I think your goal of determining sand, silt and clay is best done by meausing bulk densities rather than on particle size distribution.  A good reference is

http://www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/nrcs142p2_053256.pdf

if there is a considerable content of organics I would first determine light fraction by density separation after prescreening of oversized material (> 2 or 5 mm). To this end you may use ZnBr2 or polytungstate to adjust the continuous phase density. After or omitting this step you may use directly wet sieving to get fractions. To get the clay fraction you will have to do particle sizing of the < 20 µm fraction obtained.

Hi Gilan,

I confirm what has been written by Dr. Klicpera; in addition, I can suggest, first, a wet separation between sand (including gravel, if present) and mud (preceded by stirring, after the addition of a dispersant substance such as SHMP), followed both by a less laborious dry sieving of sand (in order of processing times) and by wet laser particle sizing for the remaining muddy fraction.

The hydrometer method (ASTM Spec. Pub. 234, 1959) has a low resolution but is certainly less expensive and also quick to be made in battery than the other two methods.

totally agree on laser particle sizing, buy this might be quite expensive and I expect your looking for a low cost way of doing this analysis

I don't know the specific method you are asking about, but we have a particle size instrument in the lab where I work, a Sedigraph, I believe, that uses settling velocity and lasers to determine particle size distribution of the silt fraction (using Stoke's Law). I agree with the previous comments above, that you will likely need to physically separate the sand/gravel fraction with wet sieving, then go from there. perhaps freeze dry the different splits, then mass them? An instrument will give high quality particle size distribution data, but the coarser fraction may require a bit more interpretation (?).

Here is a link from the people who make the sedigraph:

http://www.micromeritics.com/Product-Showcase/SediGraph-III-Plus/SediGraph-Method-Overview.aspx

Thank you all for your answers, as I understand most agree that the best method for the percentage of silt and clay,  is  the usage of lasers diffraction instrument.  for sand content we can use sieving wet/dry sediments. As Bothun said laser particle sizing is an expensive method and we don't have this in our Lab. I have 70 sediment samples in each season, so we have to use another methods. what a bout attached protocol? is a proper protocol? or we use sieving for sand and then use hydrometery for silt and clay? if anyone have a good protocol could you please send me

I used hydrometer method according to the attached protocol, but my problem is that the most  percentage of the sediment was sand by this method, while sediment texture seems more silt/clay when its touched by finger

Thanks All

If you use volume weighted or mass fraction the larger ones, i.e. sand contributes much more to the distribution, even a mass fraction of a few % clay will have a large impact on texture.

After sieving the sediment , you can use the GRADISTAT (Blott and Pye, 2001). If you want I can send you.

Blott, S. J., & Pye, K. (2001). GRADISTAT: a grain size distribution and statistics package for the analysis of unconsolidated sediments. Earth surface processes and Landforms, 26(11), 1237-1248.

Another method is specific excell modifications with Folk and Ward (1957) criteria.

Regards.

Greetings,

Have you tried to do thin section analysis of sediments? I mean if you are extracting sediments on coastal environments (salt marshes, etc.) you can successfully collect samples of undisturbed soil, even below water table, for thin section micro analysis! If you want i will give some references about it. Of course this doesn't work on percentages parameters, but works perfectly on particle sizes and origin determination.

best luck

J. Araújo Gomes.

Thank you Sobisch, Blanco, and Gomes for your answers.

Dear Blanco, I don't have the reference that you have mentioned, but I think it refer to grain size distribution ,I have Sun et al.2002 in sedimentary geology explain about grain size distribution actually I don't need distribution because my work is on dinoflagellate resting cyst and I want to know the type of sediments how can effect on cysts distribution?

Dear Gomes, no I have not tried this method, as you said this method doesn't work  on percentage, we may  use wentworth table and calculate the percentage is it right?? but I am not familiar with this method at all. 

what about the attached paper in my previous answer have you seen this protocol?

Hi André, certainly the method is not expensive, once the LPS works, but I think that we can not say the same about the cost instrument! Not all Structures can buy one (e.g. €60.000 or more), and I have also experienced the high cost of maintenance and replacement of parts...

Hi Gilan,

the method you plan to use depend on the sediment nature (grain size range, biogenic particles, mineral composition, grain shape etc.). There is no perfect method: you should try to find yours. I understand that this is not the answer you asked for, but that's my experience. I agree with German about Gradistat.

My best,

Kristina

Sorry to jump in on this conversation but I am also looking for a method to determine percentages of particle sizes (pebble, sand, silt) but am looking for something that can be done quickly in the field. We're just looking for rough estimates of each particle size, nothing that would involve lasers or having to look at samples in a laboratory. Any suggestions?

Hi Philip, 

in case of rough grain size estimation in the field, I suggest dry sieving using standard sieves of 1 phi interval.

Kind regards, 

Kristina