Sampling Networks

The selection of the sampling grid depends to a large extent on the expected character of the anomaly and the scale of the study. 

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Canada, and Mexico (23). The National Atmospheric Deposition Program has established the nationwide sampling network of —100 stations in the United States. The sampler is shown in Fig. 14-9 with a wet collection container. The wet collection bucket is covered with a lid when it is not raining. A sensor for rain moves the lid to open the wet collector bucket and cover the dry bucket at the beginning of a rainstorm. This process is reversed when the rain stops. 

Lodge, J.P. Pate, W. Swanson, G.S. Hill, K.C. Lorange, E. Lazrus, A.L. Chemistry of United States Precipitation, Final Report on the National Precipitation Sampling Network National Center for Atmospheric Research, Boulder, CO, 1968, pp... 

Three-dimensional representation of the latitudinal distribution of atmospheric carbon dioxide in the marine boundary layer. Data from the NOAA CMDL cooperative air sampling network were used. The surface represents data smoothed in time and latitude. The Norwegian and Swedish flask sampling effort at Zeppelin Station is shown in the inset as flask monthly means. (Figure kindly provided by Dr Pieter Tans and Dr Thomas Conway of NOAA (CMDL).)... 

Conway, T. J., Tans, P. P. and Waterman, L. S. (1994a). Atmospheric CO2 records from sites in the NOAA/CMDL air sampling network. In Trends 93 A Compendium of Data on Global Change, Rep. ORNL/CDlAC-65 (T. A. Boden et al. eds), pp. 41-119. Oak Ridge Natl. Lab., Oak Ridge, Term. 

Some tanks are installed with permanent leak identification sensors, which can check for leaked fuel vapor or liquid as it comes into contact with the sensors.21 However, these, as well as all the environmental sign tests (visual or instrumental) may be triggered by a spill instead of a leak. The success of external systems depends on the sensitivity of the sensor, the ability of the sensor to distinguish the stored chemical from other chemicals, the ambient background noise level of the stored chemical, the migration properties of the chemical, and the sampling network. 

Concentration units were given in microgram/liter of water and in microgram/ kilogram of SE/soil. The sampling network for SW and SE coincided geographically, and the same for GW and soil (see Fig. 6 for sample location and Table 2 for sample identification). 

Mirex has been detected in wet precipitation over rural areas at concentrations of less than 1 ng/L (ppt) (EPA 1981b). Rainfall samples collected at several sites in 1985-1986 as part of the Great Lakes Organics Rain Sampling Network contained from >0.2 to <0.5 ng/L (ppt) of mirex. Mirex was not detected consistently at many stations throughout the sampling period therefore, quantitative results for mirex were not presented (Strachan 1990). Air samples taken over southern Ontario in 1988 showed mirex in 5 of 143 samples, at an annual mean concentration of 0.35 pg/sol m (range, 0.1-22 pg/m ) with all of the positive samples detected in polluted environments (Hoff et al. 1992). 

Prior Applications. The first application of this traditional factor analysis method was an attempt by Blifford and Meeker (6) to interpret the elemental composition data obtained by the National Air Sampling Network(NASN) during 1957-61 in 30 U.S. cities. They employed a principal components analysis and Varimax rotation as well as a non-orthogonal rotation. In both cases, they were not able to extract much interpretable information from the data. Since there is a very wide variety of sources of particles in 30 cities and only 13 elements measured, it is not surprising that they were unable to provide much specificity to their factors. One interesting factor that they did identify was a copper factor. They were unable to provide a convincing interpretation. It is likely that this factor represents the copper contamination from the brushes of the high volume air samples that was subsequently found to be a common problem ( 2). 

Probably the most complete study of river water quality w as completed by the U.S. Geological Survey, released in early 1987 and periodically updated. The initial survey was coordinated by Smith and Alexander (USGS) and Wolman (The Johns Hopkins University), including water quality records from two nationwide sampling networks. The network included over 300 locations on the major nvers of the United States. Twenty-four water quality parameters are measured. Originally, the two networks were comprised of (1) the National Stream Quality Accounting Network (NaSQUaN) and (2) the National Water Quality Surveillance System (NWQSS). Locations of stations are shown on the map in Fig. 1. The measured water-quality indicators include ... 

Fig. 1. Analysis of major river waters based upon a sampling network comprised of over 300 stations and involving two systems...

After the barrier frame was in place, pipes for the injection/extraction wells, piezometers, and the sampling network were suspended in the tank from cables. Sand was then added in lifts to fill the remaining aquifer portion of the tank. After the aquifer material was in place the SMZ was packed into the permeable barrier frame. The pipes were buried in place as the tank and frame were filled. 

Selection and comparison of spray materials Design specifications for sampling networks... 

Data from National Air Sampling Network and Continuous Air Monitoring... 

The rainwater chemical concentrations were examined to determine the spatial variations of several species over the mesoscale extent of the sampling network. Geographical mapping of rainwater concentrations demonstrated an enhancement of H, SO.-, As, Pbf Cuf Inf and Sb downwind of the smelter (to the northeast), consistent with the hypothesis that the smelter was an important source of these species. 

We have analyzed the rainwater chemical data with multivariate data analysis techniques to identify sources influencing the area covered by our sampling network. Two events were included in the principal component analysis (PCA) the February 15 storm presented here and another storm collected during smelter operation on March 20, 1985... 

Precipitation sampling networks in the United States generally collect either daily (UAPSP, MAP3S) or weekly (NADP, NTN) samples. 

Evidence of pesticide dispersal in air remote from treated areas is given by West (23). Exploratory determinations were made on 18 samples of ambient air collected over four California cities in 1963. All but two contained measurable amounts of DDT. Air samples from nine different stations in the national air sampling network contained from 0.0002 to 0.34 fig. of DDT per 1000 cubic meters of air filtered over a 24-hour period. 

Another important goal of a tropospheric chemistry research program should be to establish a global air sampling network to characterize the distribution of atmospheric compounds today. In order to determine if the tropospheric composition is changing, a commitment must be made to maintain this network into the 21st century. The interchange of... 

Figure 2 Global distribution of atmospheric CH4 from 1992 to May 1, 2001. Three-dimensional latitudinal distribution of CH4 in the marine boundary layer is presented. The surface represents data from the NOAA/CMDL cooperative air sampling network smoothed in time and latitude (source National Oceanic and Atmospheric Administration (NOAA), Climate Monitoring and Diagnostics Laboratory (CMDL), Carbon Cycle Greenhouse Gases). Updated versions are available on line at http //www.cmdl.noaa.gov/ccgg/gaUery/index pageType =...

Ciais P., Tans P. P., White J. W. C., Trolier M., Francey R. J., Berry J. A., Randall D. R., Sellers P. J., Collatz J. G., and Schimel D. S. (1995b) Partitioning of ocean and land uptake of CO2 as inferred by 8 C measurements from the NOAA climate monitoring and diagnostics laboratory global air sampling network. J. Geophys. Res. Atmos. 100(D3), 5051-5070. 

Conway T. J., Tans P. P., Waterman L. S., Thoning K. W., Kitzis D. R., Masarie K. A., and Zhang N. (1994) Evidence for interannual variability of the carbon cycle from the National Oceanic and Atmospheric Administration/Climate Monitoring and Diagnostics Laboratory Global Air Sampling Network. J. Geophys. Res. 99, 22831-22855. 

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