The Allium cepa bioassay to evaluate landfarming soil, before and after the addition of rice hulls to accelerate organic pollutants biodegradation

Chronic exposure of industrial grade calcium carbide and ethylene glycol exert genotoxic effect in Wistar albino rats

OBJECTIVES

Calcium carbide (CaC2) and ethylene glycol (EG) are the two commonly used fruit ripening agents. The toxic effects of these chemicals on internal organs were reported in experimental animals. Even though the adverse effects of these compounds have been investigated for many years, there are no sufficient data available with regard to genotoxic effects. The present study evaluates the genotoxic effect of chronic exposures of CaC2 and EG in Wistar albino rats.

METHODS

CaC2 and EG were administered to the rats orally for 180 days. Chromosomal aberrations and micronuclei formation were analysed in bone marrow and peripheral blood cells. Comet assay was performed to analyse the DNA strand break. The toxic effects of the chemicals were analysed by MTT assay with normal human intestinal epithelial (IEC-6) cells.

RESULTS

Upon chronic exposure, CaC2 and EG caused chromosomal aberrations, micronuclei formation and  DNA strand breaks extensively in bone marrow and peripheral blood cells. In MTT assay, the chemicals were found to be toxic to IEC-6 cells with IC50 values at 160 and 200 μg/mL for CaC2 and EG, respectively.

CONCLUSIONS

The results show that these chemicals have a potential to cause genomic level of toxicity which may lead to carcinogenic event at a chronic level exposure. The study warns to reinforce the administrative measures against the use of CaC2 and EG for fruit ripening process.

Revitalization of Total Petroleum Hydrocarbon Contaminated Soil Remediated by Landfarming

Soil health deteriorates through the contamination and remediation processes, resulting in the limitation of the reuse and recycling of the remediated soils. Therefore, soil health should be recovered for the intended purposes of reuse and recycling. This study aimed to evaluate the applicability and effectiveness of several amendments to revitalize total petroleum hydrocarbon contaminated soils remediated by the landfarming process. Ten inorganic, organic, and biological amendments were investigated for their dosage and duration, and nine physicochemical, four fertility, and seven microbial (soil enzyme activity) factors were compared before and after the treatment of amendments. Finally, the extent of recovery was quantitatively estimated, and the significance of results was confirmed with statistical methods, such as simple regression and correlation analyses assisted by principal component analysis. The landfarming process is considered a somewhat environmentally friendly remediation technology to minimize the adverse effect on soil quality, but four soil properties—such as water holding capacity (WHC), exchangeable potassium (Ex. K), nitrate-nitrogen (NO₃-N), available phosphorus (Av. P), and urease—were confirmed to deteriorate through the landfarming process. The WHC was better improved by organic agents, such as peat moss, biochar, and compost. Zeolite was evaluated as the most effective material for improving Ex. K content. The vermicompost showed the highest efficacy in recovering the NO₃-N content of the remediated soil. Chlorella, vermicompost, and compost were investigated for their ability to enhance urease activity effectively. Although each additive showed different effectiveness according to different soil properties, their effect on overall soil properties should be considered for cost-effectiveness and practical implementation. Their overall effect was evaluated using statistical methods, and the results showed that compost, chlorella, and vermicompost were the most relevant amendments for rehabilitating the overall health of the remediated soil for the reuse and/or recycling of agricultural purposes. This study highlighted how to practically improve the health of remediated soils for the reuse and recycling of agricultural purposes.

Amendments and bioaugmentation enhanced phytoremediation and micro-ecology for PAHs and heavy metals co-contaminated soils

Co-existence of polycyclic aromatic hydrocarbons (PAHs) and multi-metals challenges the decontamination of large-scale contaminated sites. This study aims to comprehensively evaluate the remediation potential of intensified phytoremediation in coping with complex co-contaminated soils. Results showed that the removal of PAHs and heavy metals is time-dependent, pollution-relevant, and plant-specific. Removal of sixteen PAHs by Medicago sativa L. (37.3%) was significantly higher than that of Solanum nigrum L. (20.7%) after 30 days. S. nigrum L. removed higher amounts of Cd than Zn and Pb, while M. sativa L. uptake more Zn. Nevertheless, amendments and microbial agents significantly increased the phytoremediation efficiency of pollutants and shortened the gap between plants. Cd removal and PAHs dissipation reached up to 80% and 90% after 90 days for both plants. Heavy metal stability in soil was promoted after the intensified phytoremediation. Plant lipid peroxidation was alleviated, regulated by changed antioxidant defense systems (superoxide dismutase, peroxidase, catalase). Soil enzyme activities including dehydrogenase, urease, and catalase increased up to 5-fold. Soil bacterial diversity and structure were changed, being largely composed of Proteobacteria, Actinobacteria, Patescibacteria, Bacteroidetes, and Firmicutes. These findings provide a green and sustainable approach to decontaminating complex-polluted environments with comprehensive improvement of soil health.

Cytogenetic toxicity from pesticide and trace element mixtures in soils used for conventional and organic crops of Allium cepa L

Pesticides and trace elements occur in complex mixtures in agroecosystems, affecting soil health and food security. Hence, it is necessary to determine their toxicity in field conditions and to develop monitoring approaches to assess conventional and organic agriculture. The aim of this research was to evaluate the associations between Allium cepa L. cytogenetic biomarkers and the realistic mixture of pesticides and trace elements found in soils of conventional, conversion, and organic crops in an intensive agricultural region in Colombia. Pesticide screening was conducted using GC-MS/MS and LC-MS/MS methods. Arsenic, cadmium, lead, and zinc were analyzed by ICP-MS; chromium, copper, nickel, and selenium by ICP-OES; and mercury by a direct analyzer. The meristematic cells in roots of Allium cepa L. were analyzed through microscopic observations to quantify cytogenetic effects. In conventional crops, 26 pesticides were detected in the soil samples, and those were below the limit of quantification in organic crops. The mean levels of As, Cd, Cr, Ni, Pb, and Se were also greater in soils of conventional crops compared to the organics. In addition, the biomarkers of cytotoxicity and genotoxicity appeared augmented in conventional samples, and those were correlated with pesticide and trace element concentrations, pollution indices, and hazard quotients. Subsequently, a discriminant function based on the mitotic index, chromosomal aberrations, and nuclear abnormalities was suitable to classify the samples by crop type. These results demonstrate the sensitivity of Allium cepa L. to the toxicity of complex mixtures in field crops and its potential as an in-situ approach for soil health monitoring in organic and conventional crop systems.

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

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

Far-reaching cytogenotoxic effects of mine waste from the Fundão dam disaster in Brazil

On November 2015, one of Brazil's most important watersheds was impacted by the mine waste from Fundão dam collapse in Mariana. The mine waste traveled over 600 km along the Doce River before reaching the sea, causing severe devastation along its way. Here we assessed trace element concentrations and cytogenotoxic effects of the released mine waste. Water samples were collected along the Doce River ten days after the disaster in two impacted sites and one non-impacted site. Sampling points were located hundreds of kilometers downstream of the collapsed dam. Water samples were used for trace element quantification and to run an experiment using Allium cepa to test cytogenotoxicity. We found extremely high concentrations of particulate Fe, Al, and Mn in the impacted sites. We observed cytogenotoxic effects such as alterations in mitotic and phase indexes, and enhanced frequency of chromosomal aberrations. Our results indicate interferences in the cell cycle in impacted sites located hundreds of kilometers downstream of the disaster. The environmental impacts of the dam collapse may not only be far-reaching but also very likely long-lasting, because the mine waste may persist in the Doce River sediment for decades.

Evaluation of the potential agricultural use of biostimulated sewage sludge using mammalian cell culture assays

Among the bioremediation processes, biostimulation is an effective methodology for the decontamination of organic waste by the addition of agents that stimulate the indigenous microbiota development. Rice hull is a biostimulating agent that promotes the aeration of edaphic systems and stimulates the aerobiotic activity of soil microorganisms. The present study aimed to evaluate the efficacy of the bioremediation and biostimulation processes in reducing the toxicity of sewage sludge (SS) and to evaluate its possible application in agriculture using cytotoxic and genotoxic assays in human hepatoma cells (HepG2). SS of domestic origin was tested as both the pure product (PSS) and mixed with soil (S) and with a stimulating agent, such as rice hull (RH), in different proportions (SS + S and SS + S + RH); we also examined different remediation periods (3 months - T1 and 6 months - T2). For the PSS sample, a significant induction of micronucleus (MN) in T2 was observed with nuclear buds in all of the periods assessed, and we observed the presence of more than one alteration per cell (MN and nuclear bud) in T1 and T2. The PSS sample caused genotoxic effects in the HepG2 cells even after being bioremediated. For the samples containing soil and/or rice hull, no toxic effects were observed in the test system used. Therefore, the addition of SS to agricultural soils should be conducted with caution, and it is important that the SS undergoes a remediation process, such as bioremediation and biostimulation treatments.

Comparison of landfarming amendments to improve bioremediation of petroleum hydrocarbons in Niger Delta soils

Large scale landfarming experiments, using an extensive range of treatments, were conducted in the Niger-Delta, Nigeria to study the degradation of oil in contaminated soils. In this work the effect of nutrient addition, biosurfactant, Eisenia fetida (earthworm) enzyme extract, bulking and sorption agents and soil neutralization were tested. It was found that these treatments were successful in removing up to 53% of the total petroleum hydrocarbon in the soil within 16 weeks. A comparison between treatments demonstrated that most were no more effective than agricultural fertilizer addition alone. One strategy that did show better performance was a combination of nutrients, biochar and biosurfactant, which was found to remove 23% more Total Petroleum Hydrocarbons (TPH) than fertilizer alone. However, when performance normalized costs were considered, this treatment became less attractive as a remedial option. Based on this same analysis it was concluded that fertilizer only was the most cost effective treatment. As a consequence, it is recommended that fertilizer is used to enhance the landfarming of hydrocarbon contaminated soils in the Niger Delta. The attenuation rates of both bulk TPH and Total Petroleum Hydrocarbon Criteria Working Group (TPHCWG) fractions are also provided. These values represent one of the first large scale and scientifically tested datasets for treatment of contaminated soil in the Niger Delta region. An inverse correlation between attenuation rates and hydrocarbon molecular weight was observed with heavy fractions showing much slower degradation rates than lighter fractions. Despite this difference, the bioremediation process resulted in significant removal of all TPH compounds independent of carbon number.

Antigenotoxicity and antimutagenicity of ethanolic extracts of Brazilian green propolis and its main botanical source determined by the Allium cepa test system

Brazilian green propolis is a resinous substance prepared by bees from parts of the plant Baccharis dracunculifolia. As it possess several biological properties, this work assessed the cytotoxic/anticytotoxic, genotoxic/antigenotoxic and mutagenic/antimutagenic potential of ethanolic extracts of Brazilian green propolis (EEGP) and of B. dracunculifolia (EEBD), by means of the Allium cepa test system. The effects were evaluated by assessing the chromosomal aberrations (CA) and micronuclei (MN) frequencies on meristematic and F1 generation cells from onion roots. Chemical analyses performed with the extracts showed differences in flavonoid quality and quantity. No genotoxic or mutagenic potential was detected, and both extracts were capable of inhibiting cellular damage caused by methyl methanesulfonate (MMS) treatment, reducing the frequencies of CA and MN. By these data, we can infer that, independent of their flavonoid content, the extracts presented a protective effect in A. cepa cells against the clastogenicity of MMS.

Ex-Situ Remediation Technologies for Environmental Pollutants: A Critical Perspective

Pollution and the global health impacts from toxic environmental pollutants are presently of great concern. At present, more than 100 million people are at risk from exposure to a plethora of toxic organic and inorganic pollutants. This review is an exploration of the ex-situ technologies for cleaning-up the contaminated soil, groundwater and air emissions, highlighting their principles, advantages, deficiencies and the knowledge gaps. Challenges and strategies for removing different types of contaminants, mainly heavy metals and priority organic pollutants, are also described.

Rice brans, rice bran oils, and rice hulls: composition, food and industrial uses, and bioactivities in humans, animals, and cells

Rice plants produce bioactive rice brans and hulls that have been reported to have numerous health-promoting effects in cells, animals, and humans. The main objective of this review is to consolidate and integrate the widely scattered information on the composition and the antioxidative, anti-inflammatory, and immunostimulating effects of rice brans from different rice cultivars, rice bran oils derived from rice brans, rice hulls, liquid rice hull smoke derived from rice hulls, and some of their bioactive compounds. As part of this effort, this paper also presents brief summaries on the preparation of health-promoting foods including bread, corn flakes, frankfurters, ice cream, noodles, pasta, tortillas, and zero-trans-fat shortening as well as industrial products such bioethanol and biodiesel fuels. Also covered are antibiotic, antiallergic, anticarcinogenic, antidiabetic, cardiovascular, allelochemical, and other beneficial effects and the mechanisms of the bioactivities. The results show that food-compatible and safe formulations with desirable nutritional and biological properties can be used to develop new multifunctional foods as well as bioethanol and biodiesel fuel. The overlapping aspects are expected to contribute to a better understanding of the potential impact of the described health-promoting potential of the rice-derived brans, oils, and hulls in food and medicine. Such an understanding will enhance nutrition and health and benefit the agricultural and industrial economies.

Clastogenicity of landfarming soil treated with sugar cane vinasse

The addition of nutrients and/or soil bulking agents is used in bioremediation to increase microbial activity in contaminated soils. For this purpose, some studies have assessed the effectiveness of vinasse in the bioremediation of soils contaminated with petroleum waste. The present study was aimed at investigating the clastogenic/aneugenic potential of landfarming soil from a petroleum refinery before and after addition of sugar cane vinasse using the Allium cepa bioassay. Our results show that the addition of sugar cane vinasse to landfarming soil potentiates the clastogenic effects of the latter probably due the release of metals that were previously adsorbed into the organic matter. These metals may have interacted synergistically with petroleum hydrocarbons present in the landfarming soil treated with sugar cane vinasse. We recommend further tests to monitor the effects of sugar cane vinasse on soils contaminated with organic wastes.

Cadmium-induced cyto- and genotoxicity are organ-dependent in lettuce

Cadmium is a priority pollutant. Its mechanisms and effects within different plant organs remain unclear. Here, cyto-genotoxicity biomarkers were evaluated in roots and leaves after Cd exposure (0, 1, 10, and 50 μM) of the model crop Lactuca sativa L. (cv. "Reine de Mai"). Overall, superoxide dismutase (SOD) and catalase (CAT) activities were stimulated in leaves, where Cd accumulation was lower in comparison to that in roots. In roots, SOD and peroxidase (POX, APX) activities were stimulated. Moreover, in both organs glutathione reductase (GR) was not affected by Cd. Overall, the H(2)O(2) content increased in both organs, while the total antioxidant capacity decreased in leaves and increased in roots with Cd concentrations. In both organs, lipid and protein oxidation rose with consequent increase of membrane permeability. Simultaneously, the comet assay showed that tail moment, tail length, and % tail DNA were maximum for 1 μM. For 10 μM, shorter tails were found suggesting induced Cd-DNA adducts that lead to DNA-DNA/DNA-protein cross-links, and/or formation of longer DNA fragments, and/or impairment of DNA repair mechanisms, while at 50 μM, nucleoids sensitivity to the technique was evident. This result was consistent with the maximum micronuclei frequency found for the 10 μM Cd dose in roots, suggesting that the surviving cells in this organ had an increase of mitotic catastrophe and that DNA repair systems for blocking cell cycle were dysfunctional. In lower Cd concentrations, root cells might have developed strategies to repair damaged DNA by blocking the cell cycle at specific checkpoints, thus avoiding mitotic catastrophe. Roots at 1 μM showed a cell cycle blockage trend at the G(2) checkpoint, while those at higher concentrations presented S phase delay. We finally discuss a general model of Cd-organ interaction covering these cyto- and genotoxic effects and the potential use of this cultivar in phytoremediation strategies.

Allium cepa test in environmental monitoring: a review on its application

Higher plants are recognized as excellent genetic models to detect environmental mutagens and are frequently used in monitoring studies. Among the plant species, Alium cepa has been used to evaluate DNA damages, such as chromosome aberrations and disturbances in the mitotic cycle. Employing the A. cepa as a test system to detect mutagens dates back to the 40s. It has been used to this day to assess a great number of chemical agents, which contributes to its increasing application in environmental monitoring. The A. cepa is characterized as a low cost test. It is easily handled and has advantages over other short-term tests that require previous preparations of tested samples, as well as the addition of exogenous metabolic system. Higher plants, even showing low concentrations of oxidase enzymes and a limitation in the substrate specification in relation to other organism groups, present consistent results that may serve as a warning to other biological systems, since the target is DNA, common to all organisms. The A. cepa test also enables the evaluation of different endpoints. Among the endpoints, chromosome aberrations have been the most used one to detect genotoxicity along the years. The mitotic index and some nuclear abnormalities are used to evaluate citotoxicity and analyze micronucleus to verify mutagenicity of different chemicals. Moreover, the A. cepa test system provides important information to evaluate action mechanisms of an agent about its effects on the genetic material (clastogenic and/or aneugenic effects). In the face of all the advantages that the A. cepa test system offers, it has been widely used to assess the impacts caused by xenobiotics, characterizing an important tool for environmental monitoring studies, where satisfactory results have been reported.