United States Environmental Protection Agency Environmental Monitoring Systems Laboratory Las Vegas, NV 89193-3478 Research and Development EPA/600/S4-90/023 Oct. 1991 EPA Project Summary Handbook of Methods for Acid Deposition Studies, Laboratory Analyses for Soil Chemistry L. J. Blume, B. A. Schumacher, P. W. Shaffer, L. A. Cappo, M. L. Papp, R. D. Van Remortel, D. S. Coffey, M. G. Johnson, and D. J. Chaloud This handbook describes methods used to process and analyze soil samples. It Is Intended as a guidance document for groups Involved In acid deposition monitoring activities similar to those implemented by the U.S. Envi- ronmental Protection Agency's Aquatic Effects Research Program, a part of the National Acid Precipitation Assessment Program. Much of the methodology presented in this handbook Is based on existing soil survey protocols; however, most of the methods were modified to meet the particular needs of the Direct/ Delayed Response Project. These modi- fications Include specifications for sample size, quality assurance and qual- ity control samples, soil-to-solution ra- tios, extraction times, extraction appara- tus, and holding times. The handbook also delineates methods that were used to make the following laboratory deter- minations: rock fragments, bulk density, pH, organic matter, air-dry moisture, partical size analysis, cation exchange capacity, exchangeable cations in am- monium acetate, exchangeable cations In calclumchloride for lime and aluminum potential, exchangeable acidity, ex- tractable Iron, aluminum, silicon, and sulfate, sulfate adsorption Isotherms, and total carbon, nitrogen, and sulfur. This Project Summary was developed by the EPA's Environmental Monitoring Systems Laboratory, Las Vegas, NV, to announce key findings of the handbook that Is fully documented In a separate handbook of the same title (see Hand- book ordering Information at back). Introduction Concern about the effects of acidic depo- sition on the Nation's surface water re- sources led the U.S. Environmental Pro- tection Agency (EPA) to initiate research in the field in the late 1970s. Early research, focusing on a diversity of potential effects, provided insight into those research areas which were considered central to key policy questions. Recognizing the need for an integrated, stepwise approach to resolve the issues, EPA implemented the Aquatic Effects Research Program (AERP) in 1983 with its present structure, focus, and ap- proach. The AERP is a major component of the National Acid Precipitation Assessment Program's (NAPAP) Aquatic Effects Re- search Task Group 6, a cooperative effort of nine federal agencies tasked with address- ing important policy and assessment questions relating to the acidic deposition phenomenon and its effects. The Direct/Delayed Response Project (DDRP) is one of the major component projects within the AERP. Its principal mandate is to make regional projections of future effects of sulfur deposition on long- term surface water chemistry based on the best available data and most widely ac- cepted hypothesis of the acidification pro- cess (Church et al., 1989). Specific objec- tives of the DDRP are: To describe the regional variability of soil and watershed characteristics. To determine which soil and watershed characteristics are most strongly related to surface water chemistry. To estimate the relative importance of key watershed processes in moderating re- gional effects of acidic deposition. ------- To classify a sample of watersheds with regard to their response characteristics to inputs of acidic deposition and to ex- trapolate the results from this sample of watersheds to the DDRP study regions. Scope of Handbook The Handbook of Methods for Acid Depo- sition Studies, Laboratory Analyses for Soil Chemistry describes methods used to pro- cess and analyze soil samples. These procedures are based on methods used during the three soil surveys comprising the DDRP. Most of the methods were based originally on methodologies employed by the U.S. Department of Agriculture/Soil Con- servation Service (USDA/SCS), including methods described in the National Soils Handbook (USDA/SCS, 1983), Soil Survey Manual (USDA/SCS, 1951; supplement 1962), Field Study Program Elements to Assess the Sensitivity of Soils toAcidDepo- sition Induced Alterations in Forest Produc- tivity (Fernandez, 1983), Procedures for Collecting Soil Samples and Methods of Analysis for Soil Surveys (USDA/SCS, 1972), Methods of Soil Analysis, Part 1 (Klute, 1986) and Part2(Pageetal., 1982). Soil Taxonomy (USDA/SCS, 1975), Keys to Soil Taxonomy (USDA/SCS, 1988), and Soil Survey Laboratory Methods and Pro- cedures for Collecting Soil Samples (USDA/ SCS, 1984). These original methodologies were modified to meet the particular needs of the DDRP. Modifications included speci- fications for sample sizes, quality assur- ance and quality control samples, soil-to- solution ratios, extraction times, extraction apparatus, holding times, standard internal quality control procedures, and standard or automated equipment. The handbook also delineates methods for making the following laboratory analyses: Rock fragment determination. Bulk density determination. Field moist pH determination. Organic matter determination. Air-dry moisture determination. Particle size analysis. pH determination. Cation exchange capacity. Exchangeable cations in ammonium ac- etate. Exchangeable cations in calcium chloride for lime and aluminum potential. Exchangeable acidity. Extractable iron, aluminum, and silicon. Extractable sulfate. Sulfate adsorption isotherms. Total carbon and nitrogen. Total sulfur. Methods Described in Handbook Sample Processing and Rock Fragment Determination The procedures presented here are spe- cific to bulk sample preparation methods employed in the DDRP. Alternatives tothese procedures are available in the published literature (e.g., USDA/SCS, 1972). Sample processing includes sample dry- ing, disaggregation, sieving, homogeniza- tion, and subsampling. Each of these is performed as sample processing steps in the preparation laboratory. Homogenization and subsampling are completed at the ana- lytical laboratory. The objective of these procedures is to produce homogeneous subsamples for subsequent analyses of physical and chemical parameter. Also in- cluded in this section is the procedure used for determination of percent rockfragments. Bulk Density Determination In the DDRP surveys, the clod method is the primary method for determining bulk density. Where possible, three replicate clod samples are extracted from each horizon. The average bulk density of the replicates is assumed to be the bulk density of that particular horizon. Analysis of the clods is based on the method described in the USDA/ SCS (11984), Kern and Lee (1989), and Kern et al. (in preparation). Two alternate methods are also presented for soil horizons that fail to yield satisfactory clods. One method is volume replacement (VR), a method similar to one described by Flint and Childs (1984), which utilizes a known volume of small foam beads packed into a cylinder to replace a selected volume of soil excavated from a given horizon. Subtracting the initial from the final volume yields the estimated volume of sample col- lected. The other method is a volume filling (VF) method that is used if the clod or VR methods do not produce representative samples. The volume of this type of sample is based on the absolute height of a 250-mL beaker, which is a constant 300 cm3. The known volume samples are processed in a manner similar to the method described in Blake (1965). Field-Moist pH Determination This method is applicable to the determi- nation of pH in soil samples. For the DDRP, field-moist pH is determined in the prepara- tion laboratory using an Orion Model 611 pH meter and an Orion Ross combination pH electrode. The method has been written assuming that the Orbn meter and elec- trode are used (Orion, 1983); however, it can be modified for use with other instru- mentation. Organic Matter Determination Loss-on-ignition (LOI) isthe method used to determine an approximation of percent organic matter of soil samples. Because organic samples are oxidized at high tem- peratures, percent organic matter can be calculated on a weight-loss basis. From the percent organic matter, the percent organic carbon can be estimated. In the DDRP, LOI was used to classify samples as mineral or organic for subsequent analysis purposes. Oven-dried soil samples are ashed in a muffle furnace to remove organic material. The difference in pre- and post-ashing weights is used to calculate percent organic content. A modified version of the method described in MacDonald (1977) is used. Air-Dry Moisture Content Air-dry moisture determination is done both at the preparation laboratory and at the analytical laboratory. In the preparation laboratory, the process is used to ensure that each sample is at an acceptable moisture level for further processing. In the analytical laboratory, the air-dry moisture is determined on all samples to convert all results to an oven-dry basis, and if specified in, a procedure, to calculate the weight of sample equivalent to agiven weight of oven- dry soil (Brady, 1974). A subsample of the air-dried bulk soi sample is weighed, oven-dried for approxi- mately 24 hours, and reweighed. The inrtia and final weights are used to calculate a percent weight loss. Particle Size Analysis Particle size analysis is determined on the less than 2-mm fraction from minera horizons only. The sieve/pipet/gravimetrk method described in (USDA/SCS 1984) is used. Organic matter is removed from the sample by digestion with hydrogen perox- ide. The sand fractions are separated from the silt and clay fractions by wet sieving The silt and clay fractions are suspended in water; aliquots taken from the suspension under specified conditions are dried anc then weighed. The sandf ractions are sieved and each fraction is weighed. The resulting gravimetric data allow calculation of the percentage of each particle size class. pH Determination The following procedure was developec to standardize the measurement of pH ir soils. The method has been written assum ing that the Orion Model 611 pH meter anc an Orion Ross combination pH electrode ------- are used (Orion, 1983); however, it can be modified for use with other instrumentation. The applicable pH range for soil solutions is 3.0 to 11.0. Two suspensions of each soil sample are prepared, one in deionized (Dl) water and one in 0.01 M calcium chloride (CaCI2) pH. The pH of each suspension is measured with a pH meter and a combination elec- trode. This method is modified from USDA/ 80S (1984). The Dl water pH is generally higher than the 0.01 M CaCI2 pH. Cation Exchange Capacity Two saturating solutions are used for cation exchange capacity (CEC) determi- nation. Ammonium acetate (1.0 N NH4OAc) buffered at pH 7.0 yields a CEC which is close to the total cation exchange capacity for a specific soil. This saturating solution is commonly used for soil comparisons. In acid soils, this estimate results in a high CEC value because of adsorption of NH4* ions to the pH-dependent exchange sites that exist above the soil's natural pH level. The overestimation will not occur when an unbuffered saturating solution of ammo- nium chloride (1.0 N NH4CI) is used. The NH Cl CEC has been termed "effective" CEC (i.e., that which occurs at field pH and is of greater importance because it is a more realistic estimate of CECthan the total CEC by NH4OAc). The two saturating solutions are retained for the exchangeable cation determinations. This method has been written assuming use of a mechanical ex- tractor. The soil sample is saturated with NH4* from a solution of NH OAc or NH4CI. Ex- cess NH4* is removed by ethanol rinses. The NH/ is displaced by Na* and is ana- lyzed by one of three methods: automated distillation-trtration, manual distillation-au- tomated titration, or ammonium displace- ment-flow injection analysis. The entire procedure is repeated with a fresh aliquot sample and a solution of NH4CI as the NH4* source. These methods are based on Doxsee (1985), Rhoades (1982), and USDA/ SCS(1984). Exchangeable Cations In Ammonium Acetate The exchangeable cations (Ca2*, Mg2*, K*, and Na*) in the soil can be used to estimate the ability of a soil to buffer acidic deposi- tion. Ammonium chloride and buffered am- monium acetate are used to extract ex- changeable base cations at pH values near the soil pH and at the buffered pH of 7.0, respectively. Base saturation is defined as the sum of exchangeable base cations di- vided by the cation exchange capacity (CEC) and is expressed as a percentage. Previously prepared extracts from the CEC procedure are analyzed for calcium, magnesium, potassium, and sodium. Once the concentration of each cation in the soil extract is determined, the cation concen- tration in the original soil sample may be calculated. Atomic absorption spectroscopy can be used to measure calcium, magne- sium, potassium, and sodium. Inductively coupled plasma spectroscopy can be used to measure cadmium, magnesium, and sodium. Emission spectroscopy can be used to measure potassium and sodium. Exchangeable Cations In Ammonium Chloride The exchangeable cations (Ca2*, Mg2*, K*, Na* and Al3*) obtained in unbuffered 1.0 N NH4CI representthe effective exchange that occurs at field pH. Values of the exchange- able cations determined by this procedure are theoretically equal to those determined by the buffered NH4OAc exchange. The concentrations (meq/100 g) of the ex- changeable cations plus acidity should ap- proximate the CEC. Base saturation is given as the total amount of exchangeable base cations di- vided by the CEC. Exchangeable acidity is a measure of the amount of exchangeable acidic cations on the soil cation exchange complex, Previously prepared extracts from the CEC procedure are analyzed for aluminum, calcium, magnesium, potassium, and so- dium. Once the concentration of each cat- ion in the soil extract is determined, the cation concentrations in the original soil sample can be measured by using atomic absorption spectroscopy, inductively coupled plasma spectroscopy, or emission spectroscopy. Exchangeable Cations In CaCI2 for Lime and Aluminum Potential Lime and aluminum potential are related to the concentrations of calcium (Ca2*) and aluminum (Al3*), respectively, that are ex- tracted from a soil sample by dilute calcium chloride (CaCL,) solution. Lime potential is defined as pH -1/2 pCa. The p-function is defined as the negative logarithm (base 10) of the molar concentration of that species, or: pX = -log [X]. The advantage of using the p-function is that concentration information is available in terms of small positive num- bers. Aluminum potential, K is defined as: KA = 3pH - pAL. The pH value determined in this method should be between the two pH values deter- mined for each soil sample. Extractable Mg2*, K*, and Na* are also determined for comparison to amounts determined in the CEC extracts. Fe3* and Al3* are determined for comparison to amounts obtained by the extractable iron and aluminum procedures. The procedure involves extraction of soil with 0.002 M CaCI2. The soil-to-solution ratio is1:2 for mineral soils and 1:10 for organic soils. The pH is determined using a pH meter and a combination electrode. Exchangeable Acidity The method most frequently used to de- termine exchangeable acidity involves treatment of the soil sample with a barium chloride triethanolamine (BaCL-TEA) solu- tion buffered to pH 8.2 followed by titration of the extracted solution. This method measures total potential acidity (Thomas, 1982). Exchangeable acidic ions are extracted from a soil sample using a mechanical ex- tractor with a BaCI2-TEA extracting solu- tion. The excess reagent in the extract is back-titrated with HCI. Results are ex- pressed as milliequivalents (meq) ex- changeable acidity per 100 g soil. Extractable Iron, Aluminum, and Silicon Iron and aluminum are extracted from soil by sodium pyrophosphate, citrate-dithionite, and acid-oxalate solutions. According to the Johnson and Todd (1983) iron and aluminum speciation scheme, the pyrophosphate ex- tract contains organically bound iron and aluminum; the citrate-dithionite extract contains non-silicate Fe3* and Al3*, and the acid-oxalate extract contains organic and amorphous oxides of Fe3* and Al3*. The exchangeable Al3* from the unbuffered NH^CI extract is more indicative of readily available Al3* under field conditions. The Fe3* and Al3* values from the pyrophos- phate, acid-oxalate, and citrate-dithionite extracts relate directly to the sulfate adsorp- tion capacity and have been used as an indication of this property (Fernandez, 1983). Silicon is extracted with the acid oxalate. Each of three portions of a soil sample is treated with a different solution to extract iron and aluminum. The three extracting solutions are 0.1 M sodium pyrophosphate, a sodium citrate-sodium dithionite solution, and an oxalic ammonium oxalate solution. After extraction, the three solutions are analyzed for iron, aluminum, and silicon by inductively coupled plasma spectroscopy. Extractable Sulfate The ability of soils to adsorb sulfate (SO42-) is one of the principal factors af- fecting the rate and extent of soil and watershed response to acidic deposition. Quantification of existing pools of adsorbed sulfate on a soil, concurrent with measure- ------- ments of sulfate adsorption capacity of that soil, provide useful information for under- standing the status and for predicting the future response of the soil to acidic deposi- tion. This method requires the extraction of two aliquots of a soil sample. Deionized water is the extracting matrix for readily available sulfate. The extracting matrix for sulfate that is more difficult to dislocate is 0.016 M sodium phosphate (containing 500 mg P/L). Afterthe extractions arecompleted, the analytes are determined by ion chro- matography. Sulfate Adsorption Isotherms The most direct and effective way to determine sulfate-adsorption capacity uti- lizes sulfate adsorption isotherms. In this method, sulfate adsorption isotherms are developed by measuring the amount of sulfate remaining in solution after contact with asoil sample. These sulfate adsorption isotherms allow comparisons to be made between horizons or between pedons. Six aliquots of the same soil sample are shaken with solution containing 0,2,4,8,16, and 32 mg sulfur per liter, respectively. The mixtures are centrifuged and filtered, and the resulting filtrate is analyzed for sulfate by ion chromatography. The difference be- tween the original concentrations of the sulfur solutions and the final concentrations after this procedure indicates the sulfur uptake or release by the soil. Total Carbon and Nitrogen Quantification of carbon and nitrogen pro- vides information about the amount and nature of organic material in the soil. Char- acterization of organic C and N also pro- vides insight about the potential for uptake or release of nitrogen and/or sulfur by the soil organic matter due to microbial activity. Analyses of total carbon and nitrogen were conducted using automated elemental analyzers. After sample processing and analysis for moisture content, a soil sample is oxidized at temperatures greater than 1,000°C with catalysts as specified by the instrument manufacturer. The evolved gases (CO2 and N2) are determined by thermal conductivity or infrared spectroscopy. Total Sulfur The determination of total sulfur is useful for characterizing relationships between inputs of sulfur from acidic deposition and soil sulfur pools. In this method, total sulfur in soil samples is determined by an auto- mated sulfur analyzer by combustion of the sample at approximately 1,370°C. This pro- cedure is based on the operating instruc- tions for a LEGO SC-132 sulfur analyzer (LEGO Corporation, 1983), adapted to per- mit analysis of very low levels of total S (as low as 10 mg/L) in soils. The sample is placed in a ceramic cru- cible with combustion accelerators and heated to a maximum of 1,370°C in a re- sistance furnace. The combustion of the sample liberates SO2 which is determined by an infrared detector. A microprocessor calculates results by combining the outputs of the infrared detector and system ambient sensors with preprogrammed calibration, linearization, and mass compensation fac- tors. This method is based on research by David etal. (1989). References Blake, G. R. 1965. In Black, C.A. (ed.). Methods of Soil Analysis, Part 1. American Society of Agronomy/Soil Science Society of America, Madison, Wisconsin. Brady, N. C. (ed.). 1947. The Nature and Property of Soils. Eighth Edition. MacMillan Publishing Co., Inc., New York, New York. Church, M. R., K. W. Thornton, P. W. Shaffer, D. L. Stevens, B. P. Rochelle, G. R. Holdren, M. G. Johnson, J. J. Lee, R. S. Turner, D. L. Cassell, D. A. Lammers, W. G. Campbell, C. I. Liff, C. C. Brandt. L. H. Liegel, G. D. Bishop, D. C. Mortenson, S. M. Pierson, and D. D. Schmoyer. 1989. Future Effects of Long Term Sulfur Depo- sition on Surface Water Chemistry in the Northeast and Southern Blue Ridge Prov- ince: Results of the Direct/Delayed Re- sponse Project. U. S. Environmental Pro- tection Agency, EPA/600/3-89/061, Washington, D. C. David, M. B., M. J. Mitchell, D. Aldcorn, and R.B. Harrison. 1989. Analysis of Sulfur in Soil, Plant, and Sediment Materials: Sample Handling and Use of an Auto- mated Analyzer. So/7 Biology and Bio- chemistry, 21:119-123. Doxsee, K. 1985. Cation Exchange Capac- ity in Nursery Soils Using FIA (Flow Injec- tion Analysis). Am. No. 1503-15. Weyerhaeuser Technology Center, Re- search Division, Tacoma, Washington. Fernandez, I. 1983. Field Study Program Elements to Assess the Sensitivity of Soils to Acidic Deposition Induced Alter- ations in Forest Productivity. Technical Bulletin No. 404. National Council of the Paper Industry for Air and Stream Im- provement, Inc., New York, New York. Flint, A. L. and S. Childs. 1984. Develop- ment and Calibration of an Irregular Hole Bulk Density Sampler. SoilSci. Soc. Am. J., 48(2) 374-378. Johnson, D. W. and D. E. Todd. 1983. Some Relationships among Fe, Al, C, and SO4 in a Variety of Forest Soils. Son Sci. Soc. Am. J.,47:702-800. Kern, J. S. and J. J. Lee. 1989. Evaluation of Two Alternative Bulk-Density Meth- ods. Agronomy Abstracts. American Society of Agronomy/Soil Science Soci- ety of America, Madison, Wisconsin. Kern, J. S., M. L. Papp, J. J. Lee, and L. J. Blume. In preparation. Appendix A In Kern, J. S. and J. J. Lee, Direct/Delayec Response Project. Field Operations anc the Mid-Appalachian Regions of the United States, U.S. Environmental Pro- tection Agency, Office of Research and Development, Washington, D.C. Klute, A. (ed.). 1986. Methods of So/, Analysis: Part 1. Physical and Mineral- ogical Methods. Agronomy Monograph No. 9, Second Edition. American Society of Agronomy/Soil Science Society of America, Madison, Wisconsin. LEGO Corporation. 1983. Instruction ManualSC-132. LEGO Corporation, 300 Lakeview Ave., St. Joseph, Ml 49085. MacDonald, C. C. 1977. Methods of So/i and Tissue Analysis in the Analytical Laboratory. Maritime Forest Research Canter Information Report, M-X-78. Fredericton, New Brunswick, Canada. Orion Research Incorporated. 1983. Instruc- tion Manual - Model 611 pH/millivol, meter. Orion, Cambridge, Massachu- setts. Page, A. L, R. H. Miller, and D. R. Keeney (eds.). 1982. Methods of Soil Analysis. Part 2, Chemical and Microbiologha Properties. Agronomy Monograph No. 9, Second Edition. American Society ol Agronomy/Soil Science Society ol America, Madison, Wisconsin. Rhoades, J. D. 1982. Cation Exchange Capacity, pp. 149-158. In: MethodsofSoi Analysis. Part 2, Chemical and Microbio logical Properties, Second Edition, A. L. Page, R. H. Miller, and D. R. Keeney (eds.). American Society of Agronomy; Soil Science Society of America, Madi- son, Wisconsin. Thomas, G. W. 1982. Exchangeable Cat- ions. In: Page, A. L., R. H. Miller, and D, R. Keeney (eds.). Methods of Soi ------- Analysis. Agronomy 9. American Soci- ety of Agronomy/Soil Science Society of America, Madison, Wisconsin. United States Department of Agriculture/ Soil Conservation Service. 1951. Supplement 1962. So/7 Survey Manual. Agriculture Handbook No. 18, USDA. U. S. Government Printing Office, Wash- ington, D. C. United States Department of Agriculture/ Soil Conservation Service. 1972. Pro- cedures for Collecting Soil Samples and Methods of Analysis for Soil Surveys. Soil Survey Investigations Report No. 1, USDA. U. S. Government Printing Office, Washington, D. C. United States Department of Agriculture/ Soil Conservation Service. 1975. Soil Taxonomy. Agriculture Handbook No. 436, USDA; U. S. Government Printing Office. Washington, D.C. United States Department of Agriculture/ Soil Conservation Service. 1983. National Soils Handbook. Title 430, USDA. U. S. Government Printing Office, Washing- ton, D. C. United States Department of Agriculture/ Soil Conservation Service. 1984. Soil Survey Laboratory Methods and Proce- dures for Collecting Soil Samples. Soil Survey Investigations Report No. 1, USDA. U. S. Government Printing Office, Washington, D. C. United States Department of Agriculture/ Soil Conservation Service. 1988. Key to Soil Taxonomy. Technical Monograph No. 6, USDA/Agronomy Department, Cornell University, Ithaca, New York. l.S. GOVERNMENT PRINTING OFFICE: 19ğl - 548-0 28/400*5 ------- L J. Blume, B. A. Schumacher, P. W. Shaffer, L A. Cappo, M. L Papp, R. D. Van Remortel, D. S. Coffey, M. G. Johnson, and D. J. Chalaud are with Lockheed Engineering & Sciences Company, Las Vegas, NV 89119. D. T. Heggem is the EPA Project Office (see below). The complete report, entitled "Handbook of Methods for Acid Deposition Studies, Laboratory Analyses for Soil Chemistry," (Order No. PB91-218 016/AS; Cost: $39.00, subject to change) will be available only from: National Technical Information Service 5285 Port Royal Road Springfield, VA 22161 Telephone: 703-487-4650 The EPA Project Officer can be contacted at: Environmental Monitoring Systems Laboratory U.S. Environmental Protection Agency Las Vegas, NV 89193-3478 United States Environmental Protection Agency Center for Environmental Research Information Cincinnati, OH 45268 BULK RATE POSTAGE & FEES PAID EPA PERMIT NO. G-35 Official Business Penalty for Private Use $300 EPA/600/S4-90/023 ------- |