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Physical Properties of Agrochemicals
Published in John H. Montgomery, Thomas Roy Crompton, Environmental Chemicals Desk Reference, 2017
John H. Montgomery, Thomas Roy Crompton
The half-lives for simazine in soil incubated in the laboratory under aerobic conditions ranged from 27 to 231 days (Zimdahl et al., 1970; Beynon et al., 1972; |Walker, 1976, 1976a). In field soils, the disappearance half-lives were lower and ranged from 11 to 91 days (Roadhouse and Birk, 1961; Clay, 1973; Joshi and Datta, 1975; Marriage et al., 1975).
Nanoscale zero-valent iron for remediation of toxicants and wastewater treatment
Published in Environmental Technology Reviews, 2023
Paraquat is among the most important herbicides of the bipyridyl group used for agricultural practices. Pumice or diatomite-supported nZVI composites were used to remove contaminants from aqueous solutions. Both D-nZVI and P-nZVI nanoparticles were workable at a pH of 3.74, and their results found that the removal efficiencies of the D-nZVI and P-nZVI were 92.76 and 85.28%, respectively. Similarly, the maximum adsorption capacities of D-nZVI and P-nZVI were 161.3 and 169.49 mg/g, respectively [144]. Simazine, a typical triazine-derivative herbicide, was degraded using diatomite-supported nZVI (D-nZVI) in an aqueous solution. The study was conducted without the presence of O3 or H2O2 during the removal of the partially water-soluble and toxic herbicide simazine. The removal percentage was 80% under acidic conditions (pH = 2.35), with D-nZVI doses of 2 g/L and simazine concentrations of 4 ppm. The supported nZVI showed better performance than the bare nZVI. Furthermore, the adsorption capacity of simazine on diatomite was low; hence, the degradation was carried out in the nZVI than the supporting material [145].
Pesticide removal from drinking water sources by adsorption: a review
Published in Environmental Technology Reviews, 2019
Stephanie Cosgrove, Bruce Jefferson, Peter Jarvis
Most pesticides have a log Kow below 3 which is the reason why many pesticides persist in water sources [116]. Quinmerac and clopyralid are both very polar compounds, with log Kow values of −1.41 and −2.63 respectively and so are expected to be some of the pesticides most difficult to remove from water by adsorption. Sorbents that have partially charged surfaces are likely to be more successful in the removal of these compounds due to their more polar nature. In principle, metaldehyde should be easier to remove by adsorption compared to clopyralid and quinmerac due to its relatively higher log Koc (2.38) and log Kow (0.12) values. However, this has not been the case as seen by the high frequency of compliance failures it has caused. This may be because of metaldehyde’s stable ring structure or because metaldehyde’s chemical structure only contains single bonds, it can change conformation and polarity, and therefore its adsorption is not constant [117]. The development of new phenolic based activated carbons with high surface areas may help to capture metaldehyde. Metazachlor has a lower log Kow value of 2.49 so is less polar than metaldehyde, clopyralid and quinmerac and so should be relatively easier to remove from water. It does, however, have a low Koc value (1.73) that is in a similar range to other pesticides such as simazine and atrazine. Although metazachlor has not itself caused many compliance failures its Koc and Kow are similar to other pesticides known to have been problematic in the past including atrazine and carbofuran (Figure 6).
Physiological and molecular responses of pearl millet seedling to atrazine stress
Published in International Journal of Phytoremediation, 2018
Kehinde O. Erinle, Zhao Jiang, Bingbing Ma, Khalil Ur-Rehman, Andleeb Shahla, Ying Zhang
Atrazine is a common selective triazine herbicide used to control broadleaf and grassy weeds. According to the US EPA (2003), the half-life of atrazine in soil ranges from 13 to 261 days (Erinle et al. 2016a); atrazine has been reported to have a pKa value of 1.61 at 25°C (Plust et al. 1981), and solubility increased slowly with temperature below 35 °C in ethanol + water, but above 35 °C in 1-propanol + water (Jia et al. 2013). Application of atrazine in pearl millet cultivation has long been documented. In the reports of Tomer and Singh (1973) and Panchal and Sastry (1974), application of atrazine before weed emergence was noted to increase pearl millet yield by 28% and 100%, while Jain et al. (1971) recorded 150% increase in yield. Weller (1994) and de Carvalho Dias et al. (2015) reported pearl millet tolerance to atrazine. However, the ability of pearl millet (as Pennisetum) to degrade triazine herbicides at the rhizosphere level, alone or in combination with soil isolated microorganisms, has also been reported (Singh et al. 2004). Pennisetum plants were used to clean up a long-term (approx. 15 years) atrazine-contaminated soil. At 80 days, atrazine and simazine concentrations in the rhizosphere of the plants decreased to 55% and 48%, respectively, of the original level in the rhizosphere soil. However, Zhang et al. (2014a) reported the plant–microbe joint interaction (with Arthrobacter sp. DNS10) degraded 98.10% of the atrazine after a 30-day experiment period).