Carbon cycle
As acid rain fades, climate steers water browning
Open access · cc by · source: Europe PMC
DOC rose at 383 of 426 northern sites since 1990; early increases tracked falling sulfate, while later increases are nearly half climate-driven.
How this study connects
Role on claims
Each row is a claim on a concept or method page where this paper supports, challenges, or qualifies the statement. Roles are hand-checked — not a model guess.
Monitor networks also track fading acid deposition as an air-chemistry driver of water browning. At 426 headwater sites (1990–2016), 383 had positive DOC slopes (269 significant). Early on, ~90% of explained ΔDOC variance was sulfate (and some chloride); later, climate — mainly precipitation — accounted for 48%. Estimated DOC export rose 27% (2.3 Tg C/yr), more in Europe (+35%) than North America (+16%).
Evidence for the claim as stated.
The DOC trend paper uses the same broad idea — long monitoring records — on a different target. Sulfate decline explains most early ΔDOC; later precipitation dominates. That is air-chemistry recovery written into water, not a daily mortality or birth-weight coefficient, and site networks are biased toward well-monitored northern lakes and streams.
Evidence for the claim as stated.
Open questions
Tensions this paper is part of
From concept pages' “where studies disagree.” Disagreement means the same question; scope means different assays, populations, or outcomes.
The DOC trend paper uses the same broad idea — long monitoring records — on a different target. Sulfate decline explains most early ΔDOC; later precipitation dominates. That is air-chemistry recovery written into water, not a daily mortality or birth-weight coefficient, and site networks are biased toward well-monitored northern lakes and streams.
- Supports · Saharan dust days worsen coarse-PM mortality
Study at a glance
- Design
- Other — Theil–Sen DOC trends at headwater sites with attribution to sulfate vs climate
- N
- N=426 · 426 headwater monitoring sites (1990–2016)
- Population
- European and North American headwater catchments
- Outcome
- Dissolved organic carbon trends and drivers after air-quality improvement
Structured fields used in claim comparison tables when every cited study has a complete layer.
Inspect source passages
As acid rain fades, climate steers water browning
These passages occur verbatim in the stored paper text. They support the points listed below; they do not verify every statement in the explanation.
383 of 426 sites showed positive DOC slopes, 269 significant
Over the period 1990–2016, ΔDOC was overwhelmingly positive (; , ), with 383 of 426 sites showing positive slopes (269 significant, p < 0.05).
Climate variables accounted for 48% of late-period explained ΔDOC variance
In the late period, however, the sum effect of trends in climate variables (predominantly precipitation) accounts for 48% of this variance, i.e.
Key findings
383 sites had positive DOC slopes (269 significant). Early on, ~90% of explained ΔDOC variance was sulfate (and some chloride). Later, climate—mainly precipitation—accounted for 48%. Estimated DOC export rose 27% (2.3 Tg C/yr), more in Europe (+35%) than North America (+16%).
Methodology
Authors computed Theil–Sen DOC trends for 1990–2016 at 426 headwater sites, split early vs late periods, and used AIC model attribution among ΔSO4, ΔCl, climate, and base cations, then scaled fluxes to European and North American basins.
Limitations
Site networks are biased toward well-monitored northern lakes/streams. Flux scaling uses median trends times runoff, not full hydrologic models. Drought could still cut DOC transport while raising soil CO2.
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