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Wastewater Treatment
Published in Suresh C. Ameta, Rakshit Ameta, Garima Ameta, Sonochemistry, 2018
Arpita Pandey, Arpita Paliwal, Rakshit Ameta
The herbicide (4-chloro-2-methylphenoxy) acetic acid (MCPA) is normally used in paddy fields and, therefore, wastewater may be contaminated. Ultrasonic degradation of aqueous solutions of MCPA was investigated with 500 kHz under argon atmosphere by monitoring liberation of chloride ion, total organic carbon (TOC) and by-product production. Kojima et al. (2005) reported the degradation of MCPA under sonication in the presence of nitrogen, air, oxygen, argon, and argon/air (60/40%v/v). The 4-chloro-2-methylphenoxy acetic acid was fully decomposed after 180 min sonication with a power of 21 W, but 60% of the TOC remained in solution even after 6 h. The rate of decomposition of MCPA was found to be greater in oxygen-enriched atmospheres as radical production was more there, but dechlorination and TOC removal rates were relatively higher with argon.
Historical and Current Uses of Pesticides
Published in James N. Seiber, Thomas M. Cahill, Pesticides, Organic Contaminants, and Pathogens in Air, 2022
James N. Seiber, Thomas M. Cahill
Popular synthetic herbicides began with the introduction of phenoxy herbicides 2-methyl-4-chlorophenoxyacetic acid (MCPA), 2,4-dichlorophenoxyacetic acid (2,4-D), and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) (Figure 2.6). The latter two are components of “Agent Orange” used by the U.S. military as a defoliant during the Vietnam War. Agent Orange is on the “dirty dozen” list of the World Health Organization as off-limits for nations worldwide because it is contaminated with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD; “dioxin”)—one of the most toxic synthetic chemicals known to humans (Figure 2.7). TCDD is still seen in air samples collected near municipal dump sites and particularly around incinerators (Shibamoto et al., 2007).
Overview of Occurrence and Distribution of Pesticides in Relation to Use
Published in Steven J. Larson, Paul D. Capel, Michael S. Majewski, Pesticides in Surface Waters, 2019
Steven J. Larson, Paul D. Capel, Michael S. Majewski
The only phenoxy acid herbicides with significant current agricultural use in the United States are 2,4-D, esters of 2,4-D, and MCPA (Table 3.1). During the 1960’s and 1970’s, 2,4,5-T also was used agriculturally. Silvex (2,4,5-TP) was used in smaller amounts before 1984, when its use was restricted in the United States. During 1989–1991, 2,4-D ranked fifth among agricultural herbicides and MCPA ranked seventeenth in terms of mass applied. In addition, the USEPA estimates non-agricultural use of 2,4-D to be 38 to 87 percent of agricultural use (Gianessi and Puffer, 1991). If the high estimate for non-agricultural use is correct, total 2,4-D use ranked second among all herbicides during 1988–1991. The total amount of phenoxy compounds used in United States agriculture has remained nearly stable over the last two decades, although their proportion of the total herbicide use has dropped as use of triazine and acetanilide herbicides has increased (Table 3.2). The phenoxy compound 2,4-D is used primarily on pasture land, hay, wheat, com, and barley, with heaviest use in the plains states, the Midwest, and the Southwest (Figure 3.10). MCPA is used primarily on wheat, barley, oats, and rice, with heaviest use in the northern plains states and California (Figure 3.13). Phenoxy compounds, primarily 2.4-D and MCPP, are also used heavily for lawn care in urban areas by both homeowners and professional applicators. These two compounds were the herbicides used most often by homeowners, according to a 1990 survey (Whitmore and others, 1992). Occurrence of these compounds in surface waters as a result of application in urban areas is discussed in Sections 4.1 and 5.3.
Synthesis of Cr3+-doped TiO2 nanoparticles: characterization and evaluation of their visible photocatalytic performance and stability
Published in Environmental Technology, 2019
Sandra Yadira Mendiola-Alvarez, Jorge Luis Guzmán-Mar, Gemma Turnes-Palomino, Fernando Maya-Alejandro, Adolfo Caballero-Quintero, Aracely Hernández-Ramírez, Laura Hinojosa-Reyes
On the above grounds, a systematic study was undertaken, in which a new facile route for the synthesis of Cr3+-doped titanium dioxide using a microwave-assisted sol–gel method was reported. The prepared catalyst was characterized by X-ray diffraction (XRD), ultraviolet–visible diffuse reflectance spectroscopy (UV–VIS DRS), N2 adsorption–desorption analysis, Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), photoluminescence (PL) spectroscopy, X-ray photoelectron spectroscopy (XPS) and zeta potential measurements. For photocatalytic evaluation activity, the (4-chloro-2-methylphenoxy)acetic acid (MCPA) was chosen as a model pollutant. The MCPA, a phenoxyacetic acid herbicide, is highly water soluble, highly mobile and can leach from the soil exhibiting a potential risk for groundwater contamination [23,24]. The photocatalytic activity of the Cr3+-doped TiO2 was assessed by degradation of MCPA aqueous solution under visible radiation and was subsequently compared with the performances of the bare TiO2 and Degussa P25. Moreover, the stability and recyclability of the Cr3+-doped TiO2 catalyst for MCPA degradation were evaluated.
The effects of syringic acid on the properties of MCPA-contaminated soil and the growth of two cucurbit species
Published in International Journal of Phytoremediation, 2022
Elżbieta Mierzejewska, Wojciech Tołoczko, Magdalena Urbaniak
One of the most commonly-used groups of plant protection agents are herbicides based on phenoxy-phytohormones i.e. MCPA (2-methyl-4-chlorophenoxyacetic acid); they are commonly used to protect wheat fields due to their capability to selectively control annual and perennial weeds (Smith et al.1994; Horvat et al.2003). Nearly 6500 tons of phenoxy herbicides was sold and used in the fields in the EU in 2016 (Eurostat) resulting in contamination of the soil and contributing to the deterioration of surface- and groundwater ecosystems (Wei et al.2000; Sarikaya and Yilmaz 2003; Ignatowicz and Struk-Sokołowska 2004; Pazmiño et al.2011; Podolska 2014). Although MCPA has a relatively short half-life in slightly alkaline and slightly acidic soils, its extensive use and mobile character enhances its transport and deposition, and the persistence of its residues in environmental compartments represents cause for concern. The degree of sorption of MCPA is dependent on the temperature, fertilization and pH of the soil, and its organic matter content (Horvat et al.2003; Paszko et al.2016). Approximately 59% of the area of Europe is located in a temperate climate (Food and Agriculture Organization of the United Nations 2001), and is hence characterized by low winter temperatures, depleted soil organic carbon content and acidic pH (approximately 36% of grazing land and 26% of agricultural land) (Fabian et al.2014), making it especially prone to contamination (Mcghee and Burns 1995; Paszko et al.2016). Consequently, the identification of nature-based methods which can be used to sustainably restore and manage ecosystems and enhance the process of MCPA removal from environmental matrices is of particular interest.