PROGRAMS AND PLANS - Sampling and analysis of water-quality constituents associated with suspended solids March 18, 1971 QUALITY OF WATER BRANCH TECHNICAL MEMORANDUM 71.05 Subject: PROGRAMS AND PLANS - Sampling and analysis of water- quality constituents associated with suspended solids The Quality of Water Branch staff, in consultation with Division Research Hydrologists and others, is reviewing the state of knowledge of water-quality constituents associated with suspended solids, for the purpose of establishing guidelines for sampling and analysis of those constituents. These guidelines will be finalized within the next few weeks and promptly distributed to field offices. In the meantime, it seems appropriate to present the philosophy upon which the guidelines will be based, as an aid to District and Regional programming efforts. It is well known that certain water-quality constituents, especially some of the minor elements and organic compounds, are transported in streams either sorbed on or attached to suspended solids in large part. For such constituents, the traditional analysis of a "clear-water" sample only may present an erroneous picture of the concentration or load in the stream. This danger has been taken into account in our current procedures for analysis of water-suspended solids mixtures for "total" phosphorus, nitrogen, mercury, and pesticides. Similar procedures are required for the remainder of such constituents. Our objectives in sampling constituents associated with suspended solids should be: (1) to define the content of the constituent in both the dissolved and suspended phases; (2) to assess the relative significance of the two phases in the water sampled; and ultimately, (3) to define the source, behavior, and fate of each constituent. Objective 3 will be met largely through District and Division research projects, but an important contribution can be made by carefully collected basic data. In all circumstances, samples for the constituents under discussion should include the suspended phase. Whether it is necessary to sample all size fractions of suspended solids for all constituents of interest will be one of the questions considered in establishing sampling guidelines. Appropriate methods of extraction from the sampled solids will be considered also. At the present time, programming for water-quality constituents known to be significantly associated with suspended solids should be done with the following principles in mind: (1) Sampling should include the suspended phase as well as the dissolved phase. (2) An assessment of the relative loads of the constituent transported by each of the phases is usually desirable. For this purpose, the concentration of the solids in the water-solids mixture is needed in addition to the concentrations of the constituent of interest in each phase of the mixture. (3) Some knowledge of the content of the constituent in bed sediments should be obtained. Solids in the streambed at low flows contribute substantially to suspended solids at high flows. Furthermore, bed sediments can act as either a source or a sink for a number of constituents, thus exerting control on constituent concentrations in the water even when immobile. Consideration of the above principles, along with the expected use of the data, will provide a firm basis for preliminary planning of data-collection activities related to constituents associated with suspended solids. W.H. Durum Chief, Quality of Water Branch WRD Distribution: A, FO-L, S