New Insights into the Source of Decadal Increases of Dissolved Organic Matter in Acid-Sensitive Lakes of the Northeastern United States

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• 作者：Michael D. SanClements ; Gretchen P. Oelsner ; Diane M. McKnight ; John L. Stoddard ; Sarah J. Nelson
• 刊名：Environmental Science & Technology (ES&T)
• 出版年：2012
• 出版时间：March 20, 2012
• 年：2012
• 卷：46
• 期：6
• 页码：3212-3219
• 全文大小：425K
• 年卷期：v.46,no.6(March 20, 2012)
• ISSN：1520-5851

文摘

The last several decades have seen decreases in SO₄^{2鈥?/sup> deposition across the northeastern United States. As a result, SO₄2鈥?/sup> concentrations in lakes and streams have also decreased and many surface water bodies have become less acidic. During the same time period, there has been a concurrent increase in dissolved organic carbon (DOC) concentrations in many lakes and streams. We used fluorescence spectroscopy to characterize the dissolved organic matter (DOM) quality of archived samples from nine acid-sensitive lakes in Maine collected between 1993 and 2009, and determined that increased DOM contributions to lakes were primarily derived from litter and soil. All five lakes with increasing DOC trends demonstrated significant decreasing (i.e., more terrestrial) trends in fluorescence index (FI) and significant positive correlations between SO₄2鈥?/sup> and FI. This study used the chemical signature of terrestrial DOM to support the hypothesis that increased DOC concentrations in lakes and streams are driven by declining acid deposition and increased solubility of soil organic matter across a large area of the landscape.}