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<li><a href="./">Practical guide on dissolved organic matter (DOM) optic</a></li>
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<li class="chapter" data-level="1" data-path="index.html"><a href="index.html"><i class="fa fa-check"></i><b>1</b> Introduction and motivations</a></li>
<li class="chapter" data-level="2" data-path="measurements.html"><a href="measurements.html"><i class="fa fa-check"></i><b>2</b> Measurements</a><ul>
<li class="chapter" data-level="2.1" data-path="dom-measurements.html"><a href="dom-measurements.html"><i class="fa fa-check"></i><b>2.1</b> DOM measurements</a></li>
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<li class="chapter" data-level="3" data-path="absorbance.html"><a href="absorbance.html"><i class="fa fa-check"></i><b>3</b> Absorbance</a><ul>
<li class="chapter" data-level="3.1" data-path="what-is-cdom.html"><a href="what-is-cdom.html"><i class="fa fa-check"></i><b>3.1</b> What is CDOM?</a></li>
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<li class="chapter" data-level="3.3" data-path="absorption-vs-absorbance.html"><a href="absorption-vs-absorbance.html"><i class="fa fa-check"></i><b>3.3</b> Absorption vs absorbance</a></li>
<li class="chapter" data-level="3.4" data-path="mathematical-formulation-of-absorption-spectra.html"><a href="mathematical-formulation-of-absorption-spectra.html"><i class="fa fa-check"></i><b>3.4</b> Mathematical formulation of absorption spectra</a></li>
<li class="chapter" data-level="3.5" data-path="sl.html"><a href="sl.html"><i class="fa fa-check"></i><b>3.5</b> Modeling CDOM absorption spectra in R</a><ul>
<li class="chapter" data-level="3.5.1" data-path="sl.html"><a href="sl.html#potential-drawbacks"><i class="fa fa-check"></i><b>3.5.1</b> Potential drawbacks</a></li>
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<li class="chapter" data-level="3.6.1" data-path="metrics.html"><a href="metrics.html#slope-ratio"><i class="fa fa-check"></i><b>3.6.1</b> Slope ratio</a></li>
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<li class="chapter" data-level="4.1" data-path="what-is-a-eem.html"><a href="what-is-a-eem.html"><i class="fa fa-check"></i><b>4.1</b> What is a EEM</a></li>
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<li class="chapter" data-level="4.3" data-path="fluorescence-of-dom-theoretical-and-mathematical-background.html"><a href="fluorescence-of-dom-theoretical-and-mathematical-background.html"><i class="fa fa-check"></i><b>4.3</b> Fluorescence of DOM: theoretical and mathematical background</a><ul>
<li class="chapter" data-level="4.3.1" data-path="fluorescence-of-dom-theoretical-and-mathematical-background.html"><a href="fluorescence-of-dom-theoretical-and-mathematical-background.html#scattering-correction"><i class="fa fa-check"></i><b>4.3.1</b> Scattering correction</a></li>
<li class="chapter" data-level="4.3.2" data-path="fluorescence-of-dom-theoretical-and-mathematical-background.html"><a href="fluorescence-of-dom-theoretical-and-mathematical-background.html#inner-filter-effect-correction"><i class="fa fa-check"></i><b>4.3.2</b> Inner-filter effect correction</a></li>
<li class="chapter" data-level="4.3.3" data-path="fluorescence-of-dom-theoretical-and-mathematical-background.html"><a href="fluorescence-of-dom-theoretical-and-mathematical-background.html#raman-calibration"><i class="fa fa-check"></i><b>4.3.3</b> Raman calibration</a></li>
<li class="chapter" data-level="4.3.4" data-path="fluorescence-of-dom-theoretical-and-mathematical-background.html"><a href="fluorescence-of-dom-theoretical-and-mathematical-background.html#metrics-1"><i class="fa fa-check"></i><b>4.3.4</b> Metrics</a></li>
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<li class="chapter" data-level="4.4" data-path="r-code-and-study-case.html"><a href="r-code-and-study-case.html"><i class="fa fa-check"></i><b>4.4</b> R code and study case</a><ul>
<li class="chapter" data-level="4.4.1" data-path="r-code-and-study-case.html"><a href="r-code-and-study-case.html#data-importation-and-plotting"><i class="fa fa-check"></i><b>4.4.1</b> Data importation and plotting</a></li>
<li class="chapter" data-level="4.4.2" data-path="r-code-and-study-case.html"><a href="r-code-and-study-case.html#blank-subtraction"><i class="fa fa-check"></i><b>4.4.2</b> Blank subtraction</a></li>
<li class="chapter" data-level="4.4.3" data-path="r-code-and-study-case.html"><a href="r-code-and-study-case.html#raman-and-rayleigh-scattering-removal"><i class="fa fa-check"></i><b>4.4.3</b> Raman and Rayleigh scattering removal</a></li>
<li class="chapter" data-level="4.4.4" data-path="r-code-and-study-case.html"><a href="r-code-and-study-case.html#inner-filter-effect-correction-1"><i class="fa fa-check"></i><b>4.4.4</b> Inner-filter effect correction</a></li>
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<li class="chapter" data-level="4.4.6" data-path="r-code-and-study-case.html"><a href="r-code-and-study-case.html#exporting-to-matlab"><i class="fa fa-check"></i><b>4.4.6</b> Exporting to MATLAB</a></li>
<li class="chapter" data-level="4.4.7" data-path="r-code-and-study-case.html"><a href="r-code-and-study-case.html#metric-extraction"><i class="fa fa-check"></i><b>4.4.7</b> Metric extraction</a></li>
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<li class="chapter" data-level="4.5" data-path="using-r-pipeline.html"><a href="using-r-pipeline.html"><i class="fa fa-check"></i><b>4.5</b> Using R pipeline</a></li>
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<li class="chapter" data-level="5" data-path="definitions.html"><a href="definitions.html"><i class="fa fa-check"></i><b>5</b> Definitions</a></li>
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<i class="fa fa-circle-o-notch fa-spin"></i><a href="./">Practical guide on dissolved organic matter (DOM) optic</a>
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<h2><span class="header-section-number">3.6</span> Metrics</h2>
<ul>
<li><span class="math inline">\(S_{300-600}\)</span> linked to DOM molecular weight <span class="citation">(Colin A. Stedmon and Nelson <a href="#ref-Stedmon2015b">2015</a>)</span>.</li>
</ul>
<div id="slope-ratio" class="section level3">
<h3><span class="header-section-number">3.6.1</span> Slope ratio</h3>
<p>Equation <a href="#eq:sr">(<strong>??</strong>)</a> shows how the slope ratio (<span class="math inline">\(S_R\)</span>) is calculated.</p>
<span class="math display">\[\begin{equation}
S_R = \frac{S_{275-295}}{S_{350-400}}
\label{eq:sr}
\end{equation}\]</span>
<blockquote>
<p>By calculating the ratio of the slope of the shorter wavelength region (275–295 nm) to that of the longer wavelength region (350–400 nm), a dimensionless parameter called “slope ratio” or <span class="math inline">\(S_R\)</span> is defined. This approach avoids the use of spectral data near the detection limit of the instruments used, and focuses on absorbance values that shift dramatically during estuarine transit and photochemical alteration of CDOM <span class="citation">(Helms et al. <a href="#ref-Helms2008">2008</a>)</span>.</p>
</blockquote>
<p>Figure <a href="metrics.html#fig:sr">3.5</a> shows in red the 275-295 and 350-400 nm spectral range.</p>
<div class="figure"><span id="fig:sr"></span>
<img src="dom_optic_files/figure-html/sr-1.svg" alt="Spectral range used to calculate the slope ratio." width="672" />
<p class="caption">
FIGURE 3.5: Spectral range used to calculate the slope ratio.
</p>
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<!-- </div> -->
<h3>References</h3>
<div id="refs" class="references">
<div id="ref-Stedmon2015b">
<p>Stedmon, Colin A., and Norman B. Nelson. 2015. “The Optical Properties of DOM in the Ocean.” In <em>Biogeochemistry of Marine Dissolved Organic Matter</em>, edited by Dennis A. Hansell and Craig A. Carlson, Academic P, 481–508. Burlington: Elsevier. doi:<a href="https://doi.org/10.1016/B978-0-12-405940-5.00010-8">10.1016/B978-0-12-405940-5.00010-8</a>.</p>
</div>
<div id="ref-Helms2008">
<p>Helms, John R., Aron Stubbins, Jason D. Ritchie, Elizabeth C. Minor, David J. Kieber, and Kenneth Mopper. 2008. “Absorption spectral slopes and slope ratios as indicators of molecular weight, source, and photobleaching of chromophoric dissolved organic matter.” <em>Limnology and Oceanography</em> 53 (3): 955–69. doi:<a href="https://doi.org/10.4319/lo.2008.53.3.0955">10.4319/lo.2008.53.3.0955</a>.</p>
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