Screening of PAHs and DDTs in sand and acrisols soil by a rapid solid-phase microalgal bioassay

Previously we have demonstrated the rapid screening potential of a newly developed solid-phase microalgal bioassay with spiked sands. In this paper, we report further comparative results using both PAHs and DDTs spiked sands and field-collected acrisols soils. Toxicity responses obtained from standard higher plant tests with three species of plants (Lolium perenne, Cynodon dactylon and Brassica chinensis) were compared with those obtained from a cocktail of microalgae (Selenastrum capricornutum, Chlorococcum hypnosporum and the indigenous Chlorococcum meneghini). The 5-day seed germination/root elongation tests were not sensitive at all in contrast to the 4-day solid-phase microalgal tests and the 28-day early seedling growth tests in both spiked sands and contaminated soils. Sensitivities of microalgal tests were generally higher than the seedling growth tests in spiked sands. Concerning the assays with contaminated soil, the responses of microalgae and higher plants varied. However, the results demonstrated that microalgae could generally act as effective surrogates to screen xenobiotic compounds at toxic level to higher plants, with the local species C. meneghini especially sensitive to reveal phytotoxic effects. This promising rapid screening solution is possible to be used in accompany with standard seedling growth tests when assessing phytotoxicities of contaminated areas, especially for acrisols soil.     

Silver nanoparticles reduced the invasiveness of redroot pigweed

The differences in the growth performance between invasive species and native species might paly a key role in the effective invasion. The extensive use of silver nanoparticles (AgNPs) has created the concern of their release into environment. Thus, the possible effects of AgNPs on the growth performance of invading agents are critical to better illustrate the underlying mechanisms for effective invasion. This study aimed to assess the impacts of AgNPs with different concentrations [200 and 400 mg kg (soil)⁻¹] and particle sizes (30 and 70 nm) on the growth performance and competitive ability of well known invasive Amaranthus retroflexus L. (redroot pigweed) and native A. tricolor L. (red amaranth). It was observed that the growth characteristics and supporting ability of redroot pigweed were significantly lower than those of amaranth. Results of the relative competitive intensity index and the relative dominance index also revealed that redroot pigweed exhibited lower competitive ability compared to red amaranth, especially under AgNPs. It can be assumed that the poor growth performance and competitive ability of redroot pigweed might prevent its invasiveness under AgNPs. The supporting ability, leaf photosynthetic area, leaf growing ability, leaf resource use efficiency and acquisition capability, and growth competitiveness of the two plant species were found to be significantly reduced under AgNPs. AgNPs with 30 nm at 400 mg kg (soil)⁻¹ triggered more toxicity on the supporting ability and growth competitiveness of the two plant species than AgNPs with 30 nm at 200 mg kg (soil)⁻¹. In addition, AgNPs with 30 nm imparted high toxicity on the leaf growing ability of red amaranth than AgNPs with 70 nm. However, the particle size of AgNPs did not address significant effects on the growth performance of redroot pigweed. Ag⁺ solution exhibited stronger toxicity on the supporting ability and leaf growing ability of the two plant species than AgNPs.

     

Acute toxicity of the insecticide abamectin and the fungicide difenoconazole (individually and in mixture) to the tropical stingless bee Melipona scutellaris

Stingless bees have been recognized as essential plant pollinators and producers of various natural products in neotropical areas. Research into the potential risks of pesticides they may be exposed to in agricultural fields, however, remains meagre. Especially the toxicity of pesticide mixtures likely to occur under real-world conditions and that are likely to exert synergetic effects has been poorly studied. The aim of the present study was therefore to evaluate the single and mixture acute contact and oral toxicity of commercial products containing the insecticide abamectin and the fungicide difenoconazole in laboratory bioassays with the Brazilian native stingless bee Melipona scutellaris. In addition, a comparison of the insecticide sensitivity of stingless bees relative to the honeybee Apis mellifera was made based on previously published toxicity data. Except for oral exposure to abamectin, M. scutellaris appeared to be more sensitive that A. mellifera in the single compound toxicity tests. A difenoconazole concentration at the NOEC (no observed effect concentration) level indicated a synergetic toxic interaction with abamectin. A sensitivity comparison based on published toxicity data for A. mellifera and stingless bees indicated several insecticidal modes of action having a high relative sensitivity to stingless bees that need especial consideration in future studies. The research findings highlight the need for testing native bee species and environmentally relevant pesticide mixtures in risk assessments to avoid underestimation of potential risks to bee populations and the subsequent loss of pollination ecosystem services.

     

Acute toxicity of the insecticide methyl parathion and its hydrolytic product p-nitrophenol to the native Australian cladoceran Daphnia carinata

The toxicity of an organophosphorus (OP) insecticide, methyl parathion (MP), and its hydrolysis product, p-nitrophenol (PNP), to the native Australian cladoceran species, Daphnia carinata, was assessed. Both MP and PNP were stable in cladoceran water during the test period. D. carinata was sensitive to both MP and PNP; however, the parent compound was more toxic than its metabolite. This is the first study that demonstrated the acute toxicity of MP and PNP towards an Australian daphnid species. The present investigation emphasizes the need for including the native taxa as non-target test organisms while evaluating the toxicity of environmental pollutants.

     

Development of standard therapeutic guidelines for selected common diseases for the primary health care centres of a South Indian district

Method A questionnaire survey of medical officers was conducted to collect data on the most commonly‐presenting diseases and doctors' treatment choices in PHCs in Mysore. Draft guidelines were developed for these conditions based on available literature, together with microbiological sensitivity data from the three district hospitals. User feedback on the draft guidelines and on guidelines in general was obtained from medical officers using a postal questionnaire. Objective To develop standard therapeutic guidelines for selected common diseases for the primary health care centres (PHCs) of a South Indian district and to evaluate medical officers' perceptions about the proposed guidelines and about guidelines in general. Setting Sample of 17 of the 93 PHCs in Mysore. Key findings Upper respiratory tract infection was the most commonly‐presenting condition. Procaine penicillin was the most commonly‐used drug and there were examples of inappropriate treatment choices. The survey produced evidence that access to medicines on the government's “essential” list was not uniform, with many patients having to purchase prescribed drugs that were not on the list. The response rate to the user feedback questionnaire was 62 per cent (31 doctors). The medical officers had positive opinions about guidelines in general and felt that the guidelines we proposed were useful and would help them to improve their prescribing habits. Conclusions Prescribing in primary care in India needs to be improved. The involvement of potential users of the guidelines in their development should increase their acceptability and thus their use in practice.     

Toxicity of profenofos to the springtail, <Emphasis Type="Italic">Folsomia</Emphasis><Emphasis Type="Italic">candida</Emphasis>, and ammonia-oxidizers in two agricultural soils

Extensive use of organophosphorus insecticide profenofos (PFF) for agricultural and house-hold purposes has led to serious environmental pollution, with potential risk to organisms in the ecosystem. This study examined the toxicity of PFF to the soil springtail Folsomia candida and ammonia-oxidizers through a series of toxicity tests conducted on two agricultural soils. It was found that the survival, reproduction, hsp70 gene expression of F. candida and the soil potential nitrification rate (PNR) were sensitive to the PFF, whereas no apparent change was observed in the abundance of ammonia-oxidizers. The reproduction of F. candida was the most sensitive endpoint (mean 0.10 mg/kg of EC₅₀ value) for PFF, although the test was more time-consuming. The results of the acute toxicity tests suggested that the survival of F. candida could be considered as the most suitable bioindicator for fast screening of PFF toxicity because of its fast and easy test procedure. In addition, the hsp70 gene expression in F. candida and the PNR could be used as important parameters for assessment of PFF toxicity. The threshold concentration based on the obtained endpoints differed in the two soils, and consequently the soil property should be considered in toxicity assessments of contaminated soils.     

A comparison of the effects of silver nanoparticles and silver nitrate on a suite of soil dwelling organisms in two field soils

Nanomaterials are increasingly used in a wide range of products, leading to growing concern of their environmental fate. In order to understand the fate and effects of silver nanoparticles in the soil environment, a suite of toxicity tests including: plant growth with Elymus lanceolatus (northern wheatgrass) and Trifolium pratense (red clover); collembolan survival and reproduction (Folsomia candida); and earthworm avoidance, survival and reproduction (Eisenia andrei) was conducted. The effect of silver nanoparticles (AgNP) was compared with the effect of ionic silver (as AgNO₃) in two agricultural field soils (a sandy loam and a silt loam). Lethal (LC50) or sub lethal (IC50) effect levels are presented for all endpoints and demonstrate that in most cases AgNO₃ (i.e. ionic silver) was found to be more toxic than the AgNP across test species. The difference in effects observed between the two forms of silver varied based on test species, endpoint and soil type. In tests that were conducted across different soil types, organisms in the sandier soil had a greater response to the Ag (ionic and nano) than those in soil with a high silt content. Earthworms (avoidance behavior and reproduction) were the most sensitive to both AgNP and AgNO₃, while plant emergence was the least sensitive endpoint to both forms of Ag. The use of a test battery approach using natural field soils demonstrates the need to better quantify the dissolution and transformation products of nanomaterials in order to understand the fate and effects of these materials in the soil environment.     

Multiple assays of uranium toxicity in soil

The literature offers conflicting information on the phytotoxicity of uranium (U) in soil. Levels as low as 5 mg U/kg soil, well within the normal background range, have been cited as toxic, whereas many studies report no toxicity at levels 100- to 1000-fold higher. Uranium in soil does not often present a radiological hazard to humans, but toxicity to plants could lead to prescribed cleanup and assessment criteria for industrial activities. This study was designed to identify the toxic threshold of soil U. Nine levels of U were added to background-level soils. Beans were grown to maturity in an outdoor lysimeter study with 2 soils. Germination tests in the growth chamber were done with 11 soils and with 5 plant species. A rapid cycling Brassica rapa cultivar, proposed as a new toxicity test subject, was grown to maturity on 2 soils in the growth chamber, and germination of the second-generation seeds was investigated. Earthworm survival and soil phosphatase activity were measured. Measures of soil-extractable and tissue U concentrations were obtained. None of the measurements indicated detrimental effects of U below 300 mg/kg. In one of the soils, B. rapa produced seed at concentrations as high as 10,000 mg U/kg. The phytotoxicity of U occurred at concentrations 8- and 3-fold higher than the concentrations of As and Zn, respectively, which gave the same effect. © 1992 John Wiley & sons, Inc.     

Extrapolation of the laboratory-based OECD earthworm toxicity test to metal-contaminated field sites

The effects of cadmium, copper, lead and zinc on survival, growth, cocoon production and cocoon viability of the earthworm Eisenia fetida (Savigny) were determined in three experiments. In experiment 1, worms were exposed to single metals in standard artificial soil. For experiment 2, worms were maintained in contaminated soils collected from sites at different distances from a smelting works situated at Avonmouth, south-west England. In experiment 3, worms were exposed to mixtures of metals in artificial soil at the same concentrations as those present in the field soils. A survey of earthworm populations was carried out also. Population densities and species diversities of earthworms declined with proximity to the smelting works. No earthworms were found within 1 km of the factory. Comparison of toxicity values for the metals determined in the experiments indicated that zinc is most likely to be limiting earthworm populations in the vicinity of the works. Zinc was at least ten times more toxic to E. fetida in artificial soil than in contaminated soils collected from the field. This difference was probably due to the greater bioavailability of zinc in the artificial soil. The results are discussed in the context of setting protection levels for metals in soils based on laboratory toxicity data.     

Comparative study of phytotoxicity and genotoxicity of soil contaminated with biodiesel,diesel fuel and petroleum

The worldwide spillage of fossil fuels causes an ever-increasing environmental concern due to their resistance to biodegradation and toxicity. The diesel fuel is one of the derivative forms of petroleum that is widely used in the world. Its composition has many aromatic compounds and long hydrocarbons chains, both persistent and hazardous, thus requiring complex microbial dynamics to achieve full biodegradation. At this point, biodiesel has advantages because it is produced from renewable sources. It also has a relatively fast biodegradation. Biodiesel formulation chemically varies according to the raw material used for its production. While vegetable oils tend to have homogeneous proportions of linoleic and oleic fatty acids, animal fats have an heterogeneous distribution of stearic, palmitic and oleic fatty acids. As some studies have already detected the toxic potential of biodiesel from vegetable oil, this study sought information on the phytotoxic and genotoxic potential of animal fat-based biodiesel and compare it with fossil fuel as diesel fuel and crude petroleum. The impacts on the microbial activity of soils contaminated with biodiesel, diesel fuel and crude petroleum were performed by the dehydrogenase activity. Phytotoxicity tests were performed with Eruca sativa seeds and genotoxicity bioassays with Allium cepa seeds. The results showed a rapid assimilation of biodiesel by the autochthonous soil microorganisms. Soil contaminated with either diesel or crude petroleum inhibited the root and hypocotyl elongation of E. sativa. Overall, petroleum contaminated soils showed higher genotoxic potential. Biodiesel from animal fat was rapidly assimilated by soil microorganisms and did not present significant phytotoxic or genotoxic potential, but significantly reduced the mitotic index of A. cepa roots. Our results showed that biodiesel from animal fat have rapid biodegradability. Biodiesel also led to less impacts during seed development and lower genotoxic potential when compared to crude petroleum and diesel fuel. In addition, biodiesel from animal fat does not present the same toxicity demonstrated by biodiesel from soybean-based biodiesel described in current literature.

     

Use of four microbial tests to assess the ecotoxicological hazard of contaminated sediments

Three single-species bioassays (Microtox, Selenastrum capricornutum, and Panagrellus redivivus) and a test using microbial communities developed on artificial substrates were used in a series of in situ and laboratory tests evaluating the ecotoxicological hazard of contaminated sediments at two sites on Lake Michigan: Waukegan (Illinois) Harbor and The Chicago Area Confined Disposal Facility Study. In the single-species tests, exposure to elutriates of contaminated sediments significantly inhibited bacterial luminescence, algal photosynthesis, and nematode survival and growth at polluted stations, while elutriates from control stations did not. The battery of three tests is a promising screening tool for in-place pollutants. Protozoan species richness and protozoan phototroph abundance were inhibited by elutriates from contaminated sites, but the abundance of heterotrophic protozoans was enhanced by sediment elutriates from some stations. Microbial community photosynthesis was significantly inhibited by most sediment elutriates, while community respiration was often stimulated; thus, functional responses paralleled the structural changes. Overall, the results of the microbial community tests were consistent with expected patterns of toxicity at the two sites on Lake Michigan. In general, single-species test results agreed with the community bioassays. Although community tests may be more realistic than single-species bioassays in predicting the impact of sediment contamination on actual ecosystems, caution must be exercised in interpreting the results.     

Responses of Vallisneria natans (Lour.) Hara to the combined effects of Mn and pH

Aquatic plants play a vital role in maintaining the health and stability of ecosystems and in ecological restoration of contaminated water bodies. Herein, a 21-day-long laboratory-scale experiment was designed to explore the growth and physiological responses of Vallisneria natans (Lour.) Hara (V. natans) to the combined effects of manganese (Mn, 5, 20, and 80 mg L⁻¹) and pH (pH 4.0, 5.5, and 7.0). Our results showed the combined toxicity intensity was closely related to Mn concentration and the toxicity exhibited by Mn gradually strengthened with the decrease of pH level. High concentration of Mn stress significantly reduced plants leaf area, final leaf number, photosynthetic pigment content, RGR (relative growth rate) and biomass accumulation, but significantly increased the contents of malondialdehyde (MDA) and hydrogen peroxide (H₂O₂). At the same time, V. natans plants can resist the adverse stress by activating the antioxidant defense system, including superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and polyphenol oxidase (PPO) activities. Besides, V. natans tended to adjust the biomass allocation strategy and transferred more energy to the subsurface and the ramets and stolons parts under the combined stress. This experiment also showed that the increasing pH within a certain range could largely improve the removal rate of Mn (at highest by 84.28%). This may indicate the V. natans plant species can act as a promising tool for the Mn phytoremediation in aquatic environments which needs to be further explored by longer cycle field studies.

     

Osmotic tolerance of rabbit corneal epithelium in tissue culture

Abstract

The osmotic tolerance of stratified rabbit corneal epithelial cultures was determined for a balanced salt solution and various pharmaceutical vehicles in an effort to determine the biocompatibility of the different formulations after 4–128 min exposures. Acute damage was assessed by monitoring the release of radiolabeled nucleotides and corresponding changes in tissue morphology of the prelabeled cultures. Protracted damage was evaluated by re-examining the morphology of the same cultures after 24 hr along with quantitative measurements of residual ³H release, tissue loss, and concomitant changes in protein synthesis. Our testing results indicated that the permissive limits of a balanced salt solution were between 305 and 400 mOsm, which is comparable to the guidelines for native epithelium in situ established by organ perfusion studies. In contrast, the permissive limits for unbuffered and buffered intraocular vehicles were more restricted, since only isotonic formulations were relatively nontoxic. Conventional topical vehicles, by comparison, were much more damaging, which was probably a consequence of their chelating properties and the inherent toxicity of boric acid, which is a common buffering agent used for topical ophthalmic solutions. These data indicate that this type of bioassay can be effectively used for screening in drug development programs, and for establishing accurate guidelines for pharmaceutical formulations.     

Using chemical fractionation to evaluate the phytoextraction of cadmium by switchgrass from Cd-contaminated soils

The purpose of this study is to evaluate the phytoextraction of cadmium (Cd) from contaminated soils by switchgrass (Panicum virgatum L.), which is a promising energy crop with high biomass. Two ecotypes of switchgrass cultivars, Alamo and Blackwell, were investigated in a pot experiment. Dry weight and plant Cd concentration of the switchgrass plants growing on Cd-spiked soils (0, 20, and 60 mg Cd kg⁻¹ soil) with chelating agent amendments (1 g kg⁻¹ citric acid [CA] and 0.1 g kg⁻¹ ethylene diaminetetraacetic acid [EDTA]) were measured to examine the phytotoxicity and accumulation of Cd in the switchgrass. Fractions of Cd (F1, exchangeable; F2, carbonate; F3, Fe–Mn oxide; F4, organic matter; F5, residual) for the soils sampled at the time of harvesting were also determined using chemically sequential extractions. In the results, the dry weight of the switchgrass decreased with increasing Cd, with a significant dry weight reduction when Cd exceeded 20 mg kg⁻¹. However, the high Cd spike of 60 mg kg⁻¹ was not lethal to Alamo and Blackwell, which suggests that switchgrass plants can tolerate Cd and grow in contaminated soils. Compared with the control, the CA and EDTA amendments had no adverse effect on the growth of switchgrass plants. With regard to Cd accumulation, higher plant Cd concentrations were frequently found after CA amendment in Alamo; however, the Cd concentrations of Blackwell plants may increase when amended with EDTA. On the basis of the fractionation of soil Cd, dry weight and plant Cd concentration could be expressed as a function of Cd fractionation to predict the phytoextraction of Cd. Thus, the fractionation of Cd is a useful approach for evaluating the phytoextraction of Cd by switchgrass in contaminated soils. According to the comparison of phytoextractions of Cd between Alamo and Blackwell, Alamo plants removed substantially more Cd from Cd-spiked soils than Blackwell. Therefore, Alamo is better suited for the phytoextraction of Cd from contaminated soils.     

Copper toxicity in a natural reference soil: ecotoxicological data for the derivation of preliminary soil screening values

The risk assessment of contaminated soils is conventionally done with the support of soil screening values (SSVs). Since SSVs are still unavailable for many European countries, including Portugal, standardized toxicity tests are urgently claimed for their derivation. Hence, this work aimed the generation of toxicity values for copper (Cu) in a natural reference soil (PTRS1) targeting different terrestrial species, endpoints and soil functions, as to derive a preliminary Cu SSV. For this, the Assessment Factor approach was applied, which allowed calculating predicted no effect concentrations (PNEC) for Cu that will be the basis for SSV proposal. In order to increase the reliability of the PNEC, and hence of the SSV, a lab/field factor was applied to correct the toxicity values used for PNEC determination. Cu affected urease, cellulase and nitrogen mineralization activities. The EC₅₀ values calculated for the invertebrates reproduction were 130.9, 165.1 and 191.6 mg Cu Kg^?1soil_dw for Eisenia andrei, Enchytraeus crypticus and Folsomia candida, respectively. Cu inhibited seed germination mainly for Lactuca sativa, whilst it was toxic for the growth of different plant species (EC₅₀s between 89 and 290.5 mg Cu Kg^?1soil_dw). Based on the outcomes gathered, we proposed SSVs for Cu ranging between 26.3 and 31.8 mg Kg^?1 soil_dw, which is above the background values reported and below all the EC₂₀s recorded for the species and endpoints herein analyzed. Overall, this work describes a procedure that could be easily followed by other European countries wishing to derive SSVs adjusted to their soils.     

Effects of phenanthrene on lemna minor in a sediment-water system and the impacts of UVB

The objective of this study was to evaluate if the Lemna -bioassay is appropriate to test contaminated sediments. A mixture of sand was spiked with phenanthrene to investigate whether sediment-bound pollutants can affect the plants via direct contact of the roots or the underside of the leaves. After 24 h of equilibration for sorption/desorption processes, the test was carried out in the sediment–water mixture, and another test was performed with the aqueous phase which was separated from the sediment. The growth inhibition of Lemna was nearly the same in both tests. Hence it follows that the toxicant is adsorbed from the aqueous phase via the underside of the leaves and sediment bound phenanthrene is not bioavailable. Polycyclic aromatic hydrocarbons are known to show photoinduced toxicity to plants in the presence of UV which is a result of photosensitization reactions in the plant and photomodification to more toxic and better soluble photoproducts. Photoinduced toxicity could be observed in the water phase during UVB treatment, whereas the presence of suspended sediment probably lowered the UV intensity, resulting in a lower growth inhibition.     

Coupling bioaccumulation and phytotoxicity to predict copper removal by switchgrass grown hydroponically

A major challenge in phytoextraction is to increase plants’ removal rates of metals from contaminated soils. In this study, we developed a phytoextraction model, by coupling a saturable Michaelis–Menten type accumulation model and an energy-based toxicity model, to predict copper (Cu) removal by switchgrass (Panicum virgatum L.) grown hydroponically under various exposure concentrations. Results of the present study indicated that the phytotoxicity of Cu to switchgrass is relatively low, whereas a certain accumulation capacity exists in the plant for Cu. In addition, the simulation results suggested that, under a lower dissolved concentration, Cu removal is increased more efficiently as the exposure duration increases. Although it is difficult to extrapolate the results from greenhouse-based hydroponic experiments to field conditions, we believe that the current methodology can offer a first approximation in predicting the phytoextraction duration needed for plant species to remove a specific metal from contaminated sites, which is crucial in evaluating the economic costs for remediation purposes.     

Oxidant effects and toxicity of Croton campestris in Drosophila melanogaster

Context: Croton campestris A.St.-Hil. (Euphorbiaceae) is a species native to Northeast Brazil used by traditional communities for the treatment of a variety of health problems. However, potential toxicological effects of this plant are unknown.

Objective: The potential toxicity of the hydroalcoholic extract of C. campestris leaves on Drosophila melanogaster insect model, additionally with phytochemical constitution and cellular mechanisms mediating the action of extract were analysed in this study.

Materials and methods: Constituents of the extract were evaluated by HPLC. In vitro antioxidant potential of extract was analysed by DPPH, ABTS and FRAP. Flies injected culture medium mixed with extract (0.1–50?mg/mL) for 72?h. After, ROS production was evaluated by DCF-DA oxidation. Phosphorylation of MAPK signalling pathway was investigated by Western blotting method. Activity of antioxidant enzymes was analysed in homogenates.

Results: Major components of the extract include quercetin (38.11?±?0.06?mg/g), caffeic acid (20.06?±?0.17?mg/g) and kaempferol (15.45?±?0.05?mg/g). Consumption of the extract impaired locomotor performance and induced fly death of flies (LC₅₀ of 26.51?mg/mL). Augmented ROS formation and SOD, CAT and GST activity were observed from 0.1?mg/mL. JNK and p38 kinases phosphorylation was modulated and Paraquat-induced toxicity was augmented by extract.

Discussion and conclusion: Our data show important toxicological effects of C. campestris leading to increased mortality and impaired locomotor performance accompanied by induction of cell stress markers in flies. The study draws attention to the indiscriminate use of plant extracts.     

Assessing the ecotoxicological effects of long-term contaminated mine soils on plants and earthworms: relevance of soil (total and available) and body concentrations

The interactions and relevance of the soil (total and available) concentrations, accumulation, and acute toxicity of several essential and non-essential trace elements were investigated to determine their importance in environmental soil assessment. Three plant species (T. aestivum, R. sativum, and V. sativa) and E. fetida were simultaneously exposed for 21 days to long-term contaminated soils collected from the surroundings of an abandoned pyrite mine. The soils presented different levels of As and metals, mainly Zn and Cu, and were tested at different soil concentrations [12.5, 25, 50, and 100 % of contaminated soil/soil (w/w)] to increase the range of total and available soil concentrations necessary for the study. The total concentrations in the soils (of both As and metals) were better predictors of earthworm uptake than were the available concentrations. In plants, the accumulation of metals was related to the available concentrations of Zn and Cu, which could indicate that plants and earthworms accumulate elements from different pools of soil contaminants. Moreover, Zn and Cu, which are essential elements, showed controlled uptake at low concentrations. The external metal concentrations predicted earthworm mortality, whereas in plants, the effects on growth were correlated to the As and metal contents in the plants. In general, the bioaccumulation factors were lower at higher exposure levels, which implies the existence of auto-regulation in the uptake of both essential and non-essential elements by plants and earthworms.     

Acute and chronic toxicity of chromium and cadmium to the tropical cladoceran pseudosida ramosa and the implications for ecotoxicological studies

In this study, the acute and chronic toxicity of the metals chromium and cadmium were tested against the tropical freshwater cladoceran Pseudosida ramosa. Acute tests showed that the 48‐h LC₅₀ of chromium was 29 μg L^?1, while that of cadmium was 12 μg L^?1. P. ramosa had a similar sensitivity to those of other cladoceran species cultured in the same conditions as in this study, or a higher sensitivity when water hardness was raised. Long‐term chronic exposure of P. ramosa to chromium decreased maternal survival, fecundity, and fertility at a concentration of 10 μg L^?1. For cadmium, reductions in the same endpoints were observed at a concentration of 3 μg L^?1. Moreover, the degree of toxicity of the chromium and cadmium to P. ramosa after release of the first brood was similar to the result obtained after 21 days, using reproduction as the endpoint. Brazilian water bodies located near industrial areas already show concentrations of chromium and cadmium higher than levels causing acute and chronic toxicity to P. ramosa in our study. Many water quality criteria in tropical regions are based on ecotoxicological tests with non‐native species and, consequently, this may lead to errors of interpretation when the permitted maximum levels of for each toxic substance are established. Therefore, we reinforce the idea of using native species to establish the maximum concentrations of toxic substances in water quality criteria, especially for metals, since their effects are related to water hardness, pH, and temperature specific to each region. © 2011 Wiley Periodicals, Inc. Environ Toxicol 29: 176–186, 2014.