Atrazine reservoirs

In contrast to the water results [92], in which only atrazine, NP and OP were above the legislated limits, the sediments present more elevated concentrations with 18 out of the 20 compounds legislated having some samples above the limits. This different behaviour shows that the water is a more changeable matrix that reflects the current contamination while the sediments behave as a reservoir for the contaminants as a result of their accumulation potential. 

Three of the 28280 assessed systems had multiyear average concentrations above 3.0ppb for the 8-year period (Table 29.5). Each obtained raw water from an impounded (reservoir) surface water source. The multiyear average for atrazine concentrations in these systems ranged from 3.30 to 3.41 ppb. 

Figure 30.8 Concentrations of atrazine and cyanazine in water samples selected from reservoirs of midwestem United States during 1992 and 1993.

In a study by Fallon and Thurman (1996), a conceptual model was presented to explain how DAR could be used to follow runoff through Perry Lake in northeast Kansas. In the model, the reservoir already contained water with atrazine and DEA from the previous year s runoff. The arrows in Figure 30.16 show the direction of the flow for the dam. Near the dam, the water is older in age and contains water from the previous summer, whereas the upstream water contained herbicides that had entered the reservoir during the fall and winter. Therefore, the DAR values were higher on the upstream end of the reservoir, as shown in Figure 30.16 by the actual DAR values for each time period. The concept of the DAR has proved to be a useful tool in following water movement through a reservoir. 

An example of the combined use of ozone, hydrogen peroxide, and carbon filtration is seen in the operation of water plants located from the South and East of England to the North of London. Croll [220] presents a detailed explanation on the performance of such plants that supply the drinking water for a population of more than 3.6 million inhabitants. Water in reservoirs can have concentrations of 0.53 and 0.31 pg L-1 of atrazine and simazine, respectively. 

Atrazine, now banned in many European countries but which still accounts for 40% of all herbicide applied in the USA and is most often applied in the spring, is routinely present in streams, rivers, and reservoirs at levels of 1 10 pg L close to the USEPA standard of 3 pg L 1 163,164 peaks of 100 200 pg L however, have been... 

Another heterogeneous immunoassay, developed for field use [82], [83], employs immunofil-tralion (Fig. 11). Antibodies are immobilized in the middle of a nylon membrane. The first few drops placed on this membrane are immediately sucked down into a reservoir by capillary action. A few drops of washing buffer are then added, followed by AP- (alkaline phosphatase) labeled antibody to the analyte and. subsequently, a few drops of indoxyl substrate. As in the case of the sandwich immunoassay, the depth of color of the spot formed in the middle is linearly proportional to the analyte concentration i.e., an ELISA is obtained for determination of aflatoxin [84], atrazin [85], [86]. [87], carbaryl [88] or polychlorinated... 

Analyze a 250-ml water sample containing 10 ppb of atrazine by passing through a 75-ml reservoir into a C g extraction column (6 ml, J. T. Baker, Phil-lipsburg, NJ) held in a Baker-12 vacuum manifold, at a flow rate of 5 ml/min. (Prewash the column before use with 12 ml of methanol followed by 12 ml of deionized water.) Wash the column with 10 ml of deionized water (discard) and... 

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