Long-term trends in dissolved organic carbon concentration: a cautionary note

被引：0
作者：
M. Catherine Eimers
Shaun A. Watmough
James M. Buttle
机构：
[1] Trent University,Department of Geography
[2] Trent University,Environmental and Resource Sciences Program
来源：
Biogeochemistry | 2008年 / 87卷
关键词：
Dissolved organic carbon; Hydrology; Streams; Wetlands; Long-term trends;
D O I：
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中图分类号：
学科分类号：
摘要：
Dissolved organic carbon (DOC) plays an important role in surface water chemistry and ecology and trends in DOC concentration have been also associated with shifts in terrestrial carbon pools. Numerous studies have reported long-term trends in DOC concentration; however, some studies consider changes in average measured DOC whereas other compute discharge weighted concentrations. Because of differences in reporting methods and variable record lengths it is difficult to compare results among studies and make regional generalizations. Furthermore, changes in stream discharge may impact long-term trends in DOC concentration and the potentially subtle effect of shifts in stream flow may be missed if only measured DOC concentrations are considered. In this study we compare trends in volume-weighted vs. average measured DOC concentration between 1980 and 2001 at seven headwater streams in south-central Ontario, Canada that vary in wetland coverage and DOC (22-year mean vol. wt.) from 3.4 to 10.6 mg l−1. On average, annual measured DOC concentrations were 13–34% higher than volume-weighted values, but differences of up to 290% occurred in certain years. Estimates of DOC flux were correspondingly higher using measured concentration values. Both measured and volume-weighted DOC concentrations increased significantly between 1980 and 2001, but slopes were larger in measured data (0.04–0.35 mg l−1 year−1 compared with 0.05–0.15 mg l−1 year−1) and proportional increases at the most wetland-influenced sites ranged from 32 to 43% in volume-weighted DOC and from 52 to 75% in measured DOC. In contrast, DOC flux did not change with time when estimated using either method, because of the predominant influence of stream flow on DOC export. Our results indicate that changes in stream flow have an important impact on trends in DOC concentration, and extrapolation of trend results from one region to another should be made cautiously and consider methodological and reporting differences among sites.
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页码：71 / 81
页数：10
相关论文
共 150 条
[31]  
Chapman PJ(1998)Browning the waters Clim Change 40 167-28
[32]  
Clark JM(1997)Precambrian Shield wetlands: hydrologic control of the sources and export of dissolved organic matter Biogeochemistry 36 9-337
[33]  
Monteith DT(2001)Climate-induced changes in the dissolved organic carbon budgets of boreal lakes Hydrol Earth Syst Sci 5 327-176
[34]  
Cresser MS(2005)Recovery from acidification of lakes in Finland, Norway and Sweden Environ Pollut 137 165-862
[35]  
Findlay SEG(2002)Regional scale evidence for improvements in surface water chemistry: 1990–2001 Nature 415 861-380
[36]  
Forsius M(2005)Climate change (communication arising): terrestrial export of organic carbon Rev Sci Eau 18 353-65
[37]  
Vuorenmaa J(2006)Seasonal variations of the transport of dissolved organic carbon in the intermittent stream draining the Hermine headwater catchment on the Canadian Shield Sci Total Environ 365 47-139
[38]  
Mannio J(2005)Increasing trends of total organic carbon concentrations in small forest lakes in Finland from 1987 to 2003 J Hydrol 300 126-178
[39]  
Syri S(2003)Predicting the future DOC flux from upland peat catchments Biogeochemistry 64 165-402
[40]  
Freeman C(2004)Long terms records of riverine carbon flux Biogeochemistry 70 369-undefined
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