Calcium Losses from a Forested Catchment in South-Central Ontario, Canada
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- 作者：Shaun A. Watmough and Peter J. Dillon
- 刊名：Environmental Science & Technology
- 出版年：2003
- 出版时间：July 15, 2003
- 年：2003
- 卷：37
- 期：14
- 页码：3085 - 3089
- 全文大小：94K
- 年卷期：v.37,no.14(July 15, 2003)
- ISSN：1520-5851
文摘
Mass balance studies at a number of calibrated watershedsin eastern North America suggest that large losses ofCa from soil have occurred due to acid deposition. However,there is considerable controversy over whether losseshave occurred from the exchangeable pool or whether thereare other sources of Ca that have not been considered.Mass balance calculations at a small, calibrated catchment(PC1) in south-central Ontario also indicate that largelosses of Ca have occurred over the past 2 decades. Ifthe exchangeable Ca pool has declined by approximately40% between 1983/1984 and 1998/1999 but the exchangeableMg pool has remained relatively stable, these changes shouldbe evident in streamwater chemistry. The slope of thebuffer curve relating Ca to 
acid anions (FCa) decreasedsignificantly over the study period. We estimate thatFCa decreased by 12-24% between 1983 and 1999, althoughthe level of decrease is affected by changes in hydrology.During the same period, there was no significant changein FMg, and the annual volume-weighted Ca:Mg (equiv/equiv)ratio in streamwater decreased from ~2.8 to ~2.1.Measured changes in streamwater chemistry translateinto Ca losses from the exchangeable pool of approximately250-570 mequiv/m2 over the study period, which issimilar to estimated losses based on soil measurements(~425 mequiv/m2) and mass balance calculations (~380-430 mequiv/m2). The magnitude of Ca loss cannot beexplained by decreases in Ca deposition or decreased Caweathering. Large Ca losses from the soil exchangeablepool have serious implications for future forest health andthe recovery of streamwater from acid deposition.
acid anions (FCa) decreasedsignificantly over the study period. We estimate thatFCa decreased by 12-24% between 1983 and 1999, althoughthe level of decrease is affected by changes in hydrology.During the same period, there was no significant changein FMg, and the annual volume-weighted Ca:Mg (equiv/equiv)ratio in streamwater decreased from ~2.8 to ~2.1.Measured changes in streamwater chemistry translateinto Ca losses from the exchangeable pool of approximately250-570 mequiv/m2 over the study period, which issimilar to estimated losses based on soil measurements(~425 mequiv/m2) and mass balance calculations (~380-430 mequiv/m2). The magnitude of Ca loss cannot beexplained by decreases in Ca deposition or decreased Caweathering. Large Ca losses from the soil exchangeablepool have serious implications for future forest health andthe recovery of streamwater from acid deposition.