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I have benthic samples that were collected with an Ekman dredge from some small ponds. The samples contain quite a bit of coarse particulate organic matter (CPOM, basically dead leaves). I would like to quantify the amount of CPOM in the samples but they were preserved with 70% ethanol in the field.

Is there any evidence that ethanol preservation alters benthic CPOM mass?

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How do you plan to separate the POM from the rest of the sample? –  Abe Nov 18 '13 at 6:26
    
We run the samples through a 1 mm sieve to separate CPOM from the remaining sample. The coarse fraction is then dried at 50 dC and ashed at 550 dC to determine LOI and % OM. –  KennyPeanuts Nov 18 '13 at 17:19
    
This sounds like something that would be straightforward to test empirically. As a bonus, any effect of EtOH on your samples (bias) could (possibly) be quantified and accounted for, especially if the effect is small. The questions you are asking will inform how best to do this. But I do suspect EtOH might dissolve some hydrophobic compounds in the coarse fraction. Maybe try evaporating it first and adding water. Not ideal, but likely more informative than throwing samples out! –  Abe Nov 18 '13 at 18:49
    
This paper implies the EtOH extractable fraction in willow leaf litter is small ~2% download.springer.com/static/pdf/61/… but this will vary by species (eg pine tar). Again, this effect can be measured on samples similar to yours. –  Abe Nov 18 '13 at 18:57
    
@Abe Thanks for the paper, I look forward to reading it. We are actually testing this now. The initial tests with fairly old OM showed no effect but we are planning some tests with fresher OM to see if that makes a difference. –  KennyPeanuts Nov 19 '13 at 2:04

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