National Academies Press: OpenBook

Geochemistry and the Environment: Volume I: The Relation of Selected Trace Elements to Health and Disease (1974)

Chapter: 'SAMPLING, SAMPLE PREPARATION, AND STORAGE FOR ANALYSIS'

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Suggested Citation:"'SAMPLING, SAMPLE PREPARATION, AND STORAGE FOR ANALYSIS'." National Research Council. 1974. Geochemistry and the Environment: Volume I: The Relation of Selected Trace Elements to Health and Disease. Washington, DC: The National Academies Press. doi: 10.17226/20136.
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Page 89
Suggested Citation:"'SAMPLING, SAMPLE PREPARATION, AND STORAGE FOR ANALYSIS'." National Research Council. 1974. Geochemistry and the Environment: Volume I: The Relation of Selected Trace Elements to Health and Disease. Washington, DC: The National Academies Press. doi: 10.17226/20136.
×
Page 90
Suggested Citation:"'SAMPLING, SAMPLE PREPARATION, AND STORAGE FOR ANALYSIS'." National Research Council. 1974. Geochemistry and the Environment: Volume I: The Relation of Selected Trace Elements to Health and Disease. Washington, DC: The National Academies Press. doi: 10.17226/20136.
×
Page 91
Suggested Citation:"'SAMPLING, SAMPLE PREPARATION, AND STORAGE FOR ANALYSIS'." National Research Council. 1974. Geochemistry and the Environment: Volume I: The Relation of Selected Trace Elements to Health and Disease. Washington, DC: The National Academies Press. doi: 10.17226/20136.
×
Page 92
Suggested Citation:"'SAMPLING, SAMPLE PREPARATION, AND STORAGE FOR ANALYSIS'." National Research Council. 1974. Geochemistry and the Environment: Volume I: The Relation of Selected Trace Elements to Health and Disease. Washington, DC: The National Academies Press. doi: 10.17226/20136.
×
Page 93
Suggested Citation:"'SAMPLING, SAMPLE PREPARATION, AND STORAGE FOR ANALYSIS'." National Research Council. 1974. Geochemistry and the Environment: Volume I: The Relation of Selected Trace Elements to Health and Disease. Washington, DC: The National Academies Press. doi: 10.17226/20136.
×
Page 94
Suggested Citation:"'SAMPLING, SAMPLE PREPARATION, AND STORAGE FOR ANALYSIS'." National Research Council. 1974. Geochemistry and the Environment: Volume I: The Relation of Selected Trace Elements to Health and Disease. Washington, DC: The National Academies Press. doi: 10.17226/20136.
×
Page 95
Suggested Citation:"'SAMPLING, SAMPLE PREPARATION, AND STORAGE FOR ANALYSIS'." National Research Council. 1974. Geochemistry and the Environment: Volume I: The Relation of Selected Trace Elements to Health and Disease. Washington, DC: The National Academies Press. doi: 10.17226/20136.
×
Page 96

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Rept. No. NASA·TN·D-2598. National Technical Information Service, Sprqfleld, Va. p. 19. Hambidge, K. M. 1971. Use of argon atmosphere in emission spec· trochemical determination of chromium in biological materials. Anal. Chern. 43:103-107. Mertz, W. 1969. Chromium occurrence and function in biological systems. Physiol. Rev. 49(2):163-239. Pickett, E. E. 1967. Current capabilities in analysis of trace sub- stances: Flame photometry and atomic absorption. Proceedings of the First Annual Conference on Trace Substances in Envir· onmental Health, July 10-11, 1967, D. D. Hemphill (ed) . Univenity of Missouri, Columbia. pp. 29-36. Savory, J., P. Mushak, N. 0 . Roszel, and F. W. Sunderman, Jr. Analytical Methods 89 1968. Determination of chromium in serum by gas chroma· tography. Fed. Proc. 27:777. Sievers, R. E., J. W. CoMally, and W. D. Ross. 1967. Metal analysis by gas chromatography of chelates of heptafluorodimethyl· octanedione. J. Gas Chromatogr. 5 :241-247. Silverman, L., and J. F. Ege, Jr. 1947. A rapid method for determi- nation of chromic acid mist in air. J. Ind. Hyg. Toxicol. 29:136- 139. Silverman, L., and J . F. Ege, Jr. 1949. Chromium compounds in gaseous atmosphere. U.S. Patent 2483108. Woehlbier, W., M. Kirschgessner, and W. Oelschlager. 1959. The content of macro and microelements in red clover and luzerne. Arch. Tierem. 9:194-201.

XI Sampling, Sample Preparation, and Storage for Analysis GEORGE H. MORRISON, Co-Chairman JAMES 0. PIERCE, Co-Chairman William H. Allaway, Ernest E. Angino, Helen L. Cannon, Roger Jorden, Joe Kubota, Herbert A. Laitinen, Hubert W. Lakin After considering the various analytical methods for the ele- ments of concern to the Workshop, the Methods and Sam- pling Work Group surveyed the status of sampling, sample preparation and storage, standards, and baseline measure- ments, emphasizing the special considerations for each of the environmental media. SAMPLING The greatest sources of error in environmental studies are usu~y in the sampling steps; careful attention must there- fore be given to an effective and efficient field sampling program. General sampling designs have been developed for environmental surveys and can serve as models for future programs (U.S. Geological Survey, 1972). Sampling plans involving large regions begin with a decision concern- ing the materials to be investigated from the lithosphere, hydrosphere, biosphere, or atmosphere. Increased detail can be ascertained from successive stages of sampling to a point determined by the demands of the problem or by the eco- nomics of the situation. The overriding concern in sampling must be that the sample set accurately reflects the variations in the material being sampled. Samples for laboratory assays may be se· lected on the bases of the capabilities of the various ana- lytical methods-precision and accuracy, sensitivity, time considerations, costs, single versus multi-element analyses- 90 but special consideration must be given to specific media sampled. For example, greater homogeneity is often en- countered in natural waters or in body fluids than in soils or tissues of organisms. Such characteristics always deter- mine the sample sizes necessary to measure the variation accurately. The specific technique employed must be one capable of handling the analytical sensitivity required. Great diversity in techniques and sampling procedures exists. Although such a variety of approaches often leads to more profound interpretations of the data, efforts for this study should be directed toward an evaluation of such techniques so that a greater degree of reliability can be reached, which will allow interlaboratory comparisons of samples. This suggestion should not be construed to imply the formulation of standard methods. The following sections treat some of the specific aspects of sampling of various general types of materials. Soil Sampling The study of soils is important in defining geographic areas of low or high trace element concentrations for use in eval· uating plant and animal toxicity, but it may be equally im· portant in evaluating soils for such uses as waste-disposal sinks. It must be remembered that samples collected for one study may be totally unsuited for another. Some prin· ciples and procedures for the selection and collection of

soU samples for laboratory studies of trace elements were recently reviewed by Kubota ( 1972). General Principles and Procedures It is essential to recog- nize that soils are complex systems resulting from weather- ing processes. A soil profde reflects the magnitude of local weathering effects. Changes occur with depth in the distri- bution of organic matter, in texture and structure, and clay contents. Some theoretical consideration of trace element sources, their redistribution by transport and deposition, and their behavior during weathering processes is essential in the eval- uation of trace elements in soils. Conceptual models of soils then need to be translated to real soils on landscapes that have properties important to a particular study. Soil survey maps are a means of locating potential sampling sites of specific soils. Natural soils rarely have sharply defmed boundaries on a landscape and it is therefore necessary to check the actual soil to determine if it is suitable for study. Smnpling and Proceuing Surface samples of soils are usu- ally taken where information is needed about the role of soils on the trace element composition of shallow-rooted plants. Studies of trace element mobility and redistribution, whether from natural weathering or pollution, often re- quire the collection of samples to greater depth. Although only a few grams are usually needed for laboratory de- terminations, a sample of about 5-8 lb is desirable. Samples are best collected from one face of a small hole. Because sampling tools are possible sources of trace metals, the use of a clean spade is preferable to the use of a soil auger, and-unless moist samples are needed-the samples collected can be placed in a clean cloth bag. For studies of most trace elements, it is necessary to break down soil aggregates. Riffle samplers may be used to reduce the amount of soil that might be fine-ground for trace element determinations. Sieves made of sUk bolting cloth or nylon are free of trace metals and are useful for sieving ground-soil materials. Expression of Data Results of trace element analysis are commonly given as parts per million, air-dry or oven-dry weight of soil. The fact that plants grow in a volume of soil sometimes requires evaluation of data on a soil-volume basis. If such evaluations are anticipated, measurements of bulk or apparent soil density are essential. Bulk densities of soU range from about 0.2 g/cm3 for peaty soils to 1.7 g/cm3 for highly indurated soils. Plant Sampling Crop-management practices, including fertilization and ap- plications of herbicides and pesticides, have important ef- Sampling, Sample Preparation, and Storage for Analysis 91 fects on many crop plants. Processing and storage of foods for humans, in particular, often result in drastic changes in trace element concentrations naturally present in plants. Some pertinent factors concerned with plant sampling are discussed below. Number of Individual Pillnts Needed to Obtain a Sample Representative of the Soil on Which Pillnts Were Grown The species of plants collected and studied often differ as widely as do the kinds of soils on which they are grown. This problem was studied by Lazar and Beeson ( 1956) on the Atlantic Coastal Plain. Six soil areas nearly chemically uniform and representing four soil series were used. Within each soil area, the individual plants were tagged and samples were collected from them over a 2-year period. At least five individual grass plants were needed to characterize the co- balt and copper status of soils when a grass (Andropogon glomeratus (Walt.)] was used, but the same informa- tion could be obtained by using leaves of two black· gum plants (Nyssa sylvatica Marsh. var. bijlora (Walt.) Sarg.] . Later, tests using leaves of black gum (Kubota and Lazar, 1958; Kubota et aL, 1960) showed that use of this plant can distinguish the cobalt concentration of widely different soils, as it reflects concentrations of total, as well as extractable, forms of soil cobalt. Error estimates for un- equal numbers of plant samples from unequal numbers of sampling sites can be obtained with the use of pooled stan- dard error (Kubota, 1964). Time of Sampling Studies by Beeson and MacDonald (1951) of the effect of sampling dates on trace element concentra- tion of alfalfa in New York showed that manganese, cobalt, and iron increase with the growing season. Marked initial decreases in trace element concentrations, however, were later observed by Loper and Smith (1961) in Wisconsin, also using alfalfa. The differences could not be easily at- tributed to soils because the soils in the two studies were morphologically similar and were both formed in calcareous till. When effects of high rates of fertilization used in the Wisconsin study (Loper and Smith, 1961) were reduced with cropping, the seasonal changes were essentially the same as those of the New York study. Kind of Pillnts In terms of trace element concentration, plants appear to be species-distinct. Browse plants, herba- ceous plants, sedges, and grasses grown in Alaska were all studied where they were growing in the surficial peaty mantle (Kubota eta/., 1970). Marked species effects on the concentration of molybdenum were observed among species of common forage plants in Nevada (Kubota et al., 1961). Over a concentration range of 2-350 ppm (dry wt) of molybdenum, clovers took up more molybdenum than did grasses and sedges. In a New England study, ladino clover and red clover were found to take up nearly the same

92 THE RELATION OF SELECTED TRACE ELEMENTS TO HEALTH AND DISEASE amount of cobalt, but both took up less cobalt than did alsike clover (Kubota, 1964). It has been shown that effects of species differences, as reflected by comparisons of se- lenium in alfalfa, clovers, bromegrass, and timothy are negligible at levels of 0.1 ppm or less of selenium (Ehlig et al., 1968). Parts of Plants The necessity for sampling specific parts of plants to identify trace element deficiencies or toxicities affecting growth of agricultural crops is well recognized. A comprehensive review was prepared, for example, by Tanaka and Yoshida (1970) to diagnose trace element deficiencies and toxicities using specific parts of the rice plant. Increases in trace element concentration with plant growth often re- sult from increases in leaves of forage plants but not of stems or petioles (Beeson and MacDonald, 1951 ). Patterns of trace element changes evident in common forage plants also may be evident in browse plants important for game animals (Kubota et al., 1970). Contamination of Plant Samples Studies by Arkley et al. ( 1960) showed that trace elements carried in peat dust and deposited on plants are easily removed by washing, but those applied by sprays are not. Absorption of trace ele- ments through leaf surfaces was noted as a factor. Surface absorption of trace elements by plants was also observed by Lagerwerff(l971) to be an important factor in increases of cadmium, zinc, and lead in the radish plant. Increases caused by absorption of trace elements on leaf surfaces may also be enhanced with drying and changes in leaf- surface characteristics with plant maturity. Sampling of Fruits and Vegetables Sampling techniques and sample processing were examined some years ago in the study of vitamin levels in turnip greens (Southern Coopera- tive Group, 1951 ), but no systematic study has been made of sampling of fruits and vegetables for trace elements. More attention has been paid to food processing and its effect on changes in trace element composition of fruits and vegetables. Losses of zinc and manganese from spinach, beans, and tomatoes in canning, as well as gains in zinc and manganese in canned beets, have been observed by Schroeder ( 1971 ). Peeling of some common fruits and vegetables has been found to result in losses of chromium, copper, and zinc, as well as lead (Cannon et al., 1972). Sampling of Animal and Human Tissues Two general types of sampling are prevalent in experiments with animals and humans. In the first type the investigator uses experimental animals, such as rats, which can be sacri- ficed as necessary and dissected to produce whatever spe- cific tissues are desired. Here replication of animals is com- mon, total weight of samples is not limiting, and the investigator is generally present during the sampling. The major decisions involve selection of the specific tissue that will, on analysis, yield the most important data. In the second type of experiment the animal or person being investigated must remain alive and experience mini- mum discomfort. Here the number of individuals is usu- ally limited, and the investigator receives the samples from a nurse, technician, or other person who is generally not a part of the research team. In these instances, blood or serum, urine, hair, and perhaps needle biopsy materials are the tissues that are generally available. In this type of sampling, decisions include the kind of tissue or tissues most useful in charac- terizing the status of the subject with respect to the element in question and whether the data on environment, diet, health or disease, water supply, etc., are adequate for the purposes of the experiment. Very frequently the investi- gator is forced to use less than adequate samples rather than do nothing. Unfortunately, data like these tend to become chiseled on tablets of stone in the biomedical literature. Another decision in sampling under these conditions concerns contamination of samples during sampling. Blood samples drawn with stainless-steel needles may be unsatis- factory for chromium, and those drawn through rubber tubing may be unsatisfactory for zinc. Plastic urine con- tainers may irreversibly absorb heavy metals. It would be useful for some central organization to sponsor the pro- duction and distribution of syringes, blood needles, and containers for blood and urine that would be suited to trace element studies on samples obtained from humans and domestic animals. A second desirable, but perhaps un- attainable, feature would be the establishment of a uni- form terminology suited to coding, for describing the environment, health and disease, diet, etc., of the subject sampled. Sampling of Air The methods employed for the removal of metallic com- pounds from air are quite diverse, but consist essentially of the following components: a filter holder, a filter media, a flow-measuring device or a volume totalizer such as a dry- gas meter, a timing device to record length of sampling time, and a pump. Each of these components needs to be considered individually and collectively for potential sources of error. A flow-rate device, such as a rotameter, must be used in conjunction with a mechanism for recording the length of time of sample collection to allow for calculation of total quantity of air passed. This is a major source of error in the sampling process because a plot of flow rate versus time is not a linear relationship caused by the load- ing of particulate matter on the filter device. Figure 9 illustrates the assumed nature of flow versus time by this

w 1- <( a: 3: 0 ...J LL 0 TIME FIGURE 9 The assumed nature of flow versus time. procedure. The detennination of volume of air sampled is calculated by averaging the initial (F 1) and fmal (F 2 ) flow rates: F 1 ; F 2 X length of time = volume of air sampled. Actually, the flow rate through a fdter subjected to particu- late buildup follows Figure 10. The shape of the curve de- pends on the actual loading characteristics, which are the result of the total particulate burden of the air at any time t. It thus becomes clear that this is not a preferred method of estimating total volume of air sampled. A volumetric totalizer, such as a dry-gas meter, is not subject to errors of the extent described for the previous method and use of it probably represents the best method of measurement of air flow. However, this method will lead to incorrect estimates of the total volume unless certain pre- cautions are taken. The major error lies in the change in temperature of the air being sampled and the resultant w 1- <( a: :: 0 ..J LL t TIME FIGURE 10 Flow rate through a filter subjected to particulate buildup. Sampling, Sample Preparation, and Storage for Analysis 93 vacuum head produced between the fdter head and the pump. If a vacuum recorder is placed in the airline to re· cord continuously the pressure drop on the upwind side of the meter, appropriate mathematical corrections can be made. Another source of difficulty lies in the selection of a filter medium: Because the particle-size distribution of suspended particulate matter in air ranges from submicron to very large, the experimental design must take this factor into account . Any study designed to investigate the possible relation· ships between heavy metals in air and health or disease must employ the use of filter media that will have a high collection efficiency for subrnicron particles, because these sizes (probably up to 8 microns) are respirable by man and animals. The foliar deposition and intake into the plants are also significant for these smaller-size particles. The analysis of exposed filter paper poses another, usually unrecognized, problem. Pierce and Meyer (1971) using lead as a model have shown that metal particles are not uni· forrnly distributed over the surface of the fdter itself. This is presumably true of all airborne particles, making it neces- sary to ash the entire fdter if reliable data are to be obtained. These same studies suggested that, if a portion of the fdter is to be retained for future reference, the best estimate of total quantity is the random selection of three 1 ()..percent segments, separately analyzed and averaged. The other ele· ments of a particle sampling apparatus do not contribute in a significant way to sampling errors. Again, as for the other sampling problems, there is a need for standardiza- tion and more research on the design of sampling pro- cedures. Water Sampling The principal problems consist of obtaining a representative sample, avoiding contamination, and adequately separating dissolved and particulate phases. Very shallow streams, only a few meters wide, that are well mixed laterally as well as vertically may be sampled by dipping at mid-depth. Larger streams may require the compositing of numerous samples according to some meaningful system. Each cross-section sample needs to be taken in such a way that it is velocity· integrated over the distance from the water surface to the water-bed interface. In larger streams the sampling is done from a bridge, cable, or boat. Impoundments are frequently thennally stratified and should be sampled as a function of depth. In stratified water bodies, at least one sample should be taken near the water surface and one from below the thennocline. The sample-bottle holders currently in use for sampling streams should have the brass intake nozzle replaced with one made of Teflon and the rubber gasket replaced with one made of silicone. It is important that the sampler be immersed in a flowing stream to wash off dissolved metals

94 THE RELATION OF SELECTED TR:ACE ELEMENTS TO HEALTH AND DISEASE before inserting the sample bottle. With all plastic filters, filtration is best done in the field or as soon as practical. The membranes used for filtration should have a nominal pore size of no more than 0.1 J.l.. The actual particle size cutoff is unknown because, as sediment collects on the membrane, it generally filters more effectively than does the membrane itself. Water samples are best filtered using stainless-steel filters in conjunction with silver membranes for determination of dissolved and particulate organic carbon. The dissolved and particulate fractions should then be chilled to 4 C and ana- lyzed as soon as possible. It is desirable that the trace ele- ment analyses be performed immediately. Sample preserva- tion by acidification is required for some trace elements, but data are not available for most trace elements. Freezing may be a suitable preservation technique, but it has not been adequately tested to date. Sampling of Rocks Rocks are heterogeneous materials containing many mineral components in varying crystal size. The trace elements of interest may be minor impurities in major minerals of the rock or even major constituents of minor minerals. Conse- quently, both field and laboratory errors are common during sampling. The sampling methods must be designed to reduce the sampling error to a level commensurate with or less than the effects being studied. Often only 0.1 g of a 165 kg sam- ple is used for the actual analysis; thus, the sample must be ground to a sufficiently fine powder to yield an acceptable number of particles of each component of the heterogene- ous material. This process introduces contamination, which must be minimized during the sample preparation. SAMPLE PREPARATION AND STORAGE Minimum pretreatment of samples for trace analyses is an obvious goal. Nondestructive or direct methods are the most desirable because they minimize contamination and loss problems. Because of the complexities of the materials encountered, preconcentration steps are often required to attain adequate sensitivity, and separation steps may be required to eliminate interfering species. Pretreatment steps may include separation of artifacts, drying, sterilization, homogenization, ashing, dissolution, and isolation of spe- cies-according to the specifics of the samples and of the desired analytical information. A guiding principle here is the minimization of pretreatment steps. It is often essential to archive selected samples for analy- ses of additional constituents later or for comparison of data. The goal of any storage technique is the maintenance of sample integrity. Considerations of the container material are necessary regarding adsorption from solution on the walls, leaching from the walls, loss through volatilization, degradation through photochemical or biological activity, and other factors. At present, such relatively inert ma- terials as quartz, Teflon, polyethylene, hard glass, and so forth, have both attractive and undesirable attributes. An overriding consideration may be the duration of storage; short-term requirements clearly differ from those of longer periods. The systematics of storage have not as yet been ade- quately explored. The increasing need for baseline studies (see below) demands an evaluation of currently used stor· age methods. There are difficulties in predicting future disposition of stored samples, whether it be analysis of yet unconsidered species or the extension of present assays through enhanced capabilities of analyses. Nonetheless, the urgency to maintain an available supply of baseline materials demands an immediate consideration of this problem. STANDARDS Analytical methods should be validated through the use of certified standards where these are available. In their ab- sence, independent, generally accepted analytical tech- niques should be used on a subset of samples to obtain a measurement of accuracy. At present, there is a great need for additional standards representative of the various types of materials encountered in environmental studies, i.e., water, air, plant materials, and animal materials including hair, urine, blood, plasma, liver, and muscle. The U.S. National Bureau of Standards recently has made available certified samples of orchard leaves ( 1973) and bovine liver (1972) for plant and animal analyses, respectively. Table 32 summarizes the status of certifica- tion for the elements considered in this report . No values are given so far for iodine, tellurium, and molybdenum in orchard leaves, and the values for fluorine, lithium, and chromium are tentative. In the case of the bovine liver, values are not yet available for iodine, fluorine, lithium, tellurium, and chromium. The Federal Water Quality Administration, now a part of the Environmental Protection Agency, has made available a number of standard water samples for a few elements. Rock standards are available from the U.S. Geological Survey and include granites, basalts, and carbonates. In general, these are usable in soil research. However, there are needs for soil standards where the form of the ele- ment in question is important. There is a complete lack of standards for whole blood, plasma, urine, muscle, and hair. Federal agencies should be encouraged to extend the number of standards to encompass the wide variety of rna· terials encountered in environmental studies. An alternate approach, where certified standards are not available, is the use of secondary laboratory standards,

TABLE 32 Biological Standards of the U.S. National Bureau of Standards Orchard Leaves Flement (SRM-1571), ppm Iodine Fluorine (4) Lithium (14) Ouomium (2.3) Cadmium 0.11 :1:0.02 Zinc 2S :1: 3 Lead 45:1: 3 Selenium 0.08:1:0.01 Tellurium Copper 12 :t: 2 Molybdenum NOTE: Values in parentheses are tentative. SRM standard reference material Bovine Uver (SRM-1577), ppm 0.28 :1: 0 .04 1DSSMS 0.27:1:0.04 ATA 0.25 :t: 0.06 POL 126 :1: 111DSSMS 127 :t: 6 NAA 133 :t: 2 ATA 0.36 :t: 0 .08 lDSSMS 0.31 :t: 0.08 POL 1.12 :1: 0.04 NAA 1.11 :1: 0.04 lDSSMS 184 :t: 121DSSMS 193:1: 8 ATA 193 :t: 3 IDMS 3.23 :t: 0.26 IDSSMS IDSSMS isotope dUution-spark-source spectrometry AT A atomic absorption POL polarocraphy NAA neutron-activation analysis IDMS isotope dUution-mua spectrometry materials analyzed by a group of laboratories on an in- formal basis. A listing of such samples would be most beneficial, and a clearinghouse might be established under the aegis of a national agency. BASELINE MEASUREMENTS Changes in environmental compositions may be brought about either by the activities of man or by natural pro- cesses. Recognition of the history of such changes and the identification of cause may evolve from appropriate base- line studies. An appreciation of human society as a geological agent Sampling, Sample Preparation, and Storage for Analysis 95 may be found in Table 33, where movement of materials in the sedimentary cycle are compared with that involving man. Mobilization rates of materials as a result of agricultural, industrial, or social usages are within an order of magnitude or two of those in the weathering cycle. Because most of man's activities are localized to the mid-latitudes of the northern hemisphere, they may well rival geological phe- nomena in these areas. Records of trace element compositions in past times may be found in sedimentary columns, in fossilized ma- terials, or in preserved biological samples. The assignment of a reliable time of accumulation in the sample is essen- tial. Table 34 illustrates the techniques employed in the establishment of baseline values from historical records. Our knowledge about man's role in affecting trace ele- ments in the environment is still poorly defmed. Extensive efforts should be mounted to develop our information base on the natural occurrences of the elements considered in this report for both biological and geological domains. TABLE 33 Movement of Materials from the Continents to Geospheres Cause of Movement Natural processes other than man: Suspended load of rivers carried to oceans Dissolved load of rivers carried to oceans Glacial solids carried to oceans Soil and rock debris entering atmosphere and involved in global movements Volcanic ash entering atmosphere Mercury volatilizing to atmosphere Lead in rivers carried to oceans Materials mobilized by man's activities: Total amount moved about environment Carbon and fly ash to atmosphere from fossil-fuel burning Mercury to atmosphere and natural waters Lead to atmosphere from combustion of lead alkyls in internal combustion engines SOURCE: Goldberg (1972). Movement, 1014 g/yr 180 40 30 1-5 l.S 0.00025-o.0015 0.00015 30 0.25 0.00003 0.00025 TABLE34 Changes in Environmental Compositions with Time Geosphere Elements Record Time Parameter References Atmosphere Pb, S,Se, Hg Glacial strata 110Pb dating (Murozumi eta/., 1969; Koide and Goldberg, 1971; Weisseta/., 197la,b) Lake water Pb, Hg, other Sediments heavy metals Oceans Hg Museum fish Collection date Ca,Mg Oyster shells Paleontological record (Lowenstam, 1964) Biosphere (birds) Hg Bird feathers Collection date (Berget al., 1966) .. _-

96 THE RELATION OF SELECTED TRACE ELEMENTS TO HEALTH AND DISEASE SUMMARY A critical stage in studies involving the environment in rela- tion to health and disease is the obtaining of reliable and relevant analytical data. Sampling The greatest source of error in analysis _usually arises in the sampling step. Therefore, considerable attention must be given to evaluating the variety of sampling techniques such that the sample set will accurately reflect the material being sampled. Sample Preparation Pretreatment may include such diverse operations as sepa- ration of artifacts, drying, sterilization, homogenization, ashing, dissolution, preconcentration, or isolation of species. Minimum pretreatment of samples for trace analysis is an obvious goal to minimize contamination and loss. Storage It is often essential to archive selected samples for future studies involving either the analysis of additional constit- uents or the comparison of data. The goal of any storage technique is the maintenance of sample integrity. The increasing need for baseline studies demands an evaluation of storage methods in use at present. Standards Analytical methods should be validated through the use of certified standards, where available. In their absence, inde- pendent analytical techniques should be used on the same samples for comparative purposes. There is a great need at present for additional standards representative of water, air, plant materials, and animal ma- terials including hair, urine, blood, plasma, and muscle. Baseline Measurements Changes in trace element concentrations in the environment may be brought about by the activities of man or by other natural processes. Recognition of the history of such changes and the assignment of cause may evolve from base- line studies appropriately made. Extensive efforts should be mounted to develop our information base on the natural occurrences of the elements in both biological and geo- logical domains. RECOMMENDATIONS Because of the wide dispersion of information on the sam- pling and analysis of materials of environmental interest, it is recommended that a series of short monographs on the guiding principles and recommended procedures be pre- pared to facilitate interdisciplinary communication. Mono- graphs should be prepared by appropriate authorities on the following topics: 1. field sampling, 2. standards, 3. baseline studies, 4. storage of samples, 5. analytical methods and techniques, and 6. experimental design. This series could be produced under the auspices of the NAS-N RC and made available to experienced investigators and those just entering the field. There is an urgent need to extend the availability of stan- dards for calibration of analytical methods. A survey should be made to determine the most needed standards, and the appropriate federal agencies should be encouraged to de- velop them. REFERENCES Arkley, T. H., D. N. Munns, and C. M. Johnson. 1960. Preparation of plant tissues for micronutrient analysis: Removal of dust and spray contaminants. J. Agric. Food Chern. 8:318-321. Beeson, K. C., and H. A. MacDonald. 1951. Absorption of mineral elements by forage plants: The relation of stage growth to the micronutrient element content of timothy and some legumes. Agron. J. 43:589-593. Berg, W., A. Johnels, B. Sjostrand, and T. Westermark. 1966. Mercury content in feathers of Swedish birds from the past 100 years. Oikos 17:71-83. Cannon, H. L., C. S. E. Papp, and B. M. Anderson. 1972. Problems of sampling and analysis in trace element investigations of vege- tation. Ann. N.Y. Acad. Sci. 199:124-136. Ehlig, C. F., W. H. Allaway, E. E. Cary, and J. Kubota. 1968. Dif- ferences among plant species In selenium accumulation from soils l!)W in available selenium. Agron. J. 60:43-47. Goldberg, E. D. 1972. Man's role in the sedimentary cycle. Nobel Symposium 20. Koide, M., and E. D. Goldberg. 1971. Atmospheric sulfur and fossil- fuel combustion. J. Geophys. Res. 76:6589. Kubota, J. 1964. Cobalt content of New England soils in relation to cobalt levels in forages for ruminant animals. Soil Sci. Soc. Am. Proc. 28:246-251. Kubota, J. 1972. Sampling of soils for trace element studies. Ann. N.Y Acad. Sci. 199:105-117. Kubota, J., and V. A. Lazar. 1958. Cobalt status of soils of south- eastern United States: II. Ground-water podzols and six geo- graphically associated soils groups. Soil Sci. 86:262-268. Kubota, J., V. A. Lazar, and K. C. Beeson. 1960. The study of co- balt status of soils in Arkansas and Louisiana using the black

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