Herbicide Concentrations Research Articles

Effects of environmentally relevant concentrations of atrazine and glyphosate herbicides, isolated and in mixture, on two generation of the freshwater microcrustacean Daphnia magna.

The herbicides atrazine and glyphosate are used worldwide and their excessive usage results in the frequent presence of these pesticides in environmental compartments. We evaluated the effects of environmentally relevant concentrations of analytical standards and commercial formulations of atrazine (2 µg L-1) and glyphosate (65 µg L-1), isolated and in mixture (2 + 65 µg L-1) on the microcrustacean Daphnia magna. Through chronic exposure (21 days) of two generations, we observed effects on survival, reproductive capacity and responses of the antioxidant defense system (catalase) and biotransformation system (glutathione S-transferase). The survival of organisms was affected in the second generation (F1) with a mortality of 17% in the mixture of commercial formulations treatments. In the evaluation of the first generation (F0) we observed only effects on sexual maturation of organisms, while in the F1, changes were observed in all parameters evaluated. A statistical difference (p < 0.05) was also observed between the analytical standards and the commercial formulations for all parameters evaluated, indicating that other components present in the formulations can change the toxicity of products. We suggest that atrazine can modulate toxicity when mixed with glyphosate, as the standard analytical atrazine and mixture of analytical standards results were similar in most parameters. Given the difficulty in estimating effects of mixtures and considering that various stressors are found in the environment, our results support the need to carry out long-term studies and, above all, to verify what are the impacts across generations, so that the toxicity of products is not underestimated. Graphical abstract.

Biochemical and body condition markers in Rhinella icterica tadpoles exposed to atrazine, glyphosate, and quinclorac based herbicides in ecologically relevant concentrations

Amphibians have suffered population decline due to several factors, including exposure to pesticides. In the south of Brazil, rice cultivations use herbicides based on atrazine, glyphosate and quinclorac as the commercial formulations Primoleo®, Roundup® and Facet®, respectively. Rhinella icterica was chosen to evaluate oxidative balance markers and body condition after exposure to three concentrations of herbicides (10, 20 and 40 µg/L of atrazine and quinclorac; 100, 250 and 500 µg/L of glyphosate). These xenobiotics, regardless of the concentrations used, accelerated the development process of animals and seemed to act as modulators of development. We observed no significant variations for any of the oxidative balance markers studied (superoxide dismutase, catalase, TBARS and carbonylated proteins); however, we cannot rule out that other antioxidant system components prevent oxidative stress. In general, atrazine and glyphosate accelerated the development of tadpoles, and quinclorac retards this process, which could impact the survival of these animals.

Application of global sensitivity analysis in identification of herbicides cocktail effects at environment-related concentrations

<p indent="0mm">The use of herbicides in crop production continues to increase globally. By 2015, China had become one of the most important producers and consumers of herbicides in the world. Many herbicides are persistent organic pollutants and are used continuously for long periods of time, causing the high residual concentrations in the water surrounding farmland and negative effects on aquatic life. The concentrations of herbicides in the environmental water are variable and the types of herbicides are diverse. Herbicide mixtures in surface water may threaten aquatic life. However, in most areas of China, the hazard of herbicide mixtures associated with environmental exposure levels has not been assessed. This paper establishes a hazard identification assessment method for mixtures with environment-related concentrations. Firstly, the hazard of individual pollutant was assessed by hazard quotient (HQ), and the pollutants with high hazards (HQ≥1) to target organisms were further studied. Secondly, the global sensitivity analysis (GSA) based on Morris method was used to study combined effect, and identify the important or hidden drivers in chemical mixtures. In brief, the GSA experimental design consists of four steps: Input factors (target pollutants), Morris sampling, high-throughput screening, and the sensitivity analysis. Thirty-nine herbicides detected in the surface water of Tai Lake and Liao River were screened by HQ with <italic>Scenedesmus obliquus</italic> (<italic>S</italic>.<italic> obliquus</italic>) individually. The herbicides with high hazard were the input factors of GSA. Then, the Morris method was used to generate 150 samples of mixtures. The <italic>S</italic>.<italic> obliquus </italic>was exposed to 150 samples for <sc>24 h</sc> and subjected to high-throughput screening. Finally, the sensitivity analysis was used to identify the important or hidden drivers of the herbicide mixtures. The results showed that 14 herbicides had high hazards (HQ≥1) among 39 herbicides detected in Tai Lake and Liao River basin. Ametryn and diflufenican had higher hazards to algae. At the individual herbicide exposure of <sc>500 μg/L,</sc> most herbicides, except C5 and C10, significantly inhibited the growth of <italic>S</italic>.<italic> obliquus </italic>(<italic>P</italic>&lt;0.05). And the strongest growth inhibition effect caused by individual herbicide was about 40%. The results of 150 samples of mixtures with environment-related concentration showed that most of the mixtures had growth inhibition effects on <italic>S</italic>.<italic> obliquus</italic>. The total concentrations of the mixtures that consist of 14 herbicides are not greater than <sc>79 μg/L.</sc> And the strongest growth inhibition effect caused by mixture samples was over 50%. The toxicity of herbicide mixtures cannot be ignored. The growth inhibition effect of the mixtures that consist of 14 herbicides on <italic>S</italic>.<italic> obliquus</italic> was nonlinear, and there are strong interactions between herbicides. It is difficult to predict the toxic effects of the mixture system from the exposure concentration of individual herbicides. According to the <italic>μ*</italic> value, the most important factors in the combined pollution were terbutryne, bensulfuron methyl, atrazine, and ametryn. Bentazone had the lowest <italic>μ*</italic> and contributed little to the overall mixture system. And bensulfuron methyl was the hidden driver of the mixture system. The important drivers in the herbicide mixtures need to be focused, and their concentrations should be monitored regularly to control emissions and minimize the negative effect on aquatic life. Global sensitivity analysis based on Morris sampling can identify the important factors in cocktail effects of mixtures in limited samples, providing technical support for incorporating the actual toxic effects of mixtures into the risk assessment of pollutants.

Allium cepa'nın Somatik Hücreleri Üzerine Oxyfluorfen’in Sitotoksik ve Genotoksik Etkileri

In this work, the cytotoxic and genotoxic influences of oxyfluorfen herbicide were surveyed by examining of mitotic index, mitotic stages, chromosomal anomalies, micronucleus percentage, and comet assay parameters on the somatic cells of Allium cepa. The roots were treated with 0.2, 0.4, 0.8 and 1.6 ppm herbicide concentrations with 12, 24 and 36 h. application periods. Mitotic index was noticeably diminished by oxyfluorfen in each application group when matched with their control, except for 0.2 ppm. The percentages of mitotic stages were altered. Oxyfluorfen enhanced drastically the aberrant cell ratio at all application groups and application periods in contrast to their control, excluding 0.2 ppm. Mitotic anomalies were noted as disturbed prophase, stickiness, C-mitosis, chromatid bridges and laggards. The micronucleus was detected at interphase and its percentage was determined in the applied concentrations. Also, the comet assay was employed to examine the single strand breakages. Almost all of the used concentrations of oxyfluorfen increased DNA losses. A positive relationship was discovered between micronucleus occurrence and DNA loss.

In vivo microcapillary sampling coupled with matrix-assisted laser desorption/ionization fourier transform ion cyclotron resonance mass spectrometry for real-time monitoring of paraquat and diquat in living vegetables

An in vivo microcapillary sampling (MCS) method coupled with matrix-assisted laser desorption/ionization fourier transform ion cyclotron resonance mass spectrometry (MALDI-FTICR-MS) analysis was utilized to monitor the real-time bipyridine quaternary ammonium herbicides concentrations and assess their uptake and elimination behaviors in living cabbage plants noninvasively. Under optimized conditions, the proposed method for paraquat (PQ) and diquat (DQ) determination showed wide linear ranges (7.81–500 μg/kg), low limits of detection (0.1–0.9 μg/kg), and good reproducibility. In vivo tracking results demonstrated that different absorption behaviors between PQ and DQ existed in living vegetables and DQ was more easily absorbed. Through decay kinetics model fitting, herbicide half-lives were 1.32 and 1.86 days for PQ and DQ, respectively. To summarize, in vivo MCS method provides valuable information on herbicide risks for agricultural production, which is suitable for temporal, spatial, and longitudinal studies in the same living system and multicompartmental studies in the same organism.

Bioremediation Performance of Sphingomonas melonis and Bacillus muralis on Herbicide Diquot Dipremide-(ethylene-d4)

Bioremediation is a process that utilizes the degradation potential of microorganism to provide a cost-effective and reliable approach for pesticide biodegradation. For this purpose, chosen bacteria Sphingomonas melonis and Bacillus muralis were isolated from an agricultural soil sample. The biodegradation performance of these isolated bacteria at different Diquot Dipremide-(ethylene-d4) (DDE4) herbicide concentrations (250, 500 and 1000 ppm) was investigated under submerged culture conditions. Biodegradation performance of isolated bacteria was monitored with COD, TOC and, BOD5 reduction rates in culture medium at different incubation periods. According to the results; S. melonis has the highest bioremediation capacity for COD removal (91% at 250 ppm). For TOC, B. muralis has the highest removal rate as 82% at 250 ppm. On the other hand, For BOD5 at 250 ppm 85% S. melonis showed the best removal performance. Most effective removal rate at 250 ppm concentrations was obtained as 91% and 88 by S. melonis and B. muralis respectively at the end of the 216th hour for COD. Additionally, the increase in turbidity related with population dynamics at the end of the 216 th hour positively effected the bioremediation parameters included COD, TOC and BOD5 reductions. These results showed that it can be used for effective COD, TOC and BOD5 removal in S. melonis and B. muralis on DDE4 remediation.

Trifluralin and Corn Residues for Weed Management in Mung Bean Fields, Central Iraq

A field experiment was conducted at two sites (Baghdad and Wasit Governorates) to evaluate the effects of allelopathic corn residues applied as soil incorporation or mulch, alone and in combination with reduced (50% of recommended dose) rate of trifluralin herbicide on weeds growth and mung bean yield. Conventional soil tillage and zero soil tillage treatments with corn residues were performed, while 50% dose and full dose of trifluralin only (without residues) treatments were included for comparison. Soil incorporation and mulch of corn residues reduced weed density and dry weight biomass and improved yield and yield components of mung bean in both sites. Mulch application was more effective than soil incorporation for weed control. However, the reduction in weed growth and the increase in mung bean yield were below the levels achieved by the label dose of herbicide. Application of 50% dose of trifluralin in plots incorporated or mulched with corn residues reduced weeds and scored yield similar to that achieved by 100% herbicide dose applied in both conventional and zero tillage plots. Chemical analysis revealed the presence of higher phenolics in plots amended with incorporated and mulched corn residues compared to their control plots. Chemical analysis also revealed that the periods of maximum quantities of phenolics paralleled with the periods of maximum suppressive activity against weed tested under field condition, which explains the phytotoxicity of phenolics on weed suppression. Such approach may help in reducing reliance upon high concentrations of trifluralin herbicide, improving the sustainability of agroecosystem, improving environmental safety, mitigating human health risks, and reducing the ability to tolerate herbicides.

Use of superoxide dismutase activity indicator in the system of surface water ecological monitoring

The usage of herbicides is increasingly spreading both in the world and in Ukraine. Constant monitoring of this type of the polluting substances is one of the areas for maintaining the ecological security. It is significant for diverse environmental objects, especially for the surface water sources. Contemporary herbicides have a wide range of various mechanisms of action. In this regard, applied methods have to ensure the high level of sensitivity and reasonable specificity for measuring the excessive concentrations of herbicides in the environment. Besides, it is considerable to choose appropriate test organisms. They have to satisfy the list of requirements, while the most important one is that it would be a hydrophyte that has full contact with water. Therefore, the Elodea canadensis Michx. has been chosen by us as a test object. This species is a cosmopolitan and is widely used for the bioassay procedure.&#x0D; The system of biochemical transformations is one of the most sensitive links for the maintenance of the cell homeostasis. Typically, enzymes react to the stress-induced variation in environmental situation by modification of their activity. Consequently, this fact is used for the stress assessment of the organism. We have offered to measure the enzymatic activity of superoxide dismutase (SOD) as the most remarkable system biomarker on the toxic impact of the herbicides. The main function of SOD is the prevention of the growing oxidative stress in the cell. Thus, it can serve as an integral index that acts on the influence of varied chemical substances.&#x0D; For this reason, the aim of the research paper is to indicate the specific changes in the SOD activity of the Elodea canadensis’ cells in conducting the bioassay of the herbicides of varied groups. &#x0D; The aim was achieved through the investigation of the dynamical changes in the SOD activity of Elodea canadensis. The water plant had contact with varied groups of the herbicides in different concentrations.&#x0D; As a result, we have discovered the high sensitivity of the SOD activity of Elodea canadensis while being immersed into water with different herbicides. Hence, this test can be recommended for use to determine the contamination of water with pesticides.&#x0D; We recommend using a one-day experiment for the most representative results to explore the dynamical changes in the enzyme activity of elodea in herbicide solution. &#x0D; The elaborated bioassay method has the following advantages: quickness, accessibility and sensitivity. The absence of the specificity in similar studies can refer to disadvantages. Howsoever, it can also refer to advantages if the screening is conducted for a wide range of contaminations.

Conductive polymer layered semiconductor for degradation of triclopyr acid and 2,4-dichlorophenoxyacetic acid from aqueous stream using coalesce adsorption-photocatalysis technique

Polyaniline supported titanium dioxide nanoparticles (PTs) were fabricated using chemical oxidative aniline polymerization in the presence of titanium dioxide with ammonium peroxydisulfate as an oxidant. The synthesized PTs were thoroughly characterized for their morphological and functional features. PTs were employed for the photodegradation of acidic herbicides; 2,4-dichlorophenoxyacetic acid (2,4-D) and triclopyr acid (TCP). PT's surface modifications were imparted and their herbicide removal efficiencies were compared. The best operating conditions for adsorption/photocatalysis were 0.5 g/L photocatalyst, 10 mg/L concentration of individual herbicides resulted in 90.72% removal of TCP at pH 4 and 99.91% removal of 2,4-D at pH 5. Adsorption kinetics of herbicides, onto PT-1 showed the equilibrium attainment within 30 min and experimental data obeyed pseudo-second order model for TCP and 2,4-D removal which was governed by chemisorption. Analysis of TCP and 2,4-D adsorption indicated that the removal followed Sips model for TCP removal while Redlich-Peterson model explained the removal of 2,4-D by PT-1. Rate constants indicated that the amount of TiO2 in the PTs played an important role in removing the herbicides and PT-1 material excellent remarkable activity for three cycles of photodegradation. Thus, this work reports the polymerization of aniline onto TiO2 and their utility as photocatalyst for the expulsion of 2,4-D and TCP from water.

Utility of roller wiper applications of dicamba for Palmer amaranth control in soybean.

BACKGROUNDThe commercialization of dicamba‐resistant soybean has resulted in increased concern for off‐target movement of dicamba onto sensitive vegetation. To mitigate the off‐target movement through physical drift, one might consider use of rope wicks and other wiper applicators. Although wiper‐type application methods have been efficacious in pasture settings, the utility of dicamba using wiper applicators in agronomic crops is not available in scientific literature. To determine the utility of roller wipers for dicamba applications in dicamba‐resistant soybean, two separate experiments were conducted in the summer of 2020 and replicated in both Keiser and Fayetteville, AR, USA.RESULTSUtilizing opposing application directions and a 2:1:1 ratio of water: formulated glyphosate: formulated dicamba were the most efficacious practices for controlling Palmer amaranth. The high herbicide concentrations and wiping in opposing directions increased dicamba‐resistant soybean injury when the wiper contacted the crop, but no yield loss was observed because of this injury. Broadcast applications resulted in greater Palmer amaranth mortality than roller wiper applications, and the most effective roller wiper treatments were when two sequential applications were made inside the crop canopy.CONCLUSIONSDicamba applications require adequate coverage for optimum weed control. While efforts can be made to increase roller wiper efficacy by optimizing coverage and timing of applications, broadcast applications are superior to roller wiper applicators for weed control. Roller wiper applications did not reduce soybean yield, thus wiper‐type applications may be safely used in dicamba‐resistant soybean, albeit the likelihood for off‐target damage caused by volatilization of these treatments would need to be investigated. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Detecting long temporal trends of photosystem II herbicides (PSII) in the Great Barrier Reef lagoon

The Marine Monitoring Program (MMP) was established in 2005 to monitor the inshore health of the Great Barrier Reef (GBR) and evaluate progress towards water quality objectives in Reef Water Quality Improvement Plans. The MMP provides information on the magnitude and spatial extent of pesticide contamination, reports on temporal variability, and provides a risk assessment for the biota in the GBR lagoon. However, long-term trends in pesticide contamination of inshore marine waters over the entire monitoring period (2005–2018) have not been assessed. We used up to 14 years of monitoring data for five PSII herbicides (ametryn, atrazine, diuron, tebuthiuron, and hexazinone) to conduct temporal trend analyses at 11 inshore monitoring sites. The trend analyses suggested increasing significant trends (p < 0.05) for the five PSII herbicides concentrations at several monitoring sites. Power analysis indicated that monitoring sites with over 10 years of monitoring data had convincing results with 80% power.

Simultaneous monitoring of the photocatalytic degradation process of trifluralin and pendimethalin herbicides by SBA-15/TiO2 nanocomposite

Today, The occurrence of herbicides in environments attitudes a potential hazard to aquatic life and displays development forbidding of human embryonic cells, therefore their elimination from the environment is a vigorous job. In this paper, the SBA-15/TiO2 nanocomposite were synthesized utilizing amorphous nanosilica, which was extracted from stem cane ash (SCA) with 92.56% purity. FESEM and TEM images of pure SBA-15 and SBA-15/TiO2 nanocomposite demonstrates which their mean particle size was under 50 nm. The average particles size of TiO2 anatase calculated to be 27.6 nm using the Scherrer’s equation. The BET surface area, total pore volume and average pore diameter of the SBA-15/TiO2 was obtained to be 279.2 m2 g−1, 0.39 cm3 g−1 and 5.64 nm, respectively. For the first time, this nanocomposite was used as photocatalysts for degradation of trifluralin (Tri) and pendimethalin (Pen) herbicides in the aqueous solution. Partial least squares-1 (PLS-1) regression was used for simultaneous measurement of them in aqueous solutions before and after photocatalytic degradation with SBA-15/TiO2 nanocomposite. The values of some parameters such as R2(0.9951, 0.9872), recovery (101.5, 102.0%) and root mean square error of prediction (0.231, 0.239) for both Tri and Pen were attained by the PLS-1 regression, respectively. The influence of some operational parameters such as initial herbicide concentrations, photocatalyst dosage, irradiation time and pH were also investigated on the photocatalytic performance using the response surface methodology. Conferring to the ANOVA test, the most important factor on the decomposition of herbicides was photocatalyst dosage. The results displayed that the maximum elimination efficiencies under the optimum conditions (pH = 10, photocatalyst dosage 0.2 g L−1, irradiation time 30 min and initial herbicide concentration 60 mg L−1) from the river water for Tri and Pen were attained to be 90% and 82.5%, respectively.

Natural and anthropogenic influences on benthic cyanobacteria in streams of the northeastern United States

Benthic cyanobacteria are widespread in streams and rivers and have the potential to release toxins. In large numbers, these microorganisms and their toxins present a risk to human health. Cyanobacterial abundance in stream biofilms is typically related to single or a limited set of environmental factors, mainly light availability, water temperature, and nutrient concentrations. However, these factors may act synergistically with watershed characteristics and other stressors, such as anthropogenic pollutants, to affect cyanobacteria. We investigated the influence of multiple regional and local variables on the abundance of benthic cyanobacterial genera in streams using all subsets generalized additive modeling. We examined watershed factors (topography, geology, and climate) alongside in-stream factors (geomorphology, hydrology, pH, specific conductance, nutrients, organic contaminants, and dissolved metals) from 76 sites along an urban gradient in the northeast United States. Each genus responded to a distinct combination of environmental variables, demonstrating strong intergeneric variation in environmental selection of realized niches. Four of the 7 potentially toxigenic genera that we modeled were positively influenced by water temperature or nutrients. Nonetheless, watershed characteristics, streamflow, and/or other water quality pollutants were equally or more influential for the potentially toxigenic genera. Additionally, the relationships between cyanobacterial abundance and environmental factors varied in shape and direction across many genera. In particular, with increasing concentrations of herbicides, polychlorinated biphenyls, or metals, the abundance of roughly half of the affected genera decreased, while the others increased. These results likely demonstrate novel toxic effects of the pollutants on cyanobacterial genera in the environment, while indicating that unmeasured biotic interactions may lead to positive responses for other genera. Our results emphasize the need to consider variables beyond those that are most frequently measured or implicated (e.g., water temperature and nutrients) to more fully understand the environmental conditions that influence the distributions and abundance of potentially harmful cyanobacteria.

Optimization of ultrasound-assisted extraction of herbicides from soil and rice using Response surface modelling

ABSTRACT A simple, efficient and cost-effective ultrasound-assisted extraction method for the quantification of penoxsulam, anilofos, bispyribac sodium, butachlor and pretilachlor from soil and rice was developed and validated. Three independent variables, including ultrasonication temperature, ultrasonication time, type and volume of solvent, were studied by single-factor experiments. Box–Behnken design (BBD) was also used to determine the optimal parameters for efficient extraction of penoxsulam, anilofos, bispyribac sodium, butachlor and pretilachlor herbicides from soil and rice. Under optimum conditions, the mean percent recoveries ranged from 82.1 ± 3.32 to 93.8 ± 2.56 from soil and rice grain with relative standard deviation <10% and limit of quantification less than the maximum residue limits imposed by principal regulatory agencies. Results depicted that the experimental values were consistent with the predicted values, indicating that RSM is accurate and reliable method to find the optimal UAE extraction conditions for studied herbicides from soil and rice. Furthermore, the greenness was evaluated using AGREE metrics, and UAE was found to be a greener and efficient method for the determination of herbicides from soil and rice. The developed method was extended to the analysis of real samples and concentration of herbicides at 0 day in soil samples varied from 0.483 ± 1.65 to 1.420 ± 1.41 µg g−1. At harvest, the concentrations of herbicides in soil and rice were below the permissible limit (<0.01 µg g−1).

Salicylic acid enhances tolerance of Valeriana officinalis L. to bentazon herbicide

Salicylic acid is an important phytohormone, with regulation role in responses of plants to biotic and abiotic stress, especially detoxification of herbicides. For this purpose, the effect of three rates of salicylic acid (SA) (zero, 0.5, and 1 mM) and six doses of bentazon (zero, 50%, 75%, 100%, 125%, and 150% of recommended dose) on physiological response of valerian (Valeriana officinalis L.) were evaluated in the completely randomized factorial design with three replicates. The results showed that application of bentazon, especially at high levels (125% and 150% of recommended dose, in the absence of SA, exacerbated the rate of phytotoxicity damage, malondialdehyde (MDA) content, catalase (CAT), gaiacol peroxidase (GPX), and ascorbate peroxidase (APX) activity. Exogenous application of SA positively impacted bentazon- and unbentazon-exposed (control) plants, even under elevated concentration of herbicide (50% higher than recommended dose). Highest protection of the bentazon-exposed plants was observed at 0.5 and 1 mM level of SA, respectively. Combination of exogenous application (pre-treatment) of SA and bentazon herbicide reduced MDA content compared with ones were exclusively bentazon-exposed. In addition, exogenous application of SA enhanced antioxidant enzyme system, and increased APX and GPX enzyme activity. Results of present research indicated that external application of SA could be able to increase tolerance to oxidative stress generated in bentazon-exposued plants of valerian by reducing phytotoxicity and mutating antioxidant enzymatic system and antioxidant metabolites content.

Effect of Paraquat Herbicide on Oxidative Stress Biomaker Enzyme Activities in C. Gariepinus

Toxicity assessment was conducted for 96hr exposure duration using synthetic herbicide (paraquat dichloride 276g/L) on Claris gariepinus with mean weight range of 27.2 - 29.7g and mean length 10.95 -15.5cm. They were exposed to varying herbicide concentrations of 0.0, 3.45, 6.90, 10.35 and 13.5mg/L with 5-levels exposure concentrations in a Completely Randomized Design (CRD). Liver, gills and kidney tissues were analyzed for oxidative stress enzymes activities using Solarbio science assay kit (BC1170, 0170 and 0020). Four days lethal concentration (LC50) value for 96hr was found to be 7.298mg/L. The treated fish displayed erratic swimming with irregular opercular movement, loss of reflex, mucus secretion and increased air gulping with the increasing concentration of the herbicide compared with the control fish. Antioxidant biomarkers activities revealed that Glutathione S-transferase (GST), catalase (CAT) and superoxide dismutase (SOD) activities increased significantly (P&lt;0.05) in the gills, liver and kidney tissues at higher concentrations compared with control. It can be deduced that alterations in the oxidative stress enzyme activities in the exposed fish to paraquat exert toxic effect on the liver, gills and kidney tissues. It is therefore recommended that appropriate authorities should develop strategies on minimizing the indiscriminate use of synthetic herbicides due to their impact on aquatic biota such as fish in order to reduce its potential risk to other non-target organisms.&#x0D; Keywords: Clarias gariepinus, Lethal concentration, Oxidative Stress enzymes, Paraquat, Toxicity assessment

Uticaj simuliranih ostataka imazetapira na sadržaj ukupnih proteina u korenovima različitih gajenih biljaka

The bioassay conducted in controlled conditions was used to investigate the sensitivity of selected crops (maize, sunflower, wheat, sugar beet, oilseed rape and mustard) to imazethapyr carryover. The dešendence of whole protein content in test plants roots was measured in regard to different imazethapyr concentrations in the soil. The rates of imazethapyr were established at 240, 120, 60, 30, 15, 7.5, 3.75 and 1.875 mg A.I. kg-1 soil (ppbw). After sowing, the plants were grown in a growth chamber for 14 days and afterwards carefully removed from the pots intact, while the soil was removed from the root system by gentle and thorough washing. Whole protein contents were established based on the nitrogen content in roots using distillated method. Each treatment was performed in four replications and bioassays for each plant species were repeated twice. Statistical analysis of the whole protein content was based on ANOVA, and Tuckey test was used to determine the significant differences. There was no dependence of the whole protein content on herbicide concentration. A slight increase of the whole protein content was determined in maize roots. The same goes for sugar beet, mustard and oilseed rape. In wheat roots and sunflower roots there were a decrease in the whole protein content for some treatments in comparison to control (imazethapyr concentrations ≥ 15 mg A.I. kg-1 soil, for wheat and ≤ 7.5 mg A.I. kg-1 soil, for sunflower). If results obtained in this study are considered together with earlier established level of sensitivity to imazethapyr, one can say that in highly sensitive species there is always an increase in the whole protein content in herbicide treatments when compared to the control. In wheat roots (the least sensitive of plant species tested here) a decrease of the whole protein content was observed and only for higher herbicide concentrations.

ECOLOGICAL AND TOXICOLOGICAL ASSESSMENT OF THE HERBICIDE EXPOSURE DIRECTOR, W.S. (A.I. ISOPROPYLAMINE SOLT GLYPHOSATE, 410 G/DM3) ON BRANCHED CRUSTACEANS CERIODAPHNIA AFFINIS LILLJEBORG

Analysis of the chronic experiments results showed that the herbicide Director (active ingredient - isopropylamine salt of glyphosate, 41%) is a substance toxic to Ceriodaphnia affinis. This herbicide is characterized by embryotoxicity. Herbicide Director has the greatest toxic effect on C. affinis at a concentration of 50 mg/dm3. All major bioparameters of crustacean activity are suppressed. There is a high mortality of first-generation crustaceans (78%) planted in solutions with the herbicide, low life expectancy of females. The offspring born to females in a number of generations are unviable; reproduction of offspring is suspended mainly at the level of the second generation. Only one female from the second generation offspring on the 8th day gave 4 juveniles of the third generation of the 1st brood, which died a day later. At 50 mg/dm3 offspring reproduction is suspended at the level of the second generation. The productivity of females at the herbicide concentration of 25 mg/dm3 is reduced by 66.5% compared with the control. The productivity decrease at lower concentrations was in the range of 30.4 ÷ 17.6%. The smallest decrease in female productivity (by 9.2%) was observed at a concentration of 0.001 mg/dm3. At the herbicide concentration of 25 mg/dm3, the puberty of young C. affinis was delayed and was longer than in the control and at lower concentrations by 1.42 days. Females gave only 5 generations, while in the control and in the concentration range of 0.001–10 mg/dm3 for the same period there were 6 generations. The total number of offspring on average for 5 generations was 33.58% of control, with a reliability of&gt; 99.9%. To a lesser extent, inhibition of crustacean activity was observed at lower herbicide concentrations. At 10 mg/dm3, the sexual maturity of crustaceans was delayed only in the first generation, and the total number of offspring on average for 6 generations was 72.1% of control. At the same level, a decrease in total productivity was observed at concentrations of 1.0 and 0.1 mg/dm3.

The Fate of Atrazine in Tropical Environments: Photolysis, Acute Toxicity and Endocrine Disruptor Potential

Triazine herbicides are widely used both in Brazil and internationally and are frequently detected in natural environments and drinking water. This study assesses atrazine degradation through solar radiation under tropical conditions and determines the toxicity of the intermediates. Atrazine degradation is tested through ultrapure water, humic acid solution and natural water experiments, with exposure to sunlight to simulate a natural environment. A yeast estrogen screen (YES) assay and Artemia salina test are carried out during the abiotic degradation. The atrazine degradation depends on the radiation intensity, since the experiments conducted in the summer reached 50% after ca. 17 days. No significant variations in this herbicide concentration are observed after 90 days of exposure in the fall. Atrazine degradation is observed only in humic acid and is responsible for indirect photolysis. Intermediates, namely, desethylatrazine (DEA) and deisopropylatrazine (DIA), are identified and quantified at the μg L–1 level. Thus, with the degradation of atrazine in water, the medium toxicity may decrease, since DEA and DIA have mean effective concentrations that kill 50% of Artemia salina (EC50) similars to atrazine (13 mg L–1). No estrogenic activity in the YES is detected for atrazine and its metabolites. These findings evidence that radiation intensity and organic substances in tropical countries influence the half-life of pesticides in aquatic environments.

Impacts of Herbicide Oxadiargyl on the Lifespan, Fecundity and Development of a Detritivore Springtail, Cyphoderus javanus

Collembolans are tiny ubiquitous apterygote soil arthropods which plays a pivotal role in soil genesis, organic residues disintegration and soil fertility. The present study was focussed to investigate the deleterious effects of commonly used herbicide oxadiargyl on the lifespan, fecundity and development of an ecologically significant detritivore collembolan Cyphoderus javanus. Extensive application of herbicides had a significant effect on survival rates, fecundity, longevity and growth of Cyphoderus javnaus. The results revealed that rise in the concentration of herbicide negatively affects the survival rates and life history traits of this collembolan. In addition to killing non-target insects, indiscriminate utilization of herbicides in agricultural fields can cause unfavourable changes in the biological balance as well as results in environmental degradation.