Atrazine behaviour in the different pedological horizons of two Argentinean non-till soil profiles

Atrazine behaviour was investigated in the different pedological horizons from profiles of two non-tilled soils, a Typic Argiustoll and an Entic Haplustoll from the Argentinean pampas. As atrazine use in field conditions was associated with maize cropping, only one type of soil received atrazine every other year. Atrazine behaviour was characterized through the balance of ¹⁴C-U-ring atrazine radioactivity among the mineralized fraction, the extractable fraction and the non-extractable bound residues. The composition of the extractable fraction was characterized. Atrazine mineralization was the main dissipation mechanism in the superficial horizon of the Argiustoll because of microbial adaptation after repeated atrazine applications. In contrast, little atrazine mineralization was found in the Haplustoll profile, and it decreased with depth. The capacity of the soil organic matter to form bound residues was characterized using soil-size fractionation. Atrazine-bound residues depended on the soil organic matter content and the size of the fraction. Organic matter in the largest size fractions had a higher capacity to form atrazine-bound residues. In the Argiustoll profile, the atrazine degradation capacity decreased in the subsurface horizons (Bt₁ and Bt₂), where a large part of bound residues were formed. The deepest horizon (BC) of this profile had a high capacity to degrade atrazine reaching this horizon after a lag period. In the Haplustoll profile, atrazine mineralization and bound residue formation followed the organic carbon mineralization pattern.     

Aminopyrifen,a novel 2-aminonicotinate fungicide with a unique effect and broad-spectrum activity against plant pathogenic fungi

Aminopyrifen is a novel 2-aminonicotinate fungicide with unique chemistry and a novel mode of action. The fungicide showed high antifungal activity mainly against Ascomycetes and its related anamorphic fungi under in vitro and pot conditions (EC₅₀ values: 0.0039–0.23 mg/L and 1.2–12 mg/L, respectively). The active ingredient strongly inhibited germ-tube elongation of Botrytis cinerea below 0.1 mg/L and invasion into a plant. The compound exhibited no cross-resistance to commercial fungicides in B. cinerea. The antifungal agent showed high preventive efficacy and translaminar action. In the field, aminopyrifen controlled gray mold and powdery mildew at 150 mg/L. Our findings suggest that aminopyrifen is useful for protecting crops from various plant pathogens.     

Organochlorine pesticide residue in Chinese herbal medicine

Over ten-year routine inspection results on organochlorine pesticide (OCP) residue were summarized, OCPs residues, including BHC isomers (α, β, γ, and δ-BHC), DDT analogs (p,p′-DDD, p,p′-DDE, o,p′-DDT, and p,p′-DDT), and pentachloronitrobenzene (PCNB) and its metabolites (pentachloroaniline and methyl pentachlorophenyl sulfide (MPCPS)), in 1,665 samples for 37 types of Chinese herbal medicine (CHM) using the QuEChERS method coupled with the GC-ECD. Based on the maximal residue levels for OCPs set by Asian pharmacopeias, PCNB contamination in Ginseng radix as well as the total DDT and PCNB contamination in Panacis quinquefolii radix are of concern. OCP residues in different parts of Panax ginseng were also compared. The total BHC residue in leaf and fibrous root, as well as the total DDT and PCNB residue in all parts, exceeded MRL of 0.1 mg/kg. Overall, this study provided meaningful results about OCP residue in CHM for pharmaceutical industries and consumers.     

Effect of heat-treating soil and straw on the subsequent adsorption of chlortoluron and atrazine

The adsorption of chlortoluron and atrazine was measured on a range wheat straw residues that had been heated for periods of 1–5 min at temperatures up to 700°C and and on three soils that had been heated at up to 250°C for 1–5 min. Adsorption of both compounds by straw ash increased with increasing temperature of pretreatment. Atrazine adsorption by any of the soils was not changed markedly chlortoluron absorption was increased with two of the three soils. The results are discussed in terms of the changes in organic functional groups, that are likely to have been produced by the treatment, in relation to the adsorption mechanisms thatmay operate on the two compounds. Adsorption of chlortoluron by mixtures of ash and soil was less than the sum of the adsorption capacities of each component on its own in the cases of two out of three soils. It is concluded that the effect of straw burning on herbicide performance in the field will be variable but could be substantial. Le chauffage du sol et du chaume: influence sur l’adsorption ultérieure de chlortoluron et de l'atrazine     

Synergistic and antagonistic effects of atrazine on the toxicity of organophosphorodithioate and organophosphorothioate insecticides to Chironomus tentans (Diptera: Chironomidae)

The acute toxicities of two organophosphorodithioate (dimethoate and disulfoton) and two organophosphorothioate (omethoate and demeton-S-methyl) insecticides were evaluated individually and in binary combination with the herbicide atrazine using fourth-instar larvae of the aquatic midge, Chironomus tentans. Atrazine alone up to 1000 μg/L did not show significant toxicity to the midges in a 48-h bioassay. However, atrazine concentrations as low as 1 μg/L in combination with dimethoate at EC₂₅ (concentration to affect 25% of tested midges), 100 μg/L in combination with disulfoton (EC₂₅), and 10 μg/L in combination with demeton-S-methyl (EC₂₅) significantly enhanced the toxicity of each organophosphate insecticide. In contrast, atrazine concentrations of 10 μg/L and above in combination with omethoate (EC₂₅) significantly decreased the toxicity of the insecticide. Biochemical analysis indicated that increased toxicity of dimethoate, disulfoton, and demeton-S-methyl in binary combination with atrazine correlated to the increased inhibition of acetylcholinesterase. Furthermore, cytochrome P450-dependent O-deethylation activity in the midges exposed to atrazine at 1000 μg/L was 1.5-fold higher than that in the control midges. Thus, atrazine appeared to induce cytochrome P450 monooxygenases in the midges. Elevated cytochrome P450 monooxygenase activity may increase the toxicities of dimethoate, disulfoton, and demeton-S-methyl by enhancing the oxidative activation of dimethoate into omethoate, and disulfoton and demeton-S-methyl into their sulfoxide analogs with increased anticholinesterase activity. In contrast, atrazine reduced the toxicity of omethoate possibly by enhancing the oxidative metabolic detoxification since omethoate does not require oxidative activation.     

羧甲基壳聚糖/改性膨润土复合载体对莠去津释放和淋溶的影响

首次尝试将羧甲基壳聚糖与改性膨润土复合用作除草剂莠去津的载体,制备得到控释型颗粒剂,以延缓莠去津的释放,减少淋溶损失,提高药效及控制其污染。通过水中释放实验研究了制剂配方对莠去津释放速率的影响,并借助半经验方程探讨了其释放机理,采用土壤薄层实验考察了复合载体对降低莠去津淋溶的效果。 结果表明,采用复合载体时莠去津的半数释放时间(t 50)可达700 h 以上,比对照采用单一羧甲基壳聚糖作载体时延长了1倍以上。莠去津由颗粒剂向水相释放的过程主要受费克扩散(Fickian diffusion)控制,且经9次淋洗后莠去津的累计淋出率仅为6.0%,表明该复合载体控释制剂可显著减少莠去津对地下水的污染。     

Differential atrazine interference with the Hill reaction of isolated chloroplasts from Chenopodium album L. biotypes

Atrazine [2-chloro-4-(ethylaminol-6-(isopropyl-amino)-s-triazine] resistant biotypes of lamb's quarters (Chenopodium athum L) were reported in the maize growing areas of Ontario, where the herbicide had been used fur a number of years. Field samples from four locations proved tolerant to higber than recommended rates of atrazine in controlled environment screening trials. A resistant biotype was not killed with up to 40 kg/ha atrazine. Diuron at 5 x10-5 M inhibited the Hill reaction with isolated chloroplasts of resisiant and susceptible biotypes of lamb's-quarters. However, with 10-4 M atrazine, the photochemical activity was inhibited in chloroplasts isolated from the susceptible biotype but not in chloroplasts from the resisiant biotype. With maize chloroplasts, inhibition with 10-4 M atrazine was the same as with the susceptible biotype of lamb's-quarters. These studies suggested that a new mechanism of intraspecific resistance in lamb's quarters to atrazine was involved, other than differences in uptake, translocation and metabolism reported with interspecific comparisons involving the s-triazines and other herbicides, It was also concluded that atrazine and diuron did not have precisely the same mechanism of action as photosynthetic inhibitors with lamb's-quarters, and that external and or internal structure or function of chloroplasts in relation to atrazine inhibition can vary significantly even in biotypes of the same species.     

The degradation of residual pesticides and the quality of white clover silage are related to the types and initial concentrations of pesticides

In order to understand the degradation of different residual pesticides of white clover silage and their influence on silage quality, three commonly used orchard pesticides with different concentrations were added to the white clover and fermented for 90 days. The results showed that the degradation rate of cypermethrin and its toxic degradation product 3-phenoxybenzoic acid (3-PBA) was the highest after silage, at different concentrations, both were 100%. The degradation rate of Tebuconazole and chloropyridine was 72.47–80.27% and 47.76–64.82%, of which 3,5,6-trichloro-2-pyridinol (TCP) content, poisonous toxic degradation product, increased 0.0525–0.253 mg·kg⁻¹. The residues of beta-cypermethrin and tebuconazole had reached safety standards after silage. As compared with the control, the contents of lactic acid, acetic acid, and propionic acid increased in the treated samples. The higher concentrations of three pesticides all significantly reduced the lactic acid content of silage (p<0.05). Pesticides had different effects on the nutritional components of white clover silage. Conclusively, silage is a potential way to expand the utilization of covering plants in orchards.     

三嗪类除草剂莠去津的研究进展

三嗪除草剂莠去津是在世界范围内广泛应用的一种除草剂,其对人类健康、农业生产及生态环境的影响具有全球性,已经引起广泛关注。本文介绍了莠去津的性质、危害、迁移分布、分析检测及相关的法规。     

Establishing a ready biodegradability test system using OxiTop® to evaluate chemical fate in a realistic environment

The purpose of this study is to propose the use of OxiTop® for measuring biochemical oxygen demand (BOD) under the Japanese Chemical Substances Control Law in order to properly evaluate chemical fate in a real environment. In our previous study, the biodegradation of test chemicals was accelerated by both adsorbing the chemical to silica gel with chloroform and increasing the medium volume from 300 to 3900 mL in the OECD 301F test using a coulometer. However, the biodegradability of these chemicals could not be evaluated based on BOD due to chloroform residue in the silica gel, or the medium volume could not be increased further due to the oven size of the coulometer. In this study, we established an evaluation system using OxiTop® based on BOD by increasing the medium volume to 9000 mL. Based on triplicate testing, increasing the medium volume accelerated biodegradation and decreased variation in BOD.     

Influence of Atrazine and Roundup pesticides on biochemical and molecular aspects of Biomphalaria alexandrina snails

The excessive use of pesticides in agriculture has sparkled the interest of scientists in investigating the harmful effects of these compounds. The present study evaluates the pesticides Atrazine and Roundup (glyphosate) on biochemical and molecular aspects of Biomphalaria alexandrina snails. The results showed that LC₁₀ of these two pesticides caused considerable reduction in survival rates and egg production of treated snails. Additionally, Atrazine proved to be more toxic to B. alexandrina snails than Roundup. In treated snails, glucose concentration (GL) in the hemolymph as well as lactate (LT) and free amino acid (FAA) in soft tissues of treated snails increased while glycogen (GN), pyruvate (PV), total protein (TP), nucleic acids (DNA and RNA) levels in snail’s tissues decreased. The activities of glycogen phosphorylase (GP), superoxide dismutase (SOD), catalase (CAT) and glutathione reductase (GR), succinic dehydrogenase (SDH), acetylcholinesterase (AChE), lactic dehydrogenase (LDH) and phosphatases (ACP and ALP) enzymes in homogenate of snail’s tissues were reduced in response to the treatment with the two pesticides while lipid peroxide (LP) and transaminases (GOT and GPT) activity increased (P < 0.001). The changes in the number, position and intensity of DNA bands induced by pesticides may be attributed to the fact that pesticide can induce genotoxicity through DNA damage. It was concluded that the pollution of the aquatic environment by Atrazine and Roundup pesticides, would adversely affect the metabolism of the B. alexandrina snails, and have adverse effects on its reproduction.     

3种莠去津复配剂对玉米田杂草的防除效果

为降低莠去津对后茬作物的危害及环境的污染,选用3种莠去津复配制剂（20％烟嘧·莠去津可分散油悬浮剂、25％硝磺草酮·莠去津悬浮剂、50％硝磺草酮·莠去津·乙草胺悬乳剂）进行玉米田杂草防除效果研究,为田间合理选用除草剂提供依据。结果显示,3种复配剂对玉米地田间杂草群体防效均较好,药后45 d杂草群体株防效在84．00％以上、鲜质量防效在97．00％以上,25％硝磺草酮·莠去津悬浮剂对狗尾草防效较差,说明各复配剂能有效防除玉米地田间杂草且对玉米生长安全。     

Antidote action of humic substances on atrazine inhibition of sulfate uptake in barley roots

Atrazine 10^?4M rapidly inhibits sulfate uptake by excised barley roots. When humic substances are present in the uptake solution the inhibition is reduced. This effect is enhanced by 10 to 16 hr incubation of the roots in the presence of humus. Humus action is accompanied by the stimulation of leucine incorporation into protein, which, on the contrary, is unaffected by atrazine. The same experiments carried out with barley seedlings, in nutrient solution containing either atrazine or humus, or both, confirm the inhibitory action of atrazine on SO₄^2? absorption by the whole plant and the inhibition reduction by humic substances.     

Cellular and biochemical effects induced by atrazine on blood of male Japanese quail (Coturnix japonica)

Atrazine a potent endocrine disruptor herbicide is broadly used to control rapidly growing unwanted weeds in various cereals crops which induce adverse effects both in mammalian and avian species. In present study 96 mature male Japanese quail (Coturnix japonica) were procured and randomly kept in eight groups (A to H) each having 12 birds. Atrazine was administered orally at 0, 10, 25, 50, 100, 250 and 500 mg/kg body weight to all experimental groups. The mitomycin C at 2 mg/kg body weight was given to the birds of group B which served as a positive control. From each group 4 birds were randomly selected and harvested at day 15, 30 and 45. A significant (P < 0.05) decrease in serum total protein, serum albumin and serum testosterone values were recorded at day 45 in all treated groups. A significant increase in serum ALT and AST concentration was also recorded. Moreover, morphological alterations in nucleus of erythrocytes were also observed including blebbed nuclei, notched nuclei, lobed nuclei, vacuolated cells, binucleated cell, and cell with pear shaped and micronucleus. Overall, our results show that atrazine at higher doses induces significant serum biochemical alterations and changes in nucleus of erythrocytes.     

Atrazine soil metabolism in maize fields treated with organic fertilizers

The metabolism of atrazine in soil was studied in two maize fields located in regions with different soil types. Treatments were cow manure or pig slurry (50 tonnes each ha^-1) applied once either in March or in November before sowing, or green manure incorporated in March. Control plots were not treated with organic fertilizers. Atrazine at 0.75 or 1.0 kg a.i. ha^-1 was applied after sowing. In the 0-12 cm soil layer, the main atrazine metabolites found were deethylatrazine and hydroxyatrazine. Low concentrations of deisopropylatrazine and 6-chloro-1, 3, 5-triazine-2, 4-diamine were also observed. During the 4 months after sowing, the organic fertilizers decreased the rate of atrazine degradation, but subsequently there were no differences between treated and control plots. At harvest, the concentrations of atrazine and its metabolites were very low and similar in all plots. The organic fertilizers thus did not cause atrazine metabolites to accumulate in soil. In addition, atrazine and its metabolites were never detected below 12 cm in any of the plots.     

Human metabolism of atrazine

Atrazine (ATZ) metabolism by human liver microsomes (HLM), cytochrome P450 (CYP) isoforms, and human liver (HL) S9 fractions, was investigated using HPLC/PDA and LC/MS/MS. CYP-dependent metabolites from pooled HLM are desethylatrazine (DEA), desisopropylatrazine (DIA), 1-hydroxyisopropylatrazine (HIATZ), and 2-hydroxyethyl atrazine (HEATZ). DEA and DIA were major metabolites in pooled HLM. CYP1A2 and 2C19, respectively, were major isoforms for DEA and DIA production. CYP3A4, while less active, is generally at high concentrations, produces both DEA and DIA and is significant. The percent total normalized rates (%TNR) for CYP1A2 and 3A4 in pooled HLM were 63% and 24% for DEA, and 35% and 56% for DIA production. Single donor HLM samples, showed correlations for CYP1A2 (r = 0.92) and 3A4 (r = 0.81) for DEA and DIA production, while variations in production of DEA and DIA were 8.5- and 6.0-fold, respectively. Pooled S9 fractions also mediate glutathione conjugation of atrazine, DEA and DIA.     

Root exudation of prometryn and its metabolites from Chinese celery (Apium graveolens)

Root exudates from Chinese celery (Apium graveolens) and Chinese cabbage (pak choi, Brassica chinensis) plants treated by prometryn, an herbicide, were qualitatively and quantitatively investigated and compared under hydroponic cultivation. Prometryn and its metabolites released into the nutrient solution were analyzed by ultra-performance liquid chromatograph coupled with orbitrap mass spectrometer to investigate whether this xylem-mobile herbicide is exuded from the roots. The results showed that celery and pak choi had different root exudation profiles. Celery metabolized prometryn to prometryn sulfoxide and released both compounds from the roots. In contrast, pak choi barely metabolized or actively released prometryn from the roots. The concentration of prometryn sulfoxide released from celery after 96 hr was 21 µg/L, which was nearly one-third that of released prometryn. Our results indicate that the root exudation and translocation of xylem-mobile herbicides could be significant in plants and are highly species dependent compared with phloem-mobile herbicides.     

Mechanism of action and selectivity of a novel herbicide,fenquinotrione

Fenquinotrione is a novel herbicide that can control a wide range of broadleaf and sedge weeds with excellent rice selectivity. We revealed that fenquinotrione potently inhibited the 4-hydroxyphenylpyruvate dioxygenase (HPPD) activity in Arabidopsis thaliana with an IC₅₀ of 44.7 nM. The docking study suggested that the 1,3-diketone moiety of fenquinotrione formed a bidentate interaction with Fe(II) at the active site. Furthermore, π–π stacking interactions occurred between the oxoquinoxaline ring and the conserved Phe409 and Phe452 rings, indicating that fenquinotrione competes with the substrate, similar to existing HPPD inhibitors. A more than 16-fold difference in the herbicidal activity of fenquinotrione in rice and the sedge, Schoenoplectus juncoides, was observed. However, fenquinotrione showed high inhibitory activity against rice HPPD. Comparative metabolism study suggested that the potent demethylating metabolism followed by glucose conjugation in rice was responsible for the selectivity of fenquinotrione.     

An in vitro assay for the assessment of the effects of an organophosphate, paraoxon, and a triazine, atrazine, on the heart of the gilthead sea bream (Sparus aurata)

The effects of paraoxon and atrazine on the spontaneously beating auricle, isolated from the heart of Sparus aurata, were assessed. Paraoxon, 5 μM, eliminated the atria contraction within 28.4 ± 2.8 min, an effect which was fully reversed by 15 μM atropine, an antagonist of muscarinic cholinergic receptors. The IC₅₀ was estimated to be 3.2 ± 1.5 μΜ. Atrazine, 50 and 100 μM, induced a 22.5 ± 3.2 and 32.9 ± 2.3% increase in the force of auricle contraction, caused by excitation of sympathetic synaptic terminals releasing adrenaline. This effect was reversed by 50 μM propranolol, a blocker of β-adrenoreceptors. The results have shown that both sympathetic and parasympathetic nerve terminals are activated by atrazine. Also, the auricle contraction is mainly under sympathetic control, while the frequency is dominated by cholinergic system. Finally, the detailed parameters of the auricle contraction estimated during exposure to specific pesticides, force, frequency, time-response curves and electromechanical coupling can be further used to assess and compare the toxic effects of other compounds, anticholinesterases for example, on the heart of the fish.