ASTM D3977-97(2007)

Suspended-sediment samples contain particles with a wide variety of physical characteristics. By presenting alternate approaches, these test methods allow latitude in selecting analysis methods that work best with the particular samples under study.

Sediment-concentration data are used for many purposes that include: (1) computing suspended-sediment discharges of streams or sediment yields of watersheds, (2) scheduling treatments of industrial and domestic water supplies, and (3) estimating discharges of pesticides, plant nutrients, and heavy metals transported on surfaces or inside sediment particles.

1.1 These test methods cover the determination of sediment concentrations in water and wastewater samples collected from lakes, reservoirs, ponds, streams, and other water bodies. In lakes and other quiescent-water bodies, concentrations of sediment in samples are nearly equal to concentrations at sampling points; in most instances, sample concentrations are not strongly influenced by collection techniques. In rivers and other flowing-water bodies, concentrations of sediment in samples depend upon the manner in which the samples are collected. Concentrations in isokinetically-collected samples can be multiplied by water discharges to obtain sediment discharges in the vicinity of the sampling points.

1.2 The procedures given in these test methods are used by the Agricultural Research Service, Geological Survey, National Resources Conservation Service, Bureau of Reclamation, and other agencies responsible for studying water bodies. These test methods are adapted from a laboratory-procedure manual and a quality-assurance plan.

1.3 These test methods include:

1.4 Test Method A can be used only on sediments that settle within the allotted storage time of the samples which usually ranges from a few days to a few weeks. A correction factor must be applied if dissolved-solids concentration exceeds about 10 % of the sediment concentration.

1.5 Test Method B can be used only on samples containing sand concentrations less than about 10 000 ppm and clay concentrations less than about 200 ppm. The sediment need not be settleable because filters are used to separate water from the sediment. Correction factors for dissolved solids are not required.

1.6 Test Method C can be used if two concentration values are required: one for sand-size particles and one for the combination of silt and clay-size particles. The silt-clay fraction need not be settleable.

1.7 These test methods must not be confused with turbidity measurements discussed in Test Method D 1889. Turbidity is the optical property of a sample that causes light rays to be scattered and absorbed; it is not an accurate measure of the mass or concentration of sediment in the sample.

1.8 These test methods contain some procedures similar to those in Test Methods D 1888 which pertains to measuring particulate and dissolved matter in water.

This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

1.9 This test method can be used only with sediments that settle under the influence of gravity. This test method is applicable to samples ranging from 0.2 to 20 L in volume, from 5 to 550 000 mg/L in sediment concentration, and having less than 35 000 mg/L in dissolved-solid concentration.

1.10 Test Method B can be used only on samples containing sand concentrations less than about 10 000 ppm and clay concentrations less than about 200 ppm. The sediment need not be settleable because filters are used to separate water from the sediment. Correction factors for dissolved solids are not required.

1.11 Even though a high-concentration sample may filter slowly, users should not divide the sample and use two or more filters. Instead, the entire sample should be filtered through one disk.

1.12 This test method covers concentration measurements of two particle-size fractions. The term fine fraction refers to particles small enough to pass through a sieve with 62 or 63-m apertures; coarse fraction refers to particles large enough to be retained on the sieve. The fine fraction need not be settleable. This test method is useful when large samples must be collected in the field but only small subsamples, typically 300 to 500 mL, can be shipped back to the laboratory.