Available Sampling Procedures

Sampling of lead in drinking water has to include contributions from all soimces and factors influencing the lead concentrations at the tap. Therefore, various sampling techniques with different purposes have been developed and routinely applied. These are listed in the next section. 

The lead-pipe test is used to assess the lead level at the consumer s tap. Basically, the lead-pipe test measures the lead concentration in aged lead pipes for selected 

In the Drinking Water Directive 98/83/EC, the parametric value (PV) for lead is 10 ig . The parametric value refers to water as it emerges fi om the customer tap, assessed on the basis of representative monitoring (Note 3). Note 3 is as follows  

The values apply to a sample of water intendedfor human consumption obtained by an adequate sampling method at the tap and taken so as to be representative of a weekly average value ingested by consumers. Where appropriate the sampling and monitoring methods must be applied in a harmonized fashion to be drawn up in accordance with Article 7(4). Member States must take account of the occurrence of peak levels that may cause adverse effects on human health. 

Variations in average weekly lead concentrations at the consumers tap 

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Suction lysimeters are required for some field-scale groundwater monitoring studies to monitor the transport of compounds of interest through the unsaturated zone. Unlike monitoring wells or water supply wells that sample water from the saturated zone, suction lysimeters sample water from the unsaturated zone. This section provides a summary of the installation and sampling procedures for pressure-vacuum suction lysimeters. A detailed discussion of unsaturated zone sampling devices is available elsewhere. 

Anticipated persistence and mobility of agrochemical and degradates Anticipated variability in soil residues and cost constraints Depends upon specific analytical procedures (and associated LOQ) and available sample storage and processing capabilities Necessary for most dryland and irrigated cropping scenarios... 

Overall, it is not possible to evaluate whether any of these factors have compromised the data included in published studies. More research is required to determine how U-and Th-series nuclides are affected by various well construction methods and sampling procedures, how reliable are data from wells not designed fro trace element monitoring, and if there are any factors that have affected the data collected from past studies. Most importantly, radionuclide studies must incorporate greater awareness of the potential problems, summarize whatever details are available regarding the wells used, and consider potential problems where the relevant information is not available. 

The recent trend of decreasing available sample volumes and requiring lower limits of quantitation (LLOQs) means better sample preparation procedures are under consideration. Further improvements MS sensitivity will eventually impact sample preparation strategies and sample throughput. 

Automated programmable instruments that can carry out the repeated thermal cycles necessary for PCR and that can accommodate multiple samples simultaneously are now widely available. The procedure is usually performed with thermostable DNA polymerases. PCR is widely used to facilitate detection of minute amounts of viral DNA. The technique can also be used to detect specific point mutations, provided the approximate site of mutation is known. One limiting feature of this approach arises from the fact that the bacterial polymerases frequently make errors when synthesizing new strands and so can introduce mutations that are not present in the original sample. 

Both dynamic and static sampling procedures are suitable for taking samples for olfactometric measurements (15), (16). If the olfactometer and the panel are available close to the source dynamic sampling may be preferred. The equipment for preventing condensation in the sampling pipe and contamination of the sampling pipe and the olfactometer by dust should be provided. 

From these simple calculations the ANOVA table can be constructed together with the HORRAT ratio. An important difference from the conventional ANOVA table is that it allows for the sample variation to be accounted for. The general ANOVA table and calculated values for S samples are shown in Tables 28 and 29 but the example uses only two. However, if more than two samples are desired/available the procedure can be extended. 

The total available oil procedures take -40 min. It s best to prepare samples before distillation. Samples can be titrated while the next sample is distilled. The other titration procedures should not take >20 min, provided reagents are prepared. The colorimetric assays will take 3 hr given preparation of reagents and generation of standard curve. 

In general, three broad methods are available for planning a sampling procedure [GARFIELD, 1989] probability sampling, nonprobability sampling, and bulk sampling. 

Deep water sampling procedures are similar to those for surface water sampling, the difference is in the sample delivery method. There are several types of discrete depth liquid samplers available today to perform this task, such as glass weighted bottles, Wheaton bottles, Kemmerer samplers, or electrical pumps. 

The analytical methods for the main ions and heavy metals are well established and there is no special need for further improvements. The greatest uncertainties in these methods lie in the sampling procedures and site representativeness. For POPs, reference methods are at present available only for air measurements such methods need to be established for precipitation samples as well. Even though the analytical method may be the same, sample preparation and the sampling itself... 

Coincident with the development of sampling procedures were the constant iterative improvements in extraction, separation, identification and quantitation of organic compounds. Special emphasis was placed on selected compound classes such as the polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), chlorinated benzenes, and chlorinated dibenzo-p-dioxins (dioxins). The best available procedures were used to determine these components because they have known acute or chronic effects and previous studies suggested that they might be present in effluents from the combustion of coal alone and combination coal/RDF. 

MOC in Fig. 8.16d is difficult and leaves a lot of room for subjectivity. Further, MOC determination is sensitive to the accuracy of efficiency measurements—factors such aa liquid and vapor distribution, sampling procedure, end effects at the top and bottom of the packings, and the availability of a large number of efficiency points near the MOC, where conditions may not be steady-state. For instance, for one set of published experimental data reported by Eckert and Walter (61), MOC increased by about 10 percent due to reducing packed height from 10 to 5 ft-... 

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