Sampling season

Results and Discussion. The organic compounds identified in the Delaware River water samples are listed in Table III. These compounds cover a broad range of chemical types and include most of the major lipophilic compounds in the river. The data include the concentration range and the location of maximum concentration for each sampling season. Structures for a selected group of compounds are given in Figure 4. 

Recommendations for Improvements in the Design of Guideline Studies 36 Population Selection 36 Sampling Location 36 Sampling Season 36 Duration of Measurements 37 Post-Registration Studies 37 CONCLUSIONS AND RECOMMENDATIONS 37 ACKNOWLEDGEMENTS 38 REFERENCES 38... 

The timing, frequency and location of sampling, as well as the type, number and size of specimens to be taken, is usually determined by a combination of factors, i.e., strategy of ESBs, characterization type, sample chemical concentration, distribution, abundance and availability of the population and/or materials to be sampled, seasonal variability, storage room, ease of collection and transport, costs, etc. (13). 

How common is SADS A local telephone survey in the US found that 92% of the survey subjects noticed seasonal changes of mood and behavior to varying degrees. For 27% of the sample seasonal changes were a problem and 4.3% to 10% of subjects, depending on the case-finding definition, rated a degree of seasonal impairment equivalent to that of patients with seasonal affective disorder. Rosenthal remarked It is apparent that... 

Schneider in HELCOM (1996) for the time interval 1980-1993. By comparison, he did not find a negative trend for dissolved Cd and Cu below the halocline between 1980 and 1993. Because of the inconsistencies in the sampling seasons, sampling equipments, analytical methods, and quality control, the database from which these calculations were derived was not uniform. Also, sampling was performed only periodically, so there was a lag of several years. 

Station Type sample Season (Fall/Spring) Depth (m) DOC (mg/L) Humic (fcg/L) Fulvic (/tg/L)... 

The quantification of marine Utter is complicated by the size of the oceans and surfaces or volumes to be sampled, seasonal variations in intake and the presence of currents. Observation, trawling, direct coimting and filtration, overflight, video imagery, aerial photography, the use of submersibles and scuba diving are the main... 

To be useful for the purposes of dose calculations, measurements of food contamination should relate to the edible portions, not to the entire organism or plant, and it should also be made clear whether the results are on the basis of wet weight or dry weight. The dose calculations made on the basis of the measurements of food contamination should use an average contamination level derived from at least several representative samples. Seasonal crops should be sampled near the time of harvest. Dose calculations should be made on the basis of measurements of the contamination of only those species that are actually consumed by individuals of the critical groups. 

The objective of a proper sampling program is to take a sufficient number of samples to obtain a representative estimate of exposure. Contaminant concentrations vary seasonally, with weather, with production levels, and in a single location or job class. The number of samples taken depends on the error of measurement and differences in results. It is important also that if the employer has conducted air sampling and monitoring in the past, a thorough review of the records should be made. 

While certain reservations must be kept in view (i.e. there is not necessarily a correlation between pH and corrosivity, and different samples of the same species of wood show a wide scatter of pH values, which might well be even wider if differences in duration of seasoning were taken into account), the results of vapour corrosion tests nevertheless indicate a general correlation between quoted pH values and the corrosiveness of wood vapours. It may reasonably be concluded that a strongly acid wood, pH less than 4-0, is potentially dangerous, and a less acid wood, pH more than 5 0, is likely to be relatively safe. 

Where IX designs are being considered, a one-off sample is simply not appropriate. Real analyses over a period of time are required, and seasonal variations should be properly understood in order to provide a realistic design. 

Table II. Mean concentration ranges in the central Lagoon waters (min -max 4 seasonal samplings, /imol T ). Area A is represented by 6 stations, area D by 4.

In random samples of soil taken from five Alabama counties, only 3 of 46 soil samples contained methyl parathion. The concentration in these samples was <0.1 ppm (Albright et al. 1974). Aspartofthe National Soils Monitoring Program, soil and crop samples from 37 states were analyzed for methyl parathion during 1972. Methyl parathion was detected in only 1 soil sample, at a concentration of <0.1 ppm and taken from South Dakota, out of 1,246 total samples taken from the 37 states (Carey et al. 1979). In soil and sediment samples collected from a watershed area in Mississippi, methyl parathion was not detected in the soil samples. In three wetland sediment cores, however, measurable concentrations of methyl parathion were detected during application season (Cooper 1991). 

Not all these polyether occur together in the same shellfish samples. OA was the major toxin in the mussel specimens from most of the European countries (42), while DTXl was the major toxin in mussel in Japan and in Sogndal, Norway (43). Scallops in Japan show the most complicated toxin profile. Furthermore, the relative ratio of the toxins varied regionally, seasonally, and annually. Pectenotoxins were detected, however, only in Japanese shellfish. Distribution of toxins is summarized in Table I. 

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