Miscanthus,is a promising bioenergy crop,considered superior to other bioenergy crops because of its higher water and nutrient use efficiency,cold tolerance,and higher production of biomass.Broadleaf weeds and grass w...Miscanthus,is a promising bioenergy crop,considered superior to other bioenergy crops because of its higher water and nutrient use efficiency,cold tolerance,and higher production of biomass.Broadleaf weeds and grass weeds,cause major problems in the Miscanthus field.A field experiment was conducted in 2018 and 2019,to assess the effects of pre-emergence(alachlor and napropamide)and post-emergence herbicides(nicosulfuron,dicamba,bentazon,and glufosinate ammonium)on broadleaf and grass weeds in M.sinensis and M.sacchariflorus fields.The weed control efficiency and phytotoxicity of pre-and post-emergence herbicides were evaluated at 30 days after treatment(DAT)and compared to those of the control plots.The results showed wide variations in the susceptibility of the weed species to the treated herbicides.Treatment with nicosulfuron 40 g.a.i.ha^(-1) provided the most effective overall weed control(with 10%visual injury),without affecting the height and biomass of neither Miscanthus species in the field.Post-emergence herbicides such as glufosinate ammonium 400 g.a.i.ha^(-1) and dicamba 482 g.a.i.ha^(-1) were effective and inhibited the growth and density of the majority of weeds to a 100%;however,they showed significant phytotoxicity(toxicity scale of 1-10)to both species of Miscanthus.The application of glufosinate ammonium caused severe injuries to the foliar region(90%visual injury)of both Miscanthus sps.Comparatively,M.sinensis showed a slightly higher tolerance to the herbicides nicosulfuron,bentazon and napropamide with 10%visual injury at the recommended dose than M.sacchariflorus.The present study clearly showed that infestation of broadleaf and grass weeds in Miscanthus fields can cause significant damage to the growth and biomass of Miscanthus and applying pre-emergence and post-emergence herbicides effectively controls the high infestation of these weeds.展开更多
Control of glyphosate-resistant giant ragweed is a challenge, particularly for soybean growers, because of limited effective post-emergence (POST) herbicide options. Many soybean growers in no-till production systems ...Control of glyphosate-resistant giant ragweed is a challenge, particularly for soybean growers, because of limited effective post-emergence (POST) herbicide options. Many soybean growers in no-till production systems use 2,4-D in burndown application for control of broadleaf weeds, including giant ragweed. Field experiments were conducted at David City, NE, in 2012 and 2013 to evaluate 2,4-D followed by PRE or POST herbicide programs for control of glyphosate-resistant giant ragweed in glyphosate-resistant soybean. Results suggested that burndown application of 2,4-D or saflufenacil plus imazethapyr resulted in 89 to 99% control of giant ragweed at 21 days after treatment. Burndown-only treatments of S-metolachlor plus metribuzin or sulfentrazone plus cloransulam resulted in poor control (≤65%) of giant ragweed and reduced soybean yield (≤ 577 kg·ha-1). Burndown application of 2,4-D followed by saflufenacil plus imazethapyr, S-metolachlor plus metribuzin, or sulfentrazone plus cloransulam applied pre-emergence (PRE) or cloransulam, chlorimuron, fomesafen, imazethapyr, or lactofen in tank-mixtures with acetochlor applied POST resulted in 87% to 99% giant ragweed control, reduced density to ≤7 plants m-2, and resulted in soybean yield from 2519 to 3823 kg·ha-1. There was no difference among and between 2,4-D followed by PRE or POST herbicides for giant ragweed control, density, or soybean yield, indicating all the two pass herbicide programs were effective. It is concluded that glyphosate-resistant giant ragweed can be effectively controlled in soybean by including 2,4-D in burndown program followed by PRE or POST herbicides tested in this study.展开更多
The legacy of the human misery caused by the application of the herbicides including Agent Purple and Agent Orange contaminated with unknown amounts of dioxin TCDD and Agent Blue, the arsenic-based herbicide, sprayed ...The legacy of the human misery caused by the application of the herbicides including Agent Purple and Agent Orange contaminated with unknown amounts of dioxin TCDD and Agent Blue, the arsenic-based herbicide, sprayed over the jungles, rice fields, and hamlets of Vietnam is still haunting us today. Why did this happen? Could it have been prevented? Was it necessary United States military strategy? Was it an intentional decision to inflict this blight on the enemy soldiers and the Vietnamese, Cambodian, and Laotian civilians, to poison their land and cause generations of harm? Alternatively, was it an unpreventable accident in the march of military history? What patterns in the U.S. government’s thought process could be identified as the cause, which led to the decision to use these herbicides as tactical chemical weapons? If the introduction of herbicide (chemical) weapons had not been made, would the outcome of the Vietnam War and the Secret Wars in Laos and Cambodia have been any different? The objective of this treatise is to outline the role of world events and backgrounds and the role of the leaders, U.S. military, CIA, USDA, U.S. State Department, the U.S. President appointed Ambassadors to Vietnam and Laos, chemical companies, and President Diệm’s Republic of Vietnam (RVN) government and military. Their collective advice led to the decision to use herbicides as military and environmental chemical weapons in the Second Indochina War. Were the National interests achieved by U.S. military strategy in the RVN using herbicide weapons worth the long-term environmental and human health consequences in Vietnam, Cambodia, and Laos? Did it impact the outcome of the Second Indochina War?展开更多
[Objectives]The paper was to systematically study the technology of weed control in alfalfa field.[Methods]Reviving alfalfa field and newly sown alfalfa field after emergence were selected,and the effects of different...[Objectives]The paper was to systematically study the technology of weed control in alfalfa field.[Methods]Reviving alfalfa field and newly sown alfalfa field after emergence were selected,and the effects of different herbicides on weed control and alfalfa yield were discussed.[Results]The optimal herbicides after alfalfa reviving were 5%imazethapyr and 10%imazethapyr,and the optimal dosages were 1.5 and 1.05 L/hm 2,respectively.The optimal herbicides after emergence of newly born alfalfa were 5%imazethapyr and 10%imazethapyr,and the optimal dosages were 1.5 and 0.75 L/hm 2,respectively.[Conclusions]This study will provide a technical support for high quality production of alfalfa.展开更多
Background Herbicide tolerance in crops enables them to survive when lethal doses of herbicides are applied to surrounding weeds.Herbicide-tolerant crops can be developed through transgenic approaches or traditional m...Background Herbicide tolerance in crops enables them to survive when lethal doses of herbicides are applied to surrounding weeds.Herbicide-tolerant crops can be developed through transgenic approaches or traditional mutagenesis approaches.At present,no transgenic herbicide tolerant cotton have been commercialized in China due to the genetically-modified organism(GMO)regulation law.We aim to develop a non-transgenic herbicide-tolerant cotton through ethyl methanesulfonate(EMS)mutagenesis,offering an alternative choice for weed management.Results Seeds of an elite cotton cultivar Lumianyan 37(Lu37)were treated with EMS,and a mutant Lu37-1 showed strong tolerance to imidazolinone(IMI)herbicides was identified.A novel nonsynonymous substitution mutation Ser642Asn at acetolactate synthase(ALS)(Gh_D10G1253)in Lu37-1 mutant line was found to be the potential cause to the IMI herbicides tolerance in cotton.The Ser642Asn mutation in ALS did not present among the genomes of natural Gossypium species.Cleaved amplified polymorphic sequence(CAPS)markers were developed to identify the ALS mutant allele.The Arabidopsis overexpressing the mutanted ALS also showed high tolerance to IMI herbicides.Conclusion The nonsynonymous substitution mutation Ser642Asn of the ALS gene Gh_D10G1253 is a novel identi-fied mutation in cotton.This substitution mutation has also been identified in the orthologous ALS genes in other crops.This mutant ALS allele can be used to develop IMI herbicide-tolerant crops via a non-transgenic or transgenic approach.展开更多
This paper mainly analyzes the main limiting factors in the development of biological herbicides,such as narrow herbicidal spectrum,vulnerable to environmental impacts,difficulties in preparing dosage forms,difficult ...This paper mainly analyzes the main limiting factors in the development of biological herbicides,such as narrow herbicidal spectrum,vulnerable to environmental impacts,difficulties in preparing dosage forms,difficult separation and low yield of active substances,biological safety,etc.Moreover,countermeasures and suggestions are put forward,including strengthening the study of biological screening of herbicidal activity,microbial metabolites and their use as lead compounds,dosage forms,fungi complex formulation,fungi and herbicide complex formulation,and fermentation technology.展开更多
The 84 km Panama Canal connecting the Atlantic and Pacific oceans has historically been a strategic waterway for shipping and the location of United States (US) military bases. Since the construction of Lake Gatun res...The 84 km Panama Canal connecting the Atlantic and Pacific oceans has historically been a strategic waterway for shipping and the location of United States (US) military bases. Since the construction of Lake Gatun reservoir, canal locks and navigation channel through the Isthmus of Panama tropical forests in the 1910s, chemicals, pesticides, and herbicides have been essential for controlling upland and wetland vegetation as well as managing mosquito-borne diseases. Chemicals and pesticides flowed into Lake Gatun via land surface runoff and subsurface drainage either attached to the sediment or in solution during the rainy season. Lake Gatun and the Panama Canal was the drinking water source for most of the civilian and military population living in the Panama Canal Zone. Between 1948 and 1999, US military base commanders had the ability to order, from the Federal Supply Catalog, commercially available herbicide 2,4,5-T with unknown amounts of dioxin TCDD for use on the military base grounds in the Panama Canal Zone. The herbicide 2,4,5-T was transported to Panama Canal Zone ports, including the ports Cristobal on the Caribbean and Balboa on the Pacific, and distributed to the US military bases in Panama by rail or truck. The US National Toxicology Program and the International Agency for the Research on Cancer listed dioxin and TCDD as known human carcinogens. Dioxins are endocrine disrupters and can cause certain chloracne, cancers, developmental and reproductive effects. In 1985, the United States government banned the manufacture of the herbicide 2,4,5-T, with unknown amounts of dioxin TCDD, after it was shown to cause cancer in animals. The objectives of this study are to determine: 1) the fate of dioxin TCDD, a contaminant in the herbicide 2,4,5-T, sprayed on the US military base vegetation in the Panama Canal Zone from 1948 to 1999, 2) the transport of dioxin TCDD rich sediment via soil erosion and overland flow into Lake Gatun and Panama Canal waterways and 3) the human health impacts of dioxin TCDD, a known carcinogen, on US military and Panamanian civilians exposed to dioxin TCDD in the Panama Canal Zone.展开更多
Selecting a preemergence (PRE) and postemergence (POST) herbicide program that has the greatest efficacy can be difficult for corn producers and is highly dependent on weed spectrum. Weather conditions before and afte...Selecting a preemergence (PRE) and postemergence (POST) herbicide program that has the greatest efficacy can be difficult for corn producers and is highly dependent on weed spectrum. Weather conditions before and after herbicide application can further complicate decisions because they influence herbicide efficacy. Eleven field trials were conducted at three locations in Southwestern Ontario from 2003 to 2006, to determine the most effective PRE and POST corn herbicides for weed control. The most abundant weed species across all locations were redroot pigweed (Amaranthus retroflexus L.), common ragweed (Ambrosia artemisiifolia L.), common lambsquarters (Chenopodium album L.), and green foxtail (Setaria viridis (L.) Beauv.). Nine PRE herbicide treatments and eleven POST (applied at the 3-4 leaf stage of corn) herbicide treatments were tested. Results from this study suggest that the timing and amount of precipitation influence herbicide efficacy. For example, precipitation levels 0-17 mm within seven days after herbicide application (PRE or POST) provided unacceptable weed control in treatments that included atrazine, dimethenamidp, isoxa-flutole/atrazine or S-metolachlor/benoxacor. Cumulative precipitation during the 14 days after PRE application that exceeded the monthly average (by at least 64%) reduced Setaria viridis control with pendimethalin. This study demonstrates that a better understanding of how environmental conditions, especially precipitation affect herbicide efficacy, need to be considered by growers when selecting a corn herbicide program to reduce the possibility of weed control failure.展开更多
[ Objective] The paper was to explore the control effects of 3 kinds of herbicides against weeds in dogbane (Apocynum venetum) field. [ Method ] Using haloxyfop-R-mithyl and quizalofop-ethyl EC specifically killing ...[ Objective] The paper was to explore the control effects of 3 kinds of herbicides against weeds in dogbane (Apocynum venetum) field. [ Method ] Using haloxyfop-R-mithyl and quizalofop-ethyl EC specifically killing monagenns gramineous weeds and chipton specifically killing dicotyledonous broad-leaf weeds, the control test against weeds in 2-year-old dogbane field was carried out. [ Result ] Haloxyfop-R-mithyl had good control effect against gramincous weeds, and its control effect against both barnyard weed ( Echinochloa crusgalli) and green bristleweed ( Setaria viridis ) was greater than 35.0% ; the control effects of quizalofop- ethyl EC against barnyard weed and green bristleweed were 14.8% and 28.6%, respectively; chipt0n had good control effect against Chenopodium album, and the control effect reached 30.8%. Moreover, 3 herbicides did not cause damage to dogbane. [ Conclusion] The study provide theoretical basis for completing cultivation technique of dogbane.展开更多
In order to screen herbicides with ideal safety characteristics to control malignant weed nut grass in sugarcane field, 20% thifensulfuron methyl WP and 65% MCPA·ametryne·diuron WP were selected for the fiel...In order to screen herbicides with ideal safety characteristics to control malignant weed nut grass in sugarcane field, 20% thifensulfuron methyl WP and 65% MCPA·ametryne·diuron WP were selected for the field efficacy trial. The results showed that 20% thifensulfuron methyl WP and 65% MCPA·ametryne·diuron WP had good control effect on nut grass. The optimum dosage of 20% thifensulfuron methyl WP and 65% MCPA.ametryne-diuron WP was 1 125 g/hm^2 (effective ingredients 225 g) and 3 150 g/hm^2 (effective ingredients 2 047.5 g), respectively. These two herbicides should be dissolved in 675 kg water per hectare and applied in the vigorous growth period of nut grass (height 10-15 cm) with oriented stem leaf spraying. The control effect after 15 days could be above 87.9%.展开更多
The widespread use of chemical herbicides especially amide herbicides has promoted the innovation of chemical weeding in farmland, but amide herbicides have brought invisible chemical injuries to crops in addition to ...The widespread use of chemical herbicides especially amide herbicides has promoted the innovation of chemical weeding in farmland, but amide herbicides have brought invisible chemical injuries to crops in addition to weeding. Herbi-cidesafeners should be applied at the same time with herbicides to ensure herbi- cides will not injure crops while controlling weeds. The research and application of safeners is of great significance to resolving or alleviating the negative effects of herbicides on crop growth. The overview, mechanism, applied research progress and existing problems of amide herbicides and their safenars are summarized.展开更多
[Objective]The aim was to study the effect of herbicide on the growth of early seedlings of rye(Secale cereale).[Method]Effect of two kinds of herbicide(Atrazine and APM)on seedling growth of rye was investigated ...[Objective]The aim was to study the effect of herbicide on the growth of early seedlings of rye(Secale cereale).[Method]Effect of two kinds of herbicide(Atrazine and APM)on seedling growth of rye was investigated at the physiological,biochemical and cellular level.[Result]The Atrazin significantly decreased the contents of chlorophyll a,b and soluble proteins.Rye seeds were treated with 0.01-1 mg/L Atrazine for 16 h,the contents of chlorophyll a and b decreased from 1.26(a),0.49(b)mg/g FW(control)to 1.15(a),0.46(b)mg/g FW(0.1 mg/L)and 0.81(a),0.33(b)mg/g FW(1.0 mg/L).The content of soluble protein decreased with the increasing concentration of Atrazin.Atrazin had no significant influence on the cell division and chromosome structure variation.The contents of chlorophyll a,b and soluble proteins had no significantly change under the treatment of APM,but the number of chromosome structure variation such as chromosome bridge,multipolar division cells,lagging chromosome and unequal division cells increased significantly.[Conclusion]The critical concentration of Atrazine was 0.1-1.0 mg/L and 4 mg/L of APM in rye.展开更多
Rapeseed is a very important oil crop in China; however, its production is challenging due to the absence of effective weed management strategies. This is predominantly because of a shortage of herbicide resistance ge...Rapeseed is a very important oil crop in China; however, its production is challenging due to the absence of effective weed management strategies. This is predominantly because of a shortage of herbicide resistance genes. Acetohydroxyacid synthase (AHAS) herbicides inhibit AHAS, a key enzyme involved in branched-chain amino acid synthesis that is required for plant growth. A rapeseed line designated M342 with AHAS herbicide resistance was developed through seed muta- genesis and was studied to assess the level and mode of inheritance of the resistance and to identify the molecular basis of resistance. M342 possessed a high level of cross-resistance to sulfonylureas (SUs) and imidazolinones (IMIs). This resistance was due to AHAS insensitivity to these herbicides and was inherited as a dominant trait conferred by a single nuclear-encoded gene. Molecular analysis revealed the presence of a Trp574Leu mutation in M342, and an allele-specific cleaved amplified polymorphic sequence (AS-CAPS) marker was developed and cosegregated with herbicide resistance in the F2, BC1, and BC2 populations. This mutation altered the transcript levels of BnAHAS1 and BnAHAS3 in M342 compared with those in the wild type, but it did not affect the agronomic or quality traits. The simple genetic inheritance of this mutation and the availability of the cleaved amplified polymorphic sequence (CAPS) marker and herbicide resistance gene should facilitate the development of herbicide-resistant rapeseed cultivars for effective weed control in China.展开更多
To investigate the combined effects of Cd^2+ ( 0,10,100,500 μmol/L) , acetochlor (AC) (0,1.6,4.0,8.0μmol/L), and bensulfuronmethyl (BSM) ( 0,0.16,0.40,0.80 μmol/L) on the biomass,leaf soluble sugar, tota...To investigate the combined effects of Cd^2+ ( 0,10,100,500 μmol/L) , acetochlor (AC) (0,1.6,4.0,8.0μmol/L), and bensulfuronmethyl (BSM) ( 0,0.16,0.40,0.80 μmol/L) on the biomass,leaf soluble sugar, total chlorophyll (chl) content, chl a/b ratio, and Cd content in roots and shoots in the rice seedlings, pot culture experiments were conducted with rice (Oryza sativa L. ) cultivar Jinyou 402. The results showed that the Cd and AC combined treatment (Cd+ AC treatment) significantly inhibited the growth of the roots and shoots. The root dry weight/shoot dry weight (RDW/SDW) ratio, total chlorophyll content and chl a/b ratio decreased by 41%, 50%, 56% , respectively, in comparison with the control, as well as the leaf soluble sugar content, plant dry weight /plant fresh weight (PDW/PFW) ratio increased by 284% and 44% , respectively. Cd content in the roots and shoots had a decreasing tendency with the increasing concentration of AC under the Cd+AC treatment. The Cd and BSM combined treatment (Cd+BSM treatment) had a similar result to the Cd+AC treatment. The results suggest that the toxicity of Cd to rice seedlings has been enhanced due to its combination with herbicides.展开更多
This study was conducted to investigate the dissipation pattern and runoff of herbicides to the river basin from the paddy fields. Pesticide paddy field model(PADDY) was applied to predict herbicide concentration in p...This study was conducted to investigate the dissipation pattern and runoff of herbicides to the river basin from the paddy fields. Pesticide paddy field model(PADDY) was applied to predict herbicide concentration in paddy fields. A field study was conducted in a paddy farm of Higashi Hiroshima City, Hiroshima Prefecture, Japan in the year of 2003 paddy season. The herbicides were mefenacet, thiobencarb, and bensulfuron methyl. The sample water was analyzed by using gas chromatography and HPLC after solid phase extraction. Predicted dissipation rate of thiobencarb in paddy water was higher(DT_ 50 = 4 36) than that measured, with a lower k value(-0 069). Two weeks after application no thiobencarb was detected in the drainage channel and down stream. In the down stream, thiobencarb was detected until 3 d after application, with a range of 0 02% to 0 08% of applied herbicide. The predicted dissipation rate(k) and half-life(DT_ 50 ) of mefenacet was not significantly different from that of measured. In the drainage channel, upstream and downstream mefenacet was found during the whole study period. In downstream, the maximum concentration of mefenacet was present 0 61% of applied in the paddy field on 3DAH. The dissipation rate(k) of BSM varied from -0 0860 to -0 1059 to with half-life(DT_ 50 ) 3 5 and 2 84 d. In upstream water, no BSM was detected except trace amounts(0 01 μg/L) at 3 d after application. However, in the drainage channel 8%, 6% and 1 58% of applied BSM was present at 0, 1 and 3 d after application respectively. In the down stream, the highest concentration was 1 06%, shortly after application.展开更多
The physiological effects of 4 herbicides (butachlor, quinclorac, bensulfuron-methyl and atrazine) on 3 submerged macrophytes (Ceratophyllum demersum, Vallisneria natans and Elodea nuttallii) were tested in labora...The physiological effects of 4 herbicides (butachlor, quinclorac, bensulfuron-methyl and atrazine) on 3 submerged macrophytes (Ceratophyllum demersum, Vallisneria natans and Elodea nuttallii) were tested in laboratory. The variables of the relative growth rate and the photosynthetic pigment content showed that all of the tested herbicides affected the growth of the plants obviously, even at the lowest concentration (0.0001 mg/L). Except for the C. demersum treated with quinclorac at 0.005 and 0.01 mg/L, the relative growth rates of the plants were inhibited significantly (p 〈 0.01). Statistical analysis of chlorophyll a (Chl-a) contents was carded out with both the t-test and one-way ANOVA to determine the difference between the treatment and control. The results showed that Chl-a contents of the plants in all treatment groups were affected by herbicides significantly, except for the C. demersum treated with bensulfuron-methyl at 0.0005 mg/L. The decrease in Chl-a content was positively correlated to the dosage of the herbicides in most treatment groups. It was suggested that herbicides in water bodies might potentially affect the growth of aquatic macrophytes. Since the Chl-a content of submerged macrophytes responded to the stress of herbicides sensitively and directly, it could be used as a biomaker in environmental monitoring or in the ecological risk assessment of herbicide contamination.展开更多
Adsorption of atrazine, prometryne and prometon was determined on six soils with different physical and chemical properties. The adsorption isotherms of three herbicides could well fit Freundlich equation. On all of s...Adsorption of atrazine, prometryne and prometon was determined on six soils with different physical and chemical properties. The adsorption isotherms of three herbicides could well fit Freundlich equation. On all of six soils, adsorption of herbicides increased in the order: atrazine ≈prometon<prometryne. This order is quite the same to the calculation result of by means of excess thermodynamic properties of triazine. The Freundlich adsorption constants, K f, showed to have good correlation with organic matter(OM%) of soils for each of these herbicides, suggesting that OM is the main factor, which dominates in the adsorption process of these triazine herbicides.展开更多
Herbicide resistance in crop plants is valuable for integrated weed management in agriculture. Herbicide resistant rice, in particular, is important to management of weedy rice, a close relative of cultivated rice and...Herbicide resistance in crop plants is valuable for integrated weed management in agriculture. Herbicide resistant rice, in particular, is important to management of weedy rice, a close relative of cultivated rice and a noxious weed prevalent in rice fields that remains challenging to farmers worldwide. Herbicide resistant plants can be obtained through transgenic approach or by mutagenesis of regular plant and screening of mutants with elevated resistance to herbicide. In this study, we conducted ethyl methyl sulfonate mutagenesis(EMS) to elite indica cultivar Huanghuazhan(HHZ) and screened for mutants resistant to imazapic, a herbicide that can inhibit the acetolactate synthase(ALS) in plants. We obtained three mutants of Os ALS gene that have not been reported previously in rice. One of the mutants, with Trp_(548) changed to Met(W_(548)M), was analyzed in more details in this study. This mutation had no negative effect on the plant physiology and morphology as well as rice yield. Compared with the imidazolinone-resistant mutant S_(627)N(Ser_(627) changed to Asn) that has been deployed for Clearfield rice development, W_(548)M mutant showed high levels of resistance to a broad spectrum of five families of ALSinhibiting herbicides, in addition to a higher level of resistance to herbicides of the imidazolinone family.The herbicide-resistance was stably inherited by crossing into other rice lines. Thus, the W_(548)M mutation provides a valuable resource for breeding of herbicide resistant rice and weed management.展开更多
Adsorption of chloroacetanilide herbicides on homoionic montmorillonite, soil humic acid, and their mixtures was studied by coupling batch equilibration and FT IR analysis. Adsorption isotherms of acetochlor, alachlo...Adsorption of chloroacetanilide herbicides on homoionic montmorillonite, soil humic acid, and their mixtures was studied by coupling batch equilibration and FT IR analysis. Adsorption isotherms of acetochlor, alachlor, metolachlor and propachlor on Ca 2+ \|, Mg 2+ \|, Al 3+ \| and Fe 3+ \| saturated clays were well described by the Freundlich equation. Regardless of the type of exchange cations, K f decreased in the order of metolachlor > acetolachlor > alachlor > propachlor on the same clay. FT IR spectra showed that the carbonyl group of the herbicide molecule was involved in binding, probably via H bond with water molecules in the clay interlayer. The type and position of substitutions around the carbonyl group may have affected the electronegativity of oxygen, thus influencing the relative adsorption of these herbicides. For the same herbicide, adsorption on clay increased in the order of Mg 2+ <Ca 2+ <Al 3+ ≤Fe 3+ which coincided with the increasing acidity of homoionic clays. Acidity of cations may have affected the protonation of water, and thus the strength of H bond between the clay water and herbicide. Complexation of clay and humic acid resulted in less adsorption than that expected from independent adsorption by the individual constituents. The effect varied with herbicides, but the greatest decrease in adsorption occurred at a 60:40 clay to humic acid ratio for all the herbicides. Causes for the decreased adsorption need to be characterized to better understand adsorption mechanisms and predict adsorption from soil compositions.展开更多
Differential pulse stripping voltammetry method(DPSV) was applied to the determination of three herbicides, ametryn, cyanatryn, and dimethametryn. It was found that their voltammograms overlapped strongly, and it is...Differential pulse stripping voltammetry method(DPSV) was applied to the determination of three herbicides, ametryn, cyanatryn, and dimethametryn. It was found that their voltammograms overlapped strongly, and it is difficult to determine these compounds individually from their mixtures. With the aid of chemometrics, classical least squares(CLS), principal component regression(PCR) and partial least squares(PLS), voltammogram resolution and quantitative analysis of the synthetic mixtures of the three compounds were successfully performed. The proposed method was also applied to the analysis of some real samples with satisfactory results.展开更多
基金This work was supported by a BrainKorea21 Plus(BK21+,Grant No.22A20153813519,Team:Omics Research of Crop Bioresources for Future,Konkuk University),the National Research Foundation of Korea,Republic of Korea.
文摘Miscanthus,is a promising bioenergy crop,considered superior to other bioenergy crops because of its higher water and nutrient use efficiency,cold tolerance,and higher production of biomass.Broadleaf weeds and grass weeds,cause major problems in the Miscanthus field.A field experiment was conducted in 2018 and 2019,to assess the effects of pre-emergence(alachlor and napropamide)and post-emergence herbicides(nicosulfuron,dicamba,bentazon,and glufosinate ammonium)on broadleaf and grass weeds in M.sinensis and M.sacchariflorus fields.The weed control efficiency and phytotoxicity of pre-and post-emergence herbicides were evaluated at 30 days after treatment(DAT)and compared to those of the control plots.The results showed wide variations in the susceptibility of the weed species to the treated herbicides.Treatment with nicosulfuron 40 g.a.i.ha^(-1) provided the most effective overall weed control(with 10%visual injury),without affecting the height and biomass of neither Miscanthus species in the field.Post-emergence herbicides such as glufosinate ammonium 400 g.a.i.ha^(-1) and dicamba 482 g.a.i.ha^(-1) were effective and inhibited the growth and density of the majority of weeds to a 100%;however,they showed significant phytotoxicity(toxicity scale of 1-10)to both species of Miscanthus.The application of glufosinate ammonium caused severe injuries to the foliar region(90%visual injury)of both Miscanthus sps.Comparatively,M.sinensis showed a slightly higher tolerance to the herbicides nicosulfuron,bentazon and napropamide with 10%visual injury at the recommended dose than M.sacchariflorus.The present study clearly showed that infestation of broadleaf and grass weeds in Miscanthus fields can cause significant damage to the growth and biomass of Miscanthus and applying pre-emergence and post-emergence herbicides effectively controls the high infestation of these weeds.
文摘Control of glyphosate-resistant giant ragweed is a challenge, particularly for soybean growers, because of limited effective post-emergence (POST) herbicide options. Many soybean growers in no-till production systems use 2,4-D in burndown application for control of broadleaf weeds, including giant ragweed. Field experiments were conducted at David City, NE, in 2012 and 2013 to evaluate 2,4-D followed by PRE or POST herbicide programs for control of glyphosate-resistant giant ragweed in glyphosate-resistant soybean. Results suggested that burndown application of 2,4-D or saflufenacil plus imazethapyr resulted in 89 to 99% control of giant ragweed at 21 days after treatment. Burndown-only treatments of S-metolachlor plus metribuzin or sulfentrazone plus cloransulam resulted in poor control (≤65%) of giant ragweed and reduced soybean yield (≤ 577 kg·ha-1). Burndown application of 2,4-D followed by saflufenacil plus imazethapyr, S-metolachlor plus metribuzin, or sulfentrazone plus cloransulam applied pre-emergence (PRE) or cloransulam, chlorimuron, fomesafen, imazethapyr, or lactofen in tank-mixtures with acetochlor applied POST resulted in 87% to 99% giant ragweed control, reduced density to ≤7 plants m-2, and resulted in soybean yield from 2519 to 3823 kg·ha-1. There was no difference among and between 2,4-D followed by PRE or POST herbicides for giant ragweed control, density, or soybean yield, indicating all the two pass herbicide programs were effective. It is concluded that glyphosate-resistant giant ragweed can be effectively controlled in soybean by including 2,4-D in burndown program followed by PRE or POST herbicides tested in this study.
文摘The legacy of the human misery caused by the application of the herbicides including Agent Purple and Agent Orange contaminated with unknown amounts of dioxin TCDD and Agent Blue, the arsenic-based herbicide, sprayed over the jungles, rice fields, and hamlets of Vietnam is still haunting us today. Why did this happen? Could it have been prevented? Was it necessary United States military strategy? Was it an intentional decision to inflict this blight on the enemy soldiers and the Vietnamese, Cambodian, and Laotian civilians, to poison their land and cause generations of harm? Alternatively, was it an unpreventable accident in the march of military history? What patterns in the U.S. government’s thought process could be identified as the cause, which led to the decision to use these herbicides as tactical chemical weapons? If the introduction of herbicide (chemical) weapons had not been made, would the outcome of the Vietnam War and the Secret Wars in Laos and Cambodia have been any different? The objective of this treatise is to outline the role of world events and backgrounds and the role of the leaders, U.S. military, CIA, USDA, U.S. State Department, the U.S. President appointed Ambassadors to Vietnam and Laos, chemical companies, and President Diệm’s Republic of Vietnam (RVN) government and military. Their collective advice led to the decision to use herbicides as military and environmental chemical weapons in the Second Indochina War. Were the National interests achieved by U.S. military strategy in the RVN using herbicide weapons worth the long-term environmental and human health consequences in Vietnam, Cambodia, and Laos? Did it impact the outcome of the Second Indochina War?
文摘[Objectives]The paper was to systematically study the technology of weed control in alfalfa field.[Methods]Reviving alfalfa field and newly sown alfalfa field after emergence were selected,and the effects of different herbicides on weed control and alfalfa yield were discussed.[Results]The optimal herbicides after alfalfa reviving were 5%imazethapyr and 10%imazethapyr,and the optimal dosages were 1.5 and 1.05 L/hm 2,respectively.The optimal herbicides after emergence of newly born alfalfa were 5%imazethapyr and 10%imazethapyr,and the optimal dosages were 1.5 and 0.75 L/hm 2,respectively.[Conclusions]This study will provide a technical support for high quality production of alfalfa.
基金This research was funded by the National Key Research and Development Program of China,grant number 2016YFD0101418the National Natural Science Foundation of China,grant number 32172047.
文摘Background Herbicide tolerance in crops enables them to survive when lethal doses of herbicides are applied to surrounding weeds.Herbicide-tolerant crops can be developed through transgenic approaches or traditional mutagenesis approaches.At present,no transgenic herbicide tolerant cotton have been commercialized in China due to the genetically-modified organism(GMO)regulation law.We aim to develop a non-transgenic herbicide-tolerant cotton through ethyl methanesulfonate(EMS)mutagenesis,offering an alternative choice for weed management.Results Seeds of an elite cotton cultivar Lumianyan 37(Lu37)were treated with EMS,and a mutant Lu37-1 showed strong tolerance to imidazolinone(IMI)herbicides was identified.A novel nonsynonymous substitution mutation Ser642Asn at acetolactate synthase(ALS)(Gh_D10G1253)in Lu37-1 mutant line was found to be the potential cause to the IMI herbicides tolerance in cotton.The Ser642Asn mutation in ALS did not present among the genomes of natural Gossypium species.Cleaved amplified polymorphic sequence(CAPS)markers were developed to identify the ALS mutant allele.The Arabidopsis overexpressing the mutanted ALS also showed high tolerance to IMI herbicides.Conclusion The nonsynonymous substitution mutation Ser642Asn of the ALS gene Gh_D10G1253 is a novel identi-fied mutation in cotton.This substitution mutation has also been identified in the orthologous ALS genes in other crops.This mutant ALS allele can be used to develop IMI herbicide-tolerant crops via a non-transgenic or transgenic approach.
文摘This paper mainly analyzes the main limiting factors in the development of biological herbicides,such as narrow herbicidal spectrum,vulnerable to environmental impacts,difficulties in preparing dosage forms,difficult separation and low yield of active substances,biological safety,etc.Moreover,countermeasures and suggestions are put forward,including strengthening the study of biological screening of herbicidal activity,microbial metabolites and their use as lead compounds,dosage forms,fungi complex formulation,fungi and herbicide complex formulation,and fermentation technology.
文摘The 84 km Panama Canal connecting the Atlantic and Pacific oceans has historically been a strategic waterway for shipping and the location of United States (US) military bases. Since the construction of Lake Gatun reservoir, canal locks and navigation channel through the Isthmus of Panama tropical forests in the 1910s, chemicals, pesticides, and herbicides have been essential for controlling upland and wetland vegetation as well as managing mosquito-borne diseases. Chemicals and pesticides flowed into Lake Gatun via land surface runoff and subsurface drainage either attached to the sediment or in solution during the rainy season. Lake Gatun and the Panama Canal was the drinking water source for most of the civilian and military population living in the Panama Canal Zone. Between 1948 and 1999, US military base commanders had the ability to order, from the Federal Supply Catalog, commercially available herbicide 2,4,5-T with unknown amounts of dioxin TCDD for use on the military base grounds in the Panama Canal Zone. The herbicide 2,4,5-T was transported to Panama Canal Zone ports, including the ports Cristobal on the Caribbean and Balboa on the Pacific, and distributed to the US military bases in Panama by rail or truck. The US National Toxicology Program and the International Agency for the Research on Cancer listed dioxin and TCDD as known human carcinogens. Dioxins are endocrine disrupters and can cause certain chloracne, cancers, developmental and reproductive effects. In 1985, the United States government banned the manufacture of the herbicide 2,4,5-T, with unknown amounts of dioxin TCDD, after it was shown to cause cancer in animals. The objectives of this study are to determine: 1) the fate of dioxin TCDD, a contaminant in the herbicide 2,4,5-T, sprayed on the US military base vegetation in the Panama Canal Zone from 1948 to 1999, 2) the transport of dioxin TCDD rich sediment via soil erosion and overland flow into Lake Gatun and Panama Canal waterways and 3) the human health impacts of dioxin TCDD, a known carcinogen, on US military and Panamanian civilians exposed to dioxin TCDD in the Panama Canal Zone.
文摘Selecting a preemergence (PRE) and postemergence (POST) herbicide program that has the greatest efficacy can be difficult for corn producers and is highly dependent on weed spectrum. Weather conditions before and after herbicide application can further complicate decisions because they influence herbicide efficacy. Eleven field trials were conducted at three locations in Southwestern Ontario from 2003 to 2006, to determine the most effective PRE and POST corn herbicides for weed control. The most abundant weed species across all locations were redroot pigweed (Amaranthus retroflexus L.), common ragweed (Ambrosia artemisiifolia L.), common lambsquarters (Chenopodium album L.), and green foxtail (Setaria viridis (L.) Beauv.). Nine PRE herbicide treatments and eleven POST (applied at the 3-4 leaf stage of corn) herbicide treatments were tested. Results from this study suggest that the timing and amount of precipitation influence herbicide efficacy. For example, precipitation levels 0-17 mm within seven days after herbicide application (PRE or POST) provided unacceptable weed control in treatments that included atrazine, dimethenamidp, isoxa-flutole/atrazine or S-metolachlor/benoxacor. Cumulative precipitation during the 14 days after PRE application that exceeded the monthly average (by at least 64%) reduced Setaria viridis control with pendimethalin. This study demonstrates that a better understanding of how environmental conditions, especially precipitation affect herbicide efficacy, need to be considered by growers when selecting a corn herbicide program to reduce the possibility of weed control failure.
基金Supported by "948" Project of National Forestry Bureau ( 2004-04-10)~~
文摘[ Objective] The paper was to explore the control effects of 3 kinds of herbicides against weeds in dogbane (Apocynum venetum) field. [ Method ] Using haloxyfop-R-mithyl and quizalofop-ethyl EC specifically killing monagenns gramineous weeds and chipton specifically killing dicotyledonous broad-leaf weeds, the control test against weeds in 2-year-old dogbane field was carried out. [ Result ] Haloxyfop-R-mithyl had good control effect against gramincous weeds, and its control effect against both barnyard weed ( Echinochloa crusgalli) and green bristleweed ( Setaria viridis ) was greater than 35.0% ; the control effects of quizalofop- ethyl EC against barnyard weed and green bristleweed were 14.8% and 28.6%, respectively; chipt0n had good control effect against Chenopodium album, and the control effect reached 30.8%. Moreover, 3 herbicides did not cause damage to dogbane. [ Conclusion] The study provide theoretical basis for completing cultivation technique of dogbane.
基金Supported by Earmarked Fund for China Agriculture Research System(CARS-20-2-2)Project for Yunnan Provincial Modern Agricultural Industry Technology System(YNGZTX-4-92)~~
文摘In order to screen herbicides with ideal safety characteristics to control malignant weed nut grass in sugarcane field, 20% thifensulfuron methyl WP and 65% MCPA·ametryne·diuron WP were selected for the field efficacy trial. The results showed that 20% thifensulfuron methyl WP and 65% MCPA·ametryne·diuron WP had good control effect on nut grass. The optimum dosage of 20% thifensulfuron methyl WP and 65% MCPA.ametryne-diuron WP was 1 125 g/hm^2 (effective ingredients 225 g) and 3 150 g/hm^2 (effective ingredients 2 047.5 g), respectively. These two herbicides should be dissolved in 675 kg water per hectare and applied in the vigorous growth period of nut grass (height 10-15 cm) with oriented stem leaf spraying. The control effect after 15 days could be above 87.9%.
基金Supported by Special Fund for Agro-scientific Research in the Public Interest(201303031)Strategic Emerging Industries Key Technology and Major Science and Technology Achievement Transformation in Hunan Province(2014GK1040)~~
文摘The widespread use of chemical herbicides especially amide herbicides has promoted the innovation of chemical weeding in farmland, but amide herbicides have brought invisible chemical injuries to crops in addition to weeding. Herbi-cidesafeners should be applied at the same time with herbicides to ensure herbi- cides will not injure crops while controlling weeds. The research and application of safeners is of great significance to resolving or alleviating the negative effects of herbicides on crop growth. The overview, mechanism, applied research progress and existing problems of amide herbicides and their safenars are summarized.
基金Supported by Key Project for Science Researches of Ministry of Education(02010)~~
文摘[Objective]The aim was to study the effect of herbicide on the growth of early seedlings of rye(Secale cereale).[Method]Effect of two kinds of herbicide(Atrazine and APM)on seedling growth of rye was investigated at the physiological,biochemical and cellular level.[Result]The Atrazin significantly decreased the contents of chlorophyll a,b and soluble proteins.Rye seeds were treated with 0.01-1 mg/L Atrazine for 16 h,the contents of chlorophyll a and b decreased from 1.26(a),0.49(b)mg/g FW(control)to 1.15(a),0.46(b)mg/g FW(0.1 mg/L)and 0.81(a),0.33(b)mg/g FW(1.0 mg/L).The content of soluble protein decreased with the increasing concentration of Atrazin.Atrazin had no significant influence on the cell division and chromosome structure variation.The contents of chlorophyll a,b and soluble proteins had no significantly change under the treatment of APM,but the number of chromosome structure variation such as chromosome bridge,multipolar division cells,lagging chromosome and unequal division cells increased significantly.[Conclusion]The critical concentration of Atrazine was 0.1-1.0 mg/L and 4 mg/L of APM in rye.
基金supported by the National Natural Science Foundation of China(31671731)the National Key Research and Development Program of China(2016YFD0101300)+2 种基金the China Agricultural Research System(CARS-13)the Natural Science Foundation of Jiangsu Province,China(BK20151369)the Science Foundation of Jiangsu Academy of Agricultural Sciences,China(6111618)
文摘Rapeseed is a very important oil crop in China; however, its production is challenging due to the absence of effective weed management strategies. This is predominantly because of a shortage of herbicide resistance genes. Acetohydroxyacid synthase (AHAS) herbicides inhibit AHAS, a key enzyme involved in branched-chain amino acid synthesis that is required for plant growth. A rapeseed line designated M342 with AHAS herbicide resistance was developed through seed muta- genesis and was studied to assess the level and mode of inheritance of the resistance and to identify the molecular basis of resistance. M342 possessed a high level of cross-resistance to sulfonylureas (SUs) and imidazolinones (IMIs). This resistance was due to AHAS insensitivity to these herbicides and was inherited as a dominant trait conferred by a single nuclear-encoded gene. Molecular analysis revealed the presence of a Trp574Leu mutation in M342, and an allele-specific cleaved amplified polymorphic sequence (AS-CAPS) marker was developed and cosegregated with herbicide resistance in the F2, BC1, and BC2 populations. This mutation altered the transcript levels of BnAHAS1 and BnAHAS3 in M342 compared with those in the wild type, but it did not affect the agronomic or quality traits. The simple genetic inheritance of this mutation and the availability of the cleaved amplified polymorphic sequence (CAPS) marker and herbicide resistance gene should facilitate the development of herbicide-resistant rapeseed cultivars for effective weed control in China.
基金Supported by Foundation for University Key Teacher by theMinistry of Education
文摘To investigate the combined effects of Cd^2+ ( 0,10,100,500 μmol/L) , acetochlor (AC) (0,1.6,4.0,8.0μmol/L), and bensulfuronmethyl (BSM) ( 0,0.16,0.40,0.80 μmol/L) on the biomass,leaf soluble sugar, total chlorophyll (chl) content, chl a/b ratio, and Cd content in roots and shoots in the rice seedlings, pot culture experiments were conducted with rice (Oryza sativa L. ) cultivar Jinyou 402. The results showed that the Cd and AC combined treatment (Cd+ AC treatment) significantly inhibited the growth of the roots and shoots. The root dry weight/shoot dry weight (RDW/SDW) ratio, total chlorophyll content and chl a/b ratio decreased by 41%, 50%, 56% , respectively, in comparison with the control, as well as the leaf soluble sugar content, plant dry weight /plant fresh weight (PDW/PFW) ratio increased by 284% and 44% , respectively. Cd content in the roots and shoots had a decreasing tendency with the increasing concentration of AC under the Cd+AC treatment. The Cd and BSM combined treatment (Cd+BSM treatment) had a similar result to the Cd+AC treatment. The results suggest that the toxicity of Cd to rice seedlings has been enhanced due to its combination with herbicides.
文摘This study was conducted to investigate the dissipation pattern and runoff of herbicides to the river basin from the paddy fields. Pesticide paddy field model(PADDY) was applied to predict herbicide concentration in paddy fields. A field study was conducted in a paddy farm of Higashi Hiroshima City, Hiroshima Prefecture, Japan in the year of 2003 paddy season. The herbicides were mefenacet, thiobencarb, and bensulfuron methyl. The sample water was analyzed by using gas chromatography and HPLC after solid phase extraction. Predicted dissipation rate of thiobencarb in paddy water was higher(DT_ 50 = 4 36) than that measured, with a lower k value(-0 069). Two weeks after application no thiobencarb was detected in the drainage channel and down stream. In the down stream, thiobencarb was detected until 3 d after application, with a range of 0 02% to 0 08% of applied herbicide. The predicted dissipation rate(k) and half-life(DT_ 50 ) of mefenacet was not significantly different from that of measured. In the drainage channel, upstream and downstream mefenacet was found during the whole study period. In downstream, the maximum concentration of mefenacet was present 0 61% of applied in the paddy field on 3DAH. The dissipation rate(k) of BSM varied from -0 0860 to -0 1059 to with half-life(DT_ 50 ) 3 5 and 2 84 d. In upstream water, no BSM was detected except trace amounts(0 01 μg/L) at 3 d after application. However, in the drainage channel 8%, 6% and 1 58% of applied BSM was present at 0, 1 and 3 d after application respectively. In the down stream, the highest concentration was 1 06%, shortly after application.
基金supported by the Hi-Tech Re-search and Development Program (863) of China (No.2007AA06A405)the National Basic Research Pro-gram (973) Project of China (No. 2002CB412307)
文摘The physiological effects of 4 herbicides (butachlor, quinclorac, bensulfuron-methyl and atrazine) on 3 submerged macrophytes (Ceratophyllum demersum, Vallisneria natans and Elodea nuttallii) were tested in laboratory. The variables of the relative growth rate and the photosynthetic pigment content showed that all of the tested herbicides affected the growth of the plants obviously, even at the lowest concentration (0.0001 mg/L). Except for the C. demersum treated with quinclorac at 0.005 and 0.01 mg/L, the relative growth rates of the plants were inhibited significantly (p 〈 0.01). Statistical analysis of chlorophyll a (Chl-a) contents was carded out with both the t-test and one-way ANOVA to determine the difference between the treatment and control. The results showed that Chl-a contents of the plants in all treatment groups were affected by herbicides significantly, except for the C. demersum treated with bensulfuron-methyl at 0.0005 mg/L. The decrease in Chl-a content was positively correlated to the dosage of the herbicides in most treatment groups. It was suggested that herbicides in water bodies might potentially affect the growth of aquatic macrophytes. Since the Chl-a content of submerged macrophytes responded to the stress of herbicides sensitively and directly, it could be used as a biomaker in environmental monitoring or in the ecological risk assessment of herbicide contamination.
文摘Adsorption of atrazine, prometryne and prometon was determined on six soils with different physical and chemical properties. The adsorption isotherms of three herbicides could well fit Freundlich equation. On all of six soils, adsorption of herbicides increased in the order: atrazine ≈prometon<prometryne. This order is quite the same to the calculation result of by means of excess thermodynamic properties of triazine. The Freundlich adsorption constants, K f, showed to have good correlation with organic matter(OM%) of soils for each of these herbicides, suggesting that OM is the main factor, which dominates in the adsorption process of these triazine herbicides.
基金supported by Major Program of Guangdong Basic and Applied Research(2019B030302006)National Natural Science Foundation of China(U1901203 and 31901532)+2 种基金Natural Science Foundation of Guangdong Province(2018B030308008 and 2018A0303130270)Shenzhen Commission on Innovation and Technology Programs(JCYJ20180507181837997)China Postdoctoral Science Foundation(2018M633069 and 2019M652920)。
文摘Herbicide resistance in crop plants is valuable for integrated weed management in agriculture. Herbicide resistant rice, in particular, is important to management of weedy rice, a close relative of cultivated rice and a noxious weed prevalent in rice fields that remains challenging to farmers worldwide. Herbicide resistant plants can be obtained through transgenic approach or by mutagenesis of regular plant and screening of mutants with elevated resistance to herbicide. In this study, we conducted ethyl methyl sulfonate mutagenesis(EMS) to elite indica cultivar Huanghuazhan(HHZ) and screened for mutants resistant to imazapic, a herbicide that can inhibit the acetolactate synthase(ALS) in plants. We obtained three mutants of Os ALS gene that have not been reported previously in rice. One of the mutants, with Trp_(548) changed to Met(W_(548)M), was analyzed in more details in this study. This mutation had no negative effect on the plant physiology and morphology as well as rice yield. Compared with the imidazolinone-resistant mutant S_(627)N(Ser_(627) changed to Asn) that has been deployed for Clearfield rice development, W_(548)M mutant showed high levels of resistance to a broad spectrum of five families of ALSinhibiting herbicides, in addition to a higher level of resistance to herbicides of the imidazolinone family.The herbicide-resistance was stably inherited by crossing into other rice lines. Thus, the W_(548)M mutation provides a valuable resource for breeding of herbicide resistant rice and weed management.
文摘Adsorption of chloroacetanilide herbicides on homoionic montmorillonite, soil humic acid, and their mixtures was studied by coupling batch equilibration and FT IR analysis. Adsorption isotherms of acetochlor, alachlor, metolachlor and propachlor on Ca 2+ \|, Mg 2+ \|, Al 3+ \| and Fe 3+ \| saturated clays were well described by the Freundlich equation. Regardless of the type of exchange cations, K f decreased in the order of metolachlor > acetolachlor > alachlor > propachlor on the same clay. FT IR spectra showed that the carbonyl group of the herbicide molecule was involved in binding, probably via H bond with water molecules in the clay interlayer. The type and position of substitutions around the carbonyl group may have affected the electronegativity of oxygen, thus influencing the relative adsorption of these herbicides. For the same herbicide, adsorption on clay increased in the order of Mg 2+ <Ca 2+ <Al 3+ ≤Fe 3+ which coincided with the increasing acidity of homoionic clays. Acidity of cations may have affected the protonation of water, and thus the strength of H bond between the clay water and herbicide. Complexation of clay and humic acid resulted in less adsorption than that expected from independent adsorption by the individual constituents. The effect varied with herbicides, but the greatest decrease in adsorption occurred at a 60:40 clay to humic acid ratio for all the herbicides. Causes for the decreased adsorption need to be characterized to better understand adsorption mechanisms and predict adsorption from soil compositions.
基金Supported by the National Natural Science Foundation of China(No. 20562009)the Natural Science Foundation of Jiangxi Province, China(No. 0620041)+1 种基金the State Key Laboratory of the Chemo/Biosensing and Chemometrics of Hunan University, Chi-na(No. 2005-22)the Program for Changjiang Scholars and Innovative Research Team in Universities of China(No. IRT0540).
文摘Differential pulse stripping voltammetry method(DPSV) was applied to the determination of three herbicides, ametryn, cyanatryn, and dimethametryn. It was found that their voltammograms overlapped strongly, and it is difficult to determine these compounds individually from their mixtures. With the aid of chemometrics, classical least squares(CLS), principal component regression(PCR) and partial least squares(PLS), voltammogram resolution and quantitative analysis of the synthetic mixtures of the three compounds were successfully performed. The proposed method was also applied to the analysis of some real samples with satisfactory results.