Sampling site selection

The present report contains comprehensive instructions for sample site selection and sample collection. In addition, a summary of methods intended for sample preparation and analysis is included. 

In order to achieve any one or a combination of the previously listed objectives, it is necessary to measure ambient air concentrations of dioxin. In order to interpret variations in the distribution of air pollution concentrations, the on-site measurement of meteorology and a basic understanding of the role of the atmosphere in transporting and dispersing air pollutants is needed. Sampling Site Selection... 

Afterwards, the spatial coordinates X and Y (referred to a UTM ED 1950 system) and geo-morphological, paedological, and lithological data were considered and codified in order to be used for the sampling sites selection, as extensively described in previous studies [44] and summarised in Table 1. 

The purpose of sampling is to obtain lead-containing particles, adsorbed gases, liquids, and solid samples that will indicate the spacial, temporal, and chemical nature and the concentration of lead in the environment. Method of sample collection, sampling site selection, and sample processing procedures are all of major importance in sampling methods for lead. 

Before a source analysis program is undertaken, it is important to decide which information is really required. Sampling sites must be selected with care. Choice of the site can significantly affect accuracy and cost. Care must also be taken in the selection of sampling points at the site. Measurement usually involves the deterrnination of temperature, concentration, and characterization of the gas contaminants. It also requires the mass rates of emission of each contaminant, therefore concentration and volumetric flow data are required. 

The selection of a sampling site and the number of sampling points required are based on attempts to get representative samples. To accomplish this, the samphng site should be at least eight stack or duel diameters downstream and two diameters upstream from any flow disturbance, such as a bend, expansion, contraction, valve, fitting, or visible flame. 

The basis for assessment of river quality is valid data, but the question of data validity is secondary to the fundamental question What is the purpose of the river quality assessment activity What questions are being asked In short the means are determined by the ends. If, for example, the intent of an assessment program is to ascertain compliance with law, then a fixed interval "grab sampling program could be established at various river system sites selected on the basis of established guidelines which are consistent with the... 

Pesticides used on crops grown on the test site in previous seasons may also have an impact on the outcome of a field residue trial. Carryover of prior pesticide applications could contaminate samples in a new trial, complicate the growth of the crop in a trial, or cause interference with procedures in the analytical laboratory. For this reason, an accurate history of what has transpired at the potential test site must be obtained before the trial is actually installed. The protocol should identify any chemicals of concern. If questions arise when the history is obtained, they should be reviewed with the Study Director prior to proceeding with the test site. In most annual crop trials, this will not be a significant issue owing to crop rotations in the normal production practices, because the use of short residual pesticides and different chemical classes is often required for each respective crop in the rotation. However, in many perennial crops (tree, vines, alfalfa, etc.) and monoculture row crops (cotton, sugarcane, etc.), the crop pesticide history will play a significant role in trial site selection. 

Each of the five main steps in field conduct (site selection, test plot layout, test substance application, sample collection, and sample storage/handling) is addressed below. 

Soil properties A Soil texture (sand, silt, clay), organic matter/carbon content, and pH Stones, roots, and hardpans must be largely absent to allow representative sampling of soil profile Soil properties should appear uniform over test site Soil texture data should be available at time of site selection. Soil properties must match study purpose. This can be realistic use conditions, realistic worst-case or worst-case in terms of agrochemical mobility and persistence Must ensure that the majority of samples can be taken from the deepest sampling horizon. Information about sub-soils can be obtained from soil maps, test coring and on-site interviews... 

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