I want to know the precise range of particle sizes that are considered appropriate when determining total and bio-available metal concentrations in agricultural soils. I understand most scholarly studies based determination on soil samples that have been sieved through a 2-mm mesh or possibly less. Can one consider metal concentrations that were determined in soil samples sieved through a 0.5-mm sieve as also valid?
We normally recommend samples passed through 2 mm sieve for plant -available soil nutrient elements.For total nutrient analysis and for organic carbon estimation 0.5 mm sieved soil is preferred.When we take small amount of sample for analysis homogeneity of sample is important.
For a given mass of soil analysed, the bigger the particle size the greater the variation between replicates. In addition, to the extent that the particles remain intact and the rate of reaction is diffusion controlled, extraction times appropriate to 2 mm particles would need to be extended for the larger particles.
In addition to the latter comment about particle size and extraction time, fine grinding affects the behaviour of some species in some soils due to the exposure of 'new' surfaces. That is, you need to ask a more specific question to get a more specific response.
The sampled soil should be air -dried, homogenized,, and passes through a 2mm sieve.
Ghrair, A.M., Ingwersen, J., Streck, T. (2013). The effect of zeolitic tuff nanoparticles on Cd, Pb and Zn fractionation and uptake by barley from a sewage sludge treated soil. In Cadmium: Characteristics, Sources of Exposure, Health and Environmental Effects.1st ed. Nova Science Publishers, Inc. Hauppauge, USA.
Ghrair, A.M., Ingwersen, J., Streck, T. (2010): Immobilization of Heavy Metals in Soils Amended by Nanoparticulate Zeolitic Tuff: Sorption-Desorption of Cadmium. Journal of Plant Nutrition and Soil Science, DOI: 10.1002/jpln.200900053.
Best regards and wishes,
Dr. Ayoup Ghrair
Royal Scientific Society
Amman-Jordan
normally 2 mm is the required size especially when working with total elements
Hi Clement, the suggestions above are very useful. Can I ask to share the standard method on analysis of bio availability of heavy metal？ I am quite interested in that, as there are many methods, a little confused with if there is a standard method. Much appreciated.
Best of luck,
Xin
As I understand you can use the same soil test methods which can be used for plant-available soil micronutrients .Mehlich 3 method for As and DTPA method for Cd,Cr,Ni,Pb,Zn,Cu.You may consult the following publication for more details of the methods.Reference Soil and Media Diagnostic Procedure for the Southern Region of the United States by S.J.Donohue,editor.Virginia Agricultural Experimental Station,Virginia Polytechnic Institute and State University,Blacksburg,VA 24061-0402 Southern Cooperative Series Bulletin No.374( August,1992) Available online.
As I understand you can use the same soil test methods which can be used for plant-available soil micronutrients .Mehlich 3 method for As and DTPA method for Cd,Cr,Ni,Pb,Zn,Cu.You may consult the following publication for more details of the methods.Reference Soil and Media Diagnostic Procedure for the Southern Region of the United States by S.J.Donohue,editor.Virginia Agricultural Experimental Station,Virginia Polytechnic Institute and State University,Blacksburg,VA 24061-0402 Southern Cooperative Series Bulletin No.374( August,1992) Available online.
Composite soil sample air dried, mixed, homogenized and passed through 2 mm sieve is suitable for determining bio-available nutrients unless there is some specific objective of soil analysis.
Ms.Xin Shu,you may consult the following publication for estimation of bio-available heavy metals in soils
Evaluation of extractants for estimation of phyto-available trace metals in soils.Menzies,N.W and others .Environmental pollution 145(2007)121-130 Available online at www.scienceditect.com
The extraction method you use and its calibration determine which particle size maximum your sample should have. Its usually 2mm for available metals, but from my long term experience I would guess that you are also ok with 0,5 mm sieving. If you are after total metal content by any digestion method, I recommend ball or disk milling in an agate tool until powdered!
Viewers and followers of the question may also see the following paper available on researchgate which recommends 0.15mm sieving for total carbon analysis in diverse soils by high-temperature combustion.
http://www.researchgate.net/publication/233181810_Effects_of_Soil_sample_Grinding_Intensity_on_Carbon_Dererminatio_by_High_Temperature_Combustion
Article Effects of Soil Sample Grinding Intensity on Carbon Determin...
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