Inputs of atrazine

Atmospheric transport of atrazine-contaminated aerosol particulates, dusts, and soils may contribute significantly to atrazine burdens of terrestrial and aquatic ecosystems. The annual atmospheric input of atrazine in rainfall to the Rhode River, Maryland, as one example, was estimated at 1016 mg/surface ha in 1977, and 97 mg/ha in 1978 (Wu 1981). A similar situation exists with fog water. When fog forms, exposed plant surfaces become saturated with liquid for the duration of the fog (Glotfelty et al. 1987). 

Three tributaries, the Susquehanna, the Potomac, and the James Rivers account for approximately 80 to 85 percent of the fresh water flow into the Bay from the northern and western regions. These three tributaries also dominate herbicide input to the Bay (8). Foster and Lippa (8) present the most comprehensive data sets available. They estimated that 2,700 kg of atrazine were loaded into the Bay in the period 1992-1993 1,700 kg via the Susquehamia, 780 kg via the Potomac, and 220 kg via the James. Similar estimates of atrazine loading were reported by the U. S. Enviromnental Protection Agency (USEPA) 15, 24) for the Susquehanna and the James Rivers. Godfrey et cd. 25) showed that the relative error in the estimation method used by Foster and Lippa (8) was less than 40%. The Chester and Choptank Rivers are the major pathways of atrazine input fix)m the Eastern Shore of the Bay. Based on concentration and flow rate, fliese rivers accoimt for a combined mass load of approximately 100 kg. The total input of atrazine via surface runoff is thus 2,800 kg/yr. 

The Susquehanna River fluvial input of atrazine in the Upper Bay region is 1,700 kgtyr (8). The Chester and Choptank Rivers discharge proximately 100 kgtyr. Both contributions yield a total surface flux of 1,800 kg/yr into this region. To estimate the amount of atrazine introduced as groundwater inflow. 

Table 9 Average annual inputs and losses of atrazine (kg/yr) to Lake Michigan...

Ulrich, M. M., S. R. Mttller, H. P. Singer, D. M. Imboden, and R. P. Schwarzenbach, Input and dynamic behavior of the organic pollutants tetrachloroethene, atrazine, and NTA in a lake A study combining mathematical modeling and field measurements , Environ. Sci. Technol., 28, 1674-1685 (1994). 

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. 

The studies have very different cost estimates for the loss of availability for either atrazine or a triazine. The atrazine loss costs range from 458 million (regional) to 3,277 billion annually for com and sorghum, while the triazine loss had cost estimates of 912 million to 3,350 billion annually. Differences in estimated effects depend upon input data, model types, and factors, such as different geographical regions and government policies. 

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). 

In order to produce the information needed for a hedonic analysis of the demand for pesticide characteristics (Soderqvist, Chapters, this volume), five properties of the herbicides, for which a continuous quantification was possible, have been selected price, persistence, action spectrum, reliability and toxicity. These properties cover approximately 10 out of 13 of the factors indicated in Table 2.5. Quantitative information for the five properties has been provided for the alternatives to atrazine, in order to provide input data for economic modelling (Soderqvist, Chapter 3, this volume). 

A complete description of the processes that govern the fate of agrochemicals in the Bay is still beyond our current scientific knowledge. Simplified analyses are thus often used to gain some insight into the trends of chemical concentrations in the Bay. The next section presents a descriptive siunmaiy of the relevant physical and chemical processes occurring in the Bay. A compilation of data on atrazine inputs to Ae Bay is summarized in the following section. These data are used to estimate a resident atrazine mass, which is compared to estimations made fi om measured field values. We then... 

Atrazine inputs to the Bay derive mainly from (1) surface runoff, estimated to contribute about 60% of the total load, (2) groundwater flux, contributing about 23% of total atrazine load, and (3) atmospheric input wet and dry deposition, which constitutes 17% of the atrazine load to the Bay. 

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