Field exposure rate

Schwartz (4) provided the early fallout field tray information for Palanquin. He reported a fraction of total atoms produced per square foot divided by the field exposure rate at the tray locations in roentgens/ hr. at H + 1 hr. for the different nuclides studied. The trays were placed from about 2500 to 25,000 ft. from ground zero the data show no trend with distance, so the determinations for the different trays were averaged. 

It has been demonstrated that it is possible to lower the level of airborne radon progeny by filtering and/or expose the air to an electric field. If the radiological risk is measured by the potential alpha energy concentration (PAEC) or exposure rate, for instance expressed in J m 3 or WL, the level may be lowered to about 10-20 % of the value in untreated air, while the reduced level may only be about 40-50 % of the untreated one if the average dose to a certain part of the respiratory tract, for instance expressed in Gy year 1, is considered. 

Also nickel, often used in decorative Ni-Cr coatings, is a metal sensitive to the influence of sulphur compounds in the atmosphere. This may be illustrated by results from a field exposure giving the corrosion rate of 0.4 um/year in rural and 2.7 /jm/year in urban atmospheres (U). In other investigations as high corrosion rates as 6 yum/year has been found in industrial atmospheres (1 ). Also the life of decorative Ni-Cr coatings is substantially shorter in urban/industrial than in rural areas (13). 

The day following application 20 percent of nesting females had disappeared compared to 5.5 percent in the field treated with phosalone and 0.8 percent in the control. At the time of application, exposure rates of foragers were estimated at 82 and 74 percent. Larvae were slightly affected in treated fields during the 3 days post-treatment, mortality reaching 4.8 and... 

A great variety of materials and procedures have been used for estimating hazards of pesticides to bees by either the semi-field or the field method. Cages and greenhouses were generally preferred because exposure rates cannot be controlled in the field. 

As demonstrated, often only one or two doses are feasible. These may well exceed exposure rates however, application rates similar to what is seen in field studies are likely to yield non-detectable levels. 

Dermal exposure to captan and benomyl by strawberry harvesters has been the subject of several previous studies (1.2.3). This field study was designed to test a number of hypotheses and the reproducibility of dermal exposure rate measurements taken under field conditions. Most of our past studies have not been designed for a particular pesticide but were modified to accommodate the pesticide chosen by the grower to control a certain pest. In this case, the pesticide was carbaryl (1-naphthyl N-methylcarbamate) an insecticide used to control the spittlebug and leafroller. Our results could then he compared with those obtained by Maitlen and co-workers (A) who studied workers exposed to carbaryl in an apple orchard. Furthermore, attempts will be made to test possible positive correlations between age and dermal dose rate versus productivity and dermal dose rate versus age of harvesters. Difference of dermal exposure due to age or... 

Dislodgeable Foliar Residues and Dermal Exposure. Dislodgeable foliar residues were determined on days 1,3,7,14,15,16, and 17 after carbaryl had been applied to the strawberry fields at the rate of 2 Ib/A. Results of these analyses are found in Figure 2 and Table VIII. The decline of foliar residues appears to follow first-order kinetics, and carbaryl has a half-life of approximately 4.1 days. The three last sampling dates are identical with the study dates. From these data and exposure rates of corresponding days (Table V), a ratio can be calculated by the following equation ... 

Each metal behaves in a unique way with respect to atmospheric corrosion properties, and the conclusions drawn from the nickel study cannot necessarily be drawn for other metals. However, if the same or similar corrosion products are formed on a given metal when exposed to a laboratory and a natural atmospheric environment, respectively, the results surest that the same corrosion processes are operating in both exposures. Table 4 displays examples of reported laboratory tests that have generated corrosion products similar to those seen in natural field exposures [13-18]. It appears that certain combinations of two or three corrodents at concentrations below 1 ppmv, together with a proper choice of relative humidity and airflow rate, can generate the corrosion products that are formed in natural field environments. 

There are several types of instruments that can be used for radiation monitoring, each with itsown characteristics,advantages,and limitations.There havebeenseriousradiationexposures when individuals used an instrument that was not appropriate for the radiation field involved. This section willbe limited to the type ofradiation detection instruments that are commonly used forradiationsurveysratherthanthoseusedforlaboratory research.The instruments will primarily be those intended to measure external exposure rates. 

However, as already alluded to, lab-culture data do not always translate into measurable rates in natural or field exposures of PE. Early data on incubating PE in soil show minimal weight loss even over very long periods of exposure. Reported experimental results on PEs (Table 6.5) are consistent with very slow biodegradation. 

Effect of Sulphates. Sulphur dioxide comes from combustion of fuels and is identified as one of the most important air pollutants which contribute to the corrosion of metals. In the presence of SO2, corrosion starts at 60 % relative humidity and the rates are considerably higher than in the absence of any contaminate. There is a close relation between the uptake of SO2 and the corrosion rate measured during field exposure over a period and it depends considerably on the acid hydrolysis of SO2 in water and the fast oxidation of SO2 on iron surfaces. The cycle consists of two reactions, the oxidative hydrolysis of iron sulphate and the subsequent acid corrosion of iron [67]. 

The corrosion rate of instantaneously passivated WS panels is shown in Table 4.12 compares well with corrosion rate of 42 m field exposure on WS panels in 3.5 % NaCl as given in Table 3.2. Corrosion rate on WS panels was also almost similar range and order when tested in SAEJ and as well as NACE solution. It was interesting to note that corrosion rate was low in SAEJ solution when passivated in 0.1 M Na2S04 +0.001 N NaCl solution. Very low amount of chloride ions in the solution perhaps consolidate the passive layer resulting in lower corrosion rate. A fact which agrees well with similar data that reported chloride ions leads to a shift of the repassivation potential toward negative side and the sulphates in 0.1 M... 

Field exposure is a slow oxidation exposure process which has been imitated at the laboratory by slow scanning. During instantaneous passivation current gradually decreased and reached a steady-state value within 2 kilosec, but passivation was continued till 5 kilosec before taking it to corrosion rate measurement in three different media (-820 mV) as given in Fig. 4.8a. The panel passivated at -800 mV reached steady state with 500 s and passivation was continuous till 1.8 ksec. The difference in Raman shift of -820 mV passivated and -800 mV passivated can... 

Corrosion rate of weathering steels was found lower with respect to mild steels in accelerated laboratory tests. They corrode most rapidly with respect to field exposure test... 

Present research work has been carried out in two parts field exposme tests and accelerated laboratory tests on unexposed panels. Under field exposme test three representative sites PI very close to sea shore and free firom SO2, P2 away from sea with presence of SO2 and P3 industrial environment with presence SO2 were chosen. Analytical techniques (EDX, XRD and Raman spectroscopy) were used for rust characterisation and SEM was employed for understanding the morphological state. Corrosion rates were estimated after different periods of exposure at sites. It is found that though accelerated laboratory test can predict the general trend of corrosion, actual field test data cannot be created in laboratory. So an attempt was made to simulate protective rust coating in the laboratory that is typical of field exposure protective rust formation on weathering steel. 

Field exposure test is a very slow oxidation process whereas the accelerated laboratory test is a very fast oxidation process. Several months/years together are required to get measurable mst on surface of steel panels in field exposure. In accelerated laboratory test rate of oxidation is much faster and rust layers/oxides are formed, very quickly. The rust products/oxides formed in both the cases are identical but their manifestations are different. As a result corresponding morphologies and corrosion rates are vastly different. 

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