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The importance of the relationship between scale and process in understanding long-term DOC dynamics
J M Clark1, S H Bottrell, C D Evans
1Civil and Environmental Engineering, Imperial College London, South Kensington, London, UK. joanna.clark@imperial.ac.uk
The Science of the Total Environment
|April 20, 2010
Summary
Dissolved organic carbon (DOC) has increased in acid-impacted waters. Regional acid deposition, not just climate or land use, likely explains differing DOC trends across Europe and North America.
Area of Science:
- Environmental Chemistry
- Hydrology
- Ecology
Background:
- Surface water concentrations of dissolved organic carbon (DOC) have risen in many acid-impacted regions of Europe and North America over the past 20 years.
- Several hypotheses, including declining atmospheric deposition, climate change, and land management, have been proposed to explain DOC increases, but consensus remains elusive.
- Research has reached a stalemate, with ongoing debate over the primary drivers of long-term DOC trends.
Purpose of the Study:
- To reconcile conflicting findings regarding the drivers of dissolved organic carbon (DOC) trends in surface waters.
- To investigate the role of regional differences in acid deposition loading in explaining discrepancies between studies on DOC dynamics.
- To clarify the influence of temporal and spatial scales on the interpretation of DOC trends.
Main Methods:
- Comparative analysis of DOC trends across different regions with varying acid deposition histories.
- Examination of the relationship between trends in pollutant deposition (sulphur, seasalt) and DOC concentrations.
- Assessment of the influence of climatic factors and catchment characteristics on DOC variability.
Main Results:
- DOC has shown significant increases in areas with pronounced declines in sulphur and/or seasalt deposition.
- Climatic factors have primarily influenced inter-annual variability and seasonality in other regions, complicating the detection of long-term monotonic DOC trends.
- Catchment characteristics mediate the sensitivity of DOC release to changes in acidity and sulphur deposition, even in areas with similar acid loading.
Conclusions:
- Regional variations in acid deposition loading are a key factor explaining discrepancies in observed DOC trends.
- The interplay of acid deposition, climate, and catchment characteristics, viewed across appropriate temporal and spatial scales, provides a more unified explanation for DOC dynamics.
- Reconciling findings requires a nuanced understanding of how these factors interact differently across various regions and scales.
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