کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
5748807 | 1619144 | 2017 | 14 صفحه PDF | دانلود رایگان |
- There has been a significant decrease in acid deposition in the Catskill Mountains from 1991 to 2014.
- There has been a significant decrease in stream sulfate concentrations in the Catskill Mountains.
- The acid-base status of these streams has improved, but the recovery has not been as large as expected.
- Soil chemistry has not improved during the last 10-20 years.
- Our results indicate that the soil weathering rate may be decreasing as acid deposition decreases.
The Catskill Mountains have been adversely impacted by decades of acid deposition, however, since the early 1990s, levels have decreased sharply as a result of decreases in emissions of sulfur dioxide and nitrogen oxides. This study examines trends in acid deposition, stream-water chemistry, and soil chemistry in the southeastern Catskill Mountains. We measured significant reductions in acid deposition and improvement in stream-water quality in 5 streams included in this study from 1992 to 2014. The largest, most significant trends were for sulfate (SO42â) concentrations (mean trend of â2.5 μeq Lâ1 yrâ1); hydrogen ion (H+) and inorganic monomeric aluminum (Alim) also decreased significantly (mean trends of â0.3 μeq Lâ1 yrâ1 for H+ and â0.1 μeq Lâ1 yrâ1 for Alim for the 3 most acidic sites). Acid neutralizing capacity (ANC) increased by a mean of 0.65 μeq Lâ1 yrâ1 for all 5 sites, which was 4 fold less than the decrease in SO42â concentrations. These upward trends in ANC were limited by coincident decreases in base cations (â1.3 μeq Lâ1 yrâ1 for calcium + magnesium). No significant trends were detected in stream-water nitrate (NO3â) concentrations despite significant decreasing trends in NO3â wet deposition. We measured no recovery in soil chemistry which we attributed to an initially low soil buffering capacity that has been further depleted by decades of acid deposition. Tightly coupled decreasing trends in stream-water silicon (Si) (â0.2 μeq Lâ1 yrâ1) and base cations suggest a decrease in the soil mineral weathering rate. We hypothesize that a decrease in the ionic strength of soil water and shallow groundwater may be the principal driver of this apparent decrease in the weathering rate. A decreasing weathering rate would help to explain the slow recovery of stream pH and ANC as well as that of soil base cations.
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Journal: Environmental Pollution - Volume 229, October 2017, Pages 607-620