Spatial pattern of K<sub>d</sub>(PAR) and its relationship with light absorption of optically active components in inland waters across China

Abstract

<p><strong>Abstract.</strong> The spatial distribution of the attenuation of photosynthetic active radiation (K<sub>d</sub>(PAR)) was routinely estimated in China lakes and reservoirs. Higher mean value of K<sub>d</sub>(PAR) was observed in Northeastern plain and mountainous region (NER). A linear model is used to predict K<sub>d</sub>(PAR), as a function of light absorption coefficient of pigment particulates (a<sub>phy</sub>), colored dissolved organic matters (a<sub>CDOM</sub>), and inorganic particulate matters (a<sub>NAP</sub>): K<sub>d</sub>(PAR)<span class="thinspace"></span>=<span class="thinspace"></span>0.41<span class="thinspace"></span>+<span class="thinspace"></span>0.57<span class="thinspace"></span>×<span class="thinspace"></span>a<sub>CDOM</sub><span class="thinspace"></span>+<span class="thinspace"></span>0.96<span class="thinspace"></span>×<span class="thinspace"></span>a<sub>NAP</sub><span class="thinspace"></span>+<span class="thinspace"></span>0.57<span class="thinspace"></span>×<span class="thinspace"></span>a<sub>phy</sub> (R<sup>2</sup><span class="thinspace"></span>=<span class="thinspace"></span>0.87, n<span class="thinspace"></span>=<span class="thinspace"></span>741, <i>p</i><span class="thinspace"></span><<span class="thinspace"></span>0.001). Spatial K<sub>d</sub>(PAR) was relatively dependent on the inorganic particulate matters (average relative contribution of 57.95<span class="thinspace"></span>%). When only consider the contribution of absorption of a<sub>OACs</sub> to K<sub>d</sub>(PAR), the results found that the a<sub>OACs</sub> could explain 70<span class="thinspace"></span>%–87<span class="thinspace"></span>% of K<sub>d</sub>(PAR) variations. In the lakes with low TSM concentration and non-eutrophic lakes with high TSM, a<sub>CDOM</sub> was the most powerful predicting factor on K<sub>d</sub>(PAR). In eutrophic lakes with high TSM, a<sub>NAP</sub> had the most significant impact on K<sub>d</sub>(PAR). This study allowed K<sub>d</sub>(PAR) to be predicted from a<sub>OACs</sub> values in the inland waters. Besides, results of this study are suggesting that new studies on the variability of K<sub>d</sub>(PAR) in inland waters must consider the hydrodynamic conditions, trophic status and the distribution of optically active components within the water column.</p>