Atrazine solubility

There are at least 22 chemical families of organic herbicides. Even a cursory treatment of the chemistry of these materials would be extensive. Herbicides of limited toxicity (Treflan, Atrazine) as well as extremely toxic ones (Paraquat. Dinoseb) are in use in many parts of the world. They range from water soluble to insoluble. The detailed chemistry of each should be determined prior to handling. 

Ureides (e.g., diuron, linuron) and triazines (e.g., atrazine, simazine, ametryne) all act as inhibitors of photosynthesis and are applied to soil (see Figure 14.1 for structures). They are toxic to seedling weeds, which they can absorb from the soil. Some of them (e.g., simazine) have very low water solubility and, consequently, are persistent and relatively immobile in soil (see Chapter 4, Section 4.3, which also mentions the question of depth selection when these soil-acting herbicides are used for selective weed control). 

Estuarine fungi contribute substantially to plant detritus due to their abundance and potential for degradation. Fungi are known to accumulate soluble atrazine from seawater through sorption, and release up to 2.2% as hydroxyatrazine and other atrazine metabolites another 4.6% is more tightly associated and less available to the external environment. The combined processes result in atrazine accumulation, and may contribute to its transport and redistribution through the estuary (Schocken and Speedie 1982, 1984). 

Foster, T.S. and S.U. Khan. 1976. Metabolism of atrazine by the chicken. Jour. Agric. Food Chem. 24 566-570. Foster, T.S., S.U. Khan, and M.H. Akhtar. 1980. Metabolism of deethylatrazine, deisopropylatrazine, and hydroxy atrazine by the soluble fraction (105000 g) from goose liver homogenates. Jour. Agric. Food Chem. 28 1083-1085. 

Pillai, C.G.P., J.D. Weete, and D.E. Davis. 1977. Metabolism of atrazine by Spartina altemiflora. I. Chloroform-soluble metabolites. Jour. Agric. Food Chem. 25 852-855. 

The LLE of relatively polar and water-soluble organic compounds is, in general, difficult. The recovery obtained from 11 of water with dichloromethane is 90% for Atrazine but lower for its more polar, degradation products, i.e., di-isopropyl- (16%), di-ethyl- (46%),andhydroxy-atrazine (46%). By carrying out LLE with a mixture of dichloromethane and ethyl acetate with 0.2 mol/1 ammonium formate, the extraction recoveries for the three degradation products were increased to 62 %, 87 %, and 65 %, respectively [437]. 

The persistence (half-life) of atrazine in the subsurface is governed by chemically and biologically mediated transformations. Because the solubility of atrazine is relatively high ( 30mg/L) compared to its toxicity level in water (5 Lig/L), atrazine has become a hazard to groundwater quality. Atrazine has been detected in groundwater more than any other crop protection chemical two examples of atrazine persistence-transformation in aquifer environments are discussed next. 

Atrazlne. Atrazine is a chlorinated, a-triazine herhicide. Its water solubility is 33 npm (18), its vapor pressure is 3 X 10 torr (19), and H < 10 atm-i /mole. The pK of atrazlne is 1.68 (40). Kqp values of 51 and 214 have been reported (19,20) and the mean of 56 soils was reported to be 163+80 (41). The Kjj of atrazlne varies between 1 and 8 in certain soils, and seems to be dependent on the cations present (42). Kj values of 0.40-0.46 were also recently reported for aquifer sands in Nebraska (43). Atrazlne is in Helling s mobility class 3, which is the intermediate mobility class (10). (Class 5 is the most mobile, and class 1 is immobile.)... 

The first work in this field was probably that of Piletsky et al. [84] that described a competitive FILA for the analysis of triazine using the fluorescent derivative 5-[(4,6-dichlorotriazin-2-yl)amino]fluorescein. The fluorescence of the supernatant after incubation was proportional to the triazine concentration and the assay was selective to triazine over atrazine and simazine. The same fluorescent triazine derivative was applied to competitive assays using atrazine-imprinted films [70]. To this end an oxidative polymerization was performed in the presence of the template, the monomer(s) 3-thiopheneboronic acid (TBA) or mixtures of 3-amino-phenylboronic acid (APBA) and TBA (10 1) in ethanol-water (1 1 v/v) where the template is more soluble. The polymers were grafted onto the surface of polystyrene microplates. The poly-TBA polymers yielded a detection limit of 8 pM atrazine whereas for the poly-TBA-APBA plates it was lowered to 0.7 pM after 5 h of incubation. However, a 10-20% decrease in the polymer affinity was observed after 2 months. 

Some currently used pesticides that are intermediate in water solubility and persistence can reach fairly high concentrations in water, sediment, and biota, in areas of high use. Pesticides that enter the lakes—whether by direct discharge along the shores, by runoff through tributaries, or from the atmosphere—are retained in the system and become more concentrated over time. For example, atrazine is detected widely in streams in the midwestern USA at concentrations in the range of several hundred ng/L to several tens of xg/L [12]. The half-life of atrazine in deeper lakes was estimated to be greater than 10 years. 

In comparison with OC pesticides, the current-use OP and carbamate pesticides are relatively more water soluble and less bioaccumulative. However, because of the high volume of their usage, there is a potential for these compounds to be present in the environment. Herbicides such as atrazine, metolachlor, and alachlor have been surveyed in the Great Lakes [59] and along the margins of fields, streams, and tributaries within the Great Lakes Basin [5,60]. 

Although atrazine has a soil half-life of 30-90 days, transport out of this zone into receiving waters leads to longer half-lives [101]. For pesticides with high water solubilities, such as atrazine, tributary inputs can be a major source, and environmental response to sources is controlled by long hydraulic residence times and slow transformation rates. Despite the fact that only 1% of the applied atrazine is lost by transport to rivers and lakes, and another 1% by aerial transport, the large quantities applied, together with efficient hydraulic transport result in accumulation in aquatic systems. 

Talbert and Fletchall (1965) found that increasing temperature resulted in decreased sorption of simazine and atrazine. Similarly, Santana-Casiano and Gonzalez-Davila (1992) found that the sorption of lindane to chitin decreased as temperature increased from 5 to 45°C. In addition, sorption-desorption hysteresis, observed at lower temperatures, was reduced dramatically at the highest temperature. However, Chiou et al. (1979) observed decreased aqueous solubility and increased sorption at higher temperature for 1,1,1-trichloroethane. 

Figure 16.28. (a) Sorption envelopes for atrazine (AT 0.14 mmol liter1) on oxisol HA and FA, both at a concentration of 600 mg liter-1, and (b) pH dependence of AT solubility in water as detected by UV-vis spectroscopy, monitoring the absorption band at 223 nm. The initial concentration of the saturated aqueous solution of atrazine was 0.28 mmol liter-1 (Martin-Neto et al., 2001). 

In a study designed to determine the mode of action of atrazine in higher plants, Shimabukuro and Swanson (1969) concluded that atrazine inhibits the Hill reaction and its noncyclic phosphorylation, while being ineffective against cyclic photophosphorylation. Atrazine readily penetrated the chloroplast of resistant as well as susceptible plants. In tolerant plants such as sorghum, the metabolism of atrazine was postulated to occur outside the chloroplasts to form water-soluble and insoluble residues that reduced the concentration of photosynthetic inhibitors in the chloroplasts. 

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