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Water 2014, 6(5), 1360-1418; doi:10.3390/w6051360
Review

Long-term Trends of Organic Carbon Concentrations in Freshwaters: Strengths and Weaknesses of Existing Evidence

1,2,*  and 3
Received: 26 March 2014; in revised form: 25 April 2014 / Accepted: 4 May 2014 / Published: 20 May 2014
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Abstract: Many articles published in the last few years start with the assumption that the past decades have seen an increase in dissolved organic carbon (DOC) concentrations in the rivers and lakes of the Northern Hemisphere. This study analyses whether the existing evidence supports this claim. With this aim, we have collected published studies where long series of organic carbon concentrations (i.e., longer than 10 years) were analyzed for existing trends and have carefully evaluated the 63 articles found. Information has been collated in a comprehensive and comparable way, allowing readers to easily access it. The two main aspects considered in our analysis have been the analytical methods used and the data treatment methods applied. Both are sensitive issues because, on the one hand, the difficulties associated with correctly determining organic carbon concentrations in surface waters are well known, while, on the other, dealing with real environmental data (i.e., lack of normality, censoring, missing values, etc.) is an extremely intricate matter. Other issues such as data reporting and the geographical location of the systems studied are also discussed. In conclusion, it is clear that organic carbon concentrations have increased in some surface waters in the Northern Hemisphere since the 1990s. However, due to a lack of data in many parts of the world, it is not known whether this phenomenon is general and, more importantly, in the areas for which such data do exist, the reporting and methodological problems in the published studies prevent any conclusion on the existence of a general temporal behavior of organic carbon from being drawn.
Keywords: organic carbon; DOC; dissolved organic carbon; temporal trends; time-series analysis; freshwaters; lakes; rivers organic carbon; DOC; dissolved organic carbon; temporal trends; time-series analysis; freshwaters; lakes; rivers
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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MDPI and ACS Style

Filella, M.; Rodríguez-Murillo, J.C. Long-term Trends of Organic Carbon Concentrations in Freshwaters: Strengths and Weaknesses of Existing Evidence. Water 2014, 6, 1360-1418.

AMA Style

Filella M, Rodríguez-Murillo JC. Long-term Trends of Organic Carbon Concentrations in Freshwaters: Strengths and Weaknesses of Existing Evidence. Water. 2014; 6(5):1360-1418.

Chicago/Turabian Style

Filella, Montserrat; Rodríguez-Murillo, Juan C. 2014. "Long-term Trends of Organic Carbon Concentrations in Freshwaters: Strengths and Weaknesses of Existing Evidence." Water 6, no. 5: 1360-1418.


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