Porcal Petr, Dillon Peter J, Molot Lewis A
Environment and Resource Studies, Trent University, 1600 West Bank Drive, Peterborough, Ontario, CanadaK9J 7B8.
Photochem Photobiol Sci. 2014 May;13(5):799-812. doi: 10.1039/c4pp00011k.
Photochemical degradation of dissolved organic matter (DOM) plays an important role in the carbon cycle. Irradiation experiments were conducted to evaluate the influence of chemical factors, specifically those expected to be altered in natural waters by atmospheric acid deposition, on photodegradation of DOM. These included pH, nitrate, iron and calcium. The experiments were carried out using stream and lake water samples with a wide range of dissolved organic carbon (DOC) concentration. Decreasing DOC concentration along with decreasing absorbance was observed during three-week exposures to natural solar radiation as well as during laboratory experiments with artificial solar radiation. The pH of the samples significantly affected degradation rates of DOM especially with elevated iron, while no influence of nitrate or calcium concentration was observed. Addition of Fe(III) did not significantly affect photodegradation and photobleaching rate constants in samples at circumneutral pH. Acid pH increased photodegradation rates. The results suggest that photodegradation rates of DOM will decrease during recovery from acidification. Hence, lower photodegradation rates may be responsible for increases in DOM observed in some regions of North America and Europe.
溶解有机物（DOM）的光化学降解在碳循环中起着重要作用。进行了辐照实验，以评估化学因素，特别是那些预计会因大气酸沉降而在天然水体中发生变化的因素，对DOM光降解的影响。这些因素包括pH值、硝酸盐、铁和钙。实验使用了具有广泛溶解有机碳（DOC）浓度的溪水和湖水样本。在为期三周的自然太阳辐射暴露期间以及人工太阳辐射的实验室实验中，观察到DOC浓度随吸光度降低而降低。样品的pH值显著影响DOM的降解速率，尤其是在铁含量升高时，而未观察到硝酸盐或钙浓度的影响。在接近中性pH值的样品中添加Fe(III)对光降解和光漂白速率常数没有显著影响。酸性pH值会提高光降解速率。结果表明，在从酸化状态恢复的过程中，DOM的光降解速率将会降低。因此，较低的光降解速率可能是北美和欧洲一些地区观察到的DOM增加的原因。
