Origin and migration of dissolved organic carbon fractions in a clay‐rich aquitard: <sup>14</sup>C and δ<sup>13</sup>C evidence
Bibliographic record
Abstract
The origin and long‐term transport of dissolved organic carbon (DOC) and its high molecular weight (HMW) and low molecular weight (LMW) fractions were investigated in a clay‐rich till aquitard system. DOC concentrations decreased systematically with depth from 168 mg L −1 in the surficial fractured zone (1.2 m) to minimum values of 12–16 mg L −1 from 15 to 43 m depth in the nonfractured aquitard. The HMW and LMW DOC fractions and their corresponding δ 13 C values also decreased systematically with depth. Numerical transport simulations of the downward migration of DOC from the soil zone into the aquitard closely approximated field‐measured values and show transport of DOC was controlled by diffusive mixing. The depth trends for HMW and LMW DOC fractions and δ 13 C support hypothesized transport via diffusion, as well as earlier findings that microbial respiration in this nonfractured aquitard was negligible over the time period studied. The 14 C content of the HMW DOC fraction decreased systematically with depth from 87 percent modern carbon (pmC) at 1.2 m to 13–15 pmC from 15 to 43 m depth. A simple model accounting for diffusive mixing and radioactive decay described the 14 C profile in the aquitard. Radiocarbon measurements, transport modeling, and δ 13 C data suggest DOC and its fractions were derived from two distinct end‐members: soil organic carbon formed since the Holocene (∼10 ka B.P.) and DOC in connate pore water (∼15 ka B.P.).
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".