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SAMPLE SPUnERS Two types of splitters are available for compositing and splitting, the cone (decaport) and the churn. The cone splitter is a positive pour-through device that composites and splits the sample in one step. A funnel-shaped reservoir receives the sample and directs it into a splitting chamber. The splitting chamber is a solid block with 10 outlet ports (placed at 360 intervals around the circumference and drilled at 450 angles) that meet in the center to form an inverted cone. The resulting configuration splits samples into 10 equal subsamples. Tests have shown that the cone splitter can split sample volumes as small as 250-mL into 10 equal subsamples, each subsample volume within an accuracy of 5 percent (see OWQ technical memorandum 80.17, appendix A). Tests of the distribution characteristics of the cone splitter (Capel and Nacionales, 1993) indicate that, even with a slight difference in the volume ofthe subsamp1es, the relative percent of sediment mass to sample volumes are within 3 percent at each port, and the particle-size distribution of the fmer than coarse-sand fraction is within 5 percent. Tests indicate that the chum splitter does not produce equivalent subsamples for sediments coarser than 63 mm. There is concern that a metal spring in the spigot may contaminate the samples for trace- element analyses (see OWQ technical memorandum 94.09, appendix A). The churn should be used only as a compo siting vessel for dissolved inorganic samples withdrawn from the top (see OWQ technical memorandum 94.13, appendix A). The chum is limited in sample volume and currently is available only in a plastic version. Based on all available information, the Telfon cone splitter is the best available equipment for compo siting and splitting whole water samples for analyses of major ions, nutrients, trace elements, pesticides, and sediment. It is presently the only alternative for splitting pesticide and sediment samples. However, when methanol is used for cleaning the cone, it is not suitable for splitting samples for total organic compounds (TOC), dissolved organic compounds (DOC), and volatile organic compounds (VOC). Those samples must be collected separately, directly from the stream, to avoid contamination. The churn is suitable for compositing dissolved inorganic constituent samples, but NA WQA studies seldom sample for these constituents in isolation. Thus, for the multipurpose needs of NA WQA, the use of the Teflon cone splitter is required. FILTER SYSTEMS Some samples collected for inorganic constituents and most samples for organic constituents must be filtered in the field. Filtration equipment and procedures vary slightly depending on the type of constituents the filtration process is intended to isolate. The equipment basically consists of a variable-speed, battery-operated pump fitted with a peristaltic pump head or a metering pump that forces the sample through Tygon, silicon, or Teflon tubing into a filter assembly. A capsule filter system with an effective pore size of 0.45 )lIll is used for filtering inorganic constituents. The filter type used to process the dissolved organic-carbon samples has the same pore size, but uses a stainless-steel pressure filter unit to hold a 47-mm-diameter silver filter. The plate filter used for organic-compound analyses is 142 mm in diameter and is made of glass fiber with a pore size of 0.7 )lIll. 12 Collecting and Processing Stream-Water Samples for the National Water-Quality Assessment Program