A comparison of five rapid direct toxicity assessment methods to determine toxicity of pollutants to activated sludge

Five rapid direct toxicity assessment methods were used in three European partner countries to determine the toxicity of single toxicants, mixed toxicants and real industrial wastes. The final aim was to protect microbial degradation of organic wastes in biological treatment processes and hence enhance the quality of treated effluents to be discharged to the environment. Nitrification inhibition, Respirometry, Adenosine triphosphate luminescence and Enzyme inhibition were tested utilising activated sludge as the testing matrix. The Vibrio fischeri toxicity test was used as a surrogate to compare the various microbial bioassays. The IC50 (toxicant concentration eliciting a 50% inhibitory effect) was determined for a number of pollutants including single toxicants Cd, Cr, Cu, Zn, 3,5-dichlorophenol, toluene and linear alkylbenzenesulphonate (LAS); a standard mixture of metals and LAS; a standard mixture of organics and LAS, and 16 industrial effluents. The V. fischeri bioassay was also chosen in order to assess quality control of toxicant preparation during testing in the different laboratories of the partner countries. Comparisons of sensitivity, cost of implementation, cost per test, relevance, and ease of use were made. The most sensitive bioassays were V. fischeri and Nitrification inhibition, however, this depended in the main on the pollutant and mixtures tested. It is recommended that during assessment of wastewater toxicity a suite of tests be used rather than reliance on one particular test.     

Age-dependent accumulation of heavy metals in a pod of killer whales (Orcinus orca) stranded in the northern area of Japan

Mercury (Hg), cadmium (Cd), iron (Fe) manganese (Mn), zinc (Zn) and copper (Cu) concentrations in the liver, kidney and muscle of nine killer whales (including three calves) that stranded together in the northern area of Japan were determined. The Hg and Cd concentrations were found at trace levels in the calf organs, and increased with age. The Fe concentration in the muscle was significantly lower in the calves than in the mature whales and also increased with age. In contrast, Mn and Cu concentrations in the muscle were significantly higher in the calves than in the mature whales, and changes in the Zn concentration relative to age were unclear. These results suggest minimal mother-to-calf transfer of the toxic metals Hg and Cd and accumulation of these metals in the organs with age, while the essential metals Mn and Cu were found at higher concentrations in the muscle of calves than in mature whales.     

Influence of glyphosate and its formulation (Roundup) on the toxicity and bioavailability of metals to Ceriodaphnia dubia

This study examined the toxicological interaction between glyphosate (or its formulation, Roundup) and several heavy metals to a freshwater cladoceran, Ceriodaphnia dubia. We demonstrated that all binary combinations of Roundup and metals (Cd, Cu, Cr, Ni, Pb, Se and Zn) exhibited "less than additive" mixture toxicity, with 48-h LC50 toxic unit > 1. Addition of glyphosate alone could significantly reduce the acute toxicity of Ag, Cd, Cr, Cu, Ni, Pb and Zn (but not Hg and Se). The ratio between glyphosate and metal ions was important in determining the mitigation of metal toxicity by glyphosate. A bioaccumulation study showed that in the presence of glyphosate the uptake of some metals (e.g. Ag) was halted but that of others (e.g. Hg) was increased significantly. Therefore, our study strongly suggests that glyphosate and its commercial formulations can control the toxicity as well as the bioavailability of heavy metals in aquatic ecosystems where both groups of chemicals can co-occur.     

Modification of trace metal accumulation in the green mussel Perna viridis by exposure to Ag, Cu, and Zn

To examine the Cd, Hg, Ag, and Zn accumulation in the green mussel Perna viridis affected by previous exposure to Cu, Ag, or Zn, the dietary metal assimilation efficiency (AE) and the uptake rate from the dissolved phase were quantified. The mussel's filtration rate, metallothionein (MT) concentration, and metal tissue burden as well as the metal subcellular partitioning were also determined to illustrate the potential mechanisms underlying the influences caused by one metal pre-exposure on the bioaccumulation of the other metals. The green mussels were pre-exposed to Cu, Ag, or Zn for different periods (1-5 weeks) and the bioaccumulation of Cd, Hg, Ag, and Zn were concurrently determined. Pre-exposure to the three metals did not result in any significant increase in MT concentration in the green mussels. Ag concentration in the insoluble fraction increased with increasing Ag exposure period and Ag ambient concentration. Our data indicated that Cd assimilation were not influenced by the mussel's pre-exposure to the three metals (Cu, Ag, and Zn), but its dissolved uptake was depressed by Ag and Zn exposure. Although Hg assimilation from food was not affected by the metal pre-exposure, its influx rate from solution was generally inhibited by the exposure to Cu, Ag, and Zn. Ag bioaccumulation was affected the most obviously, in which its AE increased with increasing Ag tissue concentration, and its dissolved uptake decreased with increasing tissue concentrations of Ag and Cu. As an essential metal, Zn bioaccumulation remained relatively stable following the metal pre-exposure, suggesting the regulatory ability of Zn uptake in the mussels. Zn AE was not affected by metal pre-exposure, but its dissolved uptake was depressed by Ag and Zn pre-exposure. All these results indicated that the influences of one metal pre-exposure on the bioaccumulation of other metals were metal-specific due to the differential binding and toxicity of metals to the mussels. Such factors should be considered in using metal concentrations in mussel's soft tissues to evaluate the metal pollution in coastal waters.     

Characterization of heavy metal concentrations in the sediments of three freshwater rivers in Huludao City, Northeast China

Wuli River, Cishan River, and Lianshan River are three freshwater rivers flowing through Huludao City, in a region of northeast China strongly affected by industrialization. Contamination assessment has never been conducted in a comprehensive way. For the first time, the contamination of three rivers impacted by different sources in the same city was compared. This work investigated the distribution and sources of Hg, Pb, Cd, Zn and Cu in the surface sediments of Wuli River, Cishan River, and Lianshan River, and assessed heavy metal toxicity risk with the application of two different sets of Sediment Quality Guideline (SQG) indices (effect range low/effect range median values, ERL/ERM; and threshold effect level/probable effect level, TEL/PEL). Furthermore, this study used a toxic unit approach to compare and gauge the individual and combined metal contamination for Hg, Pb, Cd, Zn and Cu. Results showed that Hg contamination in the sediments of Wuli River originated from previous sediment contamination of the chlor-alkali producing industry, and Pb, Cd, Zn and Cu contamination was mainly derived from atmospheric deposition and unknown small pollution sources. Heavy metal contamination to Cishan River sediments was mainly derived from Huludao Zinc Plant, while atmospheric deposition, sewage wastewater and unknown small pollution were the primary sources for Lianshan River. The potential acute toxicity in sediment of Wuli River may be primarily due to Hg contamination. Hg is the major toxicity contributor, accounting for 53.3-93.2%, 7.9-54.9% to total toxicity in Wuli River and Lianshan River, respectively, followed by Cd. In Cishan River, Cd is the major sediment toxicity contributor, however, accounting for 63.2-66.9% of total toxicity.     

The effects of multiple metal contamination on ectomycorrhizal Scots pine (Pinus sylvestris) seedlings

Experiments were conducted to investigate the effects of single and multiple metal contamination (Cd, Pb, Zn, Sb, Cu) on Scots pine seedlings colonised by ectomycorrhizal (ECM) fungi from natural soil inoculum. Seedlings were grown in either contaminated field soil from the site of a chemical accident, soils amended with five metals contaminating the site, or in soil from an uncontaminated control site. Although contaminated and metal-amended soil significantly inhibited root and shoot growth of the Scots pine seedlings, total root tip density was not affected. Of the five metals tested in amended soils, Cd was the most toxic to ECM Scots pine. Field-contaminated soil had a toxic effect on ECM fungi associated with Scots pine seedlings and caused shifts in ECM species composition on ECM seedlings. When compared to soils amended with only one metal, soils amended with a combination of all five metals tested had lower relative toxicity and less accumulation of Pb, Zn and Sb into seedlings. This would indicate that the toxicity of multiple metal contamination cannot be predicted from the individual toxicity of the metals investigated.     

南京大气细粒子中重金属污染特征及来源解析

利用2011年1月、4月、7月和10月在南京市区和北郊采集的气溶胶样品,研究了南京大气细粒子中zn、Ph、Hg、As和cd5种重金属的污染水平,通过元素相关性分析和因子分析方法,对细粒子中这些重金属的污染来源进行了初步解析。结果表明,南京大气细粒子及其重金属污染严重,北郊普遍比市区严重;As严重超标,cd在南京北郊超标约5倍,zn在市区与北郊的质量浓度均高于其他重金属元素。每种重金属的浓度均随季节而变化。市区细粒子中,As和zn可能主要与燃煤、轮胎灰尘和建筑扬尘等有关,Pb、Hg和cd主要来自交通尘、城市垃圾焚烧等。北郊细粒子中,As、Hg和zn主要来源于燃煤、钢铁冶炼等工业,Pb和cd主要与农作物秸秆燃烧、汽车尾气、道路扬尘等影响有关。     

南京大气细粒子中重金属污染特征及来源解析简

利用2011年1月、4月、7月和10月在南京市区和北郊采集的气溶胶样品,研究了南京大气细粒子中Zn、Pb、Hg、As和Cd 5种重金属的污染水平,通过元素相关性分析和因子分析方法,对细粒子中这些重金属的污染来源进行了初步解析。结果表明,南京大气细粒子及其重金属污染严重,北郊普遍比市区严重;As严重超标,Cd在南京北郊超标约5倍,Zn在市区与北郊的质量浓度均高于其他重金属元素。每种重金属的浓度均随季节而变化。市区细粒子中,As和Zn可能主要与燃煤、轮胎灰尘和建筑扬尘等有关,Pb、Hg和Cd主要来自交通尘、城市垃圾焚烧等。北郊细粒子中,As、Hg和Zn主要来源于燃煤、钢铁冶炼等工业,Pb和Cd主要与农作物秸秆燃烧、汽车尾气、道路扬尘等影响有关。     

Frozen mitochondria as rapid water quality bioassay

A rapid and relatively low cost bioassay, usable in routine screening water test has been developed modifying the beef heart mitochondria test. In our experiments, mitochondria (FM22) were frozen at -22 degrees C, instead of -80 degrees C (FM80), and their applicability and sensitivity was verified. The oxygen consumption was measured by a Clark electrode that was interfaced to a PC to collect test analysis data. Blank tests were carried out to verify the oxygen consumption linear fitting. Toxicity tests were performed using pure organic and inorganic compounds, such to verify the FM22 sensitivity. A piecewise regression, through an Excel Macro, identified the break-point in the oxygen consumption and calculated the toxicity. The IC50s of the tested compounds were calculated and ranged from 0.123 to 0.173 mg/l for heavy metals (Cd, Cr, Cu, Ni, Pb and Zn) and from 0.572 to 10.545 mg/l for organics (benzene, DMSO, DDE, endrin, dichloromethane, chlorobenzene, 1,2-dichlorobenzene and 1,3-dichlorobenzene). Water effluent samples were then tested. The FM22 gave different toxic reactions to them. Water samples were characterised for heavy metals. The FM22 bioassay had a higher sensitivity than the FM80 and a high reproducibility in the toxicity test with pure compounds. The FM22 test was a good predictor of toxicity for water samples; the bioassay is easy, low cost and rapid, then usable for routine tests.     

Toxicity and bioaccumulation of thallium in Hyalella azteca, with comparison to other metals and prediction of environmental impact

Thallium (Tl) is an extremely toxic but little studied metal. For Hyalella azteca exposed in Lake Ontario water, a 25% reduction in survival (the LC25) occurred at about 48 nmol litre(-1) after 4 weeks. Body concentrations of Tl, which were proportional to water concentrations, averaged 290 nmol g(-1) dry mass at the LC25. Growth was reduced at slightly lower concentrations. Concentrations affecting reproduction were variable at < 50% of the LC25. On a water-concentration basis Tl was more toxic than Ni, Cu or Zn, but less toxic than Cd or Hg to Hyalella; toxicity to Pb was similar. On a body-concentration basis, the toxicities of Tl, Cd, Hg and Pb were all similar. Unlike Cd, Tl toxicity and uptake was affected by K concentrations in the water, and not by Ca, Mg, Na or other ions. Toxicity was proportional to uptake, and body concentrations were better predictors of toxicity than water concentrations in media with varying K concentrations. Preliminary measurements of Tl and Cd uptake by Hyalella from Hamilton Harbour and Lake Ontario sediments suggested that total bioavailable metal concentrations were greater in deep-water sediments from Lake Ontario than in sediments from the harbour. The ratio of bioavailable metal to the toxic threshold was slightly higher for Cd than for Tl, but well below 1 for both metals.     

Accumulation of heavy metals in the mole in Finland

Metal concentrations (Cu, Ni, Zn, Cd, Cr, Hg, Pb and Mo) were analysed from the liver and kidneys of moles, Talpa europaea L. (Insectivora), trapped in southern Finland on both contaminated and rural areas. In rural areas the concentrations of Cd, Cu, Zn, Pb and Mo were lower in juveniles (individuals in their first summer), except for Zn in the liver, which was lower in adults. When the animals were divided into annual classes (0-6 years), Cd and Mo concentrations in the liver increased significantly with age, while concentrations of Cu, Zn and Cr tended to decrease. Female moles had higher Pb concentrations than males, especially adult females, which also had lower levels of Cu in the liver than adult males. Moles in the metropolitan area of Helsinki clearly differed from those in rural areas in that the concentrations of heavy metals in these moles were higher (especially for the most toxic metals: Cd, Pb and Hg), and their body weight was lower. The renal concentrations of Cd in most of the moles in Helsinki exceeded the threshold that has been shown to have a nephrotoxic effect in mammals. In one subsample from Helsinki, Pb and Zn concentrations in the mole liver decreased as the distance from the highway increased. Concentrations of Pb in earthworms and several heavy metals in soil also decreased similarly in the same area. Our data indicate that Pb accumulates in moles through their diet of earthworms.     

Heavy metal toxicity to Lemna minor: studies on the time dependence of growth inhibition and the recovery after exposure

Environmental concentrations of toxic substances are not necessarily constant but fluctuate over time. Periods of intense exposure might be followed by episodes with a relatively low or no exposure, in principle allowing exposed organisms to recover from toxic injury. The growth reproduction assay with the limnic vascular plant Lemna minor allows for convenient studies on the time dependence of the aquatic toxicity of chemicals. Here we report on a study with four priority metals (Zn, Cu, Ni, Cd). Aims of the study were to determine the impact of the exposure duration on the observed toxicities and to determine the potential for recovery. The bioconcentrations of the test metals were recorded during the exposure in order to analyse, whether changes in the internal concentrations are a governing factor for the dynamics of toxicity. After an exposure of 7 days, Cd and Cu showed the highest toxicity to Lemna (EC50's of 1.9 and 9.7 microM respectively), while Ni and Zn had a slightly lower toxicity (EC50's of 56.3 and 46.1 microM respectively). Additionally, Zn showed a severely delayed toxicity and the exposed plants did not recover even 7 days after the exposure had ended. This is in sharp contrast to the other test metals, for which a considerable recovery was observed. These results indicate the necessity to more thoroughly consider the dynamics of toxicity, instead of recording toxic effects only after a constant exposure over a fixed time.     

Threat of heavy metal pollution in halophytic and mangrove plants of Tamil Nadu, India

Mangrove and halophytic plants occur along the coastal areas of Tamil Nadu, south India and these plants have been used in traditional medicine for centuries. Heavy metals are known to pose a potential threat to terrestrial and aquatic biota. However, little is known on the toxic levels of heavy metals found in mangrove and halophytic plants that are used in traditional medicine in India. To understand heavy metal toxicity, we investigated the bioconcentration factors (BCF) of heavy metals in leaves collected from eight mangroves and five halophytes in the protected Pichavaram mangrove forest reserve in Tamil Nadu State, south India. Data presented in this paper describe the impact of essential (Cu, Fe, Mg, Mn and Zn) and non-essential/environmentally toxic trace metals (Hg, Pb and Sn) in mangrove and halophytic medicinal plants. The concentrations of Pb among 13 plant species were higher than the normal range of contamination reported for plants. The average concentration of Hg in the halophytic plants (0.43+/-0.37mug/g) was seven times higher than mangrove plants (0.06+/-0.03mug/g) and it indicated pollutants from industrial sources affecting halophytes more than mangroves.     

Optimisation of a microbial bioassay for contaminated soil monitoring: bacterial inoculum standardisation and comparison with Microtox assay

This work represents the first step to set up a toxicity testing procedure and to evaluate the sensitivity of the test microorganism to several classes of environmental pollutants. First, three different techniques were employed to standardise the microbial inoculum, then two different toxicity assessment protocols have been compared: Microtox and a dehydrogenase (DHase) activity inhibition test. The main goal was the optimisation of a microbial bioassay based on the dehydrogenase activity (DHase) inhibition in Pseudomonas fluorescens bacterial strain ATCC 13525. Triphenyl tetrazolium chloride (TTC) was used as electron acceptor and its reduction produces Triphenyl formazane (TPF). The P. fluorescens DHase inhibition bioassay was investigated for being a reliable and rapid method for assessing toxicity. The optimisation of the operating conditions resulted in a repeatable bioassay. Then, P. fluorescens and Vibrio fischeri sensitivity were firstly compared by testing Zn++, one of the reference compounds for Microtox test. In addition, other compounds (Ni++, Cd++, Cu++, phenol) were also tested with both bioassays. A high statistical significance of data was obtained with the logistic curve. The present work has demonstrated that P. fluorescens is as sensitive as Microtox culture (V. fischeri), for some of the metal ions. With reference to organic compounds, the lower sensitivity of P. fluorescens to phenol makes its use difficult in organic polluted samples.     

Ecotoxicological assessment for receiving waters with the premetamorphic tadpoles acute assay

The toxicity of receiving waters was evaluated by means of the young tadpoles assays. The sentinel organism was Bufo arenarum, an indigenous anuran species. The assayed water samples were taken from a highly polluted urban watercourse (Reconquista River, Buenos Aires, Argentina), characterized by high concentration of nitrites, phosphates and heavy metals. The toxicity of water samples was assessed performing the pass-fail test and by means of the NOEC and LC(50); TUs (toxic units) were also calculated. The effect of the addition of a positive control (Cd) on the toxicity of the river water samples was also examined. Water samples of three sites, characterised by their different degree of pollution, were assayed. The lethal response had a clear cut correspondence with the water quality of the sample evaluated by means of physicochemical parameters. In most cases, the dilution of the samples resulted in a significant reduction of their toxicity to TU values compatible to those stated by the USEPA for industrial effluents. It was concluded that (a) the used Bufo arenarum bioassay was an adequate method for assessing the toxicity of natural polluted water samples and (b) the three considered endpoints showed no important differences after 48 or 96 h of exposure, therefore we concluded that it may not be necessary to extend the assay for a longer period than 48 h.     

P and trace metal contents in biomaterials, soils, sediments and plants in colony of red-footed booby (Sula sula) in the Dongdao Island of South China Sea

Concentrations of P and trace metals Zn, Cu, Cd, Pb and Hg in the faeces, bones, eggshells and feathers of seabirds and in the plants, soils and sediments with and without seabird influence on Dongdao Island, South China Sea, were determined and analyzed. Among the seabird biomaterials, the levels of P, Zn, Cu and Cd are the highest in the droppings and several times those in other materials; the Hg concentration is the highest in the feathers; and the Pb content is comparable among these biomaterials. These marked differences indicate different intake-bioaccumulation-elimination pathways for different trace metals. The levels of P, Zn, Cu, Cd and Hg in the plant, soil and sediment samples with the influence of seabird droppings are significantly higher than those in the samples without, and they are significantly correlated with each other. Thus, P, Zn, Cu, Cd and Hg are very likely to have a common source-predominantly bird guano-and the faeces of red-footed booby is an important vector for the flux of nutrient phosphorus and trace metals Zn, Cu, Cd and Hg from marine to island ecosystems on Dongdao Island.     

Patterns of metals and arsenic poisoning in Vibrio fischeri bacteria

The Microtox bioassay was used to establish dose-response curves for some toxic elements in aqueous solutions, namely, Zn(II), Pb(II), Cu(II), Hg(II), Ag(I), Co(II), Cd(II), Cr(VI), As(V) and As(III). Experiments were carried out at either pH 6.0 or pH 7.0 to indicate that pH may influence the measured toxicity of some elements due to pH-related changes of their chemical speciation. EC20 values, which represent a measurable threshold of toxicity, were determined for each element and were found to rank as Pb(II)>Ag(I)>Hg(II) approximately Cu(II)>Zn(II)>As(V)>Cd(II) approximately Co(II)>As(III)>Cr(VI). These values were compared to the limit concentrations allowed in industrial wastewater according to the official regulations in Catalonia (Spain). It appears that the Microtox test is sensitive enough for detecting some of the tested elements with respect to official regulations of Catalonia (Spain) dealing with pollution control, with the exception of cadmium, mercury, arsenate, arsenite and chromate.     

Effects of heavy metals on the nitrogen metabolism of the aquatic moss Fontinalis antipyretica L. ex Hedw. A 15N tracer study

The assessment of pollution in aquatic systems necessitates an accurate indication of toxicity of heavy metals for organisms and ecosystems. We used the stable nitrogen isotope 15N to estimate the influence of the heavy metals Cd, Pb and Zn on the synthesis of nitrogen-containing fractions in the aquatic moss Fontinalis antipyretica. This method permits conclusions concerning inhibitory effects of these heavy metals on the assimilation of nitrogen and the biosynthesis of amino acids and proteins. The moss was exposed to metal concentrations of 25-500 microM over a period of 5-10 days. 15N abundance of exposed plants was compared with that of control plants. Similar to a loss of vitality determined using a fluorometric assay, a decrease of the 15N abundance in the N fractions of Fontinalis antipyretica was measured in dependence on the metal concentration. Nevertheless, the individual inhibition by the distinct metals was different, so that the following order of toxicity was derived: Cd > Pb > Zn.     

Evaluation of the toxicity of marine sediments and dredge spoils with the Microtox bioassay

The Microtox^R bioassay was used to evaluate the toxicity of sediment and dredge spoil elutriates from several potentially-contaminated sites in Mobile and Pascagoula Bays. Elutriates were prepared using either local seawater or distilled deionized water (osmotically adjusted with NaCl prior to testing), and Microtox^R assays were performed with the elutriates and three reference toxicants. There were marked differences in the toxicity of several elutriates and reference toxicants in the two different waters, with the seawater generally resulting in the same or lesser toxicity than the osmotically-adjusted distilled deionized water.     

重金属对活性污泥微生物毒性的比较研究

采用发光细菌毒性、活性污泥脱氢酶毒性、硝化抑制毒性3种方法测定Hg、Cd、Zn、Pb 4种重金属对活性污泥微生物的毒性,并对测定结果进行了比较.结果表明,发光细菌毒性测定方法的灵敏度最高,测得的重金属半数有效浓度(ECSO)最低,4种重金属对发光细菌发光强度的抑制程度由大到小顺序依次为Hg>Cd>Zn>Pb;活性污泥脱氢酶毒性和硝化抑制毒性的测定结果与发光细菌毒性测定结果相比,灵敏度相对较低,测得的重金属ECSO相对较高,测得的活性污泥脱氢酶活性的抑制程度由大到小顺序依次为Cd>Hg>Zn>Pb,与测得的活性污泥硝化速率抑制程度大小顺序一致.但2者测得的EC50有所差别.为了更准确的判定重金属对活性污泥微生物的毒性影响.至少应取不同的重金属毒性终点指示指标做一组毒性实验,而不能以发光细菌毒性测定结果作为唯一的判定依据,这可能会过分夸大重金属对污水处理工艺的冲击能力,导致污水处理成本无谓增加.