High Concentrations Of Atrazine Research Articles

Prenatal exposure to pesticide mixture in Argentina: A pilot study in puerperal women from Santa Fe province

AbstractIntroductionThe epidemiological investigation of congenital anomalies (CA) represents a challenge due to the multiplicity of associated risk factors, notably environmental ones. The monitoring of genotoxic effects in different populations is a useful tool in human biomonitoring and has great biological importance in estimating the exposure risks to complex mixtures of chemical substances.ObjectiveThis study aimed to determine the presence of environmental xenobiotics and evaluate their genotoxic effect, in mothers of newborns with and without CA, and the possible association/correlation between those biomarkers and CA.Materials and methodsA descriptive case and control cross‐sectional study was developed on 290 postpartum women from Santa Fe, Argentina.ResultsSignificant differences were observed between both groups, for places of residence and gynecological variables. Metabolites of organochlorine (OC), organophosphate (OP), and pyrethroid (PYR) pesticides were detected. The most frequently detected compounds were atrazine (ATZ) (57.14%), carbendazim (CBZ) (46.42%), and methylparaben (46.42%), among others. A positive correlation was found between the number of pesticides in blood and genotoxic variables. On the other hand, mothers of children with genitourinary anomalies were the ones with the highest concentrations of ATZ and OP.Discussion and conclusionThese results showed a deep background in the health reality of Santa Fe, which could greatly impact the health of future adults, who have been born preterm. On the other hand, the mixture of pesticides detected confirms the environmental living conditions of women and the transplacental exposure to these compounds in each pregnancy. The potential effects on long‐term descendent health are unknown and unpredictable.

Characteristics of bacterial community and extracellular enzymes in response to atrazine application in black soil

The ecological functioning of black soil largely depends on the activities of various groups of microorganisms. However, little is known about how atrazine, a widely used herbicide with known harmful effects on the environment, influences the microbial ecology of black soil, and the extracellular enzymes related to the carbon, nitrogen and phosphorus cycles. Here, we evaluated the change in extracellular enzymes and bacterial community characteristics in black soil after exposure to various concentrations of atrazine. Low concentrations of applied atrazine (10 – 20 mg kg−1) were almost completely degraded after 120 days. At high concentrations (80 – 100 mg kg−1), about 95% of the applied atrazine was degraded over the same period. Additionally, linear fitting of data indicated that the total enzymatic activity index (TEI) and bacterial α-diversity index were negatively correlated with atrazine applied concentration. The atrazine had a greater effect on bacterial beta diversity after 120 days, which differentiated species clusters treated with low and high atrazine concentrations. Soil bacterial community structure and function were affected by atrazine, especially at high atrazine concentrations (80 – 100 mg kg−1). Key microorganisms such as Sphingomonas and Nocardioides were identified as biomarkers for atrazine dissipation. Functional prediction indicated that most metabolic pathways might be involved in atrazine dissipation. Overall, the findings enhance our understanding of the factors driving atrazine degradation in black soil and supports the use of biomarkers as indicators of atrazine dissipation.

Effect of herbicides on cellular growth, microbiological and physiological activities of an identified rhizosphere isolate Rhodococcus erythropolis

ABSTRACT Considering the excessive pesticide pollution in the environment, atrazine (ATZ), butachlor (BCR) and quizalofop-p-ethyl (QUIZ) were selected to assess their toxic effect on Rhodococcus erythropolis PSB-6 (NCBI Accession No. MG028649). MIC values of ATZ, BCR and QUIZ to R. erythropolis were determined to be 100, 200 and 150 μM, respectively. Biomarker enzymatic assays including LPO, LDH and oxidative stress (CAT) induced by herbicides represented significant (p ≤ 0.005) toxicity towards strain PSB-6. Herbicide-induced morphological changes viz. aberrant margins; cellular cracking and distortion/damage in R. erythropolis cells were apparent under SEM observation. Furthermore, herbicide-treated and DAPI (4’,6-diamidino-2-phenylindole)-stained cells showed concentration-dependent reduction in cellular permeability as revealed under CLSM. Furthermore, herbicides displayed toxicity towards bioactive molecules of PSB-6 in a dose-related manner. Among them, ATZ imparted maximum negative effect, where it reduced the bacterial production of IAA, ACC deaminase and 2, 3-DHBA by 68% (p ≤ 0.001), 75% (p ≤ 0.001), and 83% (p ≤ 0.005), respectively, over control. Additionally, following herbicide exposure, bacterial counts (log10 CFU mL−1) were reduced. Higher concentrations of ATZ and BCR completely reduced the growth patten of strain PSB-6. The current investigation provides an insight into a mechanistic approach of chemical herbicide-induced hazard toward a beneficial soil isolate. Careful monitoring is therefore necessary before agricultural application of pesticides.

Atrazine contaminated sites and bullfrog tadpoles: evasive trends and biochemical consequences.

Atrazine (ATZ) is one of the most used active principles in agricultural systems. This pesticide has the ability to easily accumulate in terrestrial and aquatic environments, causing impacts with chronic adverse effects. Avoidance tests are tests that seek to assess the concentration from which a given organism escapes, that is, migrates to another habitat. They are being used as a modality of innovative and minimally invasive ecotoxicological tests. Our objective was to evaluate the sensitivity and possible toxic effects of ATZ in bullfrog tadpoles (Lithobates catesbeianus), through avoidance tests and oxidative stress analyses. We performed the behavioral avoidance test lasting 12 h, with observations every 60 min in a linear multi-compartment system with seven compartments. Each compartment corresponded to a concentration: negative control, 1, 2, 20, 200, 2000, 20,000 µg L-1. After the selection of habitat, organisms were forcedly maintained in the chosen concentrations for 48 h and then, metabolic effects were measured assessing the blood plasma amino acid profile and liver protein degradation. We also determined the effective concentrations of ATZ tested at 0 h and 48 h. The results showed that there was an effect of the treatment on the distribution of tadpoles, but not on the hours or on the combined effect (interaction). The biochemical analyses also showed a concentration-dependent relationship which caused significant toxic effects even in a short period of time. In conclusion, these frogs were able to avoid places with high concentrations of ATZ in the first hours of exposure, which suggests that in the natural environment these animals can migrate or avoid areas contaminated by this herbicide; however, depending on the selected concentration, serious biochemical consequences can occur.

Mature Wistar Rats' Spleen and Liver Histomorphological Changes Related to the Duration of Atrazine Exposure

Background: Spleen and liver is secondary lymphoid organ that is highly sensitive to different chemicals. Widespread use of pesticides in agriculture has always been a matter of concern. And surprisingly, atrazine distinguishes out for being used more frequently among numerous harmful pesticides. As a result, long term exposure to atrazine and other pesticides is thought to produce metabolic abnormalities; however, little is known about how atrazine affects the spleen and liver and how this relates to its histo-achitectural structure.
 Aim: The histopathology of the spleen and liver from rats exposed to atrazine was the subject of our investigation.
 Materials and Methods: Twenty male wistar rats ranging from 150-200g were acclimated to laboratory conditions for 14 days, following which they were randomly assigned into 4 groups 1, 2, 3 and 4 of 5 animals each based on average body weight. Groups (2-4) were administered atrazine via oral route corresponding to 1237 mg/kg (20/5 LD50), 618 mg/kg (10/5 LD50) and 309 mg/Kg/body weight (1/10 LD50) for 7, 14 and 30 days, while group I (control) received distilled water orally using orogastric canula for 30 days . The liver and spleen from each group of rats were harvested, weighed, and fixed in 10% buffered formal saline fixative before being taken for histological examination 24 hours following the experimental periods of oral administration of the extract.
 Results: At the end of the experiment, the histological findings showed increased and numerous area of the white pulp of spleen from rats exposed to atrazine as compared to that from the control. The relative area of germinal centre in the structure of the splenic lymph follicles of rats exposed to atrazine also revealed increased. Also, Histo-pathologically, the liver showed necrotic hepatic cells and congested central vein, with the highest atrazine concentration causing the most adverse effects.
 Conclusion: Our data demonstrated that rats exposed to high-dose of atrazine led to hypertrophy of white pulp of the spleen and hepatic cell damage with liver. From this we concluded that both organ are highly sensitive to the debilitating effects of atrazine.

Heterocyclic agrochemical hosted by cyclodextrin and hybrid cyclodextrin-silica materials: Characterization, release behavior, and mobility in soil

Atrazine (ATZ) formulations are used to control a broad spectrum of weeds. The combination of ATZ with macromolecular systems, such as cyclodextrins (CDs), can improve its usefulness and herbicide efficacy related to the controlled release of the active ingredient. In this study, inclusion complexes of ATZ in CD and hybrid cyclodextrin-silica materials (CDSI) were prepared and characterized. Infrared spectral analysis of the inclusion compounds, concomitant with the suppression of the endothermic differential scanning calorimetry (DSC) peaks related to the fusion temperature of ATZ, confirmed the inclusion of ATZ in the functionalized and nonfunctionalized oligosaccharides. The linear increase in ATZ solubilization with the increasing addition of CD indicated that the inclusion stoichiometry was 1:1 in all studied systems. The increase in solubilization of the herbicide was approximately 1.3 times for α-CD and γ-CD, which had association constants of 20.3 and 13.4 L mol−1, respectively. The increase in solubility for α-CDSI and γ-CDSI was 3.3 and 2.7-fold, and the association constants were 161.1 and 111.1 L mol−1, respectively. Molecular mechanics (MM) calculations were performed using the force fields MM3* and AMBER*, and the results indicated that the most stable conformations resulted from the penetration of ATZ through the narrower cavity of the CDs. The MD calculations indicated three possible orientations for ATZ in the α-CD cavity, while for γ-CD the amplitude of the standard deviation of the energy values made it impossible to select a more favorable orientation. The ATZ release profile was affected by complexation. Over 22 h, more than 50% of noncomplexed ATZ was released, while for the complexes, less than 20% was released. The complexation, as well as the commercial formulation, provided variations in the development of Brassica juncea seedlings for the layers with higher concentrations of ATZ, thus agreeing with soil layer mobility studies indicated that complexation did not increase the leaching capacity of ATZ, which was mainly distributed in the upper soil layers, where it may be more available for herbicide control functions.

Toxicity comparison of atrazine on Eisenia fetida in artificial soil and three natural soils

Atrazine has been widely used in the world and caused environmental pollution, especially soil pollution. When assessing the toxicity of atrazine in soil, most studies used standardized artificial soils, while few studies focused on the real soil environments. In the present study, three natural soils and artificial soil were selected as test soils to study and compare the toxicities of atrazine to Eisenia fetida. Acute toxicity of atrazine was determined by filter paper and soil tests. In chronic toxicity study, after atrazine exposure, the content of reactive oxygen species in Eisenia fetida significantly increased and showed a dose-response relationship. The activity changes of three antioxidant enzymes and glutathione transferase showed that atrazine had obvious oxidative stress effect on earthworms. The contents of malondialdehyde and 8-hydroxy deoxyguanosine in 0.1 and 1 mg/kg atrazine treatment groups were significantly higher than the control, indicating that medium and high concentrations of atrazine could cause lipid and DNA damage in Eisenia fetida. The acute toxicity results and the integrated biomarker response index for chronic toxicity indicated that the toxicity order of atrazine was: red clay > fluvo-aquic soil > artificial soil > black soil, and that the toxicity of atrazine in artificial soil was not representative of its toxicity in real soil environment. The results of correlation analysis showed that three soil property parameters of organic carbon, organic matter and sand were most related to the toxicity of atrazine.

The stress effect of atrazine on the inducible defense traits of Daphnia pulex in response to fish predation risk: Evidences from morphology, life history traits, and expression of the defense-related genes

Herbicide pollution is persistent, which not only has a negative impact on individual organisms, but also may endanger the interspecific relationship between predators and prey. Cladocerans, i.e. zooplankton that plays an important role in the energy flow and material circulation in freshwater ecosystem, usually develop induced defense in response to predation risk. We used atrazine, one of the most used herbicides in the world, and Daphnia pulex, a representative cladocerans, to test the possible interference effect of herbicides on the induced defensive traits of cladocerans in response to predator fish (Rhodeus ocellatus) kairomone, including morphological defense, life history strategies, and the expression of defense-related genes. Atrazine reduced the body size, spine size, growth rate, total offspring, and the relative reproductive output of D. pulex, which further affected the response strength of the morphological and life history defenses, i.e., atrazine significantly reduced the spine size, relative spine size, and fecundity of D. pulex in response to R. ocellatus kairomone. Exposure to atrazine affected the expression of defense-related genes, and we speculated that atrazine affected the signaling process in the induced anti-predation defense of cladocerans. Specially, fish kairomone attenuated the negative effects of high concentrations of atrazine on the life history traits of D. pulex. Our results will help to accurately assess the potential risk of artificial compounds in freshwater ecosystems from the perspective of interspecific relationships, and help to understand the impact of environmental changes on the inducible anti-predator defense of prey in aquatic ecosystems.

Thermal and Biological Degradation of Herbicides to Treat Wastewater and Soil Pollution

Since their discovery in 1958, atrazine and other members of s-triazine family have been extensively applied in order to control grassy and broadleaf weeds in crops. Although, it was proved by many researchers that atrazine was slow and partially degradable material. These pesticides were widely used to enhance crop quality and yield. Atrazine degradation can be achieved by the effects of air, sun, water, microorganisms and temperature. Thermal degradation plays an important role in agrochemicals elimination; so a better understanding of the role of thermal degradation of atrazine is essential. Quantitative determination of pesticide residues was studied by calculating the amount of herbicide residues left after decomposition using a simple thermo analytical technique (TG, DSC). In this study, we found that all samples undergo the process of melting, evaporation, decomposition and oxidation at a temperature higher than the maximum registered climate temperature which made us conclude that 80–90%wt) of the pesticides stay in the environment without change under 100 °C on different parts of plants like fruits, leaves, and some penetrate into the ground to reach the roots or continue to the groundwater causes toxic problems to their consumers and environmental pollution. This result gave the motivation to find a more effective approach to reduce the harmful effect of these pollutants. In this regard, biological degradation of atrazine by using two legumes roots rhizobium bacteria was investigated. It is found that both rhizobium are able to treat atrazine at moderate temperature (30 °C). In comparison to chickpea rhizobia, bean rhizobia showed a higher performance with a removal efficiency of 43.21% and 57.42% at mild and high atrazine concentrations (5 mg/L and 10 mg/L) respectively. The results from this research offer an elegant way to remove the harmful effect of herbicides through degradation and to bring the safe use of herbicides a step closer to applications.

Effects of Anthropic Pollutants Identified in Pampas Lakes on the Development and Reproduction of Pejerrey Fish Odontesthes bonariensis

Anthropic activities can seriously affect the health of the organisms inhabiting them, and the observation of any alteration in the reproduction of fish could be associated with the presence of endocrine disruptors. In this manuscript we have collected information on the adverse effects of pollutants (heavy metals, environmental steroids, and agrochemicals), present in Chascomús lake, Argentina, either at environmentally relevant and pharmacological concentrations on reproduction, embryonic development, and larval survival of pejerrey fish Odontesthes bonariensis. During development, it has been reported that 17β-estradiol (E2) feminized and reduced larval survival, while 17α-ethinyl-estradiol (EE2) not only feminized but also affected both embryo and larval survival. In adult male fish, treatments with EE2 and E2 + EE2 were able to increase mRNA abundance of gnrh3 and cyp19a1b and decreased those of gonadotropin receptors (fshr and lhcgr). Heavy metals such as cadmium, chromium, and copper negatively affected sperm quality, diminishing the motility. Also, a decrease in the percentage of hatching rate and larval survival was also observed with the same metals, highlighting zinc as the most detrimental metal. Furthermore, all these metals altered the expression of hypothalamic and pituitary genes related to reproduction in male pejerrey (gnrh1,2,3; cyp19a1b; fshb; lhb; fshr and, lhcgr). Moreover, in all cases pyknotic cells, corresponding to the degeneration of the germ cells, were observed in the testes of exposed fish. For agrochemicals, exposure of male pejerrey to environmental concentrations of glyphosate did not cause alterations on the endocrine reproductive axis. However, male pejerrey with gonadal abnormalities such as the presence of intersex (testis-ova) gonads were found in other Pampa´s lakes with high concentrations of atrazine and glyphosate associated with soybean and corn crops near their coasts. These types of studies demonstrate that pejerrey, an endemic species with economic importance inhabiting the Pampas shallow lakes, can be used as a sentinel species. It should be noted that increased pollution of aquatic ecosystems and the effects on the reproduction of organisms can lead to a decline in fish populations worldwide. Which, added to overfishing and other external factors such as global warming, could cause an eventual extinction of an emblematic species.

Exploring the effect of atrazine exposure on the reproductive capacity of Daphnia magna

Atrazine is an herbicide commonly used for weed control in crops and on turf, but environmental contamination with atrazine causes endocrine disruption leading to reproductive defects in humans and freshwater organisms. The molecular and cellular mechanisms causing these reproductive deficiencies remain largely unknown. Thus, the purpose of this study is to explore the reproductive consequence of atrazine exposure at the molecular and cellular level in the freshwater planktonic crustacean, Daphnia magna. Results show that exposure of D. magna to high atrazine concentration of 1000 or 2000 μg/L reduced the number of the first set of offspring born at least 5 days after atrazine exposure. D. magna exposed to these atrazine concentrations exhibited DNA fragmentation, nuclear condensation and fragmentation in the ovaries, and caspase-3 protein activation in both the ovaries and embryos in the brood chamber. No obvious DNA fragmentation, nuclear condensation and fragmentation, or caspase-3 activation was seen in other tissues. These findings suggest that high environmental concentrations of atrazine specifically induce apoptosis in reproductive tissues, which could account for the decline in the number of offspring in D. magna exposed to high concentrations of atrazine.

Health risk assessment of exposure to atrazine in the soil of Shiraz farmlands, Iran.

Atrazine-contaminated soils can pose a carcinogenic and non-carcinogenic health risk through different routes for exposed people. This study aimed to assess the health risk of exposure to atrazine-contaminated soils through direct ingestion and dermal contact in farmlands nearby Shiraz. Atrazine concentration was measured in 22 selected sites using grid sampling. The carcinogenic and non-cancer risks associated with dermal and ingestion exposure in children and adults were estimated. The lowest and highest atrazine concentrations were in S1 (0.015mg/kg soil) and S22 (0.55mg/kg soil). Hazard Index (HI)1 values ranged from 0.007 to 0.25 for children, and the values ranged from 0.0008 to 0.03 for adults. The mean cancer risk for children and adults was 6.01×10-4 and 7.40×10-5, respectively. The HI value was less than 1 for all sampling sites, indicating that exposure to atrazine does not threaten children and adults. However, the cancer risk exceeds the United States Environmental Protection Agency (US.EPA)2 threshold risk limit (10-6 to 10-4) in all sampling sites. Therefore, it is recommended that children should avoid playing on atrazine-contaminated farms or soils near anywhere atrazine may have been used.

Association between Aqueous Atrazine and Pediatric Cancer in Nebraska

Agrichemicals, chemicals used to maximize crop and animal production, can lead to water quality concerns when these chemicals run off into surface and groundwater after precipitation events. In Nebraska, one such chemical is atrazine, a suspected carcinogen. This study evaluated the association between atrazine in surface and groundwater, in relation to the incidence of pediatric cancer in Nebraska watersheds over 30 years (1 January 1987 to 31 December 2016). The watersheds were grouped into four categories based on the average atrazine concentration over the study period, using quantile classification. The associations between atrazine (ground/surface) and pediatric cancer after adjusting for social vulnerability index (SVI) variables, using pediatric population as offset, were compared using a generalized linear model (GLM) assuming a negative binomial distribution. The results from the GLM approach suggested positive associations between watersheds with higher atrazine concentration and a higher pediatric cancer incidence rate ratio. In this study, the associations were evaluated using atrazine measurements obtained from non-drinking water sources as a proxy measure. Further research is necessary to establish the causal relationship between atrazine and pediatric cancer.

Exposure to Atrazine Impairs Behaviour and Growth Performance in African Catfish, Clarias gariepinus (Burchell, 1822) Juveniles

Clarias gariepinus juveniles of average weight, 17.57±1.95 g and an average length of 14.26±0.39 cm were exposed to environmentally relevant concentrations of 0 (control), 2.5, 25, 250, and 500 µg L-1 atrazine in a quality-controlled 28-day bioassay. Growth performance was assessed bi-weekly and fish samples were taken from different tanks to determine the relative growth rate, specific growth rate, feed conversion ratio, condition factor and behaviour. At the end of two weeks of exposure, the relative growth rate and the specific growth rate among exposed fish groups was found to reduce significantly (p<0.05) compared to the control, an indication of poor growth performance. The average specific growth rates (SGR) of control fish is 3.86±0.02 %/w at the end of the exposure duration while recording -0.64±0.09 in the 500 µg L-1 group. Feed conversion ratio increased significantly from control to the group with highest atrazine concentration. Condition factor (K) of fish among treatment groups showed significant decrease in values with increasing concentration of atrazine in a dose-dependent pattern. Atrazine exposure resulted in behavioural anomalies including erratic swimming, clinging to the water surface, loss of equilibrium, lethargy, and discolouration. The behavioural responses were found to be concentration-dependent. The length-weight relationships for both control and atrazine exposed fish exhibited positive allometric growth and significant relationships as depicted by the value of R2 (coefficient of determination) except in the fish group exposed to 500 µg L-1 atrazine which exhibited negative allometric growth. Findings from this study indicate interference with normal behaviour and growth performance of C. gariepinus juveniles with ecological implications in water bodies exposed to atrazine even at reduced concentrations.

Changes induced by atrazine in Clarias gariepinus provide insight into alterations in ovarian histoarchitecture and direct effects on oogenesis

Clarias gariepinus juveniles were exposed to environmentally relevant concentrations of 0 (control), 2.5, 25, 250 and 500 μg L−1 atrazine in a quality-controlled 28-day laboratory procedure. Findings revealed a significant decrease in the levels of follicle-stimulating hormone, luteinizing hormone and prolactin relative to control (p < 0.05). Atrazine reduced the levels of testosterone while increasing the concentration of progesterone. Histologically, the control and treatments presented three stages of oocyte maturation: the chromatin nucleolar oocyte stage, early perinucleolar oocyte stage and the vitellogenic oocyte stage. However, in the ovaries of the treatment group with the lowest treatment concentration (2.5 μg L−1), atretic oocytes with broken membranes invaded many of the dead ova and empty spaces. In other treatments (25, 250 and 500 μg L−1), interfollicular spaces, vacuolation in oocyte formation, and dissolution of oocyte walls were observed. Disruption of the yolk vesicle and clumping of the cytoplasm in maturing oocytes was observed only at the highest atrazine concentration (500 μg L−1). Gross alterations in ovarian histoarchitecture and reproductive hormone levels observed in this study showed interference with oogenesis which may result in reduced egg viability and fecundity in fish with ecological implications in water bodies exposed to atrazine even at reduced concentrations.

Thirty-year monitoring of s-triazine herbicide contamination in the aquifer north of Vicenza (north-east Italy)

The aquifer north of Vicenza, Italy, is one of the main and most studied drinking water reservoirs within the Veneto region. The area is an intensive cropland, and monitoring of s-triazine herbicides and metabolites has been carried out since the late eighties. This study analysed the trends of atrazine (ATR), terbuthylazine (TBZ), deethyl-atrazine (DEA), and deethyl-terbuthylazine (DET) concentrations from 1987 to 2016 and related the variations of agricultural land use, herbicide load, and pesticide regulations to the residence time of pollutants in the aquifer. In total, 785 water samples collected from 82 selected check wells were analysed with high-resolution gas chromatography combined with mass spectrometry. Non-detects were substituted by one-half the limit of detection. Over the 30 years of monitoring, concentrations of all of the pollutants decreased at all sampling sites. Since the beginning, TBZ and DET residues have been systematically lower than ATR and DEA, respectively, with more than 70% of the data below the limit of detection and never exceeding the European Maximum Acceptable Concentration (MAC) for a single pesticide (0.1 μg/L). The highest concentrations of ATR and DEA showed a spatial shift along the flow direction, suggesting an increase in groundwater residence time from the recharge zone to the accumulation zone of the aquifer. The last residues of ATR were found 27 years after its ban.Although all of the concentrations were lower than those found elsewhere in Europe, the sum of s-triazines overcame the MAC in 20% of the samples. Considering the structural and toxicological similarities of s-triazines, these findings confirm the necessity of better characterisation of the toxicological risk posed by mixtures.

Mobility studies of atrazine in the soil-plant system in two cameroonian vegetables Amaranthus hybridus and Corchorus olitorius

Abstract The objective of this work is to assess the level of contamination of the soil-plant system by atrazine which is a pesticide classified as dangerous in the European Union, but approved in Cameroon. To achieve this aim, two plant species (Amaranthus hybridus and Corchorus olitorius) were grown in pots according to the method developed by farmers in the field. In other words, each pot was treated with three dosages of atrazine (22.5 ​g/L; 45 ​g/L and 90 ​g/L). Later, the crops were harvested at four stages of growth and the atrazine was analysed in the soil and in the plants by HPLC-UV. The results show that the concentration of atrazine decreased from 4.66 ​mg/L in the soil after 15 days of growth of the plant to 1.96 ​mg/L after 2 months of growth. This evolution is also observed within the two plant species with a significant treatment effect. Thus, the highest concentrations of atrazine were found in the roots of plants harvested from soils treated with 90 ​g/L of atrazine. Besides, the maximum average content of atrazine of 0.74 ​mg/kg of dry matter was found in the edible part of the two plant species at their stage of maturity. Finally, atrazine is persistent in the agricultural soil after two months regardless of the dose. Given the amount of atrazine translocated into the edible leaves, this herbicide should not be used for the cultivation of the two vegetables studied, contrary to what is practiced in the field in Ngaoundere (Cameroon).

Effects of atrazine on the black community land function and role of microbial ecology

By measuring the concentration of atrazine stress and different culture days, the abundance of key genes in soil nitrogen transformation was studied by means of real-time PCR with the increase of atrazine stress time. The abundance of soil nitrogen-fixing function gene (nif-H) increased significantly with the increase of time in the middle and late culture period (15-30 d), indicating that the abundance of soil nitrogen-fixing function gene was promoted; soil ammonia oxidation. The abundance of functional gene (amo A) was reduced at the low concentration of atrazine (0 mg/kg, 20 mg/kg), and then decreased with increasing stress time, while at high concentration of atrazine. Under the treatment of (100mg/kg), with the increase of time, the abundance of soil ammonia oxidation function increased first and then decreased, indicating that the abundance of soil ammonia oxidation function gene was affected in the process of culture. II Based on high-throughput sequencing technology, the results of soil nitrogen fixation and ammonia oxidation community diversity showed that the functional gene diversity of soil samples was affected by the concentration of atrazine and stress time. According to the analysis of soil diversity index, nitrogen-fixing functional genes of soil samples treated with atrazine at 0 mg/kg, 20 mg/kg and 100 mg/kg were tested at the late stage (30 d). The diversity index of (nif-H) was higher than the mid-test (15 d). At the beginning of the experiment (0 d), the ammonia functional gene (amo A) diversity index of soil samples treated with atrazine concentrations of 0 mg/kg, 20 mg/kg and 100 mg/kg was higher than that in the middle of the experiment (15d), studies have shown that the nitrogen and ammonia oxidation functional gene diversity is affected under different concentrations of atrazine stress time. The distribution of the nitrogen-fixing gene (nif-H) and the ammonia-oxidizing functional gene (amo A) in the horizontal sample community structure showed that the nitrogen-fixing gene was in the middle of culture (15 d), and the genus Burkholderia and Rhizobium were earlier than the culture period (0d) indicating that the above two types of nitrogen-fixing microorganisms play a leading role at this stage. Throughout the experiment (0-30 d), the number of nitrogen-fixing functional genes in the blank treatment was higher than 20 mg/kg and 200 mg/kg. The principal component analysis confirmed that the different culture days and different stress concentrations of atrazine had certain effects on the composition of soil nif-H and amo A gene communities.

Development and removal ability of non-toxigenic Aspergillus section Flavi in presence of atrazine, chlorpyrifos and endosulfan

This study evaluated the in vitro effect of three concentrations of atrazine, chlorpyrifos and endosulfan on the growth parameters of four non-toxigenic Aspergillus section Flavi strains. The ability of the strains to remove these pesticides in a synthetic medium was also determined. Growth parameters were measured on soil extract solid medium supplied with 5, 10 and 20mg/l of each pesticide, and conditioned to −0.70, −2.78, −7.06 and −10.0 water potential (MPa). Removal assays were performed in Czapek Doc medium (CZD) supplied with 20mg/l of each pesticide under optimal environmental conditions (−2.78 of MPa and 25°C). The residual levels of each pesticide were detected by the reversed-phase HPLC/fluorescence detection system. The lag phases of the strains significantly decreased in the presence of the pesticides with respect to the control media. This result indicates a fast adaptation to the conditions assayed. Similarly, the mycelial growth rates in the different treatments increased depending on pesticide concentrations. Aspergillus oryzae AM 1 and AM 2 strains showed high percentages of atrazine degradation (above 90%), followed by endosulfan (56 and 76%) and chlorpyrifos (50 and 73%) after 30 days of incubation. A significant (p<0.001) correlation (r=0.974) between removal percentages and growth rate was found. This study shows that non-toxigenic Aspergillus section Flavi strains from agricultural soils are able to effectively grow in the presence of high concentrations of atrazine, chlorpyrifos and endosulfan under a wide range of MPa conditions. Moreover, these strains have the ability to remove high levels of these pesticides in vitro in a short time.

Characterisation of an efficient atrazine-degrading bacterium, Arthrobacter sp. ZXY-2: an attempt to lay the foundation for potential bioaugmentation applications

BackgroundThe isolation of atrazine-degrading microorganisms with specific characteristics is fundamental for bioaugmenting the treatment of wastewater containing atrazine. However, studies describing the specific features of such microorganisms are limited, and further investigation is needed to improve our understanding of bioaugmentation.Results and conclusionsIn this study, strain Arthrobacter sp. ZXY-2, which displayed a strong capacity to degrade atrazine, was isolated and shown to be a potential candidate for bioaugmentation. The factors associated with the biodegrading capacity of strain ZXY-2 were investigated, and how these factors likely govern the metabolic characteristics that control bioaugmentation functionality was determined. The growth pattern of Arthrobacter sp. ZXY-2 followed the Haldane–Andrews model with an inhibition constant (Ki) of 52.76 mg L−1, indicating the possible augmentation of wastewater treatment with relatively high atrazine concentrations (> 50 ppm). Real-time quantitative PCR (RT-qPCR) results showed a positive correlation between the atrazine degradation rate and the expression levels of three functional genes (trzN, atzB, and atzC), which helped elucidate the role of strain ZXY-2 in bioaugmentation. In addition, multiple copies of the atzB gene were putatively identified, explaining the higher expression levels of this gene than those of the other functional genes. Multiple copies of the atzB gene may represent a compensatory mechanism that ensures the biodegradation of atrazine, a feature that should be exploited in future bioaugmentation applications.