Table 1.
LMW DOM coverage by HILIC and RP in positive- and negative-ionization modes at each level of data filtering, expressed as the number of features detected across all nine soil water extracts.
| LC-MS Condition | All Features | High-Quality Features | Unique HQFsa | Abundant HQFsb | Varied significantly with depthc | Significant HQFs with MS1 match (+/−5 ppm) |
|---|---|---|---|---|---|---|
| HILIC (+) | 1455 | 438 | 206 | 247 | 164 | 35 |
| HILIC (−) | 8343 | 1705 | 1132 | 257 | 79 | 14 |
| RP (+) | 1828 | 1462 | 700 | 202 | 12 | 8 |
| RP (−) | 1298 | 85 | 47 | 10 | 2 | 2 |
aUnique high-quality features observed by only one LC-MS condition, determined by examining the overlap of the neutral precursor masses (+/−0.001 Da). bAbundant features were observed in at least 2 of 3 extraction replicates at each depth above an intensity threshold of 1.0E5 ion counts. cAbundant features with differential abundances that varied significantly (log2 fold change >1.5, p-value < 0.05) between soil core depths.