Toxicity and genotoxicity assessment in sediments from the Matanza-Riachuelo river basin (Argentina) under the influence of heavy metals and organic contaminants

Prospecting toxicity of the avobenzone sunscreen in plants

Avobenzone (AVO) is a sunscreen with high global production and is constantly released into the environment. Incorporating sewage biosolids for fertilization purposes, the leaching from cultivated soils, and the use of wastewater for irrigation explain its presence in the soil. There is a lack of information about the impact of this sunscreen on plants. In the present study, the ecotoxicity of AVO was tested at concentrations 1, 10, 100, and 1,000 ng/L. All concentrations caused a reduction in root growth of Allium cepa, Cucumis sativus, and Lycopersicum esculentum seeds, as well as a mitodepressive effect, changes in the mitotic spindle and a reduction in root growth of A. cepa bulbs. The cell cycle was disturbed because AVO disarmed the enzymatic defense system of root meristems, leading to an accumulation of hydroxyl radicals and superoxides, besides lipid peroxidation in cells. Therefore, AVO shows a high potential to cause damage to plants and can negatively affect agricultural production and the growth of non-cultivated plants.

Toxicity of the emerging pollutants propylparaben and dichloropropylparaben to terrestrial plants

Propylparaben (PrP) and dichloropropylparaben (diClPrP) are found in soil worldwide, mainly due to the incorporation of urban sludge in crop soils and the use of non-raw wastewater for irrigation. Studies on the adverse effects of PrP on plants are incipient and not found for diClPrP. PrP and diClPrP were evaluated at concentrations 4, 40, and 400 µg/L for their phytotoxic potential to seeds of Allium cepa (onion), Cucumis sativus (cucumber), Lycopersicum sculentum (tomato), and Lactuca sativa (lettuce), and cytotoxic, genotoxic potential, and for generating oxygen-reactive substances in root meristems of A. cepa bulbs. PrP and diClPrP caused a significant reduction in seed root elongation in all four species. In A. cepa bulb roots, PrP and diClPrP resulted in a high prophase index; in addition, PrP at 400 µg/L and diClPrP at the three concentrations significantly decreased cell proliferation and caused alterations in a significant number of cells. Furthermore, diClPrP concentrations induced the development of hooked roots in onion bulbs. The two chemical compounds caused significant changes in the modulation of catalase, ascorbate peroxidase, and guaiacol peroxidase, disarming the root meristems against hydroxyl radicals and superoxides. Therefore, PrP and diClPrP were phytotoxic and cytogenotoxic to the species tested, proving dangerous to plants.

Benzophenone-3 sunscreen causes phytotoxicity and cytogenotoxicity in higher plants

The benzophenone-3 (BP-3) sunscreen is recurrently released into the environment from different sources, however, evaluations of its adverse effects on plants do not exist in the literature. In this study, BP-3 was evaluated, at concentrations 2; 20, and 200 µg/L, regarding phytotoxicity, based on germination and root elongation in seeds, in Lactuca sativa L., Cucumis sativus L. and Allium cepa L., and phytotoxicity, cytogenotoxicity and oxidative stress in A. cepa bulb roots. The BP-3 concentrations, except for the 200 µg/L concentration in L. sativa, caused no significant reduction in seed germination. All concentrations tested significantly reduced the elongation of roots from seeds and roots from bulbs. The 20 and 200 µg/L concentrations caused oxidation in cells, disturbances in the cell cycle, and alterations in prophase and metaphase, as well as the induction of micronuclei, in A. cepa root meristems. Furthermore, the three concentrations induced a high number of prophases in root tips. Such disorders were caused by excess H2O2 and superoxide produced in cells due to exposure to BP-3, which triggered significant phytotoxicity, cytotoxicity, and genotoxicity in root meristems. Thus, the recurrent contamination of agricultural and non-agricultural soils with BP-3, even at a concentration of 2 µg/L, represents an environmental risk for plants. These results point to the impending need to set limits for the disposal of this sunscreen into the environment since BP-3 has been used in industry for several decades.

Intra- and inter-annual variations in metal concentrations in the superficial water of a highly polluted urban basin of Argentina

To protect ecosystems impacted by human activities and prevent their degradation, it is imperative to evaluate variations in the concentration of environmental pollutants over time. Here, we evaluated the intra- and inter-annual variations of several metals from 15 sites in the Matanza Riachuelo River basin (one of the most polluted in the world) and determined the physicochemical and meteorological parameters associated with these changes from 2008 to 2015. For this, in each site, we used Asymmetric Eigenvector Maps and Redundancy Analysis. The results highlighted temporal patterns of metal concentrations and several factors associated with them, perhaps related to the actions performed in the area since 2008. Additionally, we found that the effects of physicochemical and meteorological factors on metal concentrations were site-dependent, possibly related to the presence of different local sources of pollution or characteristics of the river in each site, such as its sediments. This approach could be applied to different scenarios (aquatic and terrestrial) and could provide a tool to help decision-makers address the harmful consequences of the continuous advance of human activities on human and ecosystem health.

Copper, zinc, and chromium accumulation in aquatic macrophytes from a highly polluted river of Argentina

The aims of this study were to assess Cu, Zn, and Cr pollution in a highly polluted river in Argentina (Matanza-Riachuelo) and to evaluate tolerance strategies and toxic effects in aquatic macrophytes. Chemical techniques were used to assess the bioavailability of these metals and to evaluate their uptake and translocation by plants. The ultrastructure of the roots of a free-floating plant (Eichhornia crassipes) and the leaves of an emergent macrophyte (Sagittaria montevidensis) was examined using transmission electron microscopy. In the lower basin of the river, the highest concentrations of total heavy metals were detected in water (179 µgZn/g; 54 µgCu/g; 240 µgCr/g) and sediments (1499 µgZn/g; 393 µgCu/g; 4886 µgCr/g). In the upper basin of the river, low percentages of Zn and Cu (8 to 25%) were extracted with DTPA and EDTA, probably due to the lithogenic origin of these metals. Higher extraction percentages (24 to 66%) were obtained in the lower basin, in accordance with anthropogenic pollution. For Cr, extraction percentages were low in the upper basin of the river (< 4.5%) and extremely low in the lower basin (< 0.03%). In S. montevidensis, the BCF (bioconcentration factor) and TF (translocation factor) indexes were compatible with heavy metal exclusion mechanisms in sediments, whereas in the E. crassipes, root compartmentalization could be the main tolerance strategy. The leaves of S. montevidensis showed no evidence of damage, whereas ultrastructural alterations (plasmolyzed cells, disorganized membranes) were observed in E. crassipes.

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.

Prospecting toxicity of octocrylene in Allium cepa L. and Eisenia fetida Sav

Octocrylene sunscreen is found in different environmental compartments. Unlike aquatic organisms, there are few studies evaluating the adverse effects caused by this pollutant on terrestrial plants, and no studies on soil fauna. In this study, octocrylene was evaluated at concentrations of 10, 100, and 1000 µg/L for phytotoxicity, cytogenotoxicity, and oxidative stress in Allium cepa L., and acute toxicity and oxidative stress in Eisenia fetida Sav. In A. cepa, at concentrations of 100 and 1000 µg/L, octocrylene reduced the germination potential in seeds, inhibited root elongation, and caused disturbance in cell division in roots. In E. fetida, the concentration of 1000 µg/L promoted an avoidance rate of 80%, while 10 µg/L caused a hormesis effect. The concentrations 100 and 1000 µg/L caused lipid peroxidation in A. cepa and E. fetida. Based on the results, the recurrent use of biosolids in soil fertilization, as well as the irrigation of plants with wastewater, with the presence of octocrylene can negatively impact the survival of different species that depend directly or indirectly on the soil.

Distinct structural strategies with similar functional responses of abundant and rare subcommunities regarding heavy metal pollution in the Beiyun river basin

Bacteria within a metacommunity could be partitioned into different subcommunities ecological assemblages in light of potential importance for the community function. It is unknown how abundant and rare microbial subcommunities in urban river sediments respond to heavy metal pollutants. Using high-throughput sequencing, we analyzed these response patterns in the heavliy polluted (Beijing, China). We found that this river faces substantial ecological risks, owing to high rates of Cd and Hg pollution from urban activities. Surprisingly, abundant and rare subcommunity structures showed opposite responses to heavy metals. Abundant taxa, such as Crenarchaeota and Euryarchaeota, are resistant to heavy metal pollution through the synergistic of ammonia nitrogen (NH₄⁺-N) and total phosphorus (TP). By contrast, rare taxa, such as Verrucomicrobia, Fibrobacteres, Berkelbacteria, and Euryarchaeota, had a high synergy with NH₄⁺-N and TP with high a resilience to heavy metal pollution. However, the functions of both abundant and rare subcommunities showed a similar response to heavy metal pollutants, especially in denitrification processes. The abundant taxa responded to heavy metal pollution through methanogenesis by CO₂ reduction with H₂, human pathogens nosocomia, sulfate respiration, photoheterotrophy, and dark sulfide oxidation synergy with NH₄⁺-N and TP. The rare taxa responded to heavy metals through methanogenesis by CO₂ reduction with H₂, cellulolysis, sulfate respiration, intracellular parasites, nitrate reduction and plant pathogen. We observed distinct patterns between the structural and functional responses of microbial subcommunities to heavy metal pollutants. Our findings support the concept that denitrification processes are sensitive to but not inhibited by high levels of heavy metals pollution. We propose that the structures and functions of the abundant and rare microbial subcommunities could inform the management of pollutants in heavily polluted urban river ecosystems at fine geographical scales.

Mixture of Toxic Metals and Volatile Organic Compounds in a River Induces Cytotoxicity

Pollution of aquatic ecosystems due to toxic mixtures is a worldwide problem associated with the increase of wastewater discharges that causes problems to human health and biodiversity. This study aims to evaluate the cytotoxic potential of water from the Atoyac River. Meristems of Allium cepa L. were exposed to water samples from the Atoyac River with different concentrations for 120 hours. Pearson correlation was used to investigate the relationship between contaminants and cytotoxicity. The results corroborated the cytotoxic effect of the mixture of agents such as toxic metals and volatile organic compounds found in all river sampling sites. The Allium cepa test showed decreased mitotic alterations in prophase and metaphase indices. There was a strong negative association between the concentration of toxic metals and volatile organic compounds and the cytotoxic effect. The observations of cytotoxic effects show that the contaminant mixture contains aneugenic agents which prevent the synthesis and fixation of fibers of the mitotic spindle to the kinetochore, which prevents the displacement of the chromosomes. This study shows the need to study the effects at the cellular and molecular level in heavily polluted rivers to prevent negative effects on exposed ecosystems and populations.

Application of a phosphonium-based ionic liquid for reactive textile dye removal: Extraction study and toxicological evaluation

Textile dyeing processes are known for their negative environmental impacts due to the production of aqueous effluents containing toxic dyes. Therefore, new wastewater treatment processes need to be developed to treat such effluents, including Liquid-Liquid Extraction (LLE) process using Ionic Liquids (IL). This work aimed to evaluate the application of the hydrophobic IL trihexyltetradecylphosphonium decanoate to extract black, navy, and royal reactive dyes from water and evaluate the toxicological aspects of the resulting water stream. We investigated the effect of selected parameters, such as pH (2-12), temperature (20-50 °C), salt effects, dye concentration (0.5-50 mg/L), and phase volume ratio (900-9000) on the dye extraction. The results showed extraction yields as high as 97% for the three dyes and an extraction capacity of approximately 300 mg/g for black and navy dyes and 400 mg/g for royal. The toxicity tests involved Lactuca sativa, Triticum aestivium L, and Daphnia magna as bioindicators. The difference between the toxicity of the dye solutions before and after extraction was not statistically significant when L. sativa and Triticum aestivum L were used as bioindicators. However, the extracted solution showed increased toxicity towards D. magna due to traces of IL. Overall, the IL has a high extraction capacity for the black, navy, and royal dyes. Nevertheless, further studies on LLE associated with other processes must be carried out to reduce the risk linked to the toxicity of IL transferred to the water.

Impacts of urban and industrial pollution on functional traits of benthic macroinvertebrates: Are some traits advantageous for survival?

Urbanization and industrialization produce substantial changes in biodiversity and in the functionality of ecosystems. However, little is known about how anthropic pressures might drive these changes and about their functional consequences. We aimed to determine the responses of macroinvertebrate biological traits to urban and industrial pollution and assess the impacts of these disturbances on the functional diversity of these assemblages. We sampled benthic macroinvertebrates in 27 sites of four basins with different urban disturbance gradients (rural, peri-urban, and urban-industrial), among them the Matanza-Riachuelo River, one of the most polluted basins in the world. We classified macroinvertebrates into 11 traits and 56 categories. Then, we performed an RLQ analysis and computed functional richness, evenness, divergence and Rao diversity indexes for each site and community weighted means for each trait category. The urban and industrial sites (mainly low and middle Matanza-Riachuelo River Basin) showed high concentrations of ammonium, SRP, conductivity, COD, BOD, and organic matter, as well as the lowest values of DO. The functional richness and Rao index of these sites were significantly lower than that of the other sites. Macroinvertebrate traits associated with urban and industrial sites were aerial respiration (spiracles), forms of resistance (eggs or statoblast), cylindrical body shape, oviparity, feeding on microinvertebrates, and full water swimmers. These traits potentially enabled tolerant species persistence at polluted sites while gills, grazers, and crawlers were sensitive to these disturbances. Urban and industrial activities influence biological traits, producing the disappearance or dominance of certain traits in macroinvertebrate assemblages. As a consequence, extreme pollution caused predictable trait-based community changes resulting in reduced functional diversity, and potentially altered the ecosystem function.

Assessing the genotoxic potential of freshwater sediments after extensive rain events - Lessons learned from a case study in an effluent-dominated river in Germany

Wastewater treatment plant effluents and releases from rainwater overflow basins can contribute to the input of genotoxic micropollutants in aquatic ecosystems. Predominantly lipophilic genotoxic compounds tend to sorb to particulate matter, making sediment a source and a sink of pollution. Therefore, the present study aims to investigate the genotoxic potential of freshwater sediments (i) during the dry period and (ii) after extensive rain events by collecting sediment samples in one small anthropogenically impacted river in Germany up- and downstream of the local wastewater treatment plant. The Micronucleus and Ames fluctuation assays with Salmonella typhimurium strains TA98, TA100, YG1041, and YG1042 were used to assess the genotoxic potential of organic sediment extracts. For evaluation of possible genotoxicity drivers, target analysis for 168 chemical compounds was performed. No clastogenic effects were observed, while the genotoxic potential was observed at all sampling sites primarily driven by polycyclic aromatic hydrocarbons, nitroarenes, aromatic amines, and polycyclic heteroarenes. Freshwater sediments' genotoxic potential increased after extensive rain events due to sediment perturbation and the rainwater overflow basin release. In the present study, the rainwater overflow basin was a significant source for particle-bound pollutants from untreated wastewater, suggesting its role as a possible source of genotoxic potential. The present study showed high sensitivity and applicability of the bacterial Salmonella typhimurium strains YG1041 and YG1042 to organic sediment extracts to assess the different classes of genotoxic compounds. A combination of effect-based methods and a chemical analysis was shown as a suitable tool for a genotoxic assessment of freshwater sediments.

Integrating multiple lines of evidence to assess freshwater ecosystem health in a tropical river basin

Degradation of freshwater ecosystems by uncontrolled human activities is a growing concern in the tropics. In this regard, we aimed at testing an integrative framework based on the IFEQ index to assess freshwater ecosystem health of river basins impacted by intense livestock and agricultural activities, using the Muchacho River Basin (MRB) as a case study. The IFEQ combine multiple lines of evidence such as riverine hydromorphological analysis (LOE 1), physicochemical characterization using ions and pesticides (LOE 2), aquatic macroinvertebrate monitoring (LOE 3), and phytotoxicological essays with L. sativa (LOE 4). Overall, results showed an important reduction in streamflow and an elevated increase in ion concentrations along the MRB caused by deforestation and erosion linked to agricultural and livestock activities. Impacts of the high ion concentrations were evidenced in macroinvertebrate communities as pollution-tolerant families, associated with high conductivity levels, represented 92 % of the total abundance. Pollution produced by organophosphate pesticides (OPPs) was critical in the whole MRB, showing levels that exceeded 270-fold maximum threshold for malathion and 30-fold for parathion, the latter banned in Ecuador. OPPs concentrations were related to low germination percentages of Lactuca sativa in sediment phytotoxicity tests. The IEFQ index ranged from 44.4 to 25.6, indicating that freshwater ecosystem conditions were "bad" at the headwaters of the MRB and "critical" along the lowest reaches. Our results show strong evidence that intense agricultural and livestock activities generated significant impacts on the aquatic ecosystem of the MRB. This integrative approach better explains the cumulative effects of human impacts, and should be replicated in other basins with similar conditions to help decision-makers and concerned inhabitants generate adequate policies and strategies to mitigate the degradation of freshwater ecosystems.

Evaluation of the sequential coupling of a bacterial treatment with a physicochemical process for the remediation of wastewater containing Cr and organic pollutants

A restoration strategy was developed for the treatment of two artificial liquid systems (Minimal Medium, MM, and Water Carbon Nitrogen, WCN) contaminated with Cr(VI), lindane (γ-HCH), phenanthrene (Phe), and reactive black 5 (RB5), through the use of an actinobacteria consortium, coupled with a physicochemical treatment using a column filled with nano-scale zero valent iron particles immobilized on dried Macrocystis pyrifera algae biomass. The Sequential Treatment A (ST_A: physicochemical followed by biological method) removed the three organic compounds with different effectiveness; however, it was very ineffective for Cr(VI) removal. The Sequential Treatment B (ST_B: biological followed by the physicochemical method) removed the four compounds with variable efficiencies. The removal of γ-HCH, Phe, and RB5 in both effluents did not present significant differences, regardless of the sequential treatment used. The highest removal of Cr(VI) and total Cr was observed in MM and WCN, respectively. Ecotoxicity tests (L. sativa) of the effluents treated with both methodological couplings demonstrated that the toxicity of WCN only decreased at the end of ST_A, while that of MM decreased at all stages of both sequential treatments. Therefore, MM would be more appropriate to perform both treatments.

Evaluation of heavy metal contamination levels in river sediments and their risk to human health in urban areas: A case study in the Matanza-Riachuelo Basin, Argentina

Anthropogenic contamination of Cd, Cr, Cu, Ni, Pb and Zn in riverbed sediments of the Pampean area (Matanza-Riachuelo Basin, MRB), Argentina, was evaluated using various indices: Geo-accumulation Index (Igeo), Contamination Factor (Cf), Metal Pollution Index (MPI), Pollution Load Index (PLI) and Contamination Degree (Cdeg). A database based on previous samplings of heavy metal concentrations at different sites in the Upper, Middle and Lower MRB was used. The Igeo and Cf values are calculated using selected local background (Pristine Pampean loess, LZB), and global average shale values (ASTW). Paired Igeo and Cf results with LZB and ASTW fall in dissimilar classes, especially in respect of Cd. In turn, MPI, PLI and Cdeg show similar results, as they do not have the same degree of confidence as Igeo and Cf. The Upper Basin, mainly rural, shows the following profile of sediment contamination: Cd > Ni > Cu ≫ Pb > Zn > Cr. The Middle Basin, which is at the periphery of a very industrialised and urban area, displays the following contamination profile for both Igeo and Cf: Cu > Pb > Zn > Ni > Cd > Cr. Conversely, in the Lower Basin, where land-use is urban/industrial, the levels of metal contamination are higher and appear in this order: Cr > Pb > Cu > Zn > Ni > Cd. Cadmium, Cu, Ni and Zn have shown no significant oral and/or dermal HQ nor carcinogenic risk but the potential risk posed by Cr and Pb must be taken into account. Maximum and mean values of Cr total carcinogenic risk (TCR) as well as Ni TCR also point to a health risk to children in the Lower Basin Area. All the data analysed confirm that industrial and urban growth without land-use planning, and a poor environmental legislation until the beginning of the 21st century, have not provided the necessary framework for sustainable development in the MRB.

Spatial Distribution and Ecological Risk Assessment of Heavy Metals in Sediments of a Heavily Polluted Maozhou River, Southern China

In this study, eighteen 3.30-m-long sediment profiles were sampled in Maozhou River. In order to investigate the sediment pollution status and potential sources of heavy metals, we performed heavy metal contents, grain size, organic matter concentration, moisture concentration and total phosphorus analysis, and assessed the ecological risk of heavy metal pollution in the study area using enrichment coefficient, geo-accumulation index and potential ecological risk index. The results indicated that the heavy metal concentrations in the Maozhou River sediments were 3.73-417 times higher than the soil background in Guangdong Province and the average concentrations were 0.447-15.1 times higher than Chinese lacustrine sediments. The Cr, Ni, Cu, Zn, Cd and Pb contents were significantly correlated with each other (p < 0.01), indicating similar deposition process. In addition, spatial and vertical distribution of heavy metals showed similar variation patterns and extreme high contents are distributed in the interchange area. The ecological risk of Maozhou River was much higher than other river sediments in Guangdong Province, especially for Cu, Cd and Ni. The variation pattern of potential ecological risk index is similar with that of heavy metals and the assessment results indicated high ecological risk in the Maozhou River sediments, which is in good agreement with the EF and I_geo results. This study would provide some references for the treatment of heavy metals' pollution in Maozhou River.

Assessment of the genotoxicity of sediment elutriates from an aquatic ecosystem on Allium cepa: Limache stream in central Chile

The aim of this study was to assess the genotoxic effects of sediment elutriates of an aquatic ecosystem. Sediment samples were taken from Limache stream, located in central Chile. The tests were carried out on sediment elutriates. Genotoxicity was determined by bioassay with Allium cepa. The percentage of germination, root growth, mitotic index, and frequency of chromosome aberrations were determined. The results show a significant increase in chromosome aberrations and decrease of the mitotic index in Allium cepa in all the sediment elutriates compared to the control. No significant differences were observed in the percentages of germination or root growth among the sediment elutriates. A negative correlation was found between the mitotic index and chromosomal aberrations. In conclusion, genotoxic variables are more sensitive than growth variables. The sediments contain chemical agents in bioavailable concentrations that produce genotoxic effects. Allium cepa test proved to be a sensitive indicator of genotoxic contaminants in sediment elutriates of the Limache stream in central Chile.

Co-occurrence of and risk factors for Cryptosporidium and Giardia in brown rats from Buenos Aires, Argentina

A rodent survey was conducted in different landscape units of the city of Buenos Aires (Argentina) to determine the prevalence of Cryptosporidium and Giardia in Rattus norvegicus and to, ultimately, assess the biotic, environmental and meteorological factors that explain the variations of the likelihood of infection for both parasites in an urban environment. The results of this study revealed a ubiquitous presence of Cryptosporidium and Giardia in R. norvegicus within an urban environment with the likelihood of infection depending on environmental and meteorological conditions for both parasites. The overall prevalence was greater for Cryptosporidium (p = 50.4%) than for Giardia (20.3%). The prevalence for both parasites separately was higher in parks compared to shantytowns and scrap metal yards. Generalized Linear Mixed Models revealed that the occurrence of these parasites separately, at an individual level, was positively related with rainfall variables and that the effect of temperature depended on the landscape unit. The similarities in the transmission modes, which are affected by common extrinsic factors, may facilitate the co-occurrence of Cryptosporidium and Giardia in urban rats. Rattus norvegicus is recognized as a good model for epidemiological studies and the results of this work suggest that, from an epidemiological point of view, the probability of contact with infectious oocysts and cysts of these parasites can be modulated through environmental management and healthy behaviour towards risk factors. The information presented here will be useful to improve the understanding of the dynamics of zoonotic diseases within urban environments and to contribute to the decision-making of new and effective prophylactic measures.

Genotoxicity evaluation using micronucleus test in Rattus norvegicus captured in urban ecosystems of Buenos Aires, Argentina

The overall goal of the present study was to evaluate and compare the existence of genotoxic damage in Rattus norvegicus captured in sites with different levels of chemical mixtures along the Matanza-Riachuelo river basin (MRRB). For this, thirty-six wild rats (R. norvegicus) were captured from six different sites in the MRRB. Capture sites were characterized with concentrations of 20 parameters in surface water, including concentrations of metals and its soluble state and physicochemical parameters. To evaluate genotoxic damage in the rats, the bone marrow micronucleus test was performed. For this, the frequency of micronucleated polychromatic erythrocytes (MNPCE) was calculated based on the observation of 2000 polychromatic erythrocytes (PCE) per animal. Also, to detect possible cytotoxic effects, the PCE/TE (total erythrocytes) ratio in 1000 erythrocytes/animal was calculated. The frequency of MNPCE was positively associated with the highest concentration of chrome, lead, copper, biological oxygen demand, and chemical oxygen demand. Also, the decrease on PCE/TE ratio in bone marrow was related with increase of practically all metals and physicochemical parameters in surface water. The results of this study reveal that rats that live in the MRRB were exposed to concentrations of pollutants that can cause genotoxic damage, even though the concentrations of these pollutants are mostly below the safety standards. Therefore, this work highlights the importance of using methods that allow to integrate all environmental parameters in risk assessment, such as sentinel species.

Electrochemical oxidation of indanthrene blue dye in a filter-press flow reactor and toxicity analyses with Raphidocelis subcapitata and Lactuca sativa

Alternative routes to degrade dyes are of crucial importance for the environment. Hence, we report the electrochemical removal of indanthrene blue by using a boron-doped diamond anode, focusing on the toxicity of the treated solutions. Different operational conditions were studied, such as current density (5, 10, and 20 mA cm-2) and electrolyte composition (Na2SO4, Na2CO3, and NaNO3). Besides, the pH was monitored throughout the experiment to consider its direct influence on the ecotoxicity effects. The highest electrochemical oxidation efficiency, measured as color removal, was seen in the 180 min condition of electrolysis in 0.033 M Na2SO4, applying 20 mA cm-2, resulting in a color removal of nearly 91% and 40.51 kWh m-3 of energy consumption. The toxicity towards Lactuca sativa depends solely on pH variations being indifferent to color removal. While the inhibition concentration (IC50) for Raphidocelis subcapitata increases 20% after treatment (in optimized conditions), suggesting that the byproducts are more toxic for this specific organism. Our data highlight the importance of analyzing the toxicity towards various organisms to understand the toxic effect of the treatment applied.

Changes in oxidative stress biomarkers in Sinonovacula constricta in response to toxic metal accumulation during growth in an aquaculture farm

Clam farming comprises an important part of China's economy. However, increasing pollution in the ocean caused by toxic metals has led to the bioaccumulation of toxic metals in marine animals, especially the bivalves such as clams, and the consequence of heavy metal-associated toxicity in these animals. Such toxicity can enhance the production of reactive oxygen species (ROS) within the tissues of the animals. In aquatic species, oxidative stress mechanisms have been studied by measuring the antioxidant and oxidative damage index in the tissues. The objectives of this study were to investigate the levels of different toxic metals and the extent of oxidative stress responses in the clam Sinonovacula constricta at different growth periods (from May to October) in an aquaculture farm in Wengyang, an important economic shellfish culture zone in Zhejiang Province, China. Water and sediment samples taken from the farm were subjected to Pb, Hg, Cd, Cr assays. Overall, the levels of these metals in the water and sediment could be considered as light pollution, though the levels of Hg in the water (0.266) and Cd in the sediment (0.813) could be considered as reaching moderate pollution. In addition, the levels of these metals, H₂O₂, MDA and GSH content, antioxidant enzyme (CAT, SOD, GPx) activities as well as the level of metallothioneins (MT) mRNA in the tissues of S. constricta were also analyzed. The levels of Pb, Hg, Cd, Cr increased with increasing culturing time, and a higher level of these metals was accumulated in the visceral mass than in the foot. The levels of MDA and GSH, as well as the level of SOD activity in the viscera and foot of S. constricta increased with increasing metal accumulation. However, CAT and GPX activities, H₂O₂ level and the expression of MT initially increased and then decreased. This suggested that S. constricta might have the ability to control oxidative damage by triggering antioxidant defense in coordination with the metal sequestering response. The results also implied that toxic metal pollution should be taken into account when selecting the site to be used as an aquaculture farm. In addition, the visceral mass should be considered to be a good tissue for measuring the level of metal pollutants.

Are soft tissues of urban rats good indicators of exposure to heavy metal pollution? A study conducted in one of the most polluted basins of Buenos Aires, Argentina

The overall goal of this work was to analyze the relationship between the concentration of lead in the kidney, liver, and stomach contents of rats captured in a polluted urban basin and the concentration of this metal in the environment, meteorological factors, and different intrinsic characteristics of the individuals. To this end, we determined the concentration of lead in the kidney, liver, and stomach contents of 133 Norway rats (Rattus norvegicus) captured in the Matanza-Riachuelo River Basin (Buenos Aires, Argentina). This basin is one of the most severe cases of water pollution in Latin America and metals like lead represent the most common chemical pollutants. Rats were trapped in nine sites with different soil and water lead concentrations, between 2014 and 2015. A positive relationship was found between lead concentration in the liver and kidney of R. norvegicus and the environmental concentration of this metal in water and soil. Although the remaining variables analyzed were also related to the lead concentration in soft tissues, they did not affect the association between the lead concentration in soft tissues and that in the environment. The lead concentration in the stomach contents was not related to any of the variables analyzed. Our results constitute the first study in an urban basin with a gradient of environmental lead concentration and suggest that the quantification of lead in the kidney and liver of rats can be used as an indicator of exposure to this metal within a large city.

Cytotoxic evaluation of glyphosate, using Allium cepa L. as bioindicator

Glyphosate is a chemical compound used mainly as a broad spectrum herbicide, it is recognized for its proven effectiveness and easy handling. It represents more than 60% of the world market of non-selective herbicides and is used in both agricultural fields and family gardens. The present study was designed to test the cytogenotoxic potential of glyphosate using the Allium cepa test as toxicity bioindicator. Consequently, bulbs of A. cepa were exposed to different concentrations of glyphosate (5, 10, 15, 25 and 30 mgL-1) and a control (deionized water), for 72 h; root development was also studied in this period of time. The cytogenotoxic potential of glyphosate was determined by calculating the mitotic index (MI), cellular anomalies (CA) and registering the roots longitudinal growth at 24, 48 and 72 h. Regarding root development, a greater growth was observed in the control treatment in the three measurement times. The mitotic phases analysis, determined that the higher the concentration, the lower the mitotic index, in addition the inhibition of the telophase Mitotic Index (TMI) was observed in any of the concentrations. The results indicate that the exposure to glyphosate of A. cepa meristematic cells induces diverse types of chromosomal anomalies, such as micronuclei (MN), chromosome breaking (CB), nuclear notch (Nn), among others. Therefore, in demonstrates that glyphosate has a highly cytogenotoxic effect for any of the concentrations used.

Evaluation of cytotoxic potential of chlorpyrifos using Lens culinaris Med as efficient bioindicator

The aim of this study was to evaluate the cytotoxic effect of different concentrations of chlorpyrifos (CPF), using L. culinaris apical cells as a biological indicator. L. culinaris seeds were exposed to different concentrations of chlorpyrifos (0, 1, 3, 5, 7, 8, 10 and 15 mg L^-1) and a control solution based on distilled water. Subsequently, root growth was measured during 24, 48 and 72 h. Therefore, the mitotic index (MI) and the number of cellular abnormalities were determined at 72 h. According to the obtained results, a decrease in root size was observed in the concentrations of T5 (8 mg L^-1) and T6 (10 mg L^-1). On the other hand, it was evidenced that, through all the evaluated concentrations, the inhibition of mitosis in the concentrations of T5 (8 mg L^-1), T6 (10 mg L^-1) and T7 (15 mg L^-1) was greater than 50%. Additionally, a variety of chromosomal abnormalities were reported, such as Micronuclei, sticky chromosomes in anaphase, chromosome disruption, irregular anaphase, nucleus absence, nuclear lesions, chromosomes grouped in metaphase, anaphase bridges, metaphase sticky chromosomes, present in all concentrations evaluated. Consequently, the presence of micronuclei in the concentrations of 8 mg L^-1, 10 mg L^-1 and 15 mg L^-1 indicates that the CPF is a highly cytotoxic substance to L. culinaris. Therefore, L. culinaris is a plant species that offers a feasible experimental model to be implemented in laboratory studies with the purpose to evaluate the cytotoxic effect of pesticides.

Geochemical mechanisms controlling the isotopic and chemical composition of groundwater and surface water in a sector of the Pampean plain (Argentina)

The Samborombón River basin, which has eminently rural characteristics, develops within the Pampean plain along with other basins with serious contamination problems due to the growth of the industrial activities and the absence of a proper groundwater management. Considering that the knowledge of the natural baseline quality is important to measure an imposed environmental change, the aim of this work was to study the mechanisms that control the natural composition of groundwater and superficial water in the Samborombón River basin. In order to achieve this, detailed analysis of the minerals forming the aquifer matrix along with the data obtained from isotopes, major and trace elements were performed. Geochemical processes that define the chemical characteristics and contribute to the evolution of both surface and groundwater are associated with rainwater infiltration, carbonate dissolution, cation exchange and evaporation. Additionally, the low concentration of heavy metals may respond to natural background levels. Comprehending the hydrochemical processes governing groundwater and superficial water quality, particularly in a rural area where water supply is vital for the development of human activities, is essential to prevent environmental deterioration and thus, enhance socio-economic growth.

Phytotoxicity and genotoxicity evaluation of 2,4,6-tribromophenol solution treated by UV-based oxidation processes

The environmental detriment due to the presence of emerging contaminants has encouraged the development of advanced oxidation processes. Such methods deal with non-selective chemical reactions. Therefore, toxic byproducts can be generated and distinct post treatment toxicity levels can be expected. The present study investigates the phytotoxicity of 2,4,6-tribromophenol (TBP) to L. sativa seeds and A. cepa bulbs, as well as the TBP phytotoxicity and genotoxicity to A. cepa root. L. sativa seeds and A. cepa bulbs were germinated by being exposed to solutions containing TBP before and after treatment by UV-based processes: direct photolysis (DP), heterogeneous photocatalysis (HP) and photoelectrolysis (PEC). Subsequent analysis of the root length, to determine phytotoxicity, as well as evaluation of chromosomal abnormalities, revealed that the samples treated by DP presented higher phytotoxicity than the untreated ones. On the other hand, samples treated by HP and PEC did not present phytotoxicity. In fact, for the A. cepa assays, phytotoxicity was not observed, including the initial sample. However, genotoxicity assays showed a high frequency of chromosomal aberrations in the initial sample, before the UV-based process treatment. After 140 min of treatment by HP, there was a reduction in genotoxicity, while PEC treatment resulted in a sample with no genotoxicity. In contrast, DP presented high levels of phytotoxicity and genotoxicity. Additionally, DP shows similar degradation and debromination values, when compared to the HP and PEC processes, but less mineralization. Therefore, considering that the DP process did not deals with the HO^• radical, the oxidation pathway can generate byproducts with higher toxicity, which lead to higher levels of phytotoxicity and genotoxicity. These results show that different UV-based oxidation processes are associated to distinct byproducts and toxicity levels. In addition, a toxicity assessment with different organisms should be performed to ensure a safe outcome.

Cytotoxic evaluation of sodium hypochlorite, using Pisum sativum L as effective bioindicator

The objective of this study was to evaluate the cytotoxic effect of different sodium hypochlorite concentrations, using apical root cells of P. sativum as a bioindicator. Initially, the seeds of P. sativum were exposed to different concentrations of sodium hypochlorite (0.1, 0.2, 0.4, 0.8, 1.6, 2 mg L-1) and to a control solution based on distilled water. Next, root growth was measured during 24, 48 and 72 h. Subsequently, the mitotic index (MI) and cellular anomalies (5000 cells per treatment) were determined at 72 h. According to the results obtained, a decrease in root growth was observed at concentrations of 0.4, 1.6 and 2 mg L-1. Likewise, it was evident that, among all the evaluated concentrations, an inhibition of mitosis higher than 50% was presented. Additionally, chromosomal anomalies were also generated, such as Nuclear notch, lagging chromosomes and Chromosomal break, which were present in all the concentrations evaluated. In addition, the presence of micronuclei at concentrations of 2.0 and 1.6 mg L-1 indicate that sodium hypochlorite is a highly cytotoxic substance. Therefore, P. sativum is a specie that offers a feasible experimental model to be implemented in the laboratory with the aim to evaluate the cytotoxic effect of any cytotoxic substance.

Acute toxicity of water and aqueous extract of soils from Champotón river in Lactuca sativa L

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Inhibitory effect on elongation for radicle and stem of Lactuca sativa was detected.

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Champotón river water showed more phytotoxic effect than aqueous extracts of the soil.

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Radicula and stem of lettuces showed variations in growth when exposed to different water dilutions from Champoton river.

The seeds germination, stem and root elongation of water lettuces (Lactuca sativa L) were used to evaluate the phytotoxicity of water and soil of Champotón River, Campeche, Mexico. water and soil sample were collected from two sampling sites. Lettuce seeds were exposed to three different dilutions of water and aqueous extract of soil. Significant differences on germination, root and stem elongation of lettuce were detected. Water showed more phytotoxic effect than aqueous extract of soil and inhibitory concentration 50 (IC₅₀) for radicle exposed to river water was 52% while stem elongation was 69%. Due to paucity the previously available phytotoxicological studies onto Champotón River, it is now essential to allocate time and resources to consider development of suitable chronic phytotoxicity tests.

Spatial Distribution of Metals and Associated Risks in Surface Sediments Along a Typical Urban River Gradient in the Beijing Region

Surface sediments from Beiyun River located in the rapidly urbanized Beijing metropolis were collected and analyzed for heavy metals (As, Cd, Cr, Cu, Mn, Ni, Pb, and Zn) to investigate their spatial distribution pattern, ecotoxicology and source identification. Results indicated the average heavy metal concentrations of Cd, Cr, Cu, Pb, and Zn were approximately 4, 2, 3, 2, and 4 times higher than their background values. Spatially, we found the concentrations of heavy metals made significant change in four sections along urbanized river gradients. The contents in midstream of urban region and farmland region (section 2 and section 3) were greater than those in upstream (section 1) and downstream (section 4). However, one-way analysis of variance for spatial analysis suggested there were no significant differences between mainstream and tributaries. The geo-accumulation index (I _geo) used to assess the sediment quality exhibited there was a decreasing order for the average I _geo of measured heavy metals: Zn (0.82) > Cd (0.53) > Cu (0.50) > Cr (- 0.08) > Pb (- 0.45) > Ni (- 0.96) > Mn (- 0.97) > As (- 1.01), whereas they had different "high-low" orders at different sampling transects. Ecological risk index values showed that section 2 and section 3 revealed a high and moderate ecological risk, respectively. Furthermore, principal component analysis indicated the first principle component explained 64.73% of total variance with the main pollutants of As, Cr, Ni, Zn, and Cu which were probably controlled by the mixed sources covering natural factors and anthropogenic input.

Phytoextraction of heavy metals from a multiply contaminated dredged sediment by chicory (Cichorium intybus L.) and castor bean (Ricinus communis L.) enhanced with EDTA, NTA, and citric acid application

The remediation of contaminated dredged sediments is necessary to eliminate the risk towards human beings or the environment when there is disposal on land. A greenhouse experiment was carried out to evaluate the chemically assisted phytoextraction to clean up dredged sediment contaminated with Cr, Cu, Pb, and Zn. The ability of castor bean and chicory to absorb, translocate, and accumulate metals from sediment to root and shoot was evaluated by applying EDTA (5 mM), NTA (5 mM), and citric acid (60 mM) to sediment, before the harvest. Citric acid 60 mM was the most effective treatment in increasing Cr, Cu, and Pb in castor bean and chicory shoot. Chicory could accumulate 1730 mg Cr kg-1 in shoot, and had greater values than one for the bioaccumulation and translocation factors when citric acid was added to the sediment. But, the Cr percentages removed per harvest of chicory were 0.05% and were lower for Cu, Pb, and Zn due to low biomass obtained. Citric acid-assisted phytoextraction with chicory can be a promising short time solution to reduce Cr concentration in sediment and reach the Cr level guide for industrial land use only if suitable agronomic practices could be implemented to increase crop yield.

Mitochondria and mitochondrial DNA as relevant targets for environmental contaminants

The mitochondrial DNA (mtDNA) is a closed circular molecule that encodes, in humans, 13 polypeptides components of the oxidative phosphorylation complexes. Integrity of the mitochondrial genome is essential for mitochondrial function and cellular homeostasis, and mutations and deletions in the mtDNA lead to oxidative stress, mitochondrial dysfunction and cell death. In vitro and in situ studies suggest that when exposed to certain genotoxins, mtDNA accumulates more damage than nuclear DNA, likely owing to its organization and localization in the mitochondrial matrix, which tends to accumulate lipophilic, positively charged molecules. In that regard, several relevant environmental and occupational contaminants have physical-chemical characteristics that indicate that they might accumulate in mitochondria and target mtDNA. Nonetheless, very little is known so far about mtDNA damage and mitochondrial dysfunction due to environmental exposure, either in model organisms or in humans. In this article, we discuss some of the characteristics of mtDNA which render it a potentially relevant target for damage by environmental contaminants, as well as possible functional consequences of damage/mutation accumulation. In addition, we review the data available in the literature focusing on mitochondrial effects of the most common classes of environmental pollutants. From that, we conclude that several lines of experimental evidence support the idea that mitochondria and mtDNA are susceptible and biologically relevant targets for pollutants, and more studies, including mechanistic ones, are needed to shed more light into the contribution of mitochondrial dysfunction to the environmental and human health effects of chemical exposure.