Ecotoxicity tests with Allium cepa to determine the efficiency of rice husk ash in the treatment of groundwater contaminated with benzene, toluene, ethylbenzene, and xylene

Ecotoxicity of five veterinary antibiotics on indicator organisms and water and soil communities

This study explores the environmental effects of five common veterinary antibiotics widely detected in the environment, (chlortetracycline,CTC; oxytetracycline,OTC; florfenicol,FF; neomycin, NMC; and sulfadiazine, SDZ) on four bioindicators: Daphnia magna, Vibrio fischeri, Eisenia fetida, and Allium cepa, representing aquatic and soil environments. Additionally, microbial communities characterized through 16 S rRNA gene sequencing from a river and natural soil were exposed to the antibiotics to assess changes in population growth and metabolic profiles using Biolog EcoPlates™. Tetracyclines are harmful to Vibrio fisheri (LC50 ranges of 15-25 µg/mL), and the other three antibiotics seem to only affect D. magna, especially, SDZ. None of the antibiotics produced mortality in E. fetida at concentrations below 1000 mg/kg. NMC and CTC had the highest phytotoxicities in A. cepa (LC50 = 97-174 µg/mL, respectively). Antibiotics significantly reduced bacterial metabolism at 0.1-10 µg/mL. From the highest to the lowest toxicity on aquatic communities: OTC > FF > SDZ ≈ CTC > NMC and on edaphic communities: CTC ≈ OTC > FF > SDZ > NMC. In river communities, OTC and FF caused substantial decreases in bacterial metabolism at low concentrations (0.1 µg/mL), impacting carbohydrates, amino acids (OTC), and polymers (FF). At 10 µg/mL and above, OTC, CTC, and FF significantly decreased metabolizing all tested metabolites. In soil communities, a more pronounced decrease in metabolizing ability, detectable at 0.1 µg/mL, particularly affected amines/amides and carboxylic and ketonic acids (p < 0.05). These new ecotoxicity findings underscore that the concentrations of these antibiotics in the environment can significantly impact both aquatic and terrestrial ecosystems.

Ecotoxicological Study of Tannic Acid on Soil and Water Non-Target Indicators and Its Impact on Fluvial and Edaphic Communities

Tannic acid (TA) is a key tannin extensively used in the leather industry, contributing to around 90% of global leather production. This practice leads to the generation of highly polluting effluents, causing environmental harm to aquatic ecosystems. Additionally, tannins like TA degrade slowly under natural conditions. Despite efforts to reduce pollutant effluents, limited attention has been devoted to the direct environmental impact of tannins. Moreover, TA has garnered increased attention mainly due to its applications as an antibacterial agent and anti-carcinogenic compound. However, our understanding of its ecotoxicological effects remains incomplete. This study addresses this knowledge gap by assessing the ecotoxicity of TA on non-target indicator organisms in both water (Vibrio fischeri, Daphnia magna) and soil environments (Eisenia foetida, Allium cepa), as well as natural fluvial and edaphic communities, including periphyton. Our findings offer valuable insights into TA's ecotoxicological impact across various trophic levels, underscoring the need for more comprehensive investigations in complex ecosystems. Our results demonstrate that TA exhibits ecotoxicity towards specific non-target aquatic organisms, particularly V. fischeri and D. magna, and phytotoxicity on A. cepa. The severity of these effects varies, with V. fischeri being the most sensitive, followed by D. magna and A. cepa. However, the soil-dwelling invertebrate E. foetida shows resistance to the tested TA concentrations. Furthermore, our research reveals that substantial TA concentrations are required to reduce the growth of river microbial communities. Metabolic changes, particularly in amino acid and amine metabolism, are observed at lower concentrations. Notably, the photosynthetic yield of river periphyton remains unaffected, even at higher concentrations. In contrast, soil microbial communities exhibit greater sensitivity, with significant alterations in population growth and metabolic profiles at a very low concentration of 0.2 mg/L for all metabolites. In summary, this study offers valuable insights into the ecotoxicological effects of TA on both aquatic and terrestrial environments. It underscores the importance of considering a variety of non-target organisms and complex communities when assessing the environmental implications of this compound.

Efficiency of rice husk ash to adsorb chromium(VI) using the Allium cepa toxicity test

Adsorption is widely used in the treatment of effluents and contaminated water. However, the removal of the pollutant alone does not ensure that the effluent can be safely discharged in the environment. Controlling effluent toxicity may become an important tool to ensure that the quality of the treated effluent is compatible with that of the receiving water body. In this sense, this study evaluated the efficiency of rice husk ash (RHA) to adsorb chromium(VI) using the Allium cepa toxicity test. Adsorption was assessed based on the variables adsorption time, initial concentration, and pH. The data obtained were fitted the pseudo-second-order and the pseudo-first-order models, and the Langmuir and Freundlich isotherms. Kinetic analysis indicated removal rates between 43 and 100%. All data were best fitted by the pseudo-second-order model. Also, pH 1 and pH 2 data were best fitted by the Freundlich and Langmuir isotherms, respectively. In the Allium cepa test, pH 2 solutions were toxic. At pH 7, the Alium cepa test confirmed the efficiency of chromium(VI) adsorption by RHA, ensuring acceptable germination index values.

An insight into the cytotoxicity, genotoxicity, and mutagenicity of smoked cigarette butt leachate by using Allium cepa as test system

Smoked cigarette butt (SCB) discharged in the environment became an issue of unknown consequences for plants. Thus, we aim at assessing the impact of water containing SBC leachate on the meristem cells of Allium cepa roots. We defined the following experimental groups: negative control (water), positive control (cyclophosphamide); water with SCB leachate at environmental concentration (1.9 μg/L of nicotine) (EC1× group) and water with SCB leachate concentration 1000 times higher than EC1 (EC1000× group). Mitotic index, total number of abnormal cells, index of abnormal cells per mitotic/phase, relative growth index, and inhibition index were calculated after 48 exposure hours. Root meristems were used to prepare slides in order to investigate chromosomal and nuclear abnormalities. According to our data, plants exposed to SCB leachate presented low relative growth index, high inhibition index, large number of abnormal cells, and high abnormality frequency at metaphase/anaphase. The exposed A. cepa recorded a wide variety of abnormalities such as diagonal metaphase/anaphase, metaphase/anaphase presenting chromosome fragments, binucleated cells, displaced nucleus, chromosome bridges, micronuclei, necrotic cells, stick metaphase, chromosome adherence, notched nucleus, among other cell disturbances. The chemicals in the SBC leachate had aneugenic and clastogenic effect on the genetic material of the tested plants, either when they acted individually, synergistically, or additively. Thus, our study is a pioneer in reporting that the mere disposal of cigarette butts in the environment can have cytotoxic, genotoxic, and mutagenic effects on plants.