Methodological aspects of determining soil particle-size distribution using the laser diffraction method

624 DOI: 10.1002/jpln.201000255 J. Plant Nutr. Soil Sci. 2011, 174, 624–633 Methodological aspects of determining soil particle-size distribution u...
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DOI: 10.1002/jpln.201000255

J. Plant Nutr. Soil Sci. 2011, 174, 624–633

Methodological aspects of determining soil particle-size distribution using the laser diffraction method Magdalena Ryz˙ak1* and Andrzej Bieganowski1 1

Institute of Agrophysics, Polish Academy of Sciences, Dos´wiadczalna 4, 20–290 Lublin 27, Poland

Abstract This paper presents the influence of selected methodological aspects on the results of particlesize distribution (PSD) as measured by the laser diffraction method (LDM). The investigations were carried out using the Mastersizer 2000 with Hydro MU attachment (Malvern Ltd., UK). It was found that for the investigated soils: (1) optimal speed of pump and stirrer was 2500 rpm, (2) optimal measurement time was ≈ 1 min, (3) there are two, practically equivalent methods for soil-sample dispersion: chemical (with the use of a solution of sodium hexametaphosphate) or physical (by means of ultrasound application for 4 min at a maximum power of 35W), (4) one must not use the chemical and physical dispersing methods simultaneously, because this can lead to aggregation (not dispersion) of soil particles, (5) the Fraunhofer theory (physical models) can be used to convert scattered-light data to PSD. In the case of the Mie theory, the best results were obtained for a refractive index (RI) in the range of 1.5–1.6 and an absorption index (AI) of 1.0. It was also found that most of the discussed parameters depend on design of the measuring device and on the type and volume of the investigated suspensions. It is necessary, therefore, to explain how the data was obtained every time and to specify the details in the methodological part of the paper. Key words: particle-size distribution (PSD) / laser diffraction method (LDM) / soil / dispersion of soil

Accepted November 28, 2010

1 Introduction Particle-size distribution (PSD) is one of the most important soil characteristics. PSD influences soil properties such as pore distribution, water retention, water conductivity (Hajnos et al., 2006; Sławin´ski et al., 2006), and thermal and sorption properties. It also indirectly influences soil nitrification (Włodarczyk et al., 2008) and many other soil properties (Czyz˙ and Dexter, 2009; Balashov et al., 2010; Ke˛sik et al., 2010). Sedimentation methods are currently used to measure PSD. There is an international standard describing the pipette method, which is one of the sedimentation methods (ISO 11277, 1998). A new method called the laser diffraction method (LDM) for measuring PSD, however, is becoming more and more popular. Whenever a new method appears, research is conducted to determine the applicability of the method by comparing the new method with other methods used so far. Comparisons of the LDM with sedimentation methods have been carried out (Arriaga et al., 2006; Goossens, 2008; Taubner et al., 2009; Ryz˙ak and Bieganowski, 2010) but so have investigations simply using the new laser diffraction method (Hayton et al., 2001; Murray, 2002; Campbell, 2003; Sperazza et al., 2004; Blott and Pye, 2006; McCave et al., 2006). As with every new method, the laser diffraction method has many proponents and opponents.

Literature review has led to the conclusion that the comparison of published results needs to be treated qualitatively rather than quantitatively. There are two main types of causes of uncertainty associated with quantitative comparison of published results. The first is objective causes. There are many different types of laser diffraction devices, from different generations and from various manufacturers. The development of these devices and the hardware and software innovations applied to them introduces a serious source of uncertainty in such comparisons. The second type of causes making comparison of result difficult is subjective causes— resulting from human error (error caused by researcher). The various measuring procedures (at different stages of measurement) are the main reason. Study of available papers shows that not only is there a lack of a standard method of measurement, but also a lack of information about measurement details in the methodological part of the paper. For instance, there was no information about which mathematical model (Fraunhofer or Mie theory) was used in the calculations in some of the papers published after the year 2000. When the Mie theory was used, there was often no information about the optical parameters of the continuous and dispersion phases (absorption and refractive indexes).

The laser diffraction method is based on measuring the scattered laser beam on measured soil particles. The scattered laser light is registered on detectors. The angle at which the beam is scattered is inversely proportional to the soil particle size. The software provided by the manufacturer recalculates the information from the detectors into volumetric PSD.

The aim of this paper was to perform an analysis of the influence of different methodological aspects of LDM on the PSD results. All aspects discussed in the paper are universal for all apparatus using LDM, although some of the parameters (for instance the speed of the particles moving through the laser beam) can be controlled in different ways.

* Correspondence: Dr. M. Ryz˙ak; e-mail: [email protected]

 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

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J. Plant Nutr. Soil Sci. 2011, 174, 624–633

2 Materials and methods

Methodological aspects of laser PSD 625 meters), 23 soil samples were measured and analyzed. Twenty-two samples were collected from the arable layer and one sample (Tab. 1, profile 10) was collected from the parent rock.

2.1 Materials The soil samples chosen for the measurements were derived from 23 soil profiles which are quantitatively and qualitatively representative for SE Poland. The samples were dried at 105°C, gently crushed, and dry-sieved at 2 mm mesh size. Descriptions of selected properties of the investigated mineral soil samples are given in Tab. 1. PSD obtained from the sedimentation method according to ISO 11277 (1998) is presented in Tab. 1. The first stage of investigation consisted in selection of the pump and stirrer speed and of the measuring time. The problem of rapid sedimentation of large particles under the influence of the force of gravity during mixing is especially evident in soils in which the biggest fraction (sand fraction) is found. Taking this into consideration, the sample which has one of the biggest content of sand fraction from all of the samples— the Eutric Cambisols (Tab. 1, sample from profile 6)—was selected for measuring the influence of pump and stirrer speed on sedimentation and selection of measuring time. For the realization of the second stage of the measurements (procedure of soil-sample preparation), the representatives of different types of mineral soils were selected: Haplic Phaeozem, Mollic Gleysol, Calcaric Cambisol, and Orthic Luvisol (Tab. 1, samples profiles: 10, 11, 18, and 23). For the realization of the third stage of the measurements (selection of theory and in the case of Mie theory, selection of optical para-

2.2 Apparatus Laser analyzer Mastersizer 2000 (Malvern Instruments) with Hydro MU adapter was used to determine the PSD of soil samples. The measurement range of the apparatus is 0.02–2000 lm. The Hydro MU adapter is equipped with: – a stirrer; to prevent sedimentation of particles in the beaker, by circulating the sample in the measuring system and facilitating flow through the measuring cell. The speed of rotation of the stirrer ranges from 0 to 4000 rpm and can be regulated in increments of 50 rpm. – an ultrasonic probe; with a maximum power of 35 W and a frequency of 40 kHz. The amplitude ranges from 2 to 20 lm and can be regulated in increments of 0.5 lm (defined by the manufacturer as 2–20 units in increments of 0.5 units). For the determination of PSD, the Mastersizer apparatus uses two sources of light: red (wavelength 633 nm) and blue (wavelength 466 nm).

Table 1: Selected properties of soils. Soil profile Soil number

Corg /%

Particle-size distribution / % (∅ / mm) sand 2–0.05

silt 0.05–0.002

clay < 0.002

Eutric Cambisols

50 58 71 62 70 95 96 94

40 31 25 27 27 4 3 5

10 11 4 11 3 1 1 1

0.82 0.94 0.65 0.73 0.79 2.28 0.99 0.77

9 10

Orthic Luvisols

88 84

11 6

1 10

1.01 0.15

11 12 13 14 15 16

Haplic Phaeozems

59 60 86 63 60 60

30 34 13 32 34 29

11 6 1 5 6 11

1.24 1.48 2.10 2.07 1.11 1.62

17

Eutric Fluvisol

86

12

2

1.14

18 19 20 21 22

Calcaric Cambisol

61 85 49 78 91

21 13 35 17 8

18 2 16 5 1

0.61 1.62 0.77 1.21 0.98

23

Mollic Gleysol

53

34

13

3.08

1 2 3 4 5 6 7 8

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The quantity of soil sample that is added into the measuring system is determined by a parameter called “obscuration”, which is measured by the apparatus every time a sample is added, as it is being added. Obscuration is the degree to which the light from the laser beam is obscured by the particles being measured. The manufacturer recommends that the value of obscuration should be between 10% and 20%. Below 10%, the number of particles is too small to obtain reliable results. Above 20%, the laser beam can be subject to secondary refraction because the number of particles is too large, and this may falsify the resultant PSD (Malvern Worcs, 1999). The volume of distilled water to which the soil samples were added at the dispersion phase was ≈ 800 mL (in a 1000 mL beaker). This volume was experimentally selected and allowed for good mixing of the suspension without simultaneously sucking air bubbles into the measuring system and without splashing any of the suspension out of the beaker. The measurement of PSD using the LDM consists of recording the beam which is diffracted off of the particles in suspension and returned to the detectors. Because the Mastersizer 2000 apparatus records the source signal from the detectors, it is possible to calculate the results by selecting one of the algorithms which are supplied by the manufacturer. It is necessary to select an appropriate theory (Mie or Fraunhofer) as well as an appropriate algorithm to use in the calculations. These selections depend on the properties of the particles being measured. The manufacturer provides three groups of algorithms: general purpose analysis (GPA), multiple narrow modes (MNP), and single mode (SM). Within each algorithm group, there are two more algorithms: irregular-shape ratio (ISR) and spherical-shape ratio (SSR). The GPA algorithm is a calculation procedure recommended by the manufacturer for particles with unknown properties or for samples containing a large number of various fractions. The MNP algorithm is a calculation procedure for mixtures that are known to contain particles of two (or more) monodispersive fractions, i.e., distributions of the individual fractions are narrow and best when they are also discrete. The SM algorithm is a calculation procedure used for estimating the grain-size distribution of monodispersive individual fractions with narrow grain-size distribution. The ISR algorithm is related to the shape of the measured particles. Although one of the assumptions of this method is that the particles are perfect spheres, the manufacturer has provided a module permitting greater accuracy of results when the particles under study are not perfect spheres. The SSR algorithm is a calculation procedure for spherical particles. Based on the specific properties of the soil samples, the following algorithms were chosen GPA and ISR.

2.3 Selection of pump and stirrer speed Proper selection of pump and stirrer speed should guarantee consistency of measurements throughout the measuring time and also eliminate the difficulties associated with too much intensive stirring and, thus, either sucking air bubbles in (which can be treated as soil particles by the measuring system) or splashing of the suspension out of the beaker. The apparatus Mastersizer 2000 with Hydro MU attachment is equipped with a pump which is integrated with the stirrer. Taking into account previous experience, for this investigation  2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

J. Plant Nutr. Soil Sci. 2011, 174, 624–633 this parameter was modified to cover a pump speed range from 1200 to 3000 rpm, regulated in increments of 200 rpm.

2.4 Selection of measuring time The measurements consist of a number of “snap shots” (i.e., a number of records of the intensity of the detectors) during the measuring time. The greater the number of shots, the lower the uncertainty of the measurement, because statistically the representation of the sample being measured in the measuring cell is increased. For a better explanation of the above statement, one can consider a situation where there are a very large number of identical particles of a definite size and one much larger particle suspended in the suspension. The probability that the large particle will be found in the measuring cell (and in effect be taken into account in the averaged final result) will increase as the number of individual measurements increases. From the point of view of representative results, extending the measuring time reduces the uncertainty. On the other hand, any laboratory which carries out thousands of analyses per month tends to cut down on the measuring time. It is therefore necessary to determine the minimum measuring time which will guarantee satisfactory reproducibility of results. In the Mastersizer 2000, the measuring time can be regulated from 1 to 131 s (half of the time is designed for red light and the other half for blue light). A previously prepared sample was placed in the measuring system, and 10 measurements of PSD were conducted. The measuring time for each measurement was 5 s. Next, without removing the sample from the measuring system, another 10 measurements were conducted for a measuring time extended by 5 s. PSD measurements of 10 were conducted, each time extending the measuring time by 5 s, up to a measurement time of 40 s. For each measuring time, the changes of diameter d(0.9) (decile 0.9, i.e., particle size below which 90% of all particles are contained) were monitored, to check whether all of the large particles get to the measuring cell during the measurement.

2.5 Procedure of soil-sample preparation— selection of soil-sample dispersion Natural aggregations of soil particles require breaking down before PSD can be determined; otherwise the aggregates will break down during the measurement and cause instability and a lack of result reproducibility (Pini and Guidi, 1989). The efficiency of the soil-sample-preparation method (dispersing soil aggregates) can be determined by analyzing change (or lack of change) in the value of diameter d(0.5) (also known as the median) during consecutive measurements. Measurements concerned with the methodology of soil-sample preparation were conducted for the following methods of dispersion: – application of ultrasound (by ultrasonic probe built-in to the Hydro MU adapter with minimum and maximum power) to the soil samples placed in the measuring system in dry form; www.plant-soil.com

J. Plant Nutr. Soil Sci. 2011, 174, 624–633 – application of ultrasound with tip displacement of 20 lm (maximum power) to soil samples which were soaked in water for 6 and 24 h; – application of a solution of Na-hexametaphosphate and anhydrous CaCO3 (35.7 g Na-hexametaphosphate and 7.94g anhydrous CaCO3 topped up with distilled water to 1000 mL [Polish Standard PN-R-04032, 1998]), sometimes known as calgon; – application of ultrasound with a tip displacement of 20 lm (maximum power) to soil samples which were prepared with calgon (for 40 g of soil sample: 50 mL of calgon was added to samples containing carbonate—samples from Calcaric Cambisols, profiles 18–22; and 25 mL of calgon was added to soil samples not containing carbonate). At this stage of the experiment, all measurements were conducted within 1 h from the moment the sample was placed in the measuring system. In the case of ultrasound application, the ultrasonic probe operated during the measurement. The results were registered at 60 s intervals.

2.6 Procedure of soil-sample preparation—other stages of this work Regardless the results of the selection of the sample dispersion for all other stages of this work the chemical procedure of soil dispersion was chosen. The argument was to be compatible with ISO 11277 (1998) standard. It was experimentally verified that the median of dispersed soil did not change during the measurement—verifying that all aggregates were broken up and that the sample remained stable throughout the measurement.

2.7 Selection of theory and—in the case of the Mie theory—selection of optical parameters The next stage of the research consisted of evaluating the impact of the selection of a theory (Mie or Fraunhofer) applied

Methodological aspects of laser PSD 627 to convert the diffraction data to PSD. In the case of the Mie theory being chosen, the impact of selection of optical properties was also determined. Selection of the Mie theory entails the necessity of defining the optical parameters: the refractive index for the dispersing medium, and the refractive and absorption indexes for the medium being dispersed. The refractive indexes for the two mediums should differ considerably from each other. Since soil is a heterogeneous mixture containing different minerals (with different optical properties), it is necessary to assume approximate values for the optical properties of the investigated suspensions. On the basis of literature, in this work it was assumed that the smallest value of refractive index was 1.43 (for opal) and the biggest was 3.22 (for hematite) (Sperazza et al., 2004). The parameters defined by the manufacturer for materials similar to soil were taken into account (the set of parameters called China Clay (lo), China Clay (av), China Clay (hi) and default parameters for samples with unknown properties) (Malvern Worcs, 1999). Because there is a broad gap between the value of refractive index which is recommended by the manufacturer and the maximum value for hematite, a value for refractive index equal to 2.00 was taken as an intermediate value. The absorption indexes were selected so as to take into account materials which were completely transparent (absorption index equal to 0) and completely absorbing (absorption index equal to 1) (Sperazza et al., 2004). Intermediate values of 0.01 and 0.1 were also chosen. Table 2 presents a compilation of investigated theories and values of optical parameters. As a measure of selection of the theory, and in the case of the Mie theory—the selection of optical parameters, a parameter called “residual weighted” was used. Residual weighted returns a number that is the % residual in the comparison of the fitted and corrected data when the weighting of the detector set is factored into the calculation (Malvern Worcs, 1999). According to the recommendation of the manufacturer, the result is correct if the residual weighted is
50 lm and the Mie theory when measuring particles that are < 50 lm (ISO 13320, 1999). In the case of soil it is difficult, because in soil samples particles of various sizes occur. The reason for which the Fraunhofer theory gives better results for soil samples might be heterogeneity of samples, especially optical heterogeneity. There are different mineral and organic particles in soil. Only among mineral particles there might be such as posses small and big values of the refractive index (see Tab. 2 where refractive index varies from 1.43 for opal to 3.22 for hematite). That is why arbitrary assumption of one set of optical parameters might be the source of uncertainty of final results. Using the Fraunhofer theory eliminates the necessity of defining the optical properties and, consequently, reduces the uncertainty. However, if it was necessary to choose the Mie theory then comparably small values of the sum of the residual parameter were obtained for sets of optical parameters number 5 (RI = 1.43; AI = 1), 9 (RI = 1.533; AI = 1), 14 (RI = 1.555; AI = 1), and 18 (RI = 1.577; AI = 1). It is worth to notice that for all these sets of parameters the value of absorption index was equal 1. On the base of this, one can conclude that from those two optical parameters, in the case of determining PSD, the absorption index is the most important. The value determined in our experiments is different from that proposed by the producer.

As far as the value of the refractive index is concerned, one of the three values given by the producer in the software might be assumed. Relating to data from literature, it is necessary to quote repeatedly the mentioned work by Sperazza et al. (2004) who obtained a final conclusion similar with presented in this work. The authors evaluated fitting of the distribution obtained with the LDM to the distribution obtained for properly prepared samples by mixing known proportions of given fractions. They concluded that as absorption reached a value of 1, the values for sediment concentration calculated by the software were the closest to our measured sediment concentration. At absorption settings ≥ 0.9 for mixed mineral compositions the difference from varying RI values was negligible. Estimated grain-size distributions were highly dependent on values of absorption setting for analyses of natural sediments.

4 Conclusions (1) The pump and stirrer speed selected for specific analysis will be dependent on the design of the apparatus and on the extent of heterogeneity of measured samples (with respect to PSD). For homogeneous samples, this speed may be lower.

Figure 5: Sum of the values of the residual parameter for investigated soil samples. Numbers determine the assumed parameters corresponding to the numbers of sets determined in Tab. 2.

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Thus it is indispensable to evaluate this parameter every time before measurements are conducted on a new material. The assumed parameters must be presented in the methodological part of the work. In this work the optimal speed of pump and stirrer was determined to be 2500 rpm. (2) The selection of the measuring time depends on the heterogeneity of the measured sample (with respect to PSD). Thus it is also important to present the choice of this parameter in the experiment in the methodological part of the work. In this work the measuring time was assumed as equal to 1 min (30 s for red light and 30 s for blue light). (3) The dispersion of soil samples for PSD measurement may be carried out in two practically equivalent methods: chemically (using hexametaphosphate solution) or physically (by ultrasound). In the case of using ultrasound, the power and the duration of ultrasound operation should be experimentally chosen because these are dependent on the design of the ultrasound probe and on the type and volume of substance measured. The analysis of variation (or lack of variation) and the value of the distribution median is a good parameter which permits evaluation of the efficiency of dispersion. The value adopted should be described in the methodological part of the work. For the soil samples measured in this work, the power of ultrasound probe was 35 W and the duration was equal to 4 min—this dispersion was practically equivalent to the chemical dispersion. (4) One must not simultaneously use the chemical dispersion (using hexametaphosphate solution) and the physical dispersion (using ultrasound) because this may cause an opposite effect, i.e., secondary aggregation instead of dispersion. (5) Since the soil is a mixture of small particles (∅ < 50 lm) and big particles (∅ > 50 lm) with different optical properties (refractive index and absorption index), the Fraunhofer theory should be used for the conversion of the intensity of scattered light into PSD. In the case of using the Mie theory, the best results were obtained for a refractive index between 1.5 and 1.6 and for absorption index equal to 1.0.

References Arriaga, F. J., Lowery, B., Mays, M. D. (2006): A fast method for determining soil particle size distribution using a laser instrument. Soil Sci. 171, 663–674. Balashov, E., Kren, J., Prochazkova, B. (2010): Influence of plant residue management on microbial properties and water-stable aggregates of two agricultural soils. Int. Agrophys. 24, 9–14. Beuselinck, L., Govers, G., Poesen, J., Degraer, G., Froyen, L. (1998): Grain-size analysis by laser diffractometry: comparison with sieve-pipette method. Catena 32, 193–208.

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J. Plant Nutr. Soil Sci. 2011, 174, 624–633 Bieganowski, A., Ryz˙ak, M., Witkowska-Walczak, B. (2010): Determination of soil aggregate disintegration dynamics using laser diffraction. Clay Miner. 45, 23–34. Blott, S. J., Pye, K. (2006): Particle size distribution analysis of sandsized particles by laser diffraction: an experimental investigation of instrument sensitivity and the effect of particle shape. Sedimentology 53, 671–685. Buurman, P., Pape, Th., Muggler, C. C. (1997): Laser grain-size determination in soil genetic studies. 1. Practical problems. Soil Sci. 162, 211–218. Buurman, P., Pape, Th., Reijneveld, J. A., de Jong, F., van Gelder, E. (2001): Laser-diffraction and pipette-method grain sizing of Dutch sediments: correlations for fine fractions of marine, fluvial, and loess samples. Neth. J. Geosci. 80, 49–57. Campbell, J. R. (2003): Limitations in the laser particle sizing of soils, in Roach, I. C. (ed.). Advances in Regolith. CRC LEME, Canberra, Australia, pp. 38–42. Chappell, A. (1998): Dispersing sandy soil for the measurement of particle size distribution using optical laser diffraction. Catena 31, 271–281. Czyz˙, E. A., Dexter, A. R. (2009): Soil physical properties as affected by traditional, reduced and no-tillage for winter wheat. Int. Agrophys. 23, 319–326. Eshel, G., Levy, G. J., Mingelgrin, U., Singer, J. M. (2004): Critical evaluation of the use of laser diffraction for particle-size distribution analysis. Soil Sci. Soc. Am. J. 68, 736–743. Gee, G. W., Bauder, J. W. (1987): Particle-size analysis, in Klute A. (ed.): Methods of Soil Analysis, Part 1, Physical and Mineralogical Methods. Agronomy Monograph No. 9, 2nd edn., American Society of Agronomy and Soil Science Society of America, Madison, WI, USA, pp. 383–411. Goossens, D. (2008): Techniques to measure grain-size distributions of loamy sediments: a comparative study of ten instruments for wet analysis. Sedimentology 55, 65–96. ´ wieboda, R., Sokołowska, Z., WitkowskaHajnos, M., Lipiec, J., S Walczak, B. (2006): Complete characterization of pore size distribution of tilled and orchard soil using water retention curve, mercury porosimetry, nitrogen adsorption, and water desorption methods. Geoderma 135, 307–314. Hayton, S., Campbell, S. N., Ricketts, B. D., Cooke, S., Wedd, M. W. (2001): Effect of mica on particle-size analyses using the laser diffraction technique. J. Sediment. Res. 71, 507–509. ISO 11277 (1998): Soil quality – Determination of particle size distribution in mineral soil material – Method by sieving and sedimentation. International Organization for Standarization, Geneva, Switzerland. ISO 13320 (1999): Particle size analysis – laser diffraction methods – part 1. International Organization for Standarization, Geneva, Switzerland. Ke˛sik, T., Błaz˙ewicz-Woz´niak, M., Wach, D. (2010): Influence of conservation tillage for onion production on the soil organic matter content and soil aggregate formation. Int. Agrophys. 24, 267–274. Konert, M., Vandenberghe, J. (1997): Comparison of laser grain size analysis with pipette and sieve analysis: a solution for the underestimation of the clay fraction. Sedimentology 44, 523–535. Loizeau, J. L., Arbouille, D., Santiago, S., Vernet, J.-P. (1994): Evaluation of wide range laser diffraction grain size analyser for use with sediments. Sedimentology 41, 353–361. Malvern Worcs (1999): Malvern Operators Guide. Malvern Worcs. U.K.

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J. Plant Nutr. Soil Sci. 2011, 174, 624–633 McCave, I. N., Bryant, R. J., Cook, H. F., Coughanowr, C. A. (1986): Evaluation of a laser-diffraction-size analyzer for use with natural sediments. J. Sediment. Res. 56, 561–564. McCave, I. N., Hall, I. R., Bianchi, G. G. (2006): Laser versus settling velocity differences in silt grainsize measurements: estimation of palaeocurrent vigour. Sedimentology 53, 919–928. Murray, M. R. (2002): Is laser particle size determination possible for carbonate-rich lake sediments? J. Paleolimnol. 27, 173–183. Pini, R., Guidi, G. (1989): Determination of soil microaggregates with laser light scattering. Commun. Soil Sci. Plant Anal. 20, 47–59. Polish Standard PN-R-04032 (1998): Soils and mineral formations – Sampling and determination of grain size distribution (in Polish). Polish Committee for Standarization. Pye, K., Blott, S. J. (2004): Particle size analysis of sediments, soils and related particulate materials for forensic purposes using laser granulometry. Forensic Sci. Int. 144, 19–27. Ryz˙ak, M., Bieganowski, A. (2010): Determination of particle size distributionof soil using laser diffraction – comparison with areometric method. Int. Agrophys. 24, 177–181.

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Methodological aspects of laser PSD 633 Singer, J. K., Anderson, J. B., Ledbetter, M. T., McCave, I. N., Jones, K. P. N., Wright, R. (1988): An assessement of analytical techniques for the size analysis of fine-grained sediments. J. Sediment. Res. 58, 534–543. Sławin´ski, C., Walczak, R. T., Skierucha, W. (2006): Error analysis of water conductivity coefficient measurement by instantaneous profiles method. Int. Agrophys. 20, 55–61. Sperazza, M., Moore, J. N., Hendrix, M. S. (2004): High-resolution particle size analysis of naturally occurring very fine-grained sediment through laser diffractometry. J. Sediment. Res. 74, 736–743. Taubner, H., Roth, B., Tippkötter, R. (2009): Determination of soil texture: Comparison of the sedimentation method and the laserdiffraction analysis. J. Plant Nutr. Soil. Sci. 172, 161–171. Włodarczyk, T., Ste˛pniewski, W., Brzezin´ska, M., Przywara, G. (2008): Impact of different aeration conditions on the content of extractable nutrients in soil. Int. Agrophys. 22, 371–375. Zobeck, T. M. (2004): Rapid soil particle size analyses using laser diffraction. Appl. Eng. Agric. 20, 633–639.

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