Toxicity Of Environmental Samples Research Articles

High-Efficiency Effect-Directed Analysis Leveraging Five High Level Advancements: A Critical Review.

Organic contaminants are ubiquitous in the environment, with mounting evidence unequivocally connecting them to aquatic toxicity, illness, and increased mortality, underscoring their substantial impacts on ecological security and environmental health. The intricate composition of sample mixtures and uncertain physicochemical features of potential toxic substances pose challenges to identify key toxicants in environmental samples. Effect-directed analysis (EDA), establishing a connection between key toxicants found in environmental samples and associated hazards, enables the identification of toxicants that can streamline research efforts and inform management action. Nevertheless, the advancement of EDA is constrained by the following factors: inadequate extraction and fractionation of environmental samples, limited bioassay endpoints and unknown linkage to higher order impacts, limited coverage of chemical analysis (i.e., high-resolution mass spectrometry, HRMS), and lacking effective linkage between bioassays and chemical analysis. This review proposes five key advancements to enhance the efficiency of EDA in addressing these challenges: (1) multiple adsorbents for comprehensive coverage of chemical extraction, (2) high-resolution microfractionation and multidimensional fractionation for refined fractionation, (3) robust in vivo/vitro bioassays and omics, (4) high-performance configurations for HRMS analysis, and (5) chemical-, data-, and knowledge-driven approaches for streamlined toxicant identification and validation. We envision that future EDA will integrate big data and artificial intelligence based on the development of quantitative omics, cutting-edge multidimensional microfractionation, and ultraperformance MS to identify environmental hazard factors, serving for broader environmental governance.

Methodological advances and future directions of microalgal bioassays for evaluation of potential toxicity in environmental samples: A review

Microalgal bioassays are widely applied to evaluate the potential toxicity of various persistent toxic substances in environmental samples due to multiple advantages, including high sensitivity, short test duration, and cost-effectiveness. Microalgal bioassay is gradually developing in method, and the scope of application to environmental samples is also expanding. Here, we reviewed the published literature on microalgal bioassays for environmental assessments, focusing on types of samples, sample preparation methods, and endpoints, and highlighted key scientific advancements. Bibliographic analysis was performed with the keywords ‘microalgae’ and ‘toxicity’ or ‘bioassay’, and ‘microalgal toxicity’; 89 research articles were selected and reviewed. Traditionally, most studies implementing microalgal bioassays focused on water samples (44%) with passive samplers (38%). Studies using the direct exposure method (41%) of injecting microalgae into sampled water mainly evaluated toxic effects by growth inhibition (63%). Recently, various automated sampling techniques, in situ bioanalytical methods with multiple endpoints, and targeted and non-targeted chemical analyses have been applied. More research is needed to identify causative toxicants affecting microalgae and to quantify the cause-effect relationships. This study provides the first comprehensive overview of recent advances in microalgal bioassays performed with environmental samples, suggesting future research directions based on current understanding and limitations.

Effects of conventionally-treated and ozonated wastewater on mortality, physiology, body length, and behavior of embryonic and larval zebrafish (Danio rerio)

To date, micropollutants from anthropogenic sources cannot be completely removed from effluents of wastewater treatment plants and therefore enter freshwater systems, where they may impose adverse effects on aquatic organisms, for example, on fish. Advanced treatment such as ozonation aims to reduce micropollutants in wastewater effluents and, thus, to mitigate adverse effects on the environment. To investigate the impact and efficiency of ozonation, four different water types were tested: ozonated wastewater (before and after biological treatment), conventionally-treated wastewater, and water from a river (River Ruhr, Germany) upstream of the wastewater treatment plant effluent. Zebrafish (Danio rerio) embryos were used to study lethal and sublethal effects in a modified fish early life-stage test. Mortality occurred during exposure in the water samples from the wastewater treatment plant and the river in the first 24 h post-fertilization, ranging from 12% (conventional wastewater) to 40% (river water). Regarding sublethal endpoints, effects compared to the negative control resulted in significantly higher heart rates (ozonated wastewater), and significantly reduced swimming activity (highly significant in ozonated wastewater and ozone reactor water, significant in only the last time interval in river water). Moreover, the respiration rates were highly increased in both ozonated wastewater samples in comparison to the negative control. Significant differences between the ozonated wastewater samples occurred in the embryonic behavior and heart rates, emphasizing the importance of subsequent biological treatment of the ozonated wastewater. Only the conventionally-treated wastewater sample did not elicit negative responses in zebrafish, indicating that the discharge of conventional wastewater poses no greater risk to embryonic and larval zebrafish than water from the river Ruhr itself. The sublethal endpoints embryonic- and larval behavior, heart rates, and respiration were found to be the most sensitive endpoints in this fish early life-stage test and can add valuable information on the toxicity of environmental samples.

DETERMINATION OF RICIN IN ENVIRONMENTAL SAMPLES USING BIOASSAY

A bioassay of ricin toxicity in environmental samples using real-time cell index monitoring is proposed. The halfmaximal inhibitory concentration (IC50) of ricin was estimated at 6,7 ng/ml for human hepatoma HepaRG cells proliferation. The antibodies to A- and B-subunits in HepaRG cell media lead to cytoprotective and antiapoptotic effects against the cytotoxicity of ricin. The antibodies neutralised activation of JNK kinase (phosphorylated at Thr183/Tyr185) and prevented accumulation of the active forms of caspase 8 (hydrolysed to Asp384) and caspase 9 (hydrolysed to Asp315) induced by ricin in HepaRG cells. The tested antibodies also prevented a decrease in the intracellular levels of the active forms of Akt 1 kinase (phosphorylated at Ser473) and transcription factor p53 (phosphorylated at Ser46) caused by ricin. The bioassay with antibodies can be considered as a specific method for identifying the toxin in environmental samples.

The Combined Algae Test for the Evaluation of Mixture Toxicity in Environmental Samples.

The combined algae test is a 96-well plate-based algal toxicity assay with the green algae Raphidocelis subcapitata that combines inhibition of 24-h population growth rate with inhibition of photosynthesis detected after 2 and 24 h with pulse-amplitude modulated (PAM) fluorometry using a Maxi-Imaging PAM. The combined algae test has been in use for more than a decade but has had limitations due to incompatibilities of the measurements of the 2 biological endpoints on the same microtiter plates. These limitations could be overcome by increasing growth rates and doubling times on black, clear-bottom 96-well plates by application of dichromatic red/blue light-emitting diode illumination. Different robotic dosing approaches and additional data evaluation methods helped to further expand the applicability domain of the assay. The combined algae test differentiates between nonspecifically acting compounds and photosynthesis inhibitors, such as photosystem II (PSII) herbicides. The PSII herbicides acted immediately on photosynthesis and showed growth rate inhibition at higher concentrations. If growth was a similar or more sensitive endpoint than photosynthesis inhibition, this was an indication that the tested chemical acted nonspecifically or that a mixture or a water sample was dominated by chemicals other than PSII herbicides acting on algal growth. We fingerprinted the effects of 45 chemicals on photosynthesis inhibition and growth rate and related the effects of the single compounds to designed mixtures of these chemicals detected in water samples and to the effects directly measured in water samples. Most of the observed effects in the water samples could be explained by known photosystem II inhibitors such as triazines and phenylurea herbicides. The improved setup of the combined algae test gave results consistent with those of the previous method but has lower costs, higher throughput, and higher precision. Environ Toxicol Chem 2020;39:2496-2508. © 2020 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Using Mutations for Pesticide Resistance to Identify the Cause of Toxicity in Environmental Samples.

Traditional Toxicity Identification Evaluations (TIE) are applied to identify causal agents in complex environmental samples showing toxicity and rely upon physical or chemical manipulation of samples. However, mutations conferring toxicant resistance provide the opportunity for a novel biologically based TIE. Populations within the Hyalella azteca complex from pesticide-affected waterways were 2 and 3 orders of magnitude more resistant to the pyrethroid cyfluthrin and the organophosphate chlorpyrifos, respectively, than laboratory-cultured H. azteca widely used for toxicity testing. Three resistant populations, as well as laboratory-cultured, nonresistant H. azteca, were exposed to urban and agricultural runoff. Every sample causing death or paralysis in the nonresistant individuals had no effect on pyrethroid-resistant individuals, providing strong evidence that a pyrethroid was the responsible toxicant. The lack of toxicity to chlorpyrifos-sensitive, but pyrethroid-resistant, individuals suggested chlorpyrifos was not a likely toxicant, a hypothesis supported by chemical analysis. Since these mutations that confer resistance to pesticides are highly specific, toxicity to wild-type, but not resistant animals, provides powerful evidence of causality. It may be possible to identify strains resistant to even a wider variety of toxicants, further extending the potential use of this biologically based TIE technique beyond the pyrethroid and organophosphate-resistant strains currently available.

Semivolatile and Volatile Compound Evolution during Pyrolysis and Combustion of Colombian Coffee Husk

Thermal characterization of coffee husk (Coffea arabica) from Colombian coffee has been studied. Different products, mostly volatile and semivolatile compounds, were analyzed, paying special attention to 16 polycyclic aromatic hydrocarbons (PAHs) classified by the United States Environmental Protection Agency (U.S. EPA) as priority pollutants, frequently used for checking toxicity in environmental samples. A fixed amount of raw material was exposed to different excess air ratios (λ = 0–2.33) and nominal temperature of 1123 K in a horizontal quartz reactor. The results show that coffee husk is a promising biomass for energetic exploitation with reduced formation of PAHs in a low air excess ratio. This implies reduction of carcinogenic potential in the limited presence of oxygen, demonstrated by calculating the carcinogenic potential (KE) for each experimental condition. Most volatile and semivolatile compounds followed different trends, with the oxygen presence prevailing their decomposition with increasin...

Quantification for total demethylation potential of environmental samples utilizing the EGFP reporter gene

The demethylation potential of pollutants is arguably an innate component of their toxicity in environmental samples. A method was developed for determining the total demethylation potential of food samples (TDQ). The demethylation epigenetic toxicity was determined using the Hep G2 cell line transfected with pEGFP-C3 plasmids containing a methylated promoter of the EGFP reporter gene. The total demethylation potential of the sample extracts (the 5-AZA-CdR demethylation toxic equivalency) can be quantified within one week by using a standard curve of the 5-AZA-CdR demethylation agent. To explore the applicability of TDQ for environmental samples, 17 groundwater samples were collected from heavy polluted Kuihe river and the total demethylation potentials of the sample extracts were measured successfully. Meaningful demethylation toxic equivalencies ranging from 0.00050 to 0.01747μM were found in all groundwater sample extracts. Among 19 kinds of inorganic substance, As and Cd played important roles for individual contribution to the total demethylation epigenetic toxicity. The TDQ assay is reliable and fast for quantifying the DNA demethylation potential of environmental sample extracts, which may improve epigenetic toxicity evaluations for human risk assessment, and the consistent consuming of groundwater alongside the Kuihe river pose unexpected epigenetic health risk to the local residents.

Pesticide Toxicity Index—A tool for assessing potential toxicity of pesticide mixtures to freshwater aquatic organisms

Pesticide mixtures are common in streams with agricultural or urban influence in the watershed. The Pesticide Toxicity Index (PTI) is a screening tool to assess potential aquatic toxicity of complex pesticide mixtures by combining measures of pesticide exposure and acute toxicity in an additive toxic-unit model. The PTI is determined separately for fish, cladocerans, and benthic invertebrates. This study expands the number of pesticides and degradates included in previous editions of the PTI from 124 to 492 pesticides and degradates, and includes two types of PTI for use in different applications, depending on study objectives. The Median-PTI was calculated from median toxicity values for individual pesticides, so is robust to outliers and is appropriate for comparing relative potential toxicity among samples, sites, or pesticides. The Sensitive-PTI uses the 5th percentile of available toxicity values, so is a more sensitive screening-level indicator of potential toxicity. PTI predictions of toxicity in environmental samples were tested using data aggregated from published field studies that measured pesticide concentrations and toxicity to Ceriodaphnia dubia in ambient stream water. C. dubia survival was reduced to ≤50% of controls in 44% of samples with Median-PTI values of 0.1–1, and to 0% in 96% of samples with Median-PTI values >1. The PTI is a relative, but quantitative, indicator of potential toxicity that can be used to evaluate relationships between pesticide exposure and biological condition.

Detection of tris-(2, 3-dibromopropyl) isocyanurate as a neuronal toxicant in environmental samples using neuronal toxicity-directed analysis

Neuronal toxic pollutants in environment possess hazards to human health. It is essential to determine the causative neuronal toxicants in environmental samples. In the present study, viability of primary cultured cerebellar granule neurons (CGNs), combined with sample extraction, chemical fractionation and identification, was applied for screening acid-resistant neuronal toxic substances in environmental samples. River sediments and agricultural soils along the river near a brominated flame retardant (BFR) manufacturing plant in South China were collected to screen the key neuronal toxicants. The results indicated that the manufacturing plant was a source of neuronal toxicity risks. In the sediment and soil near the plant, one of the causative toxicants was identified as tris-(2,3-dibromopropyl) isocyanurate (TBC) using HPLC-MS/MS. In addition, an unknown chemical possibly causing significant neuronal toxicity was isolated from all the soil samples in the region.

Sediment contact test with Potamopyrgus antipodarum in effect-directed analyses—challenges and opportunities

Effect-directed analysis is increasingly used for the identification of key toxicants in environmental samples and there is a growing need for in vivo biotests as diagnostic tools. Within this study, we performed an in vivo sediment contact test, applicable on both native field samples and their extracts or fractions, in order to be able to compare the results from both field and laboratory studies. A sediment contact test with the prosobranch snail, Potamopyrgus antipodarum, was carried out on extracts and fractions of field sediments from three European river basins. The results were compared with previous results of the native field samples. In contrast to the native sediments, the extracts of the samples led to an overall decrease in reproduction. Even the chosen reference sites had an adverse effect on the snails' reproduction. It appeared that a higher bioavailability in the organic extracts, together with a changing composition of compounds could have lead to this change in effects. The fractionation of the extracts partly led to a more differentiated picture, but the resolution was not high enough to see any distinct effects on the snails' reproduction. Our results highlight the importance of the use of in vivo biotests and point out the relevance of bioavailability in native sediments. For further fractionation studies, a more realistic extraction procedure, together with a higher resolution fractionation, would be appropriate in order to separate individual bioavailable compounds more efficient.

Focused toxicity identification evaluations to rapidly identify the cause of toxicity in environmental samples

Over the past 5 years numerous toxicity studies in California using the amphipod, Hyalella azteca, have reported that pyrethroid insecticides, and less frequently the organophosphate insecticide chlorpyrifos, have been responsible for observed toxicity. As work continues to characterize and mitigate these water quality impacts, an approach is needed to screen samples exhibiting toxicity quickly and cost-effectively to establish if these same substances are again responsible, or if other, more atypical toxicants are responsible. Causality is often determined by a standard toxicity identification evaluation (TIE), but when there is strong historical evidence of a likely toxicant, we propose use of a focused TIE procedure to screen samples using manipulations specifically designed to identify pyrethroid- or chlorpyrifos-related toxicity. The focused tests use reduced temperature, piperonyl butoxide addition, and engineered enzymes specifically designed to hydrolyze certain pyrethroid and organophosphate insecticides. The target compounds exhibit unique response profiles to this battery of manipulations, distinct from each other and other non-insecticides. When used in conjunction with analytical chemistry data, the focused approach was successful in identifying cause of toxicity in a variety of urban and agricultural settings.

Optimization of Bacterial Whole Cell Bioreporters for Toxicity Assay of Environmental Samples

In a study to optimize bacterial whole cell biosensors (bioreporters) for the detection of environmental contaminants, we constructed a toxicity sensing strain Acinetobacter baylyi ADP1_recA_lux. The ADP1_recA_lux is a chromosomally based bioreporter which makes the sensing system stable and negates the need for antibiotics to maintain the trait. The AOP1_recA_lux is activated to express bioluminescence when it is exposed to DNA damaging toxicants. Since the ADP1_recA_lux constantly expresses a baseline level of bioluminescence, false negative results are avoided. The host strain, A. baylyi ADP1, is an ideal model strain typical of water and soil bacteria occurring in the natural environment, and it is more robust than E. coli in terms of viability, maintenance, and storage. The expression of reporter genes - luxCDABE cloned from Photorhabdus luminescens - is robust in a broad range of temperature (10-40 degrees C). The ADP1_recA_lux was used to detect a variety of toxic or potentially toxic compounds including mitomycin C (MMC), methyl methanesulfonate, ethidium bromide, H2O2, toluene, single-wall nanocarbon tubes (SWNCT), nano Au colloids (20 nm), pyrene, beno[a]pyrene, and UV light. These exposures revealed that the ADP1_recA_lux was able to detect both genotoxicity and cytoxicity, qualitatively and quantitatively. The optimal induction time of the ADP1_recA_lux bioreporter was 3 h, and the detection limits for MMC and benezo[a]pyrene were 1.5 nM and 0.4 nM, respectively. The ADP1_recA_lux was also used to detect toxicity of groundwater contaminated by a mixture of phenolic compounds, and the bioreporter toxicity detection was in a good agreement with chemical analysis. The optimized whole cell bioreporter ADP1_recA_lux could be valuable in providing a simple, rapid, stable, quantitative, robust, and costly efficient approach for the detection of toxicity in environmental samples.

Rainbow Trout (Oncorhynchus mykiss) and Brook Trout (Salvelinus fontinalis) 7-Day Survival and Growth Test Method

A short-term method was developed in this study for conducting subchronic survival and growth renewal toxicity tests with rainbow trout (Oncorhynchus mykiss) and brook trout (Salvelinus fontinalis). Previously published early life-stage methods for various salmonid species involve test durations of 30 to 90 days. This trout method, however, follows a previously published 7-day fathead minnow (Pimephales promelas) growth method. The tests performed in this study measured subchronic growth and survival effects using standard reference toxicants (ammonium chloride, potassium chloride, phenol, and zinc sulfate), receiving water, and effluent samples. The test results were compared with performance criteria and results for 7-day survival and growth tests with P. promelas to determine the level of comparability between the two species. The results from tests with both salmonid species indicated that this 7-day survival and growth test method using O. mykiss and S. fontinalis provides reproducible results with various reference toxicant materials and can be used successfully to detect potential toxicity in environmental samples.

Chlorophyll a fluorescence as a biomarker for rapid toxicity assessment

Algal growth assays are the most frequently used methods to detect herbicide toxicity in environmental samples; however, these require several days to detect reductions in growth rate with adequate precision. Hence, a need exists for more rapid assays. Two in vivo chlorophyll a fluorescence assays, one using pulse-amplitude modulation (PAM) fluorescence and another based on fluorescence at 684 and 735 nm, detect the effects of photosystem (PS) II inhibitors (atrazine, diuron, and isoproturon) on Selenastrum capricornutum Printz only after 1 h and 30 min, respectively, of incubation. The median growth inhibition (IC50) could be predicted reliably from effects on three PAM parameters--maximal PSII quantum yield (phi(m)), operational quantum yield (phi'(m)), and nonphotochemical quenching--and from measurements of fluorescence at 684 and 735 nm. The effects of the PSI inhibitor paraquat dichloride, were smaller in magnitude and could be detected after a 24-h incubation. These two in vivo chlorophyll a fluorescence assays can thus provide reliable, rapid, and cost-effective tools to screen toxicity caused by PSII inhibitors. Neither of the two fluorescence assays could consistently predict the effects of nonphotosynthetic inhibitors (alachlor, metsulfuron methyl, and diclofop methyl).

A new approach based on polynomial functions for measuring the acute toxicity of environmental samples

In this paper, a new mathematical approach for the estimation of acute toxicity in environmental samples is proposed. The concentration of pollutant or the amount of sample producing the inhibition of 50% of the living organisms used for the test (EC50) is determined by means of Polynomial Functions (PF) applied to the experimental x (concentration of pollutant) and y (concentration or number of living organisms) points instead of using the common approach by Exponential Regression Analysis (ERA). The peculiar characteristic of the proposed method is its ability to describe the dose–response relationship of a pollutant including both growing (i.e. hormetic) and lethal effects, without requiring the exclusion of hormetic points that do not obey to the exponential relationship of a lethal response. For this reason, PF approach is proposed as an alternative method to the common estimation of EC50 by ERA method. The use of PF approach is described reporting advantages and disadvantages with respect to the conventional ERA method.

Potential application of carbonic anhydrase activity in bioassay and biomarker studies

Carbonic anhydrase (CA) (EC 4.2.1.1), a ubiquitous enzyme in bacteria, plant, and animal kingdoms, catalyses the reversible hydration of CO2 to produce H+ and using zinc as cofactor. CA plays a fundamental role in a number of physiological processes, such as respiration, ionic transport, acid–base regulation, and calcification. The aim of the present work was to investigate the sensitivity of this enzyme to heavy metals with a view to possible future applications of CA activity inhibition measurement in biomonitoring as either an in vitro bioassay or a biomarker. CA activity was determined by modifying a previously described electrometric method: briefly, CA activity units were calculated from the rate of H+ production in the reaction mixture (where CO2 was present as a substrate) against a blank containing the specific CA inhibitor acetazolamide. As regards the possible application as an in vitro bioassay, the sensitivity to heavy metals (cadmium, mercury, and copper) of the commercially available purified carbonic anhydrase (isozyme II) from bovine erythrocyte was tested in vitro. In our experimental set-up, bovine CA activity was significantly inhibited by micromolar concentrations of heavy metals, showing a dose–response behaviour. As regards the possible application as biomarkers, CA was investigated in the filter-feeding Mytilus galloprovincialis, widely used in pollution-monitoring programmes as a sentinel organism. Following in vitro and in vivo exposure to 1.785 μM cadmium chloride as a reference toxicant, mantle CA activity was significant inhibited. In conclusion, the sensitivity to chemical pollutants and low cost and simplicity of the assay method make CA activity measurement suitable for in vitro bioassay of the toxicity of environmental samples and for field biomarker applications in the sentinel organism M. galloprovincialis.

Avaliação do efeito das águas superficiais dos estuários dos rios Camboriú e Itajaí-açú sobre o crescimento da diatomácea Skeletonema costatum

The Itajai-Acu and Camboriu rivers are the main important water suppliers for domestic and agroindustrial use in Itajai and Balneario Camboriu cities in southeastern coast of Brazil. The waste dispoasal by human activities in these estuaries may result in poor water quality and even prevent its use for these activities. In order to evaluate the effects of the human activities upon the estuaries water quality, this study was carried out to evaluate and compare the surface water quality in both estuaries, using a toxicological bioassay to mesure the effect of these waters in growth of marine microalgae Skeletonema costatum (Bacillariophyceae). The samples were colletcted from august of 2003 to march of 2004 in every two weeks at CEPSUL/IBAMA pier (in Itajai-Acu estuary) and turistic pier (in Camboriu estuary). The physical and chemical characteristics of the samples were determined in situ. The samples were taken to laboratory and frozen for further use. After conducing the bioassay, the results show an increase in algal growth due to excess of nutrients in the samples of both estuaries. This result indicates water eutrophication, as reported in other studies. No effect in the growth of the species was observed for the samples collected in summer months. The samples of march of 2004 from Camboriu estuary were toxic to S. costatum. This result may be due to the disposal of treated wastewater from Balneario Camboriu wastewater treatment plant in the surface river water. The observed concentration effect (CEO) obtained for the samples of march were almost 50%. The CE50 calculated was 96,17% for one sample of march. In the present work, the use of microalgae toxicity test for mesure toxicity in environmental samples and its use as water eutrophication indicator were confirmed.

Carbonic anhydrase-based environmental bioassay

Carbonic anhydrase (CA) is a metalloenzyme catalysing the reversible idratation of CO2 in H+ and . It is an ubiquitous enzyme in bacteria, plant and animal kingdoms, playing a fundamental role in a number of physiological processes. Previous studies demonstrated the sensitivity of CA activity to dichlorodiphenyl-dichloroethane (DDT) exposure in birds and to cadmium exposure in teleosts. The aim of the present work was to develop a new in vitro enzymatic bioassay for detecting toxic chemicals in environmental samples as a cost-effective tool in environmental monitoring. This bioassay uses the commercial available CA isozyme II from bovine erythrocytes whose sensitivity to the main classes of chemical pollutants of importance in water quality research was tested in this work. CA activity was determined by a modification of the electrometric method previously described by Wilbur and Anderson [K.M. Wilbur, G.N. Anderson. J. Biol. Chem., 176, 147 (1948).]: briefly, CA activity units were calculated from the rate of H+ production in the reaction mixture (where CO2 was present as substrate) against a blank containing the specific CA inhibitor acetazolamide. [H+] variation was followed at 0°C in the reaction mixture using a Mettler Delta 350 pH-meter. In our experimental set-up bovine CA activity was significantly inhibited by heavy metals (Cd, Cu and Hg), by the organochlorate compound arochlor and by the carbammate pesticides carbaryl in a dose-dependent manner. CA in vitro bioassay can represent a novel tool for rapid and low cost understanding of the toxicity of environmental samples, for assessing bioavailability of pollutants in environmental matrices and their additive or synergistic biological effects when present in mixtures.

Assessment of the Geochemical Role of Colloids and Their Impact on Contaminant Toxicity in Freshwaters: An Example from the Lambro−Po System (Italy)

The role of colloids in regulating element transport, behavior, and bioavailability in aquatic systems is now well-established. It appears that further progress in this research field is being slowed by (i) a limited integration between the geochemical and the biological aspects of the research on colloids and (ii) a persistent gap between well-controlled laboratory studies and real field situations. This paper presents a simultaneous evaluation of the role of colloids in controlling element environmental fate and bioavailability at the confluence between a major river and a polluted tributary. Fractionation of trace elements among suspended particulate matter, colloids, and true solution suggests that colloids may play a role in the removal of trace elements from the water column to bed sediments during the mixing of the two rivers. Toxicity testing of water samples indicates that, in this specific system, contaminants associated with colloids can contribute to water toxicity for the rotifer Brachionus calyciflorus but not for the green alga Pseudokirchneriella subcapitata. To the best of our knowledge, the results for B. calyciflorus are the first ones pointing to the possible contribution of colloid-bound contaminants to water toxicity in environmental samples. Despite the uncertainties associated with field variability, the results of chemical analysis and toxicitytesting show several points of convergence. Following these observations, a few innovative research approaches are suggested to improve the understanding of trace element biogeochemistry in real field situations.