a(λ) = a(λref)e-S(λ-λref)
Where a(λ) = Absorbance coefficient at a specific wavelength per meter for CDOM, λref = Reference wavelength in nm and S = the spectral slope which is an indicator of the relative steepness of the spectrum.
Please describe what is λref ? and what is the value?
Dear Sristika,
Good morning! Regarding your question, you need to consider that λref = Reference wavelength in nm (see Twardoski, 2004), means that if you want to calculate (S275-295) then the value for λref = 275nm, and the a(λref) = is the absorbance at this wavelength.
Maybe you want to check this two Papers: (Helms, 2008) and Twardowski (2004) pdfs (attached).
All the best,
Mario
Dear Sristika,
Mario Miranda Montenegro 's answer is helpful, and these two papers are very important for the spectral slope calculation. In Twardowski et al. (2004) paper, the authors found that the variability of the spectral slope values across different studies was due to the different wavelength ranges applied. So a fixed wavelength range (e.g. 275-295 developed by Helms et al. (2008)) could be helpful for comparison among different studies. For S275-295 calculation, you can use a linear fitting of log-transformed absorption coefficient (Helms et al. 2008), so there is no need to use a reference wavelength. We also discussed about the spectral slopes derived from different methods in our review paper, and you can also check it here: Utilization of UV-Vis spectroscopy and related data analyses for dissolved organic matter (DOM) studies: A review Article Utilization of UV-Vis spectroscopy and related data analyses...
.Best Regards
Penghui
Hello! I recommend this program for an easy CDOM calculation (include s275-295, s350-400, Sr, etc.)
ASfit home page: https://sites.google.com/site/daromasoft/home/spectral-slope
Best regards!
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