Individual and combined toxic effects of herbicide atrazine and three insecticides on the earthworm, Eisenia fetida

Bio-transformation of poultry litter and activated sewage sludge to produce biomixtures for the remediation of water polluted with pesticides

The aim of this study was to formulate novel biomixtures with the ability to dissipate globally used pesticides. For this, an effective stabilization of two wastes, poultry litter and activated sewage sludge, was achieved through a combination of composting and vermicomposting, with the aid of the earthworm Eisenia fetida. Hence, two different mixtures were prepared combining the wastes with and without the addition of sewage sludge, and their physicochemical and microbiological characterization was examined during both processes. Earthworms reproduction was promoted by more than fourteen times the initial number of individuals introduced. This step made it possible to obtain substrates rich in organic matter, stable and non-pathogenic. The resulting vermicomposted substrates (V-C1 and V-C2) were used to produce two different biomixtures with wheat stubble (WS) and soil (S): SWSV-C1 and SWSV-C2, and they were tested for the remediation of a solution of five pesticides (2,4-D, cypermethrin, imidacloprid, acetochlor and dimethoate) in a 119-days assay. Comparisons were made with a WS-only biomixture (SWS) and a soil control. All biomixtures were more successful in dissipating the pesticides than soil; 2,4-D, dimethoate, and acetochlor degradation reached more than 99% in the three biomixtures after 28-56 days of assay. Biomixtures containing either vermicomposts acted faster than SWS, particularly for 2,4-D, dimethoate and cypermethrin. The total microbial activity was found to be higher in the two biomixtures containing vermicompost, which can be linked to their enhanced performance in the degradation of pesticides. Although the germination of Lactuca sativa proved that neither of the three spent biomixtures were phytotoxic at the end (germination index >60%), only SWSV-C1 and SWSV-C2 proved to be safe for the survival of E. fetida. This work confirms that vermicompost improves the success of biomixtures, not only in terms of pesticide removal, but also providing non-toxic spent biomixtures.

Deciphering survival strategies: Oxidative stress and microbial interplay in Eisenia fetida under tetracycline contamination

Soil contamination resulting from residual antibiotics presents a pressing need to understand the survival mechanisms of soil organisms in polluted environments. This study focused on Eisenia fetida, and tetracycline stress experiments were conducted in a controlled environment using sterile artificial soil. The stress concentration ranged from 0 to 600 mg/kg, and stress cycles lasted either 10 or 30 days. The objective of this study was to assess the effects of oxidative stress and the changes in microbial communities both within and outside the earthworms. A comprehensive mathematical model was developed to elucidate the responses of organisms following exposure to stress utilizing factor analysis, grey relational analysis, and hierarchical entropy weight analysis. Under tetracycline stress, the initial stage (1-3 days) exhibited a coordinated regulation of oxidative stress and microbial communities in the soil with the assistance of CAT and GPX enzymes. The subsequent stage (4-5 days) further emphasized the influence of soil microbial communities. A notable "feedback regulation" of soil microbial communities on oxidative stress was observed during the third stage (6-8 days). Earthworms maintained a metabolic balance in the fourth stage (9-10 days). In the long term, the stress-induced a self-detoxification mechanism within soil microbial communities, which collaborated with GPX to respond to oxidative stress.

A systematic review of the toxic effects of a nanopesticide on non-target organisms: Estimation of protective concentrations using a species sensitivity distribution (SSD) approach - The case of atrazine

Nanopesticides, such as nanoencapsulated atrazine (nATZ), have been studied and developed as eco-friendly alternatives to control weeds in fields, requiring lower doses. This review contains a historical and systematic literature review about the toxicity of nATZ to non-target species. In addition, the study establishes protective concentrations for non-target organisms through a species sensitivity distribution (SSD) approach. Through the systematic search, we identified 3197 publications. Of these, 14 studies addressed "(nano)atrazine's toxicity to non-target organisms". Chronological and geographic data on the publication of articles, characterization of nATZ (type of nanocarrier, size, polydispersity index, zeta potential), experimental design (test species, exposure time, measurements, methodology, tested concentrations), and toxic effects are summarized and discussed. The data indicate that cell and algal models do not show sensitivity to nATZ, while many terrestrial and aquatic invertebrates, aquatic vertebrates, microorganisms, and plants have high sensitivity to nAZT. The SSD results indicated that D. similis is the most sensitive species to nATZ, followed by C. elegans, E. crypticus, and P. subcapitata. However, the limitations in terms of the number of species and endpoints available to elaborate the SSD reflect gaps in knowledge of the effects of nATZ on different ecosystems.

Individual and combined toxicity of imidacloprid and two seed dressing insecticides on collembolans Folsomia candida

The aim of this study was to examine the chronic toxicity of imidacloprid (IMI), clothianidin (CLO) and fipronil (FIP) as a single exposure, as well as binary mixtures of IMI with CLO or FIP toward collembolans Folsomia candida, which are fauna present in the soil. Chronic toxicity assays were performed following an ISO guideline in a Tropical Artificial Soil (TAS), and the influence on the number and growth of the juveniles produced were determined. The range of nominal concentrations used in the tests with the individual compounds was 0.08-1.28 mg/kg (IMI), 0.079-1.264 mg/kg (FIP) and 0.007-0.112 mg/kg (CLO), whereas the mixture assays were performed with half the value used in the tests with individual compounds. Based upon single exposures, IMI produced a similar impact of reducing reproduction by 50% (EC₅₀ ranging from 0.74 to 0.85 mg/kg) compared to FIP (EC₅₀ = 0.78 mg/kg), whereas CLO was the most toxic to F. candida (EC₅₀ = 0.08 mg/kg). Their mixtures generally resulted in a diminished effect on reproduction, as evidenced by the higher EC₅₀ values. In contrast, in the case of the IMI+FIP combination at high concentrations at the EC₅₀ level, a synergistic effect on toxicity was observed. The single exposure to the three insecticides and the mixture of IMI-FIP also decreased the size of generated juveniles, which was evidenced by the reduction in the proportion of large juveniles and increased proportion of small juveniles. However, both binary mixtures (IMI-FIP and IMI-CLO) presented antagonistic effects as evidenced by less than expected reductions in growth. Data on the toxic effects of IMI in a mixture with other seed dressing insecticides to collembolans provides useful information to environmental risk assessors by diminishing the uncertainties on the ecological risk of exposure to pesticides, enabling soil management degradation by utilizing multiple insecticides.

Does pesticide use in agriculture present a risk to the terrestrial biota?

Inadequate pesticide application practices have many implications on human and environmental health. This research aimed at assessing pesticide risks on bees, non-target arthropods (NTAs) and earthworms, using PRIMET (Pesticide Risks in the Tropics to Man, Environment and Trade), a pesticide risk model, in the western highlands agro-ecological zone of Cameroon. For this purpose, information on pesticide usage stratagem (dosage, application interval and number of applications) and ecotoxicological properties (median lethal doses, persistence and no observable effect concentration) were gathered and entered into PRIMET to acquire the Predicted Exposure Concentration (PEC), No Effect Concentration (NEC) and Exposure Toxicity Ratio, ETR = PEC / NEC). The risk assessment revealed that the riskiest pesticides for earthworms were acetamiprid, glyphosate and imidacloprid with ETR values of 2963, 1667 and 419 respectively. For bees, acetamiprid, cypermethrin, emamectin benzoate, imidacloprid, and lambda-cyhalothrin were highly risky, with respective ETR values of 3252, 487, 278, 1383 and 295. The model predicted NTAs to be predominantly defenceless against cypermethrin and imidacloprid, as these compounds exhibited the topmost values of ETR of, 4.3 × 10⁸ and 4.4 × 10⁷, respectively. Other pesticides that were modelled to be highly risky to NTAs comprised chlorothalonil (ETR = 2076), cymoxanil (ETR = 1133), emamectin benzoate (ETR = 1700), lambda-cyhalothrin (ETR = 4900) and metalaxyl (ETR = 2303). Some compounds gave evidence of multi-level risks: imidacloprid exhibited high risk to all the organisms (earthworms, bees and NTAs); acetamiprid was risky to earthworms and bees, while cypermethrin, emamectin benzoate and lambda-cyhalothrin, were modelled to pose a risk to bees and NTAs. Regulating the use of these perilous pesticides should be encouraged in agroecosystems to protect environmental and human health.

Preliminary investigation on the impact of engineered PVP-capped and uncapped silver nanoparticles on Eudrilus eugeniae, a terrestrial ecosystem model

Recently, the production of silver nanoparticles and their commercial products has generated increased concern and caused a hazardous impact on the ecosystem. Therefore, the present study examines the toxic effect of chemically engineered silver nanoparticles (SNPs) and polyvinylpyrrolidone-capped silver nanoparticles (PVP-SNPs) on the earthworm Eudrilus eugeniae (E. eugeniae). The SNPs and PVP-SNPs were synthesized, and their characterization was determined by UV-vis spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and transmission electron microscopy. The toxicity of SNPs and PVP-SNPs was evaluated using E. eugeniae. The present result indicates that the lethal concentration (LC₅₀) of SNPs and PVP-SNPs were achieved at 22.66 and 43.27 μg/mL, respectively. The activity of antioxidant enzymes including superoxide dismutase (SOD) and catalase (CAT) was increased in SNPs compared to PVP-SNPs. Importantly, we have noticed that the E. eugeniae can amputate its body segments after exposure to SNPs and PVP-SNPs. This exciting phenomenon is named "autotomy," which describes a specific feature of E. eugeniae to escape from the toxic contaminants and predators. Accordingly, we have suggested this unique behavior may facilitate to assess the toxic effect of SNPs and PVP-SNPs in E. eugeniae.

The Survival Response of Earthworm (Eisenia fetida L.) to Individual and Binary Mixtures of Herbicides

Frequent use of herbicides may impose a risk on non-target species. The objective was to test the combined toxic effect of binary herbicide mixtures—metribuzin:halosulfuron and metribuzin:flumioxazin—on non-target earthworms in two test systems: filter paper and a soil toxicity test system. The joint action experiments were independently run twice to substantiate the findings. The most potent individual herbicide was metribuzin, with a 50% lethal concentration (LC50) of 17.17 µg ai. cm−2 at 48 h in the filter paper test. The toxicity of the individual herbicides on the filter paper test was ranked as metribuzin>halosulfuron>flumioxazin. In the soil test, metribuzin and halosulfuron had high toxicity with an LC50 of 8.48 and 10.08 mg ai. kg−1, respectively, on day 14. Thus, the individual herbicide ranking did not change between the filter paper and artificial soil tests. The herbicide’s mixed effect in both test systems showed a consistent antagonistic effect relative to a Concentration Addition reference model. It indicates that the mixtures retracted the herbicide’s action in the earthworms.

Evolution of the earthworm (Eisenia fetida) microbial community in vitro and in vivo under tetracycline stress

Bioremediation of contaminated soil has received increasing attention, and the effects of antibiotic residues on the soil ecological environment are a current research hotspot. Earthworms are the first choice of soil organisms to indicate the degree of soil pollution, and their detoxification mechanism after antibiotic stress must be further explored. Taking Eisenia fetida as the research object, an antibiotic (tetracycline) stress test was carried out in sterile artificial soil. The stress concentrations were set at 0, 0.3, 3, 30, 300 and 600 mg/kg. The ECO method was used to cultivate microbes in earthworms and soil. The carbon source utilization intensity algorithm developed by our team was used for data statistics, and a factor analysis model was constructed to explore the succession process of microbes of earthworms in vivo and in vitro under tetracycline stress. The results showed that there were four processes in the evolution of microbes under short-term tetracycline stress: at 1-3 days, the microbes in worms played a leading role; at 4-5 days, the microbes in the worms and the soil microbes jointly resisted TET stress; after 6-8 days of stress, the microbes in worms still played the main role, but their role was weakened; and after 9-10 days, soil microbes played a leading role, and tolerant microbes appeared. Under long-term stress, the microbes of earthworms in vivo and in vitro were obvious different, and there may be no regulatory relationship. And the factor analysis model is suitable for the analyse of the changes in microbial communities in vivo and in vitro under TET stress. The research results provide a reference method and model basis for the bioremediation of antibiotic-contaminated soil and the study of earthworm detoxification mechanisms, and help agricultural development.

Oxidative stress, growth inhibition, and DNA damage in earthworms induced by the combined pollution of typical neonicotinoid insecticides and heavy metals

Heavy metals pollution of soil and widespread application of neonicotinoid insecticides have caused environmental problems worldwide. To evaluate ecological toxicity resulting from the combined pollution of neonicotinoids and heavy metals, typical representatives of neonicotinoid insecticides (imidacloprid, thiamethoxam, dinotefuran) and heavy metals (cadmium, copper, zinc) were selected as soil pollutants; earthworms were used as test organisms. Analysis of the main and interaction effects of a combined pollution process were performed using a uniform design method. Results showed that the reactive oxygen species (ROS) content of earthworms in most treatment groups was higher during exposure than that of the control group. The malondialdehyde (MDA) and ROS content of earthworms demonstrated relatively low values on the 21st day and increased by the 28th day. The interaction between dinotefuran and Cd had significant antagonistic effects on ROS and MDA. The combined pollution adversely affected both the growth and genes of earthworms and also caused damage to the epidermis, midgut, and DNA. The interaction between imidacloprid and Cd was synergistic to ROS, weight inhibition rate, and Olive tail moment (OTM), but was antagonistic to MDA. Of all the single and combined exposures, Zn as a single chemical affected ROS and DNA damage the most, and MDA was significantly enhanced by imidacloprid. Composite pollutants may create different primary effects and interactions causing potential harm to soil organisms.

Ecological risk assessment of current-use pesticides and biocides in soils, sediments and surface water of a mixed land-use basin of the Pampas region, Argentina

The present study aimed to assess the ecological risk of 30 current-use agricultural pesticides and biocides in the soil, sediments and aquatic organisms of a mixed land-use basin located in the Depressed Pampas Region of Argentina. Risk Quotients (RQs) were used to evaluate the chronic risk in soil and aquatic organisms, while Toxic Units (TUs) were used to assess the acute risk in sediment-dwelling organisms and aquatic biota. Acetochlor, hydroxy-atrazine, glyphosate, AMPA, metolachlor, imidacloprid and tebuconazole were the only pesticide residues detected (>30%) and quantified in all the matrices evaluated. Glyphosate and AMPA showed the highest concentrations, being their mean and maximum levels 27.90-176.00 μg kg^-1 and 270-712.50 μg kg^-1 in soils, 8.28-32.0 μg kg^-1 and 6.85-17.50 μg kg^-1 in sediments, and 1.88-4.36 μg L^-1 and 0.66-1.03 μg L^-1 in surface water. The RQs in soils showed high chronic risk, mainly due to AMPA and imidacloprid. The TUs in sediments showed acute risk in dwelling organisms, mainly due to glyphosate and imidacloprid. RQs assessment showed a range of chronic risk levels according to the site/sampling event, with higher contribution of atrazine and its metabolites, and acetochlor, whereas TUs assessment showed no acute risk in aquatic biota. In contrast to Europe, in Argentina, there are no restrictions regarding the use of atrazine, acetochlor, imidacloprid and glyphosate to protect aquatic life. Thus, it is recommended that the current Argentine pesticide regulations should be modified to prevent ecological risk and protect ecosystems.

Study on the regulation of earthworm physiological function under cadmium stress based on a compound mathematical model

A cadmium (Cd) stress test was carried out on Eisenia fetida in artificial soil. Six Cd concentration gradient solutions (0, 50, 100, 125, 250 and 500 mg/kg) were prepared. Two treatment groups, short-term stress and long-term stress, were established. The former lasted for 10 days, and the latter lasted for 30 days. The Biolog ECO-microplate culture method was used to determine the utilization of the 31 carbon sources by the microbes in earthworm homogenate. The total protein content (TP), peroxidase activity (POD), catalase activity (CAT), superoxide dismutase activity (SOD), glutathione peroxidase activity (GPX), glutathione-S-transferase activity (GST), malondialdehyde content (MDA) and acetylcholinesterase activity (AChE) in earthworm were determined in order to investigate the regulation of oxidative stress and the functional diversity of microbial communities in earthworms under Cd stress. By combining the entropy weight method (EW) and the technique for order preference by similarity to an ideal solution model (TOPSIS), the physiological functional indices of earthworms were assessed objectively and scientifically, and the physiological changes under the different stress periods were evaluated. The results showed that a Cd-tolerant dominant population appeared in the microbial community under Cd stress. In the short-term test, oxidative stress were more effective in coping with Cd stress than the microbial community, and oxidative stress regulated the microbial community functional diversity. Under long-term Cd stress, the regulatory effect was weak or non-existent. In this study, a new evaluation model was established to explore the regulation process of earthworm on its oxidation stress and the functional diversity of microbial communities under Cd stress, and provide a theoretical basis for revealing the detoxification mechanism of earthworms.

Effects of Dual Exposure to the Herbicides Atrazine and Paraquat on Adult Climbing Ability and Longevity in Drosophila melanogaster

Anthropomorphic effects are changing the planet, and therefore, organisms are being exposed to many new biotic and abiotic stressors. Exposure to multiple stressors can affect organisms in ways that are different than the sum of their individual effects, and these interactions are often difficult to predict. Atrazine and paraquat are two of the most widely used herbicides in the United States, and are individually known to increase oxidative damage, affect dopaminergic functioning, reduce longevity, and alter motor ability in non-target organisms. We measured the effects of individual and combined exposure to low doses of atrazine and paraquat on climbing ability and longevity of Drosophila melanogaster. Atrazine and paraquat interact to affect D. melanogaster climbing ability and longevity in different ways. Atrazine appeared to have a weak mitigative effect against the decrease in climbing ability caused by paraquat. In contrast, combined exposure to atrazine and paraquat had detrimental synergistic effects on female longevity. Overall, this study shows that atrazine and paraquat can interact and that it is important to measure several traits when assessing the consequences of exposure to multiple stressors. Future studies should continue to assess the impacts of stressor interactions on organisms, as many combinations have never been examined.

Laboratory and field tests for risk assessment of metsulfuron-methyl-based herbicides for soil fauna

Metsulfuron-methyl is one of the most used sulfonylurea herbicides, being applied alone in pre-emergence and with a mineral oil (as adjuvant) in post-emergence. In risk assessment of pesticides, ecotoxicity tests have been applied to assess the effects of products and mixtures under laboratory conditions, but they are limited in their ecological relevance when compared to field assessments. Considering the differences between laboratory and field exposure, and the lack of data on the effects of metsulfuron-methyl in natural soils, this study consisted in a set of tests to assess the ecotoxicity of this herbicide applied alone, combined with an adjuvant (mineral oil) and the adjuvant applied alone, both under laboratory and field exposure, with artificial and natural soil respectively. Reproduction tests with four non-target soil invertebrates species were performed in laboratory, while two experiments were performed in field evaluating avoidance behaviour, feeding activity, mesofauna abundance and pesticide residual. Laboratory results showed that metsulfuron-methyl alone is not a threat to soil fauna on the recommended doses. However, the presence of mineral oil as adjuvant showed ecotoxicity to Eisenia andrei, Enchytraeus crypticus and Proisotoma minuta on laboratory tests. Field evaluations indicated that metsulfuron-methyl and the adjuvant do not impaired the feeding activity of the soil fauna. The low abundance of native communities could be related to soil management. Results showed that laboratory and field evaluations are necessary to better understanding of the effects of pesticides to soil fauna and adjuvant addition should be considered on pesticides risk assessment.

Assessment of acute toxicity and biochemical responses to chlorpyrifos, cypermethrin and their combination exposed earthworm, Eudrilus eugeniae

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In the present study, co-exposed administered pesticides induced a higher level of toxicity to Eudrilus eugeniae.

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Statistically significant changes were observed after 48 h exposure of CPF, cypermethrin and combination of the two, reflects the synergistic cumulative impact on the AChE and oxidative stress parameters in dose- dependent manner.

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Significant changes were observed in different body segments (Pre-Clitellar, Clitellar and Post-Clitellar) of earthworm in tissue specific pattern.

Recurrent application of chemical pesticides in the agricultural fields have adverse impact on flora and fauna of soil ecosystem. Earthworms immensely contribute in increasing the fertility of soil. They may act as a bioindicator for the ecotoxicological analysis of pesticide induced soil pollution. Earthworms, Eudrilus eugeniae were exposed to different concentrations of pesticides chlorpyrifos (OP), cypermethrin (a pyrethroid) and their combination for 48 h by paper contact toxicity method. The LC₅₀ for commercial grade of chlorpyrifos, cypermethrin and combined pesticides were determined as 0.165, 0.066 and 0.020 μg/cm², respectively. To assess the sub-lethal effect of these pesticides, E. eugeniae were exposed to 5% and 10% of LC₅₀ of the pesticides for 48 h. Variation in morpho-behavioural changes such as coiling, clitellar swelling, mucus release, bleeding and body fragmentation in earthworms were observed after exposure of both pesticides and their combination. Various biochemical estimations such as specific activity of acetylcholinesterase (AChE), superoxide dismutase (SOD), catalase (CAT), glutathione -S-transferase (GST); levels of lipid peroxidation (LPO) and reduced glutathione (GSH) were carried out in different body segments. Significant changes in these stress markers were observed at low and high sub-acute concentration of pesticides exposed earthworm, Eudrilus eugeniae. Such changes indicate potential health risk to E. eugeniae if exposed to the high concentrations of these pesticides accumulated in soil.

Screening indices for cadmium-contaminated soil using earthworm as bioindicator

Artificial soil simulation tests were conducted to study the response of oxidative stress in different parts of Eisenia fetida under cadmium Cd) stress. Factor analysis and analytic hierarchy process were used to establish a comprehensive mathematical model to screen key monitoring indices of the Cd-contaminated soil early warning system. This paper sets the short-term group and the long-term group. The former lasted 10 days, and the latter was 30 days. Gradient solution of 0, 50, 100, 125, 250, and 500 mg kg^-1 Cd²⁺ was used in each test group. The earthworm was cut into two parts from its clitellum to determine oxidative stress indices. Results showed that during the short-term stress, TP (total protein) in the head tissues of the earthworm was the key monitoring index for 3-4 and 8-9 days of Cd stress. In addition, the TP in tail tissues was the key index for 2, 4, 6, and 8-10 days of stress. On the first and second days, the key monitoring indices in the tail tissues were both the CAT (catalase), while in the head, they were CAT and TP, respectively. On the 5th, the 7th, and the 9th days, the focus should be on monitoring POD (peroxidase) in the tail tissues, while in the head tissues, they were POD, CAT, and TP, respectively. In the long-term test after 10 days of Cd stress, the key monitoring index in head tissues was GPX (glutathione peroxidase), and in the tail, it was TP. At 20-30 days, the key monitoring indices were TP in the head and MDA (malondialdehyde) in the tail.

Influence of the chain length of surfactant in the modification of zeolites and clays. Removal of atrazine from water solutions

Removal potentials of a surfactant modified zeolite (SMZ) and clay (SMC) for atrazine adsorption were evaluated. Materials were modified with hexadecyl trimethyl ammonium bromide (HDTMA-Br) and benzyl octadecyl dimethyl ammonium (BODA) chloride considering the critical micellar concentration (CMC) of each one (0.94 and 0.041 meq/L, respectively). The influence of the surfactant was analyzed in detail, particularly the formation of surfactant layers (complete or partial) connected with the length of the surfactant tail (16 and 18 methyl groups or number of carbons in the chain). Raw materials were characterized by XRD and Fourier transform infrared spectroscopy (FTIR), SMZ and SMC were analyzed by FTIR. Results obtained from kinetic adsorption experiments shown that equilibrium time is less for materials modified with HDTMA (8 h) than materials with BODA (10 and 12 h). Materials modified with the largest chain surfactant (BODA) showed more resistance to atrazine masse transference. The chemisorption was presented in the adsorption mechanisms of atrazine and adsorbent materials. Based on the results of adsorption isotherms Langmuir isotherms showed the better correlation coefficients value. The q_max is greater for materials modified with BODA (0.9232 and 4.2448 mg/g) than for materials modified with HDTMA (0.6731 and 3.9121 mg/g). Therefore, SMZ and SMC modified with the largest chain surfactant has more affinity for the pesticide. The removal process at high concentration of atrazine depends of the partition process but at lower concentration, it occurs not only by this process but also by absorption process.

Screening effects of metsulfuron-methyl to collembolans and earthworms: the role of adjuvant addition on ecotoxicity

Metsulfuron-methyl is a common active ingredient recommended for use in pre- and post-emergence control of annual grasses and broadleaf weeds in crops, usually applied with mineral oil as adjuvant to enhance its efficiency. Despite the increasing use of this herbicide, there are no information on its ecotoxicity effects to soil fauna. Avoidance and lethality tests were performed with earthworms and collembolans using tropical artificial soil contaminated with formulated products Ally® (600 g L^-1 metsulfuron-methyl) and Assist® (756 g L^-1 mineral oil) as adjuvant. Lethality test with earthworms showed no difference when tested with or without adjuvant. When Ally® was tested alone, it caused avoidance behavior only at high concentrations (5000 and 10,000 times field predicted dose). However, Assist® addition changed the response of soil invertebrates increasing the avoidance even at field predicted doses. The toxicity of the adjuvant was confirmed in tests exposing collembolans and earthworms to Assist® alone resulting in avoidance behavior. The results clearly show that the addition of mineral oil enhanced the ecotoxicity of metsulfuron-methyl. This study provides an important contribution to the knowledge on the toxicity of metsulfuron-methyl and indicates that adjuvants should be considered in risk assessment of pesticides, considering that under field conditions, these products are applied together.

Study on the influential biochemical indices of Cd(II) on Eisenia fetida in oxidative stress by principal component analysis in the natural soil

With the aggravation of heavy metal pollution in soil, the individual heavy metal content monitoring cannot predict the true effects of harmful substances on the ecosystems. Thus, the effective biological evaluation system should be established to assess the pollution risk caused by heavy metal. Earthworms are widely distributed in the soil, and at the bottom of the food chain, the changes of biochemical indices play an important role in the early warning for heavy metal pollution. Principal component analysis (PCA) is a statistical method that derives several independent principal components from the original variable based on retaining the information as much as possible. This paper is aimed at finding out and analyzing the key monitoring factors related to Cd²⁺ on the earthworm Eisenia fetida in oxidative stress. The Cd²⁺ stress concentrations were set at 0, 1, 10, 20, 100, 200, 400, and 800 mg kg^-1, and the post-clitellum segment of earthworm was chosen to determine TP, POD, SOD, GST, GPX, CAT, MDA, VE, and AChE. The results showed that the main bioindicators associated with oxidative stress reaction were GST, POD, and MDA at the exposure time of 10 days; at 20 days GPX, MDA, and AChE; at 30 days CAT, TP, and GPX; CAT, MDA, and SOD at 40th day. These results indicated that PCA can quickly, effectively, directly, and scientifically select biomarkers of oxidative stress induced by Cd and improve the accuracy and scientificity of earthworm as a biomarker in monitoring and early warning for heavy metal-contaminated soil.

The effect of insecticides chlorpyrifos, α-cypermethrin and imidacloprid on primary DNA damage, TP 53 and c-Myc structural integrity by comet-FISH assay

In parallel with the continuous use of conventional insecticides, introduction of more environmentally friendly substances continues to grow in modern agriculture. In the present study, we evaluated chlorpyrifos, and imidacloprid and α-cypermethrin as two representatives of green insecticides for their genotoxic activity. We conducted a 14-day treatment in extended human lymphocytes cultures using real life exposure relevant concentrations. An alkaline comet assay was used to detect primary DNA damage. Simultaneously, the effect on the specific action towards the TP 53 and c-Myc genes in terms of fragmentation and copy number were determined. Both genes are responsible for cell cycle regulation; thus playing an active role in carcinogenesis. Contrary to what was expected, imidacloprid showed the highest genotoxicity potential, irrespective of the fact that none of the insecticides induced a significant level of primary DNA damage at all tested concentrations. Similar, no significant effect towards the TP 53 and c-Myc gene was recorded. The present study indicates that low level use of chlorpyrifos as a conventional insecticide and imidacloprid and α-cypermethrin as green insecticides does not pose a risk to DNA in general, nor to the TP 53 and c-Myc gene structural integrity.

Ecotoxicity of 1,3-dichloropropene, metam sodium, and dazomet on the earthworm Eisenia fetida with modified artificial soil test and natural soil test

1,3-Dichloropropene (1,3-D), metam sodium (MS), and dazomet (DZ) are widely used as preplant soil fumigants to solve soilborne problems. To provide a more scientific and accurate evaluation of 1,3-D, MS, and DZ toxicity to the earthworm Eisenia fetida, modified artificial soil test and natural soil test were studied. The suitable soil moisture to maintain over 90% survival of the earthworms after 4 weeks of treatment in an enclosed system for modified artificial soil test and natural soil test were 26.9 to 86.4% of water-holding capacity (WHC) and 66.2 to 84.3% of WHC, respectively. The optimal soil moisture levels for modified artificial soil test and natural soil test (75 and 55% of WHC, respectively) were finally used to evaluate the toxicity of 1,3-D, MS, and DZ on earthworms. Each desiccator with 10 earthworms and natural or artificial soil was stored at 20 ± 1 °C under constant light of 400 to 800 lx for 2 weeks. The modified artificial soil test showed LC₅₀ values for 1,3-D, MS, and DZ of 3.60, 1.69, and 5.41 mg a.i. kg^-1 soil, respectively. The modified natural soil test of the fumigants showed similar LC₅₀ values of 2.77 and 0.65 mg a.i. kg^-1 soil, except for DZ at 0.98 mg a.i. kg^-1 soil. The present study confirms that both modified artificial soil test and modified natural soil test offer standard methods for acute toxicity test of 1,3-D, MS, and DZ on the earthworms and scientific evidences for assessing the effects of soil fumigants on non-target organisms in the soils. Graphical Abstract Two novel acute toxicity test methods for soil fumigants on the earthworm Eisenia fetida.