High-AVS concentrations (approximately 10 micromol x g(-1)) for 20 days to determine mortality, growth rate, and metal bioaccumulation. Tissue Cd and Zn concentrations at the end of the exposure were significantly higher in sediments with the low-AVS concentration at a given SEM concentration due to the increased dissolved metal concentrations in overlying water (OW). However, tissue Ni concentrations were not related to dissolved Ni in the OW. AVS concentrations also influenced the toxicity of metals to the worms. Significant mortality was observed only at the highest SEM treatments at Low-AVS series. Most individuals survived at the highest SEM treatments at Medium- and High-AVS series. Similarly, the growth rates of worms were reduced in treatments having higher molar differences between SEM and AVS ([SEM-AVS]). Overall, the bioavailability and toxicity of metals in sediments was not well predicted by sediment metal concentrations only, but considering the influence of geochemical factors (AVS) on the metal bioavailability improved the prediction of toxicity. Also, the relationship between tissue metal concentration and toxicity was used to determine which contaminant was most responsible for the observed toxicity of the metal mixture.     

Preliminary Analysis Of Heavy Metals In The Kahrizak Landfill Leachate: A Conceptual Approach

No data have been published on the leachate quality for the Kahrizak landfill site, including heavy metal concentrations. Therefore concentrations of Cu, Zn, Pb, Cd, Ni, Co, Fe and Mn were measured in four fresh and older leachate samples during a 10 months period. Conceptually, heavy metals can be considered to be present in three phases: ( a ) Dissolved; ( b ) adsorbed onto suspended solids; and ( c ) adsorbed onto the suspended solids with particle sizes less than 0.45 w m. A method is proposed in this paper to measure the concentrations of heavy metals in each of the three phases. Other samples were analyzed for phases ( a ) and ( b ). Fresh leachate samples with lower pH values had higher dissolved concentrations of heavy metals than the older leachate samples with higher pH values. Particulate heavy metal concentrations were slightly lower at higher pH values.     

某金矿尾矿库土壤重金属污染特征及来源分析

尾矿中含有的重金属通过介质向环境缓慢释放,重金属进入土壤后,会对周围土壤、生态环境造成影响,危害人类身体健康和安全。本文以某金矿尾矿库为研究对象,对尾矿库流域内土壤重金属进行取样调查,确定尾矿库及周边土壤重金属污染现状,分析重金属来源及污染特征。对尾矿库及周边的土壤进行pH、氰化物、锑、砷、镉、铜、铅、锌、汞等元素含量测试,采用单项污染指数与内梅罗指数法进行重金属污染程度分析与评价;同时运用主成分分析法,探究尾矿库及周边区域土壤重金属形成原因和污染特征。研究结果表明：尾矿库流域内地表土样处于重污染状态,污染区主要集中在尾矿库东北侧,污染范围较大;氰化物、锑、镉、铜、铅、锌存在着不同程度的相关性,表明研究区内存在这6种元素不同程度的复合污染或这些元素具有同源性,重金属污染主要来源为矿石开采和工业活动等人为来源;土壤中砷的吸附、迁移与土壤pH值关系密切。调查和分析尾矿库土壤污染情况,查明尾矿库污染形成原因和污染特征,对尾矿库的综合治理具有重要意义。     

Investigation of mangrove macroalgae as biomonitors of estuarine metal contamination

This study examined the potential use of macroalgae epiphytic on mangrove aerial roots as biomonitors of estuarine contamination. The metal concentrations of macroalgae were investigated in four estuaries in the vicinity of Sydney, Australia, and compared to water and sediment metal concentrations over three seasonal surveys. Macroalgal metal concentrations (copper, zinc, cadmium, chromium, lead, nickel, manganese and iron) appeared to be more associated with sediment metal concentrations than water concentrations, suggesting they may be useful biomonitors of estuarine sediment contamination. Algae in the more contaminated estuaries generally contained higher metal concentrations. However, concentrations of iron, nickel and manganese appeared to be similar in the algae despite the varying sediment concentrations, while accumulation of copper, zinc, lead and chromium appeared to be associated with ambient environmental concentrations. The uptake of metals also varied among the different species, suggesting that algal parameters, such as morphology, may also influence metal uptake and accumulation.     

Growth of blue-green algae in the Manukau (New Zealand) oxidation ponds—I. Growth potential of oxidation pond water and comparative optima for blue-green and green algal growth

Water sampled from the Manukau oxidation ponds between 6 December 1973 and 12 July 1974 was tested for its ability to support blue-green algal growth. A local blue-green algal isolate of Anabaena grew well on membrane filtered pond water throughout the year, however the unfiltered water sustained Anabaena only when the resident green algal populations, in particular Chlorella, were low.Temperature and pH optima for growth of Anabaena and the Manukau pond algal dominant, Chlorella, were found to be significantly different: 28–35°C and pH 9–10 and 23–28°C and pH 7–8 respectively. The ambient conditions of the ponds favoured growth of Chlorella over blue-green algae during the period of study.     

Derivation and application of a new model for heavy metal biosorption by algae

An equilibrium model for describing the relationships between important parameters for heavy metal sorption by algae was derived through a thermodynamics approach. In this model, both the removal efficiency of heavy metal and metal adsorption per unit algal biomass are considered to be simple functions of the ratio of algal biomass concentration to the initial metal concentration for selected conditions, i.e. as at constant pH and temperature. The model was found to fit the experimental results well (judged by the correlation-regression coefficient, R2), for the adsorption of cadmium, copper, lead and zinc by two algal species, Oocystis sp. (both living and non-living) and Chlorococcum sp. The applicability of the model was also supported by the reprocessed results of experimental data given in the literature, i.e. for the metal species, Cd, Pb, Cu and Ag, the algal species, Chlorella vulgaris, Scenedesmus quadricauda and Cladophora crispata, and both batch and continuous fixed-bed reactors. It was also demonstrated that the model could be applied over a broad range of pH for cadmium and copper adsorption by Oocystis sp. However, the model was not applicable at very low and high pH levels, due to negligible adsorption and precipitation, respectively.     

Distribution of micro-essential (Fe, Cu, Zn) and toxic (Hg) metals in tissues of two nutritionally distinct hydrothermal shrimps

Hydrothermal ecosystems of the Mid Atlantic Ridge (MAR) are dominated by shrimps and mussels that are naturally exposed to elevated levels of heavy metals providing unique in situ laboratories for ecotoxicological investigations. This study reports on the tissue compartmentalization of both micro-essential (Fe, Zn, Cu) and toxic metals (Hg) in two nutritionally distinct cariddean vent shrimps: Rimicaris exoculata and Mirocaris fortunata, in order to shed light on organism-biota interactions at hydrothermal vents. High metal concentrations in shrimps confirmed extreme exposure levels at both geochemically different hydrothermal vents (Rainbow and Lucky Strike). However, Hg concentrations were below those reported in species for human consumption that may either suggest low bioavailability of the metal, or its effective detoxification/depuration by the hydrothermal shrimp that needs to be confirmed by post-capture toxicological investigations. Distribution of metals in different tissues had very similar patterns in both shrimp species, the target organs being gill and pylorus. Tissue levels correlated well with end-member fluid composition with regard to element ratios, i.e. Fe/Zn and Fe/Cu ratios in end-member fluids reported for Rainbow and L. Strike were conserved in the gills of M. fortunata. Moreover, R. exoculata that lives closer to venting exits as compared to M. fortunata, had similar or often less metals accumulated in selected organs, possibly owing to its higher degree of adaptation to hydrothermal conditions. Despite of high concentrations in tissues micro essential metals only represented a small fraction (14-36%) of the whole body burden indicating preponderance of minerals on the surface and/or in the gut, and thus points to improper use of whole body concentration in metal bioavailability interpretations at hydrothermal vents.     

Modeling metal bioaccumulation in a deposit-feeding polychaete from labile sediment fractions and from pore water

Estuarine sediments are often highly enriched in particle-reactive metal contaminants and because aquatic animals have often been shown to acquire metals predominantly from their diet, benthic animals feeding on deposited or resuspended sediments may also accumulate metals through this uptake pathway. Laboratory experiments were performed in which the surface deposit-feeding polychaete, Nereis succinea, was exposed to As(+ 5), Cd, and Cr(+ 3) in pore water or in estuarine sediments with and without enrichment with algal debris. These experiments generated metal uptake parameters (assimilation efficiency of ingested metal [AE], uptake rate constant of dissolved metal, efflux rate constants following dietary or aqueous metal exposures) used in a kinetic model of metal bioaccumulation. The model showed that > 97% of the body burden of these metals is accumulated through ingested sediment. The kinetic model was further modified to consider the geochemical fractionation of the metals in the sediments because metals bound to some fractions were shown to be unavailable to these polychaetes. The modified model substituted the AE term for each metal by the percentage of metal extracted in neutral and weak acid exchangeable fractions (termed “carbonex” fraction) multiplied by the slope of the regression between the metal AE and its fractionation in carbonex. The modified model generated predictions of As, Cd, and Cr body burdens in polychaetes at three different estuarine sites that matched independent field observations at these sites (r² = 0.84 for sediments without organic enrichment, r² = 0.87 with organic enrichment). Model predictions that relied on total metal concentrations showed weaker relationships (r² = 0.11-0.50). This study adds to the evidence for the dominance of dietary uptake of metals in aquatic animals and identifies a key sedimentary fraction of metals that can account for bioavailability of sediment-bound metals.     

Growth of blue-green algae in the Manukau (New Zealand) oxidation ponds—II. Experimental studies on algal interaction

Water sampled from the Manukau oxidation ponds between 6 December 1973 and 12 July 1974 was tested for its ability to support blue-green algal growth. A local blue-green algal isolate of Anabaena grew well on membrane filtered pond water throughout the year, however the unfiltered water sustained Anabaena only when the resident green algal populations, in particular Chlorella, were low.Temperature and pH optima for growth of Anabaena and the Manukau pond algal dominant, Chlorella, were found to be significantly different: 28–35°C and pH 9–10 and 23–28°C and pH 7–8 respectively. The ambient conditions of the ponds favoured growth of Chlorella over blue-green algae during the period of study.     

Metal sorption to natural filter substrates for storm water treatment--column studies

Storm water generated from road runoff contains pollutants such as metals that are either dissolved in storm water or bound to particulates. Using detention ponds for the treatment of storm water from road runoff, where particles can settle, can reduce the level of particulate-bound metals in the water, while small particles and dissolved matter pass through the detention pond. Some of these metals can be removed by filtrating water through specially constructed filter systems. This investigation is a laboratory study where different filter substrates were tested in order to evaluate their efficiency in reducing heavy metals from water. Metal solutions were filtered through columns filled with various substrates consisting of combinations of calcium silicate rock (opoka), zeolite and peat. The metal-removal efficiency was correlated to hydraulic load, and for the metal species the reduction efficiency decreased with increased hydraulic load. Mixtures of opoka and zeolite were found to be superior to the other filter-substrate combinations tested with regard to both hydraulic aspects and removal efficiency. Peat mixed with the calcium silicate rock was not successful due to clogging which stopped the experiment. A manufactured product made from the calcium silicate rock (burned opoka) was found to be less useful because of its calcium oxide (CaO) content. Among the tested filter substrates, mixtures of opoka and zeolite seemed to be the most useful compositions with respect to reduction-efficiency and clogging aspects. The removal capacity of metals varied from 0.6 to 1.8 kg m(-3) depending on the metal and the filter substrate.     

A novel algal toxicity testing technique for assessing the toxicity of both metallic and organic toxicants

This study presents a closed-system algal toxicity test technique that is capable of detecting the effects of both organic and metallic toxicants. Toxicity testing was conducted by transferring adequate amounts of algal suspension, dilution water (with culture growth medium), and toxicants into 300-mL BOD bottles. The BOD bottles were completely filled up with no head-space left. The initial cell density and the exposure time were 15,000 cells/mL and 48 h, respectively. The performance of the above test method was evaluated using three heavy metals and six organic toxicants based on three different test endpoints, i.e., dissolved oxygen production, algal growth rate, and cell density. The proposed test revealed excellent test sensitivity and reproducibility. Currently, none of the existing algal toxicity test protocols is adequate for assessing the toxicity of organic chemicals. The closed-system algal toxicity tests developed by previous researchers also may not be ideal because the enlarged headspace and/or enriched bicarbonate buffer may result in either underestimations of the exposure concentrations or insensitive responses to both heavy metals and organic toxicants. Compared to the aforementioned algal toxicity test methods, the proposed technique in the present study has a more general applicability under conditions such as effluent samples containing both metals and organic toxicants or samples with unknown compositions.     

Some effects of stocking fish in waste treatment ponds

Oxidation ponds or sewage lagoons often present characteristics of natural water bodies in an extreme state of ecological imbalance. Excess nutrients of the decaying waste give rise to plankton blooms which subsequently die. In such conditions dissolved oxygen concentrations (DO) in the water are often low and the pH depressed. The addition of fish to ponds which twice a week received, per ha, wastes with a 5 day BOD of up to 800 kg (20°C) and 5600 kg solids, reduced plankton and benthic populations, increased the average DO, and raised the pH. All of these changes improve the effectiveness of a waste treatment pond for reducing BOD and removing nutrients from the water. Bacteria concentrations were as much as 15 times lower in treatment ponds stocked with fish as compared with unstocked ponds. Lower bacteria concentrations however reduced the rate of loss of COD in the solids of the waste.     

Do high levels of diffuse and chronic metal pollution in sediments of Rhine and Meuse floodplains affect structure and functioning of terrestrial ecosystems?

This paper (re)considers the question if chronic and diffuse heavy metal pollution (cadmium, copper, lead and zinc) affects the structure and functioning of terrestrial ecosystems of Biesbosch National Park, the floodplain area of rivers Meuse and Rhine. To reach this aim, we integrated the results of three projects on: 1. the origin, transfer and effects of heavy metals in a soil-plant-snail food chain; 2. the impact of bioavailability on effects of heavy metals on the structure and functioning of detritivorous communities; 3. the risk assessment of heavy metals for an herbivorous and a carnivorous small mammal food chain. Metal pollution levels of the Biesbosch floodplain soils are high. The bioavailability of metals in the soils is low, causing low metal levels in plant leaves. Despite this, metal concentrations in soil dwelling detritivores and in land snails at polluted locations are elevated in comparison to animals from 'non-polluted' reference sites. However, no adverse effects on ecosystem structure (species richness, density, biomass) and functioning (litter decomposition, leaf consumption, reproduction) have been found. Sediment metal pollution may pose a risk to the carnivorous small mammal food chain, in which earthworms with elevated metal concentrations are eaten by the common shrew. Additional measurements near an active metal smelter, however, show reduced leaf consumption rates and reduced reproduction by terrestrial snails, reflecting elevated metal bioavailability at this site. Since future management may also comprise reintroduction of tidal action in the Biesbosch area, changes in metal bioavailability, and as a consequence future ecosystem effects, cannot be excluded.     

Performance predictions of mature experimental constructed wetlands which treat urban water receiving high loads of lead and copper

The treatment efficiencies of vertical-flow wetland filters containing macrophytes and granular media of different adsorption capacities were investigated. Different concentrations of lead and copper sulphate were added to urban stream inflow water in order to simulate pre-treated (pH adjustment assumed) mine wastewater. After 1 year of operation, the metal mass load rate was increased by a factor of approximately 4.6. No breakthrough of metals was recorded. The use of macrophytes and adsorption media did not enhance heavy metal reduction significantly after 13 months of operation. A correlation analysis indicated strong positive correlations between conductivity on one side and other variables including temperature, total solids, dissolved oxygen and the redox potential on the other side. Some expensive or time-consuming variables (e.g., biochemical oxygen demand) can be predicted with less expensive ones (e.g., dissolved oxygen and temperature). The associated absolute mean errors were <10%.     

Influence of water and sediment quality on benthic biota in an acidified river

Water and sediment quality and benthic biota were investigated in all seasons during three years in the River Akagawa that receives the effluent from a mine drainage treatment plant at its upstream site. The upper reaches kept the low pH, the comparatively high concentrations of metals and a large amount of iron deposited on the riverbed. The predominant macroinvertebrates were Protonemura sp., Capnidae, Nemoura sp. and Chironomidae in the upper and middle reaches. In the lowest reaches, the community structure of the macroinvertebrate changed into Chironomidae, Trichoptera (Hydropsychidae) and Ephemeroptera (Baetis sp.) as the pH was increased. From the results of multivariate analyses, it was found that the restoration of pH and attached algae and the increase in the concentrations of nutrients and organic matter promoted the inhabitation of Chironomidae and Hydropsychidae, whereas the dissolved metals in the river water inhibited the inhabitation of these families. Moreover, the sedimentation of metals would cause a severe damage to the inhabitation of Hydropsychidae compared with that of Chironomidae.     

Diel changes in water chemistry in an arsenic-rich stream and treatment-pond system

Arsenic concentrations are elevated in surface waters of the Warm Springs Ponds Operable Unit (WSPOU), located at the head of the upper Clark Fork River Superfund site, Montana, USA. Arsenic is derived from historical deposition of smelter emissions (Mill and Willow Creeks) and historical mining and milling wastes (Silver Bow Creek). Although long-term monitoring has characterized the general seasonal and flow-related trends in As concentrations in these streams and the pond system used to treat Silver Bow Creek water, little is known about solubility controls and sorption processes that influence diel cycles in As concentrations. Diel (24-h) sampling was conducted in July 2004 and August 2005 at the outlet of the treatment ponds, at two locations along a nearby reconstructed stream channel that diverts tributary water around the ponds, and at Silver Bow Creek 2 km below the ponds. Dissolved As concentration increased up to 51% during the day at most of the stream sites, whereas little or no diel change was displayed at the treatment-pond outlet. The strong cycle in streams is explained by pH- and temperature-dependent sorption of As onto hydrous metal oxides or biofilms on the streambed. Concentrations of dissolved Ca(2+) and HCO(3)(-) at the stream sites showed a diel temporal pattern opposite to that of As, and geochemical modeling supports the hypothesis that the concentrations of Ca(2+) and HCO(3)(-) were controlled by precipitation of calcite during the warm afternoon hours when pH rose above 9.0. Nightly increases in dissolved Mn and Fe(II) concentrations were out of phase with concentrations of other divalent cations and are more likely explained by redox phenomena.     

A comparison of the non-essential elements cadmium, mercury, and lead found in fish and sediment from Alaska and California

Concentrations of three non-essential elements (cadmium (Cd), mercury (Hg), and lead (Pb)) were determined in sediment and fish from several locations in Alaska (AK) and California (CA) and used to examine differences in bioaccumulation within and between geographic locations. We analyzed tissue (liver, muscle, gill, and stomach contents) from white croaker (Genyonemus lineatus) and English sole (Pleuronectes vetulus) in California and flathead sole (Hippoglossoides elassodon) in Alaska, in addition to several species of invertebrates (mercury only). As found in previous work on arsenic (As) [Meador et al., 2004], Cd in fish liver exhibited a negative correlation with sediment concentrations. No such correlations were found for Hg and Pb when fish liver and sediment were compared; however, these metals did exhibit a positive relationship between liver and organic carbon normalized sediment concentrations, but only for the CA sites. Sediment concentrations of Hg at the AK sites were lower than those for the CA sites; however, AK invertebrates generally bioaccumulated more Hg than CA invertebrates. Conversely, Hg bioaccumulation was higher in CA fish. Even though ratios of total metal/acid volatile sulfides (AVS) in sediment were one to two orders of magnitude higher for the AK sites, bioaccumulation of these elements was much higher in fish from the CA sites. Bioaccumulation factors ([liver]/[sediment]) (BAFs) were highest at relatively clean sites (Bodega Bay and Monterey), indicating that elements were more bioavailable at these sites than from more contaminated locations. The observation of high BAFs for As in fish from Alaska and low BAFs for the California fish, but reversed for Cd, Hg, and Pb in this study, implies that differences in fish species are less important than the unique geochemical features at each site that control bioavailability and bioaccumulation and the potential sources for each element. Additionally, these data were also used to examine the metal depletion hypothesis, which describes the inverse relationship between elements and organic contaminants documented in some monitoring studies. Our results suggest that the enhanced bioavailability of the metals at some uncontaminated sites is the main determinant for the inverse correlation between metal and organic contaminants in tissue.