Atrazine loam study

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). 

Tasli, S., P. Ravanel, M. Tissut, J.L. Thony, and B. Garino (1996). Atrazine movement and dissipation in a sandy loam soil under irrigation An immunoenzymatic study. Bull. Environ. Contam. Toxicol., 56 359-366. 

The amount of a triazine retained or sorbed by soil can range from 0% to 100% of the amount applied, but typically sorption on silt loam, loam, or clay loam surface soils ranges from 50% to 80% of the amount applied. Although sorption of triazines (particularly atrazine) by soils has been studied for more than 40 years, there continue to be numerous studies each year to quantify sorption by different soils and to characterize the factors that affect triazine sorption. For instance, in a review of literature for 1964-1984, Koskinen and Moorman (1985) found 343 published Kd values for sorption of atrazine on 148 soils. These published Kd values averaged 4.0 4.0. From 1985 through 1995, 35 additional references reported Kd or Kf values for atrazine alone (Table 21.6). Average reported Kd values are 2.4 7.3 for 109 surface and subsurface soils (Paya-Perez et al., 1992) and 4.9 1.9 for 117 surface soils (Jaynes et al., 1995). 

Nearly all thin film photolysis studies involving triazine herbicides have utilized model surfaces such as filter paper (Jordan et al., 1964 Morita et al., 1988), aluminum (Jordan et al., 1965), glass (Pape and Zabik, 1972 Chen et al., 1984 Hubbs and Lavy, 1990), and silica gel (Lotz et al., 1983). A shortcoming of the use of model surfaces is that herbicide dissipation due to volatility losses is often not accounted for (Hubbs and Lavy, 1990). Konstantinou et al. (2001) studied the sunlight photolysis of atrazine, propazine, and prometryn on soil (sandy clay loam, clay loam, and... 

Deethylatrazine (DEA) and deisopropylatrazine (DIA) also have been detected in shallow, unsaturated surface-water runoff from a Eudora silt loam soil with DEA present at higher concentrations (Mills and Thurman, 1994a). Dissolved atrazine, DEA, and DIA concentrations in water samples from two closely spaced lakes indicated large differences in input from watershed nonpoint sources. Levels of these chemicals increased in response to spring and early summer runoff events (Spalding et al., 1994). In studies conducted by Gaynor el al. (1992, 1995), DEA was found in surface runoff samples that contained atrazine. Hydroxyatrazine (HA), deethyl hydroxyatrazine (DEHA), and deisopropyl hydroxyatrazine (DIHA) have also been identified in surface water (Lerch et al., 1995). 

However, degradation then slowed, with 16% still remaining in the silt loam 16 months after application, as compared to 20% in the clay loam and 22% in the sandy loam. In a 2-year study on the same three soils, dissipation was much slower in year two than in year one. Averaged over both years, 21 days after application 93%, 56%, and 85% of the atrazine applied still remained in the sandy loam, silt loam, and clay loam soils, respectively, with >95% of the amount present remaining in the surface soil (Koskinen et al., 1993). In a third study on the same sandy loam soil a year later, after 30 days the majority of the atrazine remaining (161 pig/kg) was in the top 15 cm of soil (Buhler et al., 1994b). About 2pg/kg was present at 45-60cm. By 60 days after application, only 5 pg/kg remained in the top 15 cm of surface soil. 

Soil Degradation Study. One hundred and forty-four amber jars (500 mL) were loaded with 50-g fresh sandy loam soil and divided into two groups. Seventy-two of them were adjusted at 14 percent moisture (group I). The other 72 were adjusted at 22 percent moisture (group II). The 72 samples in group I were further divided as follows 36 of them were spiked with dicamba, 2,4-D, and pentachlorophenol at 1 yg/g the other 36 spiked with lindane, atrazine, and diazinon at 1 yg/g. Spiking was performed after the soil was adjusted at 14 percent or 22 percent moisture. The spike was added in a concentrated solution to the soil (100 yL of a 0.5 rag/mL stock solution) and was mixed thoroughly with the soil. 

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