Simazine studies

These high levels were sporadic and transitory. However, some of them were high enough to have caused phytotoxicity, and more work needs to be done to establish whether herbicides are having adverse effects upon populations of aquatic plants in areas highlighted in this study. It should also be borne in mind that there may have been additive or synergistic effects caused by the combinations of herbicides found in these samples. For example, urea herbicides such as diuron and chlortoluron act upon photosynthesis by a common mechanism, so it seems likely that any effects upon aquatic plants will be additive. Similarly, simazine and atrazine share a common mechanism of action. 

Supercritical fluid extraction (SFE) is generally used for the extraction of selected analytes from solid sample matrices, but applications have been reported for aqueous samples. In one study, recoveries of 87-100% were obtained for simazine, propazine, and trietazine at the 0.05 ug mL concentration level using methanol-modified CO2 (10%, v/v) to extract the analytes, previously preconcentrated on a C-18 Empore extraction disk. The analysis was performed using LC/UV detection. Freeze-dried water samples were subjected to SFE for atrazine and simazine, and the optimum recoveries were obtained using the mildest conditions studied (50 °C, 20 MPa, and 30 mL of CO2). In some cases when using LEE and LC analysis, co-extracted humic substances created interference for the more polar metabolites when compared with SFE for the preparation of the same water sample. ... 

In another study, catfish samples were homogenized in ethyl acetate, and the residues were partitioned into acetonitrile and petroleum ether, subjected to C-18 SPE purification, and analyzed using LC/UV detection. "" Quantitative recoveries were obtained for atrazine, simazine, and propazine in the 12.5-100 lagkg concentration range. 

Pesticides contaminate not only surface water, but also ground water and aquifers. By 1990 in the USSR, 15% of all pesticides used were detected in underground water [29]. Pesticides were detected in 86% of samples of underground water in Ukraine in 1986-87 (including DDT and its metabolites, HCH, dimethoate, phosalone, methyl parathion, malathion, trichlorfon, simazin, atrazine, and prometrin). In actual fact, the number of pesticides was apparently larger, but the laboratory was able to determine the content of only 30 of the 200 pesticides used at that time in Ukraine [29]. In the 1960s, in the Tashkent and Andizhan oblasts of Uzbekistan, the methylmercaptophos content in the water of studied well shafts was, by clearly underestimated data, 0.03 mg/l (MPC was 0.01 mg/l), of DDT was 0.6 mg/l (MPC was 0.1 mg/ I), and of HCH was 0.41 mg/l (MPC was 0.02 mg/l) [A49]. 

In several AT studies, pesticide levels in the Ebro were found to be high. Hildebrandt et al. [50] found a homogeneous contamination pattern from atrazine (and also from simazine from May 2000) in intensive Rioja cultivation areas throughout the Ebro. Nearer to the delta, Barata et al. [72] found high levels of bentazone, methyl-4-chlorophenoxyacetic acid, propanil, molinate and fenitrothion in water, while Kuster et al. [71] found low concentration levels of atrazine and simazine at the delta, but high levels of other pesticides used in rice cultivation. Importantly, Hildebrandt et al. [50] found that levels of pesticides in groundwater... 

Cotterill [100] studied the effect of ammonium nitrate fertilizer on the electron capture or nitrogen specific gas chromatographic determination of Triazine plus other types of herbicide (Atrazine(2-chloro-4-ethylamino-6-isopropylamino, 1,3,5 triazine), Simazine (2-chloro-4.6 bis ethyl amino 1,3,5 triazine), Linuron (3,4,-chlorophenyl-l-methoxy-l-methyl urea), Metribuzin, Triallate and Phorate) residues in soil. 

Pelizzetti et al. (1990) studied the aqueous photocatalytic degradation of simazine and other 5-triazines (ppb level) using simulated sunlight (k >340 nm) and titanium dioxide as a photocatalyst. Simazine rapidly degraded forming cyanuric acid, nitrates and other intermediate... 

Another example of the potential pernicious effects of pesticides upon human health is the study conducted at the University of Colorado where researchers have found that higher concentrations of four pesticides - atrazine, simazine, alachlor and metolachlor - in groundwater are significantly associated with higher levels of Parkinson disease. For every 10 pg/L increase of pesticide levels in the drinking water, they found that the risk for Parkinson disease increased by 3% and their water samples had pesticide concentrations ranging from 0.0005 to 20 pg/L [38]. 

GS-13529, terbuthylazine A chlorotriazine similar to atrazine and simazine, terbuthylazine was first introduced to the scientific community in 1966. Terbuthylazine also provided broad-spectrum weed control in com. Studies comparing efficacy showed that generally atrazine was more effective than terbuthylazine on both broadleaf and grassy weeds. Since terbuthylazine was less efficacious than atrazine in weed control trials conducted in the United States in the late 1960s, it was not commercially developed for com in the United States. However, development for use in corn and vines continued for Europe and other countries where the weed control needs differed and the weed control differences between atrazine and terbuthylazine were not limiting. 

The triazine herbicides have revolutionized agricultural production of corn and more than 40 other crops. The yield increases, less labor-intensive production, and use for erosion control in conservation tillage are all benefits of the tri-azines, especially atrazine and simazine. Registered since the late 1950s, atrazine is still a mainstay of corn production and likely the most studied herbicide by regulatory agencies. 

LeBaron and Fertig (1961, 1962) and Schirman and Buchholtz (1966) found that while simazine and some of the other herbicides would kill the above-ground quackgrass vegetation, they had very little effect on the underground rhizomes, which were the real source of survival and reinfestation. Of all the herbicides studied, only atrazine was found to adequately control the underground rhizomes of quackgrass. 

Roth, W. (1957). Comparative study of the reaction of simazine, a herbicide, on maize and wheat. Compt. Rend, 245 942-944. 

During late 1994, the United States Environmental Protection Agency (USEPA) published a public document (PD-1) relative to the use of triazine herbicides by American farmers. In doing so, they placed atrazine and simazine in Special Review. USEPA s PD-1 triggered a benefits study of unprecedented proportions on the following issues benefits of atrazine and simazine use economic and biological impact of the loss of these products feasibility and efficacy of alternatives environmental benefits associated with atrazine and simazine use best management practices and comparative performance of alternatives. 

Simazine was the main product studied in early research on the triazines for weed control in tree fruits and vineyards (Doll, 1960 Larson and Ries, 1960). On mature grapevines in a deep, fine, and sandy loam soil, no differences in crop tolerance were observed between simazine and atrazine (Leonard and Lider, 1961). However, subsequent studies indicated that grapevines were more tolerant to simazine than to atrazine (Lange et al., 1969a). Prometryn was intermediate between the two in terms of crop tolerance (Lange et al., 1969a). 

Micropropagated raspberry is less tolerant to simazine, probably because of the shallow roots picking up more herbicide than the deeper rooting cuttings (Neal et al, 1990). When simazine was used in a New York study, weed control was excellent. However, with rainfall plus supplemental irrigation, there was less plant establishment and growth in herbicide-treated vines compared to mulched plants (Trinka and Pritts, 1992). It was determined that mulching provided a more uniform microclimate (moisture) than the plots with no weeds or cover. 

Once in the soil, deactivation is related to kind and quantity of clay and to organic matter content (Upchurch and Mason 1962 Day et al, 1968 Weber et al, 1969). Burnside et al. (1961) reported that simazine remains in the upper few centimeters of soil and breaks down readily at high temperatures and low pH. Holly and Roberts (1963) emphasized the variability in the breakdown of simazine. In one study, simazine residue in soil was evaluated 1 year after treatment, where the half-life was 59 days. However, after 12 years of treatment, the half-life was 46 days, a slight but significant enhanced degradation rate (Rouchard et al, 2000). 

---