胺苯黄隆的除草效果与残留药害

在小区试验条件下，对胺苯黄隆的除草效果进行了观察，并对其在移栽油菜上的药害和对后茬水稻的残留危害作了描述。结果表明，胺苯黄隆有较高的除草效果。在使用剂量超过１５ｇ每公顷（有效成份计，下同）时，对当季油菜的药害和后茬水稻的二次药害非常明显，可造成油菜籽产量下降３０．９６％～５７．８１％，并可使下茬水稻减产９．３４％～２３．２０％。     

Detectability of phenoxy herbicides by chlorophyll fluorescence

Abstract

Trace amounts of 2,4‐D ‐ which does not cause visible damage in plant ‐ are detectable in plant leaves by chlorophyll fluorescence regeneration in two ways. (I) In illuminated leaves the level of first and second fluorescence peak differ in treated and untreated leaves. (2) By taking buffer solution (pH=8.6) in dark‐adapted leaves under vacuum, the first, second and the other fluorescence decrease levels differ in untreated and 2,4‐D or MCPA treated leaves.     

Procedure for the determination of 2,4‐D and dicamba in inhalation,dermal, hand‐wash,and urine samples from spray applicators

Abstract

Analytical procedures for the simultaneous determination of residues of 2,4‐D and dicamba from polyurethane foam plug air samplers, ethylene glycol impregnated glass‐fiber filter paper dermal samplers, 1% sodium bicarbonate hand wash solution, and urine are presented. Residues were derivatized with diazomethane and quantitated using electron capture gas chromatography. Recoveries were greater than 80% at the limit of detection in all substrates. The limits of detection for both herbicides were 0.1 μg/foam plug and 0.5 μg/filter paper, and in the urine, 1.7 μg/100 mL and 5.0 μg/100 mL for dicamba and 2,4‐D, respectively.     

ISOPROTURON DEGRADATION AS AFFECTED BY THE GROWTH OF TWO ALGAL SPECIES AT DIFFERENT CONCENTRATIONS AND pH VALUES

Metabolism of [¹⁴C-u-phenyl]isoproturon [3-(4-isopropylphenyl)-1,1-dimethylurea] by two soil and freshwater microorganisms, green alga Chlorella kesslerei and cyanobacterium Anabaena inaequalis, was studied as a function of pH, pesticide concentration, and incubation time. Metabolized isoproturon, in the media, ranged from 0% (Chlorella at pH 5.5 after 1 d) to 22% (Anabaena at pH 5.5 after 10 d). Twenty-five percent faster degradation of isoproturon by Anabaena occurred at pH 5.5 versus pH 7.5, when measured over 10 d. Increased ¹⁴C incorporation into tissue, with time and at lower pH, was due mainly to bioaccumulation of [¹⁴C]isoproturon and/or its metabolites in the cells. Metabolic degradation resulted in four identifiable (by TLC) metabolites. Based on this, a degradation pathway is proposed, involving mono- and di-N-demethylation, hydroxylation of the isopropyl moiety, and hydrolysis to 4-isopropylaniline. Similarity in the metabolites produced suggests that the enzyme systems responsible for metabolizing isoproturon are almost identical in both photosynthetic micro-algae.     

Teratogenicity of bifenox and nitrofen in rodents

Abstract

The teratogenicity of the diphenyl ether herbicide bifenox [2,4‐dichlorophenyl 3'‐carboxymethyl‐4'‐nitrophenyl ether] was compared to that of nitrofen [2,4‐dichlorophenyl 4'‐nitrophenyl ether] in rats and in mice. Neither compound increased prenatal mortality in mice. Because nitrofen causes both malformations that are compatible with survival to weaning and a high incidence of perinatal (but not of fetal) mortality, emphasis was placed on postnatal parameters of bifenox toxicity. In rats, bifenox caused a low incidence of “bloody tears”;, but it did not decrease survival to term or to weaning in rats or mice, and did not reduce Harderian gland weight in mice. Because the weight of the Harderian glands is a more objective measure of their status than is the presence of an eye discharge, it is concluded that bifenox is not teratogenic at the levels administered. Nitrofen decreased litter size, pup weight, and Harderian gland weight in mice.     

Photooxidative removal of the herbicide Acid Blue 9 in the presence of hydrogen peroxide: modeling of the reaction for evaluation of electrical energy per order (EEO)

The present work deals with photooxidative removal of the herbicide, Acid Blue 9 (AB9), in water in the presence of hydrogen peroxide (H₂O₂) under UV light illumination (30 W). The influence of the basic operational parameters such as amount of H₂O₂, irradiation time and initial concentration of AB9 on the photodegradation efficiency of the herbicide was investigated. The degradation rate of AB9 was not appreciably high when the photolysis was carried out in the absence of H₂O₂ and it was negligible in the absence of UV light. The photooxidative removal of the herbicide was found to follow pseudo-first-order kinetic, and hence the figure-of-merit electrical energy per order (E_Eo) was considered appropriate for estimating the electrical energy efficiency. A mathematical relation between the apparent reaction rate constant and H₂O₂ used was applied for prediction of the electricity consumption in the photooxidative removal of AB9. The results indicated that this kinetic model, based on the initial rates of degradation, provided good prediction of the E_Eo values for a variety of conditions. The results also indicated that the UV/H₂O₂ process was appropriate as the effective treatment method for removal of AB9 from the contaminated wastewater.     

Nonformal environmental education: a case study with farmers in a town of the South Minas Gerais state,Brazil

Brazil is a central place in the international agricultural markets and this fact has been demanding environmentally oriented agricultural practices by Brazilian farmers and professionals involved in the agricultural market chain. A concise and structured questionnaire was applied to obtain the environmental perception of a group of Brazilian farmers in a town of the south Minas Gerais state, using herbicides as the topic for a case study. A highly variable opinion about taking the environment into account when choosing the most appropriate herbicide was found. Anyway, efficacy has been indicated as the most important factor when choosing an herbicide, followed by the environment and price. The outcomes from the questionnaires, i.e. the insufficient conception and importance given to environment when choosing the herbicide, motivated the creation of a teaching-learning model for the nonformal environmental education using the concept of socio-ecological resilience. This routine puts in practice the resilience thinking currently invoked as a major tool to achieve the conservation of the socio-ecological system, as well as it is complimentary to the outcome-oriented optimization for conservation theory. For the case study about farmers and the use of herbicides, we conclude that a complex reasoning and, ultimately, pro-environmental actions can be improved after experiencing the recommended model for environmental education.     

Fast determination of phenoxy acid herbicides in carrots and apples using liquid chromatography coupled triple quadrupole mass spectrometry

A fast, simple and inexpensive method has been developed for the analysis of phenoxy acid herbicides: 2,4-dichlorophenoxyacetic acid (2,4-D), 4-chloro-2-methylphenoxyacetic acid (MCPA), 2-(4-chloro-o-tolyloxy)propionic acid (MCPP), 2-(4-aryloxyphenoxy)propionic acid (Fluazifop) and 2-(4-aryloxyphenoxy)propionic acid (Haloxyfop) in carrots and apples by liquid chromatography coupled to triple quadrupole mass spectrometry (LC/MS/MS). The compounds were analyzed by QuEChERS (quick, easy, cheap, effective, rugged, safe) methodology without cleanup.

The recoveries were performed at two spiked levels (0.05 and 0.5 mg/kg) for both matrices with six replicates for each level. The mean recoveries ranged from 70–92% for both apples and carrots. The precision of the method expressed as relative standard deviation (RSD%) was found to be in the range 3–15%. For all compounds, good linearity (r² > 0.99) was obtained over the range of concentration from 0.05 μ g/mL to 0.5 μ g/mL, corresponding to the pesticide concentrations of 0.05 mg/kg and 0.5 mg/kg, respectively. The determination limits (LOQs) ranged from 0.01 ng/mL to 1.3 ng/mL in solvent, whereas, the LOQs calculated in matrix ranged from 0.05 ng/g to 21.0 ng/g for apples and from 0.06 ng/g to 10.2 ng/g for carrots. The developed methodology combines the advantages of both QuEChERS and LC/MS/MS producing a very rapid, sensitive and cheap method useful for the routine analytical laboratories.     

HERBICIDES AND DEGRADATES IN SHALLOW AQUIFERS OF ILLINOIS: SPATIAL AND TEMPORAL TRENDS1

ABSTRACT: During the fall of 2000, the occurrence was examined of 16 herbicides and 13 herbicide degradates in samples from 55 wells in shallow aquifers underlying grain producing regions of Illinois. Herbicide compounds with concentrations above 0.05 μg/L were detected in 56 percent of the samples. No concentrations exceeded regulatory drinking water standards. The six most frequently detected compounds were degradates. Water age was an important factor in determining vulnerability of ground water to transport of herbicide compounds. Unconsolidated aquifers, which were indicated to generally contain younger ground water than bedrock aquifers, had a higher occurrence of herbicides (73 percent of samples) than bedrock aquifers (22 percent). Temporal analysis to determine if changes in concentrations of selected herbicides and degradates could be observed over a near decadal period indicated a decrease in detection frequency (25 to 18 percent) between samplings in 1991 and 2000. Over this period, significant differences in concentrations were observed for atrazine (decrease) and total acetochlor (increase). The increase in acetochlor compound concentrations corresponds to an increase in acetochlor use during the study period, while the decrease in atrazine concentrations corresponds to relatively consistent use of atrazine. Changes in frequency of herbicide detection and concentration do not appear related to changes in land use near sampled wells.     

Spiking solvent, humidity and their impact on 2,4-D and 2,4-DCP extractability from high humic matter content soils

The 2,4-dichlorophenoxyacetic acid (2,4-D) is a hormone-like herbicide widely used in agriculture. Although its half life in soil is approximately two weeks, the thousands of tons introduced in the environment every year represent a risk for human health and the environment. Considering the toxic properties of this compound and its degradation products, it is important to assess and monitor the 2,4-D residues in agricultural soils. Furthermore, experiments of phyto/bioremediation are carried out to find economic and environmental friendly tools to restore the polluted soils. Accordingly, it is essential to accurately measure the amount of 2,4-D and its metabolites in soils. There is evidence that 2,4-D extraction from soil samples seriously depends on the physical and chemical properties of the soil, especially in those soils with high content of humic acids. The aim of this work was to assess the variables that influence the recovery and subsequent analysis of 2,4-D and its main metabolite (2,4-dichlorophenol) from those soils samples. The results showed that the recovery efficiency depends on the solvent and method used for the extraction, the amount and kind of solvent used for dissolving the herbicide and the soil water content at the moment of spiking. An optimized protocol for the extraction and quantification of 2,4-D and its main metabolite from soil samples is presented.