Stream sampling

An alternative method is sampling directlv from a moving or stationary conveyor with cutter traverse througk the complete material bed carried on the conveyor. The alternative method cannot assure executing complete extractions, or through-stream sampling, because in many applications residual fines from the material stream remain on the conveyor surface. 

Operation of a traversing sampler for gravity flow of material for through-stream sampling is required to meet the following design factors ... 

Limit the number of streams sampled and the components per stream routinely recorded by a given chromatograph. Choose only those really necessary for control. This simplifies maintenance and readout. 

Several studies have been conducted to measure methyl parathion in streams, rivers, and lakes. A U.S. Geological Survey (USGS) of western streams detected methyl parathion in five river samples taken from four states during a 14-month period in 1970 and 1971. The amount of methyl parathion detected ranged from 0.04 to 0.23 pg/L (Schultz et al. 1973). A later and more extensive USGS study analyzed water samples from major rivers of the United States four times yearly in the period of 1975-1985. Of the 2,861 water samples, 0.1% had detectable levels of methyl parathion (Gilliom et al. 1985). In a study of Arkansas surface waters, samples of lake and river/stream water were collected and analyzed over a three-year period (Senseman et al. 1997). Of the 485 samples collected, methyl parathion was found in one river/stream sample at a maximum concentration of 3.5 pg/L. Results from an EPA study in California detected methyl parathion in 3 of 18 surface drain effluent samples at concentrations of 10-190 ng/kg. Subsurface drain effluent water had concentrations of 10-170 ng/kg in 8 of 60 samples (lARC 1983). 

Side stream sampling devices can be used to collect biofilm and corrosion samples. The biofilm, inorganic passive layers, and metal attacked samples can be characterized with scanning electron microscopy and energy dispersive... 

Very high APEO concentrations in coastal water were reported from Israel. At 10 locations along the coast, water samples were taken, all near the mouth of a river or stream. Samples were taken 2-3 m from the shoreline. With reversed phase HPLC, total APEO concentrations were determined. The levels varied from 4.2 to as much as 25 p,gL 1, while concentrations in the rivers themselves were in the range of 12.5-75 xg L-1. In samples taken further offshore (between 50 and 150 km), concentrations had decreased to <1.0-2.6 p.gL 1. In all samples, the higher oligomers (around 10 ethoxylate units) were most abundant. Unfortunately, as very little analytical details were reported, the validity of the results cannot be completely established [10]. 

Yeung et al. addressed the question of whether or not pull samples gave as good equations as samples measured on-line.47 The so-called add-back and process-stream samples were compared for statistical robustness in the equations they produced and their performance in predicting values in an on-line reaction. Materials such as biomass (optical density), protein, and RNA were measured by both techniques. 

It was found that fewer PLS factors were needed for process stream samples to yield a decent model. The correlation coefficients were stronger and the SEPs lower in every case. One example is protein add-back r2 = 0.891 using four PLS factors, whereas the process-stream samples enabled a three-factor PLS model to be generated with an r2 = 0.915. The respective SEP for each model was add-back = 4.351 process = 2.343. This paper seems to confirm the idea that samples taken during a process are more representative of that process. 

Since both the direct and phased approaches offer, at least in principle, equal promise for ultimate success (i.e., comprehensiveness and complete characterization), it is worthwhile to examine their relative resource requirements. Several studies were conducted with the objective of comparing the costs of direct and phased (with elimination of low priority streams) sampling and analysis approaches. (2,3] A number of processes were evaluated during these studies and the results for two unit operations — a limestone wet scrubber and full-scale low-Btu coal gasifier — are taken as examples. The scrubber involved seven feed or waste stream sampling sites. The gasifier contained 70 identifiable stream sampling points. The total estimated costs for both processes by both approaches are shown in Table I. 

Level 2 sampling programs are directed toward a more detailed representation of stream composition. They are not as inclusive as Level 1, in that resources are expended to improve information only on streams of a critical nature and on compound classes defined as present by Level 1 analysis. Level 2 sampling is optimized for specific compounds or classes of compounds contained in the streams sampled. Level 2 also provides a more quantitative description of the concentrations and mass flow rates of the various substances in the stream. Further, recommended procedures for compliance testing should be introduced into the program to ensure that the data acquired by the procedures selected for Level 2 sampling can be correlated with regulatory requirements. 

Measurement Variable A single reading (scalar) made on a sample. For example, the uabidity of a wastewater stream sample is a measurement variable. (In soBK pattern-recognition literature, the term feature is used in place of variaiile.)... 

Blue River Basin Colorado USA 10 stream samples Mining 13-180 (<63 pm) Apodaca, Driver and Bails (2000)... 

Stream sampling and flow sampling are terms usually reserved for the collection of sample increments from a free-falling stream of coal as opposed to the collection of increments from a motionless (stopped) conveyor belt. Coal that passes from one belt to another at an angle tends to become segregated because... 

ASTM D-6609. Standard Guide for Part-Stream Sampling of Coal. 

Samples ( <1 g) of mayfly nymphs, Ephemerella sp., were collected after the first application of aminocarb to Portage Brook by picking individual insects from moss on rocks picked from the stream. Samples (10-110 g) of resident brook trout, SaLvelimts fontinalis Mitchill, were sampled from Portage Brook after each aminocarb treatment using electrofishing equipment. Stomachs were removed from the fish and they were placed in plastic bags and frozen at -20°C until analyzed, as were mayfly nymph samples. 

Electrophoresis can also be conducted on-line, as an element of industrial process monitoring and/or control. In this case a slip-stream sample is usually withdrawn from a process vessel, diluted in a mixing tank to reduce the sample turbidity, and then pumped through an electrophoresis cell that is fitted with stop-flow solenoid valves. The flow is stopped for long enough to make an electrophoresis measurement and then resumed. The sampling can be either intermittent or continuous. An example is described in reference [265]). 

Semivolatile analytes in vapor-phase samples are often associated with particulate matter or aerosols that are collected on glass or quartz fiber filters in a flowing air stream.1 However some semivolatile analytes that have higher VPs, for example, 3,3 ,5,5 -tetra-chlorobiphenyl in Fig. 8.2, can slowly vaporize from a particle trapped on a filter in the flowing air stream, and will be lost unless captured by an in-stream sampling device. Small glass or metal tubes containing polyurethane foam are often used to capture vaporized semivolatile analytes. Other-solid phase adsorbents, which are described in the next section, are also used to trap semivolatile analytes vaporized from particulate filters. 

Figure 6a) inside the process stream, stream sampling, it is difficult... 

FIGURE 6 Flowing stream sampling (a) auger sampler [6] (h) constant-volume sampler [6] (c) diverter sampler (d) full-steam sampler. 

---