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Physical and Chemical Properties of Pesticides and Other Contaminants: Volatilization, Adsorption, Environmental Distribution, and Reactivity
Published in James N. Seiber, Thomas M. Cahill, Pesticides, Organic Contaminants, and Pathogens in Air, 2022
James N. Seiber, Thomas M. Cahill
Chambers in the laboratory can also be used to study photoinitiated reactions using lamps that simulate sunlight. Trifluralin photodecomposed to multiple products in the lab in a vapor phase reactor equipped with an air sampler collecting vapors on a coated solid sorbent with limit of detection of less than 1 ng/m3 (Soderquist et al., 1975). The half-life of trifluralin was 47 minutes in the lab and between 21 and 193 min in the field, showing good agreement. Photolysis occurring at the soil surface followed by volatilization was the dominant occurrences. Trifluralin is stable in the dark (Woodrow et al., 1978).
Biochar and retention/efficacy of pesticides
Published in Johannes Lehmann, Stephen Joseph, Biochar for Environmental Management, 2015
Ellen R. Graber, Rai S. Kookana
The nature and extent of the effects of biochars on pesticides depends not only on the properties of biochars but also on the chemistry of the pesticide molecule. For example, Nag et al (2011) evaluated biochar produced from wheat straw at 450°C for its ability to influence efficacy of two commonly used herbicides (atrazine and trifluralin) with different mode of actions in controlling annual ryegrass (Lolium rigidum) in two contrasting soils. In terms of aqueous solubility, atrazine (35mg L-1) and trifluralin (0.022mg L-1) are very different. Atrazine affects photosynthesis by blocking electron flow that results after the leaf absorbs light energy, eventually leading to cell membrane disruption and leaf death. The dinitroaniline herbicides (e.g. trifluralin), on the other hand, inhibit root formation by interrupting mitosis in root tips in susceptible plants (Ashton and Crafts, 1981; Grover et al, 1997). Bioassays were conducted on soils amended with different rates of biochar (0, 0.5 and 1.0 per cent w/w) and herbicides (0, 0.5, 1, 2 and 4 times the recommended dosage). The addition of biochar to soil was found to increase ryegrass survival rate and above-ground biomass at most herbicide application rates. A dose-response analysis (Figure 23.5) showed that in the presence of 1 per cent biochar in soil, the value of GR50 (i.e. the dose required to reduce weed biomass by 50 per cent) for atrazine increased by 3.5 times in comparison to control soil (no biochar), whereas in the case of trifluralin GR50 increased only by a factor of 1.6. The difference between the two herbicides was ascribed to the greater mobility of atrazine and consequently greater contact with biochar. Since trifluralin acts via root contact, its reduced mobility meant that it had less contact with the biochar and hence was more plant available.
Student-Tested Laboratory Experiments
Published in Paul R. Loconto, Trace Environmental Quantitative Analysis, 2020
The persistence of trace residue levels of pesticides and herbicides in the environment has been cause for continued concern since the early 1960s, when it became apparent that these residues were detrimental to wildlife and possibly to human health. The benefits of using DDT gradually gave way to the increasing risk of continued use and eventually led to the banning of its use. Herbicides, however, do not appear to present such a high risk to the environment and continue to find widespread use. The chlorophenoxy acid herbicides are not directly amenable to GC and must first be chemically converted to their more volatile methyl esters prior to analysis using GC. Trifluralin or, according to International Union of Pure and Applied Chemistry (IUPAC) organic nomenclature, α,α,α-trifluoro-2, 6-dinitro-N,N-dipropyl-p-toluidine, is commonly one of the active pre-emergent herbicide ingredients in some lawn treatment formulations. Consider the molecular structures (shown below) of trifluralin and the internal standard 1,2,4-trichlorobenzene. The pre-emergent herbicide trifluralin will be extracted from herbicide treated lawn soil and quantitated against 1,2,4-trichlorobenzene in this experiment:With reference to the molecular structure for trifluralin, the presence of electronegative heteroatoms, such as fluorine combined with two nitro substituents on the benzene ring, would make the organic compound highly sensitive to the electron-capture detector (ECD), provided that the substance is sufficiently vaporizable and therefore amenable to GC. With a boiling point of 139°C, trifluralin is appropriately classified as a semivolatile, neutral organic compound (SVOC) and it is thus feasible to think that trifluralin could be isolated from a soil matrix by conventional sample preparation techniques such as liquid–liquid extraction (LLE) or perhaps by the more recently developed sample prep technique, reversed-phase solid-phase extraction (RP-SPE).
Effects of the herbicide trifluralin in the initial development of Piptadenia gonoacantha (Fabales: Fabaceae)
Published in International Journal of Phytoremediation, 2019
Naiane Maria Corrêa dos Santos, Wander Gladson Amaral, Fillipe Vieira de Araújo, Evander Alves Ferreira, Bárbara Monteiro de Castro e Castro, José Cola Zanuncio, Israel Marinho Pereira, José Barbosa dos Santos
The chemical control of grasses in forest crops is a fast, efficient, and economical method and, therefore, widely used (Mueller et al. 2014). The herbicide glyphosate is not selective to forest crops and does not leave residues in the soil to control grasses in succession (Doust et al. 2006). Herbicides selective to forest species have the potential to control grasses instead of glyphosate. Trifluralin, a pre-emergent graminicide herbicide with high adsorption and low mobility in the soil, is of the dinitroaniline chemical group and inhibits the mitotic cell division process (Fernandes et al. 2007). Forest species tolerance to trifluralin is poorly understood, increasing the need of evaluating its impact on plants, especially in restoration areas (Gianessi 2013).