Pesticide measurement

Rice CP, Chernyak SM, McConnell LL. 1997. Henry s law constants for pesticides measured as a function of temperature and salinity. J Agric Food Chem 45 2291-2298. 

Stork A, Ophoff H, Smelt JH, et al. 1998. Volatilization of pesticides Measurements under simulated field conditions. In Fuhr F, Hance RJ, Plimmer JR, et al, ed. The Lysimeter Concept Environmental behavior of pesticides. Washington, DC American Chemical Society, 21-39. 

These experimental toxicity values were compared with the theoretical toxicity units calculated for each sample and organism from the pesticide concentrations measured in the samples and their toxicity (50% effective concentration, EC50) towards the corresponding test organisms [12]. This comparison, which is illustrated in Fig. 6, gives an estimation of the extent to which the pesticides measured contribute to the observed experimental toxicity as well as about their relative contribution to it. 

Concentrations of the pesticide measured in the three soils were higher than estimated, but were less than one pg per litre. Streams in an area where there are a number of greenhouses contained higher concentrations than those measured in drainage water this was attributed to discharge of surplus spray liquid. 

One of the four plants presently treats and reuses 75% of its waste stream as vent scrubber washwater. A second plant incinerates formulating/packaging process waste and discharges incinerator blowdown that contains levels of pesticides measured as not detected. 

The extremely sensitive inductively coupled plasma-mass spectrometer was described in Section 21-6. Figure 24-23 shows 15 pesticides measured by gas chromatography— inductively coupled plasma-mass spectrometry. Eluate was atomized and ionized in the plasma. Ions were measured by a mass spectrometer that could monitor any set of mlz values. The figure shows traces for P, S, I Cl, or Br. 

Table 26.5 Acute and Chronic Toxicity of Pesticides Measured from Laboratory Exposures of Fish Species...

In view of these variations, the calibration of equipment should be done by individual users under the conditions in which they will apply the pesticide. Measurement of each of the three factors (nozzle output, swath and speed) can be measured and the volume application rate calculated using the formula ... 

It is always good practice to repeat measurements. For example, if we are measuring the concentration of pesticide in a lake, we might fill a large bottle with lake water and later (back in the laboratory) withdraw 50 cm portions of the lake water from the bottle and analyse each portion for pesticide using the same analytical technique. The mean pesticide concentration is then obtained by averaging the concentrations found in each 50 cm portion. In this case, the error in the pesticide measurements is the difference between the mean measurement and the true concentration. 

Cortes, D. R., I. Basu, C. W. Sweet, K. A. Brice, R. H. Hoff R. A. Hites, 1998. Temporal trends in gas-phase concentrations of chlorinated pesticides measured at the shores of the Great Lakes. Environ. Sci. Technol. 32 1920-1927. 

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