Experimente zum Verbleib von Cyanid nach Aufnahme in Pflanzen

Free cyanide (prussic acid) can be degraded by many organisms. Experimental data on the kinetics of degradation by plants, however, are rare. We experimentally determined the mass balance of potassium cyanide in the system nutrient solution/plant/air In the presence of living willows (Salix alba) and light, free cyanide is almost completely eliminated from the nutrient solution, also by a willow cell suspension (> 99%) and even by a dried-out stem (> 80%). The loss is smaller when the willow is autoclaved (30%). Without a willow, the CN can be recovered to more than 89%. The loss depends on light and transpiration. Volatilization and the formation of complexed cyanide are of minor relevance for the elimination of free CN. The most plausible loss process is metabolism by plants. The transfer into the roots and stem does not change with the light/dark-rhythm. The transfer factor (mg CN/kg plant fw/mg CN/l solution) after 24 h, and related to the initial concentration in solution, is between 2 and 3 for roots, 0.1 to 0.6 for leaves and 0.2 for stems. In the roots of willows and elderberries which were growing on the former gas worksite in Holte, Denmark, high concentrations of cyanides were found. In leaves and fruits, concentrations are a factor of 10 to 1000-fold lower and up to as high as that found in non-exposed control plants. Due to these results, a cyanide-polluted site in Denmark has been remediated with poplar trees.     

Bepflanzung einer Tankstelle mit Weiden

In Axelved, Denmark, an abandoned gas filling station serves as a test field for phytoremediation. Laboratory studies accompany the project. The toxicity of fresh and weathered gasoline and diesel to willow and poplar trees was studied by use of a tree transpiration toxicity test. The correlation between diesel content in soil and decrease in willow tree transpiration (Salix viminalis x schwerinii) was highly significant (r ²=0.81, n=19). the EC₅₀ (50% inhibition of transpiration) for the sum of hydrocarbons (HC) was determined to be 3910 mg/kg (95% confidence interval from 2900 to 5270 mg/kg). The EC₁₀ was 810 mg/kg (95% confidence interval 396 to 1660 mg/kg). The results were verified with artificially mixed diesel and gasolinecontaminated soils and two willow and one poplar species (S. viminalis, S. alba andPopulus nigra). The degradation of radiolabeledm-xylene was studied with and without willows. The compound was readily degraded. Willow trees accelerated the elimination, but mainly due to the volatilization ofm-xylene. Model studies provided the result that biodegradation in soil is the fastest elimination process at the site, but it is limited by the availability of electron acceptors. The pollutants are almost persistent in the groundwater, but in aerated soil, 10000 mg/kg hydrocarbons at 1 m depth are degraded within 13 years. The main effect of willows on the pollutants’ persistence is that willows transpire water, lower the groundwater level and aerate the soil, hereby speeding up biodegradation.     

Analytik von Umwandlungsprodukten des Schwefellosts (S-LOST)

The results of investigations of the aquatic ecotoxicity of sternutators and their metabolites (phenyl arsenic compounds) are presented. The standardized luminescence inhibition test (LumisTox, Dr. Lange) with the marine bacteriaVibrio fischeri was applied according to the German norm DIN 38412, part 34. All investigated organic AS(III) compounds exhibit EC₅₀-values (50 % inhibition of the luminescence) of less than 1 mg/l, whereas all investigated organic As(V) compounds and inorganic arsenic show EC₅₀-values exceeding 100 mg/l     

Effects of the insecticide sevin and its first hydrolytic product, 1-naphthol,on some early developmental stages of the bay mussel Mytilus edulis

Six developmental stages of the bay mussel Mutilus edulis, from fertilization to 32 h after fertilization, and also unfertilized eggs, were exposed for 1 h to different concentrations of the insecticide Sevin and its first hydrolytic product, 1-naphthol. After exposure, the larvae or eggs were separated from the pesticide solution and returned to clean water. At 48 h after fertilization, the numbers of normal and abnormal larvae were determined and 1-h EC₅₀ values (the effective concentrations that caused anomalous development of 50% of the test animals) were calculated. The most sensitive developmental stage was the one that occurred shortly after fertilization at the time of appearance of the first polar body. Thereafter, sensitivity decreased as age increased. The EC₅₀ of Sevin for the first polar body stage and 32-h stage were 5.3 and 24.0 mg/l of Sevin, respectively. The EC₅₀ of l-naphthol for the first polar body stage was 5.2 mg/l. Effects of the toxicants on development were characterized by disjunction of blastomeres, a reduction in the rate of development, and asynchronous and unaligned cleavages.     

土壤水溶态铜对小白菜的毒害效应及其预测模型

土壤中铜(Cu)重金属的生物毒性/有效性主要取决于它们在土壤液相中含量和土壤溶液的性质。探寻土壤有效态Cu的生物毒害效应,表征量化其与土壤溶液性质关系,可为土壤Cu的环境风险评价提供参考。选取17种典型农田土壤,探讨了有效态Cu(土壤孔隙水以及CaCl_2浸提态)对小白菜生长的毒性效应及其预测模型。结果表明:土壤孔隙水中Cu对小白菜生长10%抑制的毒性阈值值(EC_(10))和50%抑制的毒性阈值(EC_(50)),最大值与最小值相差为14.7和14.6倍;同样,对于CaCl_2提取态Cu的EC_(10)和EC_(50),最大值与最小值相差12.7和7.7倍,表明土壤溶液性质对水溶性Cu对小白菜的毒性阈值影响很大。建立了土壤溶液的重要因子(溶解性有机碳、土壤溶液pH值、电导率、全硫含量、Ca~(2+)、Mg~(2+)、K~+、Na~+)和水溶性Cu阈值之间的多元回归关系,结果显示,土壤溶液性质可以较好地预测水溶性Cu对小白菜的毒性阈值。同时,土壤溶液中Mg~(2+)、K~+和S的含量是控制孔隙水中Cu对小白菜生长毒性的最重要因子,单一的S能分别解释34%的EC_(10)变异,K~+解释26%的EC_(50)变化。本研究结果可为陆地环境中水溶性Cu的风险评价提供基础。     

Evaluation of tests to assess the quality of mine-contaminated soils

An acid metal-contaminated soil from the Aljustrel mining area (a pyrite mine located in SW Portugal in the Iberian Pyrite Belt) was subjected to chemical characterisation and total metal quantification (Cd, Cr, Cu, Ni, Pb and Zn). Water-soluble metals were determined and a sequential extraction procedure was used to investigate metal speciation. Two bioavailable metal fractions were determined: a mobile fraction and a mobilisable fraction. Soil ecotoxicity was studied using a battery of bioassays: plant growth test and seed germination with cress (Lepidium sativum L.), earthworm (Eisenia fetida) mortality, E. fetida avoidance behaviour, luminescent inhibition of Vibrio fischeri and Daphnia magna immobilisation. Although the total content of Cu, Zn and Pb in the soil was large (362, 245 and 1,250 mg/kg dry matter, respectively), these metals were mostly structurally bound (87% for Cu, 81% for Zn and 89% for Pb) and, therefore, scarcely bioavailable. Nonetheless, the D. magna immobilization test using soil leachate showed an EC₅₀ (48 h) of 36.3% (v/v), and the luminescent inhibition of V. fischeri presented an EC₂₀ (15 min) of 45.2% and an EC₂₀ (30 min) of 10.7% (v/v), suggesting a considerable toxic effect. In the direct exposure bioassays, E. fetida avoided the mine soil at the highest concentrations (50%, 75% and 100% v/v). At the same soil concentrations, cress showed negligible growth. The results suggest the need to use a battery of toxicity tests, in conjunction with chemical methods, in order to assess the quality of mine-contaminated soils correctly.     

Mikrobiologische Volatilisierung von anorganischem Selen aus Deponiesickerwässern bei umweltrelevanten Konzentrationen

Background, aim, and scope Determination of the rates of microbial alkylation are of interest with respect to natural attenuation of harmful selenium concentrations or selenium charges in contaminated ecosystems. Materials and methods Landfill gas and the headspace of microbial microcosm incubation vessels were sampled in Tedlar^® bags. On-line hyphenation of an efficient enrichment method (cryotrapping-cryofocusing), a gaschromatographic separation technique, and the sensitive ICP-MS detection system was used for speciation of volatile organoselenium compounds. A detection limit at the ultra trace level (pg Se) was achieved with this CT-CF-GC-ICP-MS technique. Results Incubation of landfill leachate with Alternata alternata as an active methylating organism showed a production of volatile selenium compounds (DMSe, DMDSe, EMDSe, DEDSe) over the whole range of applied inorganic selenium concentrations (10?µg?L^–1 to 10?mg?L^–1), with volatilization rates of up to 10?mg m^–3?d^–1. For selenium concentrations of 1?mg?L^–1 in the nutrient broth, up to 7?% of the inorganic selenium was volatilized after one week. The same volatile selenium compounds were observed in landfill gas. Discussion The amount of volatilized selenium was comparable to that found in other studies with microbial pure cultures as well as isolates from waters or soils, but at much lower initial concentrations used in the incubations. Conclusions The alkylation of selenium in the enriched mixed culture from landfill leachate at environmentally relevant concentrations indicates that the organoselenium compounds of same species composition and distribution determined in landfill gas are produced by microorganisms. Recommendations and perspectives The microbial alkylation of toxic inorganic selenium species to less toxic or non-toxic, volatile compounds is an efficient method for bioremediation of contaminated sites even at relatively low Se concentrations.     

Ecotoxicity in Aliivibrio fischeri of Ibuprofen,Omeprazole and their Mixtures

The acute ecotoxic effects of ibuprofen and omeprazole and their mixture have been measured using Aliivibrio fischeri as a biomodel. The toxic effects were also tested after 5 days, and an effect-driven approach was used to analyse the results. The toxic effects of the mixtures were compared with the predictions obtained using concentration addition and independent action mathematical methods.

According to the Passino and Smith classification, the results indicate that ibuprofen can be considered slightly toxic (10<EC₅₀ <100?mg?L^-1), while omeprazole can be denoted as moderately toxic (1<EC₅₀ <10?mg?L^-1) to Aliivibrio fischeri. An overestimation of the actual ecotoxic effect of the mixture was found when the concentration addition and independent action methods were applied. Finally, the effect-driven approach indicated that the transformation products of the studied drugs should be prioritized for risk assessment purposes.     

The influence of arsenic speciation (AsIII & AsV) and concentration on the growth, uptake and translocation of arsenic in vegetable crops (silverbeet and amaranth): greenhouse study

We examined arsenic (As) uptake by vegetable crops (amaranth, Amaranthus gangeticus, and silverbeet, Beta vulgaris) as affected by As speciation (As^III and As^V) and their concentrations in nutrient solution. Amaranth and silverbeet were grown in a nutrient solution containing four levels of arsenate (As^V): 0, 1, 5, and 25 mg As/l and three levels of arsenite (As^III): 0, 5, 10 mg As/l. Both As^V and As^III are phytotoxic to these crops with the latter being five times more toxic. Amaranth treated with As^III exhibited As toxicity symptoms within 48 h of exposure and was close to death within 1 week. However, As^V treatment did not show clear toxicity symptoms other than wilting and yield reduction at the highest dose rate of 25 mg As^V/l. The main mechanism used by vegetable crops to tolerate As^V is probably avoidance—limiting As transport to shoots and increasing As accumulation in the root system. When As^V was added to the nutrient solution, the uptake of As in shoots increased and, at the highest dose (25 mg As^V/l), 60 μg As/g DW (3.6 mg/kg FW) accumulated in the edible portion, which exceeds the WHO recommended limit for food stuffs (2 mg/kg FW) as the water contents of the crops were 94%. It is therefore important to determine the nature of the As species and their bio-accessibility. Iron treatment with 0.5 mg NaFe(III)EDTA/l dose decreased silverbeet As uptake by 45% given its affinity to bind As at the root surface or root rhizosphere and so restrict As translocation to the shoots.     

TiO<Subscript><Emphasis Type="Bold">2</Emphasis></Subscript> nanoparticles – Relationship between dispersion preparation method and ecotoxicity in the algal growth test

PurposeLittle is known about the ecotoxicity of nanomaterials and there are no specific guidelines for sample preparation and testing. We set out to establish whether the method used to prepare TiO₂ dispersions had a significant impact on aquatic ecotoxicity. We also followed the formation of agglomerates during the incubation period.MethodsWe applied the algal growth inhibition test (OECD test guideline no. 201). Dispersions were prepared by stirring and/or ultrasonication for different durations, and by filtration according to an OECD procedure recommended for testing difficult substances.ResultsSamples stirred for 7?d were not toxic, but EC₂₀ values could be calculated for all the other treatments. Shorter treatments generated EC₂₀ values in the range 1–27?mg/L. Only the shortest treatment (1 min stirring, 1 min ultrasonication) produced an unusually high EC₂₀ value, indicating low toxicity. Development of agglomerate size and of toxicity depends on the nanoparticles. We found that ecotoxicity was predominantly caused by a fraction of nanoparticles and agglomerates obtained by passing dispersions through a 0.22-µm filter.ConclusionsWe propose a short treatment regime to generate the most relevant ecotoxicity data for TiO₂, for example stirring for 1?min followed by 3 min ultrasonication. Until more data concerning the ecotoxicity of different fractions are available, we recommend the testing of unfiltered dispersions rather than filtrates. Relating ecotoxicity to the total hydrodynamic surface of the nanomaterials rather than concentration does not seem to improve the accuracy of ecotoxicity assessments using the algal growth inhibition test.     

Modeling compensated root water and nutrient uptake

Plant root water and nutrient uptake is one of the most important processes in subsurface unsaturated flow and transport modeling, as root uptake controls actual plant evapotranspiration, water recharge and nutrient leaching to the groundwater, and exerts a major influence on predictions of global climate models. In general, unsaturated models describe root uptake relatively simple. For example, root water uptake is mostly uncompensated and nutrient uptake is simulated assuming that all uptake is passive, through the water uptake pathway only. We present a new compensated root water and nutrient uptake model, implemented in HYDRUS. The so-called root adaptability factor represents a threshold value above which reduced root water or nutrient uptake in water- or nutrient-stressed parts of the root zone is fully compensated for by increased uptake in other soil regions that are less stressed. Using a critical value of the water stress index, water uptake compensation is proportional to the water stress response function. Total root nutrient uptake is determined from the total of active and passive nutrient uptake. The partitioning between passive and active uptake is controlled by the a priori defined concentration value c_max. Passive nutrient uptake is simulated by multiplying root water uptake with the dissolved nutrient concentration, for soil solution concentration values below c_max. Passive nutrient uptake is thus zero when c_max is equal to zero. As the active nutrient uptake is obtained from the difference between plant nutrient demand and passive nutrient uptake (using Michaelis–Menten kinetics), the presented model thus implies that reduced passive nutrient uptake is compensated for by active nutrient uptake. In addition, the proposed root uptake model includes compensation for active nutrient uptake, in a similar way as used for root water uptake. The proposed root water and nutrient uptake model is demonstrated by several hypothetical examples, for plants supplied by water due to capillary rise from groundwater and surface drip irrigation.     

Investigation of the hemolytic effects of various organophosphoric acid triesters (OPEs) and their structure‐activity relationship

The hemolytic effects of various organophosphonc acid triesters (OPEs) were investigated and they showed strong hemolyic toxicity except triethyl phosphate and tris(chloroethyl)phosphate. 2‐Ethylhexyl diphenyl phosphate (EHDP) showed the strongest toxicity. By quantitative structure‐activity relationship (QSAR) study, one‐parameter regression equation to estimate hemolysis was not obtained. But, two‐parameter regression equations were obtained which were enought to estimate EC₅₀ and EC₂₀. The correlation coefficients with the two‐parameter regression equations were 0.939 for log(l/EC₅₀) and 0.946 for log(l/EC₂₀).     

Exposure-response of Cr(III)-organic complexes to <Emphasis Type="Italic">Saccharomyces cerevisiae</Emphasis>

Hexavalent chromium [Cr(VI)] bioreduction produces soluble Cr(III)-organic complexes. The Cr(III)-organic complexes are relatively stable once they are formed, and no data about their toxicity were reported. Therefore, this study aims to investigate the bioavailability and toxicity of the soluble Cr(III)-organic complexes. Saccharomyces cerevisiae L-1 wild type yeast strain was chosen as the model organism and Cr(III)-citrate was selected as the representative compound of the Cr(III)-organic complexes. The short-term chronic aquatic toxicity tests of the Cr(III)-citrate was explored by measuring growth inhibition, direct viable cell count, dry biomass, biosorption, and the amount of CO₂ production. Cr(III)-citrate exerted a toxicity of 51 mg/L with an EC ₅₀, which was calculated from the percent growth inhibition. These toxicity data would be helpful to define the toxic potential of the organo-chromium-III compounds in the environment.     

Assessing the toxicity of chemical compounds associated with marine land-based fish farms: The use of mini-scale microalgal toxicity tests

Many chemicals that are currently used in aquaculture have not been evaluated with regard to their specific effects on the aquatic environment. In the present study, the toxic effects of several chemicals associated with land-based marine fish farming activities were assessed using two species of marine microalgae (Phaeodactylum tricornutum and Isochrysis galbana). Mini-scale toxicity tests were performed with six antibiotics (amoxicillin, ampicillin, flumequine, oxytetracycline, streptomycin and sulfadiazine) and two disinfectants (formaldehyde and hypochlorite). Amoxicillin and streptomycin did not exert toxic effects. Sulfadiazine was the most toxic chemical; the EC₅₀ values were 0.11 mg/L and 1.44 mg/L for P. tricornutum and I. galbana respectively. As expected, the disinfectants displayed high toxicity, and P. tricornutum was particularly sensitive to these compounds. Although the differences in microalgal sensitivity depended on the chemical considered, both species were highly sensitive to most of the compounds tested. We recommend the inclusion of mini-scale microalgal toxicity tests in environmental risk assessment (ERA) and environmental monitoring plans because they are cost-effective and rapid.     

土壤Cd污染对跳虫Folsomia candida的生态毒性

采矿及冶炼等行为造成了严重的土壤重金属污染,其中Cd污染及其带来的健康风险近年来引起人们的高度重视。利用弹尾目跳虫开展土壤Cd污染的生态毒理研究,对Cd污染土壤的生态风险评价具有重要意义。本研究将跳虫Folsomia candida(F.candida)暴露在不同Cd浓度污染的人工土壤中,利用跳虫存活数量、繁殖数量及回避行为实验来评价重金属Cd污染对跳虫的生态毒性。结果表明,Cd对F.candida的急性毒性LC50值为2 086.93 mg·kg~(-1),慢性毒性的繁殖抑制(28 d)EC50值为224.95 mg·kg~(-1)。此外,Cd对跳虫回避行为影响的EC50(48 h)为721.26 mg·kg~(-1)。可以看出,慢性毒性的EC50值与Cd对回避行为影响的EC50值近似,但远低于急性毒性LC50值。因此,跳虫F.candida的回避行为和繁殖率对Cd污染土壤有较高的灵敏度,可用来表征土壤中Cd的生态毒性。     

A Forest Nutrient Cycling and Biomass Model (ForNBM) based on year-round,monthly weather conditions: Part II: Calibration,verification, and application

The ForNBM was applied to the Nashwaak Experimental Watershed Project in central New Brunswick, Canada. The data represented a mixed hardwood site and included information about nutrient leaching, foliage and wood biomass, leaf fall, and ancillary information required for model initialization. Ancillary information included forest cover type, stand density, forest floor depth, soil rooting depth, soil texture, soil substrate type, initial amounts of biomass and N, S, Ca, Mg, and K content in foliage, wood, and roots, and mineral soil nutrient contents in soil solution, on ion-exchange sites, and in the soil.The authors were able to calibrate the model with existing data. The model simulated observed monthly leaching reasonably well. The r²-values of model simulations compared with field observations of monthly leaching of NO₃⁻_N, NH₄⁺_N, Ca, Mg, and K were 0.78, 0.7, 0.78, 0.84, and 0.75, respectively. Modeled multi-year cumulative leaching of NO₃⁻_N, NH₄⁺_N, Ca, Mg, and K compared with actual values gave r²-values close to one for all cases considered.The results also showed that soil nutrient leaching had increased approximately five-fold for NO₃⁻_N, 80% for NH₄⁺_N, 71% for K, 20% for Ca, and 14% for Mg during the 3 years following a stem-only harvest operation applied watershed-wide. However, the model simulation showed that increased nutrient leaching during the 11 years following the stem-only harvest was small compared with the amounts removed in the biomass during the harvest. Increased nutrient leaching following harvesting did not appear to impact site productivity over the long term.     

Les variations de la phototaxie des larves de crustacés sous l'action de divers polluants métalliques: mise au point d'un test de toxicité subléthale

Variations in orientation and photokinesis of Carcinus maenas and Palaemon serratus Zoeas I were studied in the presence of excess cobalt and strontium chlorides or silver nitrate. The speed of movement of larvae toward light (phototaxis) appears to constitute a good parameter for testing sublethal toxicity. The salts are toxic to crab larvae in the following decreasing order of toxicity: silver nitrate, cobalt chloride, strontium chloride. Within 4 days, orientation of C. maenas Zoea I was disturbed by excess CoCl₂ and AgNO₃ in the range 0.01 to 0.1 mg/l, and by excess SrCl₂ in the order of 100 mg/l. For P. serratus Zoea I, the corresponding values were 100 to 500 mg/l CoCl₂, 100 mg/l AgNO₃, and above 500 mg/l SrCl₂. C. maenas photokinesis was decreased by amounts of 0.001 mg/l of CoCl₂ or AgNO₃ within a period of only 2 to 3 days.     

Influence of Dissolved Organic Matter On the Bio-Availability and Toxicity of Metals in Soils and Aquatic Systems

Cations in soil are essential for the growth of plants and micro-organisms. Their availability is dependent on soil organic matter. Soil organic matter (SOM) is heterogeneous comprising amino, aliphatic and phenolic acids, but particularly humic substances. All these substances can complex cations selectively. Mechanisms of complexation with dissolved organic matter are discussed. Such complexation can lead to the apparently contradictory observations that dissolved organic matter (DOM) can either increase the concentration of some less soluble nutrients, making them more available for plant uptake, or make them less available and hence less toxic. the importance of DOM is discussed in relation to soil solution, particularly the rhizosphere, and also in relation to aquatic systems. the latter systems contain mainly dissolved humic substances whereas in the soil, non-humic substances assume a greater importance.

SOM in the rhizosphere is derived from plant, microbial and animal remains but much, especially the water-soluble compounds, are acquired through root exudation. Exudation has important consequences for enhanced nutrient availability as a result of the production of non-humic substances such as amino, aliphatic and phenolic acids. in future, the role of root exudation in relation to DOM and nutrient availability should be investigated more fully, particularly as predicted elevated CO₂ levels are likely to have a major impact on root exudation, nutrient availability, and possibly ecosystem community structure and functioning. It is likely that more information will become available on aquatic systems as more highly sensitive techniques and equipment capable of dealing with low concentrations of DOM in these systems become available.     

Monitoring toxicity of an azo dye methyl red and a heavy metal Cu,using plant and animal bioassays

Toxicities of an azo dye methyl red and a heavy metal copper (Cu) were quantified, using growth and mortality as end points, in four plant species and three animal species by subjecting them to short-term (4 days for animals, 10 days for plants) static bioassays. Lemna aequinoctialis Welwitch (EC₅₀: 7–16 ppm) was found to be the most sensitive species for methyl red, Ceratophyllum demersum L. (EC₅₀: 25 ppm) and Lactuca sativa L. (EC₅₀: 56 ppm) were intermediate, while Oryza sativa L. shows reduction in seedling vigor (9–27%) of <50%, being the least sensitive amongst the tested plant species. Methyl red toxicity is almost 3–5-fold higher in growing medium (pH = 5.8–6.0), even at high nutrient levels, while Cu toxicity is higher in nutrient-poor alkaline medium at alkaline pH (8.3–8.7; EC₅₀: Ceratophyllum = 104–200 ppb; Lemna = 100–170 ppb) compared to nutrient-rich acidic medium (pH = 5.4–5.7; EC₅₀: Ceratophyllum = 2600–3175 ppb; Lemna = 4350–4715 ppb). Rice tolerance (EC₅₀: 6500 ppb) was found to be higher than hydrophytes while lettuce was most tolerant to Cu. Fish sensitivity toward the test chemicals was almost parallel to Ceratophyllum and Lemna [Gambusia affinis Baird and Gerard (LC₅₀: 250 ppb for Cu) and Poecilia reticulata Peters (LC₅₀: 24 ppm for methyl red)]. Similar to the plants, dye toxicity increased markedly (LC₅₀: 7 ppm) in the acidic medium (pH = 6.0). Amongst the tested organisms, Daphnia was found to be most sensitive to methyl red (EC₅₀: 6 ppm) while its sensitivity to Cu (EC₅₀: 230 ppb) was similar to hydrophytes and fish. Initially, the combination of dye and Cu (at their sublethal concentrations) had additive effects in duckweed, while dye concentration ruled afterward. These results indicate that hydrophytes and animals are equally sensitive toward the test chemicals. Dye toxicity in hydrophytes and fish was pH dependent, while in the case of Cu, it is related to the nutrient status of the growth medium of plants.